Myocardial infarction boundary region tissue identification method

Abstract

The invention relates to the technical field of medical experiments, and particularly discloses a myocardial infarction boundary region tissue identification method which comprises the following steps: performing a biaxial mechanical tensile test on a to-be-identified heart tissue: the tissue between the normal myocardial tissue stiffness and the myocardial infarction tissue stiffness is a first potential boundary region; performing double-staining identification on the to-be-identified heart tissue: firstly, staining by using an Evans blue staining solution, then staining by using a 2, 3, 5-triphenyltetrazole chloride staining solution, observing a staining result, taking a red region as a second potential boundary region, and taking a red region as a second potential boundary region; the overlapped part of the first potential boundary region and the second potential boundary region is the myocardial infarction boundary region. According to the myocardial infarction boundary region tissue identification method disclosed by the invention, the myocardial infarction boundary region is subjected to multi-dimensional identification from physical and chemical angles, so that the accuracy of an identification result is ensured.

Description

Technical Field

[0001] The present application relates to the field of medical experimental technology, and in particular to a method for identifying tissue in the border zone of myocardial infarction. Background Art

[0002] Within the infarcted heart, three zones can be distinguished morphologically: the infarct border zone, the uninjured distal myocardial area, and the infarct zone, which is characterized by damage and cell death. Myocardial infarction is usually caused by occlusion of a coronary artery due to atherosclerotic plaque formation. The blockage hinders the flow of blood and oxygen to the localized area of ​​myocardial tissue, resulting in hypoxia and massive myocardial cell death. A steep oxygen gradient forms at the interface between the injured hypoxic tissue and the surrounding viable normoxic tissue, a region called the infarct border zone.

[0003] The infarct border zone is particularly important for remodeling processes after myocardial infarction. In the following days, weeks, and months, the injured myocardium, especially the border zone of the infarct, undergoes extensive remodeling of its electrical properties, which may lead to heart failure. In vivo and ex vivo models have shown that border zone tissue is a known substrate for arrhythmias and generates less force than the distal myocardium. These observations suggest that the border zone is particularly susceptible to pathophysiological remodeling, probably due to the heterogeneous cellular microenvironment. Various studies have implicated it in infarct expansion, fibrosis, hypertrophy, and repair, as well as in electrically unstable processes that trigger arrhythmias and sudden cardiac events. The boundary between injured hypoxic tissue and adjacent viable normoxic tissue (the infarct border zone) is characterized by an oxygen gradient.

[0004] However, due to the limitations of existing experimental models, little is known about the impact of the myocardial infarction border zone on cardiac tissue function. However, these changes in the myocardial infarction border zone are different from those observed in tissues exposed to uniform normoxia or hypoxia, indicating that oxygen gradients regulate cardiac tissue phenotypes differently. From an anatomical perspective, there is no clear tissue identification method for the myocardial infarction border zone, and the function of the border zone cannot be clarified. Therefore, the existing technology needs to be improved. Summary of the invention

[0005] In view of the above-mentioned deficiencies in the prior art, the purpose of the present application is to provide a method for identifying myocardial infarction boundary zone tissue, aiming to solve the problem of lack of a method for identifying myocardial infarction boundary zone tissue in the prior art.

[0006] The technical solution of this application is as follows: In a first aspect of the present application, a method for identifying myocardial infarction border zone tissue is provided, comprising the steps of: A biaxial mechanical tensile test is performed on the cardiac tissue to be identified: the tissue between the stiffness of normal myocardial tissue and the stiffness of myocardial infarction tissue is the first potential boundary zone; a double-staining identification is performed on the cardiac tissue to be identified: first staining is performed with Evans blue staining solution, and then staining is performed with 2,3,5-triphenyltetrazolium chloride staining solution, and the staining results are observed. The red area is the second potential boundary zone; the overlapping part of the first potential boundary zone and the second potential boundary zone is the myocardial infarction boundary zone.

