Compositions and methods for improving skin appearance

Abstract

To provide injectable compositions and methods of treating skin to improve hydration, elasticity and / or texture.SOLUTION: The problem is solved by compositions based on crosslinked hyaluronic acid matrices made with low molecular weight hyaluronic acids.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention generally relates to injectable compositions, and more particularly to hyaluronic acid-based compositions for treating skin wrinkles.

Background Art

[0002] Current injectable treatment options for improving the quality of the skin of the entire face or other major skin surface areas require multiple treatment sessions (typically 3 to 4 treatments every 3 to 4 weeks) and have a relatively short duration of effect. The skin is composed of the epidermis and the dermis. The outermost epidermis consists of stratified squamous epithelium with a basement membrane in the lower layer. It contains no blood vessels and is nourished by diffusion from the dermis. The main cell type that makes up the epidermis is keratinocytes, and melanocytes and Langerhans cells also exist. This layer of the skin plays a role in retaining moisture in the body and preventing the entry of harmful chemicals and pathogens. The dermis is located beneath the epidermis and contains numerous structures such as blood vessels, nerves, hair follicles, smooth muscles, glands, and lymphatic tissues. The dermis (dermis or corium) is typically 3 to 5 mm thick and is a major component of human skin. It is composed of a reticular structure of connective tissue, mainly collagen fibrils that provide support and elastic tissue that provides flexibility. The main cell types are fibroblasts, adipocytes (fat storage depots), and macrophages. Hyaluronic acid (HA) is part of the dermal composition and is a major component of the extracellular matrix.

[0003] Facial aging occurs as a result of several factors, including intrinsic changes within the skin, the effects of gravity, facial muscles (muscle lines) acting on the skin, loss or movement of soft tissues, and bone loss, as well as loss of tissue elasticity. As the epidermis begins to thin, the skin ages and the junction with the dermis becomes flat. Collagen decreases as a person ages, the bundles of collagen that give skin turgor loosen and lose strength. As the skin loses elasticity, its resistance to stretching decreases. Together with gravity, muscle pull, and tissue changes, the skin can begin to wrinkle. Water loss and disruption of cell - to - cell connections also reduce the skin's barrier function, which can increase the size of the skin's pores. It is well known that the eyes are often the first facial feature to show signs of aging. Since the skin around the eyes is thinner, skin changes occur earlier around the eyes than in the rest of the face. The skin here has fewer glands and is constantly exposed to the movements of blinking, squinting, rubbing, and turning the eyes. As the cheeks begin to sag, the mid - face ages and nasolabial folds form. The nasolabial fold is a line running from the side of the nose to the corner of the mouth. In the lower - face region, as the face ages, the facial tissues descend. As a result, so - called "laugh lines" occur. These and other creases and wrinkles are generally treated by subcutaneous and dermal injection of cosmetic facial fillers that give volume to the skin lost, thereby reducing the appearance of the creases and wrinkles.

[0004] Hyaluronic acid (HA), also known as hyaluronan, is one of the most commonly used skin filler components currently. Hyaluronic acid is a naturally occurring water - soluble polysaccharide, specifically a glycosaminoglycan, which is a major component of the extracellular matrix and is widely distributed in animal tissues. Since hyaluronic acid has the same structure in all species and tissues, this polysaccharide is an ideal substance for use as a biomaterial in health and medicine. HA has excellent biocompatibility and, unlike collagen, does not require any skin tests prior to implantation. Furthermore, HA has the ability to bind large amounts of water, making it an excellent soft - tissue volumizer. To increase its lifespan in vivo, the HA of the dermal filler is generally cross-linked. Chemically cross-linked HA is formed by reacting uncross-linked HA with a cross-linking agent under appropriate reaction conditions.

[0005] It is generally recognized that high-viscosity HA-based dermal fillers, such as those highly cross-linked and / or composed of high-molecular-weight HA and / or having a high HA concentration, tend to persist longer in the body. Conversely, low-viscosity HA-based dermal fillers, such as those more lightly cross-linked and / or composed of low-molecular-weight HA and / or having a low HA concentration, may have a shorter duration of persistence in the body. Naturally, injecting a high-viscosity material with a needle is relatively more difficult and generally requires a lower-gauge needle (e.g., 21G or 23G compared to 27G or 30G) than injecting a relatively low-viscosity material. It has been demonstrated that it is difficult to develop an HA-based composition that is easy to inject with a high-gauge needle (i.e., a thin needle) and has a long duration of persistence in the body.

Summary of the Invention

Means for Solving the Problems

[0006] The present invention relates to an injectable composition, and more particularly to an injectable composition for intradermal injection into the skin. The compositions and methods provide an improved skin appearance and quality by filling superficial skin depressions and / or improving the texture and appearance of the skin. In one aspect, the compositions and methods provide at least one of an improved skin texture, increased skin hydration, and increased elasticity. In one aspect, the composition is based on hyaluronic acid (HA) and a pharmaceutically acceptable salt of HA, such as sodium hyaluronate (NaHA). Many of the long-lasting and highly injectable compositions of the present invention contain a cross-linked HA matrix made with relatively low molecular weight HA. In some embodiments, the composition has a relatively low concentration of HA. Advantageously, many of the compositions provided herein have a longer duration of action. For example, rather than requiring multiple treatments to be repeated every 3 to 4 weeks as is common with conventional intradermal injection procedures, many of the compositions and methods provided herein have a duration of action of 3 months, 4 months, 6 months to 1 year, or more.

[0007] In a broad aspect of the invention, generally, a composition is provided that contains a low molecular weight HA material or consists essentially of a low molecular weight HA material and comprises an HA gel. The HA component comprises more than 50% by weight, such as at least 70% by weight, such as about 90% by weight, of low molecular weight HA. The low molecular weight HA material has a weight average molecular weight of from about 0.20 MDa to about 0.99 MDa or less, such as from about 0.4 MDa to about 0.8 MDa. In some embodiments, the HA gel may further contain a high molecular weight HA, i.e., an HA material having a molecular weight of at least about 1.0 MDa to about 4.0 MDa. Generally, in embodiments of the invention that include a high molecular weight HA material, the weight average molecular weight of the high molecular weight HA material is at least twice the weight average molecular weight of the low molecular weight HA material.

[0008] The HA of the HA gel may be cross-linked. For example, the HA may be chemically cross-linked with a suitable cross-linking agent. In some embodiments, the cross-linking agent is selected from the group consisting of 1,4-butanediol diglycidyl ether (BDDE), or 1,4-bis(2,3-epoxypropoxy)butane, or 1,4-bis(glycidyloxy)butane (all of which are commonly known as BDDE), 1,2-bis(2,3-epoxypropoxy)ethylene, and 1-(2,3-epoxypropyl)-2,3-epoxycyclohexane. In some embodiments, the composition has an HA concentration of from about 10.0 mg / g to a maximum of about 17.0 mg / g. In some embodiments, the HA concentration is less than about 17.0 mg / g, such as less than about 15.0 mg / g. In some embodiments, the HA concentration is between about 10.0 mg / g and about 14.0 mg / g. In some embodiments, the HA concentration is about 10.0 mg / g, about 11.0 mg / g, about 12.0 mg / g, about 13.0 mg / g, or about 14.0 mg / g.

