Anabolic actions of IGF-I and TGF-beta1 on Interleukin-1beta-treated human articular chondrocytes: evaluation in two and three dimensional cultures.

Pro-inflammatory cytokines, such as interleukin-1beta (IL-1beta) and tumor necrosis factor-alpha (TNF-alpha) play a key role in the pathogenesis of Osteoarthritis (OA). The aim of this study was to investigate the potential anti-inflammatory properties of the growth factors IGF-I and/or TGF-beta1 on IL-1beta signalling pathways and their effect on the chondrogenic potential of dedifferentiated human articular chondrocytes in vitro. Serum-starved human articular chondrocytes were treated with IL-1beta to induce dedifferentiation and further treated with IGF-I and/or TGF-beta1 at various concentrations. The effects of growth factors were evaluated both in monolayer and high-density cultures. Incubation with the cytokine IL-1beta resulted in rapid dedifferentiation of the cells; they lost their chondrocyte-like phenotype while down-regulating the expression of collagen type II, integrin, extracellular regulated kinase (Erk 1/2) and the chondrogenic transcription factor Sox9. Co-treatment with IGF-I and/or TGF-beta1 stimulated the cells to redifferentiate, increasing the expression of the above-mentioned cartilage-specific proteins. These events correlated with down-regulation of cyclooxygenase-2 (COX-2) and matrix metallo-proteinase-13 (MMP-13). Furthermore, in high-density cultures, we observed evidence for new cartilage formation after co-treatment with these growth factors. We further detected that all examined proteins were more strongly expressed during combination treatment. These results indicate that IGF-I and TGF-beta1 exert additive anabolic effects on chondrocytes and may stabilize the chondrogenic potential. The additive action of these growth factors on chondrocytes may find practical applications in the fields of OA and cartilage tissue engineering.