Objective-MicroRNAs (miRNAs) are small noncoding RNAs that have the capacity to control protein production through binding "seed" sequences within a target mRNA. Each miRNA is capable of potentially controlling hundreds of genes. The regulation of miRNAs in the lung during the development of pulmonary arterial hypertension (PAH) is unknown. Methods and Results-We screened lung miRNA profiles in a longitudinal and crossover design during the development of PAH caused by chronic hypoxia or monocrotaline in rats. We identified reduced expression of Dicer, involved in miRNA processing, during the onset of PAH after hypoxia. MiR-22, miR-30, and let-7f were downregulated, whereas miR-322 and miR-451 were upregulated significantly during the development of PAH in both models. Differences were observed between monocrotaline and chronic hypoxia. For example, miR-21 and let-7a were significantly reduced only in monocrotaline-treated rats. MiRNAs that were significantly regulated were validated by quantitative polymerase chain reaction. By using in vitro studies, we demonstrated that hypoxia and growth factors implicated in PAH induced similar changes in miRNA expression. Furthermore, we confirmed miR-21 downregulation in human lung tissue and serum from patients with idiopathic PAH. Conclusion-Defined miRNAs are regulated during the development of PAH in rats. Therefore, miRNAs may contribute to the pathogenesis of PAH and represent a novel opportunity for therapeutic intervention. Key Words: pulmonary hypertension Ⅲ small RNA molecules Ⅲ gene regulation P ulmonary arterial hypertension (PAH) is a complex disorder characterized by the obstructive remodeling of pulmonary arteries, leading to a progressive elevation in pulmonary arterial pressure (PAP) and subsequent right-sided heart failure and death. 1 Familial PAH is associated in 80% of cases with diverse heterozygous mutations in the gene-encoding bone morphogenetic protein receptor 2 (BMPR-II) 2 and can be associated with mutations in the activin-receptor kinaselike 1 gene. 3 The cause of the variable phenotypic expression of PAH among carriers of mutated BMPR-II genes is unclear, and is likely related to environmental and genetic modifiers. Although BMPR-II-related pathways are considered pivotal, many other mediator pathways participate in the pathogenesis of PAH and are being actively investigated, both independently and in combination. For example, the involvement of serotonin in the development of experimental PAH has been recently reported. 4,5 Indeed, important interactions between the serotonin and BMP pathways have recently been described. 6 Rats exposed to hypoxia or injected with the toxin monocrotaline develop pulmonary arterial changes correlated with the development of PAH, including remodeling and elevating PAP.MicroRNAs (miRNAs) are small noncoding transcripts of 16 to 29 nucleotide RNAs that regulate gene expression posttranscriptionally by targeting mRNAs. Animal miRNAs are processed from longer primary transcripts (primary miRNAs) that can contain ...

Background-Pulmonary arterial hypertension (PAH) is a hyperproliferative vascular disorder observed predominantly in women. Estrogen is a potent mitogen in human pulmonary artery smooth muscle cells and contributes to PAH in vivo; however, the mechanisms attributed to this causation remain obscure. Curiously, heightened expression of the estrogenmetabolizing enzyme cytochrome P450 1B1 (CYP1B1) is reported in idiopathic PAH and murine models of PAH. Methods and Results-Here, we investigated the putative pathogenic role of CYP1B1 in PAH. Quantitative reverse transcriptionpolymerase chain reaction, immunoblotting, and in situ analysis revealed that pulmonary CYP1B1 is increased in hypoxic PAH, hypoxicϩSU5416 PAH, and human PAH and is highly expressed within the pulmonary vascular wall. PAH was assessed in mice via measurement of right ventricular hypertrophy, pulmonary vascular remodeling, and right ventricular systolic pressure. Hypoxic PAH was attenuated in CYP1B1 Ϫ/Ϫ mice, and the potent CYP1B1 inhibitor 2,3Ј,4,5Ј-tetramethoxystilbene (TMS; 3 mg ⅐ kg Ϫ1 ⅐ d

Rationale The pathogenesis of PAH remains unclear. The four microRNAs representing the miR-143 and miR-145 stem loops are genomically clustered. Objective To elucidate the transcriptional regulation of the miR-143/145 cluster, and the role of miR-143 in PAH. Methods and Results We identified the promoter region that regulates miR-143/145 miRNA expression in pulmonary artery smooth muscle cells (PASMCs). We mapped PAH-related signalling pathways, including estrogens receptor (ER), liver X factor/retinoic X receptor (LXR/RXR), TGF-β (Smads), and hypoxia (HRE) that regulated levels of all pri-miR stem loop transcription and resulting miRNA expression. We observed that miR-143-3p is selectively upregulated compared to miR-143-5p during PASMC migration. Modulation of miR-143 in PASMCs significantly altered cell migration and apoptosis. In addition, we found high abundance of miR-143-3p in PASMCs-derived exosomes. Using assays with pulmonary arterial endothelial cells (PAECs) we demonstrated a paracrine pro-migratory and pro-angiogenic effect of miR-143-3p enriched exosomes from PASMC. Quantitative PCR and in situ hybridisation showed elevated expression of miR-143 in calf models of PAH as well as in samples from PAH patients. Moreover, in contrast to our previous findings that had not supported a therapeutic role in vivo, we now demonstrate a protective role for miR-143 in experimental PH in vivo in miR-143−/− and antimiR143-3p-treated mice exposed to chronic hypoxia in both preventative and reversal settings. Conclusions miR-143-3p modulated both cellular and exosome-mediated responses in pulmonary vascular cells, while inhibition of miR-143-3p blocked experimental PH. Taken together these findings confirm an important role for the miR-143/145 cluster in PAH pathobiology.