EC-specific CNP or GC-B conditional knockout (CNP ecKO or GC-B ecKO) mice, but not smooth muscle cell-specific GC-B conditional knockout (GC-B smcKO) mice, show more severe PH and greater expression of Edn1, Il6, Ccl2 and Tgfb1 mRNAs than their genetic controls in PAH models. This evidence concerns the gene CCL2 and pulmonary arterial hypertension.