[0007] Optionally, the steps of the biaxial mechanical tensile test include: A heart tissue sample is obtained, a tensile force is applied to the heart tissue sample along a first direction and a second direction, and the stiffness value of the heart tissue sample is measured; the angle between the first direction and the second direction is 90°.

[0008] Optionally, a strain ratio of the tensile force in the first direction to the tensile force in the second direction is at least one of 2:1, 4:3 or 1:1.

[0009] Optionally, the mass ratio of Evans blue dye in the Evans blue staining solution is 0.5-3%; the mass ratio of 2,3,5-triphenyltetrazolyl chloride in the 2,3,5-triphenyltetrazolyl chloride staining solution is 1-3%.

[0010] In a second aspect of the present application, a biaxial mechanical stretching test device is provided, comprising a base and an X-axis mechanical stretching assembly, a Y-axis mechanical stretching assembly and a sample detection platform arranged on the base, wherein the angle formed by the extension direction of the X-axis mechanical stretching assembly and the extension direction of the Y-axis mechanical stretching assembly is 90°; the X-axis mechanical stretching assembly comprises a first stretching assembly and a second stretching assembly which are centrally symmetrically arranged with the sample detection platform as the center of symmetry, and the Y-axis mechanical stretching assembly comprises a third stretching assembly and a fourth stretching assembly which are centrally symmetrically arranged with the sample detection platform as the center of symmetry; the first stretching assembly, the second stretching assembly , the third stretching assembly and the fourth stretching assembly are both provided with a clamping portion on one side close to the sample detection platform, at least one of the clamping portion of the first stretching assembly and the clamping portion of the second stretching assembly can move along the extension direction of the X-axis mechanical stretching assembly, and at least one of the clamping portion of the third stretching assembly and the clamping portion of the fourth stretching assembly can move along the extension direction of the Y-axis mechanical stretching assembly; at least one of the first stretching assembly and the second stretching assembly is provided with a force sensor, and at least one of the third stretching assembly and the fourth stretching assembly is provided with a force sensor, and the force sensor is configured to record the force value.

[0011] Optionally, the first stretching assembly, the second stretching assembly, the third stretching assembly and the fourth stretching assembly all include a displacement driver and a connecting rod, and the displacement driver, the connecting rod and the clamping portion are fixedly connected in sequence.

[0012] Optionally, a water bath is provided on the base, and the X-axis mechanical stretching assembly, the Y-axis mechanical stretching assembly and the sample detection platform are arranged in the water bath.

[0013] The third aspect of the present application provides an application of the biaxial mechanical tensile testing device of the second aspect of the present application in the identification of myocardial infarction boundary zone tissue.

[0014] The fourth aspect of the present application provides a method for identifying the boundary zone of myocardial infarction using the biaxial mechanical tensile testing device of the second aspect of the present application, comprising: obtaining a heart tissue sample; measuring the true thickness at 9 different positions of the heart tissue sample using a dial indicator; laying the heart tissue sample flat on the sample detection platform, removing excess tissue along the edge of the sample detection platform, and fixing the heart tissue sample using the clamping portion; applying a preload force of 10 mN along the X-axis and the Y-axis, and then applying biaxial tensile force on the X-axis and the Y-axis respectively with reference to 30% of the strain of the X-axis and a tensile speed of 10 µm / s, performing stress relaxation for 300 s after all loading is completed, recording the force value change through a sensor, and recording the relationship curve between the force value change and time.

[0015] Optionally, the biaxial tensile force-strain ratio is at least one of 2:1, 4:3 or 1:1.

[0016] Beneficial effects of the present application: The myocardial infarction boundary zone tissue identification method of the present application includes biaxial mechanical tensile testing, double staining identification and transcriptomic analysis of the cardiac tissue to be identified, and combines mechanical properties, chemical staining and transcriptomic analysis to conduct multi-dimensional identification of the myocardial infarction boundary zone from a macroscopic and microscopic perspective to ensure the accuracy of the identification results. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for describing the embodiments are briefly introduced below.

