FN1 and pulmonary venoocclusive disease: To further investigate the molecular mechanism by which H2 prevents and rescues EndoMT in the context of PVOD, the protein expression of classic PVOD-related protein GCN2, mesenchymal markers FN1 and Vimentin, endothelial cell makers CD31 and VE-cadherin, and p-Smads in lung tissue were then measured.