NON-INVASIVE DIAGNOSTIC METHOD FOR INFLAMMATORY DERMATOSES

Abstract

The present invention relates to non-invasive methods for diagnosing inflammatory dermatoses and their application to the identification of cosmetic and dermatological products.

Description

Title of the invention: NON-INVASIVE DIAGNOSTIC METHOD FOR INFLAMMATORY DERMATOSES STATE OF THE ART

[0001] The skin constitutes a barrier against external aggressions, particularly chemical, mechanical or infectious ones. The skin is made up of three main parts: a superficial part, the epidermis; an inner part, the dermis; and a deeper layer, the hypodermis, which interact with each other.

[0002] The natural human epidermis is composed mainly of three types of cells: keratinocytes, which are by far the most numerous, melanocytes, and Langerhans cells. Each of these cell types contributes, through its specific functions, to the essential role played by the skin in the body, particularly its role in protecting the body from external aggressions.

[0003] The dermis provides the epidermis with a solid support. It is also its nourishing element. It is mainly composed of fibroblasts within an extracellular matrix made up primarily of a substance, called the ground substance, which also contains collagen and elastin. These components are synthesized by the fibroblasts. Leukocytes, mast cells, and tissue macrophages are also found there. Finally, the dermis is traversed by blood vessels and nerve fibers, including free sensory fibers or those connected to receptors.

[0004] Finally, the hypodermis is the deepest and thickest layer of the skin. It is continuous with the dermis, with no real separation between the two tissues. The hypodermis acts as a shock absorber, providing mechanical protection for the underlying structures. This fatty layer also helps insulate the body from temperature variations. While the dermis can be considered a water reservoir, the fats stored within the adipocytes of the hypodermis constitute an energy reserve.

[0005] A dysfunction of the structural organization of epidermal cells, or a defect in the chemical barrier function of the epidermis, can result in a cutaneous inflammatory state.

[0006] Inflammatory dermatoses are skin and mucous membrane conditions, often painful, characterized by unsightly manifestations such as redness and scaling patches. Several pathologies are grouped under the term inflammatory dermatoses. Examples include Non-exhaustive list: atopic dermatitis, eczema, psoriasis, rosacea, lichen planus, prurigo, seborrheic dermatitis or acne.

[0007] These skin conditions, even though well-known, remain complex. Indeed, they can present in more or less severe forms, and they can be continuous or, conversely, progress in flare-ups interspersed with spontaneous remissions. The choice of a topical treatment is therefore not as straightforward as one might think. For maximum effectiveness, it must be perfectly adapted to the individual and even to the precise stage of the condition.

[0008] To achieve this, a precise study of the structural organization of the patients' skin would be an advantage in helping to choose an appropriate treatment.

[0009] Today, the evaluation of cosmetic and pharmacological agents can be carried out, in particular, on in vitro reconstructed human skin models. These models can even contain a differentiated epidermal barrier and reflect as closely as possible the morphological conditions of human skin in vivo. However, even these sophisticated models remain models and do not reflect the actual conditions of our skin.

[0010] Other technologies exist for analyzing skin structures and their molecular composition in detail. Among the tools that allow the study of skin composition are spectroscopic techniques, and in particular mass spectrometry.

[0011] Mass spectrometry has been a recognized technology for many years due to its sensitivity, speed of analysis, reproducibility, and versatility. Furthermore, because it allows compounds to be separated based on their mass-to-charge ratio (and therefore indirectly their molecular weight), it is particularly well-suited for the analysis of complex samples. Finally, it offers the advantage, through the study of gas-phase fragmentation (MS / MS mode), of enabling the identification of compounds and providing information on their structure. However, conventional mass spectrometry is adapted and has been developed for the analysis of samples after extraction and therefore does not allow for direct analysis in humans.Over the past 20 years, the development of ambient ionization mass spectrometry (AIMS) has contributed to the rise of in situ and real-time analysis of raw biological systems without sampling or extraction and with extremely limited sample preparation. These technical advances have brought mass spectrometry closer to in situ analysis.

[0012] Alternatively, skin biopsies obtained by punching can be used for extraction or fixed in formalin and paraffin so that they can be stained and analyzed more selectively using microdissection by Laser capture. Analysis can also be performed on skin layers obtained by suction bubbles or on scales collected with adhesive tape, where cells can be purified by flow cytometry. However, while most sampling methods are useful for routine analyses, they do not allow for in vivo measurements.

[0013] Furthermore, conventional methods for analyzing metabolites, including skin lipids, require preparation steps such as sample solubilization and the use of chromatographic methods. However, some skin lipids are difficult to solubilize. Moreover, preparation methods are optimized to measure a specific type of molecule, in terms of molecule size and hydrophobicity, which therefore does not allow for the detection of all types of lipids / metabolites in a single measurement.

[0014] Consequently, there remains a need for new tools that would allow for real-time knowledge of the structural organization of the skin of patients suffering from inflammatory dermatoses in order to offer treatments perfectly adapted to the stage of their skin conditions. Similarly, the effectiveness of a topical treatment could thus be easily assessed by a dermatologist, who could then, based on the results, decide to continue the treatment, adapt it, or even stop it. DETAILED DESCRIPTION OF THE INVENTION

[0015] The present description thus relates to a new method for detecting and measuring, in real time and simultaneously, very different chemical molecules in the skin. This technique is particularly advantageous because it allows for the identification and measurement, in vivo and in real time, of the molecules or classes of molecules that are modulated in inflammatory dermatoses compared to normal skin, in a safe, rapid, and reproducible manner. Indeed, the method described here is a microinvasive method that makes it possible to identify defects in essential components of the barrier function while detecting biological activations, such as inflammatory signals, in inflammatory dermatoses and comparing them to healthy skin.Such a molecular signature is particularly useful because it is specific to an inflammatory dermatosis and could thus, for example, allow a doctor to make a diagnosis.

[0016] In a first aspect, the present description relates to a method for identifying a molecular signature in a subject suffering from inflammatory dermatosis, said method comprising a step of analyzing the biological markers of a skin sample from the subject by in-vivo and real-time mass spectrometry.

[0017] The analysis of biological markers is preferably carried out using a technology chosen from among Raman, IR, fluorescence, or other spectroscopies. Mass spectrometry. Preferably, biological markers are analyzed by mass spectrometry.

[0018] By "mass spectrometry," we mean here a technique based on measuring the mass-to-charge ratio (m / z) of ions created in the gas phase, which allows the molecular weight of the species in an organic sample, for example, a skin sample, to be deduced. In a first step, the different species in the sample transition from their initial state as ions in the gas phase via the ion-generating source of the mass spectrometer. In a negative ionic mode (also called "negative mode"), the different species in the sample are negatively charged, mainly by deprotonation, while they are positively charged, mainly by protonation, in a positive ionic mode (also called "positive mode"); the species formed being dependent on the type of source used. The ions formed are then separated in the mass analyzer and subsequently detected and measured according to the m / z ratio.

[0019] Mass spectrometry is commonly implemented using mass spectrometers. A mass spectrometer conventionally comprises, in the following order: • an ion source or ionization chamber, • an ion transfer or focusing system, and • one or more analyzers that separate ions according to their mass and of their responsibility.

[0020] It also includes a detector that detects ions exiting the analyzer.

[0021] By way of non-limiting agreement, examples of focusing and / or ion transfer systems may include a transfer capillary, a skimmer, a focusing lens (such as, for example, a so-called Einzel unipotential lens), a multipolar field transfer system, an ion funnel, an electrostatic lens.

[0022] The mass spectrometer may also include elements designed to improve its performance, such as an ion mobility system. For example, some spectrometers are also equipped with a mobility cell that adds a separation dimension, very useful for complex mixtures, by allowing separation based on the conformation of molecules in the gas phase via the measurement of their cross-section.

[0023] The mass analyzer used may be of any type, whether simple (e.g., Single Magnetic Sector (B) or Dual Focusing (BE, EB), Quadrupole (Q), Ion Trap (Tl), Time of Flight (TOF), Cyclotronic Ion Resonance (ICR), Orbitrape), combined (e.g., Triple Quadrupole) or hybrid (e.g., Q-Orbitrape, Q-TOF).

[0024] Alternatively, the mass analyzer used may be another ion separation system (e.g., ionic mobility).

[0025] The mass analyzer can be sequentially coupled to one or more analyzers. Some spectrometers, in order to allow structural studies in addition to molecular weight determination, are thus equipped with several analyzers to enable the selection of the precursor ion, its fragmentation, and then the measurement of the m / z ratios of the generated non-neutral fragments. In particular, tandem mass spectrometry (MS / MS) combines two analyzers sequentially. Tandem mass spectrometry (MS / MS) differs from standard MS by the fragmentation of ions to allow for better identification. The ions separated during simple MS are selected in a first analyzer and fragmented. The fragments are analyzed in a second analyzer (MS fragments). The identification obtained is more precise and more accurate.

[0026] The most commonly used ion production sources because they are compatible in this field are, for example, electron ionization (El), chemical ionization (CI) and chemical desorption-ionization (DCI), fast atom bombardment (FAB), metastable atom bombardment (MAB) or ion bombardment (SIMS, LSIMS), inductively coupled plasma (ICP), and in particular inductively coupled laser ablation (LA-ICP), atmospheric pressure chemical ionization (APCI) and atmospheric pressure photoionization (APPI), electron spraying or electrospray (ESI), electrospray desorption-ionization (DESI), matrix-assisted laser ionization-desorption (MALDI), surface-activated laser ionization-desorption (SELDI) or silicon-activated laser ionization-desorption (DIOS), ionization-desorption by interaction with metastable species (DART), etc. It is also possible to use water-assisted laser desorption / ionization (WALDI), which is the basis of SpiderMass technology.

