| BackgroundAutologous fat transplantation has gradually played an increasingly important role in the field of plastic surgery and repair due to its rich source and easy access.As an important soft tissue filling and repair material,the unpredictable retention rate of fat grafting has been plaguing many scholars.Moreover,the mechanism of survival and regeneration of adipose tissue in the body is not yet fully clear.Structural fat transplantation and the 3M(multipoint,multitunnel,and multilayer)injection technique have been confirmed the significant role of tissue fluid infiltration in autologous fat transplantation.However,in clinical work,especially in large-volume fat transplantation,grafted fat tend to gather into clusters,which hinders the infiltration of tissue fluid,leading to fat necrosis and the formation of cyst nodules.ObjectiveThis study explored the role in the process of fat grafting through in vitro prefabricated microparticle fat grafts(PFMG),verifying its growth and development of adipocytes in vitro and observing graft retention in vivo.To determine the effects of adipocyte cell morphology,retention rate,vascularization,fibrosis,necrosis and apoptosis in the process of fat transplantation,thus providing a better understanding of the theory of fat grafting and a new solution for clinical work.MethodsThe C57BL/6 mouse fat particles were embedded in growth factor-reduced(GFR)-Matrigel to detect cell migration under light microscope and explore the type of migrated cells by immunofluorescence staining in vitro.PFMG was prepared by mixing mouse fat particles and GFR Matrigel in a 1:1 volume ratio and injected subcutaneously into C57BL/6 mice.Simple fat particle grafting served as a control.The grafts were harvested at 1,4,8,and 12 weeks after sacrifice.The retention rate and the gross appearance of grafts at each time point were measured.Adipose tissue morphology,fibrosis,vascularization,necrosis,and apoptosis were evaluated by histological analysis.ResultsCD34+cells migrated from the PFMG and formed a tree-like tubular network in the in vitro study.The retention rate was higher in the PFMG group than in the control group at week 12(38%vs.30%,p<0.05).In the first week,HE staining showed the morphology of the PFMG experimental group was similar to that of the control group,oil cysts were more and larger in the control group than in the PFMG group.The oil cysts were absorbed quickly and the GFR Matrigel was displaced by adipose tissue in the PFMG group with time,however,in the control group,the oil cysts were maintained at a high level.Nevertheless,By semi-quantitative analysis of inflammatory cells infiltration and fibrosis level,the control group was much higher than the PFMG experimental group and that was statistically significant.TUNEL assay and HIF-la detection effectively verified the improvement of early hypoxia environment,more sufficient tissue fluid infiltration,and less cell apoptosis in the experimental group.The increase of VEGF level in the early stage effectively promoted the increase of CD31+cells,which is related to vascularization,and effectively improved the retention rate of grafted fat.Conclusion1.In vitro composite microparticles of fat graft effectively improved the late volume retention rate.2.Effective infiltration of tissue fluid is the key to the early survival of transplanted fat.In vitro composite microparticles of fat graft can improve the infiltration of tissue fluid,alleviating the ischemia and hypoxia microenvironment,and reducing adipocyte apoptosis.3.In vitro composite microparticles of fat graft promote the migration of ADSCs and achieve early vascularization after grafting,and improve the retention rate of grafts.4.Due to better vascularization as soon as possible,it is conducive to more macrophage infiltration,promotes the absorption of oil sacs,and retard the production of fibrosis. |
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