Efficient isolation of bone marrow adipocyte progenitors by silica microbeads incubation.

Excessive bone marrow adipocytes (BMAs) formation is tightly associated with development of osteoporosis. Considering the high heterogeneity of bone marrow stromal cells (BMSCs), identification of bone marrow adipocyte progenitors (BMAPs) within heterogeneous BMSCs may provide better cellular models for research regarding osteoporosis development and therapy. However, currently there is no efficient method or specific surface makers that are available for BMAPs isolation. In the current study, we developed a novel BMAPs isolation method based on silica microbeads incubation and subsequent centrifugation in ficoll-paque. The "Sca-1(+)CD73(-)CD90(-)CD105(+)" subpopulation selected by this method exhibited significantly stronger adipogenic potential than nonselected BMSCs in vitro and could homogeneously differentiate into mature adipocytes within 4 days. Moreover, these cells also highly expressed a series of adipogenesis-related genes even before differentiation. After long-term culture, however, BMAPs would gradually lose high adipogenic ability, but sorting CD105(+) cells from BMAPs in later passages was able to retrieve the highly adipogenic subpopulation. In conclusion, this study demonstrated that BMAPs subpopulation could be effectively isolated from heterogeneous BMSCs by a special silica microbeads incubation method and re-enriched by sorting CD105(+) cells. These findings offer convenient and repeatable approaches to obtain pure BMAPs for research regarding pathogenic mechanisms and therapeutics development of osteoporosis.