[0027] The method described herein can be implemented using any of these mass spectrometry techniques. However, it is particularly advantageous to use the SpiderMass technique within the framework of the methods described in this description.

[0028] According to this preferred embodiment, the method for identifying a molecular signature in a subject with inflammatory dermatosis described herein includes a step of analyzing the biological markers of a skin sample by SpiderMass technology.

[0029] SpiderMass is a recently developed, non-destructive ambient ionization technique for in vivo analysis using an infrared-emitting laser probe to scan a target tissue and connected to a mass spectrometer. The SpiderMass technique thus comprises, in a first step, a laser desorption / ionization process that allows sampling of biological material (e.g., aa skin sample) to be analyzed. The laser beam excites the water molecules present in the biological material, leading to the ejection of gaseous particles (charged or uncharged). The laser ablates only a few microns thick of the stratum corneum per shot. The ablated material is transmitted in real time to the mass spectrometer via a transfer line, which is a tube with a diameter of a few millimeters at most and can be several meters long, allowing the spectrometer to be located away from the laser operation. The transfer is achieved by creating a vacuum between the inside and outside of the spectrometer through simple suction.The aerosol transferred to the spectrometer via the tube allows for real-time analysis and enables the collection of molecular profiles (signals from the analysis of biological material corresponding to biomolecules such as organic compounds, amino acids, metabolites, lipids, peptides, etc.) characteristic of the analyzed area.

[0030] Advantageously, these profiles are compared to a database of molecular profiles obtained by the same SpiderMass technique.

[0031] SpiderMass is notably implemented using a device comprising 4 parts: 1. an infrared laser (2940 nm) used via an optical fiber for in vivo microsampling of matter and potentially the production of ions; 2. a transfer line which allows the ablated particles to be aspirated, brought to the instrument and introduced into it; 3. A mass spectrometer capable of analyzing molecules in real time and generating characteristic molecular profiles, which may include a tandem mass spectrometer (MS / MS); and 4. a tool for processing generated data based on databases and statistical analysis tools.

[0032] La technique SpiderMass et le dispositif associé sont bien connus dans l’art. Ils sont décrits dans, par exemple, la demande internationale WO 2016 / 046748, Fatou et al. SPIDERMASS : A Novel in vivo Real-Thne Mass Spectrometry Based Instrument of Low Invasiveness for Guided Surgery Applications. 2016. Sci Rep. 6:25919; Fatou et al. Remote Atmospheric Pressure Infrared Matrix-Assisted Laser Desorption-lonization Mass Spectrometry of Proteins. Mol Cell Proteomics. 2018. 17(8):1637-1649; Saudemont et al. Real-Thne Molecular Diagnosis of Tumors Using Water-Assisted Laser Desorption / Ionization Mass Spectrometry Technology. Cancer Cell. 2018. 34(5):840-851.e4; Fatou et al. Real time human micro-organisms biotyping using SpiderMass technology based on WALDI processes. Eur. J. Biotech 2019. 3(2), 97-104; Cameron et al. Utilisation of Ambient Laser Desorption Ionisation Mass Spectrometry (ALDLMS) Improves Lipid- Based Microbial Species Level Identification. SciRep. 2019. 9(l):3006; Ogrinc et al. SpiderMass for in-vivo and real-time analysis. Nat Protoc. 2019. 14(11):3162-3182; Ogrinc et al. Robot-Assisted SpiderMass for In Vivo Real-Time Topography Mass Spectrometry Imaging. Anal Chem. 2021. 93(43):14383-14391; Ogrinc et al. Direct Water-Assisted Laser Desorption / Ionization Mass Spectrometry Lipidomic Analysis and Classification of Formalin-Fixed Paraffin-Embedded Sarcoma Tissues without Dewaxing. Clin Chem. 2021. 67(11): 1513-1523; and Ogrinc et al. Cancer Surgery 2.0: Guidance by Real-Time Molecular Technologies. 27(6):602-615.

[0033] In a preferred embodiment, the present description relates to a method for identifying a molecular signature in a subject with inflammatory dermatosis, said method comprising a step of analyzing the biological markers of a skin sample by the SpiderMass technique.

[0034] The term "inflammatory dermatosis" here refers to an inflammatory condition or pathology of the skin. An inflammatory dermatosis is an inflammation of the superficial layers of the skin that is commonly (but not always) characterized by itching, blisters, erythema (redness), edema, and often oozing, crusting, and scaling. Several pathologies are grouped under the term inflammatory dermatoses. Examples include psoriasis, atopic dermatitis, eczema, acne, rosacea, lichen planus, prurigo, and seborrheic dermatitis. These dermatoses often result from inflammatory processes and / or immune disorders.

[0035] Preferably, inflammatory dermatoses are selected from psoriasis, atopic dermatitis, eczema, acne, rosacea, lichen planus, prurigo, and seborrheic dermatitis. Preferably, an inflammatory dermatosis for the method described herein is seborrheic dermatitis.

[0036] The term “molecular signature” or “molecular profile” here refers to a group of biological markers whose expression is specific to the sample analyzed, for example, a skin sample from an inflammatory dermatosis. The term “biological marker” in the context of this application means a characteristic that is objectively measured and evaluated as an indicator of normal biological processes, pathogenic processes, or pharmacological responses to a therapeutic intervention. A biological marker thus encompasses a wide range of substances, activities, and parameters. For example, a biological marker may be a substance whose detection indicates a particular pathological state or, conversely, a substance whose detection indicates a specific physiological state.A biological marker as understood here can include any type of cellular molecule, such as metabolites, proteins, lipids, nucleic acids, etc.

[0037] In a preferred embodiment, a molecular marker may in particular be a metabolite, such as, for example, a dipeptide, an amino acid and analogues, an imidazole, an indole, an amine, a carbonyl, etc. Preferably, the metabolites include urocanant, andrenochrome o-semiquinone, indolactic acid, 2-hydroxybenzyldehyde, pyroglutamic acid, glutamic acid, histidine, citrulline, the dipeptide His-Pro and histamine.

[0038] In another preferred embodiment, a molecular marker may in particular be a lipid selected from free fatty acids and their conjugates; prostaglandins; fatty aldehydes; fatty esters (esters of fatty acids branched by a hydroxylated fatty acid); cerides; squalene; glycerolipids; sphingolipids, oxylipins and cholesterol and / or cholesterol esters.

[0039] Preferably, the molecular marker is chosen from free fatty acids, fatty aldehydes, fatty esters, cerides, glycerolipids and / or oxylipins.

[0040] Preferably, the free fatty acids comprise saturated fatty acids and / or unsaturated fatty acids. Preferably, the saturated fatty acids comprise C8:0, C12:0, C14:0, C15:0, C16:0, C17:0, C18:0, C24:0 and / or C26:0. Preferably, unsaturated fatty acids include C6:1, C8:1, C9:1, C10:1, C10:2, C11:1, C11:2, C11:3, C12:1, C12:2, C13:1, C13:2, C14:3, C17:2, C18:1, C18:2, C19:1, C19:2, C20:1, C20:2, C20:3, C20:4, C22:1, C26:1 and C30:1.

[0041] Preferably, the fatty aldehydes comprise C23:0, C24:0, C26:0, C26:1 and C28:0.

[0042] Preferably, the fatty esters comprise Cl8:2 / 30-0-C30:0, C18:2 / 32-O-C30:0 and C18:2 / 30-0-30:0.

[0043] Preferably, the cerides comprise Cl:0 / C7:0, C2:0 / C12:0 and C16:0 / C21:0.

[0044] Preferably, the glycerolipids comprise monoacylglycerol (MG) MG 18:1; MG 24 :0, le diacylglycérol (DG) 18 :1 / 18 :1, DG 0-26 :0, DG 30 :1, DG 30 :0, DG 15 :0 / 16 :0, DG 16 :0 / 16 :1, DG 16 :1 / 17 :0, le triglycéride (TG) 16 :0 / 18 :1 / 18 :1, TG 18 :1 / 18 :1 / 18 :2, TG 18 :1 / 18 :1 / 18 :1, TG 16 :1 / 18 :1 / 20 :1 et TG 18 :0 / 18 :1 / 18 :1.

[0045] Preferably, the sphingolipids comprise sphingosine, sphingoid base 20:0;O3, sphingoid base 22:0;O3, sphingoid base 20:1;O3, sphingoid base 25:0;O3, sphingoid base 24:0;O2, sphingoid base 24:1;O2, sphingoid base 25:0;O2, sphingoid base 25:1;O2, sphingoid base 26:0;O2, sphingoid base 26:1;O2, sphingoid base 27:0;O2, sphingoid base 27:1;O2, sphingoid base 28:0;O2, phytosphingosine and ceramides. More preferably, ceramides include Cer 38:1;O3, Cer 17:0;O3 / 24:0; (2OH), Cer 18:0;O3 / 25:0;O, Cer 17:0;O3 / 26:0;O, Cer 21:0;O3 / 24:0;O, Cer 22:0;O3 / 25:0;O, Cer 24:0;O2 / 24:0, Cer 23:0;O2 / 25:0, Cer 24:0;O2 / 26:0, Cer 26:0;O2 / 24:0, Cer 24:0;O2 / 25:0, Cer 22:1;O3 / 28:0, Cer 20:1;O3 / 30:0, Cer 20:1;O3 / 28:0, Cer 20:1;O3 / 27:0, Cer 21:1; 03 / 26:0, Cer 21:1;O3 / 28:0, Cer 18:1;O3 / 27:0, Cer (20:1; 03 / 25:0, Cer 20:1;O3 / 26:0, Cer 18:1; 03 / 28:0, Cer 18:1;O3 / 26:0, Cer 17:0;O3 / 26:0, Cer 18:0;O3 / 24:0, Cer 20:0;O3 / 25:0, Cer 18:0; :0, Cer 20:0; 03 / 24:0, Cer 22:0;O3 / 26:0, Cer 22:0;O3 / 27:0, Cer 16:0;O3 / 24:0, Cer 18:0; 03 / 22:0, Cer 22:0;O3 / 28:0, Cer 24:0; 03 / 26:0, Cer (24:1;O2 / 27:0, Cer 16:1;O2 / 26:0, Cer 18:1; 02 / 24:0, Cer 17:1;O2 / 26:0, Cer 18:1; 02 / 25:0, Cer 20:1;O2 / 24:0, Cer 18:1; 02 / 26:0 and Cer:18:1;O2 / 16:0.

