To elucidate how miRNAs are involved in PAH pathogenesis, we investigated and compared global miRNA expression profiles in PASMCs isolated from monocrotaline-treated rats and normal control using microarray and selected the most significantly down-regulated miRNAs, miR-26b, for further functional analysis due to its documented role in regulating human cell proliferation [27], as well as the virtual function to suppress the expression of CTGF and CCND1 predicted by online microRNA databases such as www.targetscan.org. Here, CCND1 is linked to pulmonary arterial hypertension.