SPP1 and pulmonary arterial hypertension: PH patients with different etiologies, including IPAH [40,41], PAH associated with congenital heart diseases (CHD-PAH) [42], PAH associated with connective tissue diseases (CTD-PAH) [43] and PH associated with COPD [44], display increased osteopontin expression in the pulmonary vasculature and lung tissue.