[0046] Preferably, the oxylipins comprise 13-HODE and 13-HOTE.

[0047] Preferably, the analysis of biological markers from a skin sample The SpiderMass technique involves the detection of molecules present in the analyzed biological material. Preferably, the analysis of biological markers includes the identification of these molecules. The molecules are identified, in particular, by tandem mass spectrometry (MS / MS), in positive or negative mode. Even more preferably, this analysis also includes the quantification of these molecules. This quantification allows for the determination, and therefore the measurement, of the expression level of each biological marker present in the signature.

[0048] Furthermore, the inventors have developed methods for evaluating the efficacy of cosmetic or dermatological active ingredients and formulations in the prevention and treatment of all aspects of inflammatory dermatosis. Such methods had never been described before. Indeed, the use of in-vivo and real-time mass spectrometry, particularly SpiderMass technology, makes it possible to directly analyze variations in the molecular components of diseased skin treated with specific cosmetic or dermatological active ingredients or formulations. It is thus possible to identify topical or oral cosmetic or dermatological active ingredients or formulations that restore a molecular signature characteristic of healthy skin.

[0049] In another aspect, the description therefore relates to a method for identifying cosmetic or dermatological active ingredients or formulations that can prevent and / or improve the effects of an inflammatory dermatosis, or for evaluating the efficacy of cosmetic or dermatological active ingredients or formulations that can prevent and / or improve at least one effect of an inflammatory dermatosis. In particular, the invention makes it possible to distinguish cosmetic or dermatological active ingredients or formulations according to their activity in preventing and / or improving at least one effect of an inflammatory dermatosis.

[0050] This method for identifying cosmetic or dermatological active ingredients or formulations includes, in particular, a step of determining the molecular signature of the skin of inflammatory dermatosis treated with the tested cosmetic or dermatological active ingredient or formulation, according to the method described above.

[0051] In a preferred embodiment, the method comprises: a. the application of the active ingredient or the cosmetic or dermatological formulation tested on a skin sample; b. the determination of the molecular signature of the skin sample treated according to the method described above; and c. the identification of said active ingredient or cosmetic or dermatological formulation as enabling the prevention and / or improvement of at least one effect of an inflammatory dermatosis based on the molecular signature of step b).

[0052] In other words, the method for identifying active ingredients or cosmetic or dermatological formulations includes: a. the application of the active ingredient or the cosmetic or dermatological formulation tested on a skin sample; b. the determination of the molecular signature of the treated skin sample, said determination including the analysis of biological markers of a skin sample by the SpiderMass technique; and c. the identification of said active ingredient or cosmetic or dermatological formulation as enabling the prevention and / or improvement of at least one effect of an inflammatory dermatosis based on the molecular signature of step b).

[0053] Preferably, the analysis of biological markers in a skin sample using the SpiderMass technique includes the detection of molecules present in the analyzed biological material. More preferably, the analysis of biological markers includes the identification of the molecules present. The molecules are identified, in particular, by tandem mass spectrometry (MS / MS), for example, by de novo interpretation of spectra or by comparison with databases or standards. Even more preferably, this analysis further includes the quantification of these molecules. This quantification makes it possible to determine, and therefore measure, the expression level of each biological marker present in the signature.

[0054] According to this preferred embodiment, the method for identifying active ingredients or cosmetic or dermatological formulations for preventing and / or improving the effects of an inflammatory dermatosis includes: a. the application of the active ingredient or the cosmetic or dermatological formulation tested on a skin sample; b. the determination of the molecular signature of the treated skin sample, said determination including the measurement of the expression of biological markers of a sample by the SpiderMass technique; and c. the identification of said active ingredient or cosmetic or dermatological formulation as enabling the prevention and / or improvement of at least one effect of an inflammatory dermatosis based on the expression of the biological markers of step b).

[0055] The methods described herein thus make it possible to determine precisely which cosmetic active ingredients have a beneficial effect on the prevention and / or treatment of the effects of an inflammatory dermatosis. The methods of the invention are also suitable for evaluating the activity of formulations. The inventors were thus able to show that certain formulations were more effective than others in preventing and / or limiting the effects of an inflammatory dermatosis, thereby demonstrating the usefulness of the approach taken.

[0056] According to another aspect, the description therefore relates to a method for evaluating the effectiveness of an active ingredient or a cosmetic or dermatological formulation for treating and / or preventing an inflammatory dermatosis.

[0057] This method for evaluating the efficacy of an active ingredient or a cosmetic or dermatological formulation includes in particular a step of determining the molecular signature of the skin of inflammatory dermatosis treated with the active ingredient or the cosmetic or dermatological formulation tested, according to the method described above.

[0058] In a preferred embodiment, the method comprises: a. the application of the active ingredient or the cosmetic or dermatological formulation tested on a skin sample; b. the determination of the molecular signature of the skin sample treated according to the method described above; and c. evaluation of the efficacy of said active ingredient or cosmetic or dermatological formulation to prevent and / or improve at least one effect of an inflammatory dermatosis according to the molecular signature of step b).

[0059] In other words, the method for evaluating the efficacy of an active ingredient or a cosmetic or dermatological formulation includes: a. the application of the active ingredient or the cosmetic or dermatological formulation tested on a skin sample; b. the determination of the molecular signature of the treated skin sample, said determination including the analysis of biological markers of a skin sample by the SpiderMass technique; and c. evaluation of the efficacy of said active ingredient or cosmetic or dermatological formulation to prevent and / or improve at least one effect of an inflammatory dermatosis according to the molecular signature of step b).

[0060] Preferably, the analysis of biological markers in a skin sample using the SpiderMass technique includes the detection of molecules present in the analyzed biological material. More preferably, the analysis of biological markers includes the identification of the molecules present. These molecules are identified, in particular, by tandem mass spectrometry (MS / MS). Even more preferably, this analysis further includes the quantification of these molecules. This quantification makes it possible to determine, and therefore measure, the expression level of each biological marker present in the signature.

[0061] According to this preferred embodiment, the method for evaluating the efficacy of an active ingredient or a cosmetic or dermatological formulation includes: a. the application of the active ingredient or the cosmetic or dermatological formulation tested on a skin sample; b. the determination of the molecular signature of the treated skin sample, said determination including the measurement of the expression of biological markers of a skin sample by the SpiderMass technique; and c. evaluation of the efficacy of said active ingredient or cosmetic or dermatological formulation to prevent and / or improve at least one effect of an inflammatory dermatosis based on the expression of biological markers from step b).

[0062] The active ingredient of interest can be applied directly to the skin. Alternatively, it may be advantageous to formulate the active ingredient of interest, for example, to obtain a liquid composition, in order to facilitate its application to the skin. Thus, according to one embodiment of the invention, the process further comprises a step of formulating the active ingredient, in particular in the form of a liquid solution, especially an aqueous one, prior to the step of applying said active ingredient to the skin.

[0063] The candidate active ingredient is an active ingredient for the prevention and / or treatment of the effects of an inflammatory dermatosis if said candidate active ingredient allows for the modulation of the expression of at least one biological marker of the molecular signature. This modulation may correspond, depending on the case, and in particular depending on the nature of the biological marker, to an increase or a decrease in the expression of said marker. Similarly, the candidate formulation is a formulation for the prevention and / or the treatment of the effects of an inflammatory dermatosis, if said candidate formulation allows modulation of the expression of at least one biological marker of the biological signature. This modulation may correspond, depending on the case, and in particular depending on the nature of the biological marker, to an increase or a decrease in the expression of said marker.

[0064] The term “efficacy of an active ingredient or cosmetic or dermatological formulation in preventing and / or treating at least the effects of an inflammatory dermatosis” refers to the ability of the formulation or active ingredient to cancel out or reduce the effects associated with an inflammatory dermatosis. Prevention, in this context, refers to treatment administered before the development of an inflammatory dermatosis, while reduction refers to treatment administered once the effects of an inflammatory dermatosis have appeared.

[0065] It is important to verify that the active ingredients and cosmetic or dermatological formulations used for the prevention and / or treatment of an inflammatory dermatosis are well tolerated. For example, some currently marketed products could cause irritation if used regularly. Such an effect can only worsen a developing or existing inflammatory dermatosis. It is therefore necessary to verify whether an active ingredient or a cosmetic or dermatological formulation modulates the expression of one or more biological markers of healthy skin before using this active ingredient or formulation to prevent or treat an inflammatory dermatosis. In this context, the methods described above for determining a molecular signature are particularly useful.

[0066] According to another aspect, the invention therefore relates to a method for evaluating the tolerance of an active ingredient or formulation intended to prevent or treat an inflammatory dermatosis.

[0067] This method for evaluating the tolerance of an active ingredient or a cosmetic or dermatological formulation includes in particular a step of determining the molecular signature of the skin of inflammatory dermatosis treated with the active ingredient or the cosmetic or dermatological formulation tested, according to the method described above.

[0068] In a preferred embodiment, the method comprises: a. the application of the active ingredient or the cosmetic or dermatological formulation tested on a skin sample; b. the determination of the molecular signature of the skin sample treated according to the method described above; and c. evaluation of the tolerance of said active ingredient or cosmetic or dermatological formulation according to the molecular signature of step b).

