Mitochondrial Transplantation from Bone Marrow Mesenchymal Stromal Cells Combined with Sildenafil Attenuated Vascular Remodeling and Improved Right Ventricular Dysfunction in Experimental Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is characterized by progressive vascular remodeling and right ventricular (RV) dysfunction, processes that are increasingly associated with disturbances in cellular metabolism. We investigated whether transplantation of exogenous mitochondria derived from bone marrow mesenchymal stromal cells, alone or combined with sildenafil, could improve mitochondrial homeostasis and attenuate cardiopulmonary remodeling in monocrotaline-induced PAH. Male Wistar rats were assigned to control (CTRL, <i>n</i> = 8) or PAH (<i>n</i> = 32) groups. Fourteen days after induction of PAH, animals were randomized to receive saline, sildenafil (20 mg/kg/day for 14 days), intravenous mitochondrial transplantation (100 μg, days 14 and 21), or combined therapy. On day 28, echocardiography, invasive measurement of RV systolic pressure (RVSP), pulmonary vascular histology, gene expression analyses (vimentin, VE-cadherin, and mitochondrial metabolism-related genes), and high-resolution respirometry were performed. All treatments significantly reduced RVSP compared with untreated PAH. Mitochondrial therapy, alone or combined with sildenafil, decreased arteriolar α-smooth muscle actin content, whereas endothelial-mesenchymal transition was attenuated only with combined treatment. Mitochondrial transplantation and sildenafil increased Complex I-dependent respiration, whereas Complex IV activity improved exclusively with mitochondrial therapy. Combined treatment reduced plasma IL-6 and IL-1β levels compared with PAH. Thus, mitochondrial transplantation, particularly when combined with sildenafil, improved RV function, limited pulmonary vascular remodeling, reduced plasma inflammatory markers, and changed key mitochondrial pathways in experimental PAH.