[0009] In another aspect of the invention, a method of treating the skin with the present composition is provided. For example, a method of improving one or more qualities of the skin, or improving the appearance or texture of the skin is provided. In one aspect, a method of treating skin dryness, texture or roughness, and / or elasticity is provided. The method generally includes treating a region of the skin by introducing a plurality of spaced injections of a composition comprising a crosslinked HA-containing hyaluronic acid (HA) gel into the region of the skin, and the treated skin maintains improved hydration, a smoother texture, or increased elasticity over a long-term duration of, for example, at least about 3 months to about 1 year, or more. In particularly advantageous embodiments, the introducing step is performed in only a single treatment session, thereby eliminating the need to repeat the treatment to maintain the duration of the effect. In some embodiments, the introducing step includes introducing the composition by injections spaced at intervals between about 2 mm and about 30 mm. For example, the introducing step includes introducing the composition by injections spaced at intervals between about 5 mm and about 20 mm, or between about 10 mm and about 15 mm. In some embodiments, the composition is introduced at an injection depth between about 500 μm and about 2000 μm, such as at a depth of about 1000 μm. In preferred embodiments, the composition is introduced at an injection depth between about 0.5 mm and about 5.0 mm, preferably between about 1.0 mm and about 4.0 mm, more preferably between about 1.5 mm and about 3.0 mm. Generally, deeper injections result in improved hydration. In another aspect, the present invention provides a method of treating skin roughness, comprising treating a region of the skin by introducing a plurality of spaced injections of a composition comprising a crosslinked hyaluronic acid (HA) gel into the region of the skin, wherein the treated skin maintains a smoother texture for at least about 3 months, at least about 4 months, at least about 6 months, or at least about 12 months as a result of the treatment.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010]

Figure 1

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DETAILED DESCRIPTION OF THE INVENTION

[0011] In the context of numerical values, the term “about” is readily understood by those skilled in the art and preferably means that a particular value can be modified by up to ±10%. With respect to the endpoints of a range, the modifier “about” preferably means that the lower endpoint can be decreased by up to 10% and the upper endpoint can be increased by up to 10%. Each numerical value or range disclosed in this application can be absolute, i.e., it is also contemplated that the modifier “about” can be removed. All numbers in this specification representing the “molecular weight” of HA are understood to represent the weight average molecular weight (Mw) in daltons. The molecular weight of HA is calculated from the measured intrinsic viscosity value using the following Mark Houwink relational equation: Intrinsic viscosity (m 3 / kg) = 9.78×10 -5 ×Mw 0.690 is used.

[0012] The intrinsic viscosity is measured according to the procedure specified in the European Pharmacopoeia (HA Monograph N°1472, 01 / 2009). The high molecular weight HA used in this specification represents a HA material having a molecular weight of at least about 1 million (1.0 million) Daltons (Mw≥10 6 Da or 1 MDa) to about 5.0 MDa. For example, the high molecular weight HA in the present composition may have a molecular weight in the range of about 1.5 MDa to about 3.0 MDa, or the high molecular weight HA may have a mass average molecular weight of about 2.0 MDa. In another example, the high molecular weight HA may have a molecular weight of about 3.0 MDa. In another example, the high molecular weight HA has an intrinsic viscosity of 1.35 m 3 / kg corresponding to about 1 MDa, 1.5 MDa (1.35 m 3 / kg), 2 MDa (2.18 m 3 / kg), 3 MDa (2.88 m 3 / kg), 5 MDa (4.10 m 3 / kg), 0.2 MDa (0.44 m 3 / kg), 0.4 MDa (0.72 m 3 / kg), 0.8 MDa (1.1 m 3 / kg), 0.99 MDa (1.34 m 3 / kg) when calculated according to the above - shown Mark Houwink relational equation.

[0013] As used herein, low molecular weight HA refers to HA materials having a molecular weight of less than about 1.0 MDa. Low molecular weight HA can have a molecular weight from about 200,000 Da (0.2 MDa) to less than 1.0 MDa, such as from about 400,000 Da to about 800,000 Da, such as from about 386,000 Da (0.386 MDa) to about 740,000 Da (0.74 MDa). In some embodiments, the low molecular weight HA used to produce the crosslinked HA matrix is 0.99 MDa or less. Preferably, the mixture of low molecular weight HA and high molecular weight HA has a bimodal molecular weight distribution. The mixture may also have a multi-modal molecular weight distribution.

[0014] In one aspect of the invention, the composition comprises HA having a high molecular weight component and a low molecular weight component, wherein the high molecular weight component has a mass average molecular weight that is at least twice the mass average molecular weight of the low molecular weight component. For example, a composition according to this aspect of the invention can comprise a low molecular weight component having a mass average molecular weight of about 500,000 Da and a high molecular weight component having a mass average molecular weight of about 1.0 MDa or at least about 1.0 MDa. In another example, a composition according to the invention can comprise a low molecular weight component having a mass average molecular weight of about 800,000 Da and a high molecular weight component having a mass average molecular weight of about 1.6 MDa or at least about 1.6 MDa. The degree of crosslinking is measured by the final mass ratio of the crosslinking agent to the HA disaccharide unit.

[0015] As used herein, uncrosslinked HA refers to individual HA polymer molecules that are not crosslinked to each other. Uncrosslinked HA generally remains water-soluble. In this specification, there is provided a composition for treating the skin, for example, an injectable composition that can be introduced intradermally to improve the appearance or quality of the skin, for example, to improve hydration, texture, and / or elasticity. The composition may also be effective in treating skin wrinkles and reducing superficial cutaneous depressions. Also provided are methods for manufacturing these compositions and methods for treating using these compositions. The composition is based on hyaluronic acid (HA) and a pharmaceutically acceptable salt of HA, such as sodium hyaluronate (NaHA). As used herein, hyaluronic acid (HA) can refer to any hyaluronate salt thereof, including but not limited to sodium hyaluronate (NaHA), potassium hyaluronate, magnesium hyaluronate, calcium hyaluronate, and combinations thereof. Any of HA and its pharmaceutically acceptable salts can be used in the present invention.

[0016] Generally, the concentration of HA in some of the present compositions is from about 10.0 mg / g to a maximum of about 17.0 mg / g. In some embodiments, the HA concentration is less than about 17.0 mg / g, such as less than about 15.0 mg / g. In some embodiments, the HA concentration is from about 10.0 mg / g to about 14.0 mg / g. In some embodiments, the HA concentration is about 10.0 mg / g, about 11.0 mg / g, about 12.0 mg / g, about 13.0 mg / g, or about 14.0 mg / g. Some of the compositions of the present invention include additional agents, such as an anesthetic in an amount effective to relieve pain experienced upon injection of the composition. The anesthetic can be selected from the group consisting of ambucaine, amolanone, amylocaine, benoxinate, benzocaine, betoxycaine, bifenamine, bupivacaine, butacaine, butamben, butanilicaine, butetamine, butoxycaine, carticaine, chloroprocaine, cocaethylene, cocaine, cyclomethycaine, dibucaine, dimethisoquin, dimethocaine, diphenone, dicyclomine, ecgonidine, ecgonine, ethyl chloride, etidocaine, beta-eucaine, eufl procaine, phenacolin, formocaine, hexylcaine, hydroxytetracaine, isobutyl p-aminobenzoate, leucinocaine mesylate, levoxadrol, lidocaine, mepivacaine, meprilocaine, metabutoxycaine, methyl chloride, myrtecaine, naepaine, octocaine, orthocaine, oxethazaine, parethoxycaine, phenacaine, phenol, piperocaine, pyridocaine, polidocanol, pramoxine, prilocaine, procaine, propanocaine, propalacaine, propipocaine, propoxycaine, pseudococaine, pyroocaine, ropivacaine, salicyl alcohol, tetracaine, tricaine, trimecaine, zolamine, and salts thereof. In one embodiment, at least one anesthetic is lidocaine, for example in the form of lidocaine HCl. The compositions described herein can have a lidocaine concentration of from about 0.1% to about 5% by weight of the composition, such as from about 0.2% to about 1.0% by weight of the composition. In one embodiment, the composition has a lidocaine concentration of about 0.3% (w / w%) of the composition.

