Resveratrol regulates type II collagen and COX-2 expression via the ERK, p38 and Akt signaling pathways in rabbit articular chondrocytes.

Resveratrol, a naturally occurring polyphenolic phytoalexin antioxidant compound present in grapes and red wine, has been reported to induce various biochemical responses. It has been shown to possess anti-aging, anti-inflammatory and anti-proliferative activities in several cell types. However, the effects of resveratrol in normal cells, including chondrocytes, have not yet been clearly elucidated. The aim of the present study was to evaluate the effects of resveratrol on differentiation and inflammation in rabbit articular chondrocytes and to investigate the underlying mechanism of action. Rabbit articular chondrocytes were treated with 20 µM resveratrol for different time periods or with various concentrations of resveratrol for 24 h. It was observed that the expression levels of type II collagen and sulfated proteoglycan, as determined by western blot analysis and Alcian blue staining, respectively, increased following treatment with resveratrol in a concentration-dependent manner at concentrations up to 20 µM and then decreased at higher concentrations. The expression levels of cyclooxygenase (COX-2) and prostaglandin E2 (PGE2) began to increase at 10 min after the addition of resveratrol, reached peak levels at 3 h and decreased from the peak level thereafter, as determined by western blot analysis and PGE2 assay, respectively. It was also demonstrated that resveratrol caused phosphorylation of mitogen-activated protein kinase proteins [extracellular signal-regulated kinases (ERK), p38 and c-Jun N-terminal kinases (JNK)] and Akt in rabbit articular chondrocytes. The inhibition of ERK, p38 kinase, phosphoinositide 3-kinase (PI3K) and Akt with PD98059, SB203580, LY294002 and triciribine, respectively, suppressed resveratrol-induced type II collagen and COX-2 expression. However, inhibition of JNK with SP600125 produced no clear changes in the expression levels of type II collagen and COX-2. The results suggest that resveratrol in articular chondrocytes stimulates differentiation and inflammation via the ERK, p38 and Akt signaling pathways.

The effect of sonication on simulated osteoarthritis. Part I: effects of 1 MHz ultrasound on uptake of hyaluronan into the rabbit synovium.

High molecular weight (MW) hyaluronan (HA) preparation is considered to be more biologically active than HAs of lower MWs. However, many of the HA preparations currently used to treat osteoarthritis (OA) have lower MWs by the enhanced penetration of HA molecules into the synovial lining cells. In this study, we determined the effectiveness of sonophoresis on the delivery of high MW HA into synovial membrane using an animal model of OA. A total of 1000 kDa (HA1000) and 3000 kDa (HA3000) HA were labeled with fluorescein and injected into the knees of rabbits. Low-intensity continuous ultrasound at 1 MHz, 400 mW/cm2 was applied to the knees for 10 min treatment bid. Synovial fluid analysis revealed increased absorption and fluorescence microscopy showed deeper penetration of both HA1000 and HA3000, more so with the latter. Histologic examination indicated that ultrasound treatment resulted in no apparent damage to the synovial membrane. These results suggest that simultaneous sonication with HA injection might compensate for the short half-life of HA. Consequently, this dual treatment would render HA a far more effective tool in the management of OA.

The effect of sonication on simulated osteoarthritis. Part II: alleviation of osteoarthritis pathogenesis by 1 MHz ultrasound with simultaneous hyaluronate injection.

In our previous study, we demonstrated the effects of ultrasound (US) on the delivery of hyaluronan (HA) into the synovium, even at molecular sizes as high as 3000 kDA. We hypothesized that a combined therapy with US and HA would have synergistic effects on alleviating the pathogenesis of osteoarthritis (OA). In the present study, we evaluated the effectiveness of sonication on the progress of induced OA in rabbits. We measured the cartilage degradation and inflammation, synovial fluid amount along with protein content and, finally, performed histologic analyses of the integrity of the cartilage and synovium. Low-intensity continuous US at 1 MHz, 400 mW/cm2 was applied to the knees for 10 min bid. Combined treatment with US and HA most strikingly reduced total synovial fluid volume and also significantly alleviated the OA-induced accretion of total protein, proteoglycan and prostaglandin E2 in the synovial fluid. It also attenuated the release of collagen type II and matrix metalloproteinase-3 in the OA-induced joint to normal levels. Histopathology revealed that combined HA and US treatment also reduced the severity of OA-induced structural damages in the cartilage and synovium. The effectiveness of HA with regard to the alleviation of OA pathogenic changes can be greatly enhanced by the simultaneous treatment with HA and US.