COL3A1 and pulmonary arterial hypertension: We also found that the PAH lung had significantly increased gene expression for genes involved in the biosynthesis of collagen, such as procollagen-lysine, 2-oxoglutarate 5-dioxygenase 2 (PLOD2), collagen type XIV alpha 1 (COL14A1) and collagen type III alpha 1 (COL3A1) (Fig 2)