Endothelial Nitric Oxide Synthase Overexpression Provides a Functionally Relevant Angiogenic Switch in Hibernating Pig Myocardium
Christian Kupatt, MD*,*,
Rabea Hinkel, DVM*,
Marie-Luise von Brühl, DVM*,
Tilmann Pohl, MD*,
Jan Horstkotte, MD*,
Philip Raake, MD*,
Chiraz El Aouni, PhD*,
Eckehard Thein, DVM ,
Stefanie Dimmeler, PhD ,
Olivier Feron, PhD and
Peter Boekstegers, MD*
* Internal Medicine I, Klinikum Grosshadern
Institute of Surgical Research, Ludwig-Maximilians-University of Munich, Munich, Germany
Molecular Cardiology, Department of Medicine IV, University of Frankfurt, Frankfurt, Germany
Unit of Experimental Pharmacology, Catholique University of Leuven, Brussels, Belgium
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Figure 1 Percutaneous Model of Hibernating Myocardium
After percutaneous implantation of a reduction stent in the proximal left anterior descending artery (LAD) (day 0, arrow) the formation of a high-grade stenosis was angiographically confirmed at day 10 (top). At day 28, (sub)total occlusion of the LAD was noted with distal filling of the LAD through collaterals. At this time point, retroinfusion of liposomes with either green fluorescent protein (GFP) or endothelial nitric oxide synthase (eNOS) S1177D was performed. At day 49, hemodynamic measurements were performed, and tissue was obtained for molecular analysis.
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Figure 2 eNOS Expression After Retroinfusion of eNOS S1177D
Compared with a control heart (A), endothelial nitric oxide synthase (eNOS) S1177D transfection enhanced eNOS expression in the ischemic area (B). (C) In comparison, inducible NOS (iNOS) was found to be more confined to round cells (arrows), which did not express eNOS (D = merged fluorescence). Red bar = 50 µm. (E) Immunoblotting of eNOS revealed a 2.3-fold increase of eNOS expression in the ischemic region, as compared with the control region (representative example of 3 experiments). (F) Cyclic guanosine monophosphate (cGMP) levels detected by radioimmunoassay (RIA) indicate an increased cGMP formation in eNOS S1177D-treated animals, except for L-nitroarginine-methylester (L-NAME) co-application (normalized to nonischemic tissue, 3 animals/group with 3 tissue specimens/condition each). LAD = left anterior descending artery; RCx = ramus circumflexus.
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Figure 3 Endothelial Cells Proliferate After eNOS S1177D Transfection In Vitro
Proliferation of hypoxic coronary endothelial cells (CECs) is increased after endothelial nitric oxide synthase (eNOS) S1177D transfection (n = 4 independent experiments). H/R = hypoxia-reoxygenation; L-NAME = L-nitroarginine-methylester.
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Figure 4 Endothelial Cells Proliferate After eNOS S1177D Transfection In Vivo
Histochemical evaluation proliferation (Ki67 positivity) in control (A) and ischemic (B) tissue. Red bar = 50 µm. (C) Quantitative analysis revealed an increased proliferation in eNOS S1177D transfected tissue (3 experiments/group with 5 tissue specimens/condition each). Cx = circumflex coronary artery. (D) Fluorescence microscopy of Ki67 (left), endothelial marker platelet endothelial adhesion molecule-1 (PECAM-1) (middle), and overlay (right), red bar = 10 µm. Abbreviations as in Figure 2.
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Figure 5 Capillary and Collateral Growth After eNOS S1177D Transfection In Vivo
(A) Example of platelet endothelial adhesion molecule-1 staining of capillaries (red bar = 100 µm). (B) Three days after transfection, the ischemic area of endothelial nitric oxide synthase (eNOS) S1177D-transfected animals displayed increased capillary levels compared with the eNOS+ L-nitroarginine-methylester (L-NAME) group. (C) The pro-angiogenic effect was found attenuated at day 49. (D) However, the number of collaterals at day 49 (postmortem angiogram) was increased after eNOS S1177D transfection (n = 6/group).
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Figure 6 Forced eNOS S1177D Expression Improves Perfusion of Ischemic Myocardium
At day 28 (A) and day 49 (B), regional myocardial perfusion in the RCx region at rest was similar in all groups at resting heart rate (slice 1 = most proximal ischemic short-axis tissue slice, slice 4 = apex). (C) The LAD perfusion at day 28 was reduced to the same extent in all groups. (D) Myocardial perfusion of the apical ischemic area was significantly improved in the eNOS S1177D-treated hearts, as compared with control or L-NAME co-treated animals. (E) At resting heart rate and (F) at rapid atrial pacing, the LAD perfusion/RCx perfusion ratio was significantly improved in the eNOS S1177D hearts, when compared with control hearts (n = 6 for control subjects, eNOS S1177D, n = 5 for eNOS S1177D + L-NAME). Cx = circumflex coronary artery; other abbreviations as in Figure 2.
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Figure 7 Regional Gain of Myocardial Function in the Distal LAD Region
Regional myocardial function was assessed by subendocardial segment shortening (see Methods) at day 49 in the proximal (A) or distal LAD region (B) at rest or after atrial pacing (120/min and 140/min); n = 5/group. Abbreviations as in Figure 2.
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