MicroRNA-30a-5p promotes proliferation and inhibits the apoptosis of human pulmonary artery endothelial cells by downregulating Chi3l1 levels through binding to the 3′-UTR of Chi3l1; thus, the miR-30a-5p/Chi3l1 axis may be a potential target in the treatment of pulmonary arterial hypertension (PAH) [300]. This evidence concerns the gene CHI3L1 and pulmonary arterial hypertension.