[0017] In some embodiments, the composition further comprises a beneficial additive, such as an antioxidant. In some embodiments, the composition comprises, for example, mannitol. Mannitol may be present in an amount from about 0.1% to about 2.0% by weight, or from about 0.3% to about 0.9% by weight. In some embodiments, mannitol is present in an amount less than about 1.0% by weight, about 1.0% by weight or less, or about 1.0% by weight. In some embodiments, mannitol is present in an amount of about 0.9% by weight. In other embodiments, mannitol is present in an amount of about 0.1% by weight, or about 0.2% by weight, or about 0.3% by weight, or about 0.4% by weight, or about 0.5% by weight, or about 0.6% by weight, or about 0.7% by weight, or about 0.8% by weight, or about 0.9% by weight, or about 1.0% by weight. In other embodiments, mannitol is present in an amount greater than about 1.0% by weight. In some embodiments, mannitol is present in an amount from about 1.0% to about 5.0% by weight.

[0018] In some embodiments, the composition further comprises a vitamin, such as vitamin C. In a more preferred embodiment, the vitamin is a derivative or stabilized form of vitamin C, such as ascorbic acid 2-glucoside. The vitamin may be present in an amount from about 0.1% to about 2.0% by weight, or from about 0.2% to about 1.0% by weight, or from about 0.3% to about 0.6% by weight. In some embodiments, vitamin C is present in an amount of about 0.6% by weight. In other embodiments, the vitamin C derivative is present in an amount of about 0.1% by weight, or about 0.2% by weight, or about 0.3% by weight, or about 0.4% by weight, or about 0.5% by weight, or about 0.6% by weight, or about 0.7% by weight, or about 0.8% by weight, or about 0.9% by weight, or about 1.0% by weight. In other embodiments, the vitamin C derivative is present in an amount greater than 1.0%. In some embodiments, the vitamin C derivative is present in an amount from about 1.0% to about 5.0% by weight.

[0019] In some embodiments, the composition further comprises a combination of mannitol and ascorbic acid 2-glucoside. In some of these embodiments, mannitol is present in an amount of 1.0 wt% or less, such as 0.9 wt%, and ascorbic acid 2-glucoside is present in an amount of about 0.6 wt%.

[0020] In some embodiments, the composition does not contain an antioxidant or a vitamin. For example, in some embodiments, the composition comprises or consists essentially of cross-linked hyaluronic acid and water cross-linked with a cross-linking agent. These compositions may or may not contain an anesthetic such as lidocaine.

[0021] The product and the composition are preferably provided in a sterile form. The composition can be sterilized using conventional methods, such as an autoclave. For example, the composition can be sterilized by exposing the composition to a temperature of at least about 120°C to about 130°C and / or a pressure of at least about 12 pounds per square inch (PSI) to about 20 PSI for at least about 1 minute to about 15 minutes. The method for manufacturing the composition includes the step of providing a raw material HA material in the form of dry HA fibers or powder. The raw material HA material may be HA, its salts, and / or mixtures thereof. In a preferred embodiment, the HA material includes fibers or powder of NaHA, for example, NaHA fibers derived from bacteria. In some aspects of the present specification, the HA material may be of animal origin. The HA material may be a combination of raw materials including HA and at least one other polysaccharide, such as glycosaminoglycan (GAG). In a broad aspect of the present invention, the HA material of the composition can include a cross-linked HA matrix made using from about 5% to about 95% low molecular weight HA and the remainder of the HA material containing high molecular weight HA.

[0022] In some embodiments of the present invention, the HA material used to produce the present composition is substantially entirely composed of or contains low molecular weight HA. In some embodiments, substantially 100% of the HA material used to produce the present composition can be low molecular weight HA as defined above. In other embodiments, the HA material used to produce the composition contains a combination of relatively high molecular weight HA and relatively low molecular weight HA as defined above. In certain embodiments, at least about 50% by weight, such as at least about 70% by weight, such as at least about 90% by weight or more of the HA material in the composition is low molecular weight HA as defined above, and the balance of the HA is high molecular weight HA. In one embodiment, the composition is produced using a 90:10 low molecular weight HA to high molecular weight HA ratio. That is, the compositions of these embodiments are produced using a combination of high molecular weight HA and low molecular weight HA in which about 90% by weight of the HA is low molecular weight HA.

[0023] In one embodiment, pure dry NaHA fibers are hydrated in an alkaline solution to produce an uncrosslinked NaHA gel. In this step, any suitable alkaline solution can be used to hydrate the NaHA, such as, but not limited to, aqueous solutions containing sodium hydroxide (NaOH), potassium hydroxide (KOH), sodium bicarbonate (NaHCO3), lithium hydroxide (LiOH), etc. In another embodiment, the suitable alkaline solution is an aqueous solution containing NaOH. The resulting alkaline gel will have a pH greater than 7.5. The resulting alkaline gel can have a pH greater than 9, or greater than 10, or greater than 11, or greater than 12, or greater than 13.

[0024] The next step in the manufacturing process involves crosslinking the hydrated alkaline NaHA gel with a suitable crosslinking agent. The crosslinking agent may be any agent known to be suitable for crosslinking polysaccharides and their derivatives via hydroxyl groups. Suitable crosslinking agents include, but are not limited to, 1,4-butanediol diglycidyl ether (or 1,4-bis(2,3-epoxypropoxy)butane or 1,4-bisglycidyloxybutane, all of which are commonly known as BDDE), 1,2-bis(2,3-epoxypropoxy)ethylene, and 1-(2,3-epoxypropyl)-2,3-epoxycyclohexane. The use of multiple crosslinking agents or different crosslinking agents is not excluded from the scope of the present disclosure. In one embodiment, the HA gel described herein is crosslinked using BDDE. The crosslinking step can be carried out using any technique known to those skilled in the art. Those skilled in the art understand how to optimize the crosslinking conditions according to the properties of HA and how to carry out crosslinking to an optimized extent.

[0025] In another embodiment, crosslinking of HA is achieved during hydration of the HA fibers by hydrating a combination of high molecular weight fibers and low molecular weight fibers in an alkaline solution containing a crosslinking agent, such as BDDE. The degree of crosslinking in the HA component of the composition is at least about 1% to a maximum of about 20% BDDE / HA, mass / mass (w / w), for example about 4% to about 12% by mass, for example about 10% by mass, for example about 8% by mass, for example about 6% by mass, for example about 5% by mass, for example about 4% by mass. The hydrated crosslinked HA gel may be swollen to a desired HA concentration. This step can be achieved, for example, by neutralizing the crosslinked hydrated HA gel by adding an aqueous solution containing an acid such as HCl. The gel is then swollen in phosphate buffered saline (PBS) solution.

[0026] The gel may be purified by conventional techniques such as dialysis against phosphate buffer or alcohol precipitation to recover the cross-linked material, stabilize the pH of the material, and remove any unreacted cross-linking agent. The composition is mixed to be homogeneous. Preferably, the homogenization step includes mixing, stirring, or pulping the gel with controlled shear force to obtain a substantially homogeneous mixture. In some embodiments, phosphate buffer is added during or after mixing to bring the HA in the final composition to the desired concentration.

