MicroRNA-216b actively modulates diabetic angiopathy through inverse regulation on FZD5

Background: In this work, we examined the angiogenic function of microRNA-216b in an in vitro rat diabetic model of myocardial microvascular endothelial cells (MMECs). Methods: MMECs were extracted from Wistar rats (MMEC(WI)) or diabetic Goto-Kakizaki (GK) rats (MMEC(GK)) and cultured in vitro. QRT-PCR was applied to compare miR-216b between MMEC(WI) and MMEC(GK). MiR-216b was downregulated in MMEC(GK). Its effects on angiogenic development, including invasion and proliferation, were evaluated. In MMEC(GK), putative miR-216b downstream target gene, frizzled class receptor 5 (FZD5), was evaluated by dual-luciferase reporter, qRT-PCR and western blot assays, respectively. FZD5 was further downregulated in MMEC(GK) with stable miR-216b downregulation to evaluate its functional role in regulating diabetic angiogenesis. Results: MiR-216b was markedly overexpressed in MMEC(GK). MiR-216b downregulation significantly enhanced angiogenesis in MMEC(GK) by promoting invasion and proliferation. FZD5 was inversely upregulated in miR-216b-downregulated MMEC(GK). Subsequently, FZD5 downregulation suppressed angiogenic development, by inhibiting invasion and proliferation in miR-216b-downregulated MMEC(GK). Conclusion: MicroRNA-216b was overexposed in diabetic MMECs and its downregulation may actively enhance angiogenesis in diabetic angiopathy through inverse regulation on FZD5.