[0069] In other words, the method for evaluating the efficacy of an active ingredient or a cosmetic or dermatological formulation includes: a. the application of the active ingredient or the cosmetic or dermatological formulation tested on a skin sample; b. the determination of the molecular signature of the treated skin sample, said determination including the analysis of biological markers of a skin sample by the SpiderMass technique; and c. evaluation of the tolerance of said active ingredient or cosmetic or dermatological formulation according to the molecular signature of step b).

[0070] Preferably, the analysis of biological markers in a skin sample using the SpiderMass technique includes the detection of molecules present in the analyzed biological material. More preferably, the analysis of biological markers includes the identification of the molecules present. These molecules are identified, in particular, by tandem mass spectrometry (MS / MS). Even more preferably, this analysis further includes the quantification of these molecules. This quantification makes it possible to determine, and therefore measure, the expression level of each biological marker present in the signature.

[0071] According to this preferred embodiment, the method for evaluating the efficacy of an active ingredient or a cosmetic or dermatological formulation includes: a. the application of the active ingredient or the cosmetic or dermatological formulation tested on a skin sample; b. the determination of the molecular signature of the treated skin sample, said determination including the measurement of the expression of biological markers of a skin sample by the SpiderMass technique; and c. evaluation of the tolerance of said active ingredient or cosmetic or dermatological formulation based on the expression of biological markers from step b).

[0072] The active ingredient of interest can be applied directly to the skin. Alternatively, it may be advantageous to formulate the active ingredient of interest, for example, to obtain a liquid composition, in order to facilitate its application to the skin. Thus, according to one embodiment of the invention, the process further comprises a step of formulating the active ingredient, in particular in the form of a liquid solution, especially an aqueous one, prior to the step of applying said active ingredient to the skin.

[0073] The active ingredient is well tolerated by the skin if said active ingredient does not significantly modulate the expression of the biological marker. Similarly, the cosmetic or dermatological formulation is well tolerated if the expression of the biological marker is not significantly modulated by its addition to the skin. "Significant" means a result obtained by performing a statistical test, such as a univariate Wilcoxon test, and having a p-value less than 0.05, preferably a p-value less than 0.01, more preferably a p-value less than 0.001. The appropriate statistical tests are well known to those skilled in the art. This modulation may correspond, depending on the circumstances and in particular on the nature of the biological marker, to an increase or a decrease in the expression of said marker. In particular, the expression of inflammatory markers is known to be increased in the skin of atopic dermatosis. In a preferred embodiment, the biological marker in step b) is an inflammatory marker.

[0074] The term "augmented", as used here, means a larger quantity, for example, a quantity slightly greater than the original quantity, or for example a quantity in large excess compared to the original quantity, and in particular all quantities in the interval.Alternatively, "increase" may refer to a quantity or activity that is at least 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, or 20% greater than the quantity or activity to which the increased quantity or activity is being compared, or at least 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, 110%, 120%, 130%, 140%, 150%, 160%, 170%, 180%, 190%, 200%, 250%, 300%, 350%, 400%, 450%, 500%, 550%, 600%, or 650%. 700%, 750%, 800%, 900%, 950%, 1000%, 1100%, 1200%, 1300%, 1400%, 1500%, 1600%, 1700%, 1800%, 1900% or 2000% more than the quantity or activity to which the increased quantity or activity is being compared. The terms "increased", "greater than", and "increased" are used interchangeably here.

[0075] The term "reduced", as used here, means a smaller quantity, for example, a quantity slightly less than the original quantity, or for example a quantity greatly reduced compared to the original quantity, and in particular all quantities in the interval.Alternatively, "decrease" may refer to a quantity or activity that is at least 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, or 20% less than the quantity or activity to which the decreased quantity or activity is being compared, or at least 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, 110%, 120%, 130%, 140%, 150%, 160%, 170%, 180%, 190%, 200%, 250%, 300%, 350%, 400%, 450%, 500%, 550%, 600%, or 650%. %, 700%, 750%, 800%, 900%, 950%, 1000%, 1100%, 1200%, 1300%, 1400%, 1500%, 1600%, 1700%, 1800%, 1900% or 2000% less than the quantity or activity to which the decreased quantity or activity is compared. The terms "decreased", "less than", and "reduced" are used interchangeably here.

[0076] In order to determine whether the expression of a marker is increased or decreased in the skin treated with the active ingredient or the tested cosmetic or dermatological formulation, the the level of expression of said marker can be compared with a reference level of expression.

[0077] According to this preferred embodiment, step c) of the above methods may include a comparison of the expression level of the biological marker from step b) with a reference expression level.

[0078] For the purposes of this application, "a reference expression level of a biological marker" means any expression level of that marker used as a reference. For example, a reference expression level may be obtained by measuring the expression level of the marker of interest in a sample of healthy skin. Such a sample of healthy skin may, for example, be the skin of a healthy subject or one without any apparent pathology. Alternatively, a skin sample without any apparent pathology may be used, but taken from a subject with an inflammatory dermatosis.

[0079] In other embodiments, the reference expression level of a biological marker corresponds to the expression level of said marker in a skin sample in the absence or presence of a particular treatment. For example, in one particular embodiment, the reference expression level of a biological marker is obtained by measuring the expression of said marker in a skin sample from the subject that has not been exposed to an active ingredient or formulation. In another particular embodiment, the expression of said marker is measured in the skin sample treated with an active ingredient or formulation known to be effective against at least one effect of an inflammatory dermatosis.

[0080] A person skilled in the art will readily understand that comparing the expression level of the biological marker with a reference expression level will be all the more relevant if the marker expression level and the reference expression level have been measured using the same in vivo and real-time mass spectrometry technique. Preferably, both the marker expression level and the reference expression level are measured using the SpiderMass technique. This technique allows for the analysis of samples of uniform size and volume, thanks to the laser ablation step. EXAMPLES

[0081] The following examples are provided here by way of illustration and are not, unless otherwise indicated, intended to be limiting.

[0082] Example 1: Exploratory study using real-time mass spectrometry (SpiderMass analysis) for the analysis of molecular profiles of the epidermis of subjects with chronic inflammatory dermatosis: atopic dermatitis group versus control group

[0083] The aim of this study is to characterize the molecular signals, particularly lipid signals, of subjects with or without dermatosis.

[0084] This is an exploratory, single-center, comparative study conducted in a control group and a group of subjects with atopic dermatitis of the upper limbs.

[0085] The two groups are included in parallel. They belong to the same age group and are as balanced as possible in terms of gender.

[0086] The samples and measurements taken in the areas under study are: • For the dermatosis group: lesion area, perilesional area and reference area, as well as: • measurements of hydration index (HI) and transepidermal water loss (TEWL) on the upper limbs (excluding hands) • SpiderMass measurements on the upper limbs for the lesion area and the peri-lesional area and on the inner side of the forearm for the reference area. • For the control group: same areas corresponding to those of the dermatosis group.

[0087] 43 subjects are included, 21 in the pathological group and 22 in the control group.

[0088] The data are MS spectra acquired by SpiderMass technology of the stratum comeum, in positive mode.

[0089] A differential analysis is performed to identify peaks with significant changes by comparing the following data combinations: • Intergroup: • Comparison of reference areas between subjects with atopic dermatitis and control subjects, • Comparison of lesion areas between atopic dermatitis subjects and control subjects. • Intra-group: • Comparison in subjects with atopic dermatitis of lesioned areas with peri-lesional areas, • Comparison in subjects with atopic dermatitis of lesioned areas with reference areas.

[0090] Data preprocessing is performed using a program developed in the Matlab Mathworks environment. During the exploratory analysis, average spectra are calculated. A TIC effect is observed during this analysis, so differential analysis will be performed with a fit to Log2 (TIC). Finally, for all comparisons, a model is used, where a model is applied to each mass. A mixed linear model explains the intensity changes. A Benjamini-Hochberg (BH) multiple test correction is performed on all peaks. Results

[0091] The description of the significantly modulated masses on the 4 comparisons is given in Table 1. As there are a large number of modulated signals in each of the comparisons, the inventors focused on the signals which have an absolute Fold Change factor (FCabs for "Absolute Fold Change") of at least 2.0.

[0092] Table 1: Details of significantly modulated signals including overproduced and underproduced signals for each of the comparisons studied in the study as well as signals after filtering with an absolute change factor (FCabs for "Absolute Fold Change") >2.

[0093] [Tables 1] ZR DA vs C TL ZL DA vs C TL DA ZL vs ZR DA ZL vs Z PL Significantly modulated signals 106 377 337 191 Overproducts / Byproducts 1 / 105 72 / 305 137 / 200 62 / 129 Signals after filtering (FCabs > 2) 16 243 49 8 Overproducts / Byproducts 1 / 15 41 / 202 8 / 41 0 / 8

[0094] ZR: reference zone; ZL: lesion zone; ZPL: peri-lesional zone; DA: atopic dermatitis, CTL: control.

[0095] Among the masses that were significantly modulated and had an FCabs > 2, the inventors identified two confidence levels: level 2 corresponds to identification using MS / MS fragmentation, and level 3 corresponds to identification using software, databases, and literature, but only based on the mass of the parent ion; therefore, no fragmentation is performed for this confidence level. The number of masses identified at each level for the three comparisons is detailed in Table 2.

[0096] Table 2: Details of the signals significantly modulated with an FCabs > 2 with their distribution in the different identification levels.

