CD36 Identifies a Subpopulation of Adipose-Derived Mesenchymal Stromal Cells with Enhanced Osteogenic Ability.

Abstract Background Adipose-derived mesenchymal stromal cells (AMSCs) represent attractive cellular therapeutics for treatment of various diseases including osteoarthritis and bone degeneration. Preparation and characterization of AMSCs show donor-to-donor variability that indicating that AMSCs are heterogeneous populations of cells. Cell surface markers to identify MSCs, such as CD44, CD90, and CD105, are relatively invariable among AMSCs and do not reflect the heterogeneity of AMSC populations. CD36, a multifunctional surface receptor associated with transport of oxidized low-density lipoproteins and fatty acids, is also expressed by AMSCs but this marker is considerable more variable. Therefore, we assessed whether CD36 can be used to identify subpopulations in AMSCs. Methods Clinical-grade AMSCs were isolated from patient fat biopsies, cultured under xenobiotic-free conditions using human platelet lysate and sorted by flow cytometry or magnetic cell sorting to characterize CD36 expression. CD36 enriched, CD36 depleted, and unsorted AMSCs were characterized using cellular and molecular techniques including proliferation, multilineage potential, RNA-sequencing and bioinformatics, metabolomics, and sensitivity to the CD36 inhibitor sulfosuccinimidyl oleate (SSO). Results CD36 exhibited biphasic expression on AMSCs grown in human platelet lysate. Enrichment of CD36+ AMSCs showed that CD36+ expression identifies a stable subpopulation. Transcriptomic analysis revealed enhancement of calcium transporter genes. Osteogenic differentiation of CD36+ enriched, CD36+ depleted, and unsorted AMSCs showed strikingly enhanced osteogenic calcium deposition and enhanced expression of alkaline phosphatase (ALPL) and osteoprotegrin (TNFRSF11B) in the CD36+ population. While lipid droplets were not altered, adipogenic differentiation showed upregulated gene expression of key adipogenic markers, including fatty acid-binding protein 4 (FABP4) and Adiponectin (ADIPOQ), with CD36+ enrichment. Treatment of CD36+ enriched AMSCs with the SSO showed reduced calcium deposition whereas CD36+ depleted AMSCs were unaffected. Conclusions CD36 exhibits variable expression amongst AMSCs. CD36+ enriched AMSCs are a stable subpopulation with enhanced osteogenic potential that linked to CD36 receptor function. These results may further refine production and clinical application of AMSC cellular therapeutics. Furthermore, the enhanced osteogenic potential of CD36+ AMSCs may be considered for therapeutic regeneration of bone.