[0027] In some embodiments, lidocaine or another suitable anesthetic (e.g., in the form of lidocaine HCl) is added to the composition. For example, the pH of the purified substantially neutral pH gel is adjusted so that the gel becomes slightly alkaline, such that the pH of the gel exceeds about 7.2, for example, about 7.5 to about 8.0. Alternatively, the gel is adjusted to be alkaline such that the pH of the gel exceeds about 9, for example, about 10.0 to about 11.0. This step can be accomplished by adding any suitable means, such as dilute NaOH, KOH, NaHCO3 or LiOH, or any other alkaline molecule, solution and / or buffered composition known to those skilled in the art, to the gel in an appropriate amount. For example, in some embodiments, lidocaine HCl is provided in powder form and solubilized using water for injection (WFI). The lidocaine is then added to the (slightly) alkaline gel. Then, optionally, uncrosslinked HA may be added to the lidocaine-containing gel. For example, in one embodiment, the desired HA concentration is about 12.0 mg / g. The composition containing lidocaine may have a lidocaine concentration of from about 0.1% to about 5% by weight of the composition, for example, about 0.3% by weight (or w / w) based on the total weight of the composition. The composition containing uncrosslinked HA may have an uncrosslinked HA concentration of less than 10% or less than 5% by weight of the composition, for example, preferably from about 0.5% to about 1.5% by weight, for example, about 0.9 to 1.0% based on the total weight of the composition. The uncrosslinked HA preferably has a high molecular weight.

[0028] The composition is introduced into a delivery device, such as a syringe. Syringes useful herein include any syringe known in the art capable of delivering a viscous dermal filler composition. The syringe can have an internal volume of from about 0.4 mL to about 3 mL, from about 0.5 mL to about 1.5 mL, or from about 0.8 mL to about 1.0 mL. In other embodiments, the composition is introduced into an infusion device suitable for delivering the composition to a relatively superficial surface of the skin using multiple microdepot injections. Gauges of needles used to deliver the present composition include gauges from about 18G to about 40G. In some embodiments, the needle for delivering the composition is from about 25G to about 33G, such as from about 31G to about 33G or from about 32G to about 33G. In some embodiments, the composition is delivered using a needle having a gauge of 28G, 29G, 30G, 32G, or 33G.

[0029] In another aspect of the invention, a method of treating skin using the present composition is provided. For example, a method of improving one or more qualities of the skin, or improving the appearance or texture of the skin is provided. In one aspect, a method of treating skin dryness, texture or roughness, and / or elasticity is provided. The method generally comprises treating a region of the skin by introducing a plurality of spaced injections of a composition comprising a crosslinked hyaluronic acid (HA) gel into the region of the skin, wherein the treated skin maintains improved hydration, a smoother texture, or increased elasticity over a long-term duration, such as, for example, from at least about 3 months to about 1 year, or longer, as a result of the treatment. In a particularly advantageous embodiment, the introducing step is performed in only a single treatment session, thereby eliminating the need to repeat the treatment to maintain the duration of the effect. In one aspect of the invention, a method of treating skin is provided that includes introducing the composition into the skin during a treatment session that includes a plurality of injections of the composition into a skin region. In one embodiment, a treatment session includes a patient visiting a practitioner once. During the treatment session, a plurality of injections can be administered to the skin, for example, a specific skin area.

[0030] The plurality of injections in a single treatment session can include, for example, 2 to about 500 injections, about 50 to about 200 injections. In some embodiments, the treatment session includes, for example, at least 2 injections, at least 10 injections, at least 20 injections, at least 40 injections, at least 60 injections, at least 80 injections, at least 100 injections, at least 140 injections, at least 180 injections, at least 200 injections, at least 300 injections, at least 400 injections, at least 500 injections, or more to the skin area. In some embodiments, the time required for a treatment session is about 45 minutes or less, about 30 minutes or less, about 15 minutes or less, or about 10 minutes or less per treatment area. The treatment area is defined as the skin area treated with the present composition and the present method. The treatment area may include or consist of at least one skin area of the face, neck, or décolletage. The treatment area may also be an area of skin other than the face, neck, or décolletage, such as the back of the hand, knee, elbow, forearm, calf, thigh, back skin area, or any other area of skin that can be treated using the present composition and method and thereby benefit or be improved.

[0031] In some embodiments, the introducing step includes introducing the composition by injections spaced at intervals from about 2 mm to about 30 mm. For example, the introducing step includes introducing the composition by injections spaced at intervals from about 5 mm to about 20 mm. In some embodiments, the introducing step includes introducing the composition by injections spaced at intervals from about 10 mm to about 15 mm.

[0032] In some embodiments, the injection is provided at a very shallow depth in the skin. For example, in some embodiments, the composition is introduced to a depth of about 2000 μm or less. For example, the injection can be provided at a depth of about 500 μm to about 2000 μm, about 800 μm to about 1600 μm, or about 1000 μm to about 1200 μm. In preferred embodiments, the composition is introduced at an injection depth of about 0.5 mm to about 5.0 mm, preferably about 1.0 mm to about 4.0 mm, more preferably about 1.5 mm to about 3.0 mm. In one embodiment, the injection is introduced in an amount of about 1 μL to about 200 μL per injection, such as about 5 μL to about 100 μL, for example about 20 μL to about 80 μL per injection, such as about 40 μL to about 60 μL. In some embodiments, the injection is introduced in an amount of about 5 μL to about 500 μL per injection, about 10 μL to about 400 μL per injection, about 50 μL to about 200 μL, or about 100 μL per injection.

[0033] In some embodiments, the injection is delivered through a needle having a gauge of at least 27G, such as 28G, 30G, or 32G. Conveniently, the treatment method can include or consist of a single treatment session that lasts for a relatively short time. In some embodiments, the treatment session covering the skin area to be treated includes multiple intradermal injections into the skin area, and the time required for the treatment session is about 45 minutes or less. In some embodiments, the time required for the treatment session is about 30 minutes or less. In still other embodiments, the time required for the treatment session is about 20 minutes or less, or about 15 minutes or less, or about 10 minutes or less.

[0034] Also provided is a method for treating rough skin, the method including treating the area by introducing a composition containing a crosslinked HA hyaluronic acid (HA) gel into the skin area by a plurality of spaced injections, and the treated skin maintains a smoother texture for at least about 3 months, at least about 4 months, at least about 6 months, at least about 9 months, or at least about 12 months by the treatment.

[0035] In certain embodiments, the composition of the present invention comprises a sterile physiological solution of a non-animal-derived hyaluronic acid (HA) gel crosslinked with 1,4-butanediol diglycidyl ether (BDDE) at a concentration of 12 mg / ml. The composition is useful for treating superficial skin depressions as measured by improvement in skin texture compared to untreated superficial skin depressions, as well as improvement in skin quality such as smoothness, hydration, and elasticity. In certain embodiments, the treatment method includes intradermal injection using a 32G needle across the target anatomical area, such as depot injection. Target anatomical areas include the facial skin area and the neck skin area. Improvement in skin appearance, such as reduction in depressions, fine lines, and the appearance of an uneven or rough texture compared to untreated skin, can be significantly prominent for patients, and improvement can persist for a duration of at least 4 months, 6 months, 9 months, or 12 months after a single treatment session of as little as 45 minutes, or as little as 30 minutes, or as little as 20 minutes, or as little as 15 minutes, or less. Improvement in skin texture can be evaluated using appropriate metrics. Skin quality measurements of hydration and elasticity can be performed using appropriate instruments and compared to a baseline, i.e., untreated skin. Other evaluation methods, such as FACE Q and GAIS, can be utilized to evaluate the satisfaction of the subject and the researcher, respectively. In certain embodiments, the duration of action of the product after treatment is at least about 4 months, such as about 6 months.

