MicroRNAs are prognostic markers for the chondrogenic potential of MSCs

Purpose: The capacity of mesenchymal stromal cells (MSCs) to differentiate into chondrocytes as well as to function as trophic mediators restoring joint homeostasis make them a promising cell source for a disease modifying treatment in osteoarthritis. MSCs can be easily harvested from various locations of the body, including amongst others bone marrow, periosteum, synovium, synovial fluid, adipose tissue, buccal fat pad, infrapatellar fat pad and osteoarthritic cartilage. MSCs are a heterogeneous cell population and large inter-donor variation with respect of the chondrogenic potential of these cells has been reported which may hamper clinical application. Presently, prognostic markers predicting the chondrogenic differentiation potential of culture expanded MSCs derived from multiple donors are lacking. The objective of this study is to identify such prognostic markers.

Methods: In this study 20 human MSC donors were tested for their ability to produce cartilage in a standard chondrogenic differentiation assay consisting of pellet culture in the presence of serum free medium and TGFβ. Cartilage formation was scored on the basis of histological matrix formation, mRNA expression levels of chondrogenic marker genes and quantification of glycosaminoglycan deposition. Of each of these donors genome wide mRNA expression profiles were obtained using an affymetrix microarray platform before the onset of differentiation. In addition, small nucleotide RNAs were isolated for miRNA profiling using a panel of miRNAs previously implemented in chondrogenesis.

Results: Only 3 donors out of 20 were identified as donors with high chondrogenic potential, whereas 9 showed moderate and 8 low chondrogenic potential. Despite these huge differences in chondrogenic potential, genome wide mRNA profiling at the onset of differentiation showed only marginal differences between the 3 groups. In contrast, profiling of microRNAs (miRNAs) previously implemented in chondrogenesis and cartilage homeostasis showed a very distinctive pattern between good and bad performing donors. We also studied the changes in miRNA expression during a 7 day differentiation period of MSCs in pellet culture and identified miR-210 and miR-630 as positive regulators of chondrogenesis with miR-630 as a potential marker for high performing donors. In contrast miR-181 and miR-34a, both of which are negative regulators of chondrogenesis, were up-regulated during differentiation in bad performing donors.

Conclusions: In contrast to the marginal differences at the global mRNA level between good and bad MSC donors with respect of chondrogenic differentiation potential, screening of a panel of miRNAs previously implemented in cartilage formation showed more clear segregation between good and bad performing donors. MiRNA profiling of MSC donors may, therefore, have prognostic value to select MSC donors with respect of their chondrogenic differentiation potential and their capacity to restore cartilage homeostasis after intra-articular injection in the osteoarthritic joint.