No abstract

Currently, there are no established treatments to prevent, stop, or even retard the degeneration of articular cartilage in osteoarthritis (OA). Biological repair of the degenerating articular cartilage would be preferable to surgery. There is no benign site where autologous chondrocytes can be harvested and used as a cell source for cartilage repair, leaving mesenchymal stem cells (MSCs) as an attractive option. However, MSCs from OA patients have been shown to constitutively express collagen type X (COL-X), a marker of late-stage chondrocyte hypertrophy. We recently found that naproxen (Npx), but not other nonsteroidal anti-inflammatory drugs, can induce collagen type X alpha 1 (COL10A1) gene expression in bone marrow-derived MSCs from healthy and OA donors. In this study, we determined the effect of Npx on COL10A1 expression and investigated the intracellular signaling pathways that mediate such effect in normal human MSCs during chondrogenesis. MSCs were cultured in standard chondrogenic differentiation media supplemented with or without Npx. Our results show that Npx can regulate chondrogenic differentiation by affecting the gene expression of both Indian hedgehog and parathyroid hormone/parathyroid hormone-related protein signaling pathways in a time-dependent manner, suggesting a complex interaction of different signaling pathways during the process.

Osteoarthritis (OA) is a disease of diarthrodial joints associated with extracellular matrix proteolytic degradation under inflammatory conditions, pain and disability. Currently, there is no therapy to prevent, reverse or modulate the disease course. The present study aimed at evaluating the regenerative potential of Link N (LN) in human OA cartilage in an inflammatory milieu and determining if it could affect pain-related behaviour in a knee OA mouse injury model. Osteo-chondro OA explants and OA chondrocytes were treated with LN in the presence of interleukin-1β (IL-1β) to simulate an osteoarthritic environment. Quantitative von Frey polymerase chain reaction and Western blotting were performed to determine the effect of LN on matrix protein synthesis, catabolic enzymes, cytokines and nerve growth factor expression. Partial medial meniscectomy (PMM) was performed on the knee of C57BL/6 mice and, 12 weeks post-surgery, mice were given a 5 µg intra-articular injection of LN or phosphate-buffered saline. A von Frey test was conducted over 24 h to measure the mechanical allodynia in the hind paw. LN modulated proteoglycan and collagen synthesis in human OA cartilage through inhibition of IL-1βinduced biological effects. LN also supressed IL-1β-induced upregulation of cartilage-degrading enzymes and inflammatory molecules in OA chondrocytes. Upon investigation of the canonical signalling pathways IL-1β and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), LN resulted to significantly inhibit NF-κB activation in a dose-dependent manner. In addition, LN suppressed mechanical allodynia in an OA PMM mouse model. Results supported the concept that LN administration could have therapeutic potential in OA.