[0036] Adding lidocaine to the composition reduces pain in the treatment area in some embodiments. However, in some embodiments, the composition does not contain lidocaine to address patient needs regarding allergies to lidocaine and pain sensitivity. Another embodiment is a method of increasing at least one of smoothness, hydration, and elasticity in the skin, the method comprising introducing, in a single treatment session, a plurality of spaced injections of a composition comprising a hyaluronic acid (HA) gel containing BDDE-crosslinked HA and uncrosslinked HA into a skin region at a depth of from about 500 μm to about 5000 μm, the injections being introduced in an amount of from about 5 μL to about 100 μL per injection, the injections being delivered through a needle having a gauge of 28G to 33G, and the injections being spaced apart at intervals of from about 5 mm to about 20 mm. In some embodiments, the skin region maintains increased smoothness, hydration, and / or elasticity for at least about 3 months, about 4 months, about 5 months, about 6 months, 9 months, 12 months, or more as a result of the treatment. Another embodiment provides a composition for increasing at least one of smoothness, hydration, and elasticity of the skin, the composition comprising a hyaluronic acid (HA) gel comprising a crosslinked HA matrix made using a low molecular weight HA material having a mass average molecular weight of from about 400,000 Da to about 800,000 Da, the HA concentration of the composition being from about 10.0 mg / g to about 14.0 mg / g, the composition maintaining increased smoothness, hydration, and / or elasticity for at least about 6 months after being introduced into the skin in a single treatment session comprising injections of a plurality of spaced compositions, the injections being introduced in an amount of from about 5 μL to about 100 μL per injection, being delivered through a needle having a gauge of 28G to 33G, and being spaced apart at intervals of from about 5 mm to about 20 mm. The skin region may maintain increased smoothness, hydration, and / or elasticity for at least about 3 months, about 4 months, about 5 months, about 6 months, 9 months, 12 months, or more as a result of the treatment. The composition may further comprise at least one of mannitol and vitamin C. In some embodiments, both mannitol and a vitamin C derivative are present in the composition.

[0037] The composition is accompanied by a gel hardness G' of about 50 - 200 Pa, such as 100 - 150 Pa or 120 Pa when measured at 0.1 Hz, and about 100 - 300 Pa, such as 150 - 200 Pa or 175 Pa when measured at 5 Hz. Methods for measuring gel hardness are known in the art. Gel hardness is an indicator of the softness of a skin filler.

[0038] The composition is further accompanied by a gel viscosity G'' of about 10 - 100 Pa, such as 15 - 40 Pa or 20 Pa when measured at 0.1 Hz, and about 10 - 100 Pa, such as 20 - 40 Pa or 30 Pa when measured at 5 Hz. Methods for measuring viscosity are known in the art.

[0039] The composition is also accompanied by a compression ratio of about 5 - 20 N, such as 10 - 15 N or 12 N. Methods for measuring the compression ratio are known in the art. The compression ratio is an indicator of the deformation resistance of a skin filler. Generally, the lower the compression ratio, the lower the lift spreadibility of the filler, that is, the filler is more suitable for treating wrinkles and folds on the surface of the face or neck compared to fillers with a higher compression ratio that are more suitable for deeper injection and volume restoration.

Example

[0040] (Example 1) By a free radical decomposition test, the resistance of the gel sample to the decomposition of HA chains by free radicals (one of the main decomposition pathways of HA) can be evaluated. The free radical decomposition test was performed on three different batches of the present composition. The results obtained are shown in Table 1. It was found that all measured values were consistent (CVr < 10%).

Table 1

[0041] The variation between batches was about 3% for three different batches, and the average value of the decomposition time was 4985 seconds (Table 2).

Table 2

[0042] (Example 2) A 37-year-old female presents with rough, dry facial skin due to aging, dry climate, and / or lifetime exposure to sun / wind. The physician administers the composition described herein by intradermal, micro-depot injection. The treatment consists of 10 to about 100 superficial injections per skin area using a 32G / 4mm needle. The skin areas to be treated are the face, neck, and décolletage. The treatment session lasts about 40 minutes from the first injection to the last injection over all the patient's skin areas. An appropriate amount of the composition is administered by spaced injections to each treatment area. For example, in the facial area, about 2 mL to about 3 mL of the composition is administered by superficial single injections spaced at intervals of approximately about 10 mm to about 15 mm. The neck is treated with about 1 mL to 2 mL of the composition and the injections are spaced at intervals of approximately 15 mm to about 20 mm. After treatment, the treated skin areas are examined by visual, tactile, and pressure sensations. Photographic evaluations are performed at the start and end of treatment. The patient reports that the treatment caused minimal discomfort to the physician. The patient returns to daily activities immediately after treatment. Small areas of petechial hemorrhage are seen in the treated skin of the right hand, which resolve within a few days after application of an anti-inflammatory cream. The patient returns to the physician's office four months after treatment for follow-up evaluation. No further filler injections or mesotherapy treatments are performed on the patient prior to the follow-up evaluation visit. At the objective examination during the follow-up visit, the treatment has resulted in improvement in the texture of the epidermis, reduction in dryness, and improvement in skin brightness. These improvements are somewhat evident from photographic records. Gently palpating the treated skin areas, it appears that the hydration, softness, elasticity, and tone have improved. The patient expresses a high degree of satisfaction with the treatment by filling out a self-evaluation questionnaire. The patient claims that the treated areas have improved and is very satisfied with the results. Interestingly, these good results are achieved based on only a single treatment session and no repeated injections, "top-ups", or additional injection treatments are performed between the treatment session and the follow-up visit.

[0043] (Example 3) The degree of hydration of an injectable composition on the epidermal and dermal structures of human living skin explants was evaluated by corneometry measurement. That is, using a CM825 Corneometer (registered trademark) (COURAGE & KHAZAKA), the moisturizing level of the outermost skin layer of the stratum corneum was measured. The operating principle of the Corneometer (registered trademark) is based on the change in the capacitance of a detector designed in the form of a capacitor. On the surface of the measurement head in contact with the skin, its capacitance changes according to the moisturizing level of the skin. At D0 (= day 0), the electrical epidermal capacitance expressed in AU serves as an index of skin hydration. The following compositions according to the present disclosure were measured.

[0044]

Table 3

[0045] Preparation of explants: Nine explants were prepared in an abdominoplasty from a 45-year-old white female. The explants were kept alive in BEM medium (BIO-EC’s Explants Medium) at 37°C in a humidified, 5%-CO2 atmosphere. The explants were divided into 3 batches (Nb = number).

[0046]

Table 4

[0047] Product application: The explants of batch C1 used for corneometry were treated with 4 × 10 μL of the injectable product (square injection), with each injection point separated by 0.5 cm (see Figure 1). The explants of batch C2 used for corneometry were treated with 4 × 10 μL of the injectable product (square injection), with each injection point separated by 1 cm (see Figure 1). No treatment was given to the untreated control. Corneometry: For the explants at D0, D2, D7, and D9, the epidermal capacitance, which is an index of skin hydration, was evaluated using a CM825 Corneometer® (COURAGE & KHAZAKA). The measurement was performed at the center of the square explant using a 1-cm diameter probe. The measurement was taken 10 times, and the average value was calculated by the corneometer. Sampling: At D0, three explants from batch T0 were collected, cut into two parts, half were frozen at -80 °C, and half were fixed in formalin. At D2, D7, and D9, three explants were collected from each batch and processed in the same way.

[0048] Statistical analysis: Statistical analysis was performed according to the Student's t-test. The Student's t-test gives the probability "p" that two batches are significantly different. The difference between two batches is significant if p < 0.05 ( * ), and thus there is a 95% probability of a significant difference between the two batches, or significant if p < 0.01 ( ** ), and thus there is a 99% probability of a significant difference between the two batches.

