Human bone marrow-derived MSCs spontaneously express specific Schwann cell markers

In peripheral nerve injuries, Schwann cells (SC) play pivotal roles in regenerating damaged nerve. However, the use of SC in clinical cell-based therapy is hampered due to its limited availability. In this study, we aim to evaluate the effectiveness of using an established induction protocol for human bone marrow derived-MSC (hBM-MSCs) transdifferentiation into a SC lineage. A relatively homogenous culture of hBM-MSCs was first established after serial passaging (P3), with profiles conforming to the minimal criteria set by International Society for Cellular Therapy (ISCT). The cultures (n = 3) were then subjected to a series of induction media containing β-mercaptoethanol, retinoic acid, and growth factors. Quantitative RT-PCR, flow cytometry, and immunocytochemistry analyses were performed to quantify the expression of specific SC markers, that is, S100, GFAP, MPZ and p75 NGFR, in both undifferentiated and transdifferentiated hBM-MSCs. Based on these analyses, all markers were expressed in undifferentiated hBM-MSCs and MPZ expression (mRNA transcripts) was consistently detected before and after transdifferentiation across all samples. There was upregulation at the transcript level of more than twofolds for NGF, MPB, GDNF, p75 NGFR post-transdifferentiation. This study highlights the existence of spontaneous expression of specific SC markers in cultured hBM-MSCs, inter-donor variability and that MSC transdifferentiation is a heterogenous process. These findings strongly oppose the use of a single marker to indicate SC fate. The heterogenous nature of MSC may influence the efficiency of SC transdifferentiation protocols. Therefore, there is an urgent need to re-define the MSC subpopulations and revise the minimal criteria for MSC identification.