[0097] [Tables2] ZR DA vs CTL ZL DA vs CTL DA ZL vs ZR DA ZL vs ZPL Signals after filtering with an FCabs > 2 16 243 49 8 By-products / By-products 1 / 15 41 / 202 8 / 41 0 / 8 Signals identified at level 1 / equivalent in molecules 0 0 0 0 Signals identified at level 2 / equivalent in molecules 7 / 6 138 / 71 35 / 23 6 / 5 Signals identified at level 3 / equivalent in molecules 4 / 3 60 / 45 9 / 7 0 Isotopes (levels 2 and 3) 2 73 13 1

[0098] ZR: reference zone; ZL: lesion zone; ZPL: peri-lesional zone; DA: atopic dermatitis, CTL: control.

[0099] The masses that are not identified are mainly masses with intensities too low to be fragmented, this represents 90.2% of the unidentified masses, the other masses could not be identified because they had too low an m / z or because the interpretation of the fragmentation was not successful.

[0100] Identification of common and different masses between the 3 comparisons

[0101] By comparing the significantly modulated masses and with an FCabs > 2 between In the ZR DA vs CTL and ZL DA vs CTL comparisons, only three masses were common and were not found to be significantly different in the other two comparisons. These three masses correspond to alpha-tocopherol acetate (level 2) and a hexceramide (level 3); the last mass is an isotope. Furthermore, the eight masses from the DA ZL vs ZPL comparison were also found in the two other comparisons involving the injured area. Finally, 43 masses were found to be common between the ZL DA vs CTL and DA ZL vs ZR comparisons. These results are summarized in Table 3.

[0102] Table 3: Common masses between the different pairwise comparisons

[0103] [Tables3] ZR DA vs CT L ZL DA vs CTL DA ZL vs ZR DA ZL vs ZPL ZR DA vs CTL 16 - - - ZL DA vs CTL 3 243 - - DA ZL vs ZR 0 43 - - DA ZL vs ZPL 0 8 8 8

[0104] ZR: reference zone; ZL: lesion zone; ZPL: peri-lesion zone; DA: atopic dermatitis, CTL: control. Identification by fragmentation: level 2

[0105] 107 molecules were identified across all comparisons, but some Some of them were common to several comparisons. In total, 81 molecules were therefore identified by fragmentation.

[0106] The 72 molecules of ZL DA vs CTL are divided into 7 superclasses (fatty acyls; glycerolipids; sphingolipids; prenol lipids; organoheterocyclic compounds; organic oxygen compounds; organic acids) and 15 main classes (fatty acids and conjugates; eicosanoids; fatty aldehydes; fatty esters; fatty amides; monoacylglycerols; diacylglycerols; triacylglycerols; sphingoid bases; ceramides; quinones and hydroquinones; azoles; indoles and derivatives; organooxygen compounds; carboxylic acids and derivatives).

[0107] In the ZR DA vs CTL comparison, the 6 molecules are divided into two superclasses (glycerolipids and prenol lipids) and two main classes (diacylglycerols and quinones and hydroquinones).

[0108] Then the 24 molecules of the DA ZL vs ZR comparison are divided into 4 superclasses (fatty acyls; sphingolipids; organoheterocyclic compounds; organic acids and derivatives) and 8 main classes (fatty acids and conjugates; fatty aldehydes; fatty esters; sphingoid bases; ceramides; azoles; indoles and derivatives; carboxylic acids and derivatives).

[0109] Finally in DA ZL vs ZPL, 5 molecules are divided into 3 superclasses (fatty acyls; sphingolipids; organoheterocyclic compounds) and 4 main classes (fatty esters; sphingoid bases; ceramides; azoles).

[0110] Fatty acyls: 17 molecules

[0111] A total of 17 fatty acyl molecules are identified by fragmentation, distributed into 5 groups: 8 fatty acids, 3 fatty aldehydes, 2 prostaglandins, 2 cerides and 2 esters of fatty acid branched by a hydroxylated fatty acid.

[0112] Eight fatty acids are identified and are modulated in ZL DA vs CTL, there are also 2 which are modulated with an FCabs > 2 in DA ZL vs ZR, presented in Table 4.

[0113] Table 4: List of fatty acids significantly overproduced and underproduced with an FCabs > 2 in the 3 comparisons.

[0114] [Tables4] Family Name Formula FC: ZR DA vs CTL FC: ZLDA vs CTL FC: DA ZL vs ZR FC: DA ZL vs ZPL AG 8:0 Saturated C8H16O2 NS 2.56 NS NS AG 12:0 Saturated C12H24O2 NS 2.63 NS NS AG 18:0 Saturated C18H36O2 NS 2.36 NS NS AG 24:0 Saturated C24H48O2 NS -3.26 -1.94 -1.58 AG 26:0 Saturated C26H52O2 NS -4.89 -2.63 -1.84 AG 20:4 Unsaturated C20H32O2 NS 3.19 2.03 1.51 AG 26:1 Unsaturated C26H50O2 NS -2.22 -1.31 NS AG 30:1 Unsaturated C30H58O2 NS -2.7 -1.73 -1.35

[0115] FC: Fold change; NS: not significant.

[0116] Free fatty acids are an integral part of the lipid matrix of the stratum corneum since their COOH group at the end of the chain contributes to maintaining the acidity of the skin. C24:0 and C26:0 fatty acids represent 50% of the weight of free fatty acids in the stratum corneum.

[0117] Three fatty aldehydes (FAs) are identified in this study ALG 23:0 (FCm = -2.2 in ZL DA vs CTL and FCm = -2.09 in DA ZL vs ZR; ALG 24:0 (FCm = -2.4 in ZL DA vs CTL); ALG 28:0 (FCm = -3.4 in ZL DA vs CTL and FCm = -2.19 in DA ZL vs ZR).

[0118] There is therefore always an under-expression of this family of molecules in lesion areas compared to non-lesion areas and in DA subjects versus CTL subjects.

[0119] Two prostaglandins are identified as being significantly modulated between lesion areas in DA subjects and controls.

[0120] These two molecules are derivatives of prostaglandin F2a, Dinor PGF2alpha methyl ether and PGF2alpha methyl ether (FCm = 5.91 and FC = 5.94 for ZL DA vs CTL).

[0121] In this study, 4 fatty ester molecules appear to be significantly modulated: - Fatty ester 18:2 / 300 (FA 30:0), FCm = -6 in ZL DA vs CTL; FCm = -2.87 in DA ZL vs ZR and FCm = -2.05 in DA ZL vs ZPL - Fatty ester 18:2 / 320 (AG 32:0), FCm = -3.5 in ZL DA vs CTL

[0122] The other 2 fatty esters identified are cerides, they are only modulated in ZL DA vs CTL with FCm = 4.36 for ceride (1:0 / 7:0) and FCm = 2.09 for ceride (2:0 / 12:0).

[0123] The 3 families of glycerolipids are identified in this study. In the comparison of ZL DA vs CTL, an increase in a monoacylglycerol was found in the DA subjects, MG 18:1 (FCm = 2.74), and an increase in a diacylglycerol, the DG (18:1 / 18:1), with an FCm = 2.51 and an increase in 4 triacylglycerols, represented in Table 5.

[0124] Table 5: List of glycerolipids overproduced and by-products significantly with an FCabs > 2 in both comparisons.

[0125] [Tables5] Name Raw formula FC: ZR DA vs CTL FC: ZL DA vs CTL DG 30:1 C33H62O5 -2.17 -1.77 DG 30:0 C33H64O5 -2.03 -1.6 DG 31:0: DG (15:0 / 16:0) C34H66O5 -2 NS DG 32:1: DG (16:0 / 16:1) C35H66O5 -2.08 -1.54 DG 33:1: DG (16:1 / 17:0) C36H68O5 -2.07 NS TG 52:2: TG (16:0 / 18:1 / 18:1) C55H102O6 NS 2.23 TG 54:4: TG (18:1 / 18:1 / 18:2) C57H102O6 NS 2.97 TG 54:3: TG (18:1 / 18:1 / 18:1) C57H104O6 NS 3.2 TG 54:2: TG (16:1 / 18:1 / 20:1); TG (18:0 / 18:1 / 18:1) C57H106O6 NS 2.37

[0126] FC: fold change; NS: not significant.

[0127] Sphingolipids are the most modulated class of lipids (42 molecules) in AD subjects. They are also the most represented lipids in the stratum corneum.

[0128] Among these sphingolipids, 12 sphingoid base (SBP) molecules and 30 ceramides.

[0129] 12 sphingoid bases are identified as significantly modulated and distributed In 3 of the 4 comparisons studied, all these molecules were modulated in the ZL DA vs CTL comparison. Among these 12 molecules, 7 were significantly modulated in the DA ZL vs ZR comparison and 3 in the DA ZL vs ZPL comparison. These sphingosine bases comprise 3 subclasses: sphingosines, sphinganines, and phytosphingosines. These results are detailed in Table 6.

[0130] Table 6: List of sphingoid bases significantly underproduced with an FCabs > 2 in the 3 comparisons.

[0131] [Tableauxô] Name Raw formula FC: ZL DA vs CTL FC: DA ZL vs ZR FC: DA ZL vs ZPL Phy to sphingo sine C18H39NO3 -2.06 -1.57 -1.34 BSP 20:0 ; 03 C20H43NO3 -2.15 -1.73 -1.51 BSP 22:0; 03 C22H47NO3 -2.22 -1.74 -1.49 BSP 20:1; 03 C20H43NO3 -2.54 -2.04 -1.53 ​​BSP 25:0; 03 C25H53NO3 -3.02 -2.42 -1.7 BSP 26:1; 02 C26H53NO2 -2.9 -1.84 -1.52 BSP 27:1; 02 C27H55NO2 -2.64 -2.23 -1.65 BSP 24:0; 02 C24H51NO2 -2.5 -1.86 -1.61 BSP 25:0; 02 C25H53NO2 -3.36 -2.57 -2.03 BSP 26:0; 02 C26H55NO2 -3.73 -2.79 -2.13 BSP 27:0; 02 C27H57NO2 -3.82 -2.4 -1.98 BSP 28:0; 02 C28H59NO2 -4.19 -2.8 -2.09

[0132] FC: fold change.

