PECAM1 and pulmonary arterial hypertension: Interestingly, in the perivascular areas, H3K27Me3 abundance increased 1.6-fold in ECs of PAH rats compared to sham-treated rats (Figures 7C,D) which associated with an increased percentage of CD31+ SM22α+ cells (14.31% PAH and 3.94% sham, p = 0.0002, Figures 7C–E), indicative of EndMT.