Different Rate SVF-gel Mixed With Fat Promoted Retention Of Grafts In Fat Transplantation

Background:Autologous fat grafting is considered as not only an ideal filler but also a stem cell therapy,thus it became more widely application.However,the unstable and low retention rate of grafts as well as the formation of duration limited the further application of fat transplantation.In our recent researches a novel adipose tissue-derived injectable Extracellular Matrix/Stromal Vascular Fraction Gel(ECM/SVF-gel)prepared by shearing force was described and used in promoting wound healing because of enriched growth factors and stem cells.The further investigation shown that SVF-gel not only was therapeutically effective in wound healing,but also had a high long-term retention rate after transplantation.The SVF-gel is thought as safer assister for fat transplantation because of its mechanical process.However,the output rate of SVF-gel isolated from fat is low(<15%),so we need to find a suitable proportion of SVF-gel mixed with fat in transplantation.Methods1.Preparation of Coleman adipose tissue and SVF-gelAbdominal or femoral fat tissues were harvested with a 3 mm multiport cannula.After standing for 10 min in ice water,the fat layer was centrifuges at 1200 g for 3 min to get Colman fat.SVF-gel was prepared as described in previous research Briefly,the Colman fat was shuffles between two 10 ml syringes by a Luer-lock connector with an internal diameter of 2.4 mm for 1 min.After processing,the emulsified Coleman fat was centrifuged at 2000 g for 3min.Finally,the sticky substance under the oil layer was SVF-gel.2.Fat/SVF-gel transplantationFemale nude mice(n=90;age 5-6 weeks)were housed in individual cages with a 12-h light/dark cycle and provided with standard food and water.According to the different mixing ratio of Fat/SVF-gel(fat,20%gel + 80%fat,40%gel + 60%fat,60%gel ?40%fat,80%gel + 20%fat,gel),the 90 nude mice were divided into 6 groups(n=15/group).Fat/SVF-gel(0.3 ml/point)was subcutaneously injected into the 4 quadrants of nude mouse back with a 1 ml syringe.3 animals in each group were sacrificed at 7,14,30,60 and 90 days after transplanting to harvest the grafts.The volumes of grafts were measured and then used in Histological examination and Immunofluorescent staining.Result1.There was no significant difference of appearance in all groups on 7 days.Obvious oil sacs were presented in fat and mixed fat/SVF-gel groups except gel group at 60 and 90 days.Moreover,the texture of grafts became harder with the decease rate of gel in grafts.The retention of grafts in all group decreased with time.However,the retention of grafts was highest in gel group,lowest in fat group from 30 days to 90 days(p<0.05).There was no signification of the retention of the 4 mixed fat/SVF-gel groups(p>0.05).By 90 days,most of the vascularized connective tissue in the grafts had been replaced by mature adipocytes,with a structure similar to that of normal tissue in all groups,but grafts in high rate(60%and 80%)gel and gel groups had greater tissue integrity and fewer oil cysts,whereas grafts in low rate(20%and 40%)and fat groups contained large areas of necrosis in their centers and numerous large oil cysts.Conclusion1.The retention volume and quality of SVF-gel grafts was significant higher than fat grafts,.2.SVF-gel promotes the retention rate and quality of fat grafts when they were mixed transplantation.3.The low rate gel in grafts played the role of cellular therapy4.The SVF-gel showed the significant regeneration at a high rate in grafts.5.Due to the low productivity of SVF-GEL,according to different requirements of fat transplantation clinically to join different proportions of SVF-GEL,with a minimum of SVF-GEL to achieve the best clinical effect.