Abstract
Bone marrow-derived stromal cells (BMSCs) are defined by their ability to self-renew and differentiate into at least three mesenchymal cell types (bone, adipose, and cartilage). The inability to isolate a reliably efficacious and homogeneous population of early progenitor cells has limited efforts to increase their therapeutic potential. In this study, we focused on identifying protein markers that may be employed to predict the efficacy of a cultured BMSC population. Markers of progenitor status were identified by comparing BMSCs at early and late passage, donor-matched skin fibroblasts, and commercially available dermal fibroblast cell lines. Differentiation potential was determined according to in vitro assays of osteogenesis, adipogenesis, and chondrogenesis. Early-passage BMSCs differentiated into all three lineages, whereas late-passage BMSCs and both fibroblast preparations did not. To identify novel markers of early progenitors, microarray transcript analysis between early-passage BMSCs and fibroblasts was performed. Messenger RNA encoding the cytokine leukemia inhibitory factor (LIF) was identified as differentially expressed. Enzyme-linked immunosorbent assay on conditioned media confirmed that LIF secretion was much higher from early progenitor BMSCs than donor-matched or commercial lines of fibroblasts and dropped with extensive expansion or induction of differentiation. In clonally expanded BMSCs, colonies that retained progenitor status expressed significantly higher levels of LIF than those that failed to differentiate. Our results indicate that LIF expression may represent a marker to quantify the differentiation potential of BMSCs and may be especially suited for the rapid, noninvasive quality control of clinical preparations.