BMPR-1A+ Adipose-Derived Stromal Cells Demonstrate Enhanced de novo Adipogenesis
Elizabeth R. Zielins, MD, R. Chase Ransom, M.D., Elizabeth A. Brett, M.S., Charles P. Blackshear, M.D., Graham G. Walmsley, M.D., Ph.D., Siddarth Menon, B.S., John Flacco, B.S., Siny Shailendra, B.S., Clement D. Marshall, M.D., Tripp Leavitt, B.S., Arash Momeni, M.D., Michael T. Longaker, M.D., M.B.A., Derrick C. Wan, M.D..
Stanford University, Stanford, CA, USA.
Purpose: Within the stromal vascular fraction of lipoaspirate resides a heterogeneous population of adipose-derived stromal cells (ASCs) with potential for de novo adipogenesis. Importantly, previous reports have demonstrated signaling through BMP receptor type 1A (BMPR-IA) to promote adipogenic lineage commitment among mesenchymal cells. In this study, we evaluated the ability for the BMPR-IA subpopulation of ASCs to undergo enhanced formation of mature adipocytes.
Methods: Freshly harvested human stromal cells were separated into BMPR-IA+ and BMPR-IA- fractions using magnetic-activated cell separation and flow cytometry was performed to confirm enrichment. These cells, along with unsorted cells, were then cultured in adipogenic differentiation medium for 7 days followed by Oil-Red-O staining and gene expression analysis. Cells from each group were also labeled with a GFP lentivirus and transplanted into the inguinal fat pads of immunocompromised mice for evaluation of de novo adipocyte formation within a natural adipogenic niche.
Results: Oil-Red-O staining showed significantly more lipid droplet formation in BMPR-IA+ cells (*p<0.05), and this was paralleled by increased expression of FABP4 (*p<0.05), a marker of terminal adipogenic differentiation, among BMPR-IA+ cells. Confocal microscopy of explanted inguinal fat pads demonstrated significantly more mature GFP+ adipocytes formed by BMPR-IA+ cells compared to BMPR-IA- and unsorted stromal cells (**p<0.01).
Conclusions: BMPR-IA+ stromal cells show greater adipogenic ability both in vitro and in vivo. Enrichment for BMPR-IA+ cells may thus identify a subpopulation with increased utility in soft tissue restorative procedures where inclusion of pro-adipogenic stromal cells (e.g. cell-assisted lipotransfer) may enhance reconstructive outcomes.
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