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Factors contained in the expansion medium regulate the expression stem cell markers CD146 and SUSD2 on human placenta‐derived mesenchymal stromal cells and modulate their differentiation capacity in vitro

Human mesenchymal stromal cells (MSCs) are investigated in vitro and in vivo manifold to serve as cellular therapy in different clinical situations including the regeneration of muscular tissues eventually. For production of MSCs for experimental purposes expansion media often include fetal bovine serum (FBS) as source of growth factors. In clinical situations xenogenic components such as FBS must be avoided in many countries. Therefore, different xeno‐free MSC expansion media were developed and FBS was replaced e.g. by human serum (hS), platelet lysate (hPL) or hPL plus human plasma (hPLP). However, differences in these medium complements could influence the phenotype and characteristics of MSCs. We therefore compared the expression of cell surface markers, the differentiation capacity and the expression of key cytokines involved in muscular regeneration in human placenta‐derived MSC‐like cells (pMSCs) expanded in different xeno‐free and GMP‐compliant expansion media. We report that addition of 5% hPL to either commercial MSC expansion medium (medium with FBS + 5% hPL) or to GMP‐compliant MSC expansion medium (DMEM + 5% hS + 5% hPL) significantly increased the MSC proliferation (p<0.05), and reduced the expression of CD146 (p<0.05), whereas CD73 and CD90 and other markers remained unchanged, on both transcript and protein levels. Expression of stem cell marker SUSD2 was not significantly regulated by hPL. The osteogenic differentiation capacity was reduced in pMSCs expanded in medium complemented with 5% hP + 5% hPL when compared to pMSCs incubated in medium containing FBS without hPL, but not in DMEM + hS compared to DMEM+ hS + hPL. Significant changes in the expression of neuro‐ or myo‐regenerative cytokines including BDNF, bFGF, GDNF, HGF, IGF‐1, IGF‐2, TGFβ, or VEGF in MSCs was not influenced by the composition of the GMP‐compliant expansion media. However, some interindividual differences between pMSCs from individual donors and between batches of hPL were noted. In contrast, the composition of expansion media did not influence osteogenesis or expression of stem cell markers CD146 and SUSDA on human bone marrow‐derived MSCs. We conclude that the expression of CD146 and the osteogenic differentiation potential of human pMSCs is influenced by the expansion medium. The expression of the regenerative cytokines investigated was not biased by hPL in the expansion medium. Expansion of pMSCs in GMP‐compliant medium enriched by hP + hPL could therefore be an advantage when bone formation by the MSCs applied should be avoided in clinical situations.