Abstract P258: Effect of MicroRNA-223 on Hypoxic Pulmonary Hypertension

Chronic hypoxia plays a key role in pulmonary hypertension and remodeling by inducing marked changes in gene expression. However, the regulatory effect of chronic hypoxia on microRNA (miR) expression in the lung has not yet been investigated. The purpose of this study was to determine which miRs are regulated by chronic hypoxia in the mouse lung and to determine their functional significance. We identified miRs altered in mouse lung after 3 weeks chronic hypoxia (10% O 2 (10 in 100) ) treatment by Microarray screening, verified miR target genes by reporter gene assays and Western blotting. Furthermore, we analyzed in vitro and in vivo functional significance for mouse pulmonary vascular artery smooth muscle cells. Among the miRs regulated, miR-223 was the most significantly decreased, a phenomenon verified by RT-qPCR. The insulin-like growth factor 1 receptor (IGF1R) is a known target of miR-223 and the binding of miR-223 to the 3’UTR of IGF1R was demonstrated. We found that IGF1R protein levels (but not RNA) were increased in lungs from hypoxic mice via a mechanism involving HIF1α/2α and reduced C/EBPα expression and transcription activity. Moreover, the expression of IGF1R was decreased following introduction of pre-mir-223 into pulmonary artery smooth muscle cells, an phenomenon coupled to attenuated IGF1-induced Akt phosphorylation, cell migration and proliferation. Decreasing endogenous miR-223 levels using a specific antagomir (3 weeks), increased pulmonary artery pressure and vessel muscularization. A similar phenomenon was observed in miR-223 -/y mice, which also demonstrated a more severe response to hypoxia than wild-type mice. In lungs from primary pulmonary hypertension (PPH) patients we also detected a decrease in miR-223 and increase in IGF1R expression. These data indicate that the downregulation of miR-223 may contribute to the IGF1-induced pulmonary smooth muscle migration by regulating the expression of its receptor and thus contributing to pulmonary remodeling and the development of pulmonary hypertension.