[0018] Figure 1 A schematic diagram of the structure of a biaxial mechanical tensile testing device provided in an embodiment of the present application; Figure 2 A physical picture of the biaxial mechanical tensile testing device provided in the embodiment of the present application; Figure 3 This is a graph of the ultrasound results of myocardial infarction in mice provided in the examples of the present application; Figure 4Biaxial mechanical tensile test diagram provided for the embodiment of this application: A is the tensile stress-strain curve along the direction of myocardial fiber; B is the creep stress-relaxation curve along the direction of myocardial fiber; C is the tensile stress-strain curve perpendicular to the direction of myocardial fiber; D is the creep stress-relaxation curve perpendicular to the direction of myocardial fiber; Figure 5 This is a double staining identification diagram provided in the examples of this application. Description of the drawings: 1. Base; 2. X-axis mechanical stretching assembly; 21. First stretching assembly; 211. Clamping part; 212. Connecting rod; 213. Displacement driver; 214. Force sensor; 22. Second stretching assembly; 3. Y-axis mechanical stretching assembly; 31. Third stretching assembly; 32. Fourth stretching assembly; 4. Sample detection platform; 5. Water bath. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical solutions and advantages of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below in combination with the drawings and embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments of the present application, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the protection scope of the present application. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0021] It should be noted that if there are descriptions involving "first", "second", etc. in the implementation of this application, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or suggesting their relative importance and implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the fact that ordinary technicians in the field can implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by this application.

[0022] The present application embodiment provides a method for identifying myocardial infarction border zone tissue, comprising the steps of: The cardiac tissue to be identified was subjected to biaxial mechanical tensile testing: the tissue between the stiffness of normal myocardial tissue and the stiffness of myocardial infarction tissue was the first potential boundary zone; Double staining is performed on the cardiac tissue to be identified: first staining is performed with Evans blue staining solution, and then staining is performed with 2,3,5-triphenyltetrazolium chloride staining solution, and the staining results are observed. The red area is the second potential boundary area; The overlapping portion of the first potential boundary area and the second potential boundary area is the myocardial infarction boundary area.

[0023] The myocardial infarction boundary zone tissue identification method of the present application combines the mechanical properties results of the cardiac tissue to be identified and the chemical staining results to perform multi-dimensional identification of the myocardial infarction boundary zone from a physical and chemical perspective to ensure the accuracy of the identification results.

[0024] In some embodiments, the steps of biaxial mechanical tensile testing include: A heart tissue sample is obtained, a tensile force is applied to the heart tissue sample along a first direction and a second direction, and the stiffness value of the heart tissue sample is measured, wherein the angle between the first direction and the second direction is 90°.

[0025] Specifically, the steps for obtaining a cardiac tissue sample include: (1) After inducing anesthesia with 5% isoflurane, the chest was opened and the inferior vena cava was cut to bleed. The heart was perfused from the apex of the left ventricle with phosphate-buffered saline containing 150 mM potassium chloride to stop the heart in saline. The heart was removed; (2) Embed the heart tissue block in 2% low-melting-point agarose, mount it on the platform of a vibrating microtome, and cut the sample to a thickness of 500 μm.

[0026] In some embodiments, a strain ratio of the tensile force in the first direction to the tensile force in the second direction is at least one of 2:1, 4:3, or 1:1.

[0027] In some embodiments, the mass ratio of Evans blue dye in the Evans blue staining solution is 0.5-3%. For example, the mass ratio of Evans blue dye in the Evans blue staining solution is 0.5%, 1%, 1.5%, 2%, 2.5% or 3%. The mass ratio of 2,3,5-triphenyl tetrazolium chloride in the 2,3,5-triphenyl tetrazolium chloride staining solution is 1-3%, for example, the mass ratio of 2,3,5-triphenyl tetrazolium chloride in the 2,3,5-triphenyl tetrazolium chloride staining solution is 1%, 1.5%, 2%, 2.5% or 3%.

