Transforming growth factor-β2 and connective tissue growth factor in proliferative vitreoretinal diseases: Possible involvement of hyalocytes and therapeutic potential of rho kinase inhibitor

The critical association of connective tissue growth factor (CTGF), which is thought to be one of the downstream mediators of transforming growth factor-β (TGF-β), with vitreoretinal diseases remains to be clarified. In the current study, we first demonstrated the correlation between the concentrations of TGF-β2 as well as CTGF in the vitreous and CTGF gene regulation in cultured hyalocytes. Concentrations of TGF-β2 and CTGF in the vitreous from patients with proliferative vitreoretinal diseases were significantly higher than in those with nonproliferative diseases, and there was a positive correlation between their concentrations (r = 0.320, P < 0.01). Cultured hyalocytes expressed CTGF mRNA, which was enhanced in the presence of TGF-β2, associated with nuclear accumulation of Smad4. TGF-β2- dependent Smad4 translocation and CTGF gene expression were mediated through Rho kinase and at least partially via p38 mitogen-activated protein kinase. Finally, fasudil, a Rho kinase inhibitor already in clinical use, inhibited both Smad4 translocation and CTGF gene expression. In conclusion, combined effects of TGF-β2 and CTGF appear to be involved in the pathogenesis of proliferative vitreoretinal diseases. Hyalocytes may be a possible source of CTGF and thus might play a role in vitreoretinal interface diseases. Furthermore, Rho kinase inhibitors might have therapeutic potential to control fibrotic disorders in the eye.