[0049] Results: Corneometry measurements for each batch (see also Figures 2 and 3)

Table 5

[0050] By corneometry, for product Pcl, the corneometry values were higher at 44.0% at D2 ** vs. T, 34.9% at D7 ** vs. T, and 43.6% at D9 ** vs. T. For product Pc2, the corneometry values were higher at 30.7% at D2 * vs. T, 38.6% at D7 ** vs. T, and 41.9% at D9 ** vs. T. (According to the Student's t-test, * significant at p < 0.05 (95%);** p < 0.01 (significant at 99%). The compositions according to the present disclosure showed good hydration activity regardless of the conditions tested (four 10 μL injections at intervals of 0.5 cm or 1 cm each for Pc1 and Pc2 respectively), thereby inducing a strong increase in the epidermal capacitance value that increases skin hydration.

[0051] (Example 3) The skin hydration of the injectable compositions according to the present disclosure on the epidermal and dermal structures of human living skin explants was evaluated by additional corneometry measurements. The following compositions were measured.

Table 6

[0052] Preparation of explants: For the first donor, nine explants of size 1.5 cm × 2 cm were prepared from an abdominoplasty from a 59-year-old white female. For the second donor, nine explants of size 1.5 cm × 2 cm were prepared from an abdominoplasty from a 42-year-old white female. For the third donor, nine explants of size 1.5 cm × 2 cm were prepared from an abdominoplasty from a 52-year-old white female. For each donor, the nine explants were divided into three batches as follows.

[0053]

Table 7

[0054] Product application: At D0, 3 × 50 μL of product P1 or P2 was injected with a needle into the dermis of a rectangular explant (1.5 × 2 cm). The untreated control was not treated at all. The half volume (1 ml) of the medium was exchanged at D1, D2, D5, and D7. Corneometry: For the explants, the epidermal capacitance, which is an index of skin hydration, was evaluated using a CM825 Corneometer (registered trademark) (COURAGE&KHAZAKA) at D0, D1, D2, and D8.

[0055] Result: The results of the cornealometry measurements for three donors were presented as the average of three values (see also Figures 4 and 5).

Table 8

[0056] For three donors, cornealometry indicates that product P1 induces a 15% increase in cornealometry values compared to D0 at D1, continues to increase to 18% at D2, and increases to 22% at D8. Product P2 induces a rapid 37% increase from D0 to D1 and continues to increase to reach 49% from D2 to D8. According to these experimental conditions, and compared to the blank batch of D8 (TJ8), the following conclusions can be drawn.

[0057]

Table 9

[0058] Generally, under the experimental conditions of this test, these results indicate that the product (P2) according to the present disclosure shows an increase in skin hydration in the stratum corneum on the 8th day (D8) compared to product P1 and the untreated control T. The present invention has been described and illustrated with some degree of particularity, but the present disclosure has been made only by way of example, and it is understood that those skilled in the art can make numerous changes with respect to the combination and arrangement of parts, steps, and elements without departing from the scope of the invention claimed below.

[0059] The present invention can be further described by the following embodiments. 1. An injectable composition useful for reducing the appearance of superficial depressions of the skin, the composition comprising a hyaluronic acid (HA) gel comprising a crosslinked HA matrix made using a low molecular weight HA material having a mass average molecular weight of from about 0.20 MDa to about 0.99 MDa The HA concentration of the composition is less than about 17.0 mg / g, and the composition is an injectable composition that maintains an appearance with reduced superficial depressions of the skin for at least about 3 months after being introduced into the skin. 2. The composition according to item 1, wherein the composition maintains an appearance with reduced superficial depressions of the skin for at least about 6 months after being introduced into the skin. 3. The composition according to item 1, wherein the composition maintains an appearance with reduced superficial depressions of the skin for at least about 9 months after being introduced into the skin. 4. The composition according to item 1, further comprising at least one of mannitol and a vitamin C derivative. 5. The composition according to item 4, wherein mannitol is present in an amount of about 0.3% by mass to about 0.9% by mass. 6. The composition according to item 4, wherein the vitamin C derivative is ascorbic acid 2-glucoside. 7. The composition according to item 6, wherein ascorbic acid 2-glucoside is present in an amount of about 0.3% by mass to about 0.6% by mass. 8. The composition according to item 1, further comprising about 0.9% by mass of mannitol and about 0.6% by mass of ascorbic acid 2-glucoside. 9. The composition according to item 1, wherein the mass average molecular weight of the low molecular weight HA material is about 400,000 Da to about 800,000 Da. 10. The composition according to item 1, wherein the crosslinked HA matrix is crosslinked with a crosslinking agent selected from the group consisting of 1,4-butanediol diglycidyl ether (BDDE), 1,4-bis(2,3-epoxypropoxy)butane, 1,4-bisglycidyloxybutane, 1,2-bis(2,3-epoxypropoxy)ethylene, and 1-(2,3-epoxypropyl)-2,3-epoxycyclohexane.

[0060] 11. The composition according to item 1, wherein the HA concentration is about 10.0 mg / g to about 14.0 mg / g. 12. The composition according to item 1, wherein the HA concentration is about 12.0 mg / g. 13. An injectable composition useful for reducing the appearance of superficial depressions of the skin or improving the quality of the skin, the composition comprising A hyaluronic acid (HA) gel containing a crosslinked HA matrix, at least one of mannitol and a vitamin C derivative and comprising, the HA concentration of the composition is less than about 17.0 mg / g, the composition is an injectable composition that maintains an appearance with reduced superficial depressions of the skin or improved skin quality for at least about 3 months after being introduced into the skin. 14. The composition according to item 13, wherein the composition maintains an appearance with reduced superficial depressions of the skin or improved skin quality for at least about 6 months after being introduced into the skin. 15. The composition according to item 13, wherein the composition maintains an appearance with reduced superficial depressions of the skin or improved skin quality for at least about 9 months after being introduced into the skin. 16. The composition according to item 13, wherein mannitol is present in an amount of about 0.3% to about 0.9% by mass. 17. The composition according to item 13, wherein the vitamin C derivative is ascorbic acid 2-glucoside. 18. The composition according to item 17, wherein ascorbic acid 2-glucoside is present in an amount of about 0.3% to about 0.6% by mass. 19. The composition according to item 13, wherein at least one of mannitol and the vitamin C derivative comprises both mannitol present in an amount of about 0.9% by mass and the vitamin C derivative present in an amount of about 0.6% by mass. 20. The composition according to item 19, wherein the vitamin C derivative is ascorbic acid 2-glucoside.

[0061] 21. The composition according to item 13, wherein the HA concentration is about 10.0 mg / g to about 14.0 mg / g. 22. The composition according to item 13, wherein the HA concentration is about 12.0 mg / g. 23. A method of improving at least one of skin texture, hydration, and elasticity, the method comprising, treating a skin area by introducing multiple spaced injections of a composition comprising a hyaluronic acid (HA) gel containing crosslinked HA into the skin area in a single treatment session, The HA concentration of the composition is less than about 17.0 mg / g, A method in which the treated skin maintains at least one of improved texture, hydration, and elasticity for at least about 3 months by the treatment. 24. The method of item 23, wherein the treated skin maintains at least one of improved texture, hydration, and elasticity for at least about 6 months by the treatment. 25. The method of item 23, wherein the treated skin maintains at least one of improved texture, hydration, and elasticity for at least about 12 months by the treatment. 26. The method of item 23, wherein the HA concentration is from about 10.0 mg / g to about 14.0 mg / g. 27. The method of item 23, wherein the HA concentration is about 12.0 mg / g. 28. The method of item 23, wherein the injections are spaced at intervals of from about 5 mm to about 20 mm. 29. The method of item 23, wherein the injections are introduced in an amount of from about 5 μL to about 100 μL per injection. 30. The method of item 23, wherein the time required for the treatment is about 45 minutes or less.

