Investigation of the mechanisms of diabetic vitreoretinopathy and its pharmaceutical regulation

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Diabetic retinopathy including diabetic macular edema is considered to be caused not only by the pathological change of the retina but also by that of the vitreous. Therefore, the pathological condition should be considered as diabetic vitreoretinopathy rather than simply as diabetic retinopathy. However, precise mechanisms are not fully understood to date.We are focusing on the functional change of hyalocytes (a macrophage lineage in the vitreous cavity) and retinal vascular endothelial cells under the pathological conditions. In addition, we suppose that rho-kinase might be a possible therapeutic target for the treatment of diabetic vitreoretinopathy. In the present study, we used Fasudil which is a rho-kinase inhibitor already in clinical use fro the treatment of erebrovascular spasm.We previously reported that Fasudil could be able to inhibit the cicatrical contraction of proliferative membrane using cultured hyalocytes. The critical association of connective tissue growth factor ( … More CTGF), which is thought to be one of the downstream mediators of transforming growth factor-beta (TGF-beta), with vitreoretinal diseases remains to be clarified. In the present study, we first demonstrated the correlation between the concentrations of TGF-beta2 and CTGF in the vitreous, and CTGF gene regulation in cultured hyalocytes. Concentrations of TGF-beta2 and CTGF in the vitreous from patients with proliferative vitreoretinal diseases were significantly higher than those with non-proliferative 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-beta2,associated with nuclear accumulation of Smad4. The TGF-beta2-dependent Smad4 translocation and CTGF gene expression were mediated through Rho kinase and at least partially via p38 MAPK. Fasudil inhibited both of Smad4 translocation and CTGF gene expression. In conclusion, combined effects of TGF-beta2 and CTGF appear to be involved in the pathogenesis of proliferative vitreoretnal 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.Vascular endothelial growth factor (VEGF) plays pivotal roles in the pathogenesis of angiogenesis. In this study, we addressed the therapeutic potential of fasudil for VEGF-elicited angiogenesis and also its intracellular signaling. VEGF-elicited angiogenesis in corneal micro-pocket assay was potently attenuated by co-embedding with fasudil (p<0.01). VEGF caused MLC phosphorylation of BRECs, which was almost completely abrogated by fasudil. VEGF-dependent phosphorylation of ERK1/2 and Akt were also significantly abrogated by the treatment with fasudil without affecting VEGFR2 (KDR) phosphorylation. Moreover, both VEGF-induced [3H]-thymidine uptake and migration of BRECs were significantly inhibited in the presence of fasudil. These findings indicate that fasudil might have therapeutic potential for ocular angiogenic diseases. The anti-angiogenic effect of fasudil appears to be mediated through the blockade not only of Rho-kinase signaling but also of ERK and Akt signalings. Less