The Study Of Promoting Ischemic Random Skin Flap Vascularization Via Hydrogel Based Biological Scaffolds

ObjectivesIn recent years,a lot of researches on accelerating ischemic tissues vascularization by preparation of a variety of biomaterials with different physical and chemical properties obtained good effect.However,biomaterials with the different physical and chemical properties used in different types of tissues and organs have different effects on vascularization.Hydrogel with controllable physical and chemical properties can be prepared under mild conditions.Distal and complete necrosis of skin flap is always clinical problematic in plastic surgery.Therefore,in this study,we explored acceleration vascularization and promoting skin flap survival by application of several kinds of funtion hydrogel scaffolds.Methods1.Two typical nanofibrous membranes of synthetic(poly(L-lactide))and natural(gelatin)materials were fabricated by electrospinning.The morphology,surface wettability was to characterize,and infuence on human dermal fbroblasts(HDFs)and human umbilical vein endothelial cells(HUVECs)survival were investigated in vitro by SEM and cell activity assay.In vivo,two kinds of nanofibrous membranes infuence on the random skin flap survival in a rat model was investigated by hemodynamic and histology detection.2.We synthesized an ultraviolet(UV)photocrosslinkable gelatin hydrogel and then fabricate the hydrogel nanofibrous membrane by electrospinning.We investigated the morphology,water retention,and mechanical and degradation properties of the fibrous membranes in vitro.Additionally,the ability of Gel MA nanofibrous membrane for cellular adhesion,proliferation,and secretion,as well as vascularization,was also evaluated in vitro.In order to explore the potential of the Gel MA nanofibrous membrane for promoting random skin flap survival applications,in vivo blood supply and vascularization were also investigated in a rat model.3.The in situ-forming dextran hydrogel were fabricated and the interior morphologies of the hydrogels was detected by SEM analysis.The cytotoxicity and biocompatibility of the dextran hydrogel on stem cell was evaluated by Cryo-SEM,Live/Dead staining and CCK-8 assay.Pluripotency and vascularization related growth factors expression of dextran hydrogel on ADSCs was further explored using Immunofluorescent staining,RT-PCR,Elisa and other methods.In vivo experiments ADSCs were delivered into ischemic skin flaps by using hydrogel.The rate of engraftment and survival of donor cells were assessed by noninvasive optical bioluminescence,and the promoting vascularization consequences of transplantation were determined by morphological and histological analysis.Results1.The results in the present work indicated that gelatin electrospun nanofibrous membranes possessed a better hydrophilicity with a stable fibrous structure.HDFs and HUVECs adhered better to the gelatin fiber than to the PLLA fibers and showed a better vitality in the gelatin fiber.In a rat model,after 7 days of implantation,blood perfusion of the flap treated with gelatin membrane was higher than other groups.From histology tests,in comparison to PLLA,gelatin did not cause severe inflammation reaction and allowed the formation of new blood vessels.2.It is observed that the optimized hydrogel scaffolds could support endothelial cells and dermal fibroblasts adhesion,proliferation,and migration into the scaffolds,which facilitated vascularization.After Gel MA fibrous scaffold implantation below the skin flap in a rat model,it was found that the flap survival rate was higher than the control group,and there was more microvascular formation,which was potentially beneficial for the flap tissue vascularization.3.When tested in vitro,the in situ-forming dextran hydrogel significantly increased cell survival,expression of stemness genes and paracrine effects by provided a functionalized micro-niche for ADSCs.After transplanted in a random flap model of nude mice,this engineered cellular constructs not only promoted ADSCs retention,but also stimulated quick vascularization.ConcludionsThis study preliminarily proved that preparing hydrogel scaffold which was high simulation of extracellular matrix could improve the skin tissue regeneration and was beneficial to the formation of local microvascular.Furthermore,after loading ADSCs,the hydrogel could improve ADSCs survival miro-environment against harmful factor and cell survival rate,which could be utilized as an attractive strategy for ischemic random skin flap vascularization.