| BackgroundThe reconstruction of large soft tissue defects is still a difficult problem faced by plastic surgeons at present.The existing reconstruction methods,such as skin flap transplantation,fat transplantation or material filling,need surgical operation.in recent years,the non-surgical invasion methods can also achieve good reconstruction results.In some studies,extracorporeal dilators have been used in the breast to stimulate adipose tissue growth by applying traction.This method of in situ regeneration of adipose tissue through in vitro expander has attracted our attention.however,the mechanism of in vitro expander promoting tissue regeneration is not clear.In order to further clarify the mechanism of tissue regeneration promoted by expander in vitro and improve the in situ regeneration ability of adipose tissue,we used(EVE),in tissue engineering room to give adipose tissue biomechanics by negative pressure suction to achieve the effect of in situ regeneration of adipose tissue.ASCs plays an important role in adipose tissue regeneration induced by biomechanics.The purpose of this study was to change the biomechanical effect of EVE device and compare the migration and adipogenic differentiation of ASCs,and to compare the function of ASCs in different mechanical environments and the ability of long-term fat regeneration in combination with adipose tissue acellular matrix.Methods and resultsThe unilateral inguinal fat flap of SD rats was transferred to the middle of abdomen by transposition.The biomechanical size of EVE device(3 KPA,6 KPA)was set up and negative pressure suction was performed 12 hours after valve rotation.The attraction time was 12 hours a day,and the samples were collected on the 1st,3rd,5th,7th and 9th day.Immunofluorescence showed that the cells of CD34+in the two groups increased the most on the first day(6kPa)and the third day(3kPa),respectively.Then ASCs labeled with CM-DiI was injected around the fat flap of the two groups before the 1st and 3rd day respectively.in the same way,the materials were collected on the 1st and 3rd day.Immunofluorescence showed that the larger the biomechanics,the more the number of ASCs migration,the faster the speed,and the more proteins related to migration.However,histological staining of adipose tissue showed that the greater the biomechanical effect,the higher the degree of long-term fibrosis and the lower the expression of adipogenic related proteins.Then the finite element analysis of the stiffness of adipose tissue under different biomechanics was carried out,and it was found that the higher the biomechanics,the higher the stiffness of adipose tissue.Therefore,the above findings may be due to changes in the stiffness of adipose tissue.Therefore,we originally mixed the acellular matrix of adipose tissue with different proportions of methylcellulose to prepare acellular matrix gels with different stiffness.The gel was injected into nude mice to compare the migration and fat regeneration of ASCs.The results showed that the higher the stiffness,the more ASCs migrated in the early stage,but only the gel with stiffness close to adipose tissue had the strongest fat regeneration ability in the long term.this part of the results also verified the findings of the first part.Conclusions1)Biomechanics can induce ASCs migration from surrounding tissue and participate in adipose tissue regeneration;2)There is an optimum number of new ASCs in participating tissues,and too many ASCs will cause tissue fibrosis;3)The greater the biomechanical effect is,the more the tissue stiffness increases,and the higher the tissue stiffness is,the more ASCs are recruited.4)The closer the tissue stiffness was to normal adipose tissue,the stronger the adipogenic ability of ASCs was;5)There may be an optimal range of mechanical induction in EVE model to promote ASCs migration while maintaining appropriate tissue stiffness and promoting adipose tissue regeneration. |
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