Induction of HO-1 has been demonstrated to improve MSC therapy in vivo by improving tissue functioning of the damaged organ, whereas inhibition of HO-activity worsened MSC therapy outcome in diverse pathologic conditions, such as ischemia reperfusion injury of the heart, pulmonary arterial hypertension, diabetes, and dermal wound healing [31,33,34,35,36,37,38,39,40]. Here, HMOX1 is linked to pulmonary arterial hypertension.