M. R. Borrelli1, C. Blackshear1, S. Vistnes1, R. Patel1, M. Longaker1, D. C. Wan1 1Stanford University,Palo Alto, CA, USA
Introduction: Adipose-derived stromal cells (ASCs) are cells isolated from the stromal vascular compartment of adipose tissue with extensive proliferative capacity and multilineage differentiation abilities. These characteristics make them strong candidate cells in regenerative medicine. Recent work indicates that ASCs are a heterogeneous mix of cells, and are comprised of multiple stem and progenitor subpopulations. Further elucidation of the exact identity and regenerative capacities of each of the ASC subpopulations can help to develop therapies able to target specific regenerative processes.
Methods: We previously identified a subpopulation of ASCs positive for the surface marker CD146. Flow cytometry was used to isolate CD146+ ASCs from human lipoaspirate samples (n=3). Gene expression analysis was compared between CD146+ and CD146- ASC populations, and unsorted fat cells, for a number of proangiogenic (ANGPT1, VEGF, FGF) and adipogenic (PPARg, LPL, FABP4) factors. To explore in vivo regenerative potential, freshly isolated CD146+ ASCs were also injected into the subcutaneous tissue overlying the scalp of recipient immunodeficient mice. Graft retention was followed by CT scanning every two weeks for a total of 12 weeks, at which point mice were sacrificed and the fat grafts were explanted and procssed for histology and confocal microscopy.
Results: CD146+ ASCs showed a significant upregulation of VEGF and LPL expression compared to unsorted fat cells and CD146- cells (*p > 0.05, ***p > 0.005) (Figure 1.A). CD146+ and unsorted fat cells had significantly higher graft retention volumes compared to CD146- ASCs and fat alone. Transplantation of fat alone resulted in the poorest graft retention (Figure 1.B). Fat grafts isolated from mice transplanted with CD146+ ASCs showed the greatest CD31 immunofluorescent staining, and the greatest graft vascularization in confocal microscopy.
Conclusion: We have identified a subpopulation of ASCs positive for the surface marker CD146 with enhanced angiogenic effects. These effects are likely mediated by increased expression of proangiogenic factors such as VEGF. This work suggests that enriching lipoaspirates with CD146+ ASCs may enhance fat graft vascularization and retention in the clinical setting.
