MiR-184 exhibits angiostatic properties via regulation of Akt and VEGF signaling pathways

Abstract

Corneal avascularity is critical for achieving transparency necessary for proper transmission of light to the lens and visual acuity. Although much is known about angiogenesis and angiostasis, the precise regulation of these processes in the cornea is unclear. MicroRNA (miR)-184, the most abundant corneal epithelial miRNA, has been suggested to function in corneal angiostasis by altering VEGF signaling; however, the mechanism(s) underlying this regulation have not been addressed. Using a combination of in vitro and in vivo assays to evaluate angiogenesis, we demonstrated that human limbal epithelial keratinocytes (HLEKs) engineered to overexpress miR-184 secretedlower amounts of angiogenicmitogens.Humandermalmicrovascular cells exposedto conditioned mediumfrommiR-184-overexpressingHLEKswere lessproliferative andfailed to seal linear scratchwounds.The in vivoMatrigel plug assay showed that conditionedmedium frommiR-184-expressing HLEKs elicited a lesser degree of neovascularization comparedwith controls.WefoundthatmiR-184 directly targets andrepresses the proangiogenic factors, friend of Gata 2 (FOG2), platelet-derived growth factor (PDGF)-b, and phosphatidic acid phosphatase 2b (PPAP2B).FOG2regulatesVEGFexpression,whereasPDGF-βandPPAP2B regulate Akt activity. By attenuating both VEGF and Akt signaling, miR-184 acts as a broad-spectrum negative regulator of corneal angiogenesis.