A novel compressive stress-based osteoarthritis-like chondrocyte system

Mechanical stress damage and insufficient self-repair can contribute to osteoarthritis (OA) in the affected joint. As the effects of stress on chondrocyte metabolism can regulate cartilage homeostasis, the specific stress-response condition is therefore a key to the generation of an OA disease model. We aimed to produce a specific stress- and cell-based OA model after evaluating the metabolic responses of chondrocytes in response to a series of static and cyclic compression stressors. A static load exceeding 40 psi initiated extracellular matrix (ECM) degradation through a decrease in the sulphated-glycosaminoglycan (GAG) content, upregulation of catabolic matrix metalloproteinase (MMP)-13 encoding gene expression, and downregulation of the ECM-related aggrecan and type II collagen encoding genes within 24 h. Indicators of pro-inflammatory events and oxidative stress were found to correlate with increased IL-6 expression and reactive oxygen species (ROS) production, respectively. However, chondrocytes stimulated by moderate cyclic loading (30-40 psi) exhibited increased ECM-related gene expression without significant changes in catabolic and pro-inflammatory gene expression. BMP-7 expression increased at cyclic loading levels above 30-60 psi. These results demonstrated that static compression exceeding 60 psi is sufficient to produce OA-like chondrocytes that exhibit signs of ECM degradation and inflammation. These OA-like chondrocytes could therefore be used as a novel cell-based drug screening system. Impact statement The lack of an effective treatment for osteoarthritis (OA) reflects the great need for alternative therapies and drug discovery. Disease models can be used for early-stage compound screening and disease studies. Chondrocytes are solely responsible for the maintenance of the articular cartilage extracellular matrix. Our strategy involved the generation of a cell-based model of OA, a more readily studied disease. Instead of using animal cartilage explants, we incorporated isolated porcine chondrocytes with hydrogel to form three-dimensional assemblies. We could identify the specific magnitude-dependent metabolic responses of chondrocytes by applying a series of static and cyclic compression, and therefore successfully generated a novel OA-like cell-based model for drug screening.

Effect of chondroitin sulphate C on the in vitro and in vivo chondrogenesis of mesenchymal stem cells in crosslinked type II collagen scaffolds

This study evaluates the crosslinkage effect of chondroitin sulphate C (CSC) and type II collagen (COL II) on chondrogenesis of mesenchymal stem cells (MSCs) in vitro and in vivo. In the in vitro studies, our results show that the weight ratio CSC:COL II that reaches 1.2:100 (CSC1.2/100 -COL II scaffold) can provide an optimal microenvironment for MSC chondrogenesis. When MSCs are cultured in this CSC1.2/100 -COL II scaffold, the chondrogenic gene expression of cultured cells is upregulated, while the osteogenic gene expression of these is downregulated. In addition, MSCs cultivated in the CSC1.2/100 -COL II scaffold are found to express the highest glycosaminoglycans:DNA ratio as compared to those in scaffolds of other CSC:COL II ratios. Histological and immunohistological evidence also supports the result. In the in vivo study, our results show that MSCs cultivated in the CSC1.2/100 -COL II scaffold demonstrate a better repair ability on cartilage lesions than does the COL II scaffold. After 1 month in vivo, the injected MSCs in the CSC1.2/100 -COL II scaffold show lacuna structures and stimulate the formation of type II collagen at the defective sites. Six months after transplantation, the generated cells in the CSC1.2/100 -COL II group show higher gene expressions of type II collagen and aggrecan but lower gene expression of type I collagen at the defective sites than those in the COL II group. The results strongly suggest that CSC1.2/100 -COL II scaffold can serve as a potential candidate for cartilage repair and improve the chondrogenesis of MSCs in general.