We report that anti-Activin A and anti-TGF-β, but not anti-Gremlin 1, antibodies significantly reduce self-supported growth and proliferation of PAVSMC from human PAH lungs while having little effect on the growth of non-diseased PAVSMC induced by soluble factors secreted by PAH PAVSMC. This evidence concerns the gene GREM1 and pulmonary arterial hypertension.