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Involvement of Rho-Kinase Pathway in Contractile Activity of Rabbit RPE Cells In Vivo and In Vitro

From the Department of Ophthalmology, Osaka University Medical School, Osaka, Japan.

PURPOSE. Increased -smooth muscle actin (-SMA) expression in epiretinal membranes causes tractional retinal detachment (TRD) in proliferative vitreoretinopathy (PVR). The Rho-A/Rho-associated kinase signaling pathway is a principal mediator of contractile force generation in nonmuscle cells. In the current study, the relation between the Rho-kinase pathway and -SMA expression and type I collagen gel contractile activity in retinal pigment epithelial (RPE) cells was investigated, using Y27632, a specific inhibitor of p160ROCK, and the involvement of the Rho-kinase pathway was evaluated in a rabbit PVR model with cultured RPE cells and platelet-rich plasma (PRP).

METHODS. RPE cells were obtained from rabbits and cultured. The number of passages and the effect of Y27632 on -SMA expression were studied by immunohistochemistry and immunoblot analysis. An in vitro type I collagen gel contraction assay and MTT assay evaluated the effect of Y27632 on RPE cell contractile force and proliferation. Cultured sixth-passage rabbit RPE cells were coinjected with PRP intravitreally, followed by 50 µM of Y27632, injected weekly. The presence of TRD was assessed until 28 days to evaluate the effect of Y27632 in vivo.

RESULTS. Expression of -SMA was increased according to the passages. Y27632 suppressed -SMA expression in cultured RPE cells and impaired contractile force. Y27632 did not affect the proliferative potential. Y27632 significantly (P < 0.01) reduced TRD development.

CONCLUSIONS. Y27632 decreased -SMA expression and the contractile force generated by RPE cells and attenuated PVR, indicating the involvement of the Rho-kinase pathway in cell-dependent collagen contraction in vitro and in vivo. The drug may affect the biological event by inhibiting -SMA expression, and Y27632 could be useful for preventing PVR.

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