[0028] Evans blue dye has a strong affinity with myocardial tissue. After ligation, Evans blue dye solution is injected into the inferior vena cava, so that the myocardium with blocked blood flow in the left anterior descending coronary artery is not stained, while the myocardium with normal blood supply is stained dark blue, thereby distinguishing normal myocardial tissue from myocardium without blood supply (including myocardial infarction area and myocardial infarction border area). 2,3,5-Triphenyltetrazolium chloride (TTC) is a fat-soluble photosensitive complex. As a proton receptor of the pyridine-nucleoside structural enzyme system in the respiratory chain, it reacts with dehydrogenase in normal and ischemic myocardial tissue to appear red (normal myocardium + myocardial infarction border area), while the dehydrogenase activity in the infarcted myocardial tissue drops sharply and cannot react, so it will not change to pale (myocardial infarction area). Evans blue dye appears dark blue in normal myocardial tissue, which masks the staining of TTC. Therefore, after double staining of the myocardial infarction heart model, normal myocardial tissue appears blue, myocardial infarction border area tissue appears red, and myocardial infarction dead tissue appears pale.

[0029] See also Figure 1 and Figure 2 The embodiment of the present application also provides a biaxial mechanical stretching testing device 100, which generally includes: a base 1 and an X-axis mechanical stretching component 2, a Y-axis mechanical stretching component 3 and a sample detection platform 4 arranged on the base 1, and the angle formed by the extension direction of the X-axis mechanical stretching component 2 and the extension direction of the Y-axis mechanical stretching component 3 is 90°.

[0030] Further, the X-axis mechanical stretching assembly 2 includes a first stretching assembly 21 and a second stretching assembly 22 which are centrally symmetrically arranged with the sample detection platform 4 as the symmetry center, and the Y-axis mechanical stretching assembly 3 includes a third stretching assembly 31 and a fourth stretching assembly 32 which are centrally symmetrically arranged with the sample detection platform 4 as the symmetry center. The first stretching assembly 21, the second stretching assembly 22, the third stretching assembly 31 and the fourth stretching assembly 32 are all provided with a clamping portion 211 on one side close to the sample detection platform 4, and at least one of the clamping portion 211 of the first stretching assembly 21 and the clamping portion 211 of the second stretching assembly 22 can move along the extension direction of the X-axis mechanical stretching assembly 2, and at least one of the clamping portion 211 of the third stretching assembly 31 and the clamping portion 211 of the fourth stretching assembly 32 can move along the extension direction of the Y-axis mechanical stretching assembly 3. At least one of the first stretching assembly 21 and the second stretching assembly 22 is provided with a force sensor 214, and at least one of the third stretching assembly 31 and the fourth stretching assembly 32 is provided with a force sensor 214. When the clamping portion 211 of the first stretching assembly 21, the second stretching assembly 22, the third stretching assembly 31 and the fourth stretching assembly 32 moves, the force sensor 214 can record the force value in the direction.

[0031] In some embodiments, the clamping portion may include a plurality of stainless steel needles arranged at intervals, and the side of the stainless steel needle away from the stretching assembly (the first stretching assembly 21, the second stretching assembly 22, the third stretching assembly 31, and the fourth stretching assembly 32) has a certain curvature and is bent toward the sample detection platform 4, so as to facilitate penetration into the heart tissue to be identified for fixation. The number of stainless steel needles may be 3 or 5.

