Role of microRNAs in retinal neovascularization

© 2018 Dr Jiang Hui WangMicroRNAs (miRNAs) are master gene regulators that have been widely implicated in many biological processes as well as pathogenesis of many diseases in the eye. The identification of miRNAs that are altered in human diseases as well as in animal models has led to new avenues to develop novel therapeutic targets for ocular disorders. The broad focus of studies described in this thesis is the identification of miRNAs that have altered expression during neovascularization of the retina using a rat model of oxygen-induced retinopathy (OIR). miRNA-Seq studies carried out in rats, mice and humans show that retinal miRNAs in rats and mice are highly homologous with humans. In exploring the altered miRNAs in retinal neovascularization, we found four miRNAs of interest (miR-143, miR-126, miR-150 and miR-145) that were down-regulated in the retina preceding neovascularization in OIR rats. Further investigation suggested that transforming growth factor-beta activated kinase 1 (TAK1), a target gene of miRNA-143, was highly up-regulated in the retina of OIR rats. Selectively pharmacological inhibition of TAK1 activity by 5Z-7-Oxozeaenol led to significant reduction of angiogenic capability of human endothelial cells, as measured by cell proliferation, cell migration and tube formation. Moreover, 5Z-7-Oxozeaenol greatly suppressed vascular spouting of mice aortic explants. In vivo intravitreal administration of 5Z-7-Oxozeaenol profoundly attenuated the retinal neovascularization in OIR rats. Previous studies have reported the down-regulation of miR-126 and miR-150 in OIR mice, and the restoration of these altered miRNAs led to significant suppression of retinal neovascularization in vivo. Here we focus on miR-143 rather than miR-126 and miR-150 to explore its therapeutic potential and underlying mechanisms in retinal neovascularization. Intravitreal administration of a synthetic miR-143 mimic into the eyes of OIR rats suppressed retinal neovascularization by ~50%. Further RNA-Seq identified that a gene cluster mediated by Fos, an inflammatory and stress gene, plays a crucial role in the suppression of retinal neovascularization in OIR rats by the restoration of miR-143. Plasmid vectors of reporter genes and corresponding elements of altered miRNAs such as miR-143, miR-126 and miR-150 were devised. Co-transfecting the devised plasmids with corresponding mimic of the altered miRNAs in HEK293A cells inhibited reporter gene expression. In the context of gene therapy for retinal neovascularization, the results indicate that therapeutic gene expression could be regulated in accordance with the disease activity through altered miRNAs