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Qinbo Zhou, Ashwath Jayagopal, Shusheng Wang; Functional study of microRNA-24 in ocular angiogenesis. Invest. Ophthalmol. Vis. Sci. 2013;54(15):1244.
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© ARVO (1962-2015); The Authors (2016-present)
Actin cytoskeleton is critical for cell motility and proliferation, both of which are important for angiogenesis. MicroRNAs (miRNAs or miRs) are important posttranscriptional regulators of gene expression, and are emerging as pivotal modulators of vascular development and disease. Currently, miRNAs are rapidly advanced as novel therapeutic targets for several diseases. How miRNAs regulate actin cytoskeleton dynamics in endothelial cells (ECs) and angiogenesis is still unclear. Our recent studies have shown that miR-23 and miR-27 in miR-23~27~24 family are required for proper angiogenesis and choroidal neovascularization (CNV). Here we test the hypothesis that miR-24 regulates ocular angiogenesis through modulating actin dynamics in ECs by targeting multiple components downstream of Rho signaling.
In vitro Matrigel assay, time-lapse living cell imaging, novel transgenic mouse model, laser injury AMD model, and in vivo miRNA mimic delivery methods were used to dissect the function of miR-24 in angiogenesis, ocular vascular development and laser-induced CNV.
Our in vitro and in vivo results provide comprehensive evidence that miR-24 plays an important role in ocular angiogenesis by regulating multiple critical components in actin cytoskeleton dynamics. Overexpress of miR-24 in ECs blocked stress fiber and lamellipodia formation, represses ECs migration, proliferation and tube formation in vitro. Overexpression of miR-24 inhibited EC cell tube formation in Matrigel and angiogenic vessel sprouting in an ex vivo aortic ring assay. We also generated miR-24 transgenic mice and found that the development of superficial vascular plexus is delayed upon miR-24 overexpression in mice. Moreover, the adult miR-24 transgenic mice also lack the deep layers of vascular plexus. Consistently, therapeutic subretinal delivery of miR-24 mimics potently repressed laser-induced CNV in vivo. Mechanistically, miR-24 represses angiogenesis by regulating PAK-LIMK-Cofilin pathway. Knockdown of miR-24 target gene LIMK2 or PAK4 inhibited stress fiber formation and tube formation in vitro, mimicking miR-24 overexpression phenotype.
These findings demonstrate that miR-24 represses ocular angiogenesis by simultaneously regulating multiple components in the actin cytoskeleton pathways. Manipulation of actin cytoskeleton pathways by miR-24 may represent an attractive therapeutic solution for treatment of wet AMD and other vascular diseases.
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