[0032] The biaxial mechanical tensile testing device 100 can be used to perform biaxial mechanical tensile testing on the cardiac tissue to be identified. Specifically, the cardiac tissue to be identified is fixed on the sample detection platform 4 through four clamping parts 211, and the forces in the X-axis direction and the Y-axis direction can be applied to the cardiac tissue to be identified through the X-axis mechanical tensile component 2 and the Y-axis mechanical tensile component 3, and the force values ​​in the X-axis direction and the Y-axis direction are recorded by the force sensor 214. By combining the forces applied in the X-axis and Y-axis directions and the data recorded by the force sensor, the mechanical properties of the cardiac tissue to be identified can be obtained, including the Green-Lagrange strain tensor and the second Piola-Kirchhoff stress, or the tensile stress-strain curve of the cardiac tissue in the direction of the myocardial fibers and the tensile stress-strain curve in the direction perpendicular to the myocardial fibers, etc. The cardiac tissue to be identified can be judged by subsequent calculations to identify whether it is a myocardial infarction boundary area.

[0033] In some embodiments, the sample detection platform 4 is a glass slide, and the biaxial mechanical tensile testing device 100 further includes a microscopic observation component, preferably a laser confocal microscope. The laser confocal microscope can be used to stimulate the autofluorescence of elastin and collagen in myocardial tissue to perform three-dimensional in-situ scanning, observe the changes in the spatial positions of small blood vessels and myocardial cells during the stretching process, and then obtain the coupling relationship between myocardial fibers and small blood vessels during the deformation process, so as to identify the boundary area of ​​myocardial infarction.

[0034] In some embodiments, the first stretching assembly 21, the second stretching assembly 22, the third stretching assembly 31, and the fourth stretching assembly 32 all include a displacement driver 213 and a connecting rod 212, and the displacement driver 213, the connecting rod 212, and the clamping portion 211 are fixedly connected in sequence. The displacement driver 213 can drive the connecting rod 212 to translate, so as to drive the clamping portion 211 to move, and then generate tension on the cardiac tissue to be identified fixed by the clamping portion 211.

[0035] In some embodiments, a water bath 5 is provided on the base 1, and the X-axis mechanical stretching assembly 2, the Y-axis mechanical stretching assembly 3 and the sample detection platform 4 are arranged in the water bath. The water bath 5 can be used to hold liquids such as buffer solutions, so that the cardiac tissue to be identified is kept in a solution of a certain solubility during the biaxial mechanical stretching test, thereby better restoring the physiological environment of the cardiac tissue to be identified.

[0036] The embodiment of the present application also provides an application of the biaxial mechanical tensile testing device as described above in the identification of myocardial infarction boundary zone tissue.

[0037] The present application also provides a method for identifying a myocardial infarction boundary zone using the biaxial mechanical tensile testing device as described above, comprising the steps of: Obtaining cardiac tissue samples; The true thickness was measured using a dial indicator at 9 different locations on the heart tissue samples; Lay the heart tissue sample flat on the sample detection platform, remove excess tissue along the edge of the sample detection platform, and fix the heart tissue sample with a clamping part; A preload force of 10 mN was applied along the X-axis and Y-axis, and then a biaxial tensile force was applied on the X-axis and Y-axis respectively with a strain of 30% on the X-axis and a tensile speed of 10 µm / s as reference. After all loading was completed, stress relaxation was performed for 300 s, and the force value change was recorded by the sensor and the force value change curve was plotted.

[0038] In some embodiments, the biaxial stretching force-strain ratio is at least one of 2:1, 4:3, or 1:1.

[0039] The following is further described through specific implementation methods.

[0040] Example 1 Establishment of myocardial infarction model in mice The mice (C57BL / 6J) were intubated and ventilated with 2% isoflurane. After anesthesia and fixation, the ribs were opened upwards, and a thoracotomy was performed at the fourth intercostal space on the left side to expose the heart. The left anterior descending coronary artery of the mice was permanently ligated with 8-0 nylon suture to establish a mouse myocardial infarction model. The mouse heart was examined by ultrasound, and the results were as follows Figure 3 As shown, from Figure 3 It can be seen that the mouse heart ultrasound results showed obvious anterior wall contraction abnormalities, and the ejection fraction decreased to below 50%, indicating the success of the animal model.

