Are MicroRNAs Associated with the Chondrogenic Potency of Equine Cord Blood Mesenchymal Stromal Cells?

Mesenchymal stromal cells (MSCs) can be easily harvested from a variety of tissues and are capable of differentiating down a number of mesodermal and non-mesodermal cell lineages in vitro. These properties make MSCs a promising cell source for restorative and/or regenerative applications such as tissue repair in animals and humans. However, MSCs are a heterogeneous cell population and large inter-donor variation in their differentiation potential, particularly their chondrogenic capacity, has been reported. This attribute may hamper the development of reproducible therapies and the use of MSCs in research and regenerative medicine. Moreover, underlying molecular mechanisms governing the heterogeneity of the chondrogenic differentiation potential of culture expanded MSCs remain poorly understood. In this study, we sought to identify miRNA signatures as potential prognostic biomarkers associated with chondrogenic differentiation potential of MSC cultures in the equine model. Equine cord blood-derived MSC (CB-MSC) cultures were initially evaluated for their ability to produce cartilage in a standard chondrogenic differentiation assay. The chondrogenic differentiation potential was scored and categorized based on histological extra-cellular matrix formation and quantification of glycosaminoglycan deposition. Subsequently, total RNA of CB-MSCs were used for identification of miRNAs associated with high and low chondrogenic potency of CB-MSCs via next generation sequencing (NGS). A total of 12 miRNA libraries were sequenced: 6 with high and 6 with low chondrogenic potential. We identified as many as 30 differentially expressed miRNAs based on chondrogenicity, including miR-146a-5p, miR-183-5p and miR-203a-3p. Consistent with previous reports, SMAD4 is targeted by miRNAs that are upregulated in CB-MSCs with low chondrogenicity. Predicted KEGG pathways include “TGF-beta signaling pathway”, “proteoglycans in cancer” and “adherens junction”. In conclusion, microRNA profiling of CB-MSC cultures may have prognostic value in selecting MSC donors with regards to their chondrogenic differentiation potential and their future utility in cartilage tissue engineering or cell therapy strategies.