[0133] Thirty ceramides (based on their molecular formula; see Table 7 below) are significantly modulated between lesioned and non-lesioned areas, as seen in two comparisons: ZL DA vs CTL, comprising 26 of the 30 modulated ceramides, and the DA ZL vs ZR comparison, comprising the remaining 4 modulated ceramides from the study. Several ceramide families are modulated. All these results are detailed in Table 7.

[0134] Table 7: List of ceramides significantly overproduced and underproduced with an FCabs > 2 in both comparisons.

[0135] [Tables7] Name Raw formula FC:ZL DA vsC TL FC:DA ZL vs ZR Cer 41:0;O4: Cer (17:0;O3 / 24:0; (2OH)) C41H83NO5 -2.28 -1.43 Cer 43:0;O4: Cer (18:0;O3 / 25:0;O); Cer (17:0; 0 3 / 26:0;O) C43H87NO5 -2.46 -1.38 Cer 45:0;O4: Cer (21:0;O3 / 24:0;O) C45H91NO5 -2.13 NS Cer 47:0;O4: Cer (22:0;O3 / 25:0;O) C47H95NO5 -2.09 NS Cer 48:0;O2: Cer (24:0;O2 / 24:0); Cer (23:0; 02 / 2 5:0) C48H97NO3 -2.61 -1.46 Cer 50:0;O2: Cer (24:0;O2 / 26:0); Cer (26:0; 02 / 2 4:0) C50H101NO3 -2.56 -1.63 Cer 49:0;O2: Cer (24:0;O2 / 25:0) C49H99NO3 -2.05 -1.27 Cer 50:1 ;O3 : Cer (22:1 ;O3 / 28:0) ; Cer (20:1 ; 03 / 3 0:0) C50H99NO4 -3.22 -1.63 Cer 48:1 ;O3 : Cer (20:1 ;O3 / 28:0) C48H95NO4 -3.19 -1.69 Cer 47:1 ;O3 : Cer (20:1 ;O3 / 27:0) ; Cer (21:1 ; 03 / 2 6:0) C47H93NO4 -2.87 NS Cer 49:1 ;O3 : Cer (21:1 ;O3 / 28:0) C49H97NO5 -2.77 -1.58 Cer 45:1 ;O3 : Cer (18:1 ;O3 / 27:0) ; Cer (20:1 ; 03 / 2 5:0) C45H89NO4 -2,26 NS Cer 46:1 ;O3 : Cer (20:1 ;O3 / 26:0) ; Cer (18:1 ; 03 / 2 8:0) C46H91NO4 -2.25 NS Cer 44:1 ;O3 : Cer (18:1 ;O3 / 26:0) C44H87NO4 -2.21 NS Cer 43:0 ;O3 : Cer (17:0 ;O3 / 26:0) C43H87NO4 -3.95 -1.68 Cer 42:0 ;O3 : Cer (18:0 ;O3 / 24:0) C42H85NO4 -3.63 -1.56 Cer 45:0 ;O3 : Cer (20:0 ;O3 / 25:0) ; Cer (18:0 ; 03 / 2 7:0) C45H91NO4 -3.38 -1.69 Cer 41:0 ;O3 : Cer (17:0 ;O3 / 24:0) C41H83NO4 -3.24 -1.57 Cer 46:0 ;O3 : Cer (22:0 ;O3 / 24:0) ; Cer (20:0 ; 03 / 2 6:0) C46H93NO4 -3.17 -1.67 Cer 47:0 ;O3 : Cer (22:0 ;O3 / 25:0) C47H95NO4 -3.14 -1.7 Cer 44:0 ;O3 : Cer (18:0 ;O3 / 26:0) ; Cer (20:0 ; 03 / 2 4:0) C44H89NO4 -3.05 -1.46 Cer 48:0 ;O3 : Cer (22:0 ;O3 / 26:0) C48H87NO4 -2.86 -1.61 Cer 49:0;O3: Cer (22:0;O3 / 27:0) C49H99NO4 -2.56 -1.55 Cer 40:0;O3: Cer (16:0;O3 / 24:0); Cer (18:0; 03 / 2 2:0) C40H81NO4 -2.24 NS Cer 50:0;O3: Cer (22:0;O3 / 28:0); Cer (24:0; 03 / 2 6:0) C50H101NO4 -2.21 -1.56 Cer 52:1;O2: Cer (24:1;O2 / 27:0) C52H103NO3 -2.26 NS Cer 42:1;O2: Cer (16:1;O2 / 26:0); Cer (18:1; 02 / 2 4:0) C42H83NO3 NS 2.19 Cer 43:1;O2: Cer (17:1;O2 / 26:0); Cer (18:1; 02 / 2 5:0) C43H85NO3 NS 2.02; Cer 44:1;O2: Cer (20:1;O2 / 24:0); Cer (18:1; 02 / 2 6:0) C44H87NO3 NS 2.09 Cer 34:1;O2: Cer (18:1;O2 / 16:0) C34H67NO3 1.7 2.55

[0136] FC: fold change

[0137] Only one prenol is modulated in this study, namely alpha-tocopherol acetate (FCm = 3.6 for ZL DA vs CTL).

[0138] Finally, 9 metabolite molecules are modulated in 3 of the 4 comparisons in the study; 1 dipeptide and 4 amino acids and analogues are found; the data are found in Table 8 below.

[0139] Also found is an imidazole, urocanate (FCm = -6.02 in ZL DA vs CTL, FCm = -3.93 in DA ZL vs ZR and FCm = -2.09 in DA ZL vs ZPL), and two indoles, namely andrenochrome o-semiquinone (FCm = -3.62 in ZL DA vs CTL and FCm = 2.37 in DA ZL vs ZR) and indolactic acid (FCm = -2.43 in ZL DA vs CTL). Finally, a carbonyl compound, 2-hydroxybenzyldehyde (FCm = 3.44 in ZL DA vs CTL).

[0140] Table 8: List of molecules from the amino acids, peptides and analogues group significantly modulated in 2 comparisons.

[0141] [Tables8] Name Molecular Formula FC: ZL DA vs CTL FC: DA ZL vs ZR Pyroglutamic acid C5H7NO3 -3.59 -2.1 Glutamic acid C5H9NO4 -3.56 NS Histidine C6H9N3O2 -3.53 NS Citrulline C6H13N3O3 -7.73 -2.53 His-Pro C11H16N4O3 -5.67 -2.37

[0142] FC: fold change.

[0143] The skin's barrier function is largely ensured by its brick and mortar system. This system is composed of 2 parts, the first, the "brick," corresponds to proteins such as keratin and filaggrin, and the second part, the "mortar," corresponds to the lipids surrounding these proteins, such as ceramides, free fatty acids, and cholesterol esters.

[0144] A disruption of one of the two parts leads to a defect within the stratum comeum and therefore an alteration of the barrier function. In atopic dermatitis, both parts are disrupted. The disruption of the "mortar" part occurs via a decrease in very long-chain free fatty acids caused by a decrease in the expression of elongases such as ELOVL1 and ELOVL4. Other molecules heavily involved in the "mortar" part are ceramides. These are These lipids are major components of the stratum comeum, representing 50% of the total lipid mass and playing an essential role within this epidermal layer. They consist of a chain of hydrophobic fatty acids linked to a sphingoid base containing an amine. Fifteen classes of ceramides are found in the human stratum comeum.

[0145] Ceramides, like free fatty acids, are affected by decreased elongase expression, leading to a reduction in long-chain ceramides and an increase in short-chain ceramides in subjects with atopic dermatitis. In this study, these results are consistent with the literature (Janssens et al., 2012 Journal of Lipid Research 53, 2755-2766). Generally, the amount of ceramides decreases in lesioned areas. Despite this general decrease in ceramides, some ceramide families, such as [NS] ceramides, show an increase in their concentration. Conversely, ceramides of the [NP], [AP], and [NH] families, as well as long-chain [NDS] ceramides, show a decrease in their concentration in lesions. The reduction of long-chain ceramides leads to a decrease in the barrier function because the shorter the chains, the fewer interactions are possible to maintain the "mortar" function of the stratum comeum.Finally, phytoceramides [NP] and [AP] are known to act as water-binding agents and to strongly maintain the structure of the stratum corneum because they possess more OH groups on their backbone, resulting in stronger hydrogen bonds. Therefore, a decrease in these molecules inevitably leads to water loss from the skin. All the results on these ceramides correlate perfectly with the results of other studies in the literature (Shen et al., 2018 Dermatitis 29, 219-222).

[0146] For sphingoid bases, it is their chain length that will determine whether they are over- or under-expressed. Indeed, sphingoid bases with chains of 18 carbons and less will be increased in lesioned areas compared to non-lesioned areas, which is consistent with what is reported in the literature (Toncic et al., 2020, International Journal of Molecular Sciences 21, 1958).

[0147] A third type of lipid is involved in the dysregulation of barrier function in atopic dermatitis: fatty esters. These are molecules secreted by keratinocytes. In atopic dermatitis, elongases act on these fatty esters, leading to a decrease in very long-chain fatty esters, which also reduces barrier function.

[0148] The most representative molecule of the inflammatory state in subjects with atopic dermatitis is arachidonic acid. Indeed, arachidonic acid is an eicosanoid and, like all eicosanoids, is produced by all types of skin cells and contributes to homeostatic processes and inflammatory responses. It is a lipid mediator and precursor of several prostaglandins and oxylipins. For a long time, an increase in the concentration of this fatty acid has been observed in lesional skin; in this study, the inventors observed the same conclusions with a marked increase in arachidonic acid in lesional skin compared to control subjects or to the non-lesional skin of subjects with atopic dermatitis.

