The Mechanism And Prospect In Clinical Practice Of CXCL12 Attracting ASCs To Promote The Preferential Repair In Donor Site Of Fat Grafting

BackgroundThe unpredictable and unstable tissue retention rate of autologous fat grafting remains an obstacle faced by plastic surgeons.Adipose-derived stem cells,a multi-pluripotent stem cells within adipose tissue,play key role in the homeostasis and tissue repair process both physiologically and pathologically.Many researches potentiate the outcomes of fat grafting by exogenous addition or promoting the viability of endogenous ASCs.Conventionally,experimental model of fat grafting contains only the recipient site while clinically,the surgery on donor site is nonnegligible.It has been unveiled that liposuction in the donor site crippled the retention rate of grafts in recipient site compared with that in mice only received tissue grafting in recipient site.The reparative cells infiltrated the donor site first while cell infiltration and tissue repair in recipient site was delayed.Notably,ASCs infiltration in recipient site was also delayed.This triggered our questions:what causes the differential infiltration of ASCs?Tissue released lots of chemokines after injury,which mediates the influx of cells.Chemokine CXCL12 exerts functions through binding to receptor CXCR4 and CXCL12/CXCR4 is the most studied chemokine axis to attract stem cells.It has been demonstrated that,ASCs expressed CXCR4 and there is an upregulation of CXCL12 after adipose tissue damage.Based on the above,we refer to a mice model with donor site which resemble clinical autologous fat grafting.We attempt to explore the mechanism of delayed ASCs infiltration in recipient site of autologous fat grafting through testing the CXCL12/CXCR4 expression in donor and recipient site.Then focused on that,we intend to modulate ASCs infiltration to promote adipose tissue repair and upregulate grafts retention rate.Methods and ResultsFirstly,we clamped the inguinal fat pads of C57/BL6 mice and transferred adipose tissue on the back simultaneously to create autologous fat grafting model with donor site.We test the expression of CXCL12/CXCR4 and found that the expression of CXCL12/CXCR4 in donor site was significantly higher than that in recipient site early after autologous fat grafting.Immunofluorescence showed that there were significantly more CD34+ASCs in the donor than in recipient site early after surgery.The consistency between CXCL12/CXCR4 expression in the donor and recipient site and ASCs activity indicated CXCL12/CXCR4 to be the mechanism behind the differential infiltration of ASCs.Next,we established CXCL12+AMD3100-Group,CXCL12-AMD3100+Group,and CXCL12+AMD3100+Group basing on the autologous fat grafting mice model with donor site to modulate the effect of CXCL12 in the donor and recipient site in comparison with the Control(CXCL12-AMD3100-).The general look,retention rate and tissue structures of grafts 90 days after surgery showed CXCL12+AMD3100+Group efficiently promote ASCs infiltration in recipient to accelerate tissue repair and obtain a better grafts retention rate.However,solely upregulated CXCL 12 in recipient site could not promote ASCs infiltration as we expected.Surprisingly,blocking CXCL12 in donor site using AMD3100 could accelerate ASCs infiltration and obtain a better retention rate.Stepping forward,we explored the role of blood perfusion using a Normal/Ischemic mice model in which we test the expression of CXCL12/CXCR4 and immunofluorescence for CD34,PERILIPIN in adipose tissue in Normal and Ischemic adipose tissue 3,7,14 and 30 days after surgery.We found CXCL12/CXCR4 expressed higher in Normal than in Ischemic adipose tissue;consistently,there were more ASCs infiltrating Normal than Ischemic adipose tissue within 7 days after surgery.Conclusion1.Higher expression of CXCL12 in donor site than in recipient site early after autologous fat grafting induces early infiltration of ASCs in donor site and that in recipient site is postponed,which results in relatively poor tissue repair;2.Blocking the effect of CXCL12 in donor site can accelerate ASCs infiltration in recipient site to promote tissue repair and fat graft retention rate;3.Blood perfusion is an important source of CXCL12 which stressed the importance of early angiogenesis after grafting form a new aspect;4.Early angiogenesis is essential for CXCL12 promoting adipose tissue repair in recipient site.