Adipose Extracellular Matrix/Stromal Vascular Fraction Gel Secretes Angiogenic Factors And Enhances Skin Wound Healing In A Murine Model

BackgroundWound healing is a highly complex process that remains a major challenge in modern medicine.Among the factors contributing to these nonhealing conditions,impairment of cytokine production and reduced vascularization play crucial roles.Mesenchymal stem cells-(MSCs-)based cytotherapy is an attractive approach in wound healing due to the differentiation potential,immunomodulating properties,and paracrine properties.Adipose-derived stem cells(ASCs)are promising candidates for cytotherapy because they can be easily harvested from adipose tissue and are abundant in number.However,isolation of ASCs still requires enzymatic digestion,which increases the risk of biological contamination.Additionally,in vitro culture and expansion of ASCs require specific laboratory experience and can take days to weeks.Moreover,in most studies,ASCs suspensions are injected separately without the protection of extracellular matrix(ECM)compo-nents,leading to rapid elimination of ASCs by the immune system and subsequent poor cell retention at recipient sites.All of these factors weaken the therapeutic effects and applications of ASCs-based cytotherapy.We have recently described a novel adipose-tissue-derived injectable extracellular matrix/stromal vascular frac-tion gel(ECM/SVF-gel).Taking advantage of shearing force to selectively break mature adipocytes,the ECM/SVF-gel eliminates most of the lipids and other unwanted components of adipose tissue,leaving only the extracellular matrix(ECM)and SVF cells and greatly improving ASCs density.Because ECM/SVF-gel is rich in ASCs,we speculated that ECM/SVF-gel may exert cytotherapy effects on wound healing.To test this hypothesis,preliminary studies were conducted in a mouse excisional wound healing model to assess the therapeutic value of ECM/SVF-gel for wound repair.Methods and resultsFirst,angiogenic factors expression and angiogenic effect of ECM/SVF-gel extract in vitro were tested.Next,angiogenic factors secretion and angiogenic efficacy of the grafted ECM/SVF-gel in vivo were examined.Finally,the inflammation level of ECM/SVF-gel in vivo was evaluated.ECM/SVF-gel was prepared for use in nude mouse excisional wound healing model.SVF cell suspension and phosphate-buffered saline injection served as the control.The expression levels of vascular endothelial growth factor(VEGF),basic fibroblast growth factor(bFGF),and monocyte chemotactic protein-1(MCP-1)in ECM/SVF-gel were analyzed at different time points.Angiogenesis(tube formation)assays of ECM/SVF-gel extracts were evaluated,and vessels density in skin was determined.The ECM/SVF-gel extract promoted tube formation in vitro and increased the expression of the angiogenic factors VEGF and bFGF compared with those in the control.The expression of the inflammatory chemoattractant MCP-1 was high in ECM/SVF-gel at the early stage and decreased sharply during the late stage of wound healing.The potent angiogenic effects exerted by ECM/SVF-gel may contribute to the improvement of wound healing,and these effects could be related to the enhanced inflammatory response in ECM/SVF-gel during the early stage of wound healing.ConclusionsIn this study,we preliminarily verify the potential mechanisms underlying the efficacy of ECM/SVF-gel therapy on wound healing in a murine model.The results revealed that the therapeutic effect of ECM/SVF-gel is mainly attributed to the secretion of angiogenic factors and promotion of vascularization,and this process could be related to the intense inflammatory response in ECM/S VF-gel during the early stage of wound healing.Besides,the protective effects of the ECM component on attached ASCs in ECM/SVF-gel may also contribute to the enhanced angiogenic response and final wound healing process.