Background aims. We hypothesized that the long-term therapeutic effect of combined sildenafil and bone marrow-derived endothelial progenitor cells (BMDEPCs) on monocrotaline (MCT)-induced rat pulmonary arterial hypertension (PAH) is superior to either treatment alone. Methods. Male Sprague-Dawley rats (n ¼ 40) were equally divided into normal controls, MCT (65 mg/kg, subcutaneously) only, MCT þ sildenafil (25 mg/kg/day, orally), MCT þ BMDEPCs (2.0 106 autologous cells, intravenously) and MCT þ sildenafilþ BMDEPCs. BMDEPCs and sildenafil were given on day 21 after MCT administration. Animals were sacrificed by day 90 after MCT administration. Results. The apoptotic (caspase 3, Bax) and inflammatory (tumor necrosis factor-a, matrix metalloproteinase-9) biomarkers in right ventricle and lung and pulmonary expressions of fibrotic biomarkers (transforming growth factor-b, p-Smad3) and connexin 43 protein were lower in monotherapy groups (i.e., MCT þ sildenafil andMCT þ BMDEPCs) and further decreased in normal controls and combined treatment groups (i.e.,MCT þ sildenafil þ BMDEPCs) compared with untreated animals (i.e., MCT only) (all P < 0.01). Expressions of anti-fibrotic biomarkers (bone morphogenetic protein-2, p-Smad1/5) and numbers of alveolar sacs and arterioles in lung were higher in monotherapy groups and further increased in normal controls and combined treatment groups compared with untreated animals (all P < 0.005). In right ventricle, connexin 43 and a-myosin heavy chain (MHC) expressions were higher in the monotherapy groups and further elevated in normal controls and combined treatment groups compared with untreated animals, whereas b-MHC exhibited the opposite pattern (all P < 0.01). Right ventricular systolic pressure and weight were lower in the monotherapy animals and further reduced in normal controls and combined treatment groups compared with untreated animals (all P < 0.0001). Conclusions. Combined therapy with BMDEPCs and sildenafil was superior to either treatment alone in attenuating rodent MCT-induced PAH.
