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Cardiomyocyte-Specific Inhibition of Prolyl-4-Hydroxylase 2 (PHD-2) Leads to Increased Pro-angiogenic and Anti-apoptotic Signaling and Preservation of Cardiac Function in a Murine Genetic Myocardial Infarction Model
Sue Ting Lim2, Pradeep S. Radhakrishna2, Mahesh Thirunavukkarasu2, John Alexander Palesty1, Nilanjana Maulik2
1The Stanley J. Dudrick, Department of Surgery, Saint Mary"s Hospital, Waterbury, Connecticut, United States, 2Department of Surgery, University of Connecticut School of Medicine, Farmington, Connecticut, United States

Objective: We have previously reported the stabilization of hypoxic-inducible transcription factor (HIF-1alpha) by suppressing prolyl-4-hydroxylase enzymes (PHD-1 and PHD-3) improved angiogenesis, cardiac function, and limb perfusion in murine models. This study explores the inhibitory effects of another prolyl-4-hydroxylase enzyme, PHD-2, in ischemic heart failure. We used a mouse cardiac-specific PHD-2 gene knockout model to study its effects on angiogenic factors, cell survivability, and cardiac function in myocardial infarction(MI).

Design: Preclinical murine model permanent ligation of left anterior descending artery (LAD) to induce MI.

Setting: Basic Science Surgical Laboratory (UConn Health).

Patients or other participants: Cardiomyocyte-specific prolyl-4-hydroxylase 2 knockout (PHD2-/-) and Wild Type (WT) mice, 8-12 weeks old.

Interventions: LAD is ligated in wild-type (WTMI) and PHD2-/- mice (PHD2-/-MI) to induce MI. Cardiac function was obtained using echocardiography. Left ventricular tissues were obtained at 4 and 30-days post-MI.

Main Outcome Measures: Echocardiographic analysis was performed 30-days post-MI followed by immunohistochemistry to determine the extent of fibrosis and vessel growth. Western blot (WB) was performed to determine pro-angiogenic and anti-apoptotic factors.

Results: Echocardiography at 30-days post-MI shows a greater ejection fraction (52.023.2% vs. 27.853.12%, p<0.0001) and fractional shortening (26.88 1.9% vs. 13.141.63%, p<0.0001) in PHD2KO as compared to WT(n=9). WB shows increased HIF-1alpha (36-fold), VEGF (11-fold), phospho-AKT (4.3-fold), beta-Catenin (19-fold) levels along with reduced Bax expression (3.6-fold) and myocardial fibrosis (3.81.4% vs. 15.55%, p=0.048) in PHD2-/-MI compared to WTMI group (n=6).

Conclusion: Inhibition of PHD2 is cardioprotective as evident by preserved cardiac function, increased expression of angiogenic factors, and reduction of apoptotic markers. Overall, PHD2 gene inhibition is a promising candidate in the management of cardiovascular diseases.

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