Effect of MSCA1 expression on characteristics and functionality of mesenchymal stromal cells

The therapeutic potential of mesenchymal stromal cells (MSC) has been shown in multiple diseases. However, the heterogeneity of MSC and thus the existence of MSC subpopulations may influence their potency. Among other markers, mesenchymal stem cell antigen-1 (MSCA1) can be used to distinguish subpopulations. Since this marker is associated with the regulation of different cellular programs, the effect of MSCA1 expression levels on MSC characteristics and functionality was investigated.

MSC subpopulations were sorted by FACS according to their MSCA1 expression. Applied sort criteria were 5-10% of MSC with highest or lowest expression (MSCA1 high or low). Control groups included the overall MSC population, either exposed to the FACS procedure (Sort Ctrl) or untreated (Ctrl). The MSC were expanded for two passages. Basic expansion parameters, cell viability, and the differentiation potential were analyzed. The expression of identity (CD73, CD90, CD105), purity (CD14, CD34, CD45, MHC II), and additional markers (e.g., MSCA1, CD146) was determined. Functional analyses included secretion of bioactive molecules (e.g., ACTH, Osteopontin (OPN), Tumor necrosis factor-inducible gene 6 (TSG-6)) and inhibition of T cell proliferation.

No differences were obtained between the groups regarding basic MSC characteristics (viability, potential for ex vivo expansion, differentiation potential, expression of identity and purity markers). A stable expression of MSCA1 could be shown which remained significantly higher for MSCA1 high compared to MSCA1 low for two passages. Moreover, the expression of CD146 was significantly increased for MSCA1 high, while the expression of other markers was unaffected. An altered secretome of MSC subpopulations was indicated by a significantly higher secretion of OPN and ACTH by MSCA1 low and TSG-6 by MSCA1 high, respectively (Figure 1). No difference in the inhibitory potential of T cells was observed between MSCA1 high and low subpopulations.

MSC subpopulations could be distinguished by MSCA1 expression with consistent basic MSC characteristics. Altered properties were observed regarding the secretion of factors relevant for e.g., bone formation or wound healing. Gene expression analyses are ongoing to further elucidate potential differences in the potency of MSC subpopulations. This may help in improving the efficiency of MSC therapy by selecting for subpopulations with distinct features, thereby reducing the heterogeneity of MSC.

The authors declare no commercial, proprietary or financial interest. VJ, KG, SE, MR and HS received funding from the Bundesministerium für Verteidigung, the European Union"s Seventh Framework Programme and the European Union"s Network HORIZON2020. The materials presented and views expressed here are the responsibility of the authors only. The European Union Commission takes no responsibility for any use made of the information set out.