FOS and pulmonary arterial hypertension: Cardiomyocytes with nuclei positively stained for c-fos compared to the total amount of cells in the RV revealed an increase from 5.8 ± 0.9 to 17.8 ± 1.8% due to PAH which was partially reversed by lodenafil (13.6 ± 0.5%) and normalized by lodenafil + hMSCs (6.1 ± 0.5%).