The Cell Surface Proteome of Human Mesenchymal Stromal Cells

Background: Multipotent human mesenchymal stromal cells (hMSCs) are considered as promising biological tools for regenerative medicine. Their antibody-based isolation relies on the identification of reliable cell surface markers. Methodology/Principal Findings: To obtain a comprehensive view of the cell surface proteome of bone marrow-derived hMSCs, we have developed an analytical pipeline relying on cell surface biotinylation of intact cells using cell impermeable, cleavable sulfo-NHS-SS-biotin to enrich the plasma membrane proteins and mass spectrometry for identification with extremely high confidence. Among the 888 proteins identified, we found approximate to 200 bona fide plasma membrane proteins including 33 cell adhesion molecules and 26 signaling receptors. In total 41 CD markers including 5 novel ones (CD97, CD112, CD239, CD276, and CD316) were identified. The CD markers are distributed homogenously within plastic-adherent hMSC populations and their expression is modulated during the process of adipogenesis or osteogenesis. Moreover, our in silico analysis revealed a significant difference between the cell surface proteome of hMSCs and that of human embryonic stem cells reported previously. Conclusions/Significance: Collectively, our analytical methods not only provide a basis for further studies of mechanisms maintaining the multipotency of hMSCs within their niches and triggering their differentiation after signaling, but also a toolbox for a refined antibody-based identification of hMSC populations from different tissues and their isolation for therapeutic intervention.