PDGFRα and CD51 Mark Human Nestin+ Sphere-Forming Mesenchymal Stem Cells Capable of Robust Hematopoietic Stem Cell Expansion

Abstract 505 Few markers have thus far been identified on native mesenchymal stem cells (MSCs), both in the mouse and human systems. Most markers cited in the literature are indeed based on expression analyses on heterogeneous cultured cell populations, which may not have self-renewal properties if rigorously tested by transplantation assays. Previous studies using Nestin (Nes)-Gfp transgenic mice showed that Nes-GFP+ cells are self-renewing MSCs, a major constituent of the hematopoietic stem cell (HSC) niche in the bone marrow (BM) (Nature 2010; 466:829). However, the cytoplasmic location of Nestin precludes prospective live cell isolation outside of the transgenic mice. Hence, finding a combination of surface markers labeling Nestin+ cells in situ would be valuable to isolate bona fide MSCs and characterize niche cells. Screening analyses toward this end revealed that PDGFRα and CD51 expression among CD45− Ter119− CD31− BM stromal cells comprised a large fraction (∼60%) of Nes-GFP+ cells. Upon gating first on PDGFRα+ and CD51+, double-positive cells were also highly enriched in Nes-GFP+ cells (∼75%), and represented a rare fraction (∼2%) of the stromal population. Endogenous Nestin expression was also enriched in PDGFRα+ CD51+ cells, compared to single-positive or double-negative stromal cells (control subsets). Cell sorting of BM PDGFRα+ CD51+ and control subsets revealed that PDGFRα+ CD51+ significantly enriched (> 10-fold, p 7-fold, p Disclosures: No relevant conflicts of interest to declare.