Role of mitochondrial PKD on right ventricular fibrosis under pulmonary hypertension

Introduction: Growing evidence suggests a link between right ventricular (RV) fibrosis, poor function of the pressure-overloaded RV, and mortality in pulmonary arterial hypertension (PAH). However, there are no currently available therapies that specifically target RV fibrosis. Using RV tissues from a preclinical rat PAH model, we previously reported that activation of stress-responsive protein kinase D (PKD) and phosphorylation of its substrate dynamin-related protein 1 (DRP1) occur specifically at the outer mitochondrial membrane (OMM) of RV cardiac fibroblasts (RV-CFs), but not in RV myocytes. RV-CFs isolated from PAH rats exhibited increased mitochondrial fission, mitochondrial reactive oxygen species (mROS), and proliferative signaling compared to RV-CFs from control animals, suggesting an association between PKD signaling in RV-CFs and RV fibrosis. Hypothesis: Inhibition of mitochondrial PKD signaling in CFs can attenuate RV fibrosis in PAH. Methods: Primary adult CFs from human ventricles were used for in vitro assays. A preclinical rat PAH model (Sugen 5416 injection and 3-week hypoxia followed by 4-week normoxia) was used for in vivo assays. Results: To specifically inhibit PKD activity at the OMM, an OMM-targeted dominant-negative PKD1 (mt-PKD-DN) was generated by adding an OMM-target sequence (amino acid 1-33 from human TOM20) at the N-terminus of PKD1-K612W. We confirmed that mt-PKD-DN is specifically expressed in mitochondria and decreases basal PKD activity only in mitochondria, assessed by protein fractionation. Importantly, mt-PKD-DN was able to inhibit mitochondrial fission, reduce mROS, hyperpolarize mitochondrial membrane potential, and ultimately decrease CF proliferation in vitro. To inhibit mitochondrial PKD activity in quiescent and resident CFs in vivo, we next administrated CF-selective adeno-associated virus serotype 9 (AAV9) carrying human TCF21 (hTCF21) promoter and mt-PKD-DN into the rat PAH model by tail vein injection. Introduction of AAV9-hTCF21-mt-PKD-DN or its control virus did not significantly alter baseline cardiac function. CF-specific mt-PKD-DN expression was able to significantly reduce RV hypertrophy/fibrosis, and RV-CF hyperproliferation as assessed by immunostaining of a nucleus-localized marker of active cell proliferation Ki67. Lastly, we found the partial recovery of in vivo RV function (i.e., recovery of tricuspid annular plane systolic excursion in echocardiography) in PAH rats with mt-PKD-DN. Conclusion: Targeting mitochondrial PKD may be a potential therapeutic strategy to reduce cardiac fibrosis under pathological conditions including PAH. R01HL136757 (to J.O.-U), AHA 18CDA34110091 (to B.S.J) This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.