[0149] Alpha-tocopherol, or vitamin E, is normally known for its anti-inflammatory action; however, even today, the quantification of alpha-tocopherol in patients with atopic dermatitis yields contradictory results. This demonstrates that we currently do not fully understand the processes and metabolism of vitamin E in atopic dermatitis. In this study, only alpha-tocopherol acetate was significantly modulated. This molecule is widely used in cosmetics because it is a more stable form of vitamin E, but there is little literature on the presence of this molecule endogenously in the skin.

[0150] As with vitamin E, prostaglandins are a family of molecules that play an important role in inflammation, as they are involved in oxidative stress, such as in vitiligo or atopic dermatitis (Tôrôcsik et al., 2019 Experimental Dermatology 28, 177-189). Oxidative stress is an imbalance between the production of free radicals and the ability of a biological system to detoxify reactive intermediates or repair the resulting damage. The two prostaglandins identified in this study are derivatives of Prostaglandin F2a, which has been described in the literature as having the ability to induce common itching in subjects with atopic dermatitis. The increase in prostaglandins is therefore correlated with the increase in the biosynthesis of cyclooxygenases, which are the main enzymes in the synthesis of prostaglandins, which are themselves increased in cases of atopic dermatitis.The significant increase in these molecules clearly demonstrates the inflammatory nature of atopic dermatitis.

[0151] Finally, glutamate is a common denominator among several diseases with an inflammatory state, such as rheumatoid arthritis, obesity, and Alzheimer's disease, where it is found at higher concentrations in patients with these pathologies compared to healthy subjects. In our study, the elevated levels of glutamate in lesional skin could be linked to an increased need for glutamine, which is an important energy source for immune cells. Indeed, in lymphocytes, glutamate is the main intermediate in glutamine metabolism.

[0152] Oxidative stress refers to the oxidation of biological compounds in our body by free radicals. This oxidative stress plays an important pathogenic role. In atopic dermatitis, adrenochrome o-semiquinone is one of the molecules influencing oxidative stress and was significantly modulated in this study. Indeed, its levels were reduced in the affected area compared to the unaffected area in subjects with atopic dermatitis, as well as in control subjects. Adrenochrome is the oxidized form of adrenaline, the quintessential stress hormone, and is also the precursor of melanin, the skin's primary pigment. This pigment is also highly reactive to oxidative stress, such as during intense UV exposure, like sunburn. Adrenochrome o-semiquinone is a reducing agent that reacts rapidly in the presence of oxygen. A decrease in this molecule in affected areas leads to an accumulation of reactive oxygen species and therefore an increase in oxidative stress.

[0153] Filaggrin is one of the proteins involved in the "brick and mortar" system of epidermal formation. In addition to its structural role, filaggrin is slowly degraded by proteases to release hygroscopic amino acids such as trans-urocanic acid and pyroglutamic acid. Together, these form natural moisturizing factors essential for the integrity of the epidermal barrier, pH balance, and for maintaining epidermal hydration (Riethmuller et al., 2015 Journal of Allergy and Clinical Immunology 136, 1573-1580e2). In this present study, it is clearly shown that these hygroscopic amino acids are greatly reduced in lesional skin compared to non-lesional skin, sometimes by a factor of 2. In addition to trans-urocanic acid and pyroglutamic acid, the degradation of filaggrin leads to the release of citrulline.This amino acid originates from a post-translational modification of filaggrin on arginine residues, citrullination. In the study by Winget et al. (J Invest Dermatol 136, 1732-1735, 2016), the authors demonstrated a decrease in the citrullination of arginine residues in filaggrin. These results explain the decrease in citrulline observed in our study when comparing lesioned areas with non-lesioned areas.

[0154] In conclusion, the inventors highlighted a significant change in the skin's molecular profile using the SpiderMass system, both between lesioned and non-lesioned areas in subjects with atopic dermatitis and between lesioned and perilesional areas. These changes affect several families of molecules, particularly sphingolipids, as they are heavily involved in maintaining the barrier function, which is itself severely impaired in atopic dermatitis. It is not only the quantity of lipids that is correlated with the barrier function, but also the nature of these lipids and their chain length, since part of the lipid elongation metabolism is inhibited in subjects with AD.

[0155] This SpiderMass system is sufficiently sensitive, it allows to characterize all these molecular modifications within the stratum comeum itself.

[0156] In addition to its barrier function component, atopic dermatitis induces a significant disruption of inflammatory functions. Several molecules and families of molecules are involved in this mechanism, such as prostaglandins, certain fatty acids, and glutamate. These alterations in these molecules consistently demonstrate the strong inflammatory component in atopic dermatitis.

[0157] Finally, modifications of certain skin proteins, such as filaggrin, lead to a significant decrease in hygroscopic amino acids and therefore a decrease in skin hydration.

[0158] These results are not only consistent with previously published studies showing molecular modulations in the skin of subjects with atopic dermatitis, but also demonstrate a significant technological advance, as all these results are obtained without any invasive procedures. This is an advantage for the patient, but also for the practitioner, who obtains more precise and numerous results for assessing the state of the skin pathology.

[0159] Example 2: Evaluation of the effectiveness of a treatment

[0160] The aim of this study is to evaluate and quantify the recovery of pathological skin during a cosmetic treatment.

[0161] The laser measurements according to the invention should make it possible to monitor over several days and quantify the recovery or lack thereof of pathological skin during a daily cosmetic treatment. This technique according to the invention appears to be very suitable for clinical studies.

[0162] The lipid profile of 63 subjects with seborrheic dermatitis of the scalp is thus evaluated before and after a two-week treatment, this treatment consists of a local application of an antifungal shampoo on the entire scalp and especially on the areas affected by the dermatitis.

[0163] This shampoo is the product sold by Ducray under the name KELUAL DS containing 2 antifungals, Ciclopiroxolamine and Piroctone olamine.

[0164] This study, carried out on 63 subjects, includes 2 visits, a first one to include the subjects, on J0, which is the start of treatment; and a second visit 15 days later (J15) to close the end of this treatment.

[0165] The data are MS spectra acquired by SpiderMass technology in positive mode. These analyses are performed on sebum samples on cigarette papers.

[0166] For the absorbent paper sample, from the SpiderMass analysis, a differential analysis is carried out to study the peaks with significantly different changes between J0 and J15. Results

[0167] For the comparison between J0 and J15, 1211 significantly modulated masses appear, with 315 masses appearing overexpressed at J15 and 896 underexpressed at J15. In view of the very large number of results, the analysis will be carried out on the significantly modulated masses, therefore with an absolute Fold Change (FCabs) greater than 1.5. With filtering, 460 modulated masses are obtained (247 masses overexpressed at J15 and 213 masses underexpressed at J15) without the product masses.

[0168] Table 9: Distribution of significant signals

[0169] [Tables9] Absolute fold change Number of masses 1.5 < FCabs < 2 182 2 < FCabs < 3 112 3 < FCabs < 4 55 4 < FCabs < 5 49 5 < FCabs < 6 27 6 < FCabs < 7 16 7 < FCabs < 8 6 FCabs > 8 12

[0170] In total, of the 460 significantly modulated masses, 413 masses are assigned. Among these masses, there are 2 confidence levels: level 2 corresponds to identification with fragmentations in MS / MS and level 3 corresponds to identification with different software but only on the masses of the parent ion, therefore no fragmentation is performed for this confidence level.

[0171] Of the 460 significantly modulated masses, 117 are isotopes and 150 are identified as lipids or metabolites by fragmentation, representing 133 molecules. These molecules are divided into 7 superclasses (fatty acyls, glycerolipids, sphingolipids, prenol lipids, organoheterocyclic compounds and organic acids and derivatives) and 11 main classes (fatty acids and conjugates, octadecanoic acids, fatty esters, monoacylglycerols, diacylglycerols, triacylglycerols, ceramides, acylceramides, quinones and hydroquinones, and finally amines and imidazoles). Fatty acyls

[0172] A total of 30 fatty acyl molecules are identified by fragmentation, forming 4 groups: 22 unsaturated fatty acids, 5 saturated fatty acids, 2 oxylipins and one ceride.

[0173] Table 10 below describes all the identified unsaturated fatty acid molecules.

[0174] Table 10: List of unsaturated fatty acid molecules significantly overexpressed and underexpressed with an FCm > 1.5.

[0175] [TableauxlO] FCm Nom Formulas FCm Nom Formulas -1.72 AG 8:1 C8H14O2 -3.55 AG 14:3 C14H22O2 -1.59 AG 9:1 C9H16O2 -3.71 AG 17:2 C17H30O2 -1.70 AG 10:1 C10H18O2 -1.72 AG 18:1 C18H34O2 -2.37 AG 10:2 C10H16O2 -1.57 AG 18:2 C18H32O2 -1.59 AG 11:1 C11H20O2 -2.00 AG 19:1 C19H36O2 -1.64 AG 11:2 C11H18O2 -1.67 AG 19:2 C19H34O2 -2.73 AG 11:3 C11H16O2 -1.97 AG 20:1 C20H38O2 -1.65 AG 12:1 C12H22O2 -1.53 ​​AG 20:2 C20H36O2 -1.64 AG 12:2 C12H20O2 -1.83 AG 20:3 C20H34O2 -2.07 AG 13:1 C13H24O2 -1.57 AG 20:4 C20H32O2 -1.75 AG 13:2 C13H22O2 -1.55 AG 22:1 C22H42O2

[0176] 22 unsaturated fatty acids are identified between JO and J15. All these fatty acids are Under-expressed after 2 weeks of treatment. Unsaturated fatty acids can be considered metabolites of Malassezia furfur (a commensal yeast involved in seborrheic dermatitis) which consumes monoacylglycerols, diacylglycerols, and triacylglycerols in sebum. Most of these molecules have irritant activity, such as oleic acid (18:1 fatty acid) and arachidonic acid (20:4 fatty acid). This decrease in unsaturated fatty acids at day 15 therefore demonstrates the effectiveness of the treatment.