[0062] 31. The method of item 23, wherein the injections are delivered through a needle having a gauge of 28G to 33G. 32. The method of item 23, wherein the composition further comprises at least one of mannitol and a vitamin C derivative. 33. The method of item 23, wherein mannitol is present in an amount of from about 0.3% by mass to about 0.9% by mass. 34. The method of item 23, wherein the vitamin C derivative is ascorbic acid 2-glucoside. 35. The method of item 34, wherein ascorbic acid 2-glucoside is present in an amount of from about 0.3% by mass to about 0.6% by mass.

[0063] 36. A method of increasing at least one of the smoothness, hydration, and elasticity of the skin, Introducing multiple spaced injections of a composition comprising a hyaluronic acid (HA) gel containing BDDE-crosslinked HA and uncrosslinked HA at a depth of about 0.5 to about 4.0 mm or about 0.5 to about 5.0 mm in the skin area in a single treatment session, The injections are introduced in an amount of about 5 μL to about 100 μL per injection, The injections are delivered through a needle having a gauge of 28G to 33G, The injections are spaced at intervals of about 5 mm to about 20 mm, and The skin area maintains increased smoothness, hydration, and / or elasticity for at least about 6 months by the treatment. 37. The method of item 36, wherein the composition further comprises at least one of mannitol and a vitamin C derivative. 38. A composition for increasing at least one of skin smoothness, hydration, and elasticity, comprising a hyaluronic acid (HA) gel containing a crosslinked HA matrix made using a low molecular weight HA material having a mass average molecular weight of about 400,000 Da to about 800,000 Da, The HA concentration of the composition is about 10.0 mg / g to about 14.0 mg / g, The composition maintains increased smoothness, hydration and / or elasticity for at least about 6 months after being introduced into the skin in a single treatment session comprising injections of multiple spaced compositions by the treatment, the injections are introduced in an amount of about 5 μL to about 100 μL per injection and are delivered through a needle having a gauge of 28G to 33G and are spaced at intervals of about 5 mm to about 20 mm. 39. The composition of item 38, wherein the composition further comprises at least one of mannitol and a vitamin C derivative.

Claims

1. An injectable composition for reducing the appearance of superficial depressions of the skin, comprising a hyaluronic acid (HA) gel containing a crosslinked HA matrix made using a low molecular weight HA material having a mass average molecular weight between about 0.20 kDa and about 0.99 kDa, preferably between about 400,000 Da and about 800,000 Da, and being at least 70% by weight, or at least about 90% by weight, more than 50% by weight based on the total mass of the HA material, wherein the HA concentration of the composition is less than about 17.0 mg / g, for example between about 10.0 mg / g and about 14.0 mg / g, preferably about 12 mg / g, the crosslinked HA matrix is crosslinked with a crosslinking agent selected from the group consisting of 1,4-butanediol diglycidyl ether (BDDE), 1,2-bis(2,3-epoxypropoxy)ethylene, and 1-(2,3-epoxypropyl)-2,3-epoxycyclohexane, the composition preferably does not contain an antioxidant or a vitamin, the composition is an injectable composition that maintains an appearance with reduced superficial depressions of the skin for at least about 3 months after being introduced into the skin.

2. The composition according to claim 1, which maintains an appearance with reduced superficial depressions of the skin for at least about 6 months, preferably at least about 9 months or 12 months after being introduced into the skin.

3. The composition according to claim 1 or 2, which contains uncrosslinked HA in an amount of preferably less than 10% by weight or less than 5% by weight based on the total mass of the composition.

4. The composition according to claims 1 to 3, which further comprises at least one of mannitol and a vitamin C derivative, or preferably further comprises lidocaine in an amount between about 0.1% by weight and about 5% by weight of the composition, for example in an amount of 0.3% by weight.

5. The composition according to claim 4, wherein mannitol is present in an amount between about 0.3% by weight and about 0.9% by weight based on the total mass of the composition.

6. The composition according to claim 4, wherein the vitamin C derivative is ascorbic acid 2-glucoside.

7. The composition according to claim 6, wherein ascorbic acid 2-glucoside is present in an amount between about 0.3% by weight and about 0.6% by weight based on the total mass of the composition.

8. The composition according to claims 1 to 4, which further comprises about 0.9% by weight of mannitol and about 0.6% by weight of ascorbic acid 2-glucoside based on the total mass of the composition.

9. A hyaluronic acid (HA) gel containing a cross-linked HA matrix, at least one of mannitol and a vitamin C derivative comprising an injectable composition for reducing the appearance of superficial depressions in the skin or for improving the quality of the skin, wherein the HA concentration of the composition is less than about 17.0 mg / g, such as from about 10.0 mg / g to about 14.0 mg / g, preferably about 12.0 mg / g, the composition maintaining a reduced appearance of superficial depressions in the skin or an improved quality of the skin for at least about 3 months after being introduced into the skin. An injectable composition.

10. The cross-linked HA matrix is made using a low molecular weight HA material having a mass average molecular weight between about 0.20 MDa and about 0.99 MDa, at least 70% by mass, or at least 90% by mass, based on the total mass of the HA material, preferably between about 400,000 Da and about 800,000 Da. The injectable composition according to claim 9.

11. The cross-linked HA matrix is cross-linked with a cross-linking agent selected from the group consisting of 1,4-butanediol diglycidyl ether (BDDE), 1,2-bis(2,3-epoxypropoxy)ethylene, and 1-(2,3-epoxypropyl)-2,3-epoxycyclohexane. The injectable composition according to claims 9 to 11.

12. The composition according to claims 9 to 11, maintaining a reduced appearance of superficial depressions in the skin or an improved quality of the skin for at least about 6 months, at least about 9 months, or at least about 12 months after being introduced into the skin.

13. The composition according to claims 9 to 12, further comprising lidocaine, preferably in an amount between about 0.1% by mass and about 5% by mass of the composition, such as 0.3% by mass.

14. The composition according to claims 9 to 13, wherein mannitol is present in an amount between about 0.3% by mass and about 0.9% by mass based on the total mass of the composition.

15. The composition according to claims 9 to 14, wherein the vitamin C derivative is ascorbic acid 2-glucoside.

16. The composition according to claim 15, wherein ascorbic acid 2-glucoside is present in an amount between about 0.3% by mass and about 0.6% by mass based on the total mass of the composition.

17. The composition according to any one of claims 9 to 13, wherein at least one of mannitol and the vitamin C derivative is present at about 0.9% by mass of mannitol and about 0.6% by mass of the vitamin C derivative, based on the total mass of the composition.

18. The composition according to claim 17, wherein the vitamin C derivative is ascorbic acid 2-glucoside.

19. A composition for use in a method of improving at least one of skin texture, hydration, and elasticity, the method comprising introducing into a skin region in a single treatment session a plurality of spaced injections of a composition comprising a hyaluronic acid (HA) gel containing a crosslinked HA matrix made with a low molecular weight HA material having a mass average molecular weight between about 0.20 MDa and about 0.99 MDa, preferably between about 400,000 Da and about 800,000 Da, wherein the crosslinked HA matrix is more than 50% by mass, at least 70% by mass, or at least about 90% by mass, based on the total mass of the crosslinked HA matrix, the crosslinked HA matrix being crosslinked with a crosslinking agent selected from the group consisting of 1,4-butanediol diglycidyl ether (BDDE), 1,2-bis(2,3-epoxypropoxy)ethylene, and 1-(2,3-epoxypropyl)-2,3-epoxycyclohexane, the HA concentration of the composition being less than about 17.0 mg / g, such as from about 10.0 mg / g to about 14.0 mg / g, preferably about 12.0 mg / g, the injections being spaced at intervals between about 5 mm and about 20 mm, such as between 5 mm or 10 mm, the treated skin maintaining, by the treatment, at least one of improved texture, hydration, and elasticity for at least about 3 months.

