 Bone marrow mesenchymal stem cell (BM-MSC) has been shown to treat pulmonary arterial hypertension (PAH). However, excessive reactive oxygen species (ROS) increases the apoptosis of BM-MSCs, leading to poor survival and engraft efficiency. Thus, improving the ability of BM-MSCs to scavenge ROS may considerably enhance the effectiveness of transplantation therapy. Mammalian Ste20-like kinase 1 (Mst1) is a pro-apoptotic molecule which increases ROS production. The aim of this study is to uncover the underlying mechanisms the effect of Mst1 inhibition on the tolerance of BM-MSCs under H2O2 condition.