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C. B. Del Debbio, M. F. Santos, C. Y. I. Yan, I. Ahmad, D. E. Hamassaki-Britto; Role of Rho GTPases in Ciliary Epithelium Proliferation. Invest. Ophthalmol. Vis. Sci. 2008;49(13):4897. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Rho GTPases are important proteins in signaling pathways that regulate gene transcription, cell survival, and cell proliferation. We have previously shown that RhoA, Rac1 and Cdc42 were diffusely expressed in retinal progenitor ciliary epithelial (CE) cells, whereas RhoB was seen in pars plana (Del Debbio CB, et al. IOVS 2007; 48: ARVO E-Abstract 3065). The aim of the present study was to determine the possible role of Rho GTPases on the proliferation of mouse retinal progenitor CE cells.
Adult Balb/c mice were anesthetized and CE cell proliferation was induced by intraocular co-injections of bFGF (100ng/eye) and insulin (2µg/eye) or TGF-β signaling inhibiting cocktail (blocking the ligands 1, 2 and 3, 5µg/eye; and receptor II, 1.25µg/eye). Rho GTPases were activated by LPA (1µM) or inactivated by Toxin A (10ng/eye). PBS was used as control. All animals received subcutaneous injections of 100µl of 10 mg/ml bromodeoxyuridine (BrdU) daily. After four days of injections, the animals were sacrificed and the retinas processed for immunofluorescence analysis with the antibodies against RhoA, RhoB and Rac1, markers for proliferation (BrdU, Ki67) and progenitor cells (Pax6, Chx10 and Nestin).
Whereas no proliferation was observed in CE cells after PBS injection, an increase was seen after bFGF and insulin or TGFβ inhibitors treatments (2-fold higher than the control). Rho GTPases inhibition by Toxin A alone or together with bFGF and insulin increased the percentage of immunoreative Ki67 cells (7- and 11-fold higher, respectively). On the other hand, the proliferation induced by TGFβ inhibitors was reduced to control levels after Rho GTPases activation by LPA.
Our findings suggest that Rho GTPases may act as negative controllers for cell proliferation since their inhibition potentiate the effects of bFGF and insulin, and their activation reduced the proliferation induced by blockage of TGFβ signaling.
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