[0177] 5 saturated fatty acids are identified between J0 and J15. All of these fatty acids are Excess products are produced after 2 weeks of treatment. In cases of seborrheic dermatitis, these lipids are consumed by Malassezia. After treatment, Malassezia is reduced, therefore its metabolism is also reduced, which explains this increase in saturated fatty acids on day 15.

[0178] Table 11 below describes all the saturated fatty acid molecules.

[0179] Table 11: List of overexpressed and underexpressed saturated fatty acid molecules expressed in a significant way with an FCm > 1.5.

[0180] [Tableauxll] FCm Nom 1.71 AG 14:0, myristic acid 1.66 AG 15:0 2.35 AG 16:0, palmitic acid 1.81 AG17:0, margaric acid 1.57 AG 18:0, stearic acid

[0181] Two oxylipins are identified between JO and J15. Oxylipins are a family of oxygenated natural products formed from fatty acids, particularly polyunsaturated fatty acids. Oxylipins are produced by organisms such as plants, animals, and fungi. These lipids allow these species to communicate with their host, reducing the host's inflammatory response and thus increasing their virulence.

[0182] The two oxylipins identified are 13-HODE (FCm: -1.58), which participates in maintaining keratinocyte proliferation and the release of inflammatory cytokines, and 13-HOTE (FCm: -1.73), which is thought to play a role in activating the inflammatory response. The oxylipins identified in this study decreased after treatment, in correlation with a decrease in Malassezia, the inflammatory state, and keratinocyte hyperproliferation.

[0183] A ceride is identified between JO and J15. Cerides are markers of sebum since these lipids are found almost exclusively in this matrix. The molecule is WE 37:0 with an FCm of -1.62. Glycerolipids

[0184] At the end of these two weeks of treatment, a very large number of glycerolipids are overproduced. In total, 93 glycerolipids are overproduced, including 13 monoglycerols, 43 diacylglycerols, and 37 triacylglycerols. This increase in glycerolipids, which can be very high for some (FCm up to 10), is explained by the reduced lipase activity of Malassezia, as the treatment leads to a substantial reduction in the amount of Malassezia via the antifungal agents. Sphingolipids

[0185] During these 2 weeks of treatment, 5 sphingolipids were identified by fragmentation. The 5 molecules are listed below. A decrease in two ceramides and two acylceramides, as well as an increase in one acylceramide, were observed. These changes are consistent with the reduction in certain symptoms of the pathology between day 0 and day 15. In fact, a reduction in the hyperproliferation and desquamation in which these molecules are involved was observed.

[0186] Table 12: List of sphingolipid molecules significantly overexpressed and underexpressed with an FCm >1.5

[0187] [Tables 12] FCm Name Lipid Category Main Class Subclass 2,34 Acer 51:0; 04 Sphingolipids Ceramides Acylceramides -1,52 Cer54:l ; 04 [AH ] Sphingolipids Ceramides N-acylsphingosine -2,54 Acer 58:2 ; 02 Sphingolipids Ceramides Acylceramides -1.73 Cer50:l;O3 : Cer( 24:l;O3 / 26:0) Sphingolipids Ceramides N-acylsphingosine -1.63 ACer60:l;O3 Sphingolipids Ceramides Acylceramides

[0188] There remain 4 molecules which have been identified by fragmentation and which are urocanate, indolelactate, pyroglutamic acid and Thistamine.

[0189] Urocanat is a metabolite of the histamine synthesis cascade, which is a marker molecule of pruritus. Between day 0 and day 15, a decrease in urocanat was observed (FCm = -1.61), which correlated with a decrease in the amount of Malassezia and a decrease in other pruritus markers such as cathepsin. In this study, histamine was also found to be underexpressed after 2 weeks of treatment (FCm = -2.50). Histamine, like its metabolite mentioned above, is also a marker of pruritus.

[0190] In this study, the inventors observed a decrease, sometimes very significant (FCm between -1.5 and -3.7), in 22 unsaturated fatty acids, as well as an increase, also sometimes very significant (FCm between 1.5 and 10.1), in 93 glycerolipids. These results were confirmed by fragmentation analysis, but a decrease in 12 unsaturated fatty acids and an increase in 19 glycerolipids identified from a database were also observed. This could be interpreted as a reduction in lipase activity in the skin. These results are consistent with previous studies that have revealed increased levels of unsaturated fatty acids in patients with seborrheic dermatitis compared to healthy subjects due to the lipase activity of Malassezia (Gordon et al., 2013 Int. J. Cosmet Sci. 35, 169-175).

[0191] Thus, the SpiderMass measurement makes it possible to monitor enzymatic activity, in particular caused by dysbiosis of the microbiota.

[0192] The association between seborrheic dermatitis and increased levels of unsaturated free fatty acids is well understood. In seborrheic dermatitis, lipase activity is increased. Lipases break down glycerolipids such as triglycerides or diglycerides in sebum are free unsaturated fatty acids, which can be irritating to the skin and contribute to inflammation.

[0193] Most of the sphingolipid groups identified in this study were significantly reduced. Between day 0 and day 15, a general decrease in sphingolipids (ceramides and acylceramides) was observed. This decrease can be correlated with the decrease in desquamation observed during the same period.

[0194] A large proportion of the sphingolipids identified by the database are 1-O-acylceramide type acylceramides. This family was recently discovered in the human epidermis, particularly in the stratum comeum (Rabionet et al., 2013, J. Lipid Res. 54, 3312-3321). These molecules have an epidermal origin, specifically from maturing keratinocytes. Indeed, although the role of these ceramides in the skin barrier effect is not yet fully understood, one study showed a continuous increase in 1-O-acylceramide ceramides during keratinocyte maturation, indicating preferential synthesis during keratinocyte differentiation (Rabionet et al., 2022, Lipids 57, 183-195). However, subjects with seborrheic dermatitis have keratolytic hyperproliferation, causing desquamation.

[0195] In conclusion, during this study, the inventors observed a significant change in the molecular profile of the skin thanks to the SpiderMass system in just two weeks of daily treatment with Kelual DS shampoo.

[0196] These modifications affect several families of molecules, particularly glycerolipids, which tend to return to a healthy profile since they are less consumed by the Malassezia yeast, which is found in much lower quantities after treatment. Indeed, as the amount of Malassezia decreases after two weeks of treatment, lipase activity is also reduced.

[0197] The epidermal barrier regains a healthier profile due to a decrease in unsaturated free fatty acids and sphingolipids and an increase in glycerolipids.

[0198] This decrease in free fatty acids and sphingolipids is correlated with the clinical parameters observed during this same period, a very significant decrease between J0 and J15 in clinical scores, irritative state and erythema (p<0.0001 for both scores).

[0199] The increase in glycerolipids and the decrease in amino acids and their derivatives after two weeks of daily treatment are correlated with a decrease in the amount of Malassezia and therefore in their lipase and protease activity.

[0200] Thus, after 2 weeks of treatment consisting of daily application of an antifungal shampoo, an intense modification of the molecular profiles of subjects is observed with a strong correlation with other clinical and biometrological parameters.

[0201] The inventors thus clearly demonstrate that this SpiderMass system, using real-time mass spectrometry, makes it possible to characterize molecular profiles within the epidermis itself. This system is sensitive enough to detect significant differences in molecular profiles in cases of inflammatory skin dermatoses. It also makes it possible to demonstrate improvement in an inflammatory dermatosis following treatment by measuring these molecular profiles. It is capable of characterizing molecules from very different chemical families, from small polar molecules to large nonpolar molecules.

[0202] This SpiderMass system is therefore highly versatile and of great interest for dermatological applications, due to the system's ability to perform direct in vivo analysis of human skin. Indeed, the instrument allows for in situ characterization without the need for biopsy or sample preparation, and with a very limited invasiveness thanks to a completely painless micro-sampling procedure.

Claims

Demands

1. Method for evaluating the efficacy of an active ingredient or cosmetic or dermatological formulation for treating and / or preventing an inflammatory dermatosis, the method comprising: a) the application of the tested active ingredient or cosmetic or dermatological formulation to a skin sample; b) the determination of the molecular signature of the treated skin sample by real-time mass spectrometry; and c) the evaluation of the efficacy of said active ingredient or cosmetic or dermatological formulation for preventing and / or improving at least one effect of an inflammatory dermatosis based on the molecular signature of step b), said molecular signature comprising a metabolite selected from dipeptides, amino acids and their analogues, imidazoles, indoles, amines, carbonyls, free fatty acids and their conjugates; prostaglandins; fatty aldehydes; fatty esters; cerides; squalene; glycerolipids;sphingolipids, oxylipins and cholesterol and / or cholesterol esters;

2. The method of any one of claim 1, wherein the determination in step b) comprises measuring the expression level of the metabolite from the skin sample in step a) by real-time mass spectrometry.

3. The method of claim 2, wherein step c) comprises comparing the level of expression of step b) with a reference level of expression.

4. The method of claim 3, wherein the reference expression level is the expression level of the metabolite in the skin sample prior to application of the active ingredient or cosmetic or dermatological formulation.

5. The method of any one of claims 1 to 4, wherein the real-time mass spectrometry is the SpiderMass technology.

6. The method of any one of claims 1 to 5, wherein the inflammatory dermatosis is selected from psoriasis, atopic dermatitis, eczema, acne, rosacea, lichen planus, prurigo, and seborrheic dermatitis.