Impact of 3D Culture Systems for Mesenchymal Stromal Cells on the Secretion of Growth Differentiation Factor 5 and the Implications for Cartilage Regeneration

The poor regenerative capacity of articular cartilage and the limited efficacy of current treatments in restoring its extracellular matrix contribute to osteoarthritis. This study investigated an emerging approach using the secretome of mesenchymal stromal cells (MSC) to stimulate chondrocyte-driven cartilage matrix synthesis. MSC from human bone marrow (hBM-MSC) and Wharton’s jelly (hWJ-MSC) were cultured in various 3D culture systems, including spheroids, alginate beads, porous collagen scaffolds and bilayer collagen membranes in vitro. Conditioned medium (CM) was collected and analyzed for anti-inflammatory and trophic factors via ELISA. Furthermore, the CM was applied to human chondrocytes (hCh), which were assessed for chondrogenic and osteogenic gene expression and histologically stained for type II collagen (COL II) and sulfated glycosaminoglycans (sGAG). hCh cultured in chondrogenic differentiation medium served as a control. MSC remained viable in all four application models. Growth differentiation factor 5 (GDF-5) release was significantly increased for hWJ-MSC compared to hBM-MSC. Anti-inflammatory factors remained undetectable in the present setup. CM of 3D cultivated MSC differently affected chondrogenic differentiation of chondrocyte pellets, with CM of spheroids showing higher effects compared to the other three application models. This study demonstrates that the secretion of cytokines by MSC is strongly affected by the microenvironment of the cells.