Interestingly, while there is strong evidence of increased BMP antagonist Gremlin in a human PAH lung [47], we detected no differences in either endogenous or secreted Gremlin 1 between human PAH and non-diseased PAVSMC, suggesting that Gremlin 1 is produced predominantly by endothelial cells [36]. This evidence concerns the gene GREM1 and pulmonary arterial hypertension.