Introduction:
Pulmonary hypertension (PH) is characterized by persistent elevation of pulmonary arterial pressure which leads to right ventricular overload and ultimately right heart failure. Few treatment options offer effective management of PH and therapy focuses on alleviating symptoms. Therefore, the development of a novel strategy for the treatment of this disease is highly relevant.  

Purpose Previous studies point out the importance of pro-inflammatory macrophages in induction of PH. Moreover, patients with increased plasma levels of inflammatory markers present with more severe disease. Regnase-1 is an endoribonuclease cleaving the mRNA of pro-inflammatory cytokines therefore reducing their levels of expression. Hence, we hypothesize that regnase-1 overexpression in lung tissue can be translated into a novel therapeutic approach for PH.

Methods:
Mice were subjected to hypoxic conditions (10% O2) for 3 weeks. Regnase-1 overexpression was achieved in lung endothelial cells by transduction with targeted adeno-associated virus serotype 2 (AAV2-ESGHGYF). AAV2-EGFP treated mice served as controls. Right ventricular function was monitored by echocardiography and right ventricular systolic pressure was measured by right heart catheterization. The degree of pro-inflammatory cell infiltration was monitored by immunohistochemistry. Induction of fetal gene programme in the right ventricle was measured by real time qPCR. Fibrosis deposition in lung tissue was determined by Sirius Red staining of frozen sections. Results Regnase-1 overexpression in lung endothelial cells led to a significant improvement in right ventricular function and decreased pulmonary pressure in mice placed under hypoxic conditions. Moreover, the described gene therapy approach induced normalization of fetal gene programme in the cardiac tissue and reduced pro-inflammatory cell infiltration in lungs. Additionally, we could determine mitigation of pulmonary extracellular matrix deposition and fibrosis development in mice receiving AAV2-regnase1 as compared to controls.

Conclusion:
 AAV-mediated regnase-1 overexpression in lung endothelial cells results in amelioration of pathological events leading to PH in mice subjected to hypoxia. Further experiments will determine whether this method can be successful used for reversing already established PH.