Engineering a chondrogenic microenvironment to promote MSC chondrogenesis
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Osteoarthritis (OA) is characterized by the degradation of articular cartilage and affects 27 million people in the US. Mesenchymal stem cells (MSCs) are a promising cell source for OA therapies because of their immunomodulatory properties and ability to be differentiated along a chondrogenic lineage. Traditional chondrogenic differentiation of MSCs relies on using growth factors such as TGF-βs, but cells rapidly undergo hypertrophy and are not able to withstand the same mechanical load as healthy hyaline cartilage. Decellularized cartilage contains important growth factors and extracellular matrix (ECM) proteins to support chondrogenesis at physiologically relevant concentrations and may be an alternative or additive to improve chondrogenic differentiation. The objective of this study was to investigate whether digested cartilage ECM incorporation into MSC pellets could improve chondrogenic differentiation alone or in combination with exogenous growth factors such as TGF-β1. Porcine articular cartilage was decellularized and then digested in pepsin to form an ECM digest. The ECM digest was incorporated into 250,000 cell pellets at various concentrations to determine an appropriate dose. The ECM digest was then subsequently incorporated into MSCs with and without the addition of TGF-β1. The chondrogenic TGF-β1 treated control with no additional ECM was negative for glycosaminoglycan (GAG) staining after 21 days in culture, so subsequent experiments investigated the role of donor-to-donor variability, passage number, and media composition in affecting MSC chondrogenic differentiation. Chondrogenic differentiation of MSC pellets had better glycosaminoglycan (GAG) content with TGF-β3 induction compared to TGF-β1, but this differentiation was greatly limited in multiple donors with high (>p4) passage number. Future studies will compare ECM addition with chondrogenic induction of MSCs from earlier passages.