[0041] Example 2 Biaxial mechanical tensile test (1) Obtain normal myocardial tissue, myocardial infarction tissue, and myocardial infarction border zone tissue: After inducing anesthesia with 5% isoflurane, open the chest and cut the inferior vena cava for bleeding. Perfuse the heart from the apex of the left ventricle with phosphate-buffered saline containing 150 mM potassium chloride to stop the heart in saline. Excise and obtain the heart; embed the heart tissue block in 2% low-melting point agarose, mount it on the platform of a vibrating microtome, and cut the sample with a thickness of 500 um; (2) After obtaining the sample, use a dial indicator to measure the true thickness at 9 different locations; (3) Lay the sample flat on the sample testing platform, carefully remove excess tissue along the edge of the platform, and insert the five stainless steel needles of each hook clamp through the sample into the guide hole; (4) Adjust the positions of the four displacement actuators of the planar biaxial stretching instrument and set the distance between the two opposing needles to 9.5 mm; (5) A preload of 10 mN was applied along the X-axis and Y-axis, and the initial length of the sample in the fiber and perpendicular fiber directions was defined as the distance between the opposite hook clamps under this preload, respectively; (6) With a strain of 30% on the X-axis and a tensile speed of 10 µm / s as reference, quasi-static biaxial stretching with strain ratios of 2:1, 4:3, and 1:1 was applied on the X-axis and Y-axis, respectively. After all loading was completed, stress relaxation was performed for 300 s.

[0042] The force change is recorded by the sensor and the force change curve is drawn. Figure 4 As shown. Combined Figure 4 The calculation results show that the stiffness of normal myocardial tissue is 180.0 ± 5.4 kPa, the stiffness of infarcted tissue is 321.5 ± 46.9 kPa, and the stiffness of the border zone is between the two, 236.8 ± 38.1 kPa. Therefore, the tissue between the stiffness of normal myocardial tissue and the stiffness of myocardial infarction tissue is the border zone of myocardial infarction.

[0043] Example 3 Double staining identification (1) Take the mouse myocardial infarction model constructed in Example 1, free the vena cava, clamp the distal end, insert a needle from the upper end of the vascular clamp, and inject 3 mL of 1% Evans blue staining solution (EB staining solution, 1g Evans Blue, 100 mL double distilled water). Then quickly remove the heart, rinse with pre-cooled PBS, stop the heartbeat in 30 mM KCl solution, and freeze it at -20°C for 30 minutes.

[0044] (2) Cut the heart tissue in (1) into slices with a thickness of 1.5 mm using a mold, place them in a 6-well plate containing 3 mL of 2% 2,3,5-triphenyltetrazolium chloride, and incubate them in a 37°C constant temperature water bath in the dark for 20 min. After incubation, place the slices in 4% FPA fixative for fixation and observe and photograph them the next day.

[0045] The final section staining results are as follows Figure 5 As shown, from Figure 5 It can be seen that the red area is the myocardial infarction boundary area, the blue area is the normal area, and the white area is the myocardial infarction area.

[0046] It should be understood that the application of the present application is not limited to the above examples. For ordinary technicians in this field, improvements or changes can be made based on the above description. All these improvements and changes should fall within the scope of protection of the claims attached to this application.

Claims

1. A method for identifying myocardial infarction border zone tissue, characterized in that: Includes steps: The cardiac tissue to be identified was subjected to biaxial mechanical tensile testing: the tissue between the stiffness of normal myocardial tissue and the stiffness of myocardial infarction tissue was the first potential boundary zone; Double staining is performed on the cardiac tissue to be identified: first staining is performed with Evans blue staining solution, and then staining is performed with 2,3,5-triphenyltetrazolium chloride staining solution, and the staining results are observed. The red area is the second potential boundary area; The overlapping portion of the first potential boundary area and the second potential boundary area is the myocardial infarction boundary area.

