Chondroitin Sulfate Microparticles Modulate TGF-β1-Induced Chondrogenesis of Human Mesenchymal Stem Cell Spheroids

摘要

Mesenchymal stem cells (MSCs) have been previously explored as a part of cell-based therapies for repair of damaged cartilage. Current MSC chondrogenic differentiation strategies employ large pellets, however, we have developed a technique to form small MSC aggregates (500–1,000 cells) that can reduce transport barriers while maintaining a multicellular structure analogous to cartilaginous condensations. The objective of this study was to examine the effects on chondrogenesis of incorporating chondroitin sulfate methacrylate (CSMA) microparticles (MPs) within small MSC spheroids cultured in the presence of transforming growth factor-β1 (TGF-β1). Spheroids +MP induced earlier increases in collagen II and aggrecan gene expression (chondrogenic markers) than spheroids -MP, although no large differences in immunostaining for these matrix molecules were observed by day 21 between these groups. Collagen I and X were also detected in the ECM of all spheroids by immunostaining. Interestingly, histology revealed that CSMA MPs clustered together near the center of the MSC spheroids and induced circumferential alignment of cells and ECM around the material core. This study demonstrates the use of CSMA materials to further examine the effects of matrix molecules on MSC phenotype, as well as potentially direct differentiation in a more spatially controlled manner that better mimics the architecture of specific musculoskeletal tissues.