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.