Secretome analysis of human mesenchymal stem cells undergoing chondrogenic differentiation

Human mesenchymal stem cells (hMSCs) can be triggered to differentiate toward chondrocytes and thus harbor great therapeutic potential for the repair of cartilage defects in osteoarthritis (OA) and other articular diseases. However, the molecular mechanisms underlying the chondrogenesis process are still in part unknown. In this work, we followed a double-stable isotope labeling by amino acids in cell culture (SILAC) strategy to evaluate the quantitative modulation of the secretome of stem cells isolated from bone marrow (hBMSCs) during the first steps of their chondrogenic differentiation. Analysis by LC-ESI-MS/MS led to the identification of 221 proteins with a reported extracellular localization. Most of them were characteristic of cartilage extracellular matrix, and 34 showed statistically significant quantitative alterations during chondrogenesis. These include, among others, cartilage markers such as Proteoglycan 4 or COMP, anticatabolic markers (TIMP1), reported markers of cartilage development (Versican), and a suggested marker of chondrogenesis, CRAC1. Altogether, our work demonstrates the usefulness of secretome analysis for understanding the mechanisms responsible for cartilage matrix formation, and it reports a panel of extracellular markers potentially useful for the evaluation of tissue development in cell therapy- or tissue engineering-based approaches for cartilage repair.