2. The method for identifying myocardial infarction border zone tissue according to claim 1, characterized in that: The steps of the biaxial mechanical tensile test include: Obtaining a cardiac tissue sample, applying a tensile force to the cardiac tissue sample along a first direction and a second direction, and measuring a stiffness value of the cardiac tissue sample; The included angle between the first direction and the second direction is 90°.

3. The method for identifying myocardial infarction border zone tissue according to claim 2, characterized in that: A strain ratio of the tensile force in the first direction to the tensile force in the second direction is at least one of 2:1, 4:3 or 1:

1.

4. The method for identifying myocardial infarction border zone tissue according to claim 1, characterized in that: The mass ratio of Evans blue dye in the Evans blue staining solution is 0.5-3%; The mass ratio of 2,3,5-triphenyltetrazolyl chloride in the 2,3,5-triphenyltetrazolyl chloride dyeing solution is 1-3%.

5. A biaxial mechanical tensile testing device, characterized in that: include: A base, an X-axis mechanical stretching component, a Y-axis mechanical stretching component and a sample detection platform arranged on the base, wherein the angle formed by the extension direction of the X-axis mechanical stretching component and the extension direction of the Y-axis mechanical stretching component is 90°; The X-axis mechanical stretching assembly includes a first stretching assembly and a second stretching assembly that are centrally symmetrically arranged with the sample detection platform as the symmetry center, and the Y-axis mechanical stretching assembly includes a third stretching assembly and a fourth stretching assembly that are centrally symmetrically arranged with the sample detection platform as the symmetry center; The first stretching assembly, the second stretching assembly, the third stretching assembly and the fourth stretching assembly are all provided with a clamping portion on one side close to the sample detection platform, and at least one of the clamping portion of the first stretching assembly and the clamping portion of the second stretching assembly can move along the extension direction of the X-axis mechanical stretching assembly, and at least one of the clamping portion of the third stretching assembly and the clamping portion of the fourth stretching assembly can move along the extension direction of the Y-axis mechanical stretching assembly; At least one of the first stretching assembly and the second stretching assembly is provided with a force sensor, and at least one of the third stretching assembly and the fourth stretching assembly is provided with a force sensor, wherein the force sensor is configured to record a force value.

6. The biaxial mechanical tensile testing device according to claim 5, characterized in that: The first stretching assembly, the second stretching assembly, the third stretching assembly and the fourth stretching assembly all include a displacement driver and a connecting rod, and the displacement driver, the connecting rod and the clamping portion are fixedly connected in sequence.

7. The biaxial mechanical tensile testing device according to claim 5, characterized in that: A water bath is provided on the base, and the X-axis mechanical stretching component, the Y-axis mechanical stretching component and the sample detection platform are arranged in the water bath.

8. Use of the biaxial mechanical tensile testing device according to any one of claims 5 to 7 in the identification of border zone tissue of myocardial infarction.

9. A method for identifying myocardial infarction border zone using the biaxial mechanical tensile testing device according to any one of claims 5 to 7, characterized in that: include: Obtaining cardiac tissue samples; Using a dial indicator to measure the true thickness at 9 different locations of the heart tissue sample; Laying the cardiac tissue sample flat on the sample detection platform, removing excess tissue along the edge of the sample detection platform, and fixing the cardiac tissue sample using the clamping part; A preload force of 10 mN was applied along the X-axis and Y-axis, and then a biaxial tensile force was applied on the X-axis and Y-axis respectively with a strain of 30% on the X-axis and a tensile speed of 10 µm / s as reference. After all loading was completed, stress relaxation was performed for 300 s, and the force value change was recorded by the sensor, and the relationship curve between the force value change and time was recorded.

10. The method according to claim 9, characterized in that The strain ratio of the biaxial tensile force is at least one of 2:1, 4:3 or 1:1.

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