Identification of predictive markers for human mesenchymal stromal cells chondrogenic potential is challenged by donor variability

Human bone marrow derived mesenchymal stromal cells (BMSCs) represent a putative cell source candidate for tissue engineering based strategies to repair cartilage and bone. However, traditional isolation of BMSCs by their preference to adhere to plastic leads to very heterogeneous cell populations and may account for high inter-donor variability and unpredictability of chondrogenic differentiation out-come. Identification of a cell fraction with higher chondrogenic capacity and reduced variance in basic chondrogenic differentiation could further aid the process for developing BMSC-based cartilage and bone regeneration approaches. Since single cell derived clones isolated from fresh bone marrow aspirates show a broad range of chondrogenic capacity, we assessed whether the gene expression profile of clones with high and low chondrogenic capacity differs. While a clustering between high and low chondrogenic capacity clones was observed for one donor, donor-to-donor variability drastically hampered the possibility to achieve conclusive results when different donors were considered. NCAM1/CD56 as identified by the transcriptomic analysis of one donor was still up-regulated in clones with higher chondrogenic capacity and we showed that enriching expanded multiclonal BMSCs for CD56+ expression led to an increase in chondrogenic capacity, though still highly affected by donor-to-donor variability. Our study finally suggests that the definition of predictive marker(s) for BMSCs chondrogenesis is challenged by the high donor’s heterogeneity of these cells. Moreover, we hypothesis that multiple pathways may be involved in determining the chondrogenic potential of BMSCs, making the identification of putative markers still an open issue.