20. A non-therapeutic method of improving at least one of skin texture, hydration, and elasticity, the method comprising introducing into a skin region in a single treatment session a plurality of spaced injections of a composition comprising a hyaluronic acid (HA) gel containing a crosslinked HA matrix made with a low molecular weight HA material having a mass average molecular weight between about 0.20 MDa and about 0.99 MDa, preferably between about 400,000 Da and about 800,000 Da, wherein the crosslinked HA matrix is more than 50% by mass, at least 70% by mass, or at least about 90% by mass, based on the total mass of the crosslinked HA matrix. The crosslinked HA matrix is crosslinked with a crosslinking agent selected from the group consisting of 1,4-butanediol diglycidyl ether (BDDE), 1,2-bis(2,3-epoxypropoxy)ethylene, and 1-(2,3-epoxypropyl)-2,3-epoxycyclohexane, the HA concentration of the composition is less than about 17.0 mg / g, such as from about 10.0 mg / g to about 14.0 mg / g, preferably about 12.0 mg / g, the injections are spaced apart between about 5 mm and about 20 mm, such as at intervals of 5 mm or 10 mm, a non-therapeutic method in which the treated skin maintains at least one of improved texture, hydration, and elasticity for at least about 3 months as a result of the treatment.

21. The composition for use according to claim 19 or the non-therapeutic method according to claim 20, wherein the treated skin maintains at least one of improved texture, hydration, and elasticity for at least about 6 months, at least about 9 months, or at least about 12 months as a result of the treatment.

22. The composition for use according to claim 19 or 21 or the non-therapeutic method according to claim 20 or 21, wherein the treated skin maintains at least one of improved texture, hydration, and elasticity for at least about 6 months, at least about 9 months, or at least about 12 months as a result of the treatment.

23. The composition for use according to claims 19 and 21 to 22 or the non-therapeutic method according to claims 20 to 22, wherein the injection is introduced in an amount of about 5 μL to about 100 μL per injection.

24. The composition for use according to claims 19 and 21 to 23 or the non-therapeutic method according to claims 20 to 23, wherein the time required for the treatment is about 45 minutes or less.

25. The composition for use according to claims 19 and 21 to 24 or the non-therapeutic method according to claims 20 to 24, wherein the injection is delivered through a needle having a gauge of 28G to 33G.

26. The composition for use according to claims 19 and 21 to 25 or the non-therapeutic method according to claims 20 to 25, wherein the composition further comprises at least one of mannitol and a vitamin C derivative, or the composition does not contain an antioxidant or a vitamin, and / or the composition preferably further comprises lidocaine in an amount between about 0.1% by mass and about 5% by mass of the composition, such as 0.3% by mass.

27. A composition for use according to claims 19 and 21 to 26 or a non-therapeutic method according to claims 20 to 26, wherein mannitol is present in an amount between about 0.3% by mass and about 0.9% by mass based on the total mass of the composition.

28. A composition for use according to claims 19 to 27 or a non-therapeutic method according to claims 20 to 27, wherein the vitamin C derivative is ascorbic acid 2-glucoside.

29. A composition for use according to claim 28 or a non-therapeutic method according to claim 28, wherein ascorbic acid 2-glucoside is present in an amount between about 0.3% by mass and about 0.6% by mass based on the total mass of the composition.

30. A composition for use in a method of increasing at least one of skin smoothness, hydration, and elasticity, the method comprising: introducing, in a single treatment session, a plurality of spaced injections of the composition comprising a hyaluronic acid (HA) gel containing BDDE-crosslinked HA and uncrosslinked HA into a skin area at an injection depth between about 0.5 mm and about 5.0 mm, preferably between about 1.0 mm and about 4.0 mm, more preferably between about 1.5 mm and about 3.0 mm; the HA concentration of the composition being less than about 17.0 mg / g, such as from about 10.0 mg / g to about 14.0 mg / g, preferably about 12.0 mg / g; the injections being introduced in an amount of about 5 μL to about 100 μL per injection; the injections being delivered through a needle having a gauge of 28G to 33G; the injections being spaced apart at intervals between about 5 mm and about 20 mm, such as between 5 mm or 10 mm; the skin area maintaining increased smoothness, hydration, and / or elasticity for at least about 6 months, at least about 9 months, or at least about 12 months as a result of the treatment.

31. A non-therapeutic method of increasing at least one of skin smoothness, hydration, and elasticity, the method comprising introducing, in a single treatment session, a plurality of spaced injections of a composition comprising a hyaluronic acid (HA) gel containing BDDE-crosslinked HA and uncrosslinked HA into a skin area at an injection depth between about 0.5 mm and about 5.0 mm, preferably between about 1.0 mm and about 4.0 mm, more preferably between about 1.5 mm and about 3.0 mm, the HA concentration of the composition being less than about 17.0 mg / g, such as from about 10.0 mg / g to about 14.0 mg / g, preferably about 12.0 mg / g; The injection is introduced in an amount of from about 5 μL to about 100 μL per injection, the injection is delivered through a needle having a gauge of 28G to 33G, the injections are spaced apart at intervals of from about 5 mm to about 20 mm, such as between 5 mm or 10 mm, a non-therapeutic method in which the skin area maintains increased smoothness, hydration, and / or elasticity for at least about 6 months, at least about 9 months, or at least about 12 months by the treatment.

32. The composition further comprises at least one of mannitol and a vitamin C derivative, or the composition does not contain an antioxidant or vitamin, and / or the composition preferably further comprises lidocaine in an amount of from about 0.1% to about 5% by weight of the composition, such as 0.3% by weight, for use according to claim 30 or the non-therapeutic method according to claim 31.

33. A composition for increasing at least one of skin smoothness, hydration, and elasticity, comprising a hyaluronic acid (HA) gel comprising a cross-linked HA matrix made of a low molecular weight HA material having a mass average molecular weight between about 0.20 MDa and about 0.99 MDa, preferably between about 400,000 Da and about 800,000 Da, wherein the HA concentration of the composition is less than about 17.0 mg / g, such as from about 10.0 mg / g to about 14.0 mg / g, preferably 12.0 mg / g, the composition is introduced into the skin in a single treatment session comprising injections of a plurality of spaced-apart compositions by treatment and maintains increased smoothness, hydration, and / or elasticity for at least about 6 months, at least about 9 months, or at least about 12 months, the injection is introduced in an amount of from about 5 μL to about 100 μL per injection and is delivered through a needle having a gauge of 28G to 33G, preferably 32G, and is spaced apart at intervals of from about 5 mm to about 20 mm, such as 5 mm or 10 mm.

34. The composition further comprises at least one of mannitol and a vitamin C derivative, or the composition does not contain an antioxidant or vitamin, and / or the composition preferably further comprises lidocaine in an amount of from about 0.1% to about 5% by weight of the composition, such as 0.3% by weight, according to claim 33.

35. The composition according to claims 33 to 34, wherein the crosslinked HA matrix is made using at least 70% by mass, or at least about 90% by mass of the low molecular weight HA material, which exceeds 50% by mass based on the total mass of the HA material.

36. The composition according to claims 33 to 35, wherein the crosslinked HA matrix is crosslinked with a crosslinking agent selected from the group consisting of 1,4-butanediol diglycidyl ether (BDDE), 1,2-bis(2,3-epoxypropoxy)ethylene, and 1-(2,3-epoxypropyl)-2,3-epoxycyclohexane.

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