Abstract 3586: A Critical and Novel Role of MicroRNAs in the Etiology of Human PAH
Pulmonary arterial hypertension (PAH) is a proliferative remodeling disease characterized by enhanced pulmonary artery smooth muscle (PASMC) proliferation and suppressed apoptosis. We previously described that the sustainability of this phenotype requires long-term plasticity through regulation at the gene level by transcription factors like NFAT and HIF-1. The mechanism by which NFAT/HIF-1 are activated in PAH-PASMC remains elusive. Through their interaction with mRNA, microRNAs have emerged as crucial players regulating gene expression in a variety of organisms. Nevertheless, the implication of miRNAs in PAH remains unknown. Using TaqMan microRNA assay, we identified 10 downregulated and 6 upregulated miRNAs in human PAH-PASMC compared to healthy PASMC (n=4; p<0.05). DNA-Microarrays and Gene Sets Enrichment Analysis reveal that both NFAT and HIF-1 pathways are upregulated in PAH-PASMC compared to healthy PASMC (n=4; p<0.05). Cross analysis of our DNA-microarrays/microRNAs assay data with In silico algorithm analysis (targetscan5.1) showed that among the 16 altered miRNAs in PAH-PASMC, 7 (miR-27b; 29; 106b; 101; 204; 367 and 450) and 4 (miR-302; 138; 145 and LET-7a) are predicted as NFAT and HIF-1 pathway activator respectively (p<0.05). Interestingly, miR-204 is the most downregulated miRNA in PAH (7 fold p<0.05; n=4) and is localized within the TRPM3 gene (TRP channel are involved in the etiology of PAH). In vitro, miR-204 dowregulation in PAH-PASMC is associated with an increase in NFAT expression and activity (n=5; p<0.05 luciferase assay); promoting PAH-PASMC proliferation (n=50; p<0.05 PCNA) and resistance to apoptosis (p<0.05 n=50; TMRM&TUNEL). Restoring miR-204 expression (by mimics) in PAH-PASMC reverses these abnormalities, while miR-204 inhibition in healthy PASMC mimics them. Similarly to humans, miR-204 is downregulated in monocrotaline-induced PAH rat model (n=8 p<0.001) and its in vivo activation by mimic (i.v 2weeks) decreases PAH (n=8; p<0.05). We demonstrated for the first time the implication of inappropriate miRNAs expression in human and experimental PAH. While the role of the others identified miRNAs remains to be established in PAH, targeting miRNAs might represent a novel therapeutic strategy for human PAH.