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(Arteriosclerosis, Thrombosis, and Vascular Biology. 2008;28:2144.)
© 2008 American Heart Association, Inc.

Integrative Physiology/Experimental Medicine

Myocyte Specific Overexpression of Myoglobin Impairs Angiogenesis After Hind-Limb Ischemia

Surovi Hazarika; Michael Angelo; Yongjun Li; Amy J. Aldrich; Shelley I. Odronic; Zhen Yan; Jonathan S. Stamler; Brian H. Annex

From the Division of Cardiology, Department of Medicine (S.H., Y.L., A.J.A., S.I.O., Z.Y.) and the Departments of Medicine and Biochemistry (M.A., J.S.S.), Duke University Medical Center, Durham, NC; and the Division of Cardiovascular Medicine, Department of Medicine, and Robert M. Berne Cardiovascular Research Center (B.H.A.), University of Virginia, Charlottesville.

Correspondence to Brian H. Annex, MD, Division of Cardiovascular Medicine and the Cardiovascular Research Center, UVAHS PO Box 800158, Charlottesville, VA 22908. E-mail annex{at}virginia.edu

Objective— In preclinical models of peripheral arterial disease the angiogenic response is typically robust, though it can be impaired in conditions such as hypercholesterolemia and diabetes where the endothelium is dysfunctional. Myoglobin (Mb) is expressed exclusively in striated muscle cells. We hypothesized that myocyte specific overexpression of myoglobin attenuates ischemia-induced angiogenesis even in the presence of normal endothelium.

Methods and Results— Mb overexpressing transgenic (MbTg, n=59) and wild-type (WT, n=56) C57Bl/6 mice underwent unilateral femoral artery ligation/excision. Perfusion recovery was monitored using Laser Doppler. Ischemia-induced changes in muscle were assessed by protein and immunohistochemistry assays. Nitrite/nitrate and protein-bound NO, and vasoreactivity was measured. Vasoreactivity was similar between MbTg and WT. In ischemic muscle, at d14 postligation, MbTg increased VEGF-A, and activated eNOS the same as WT mice but nitrate/nitrite were reduced whereas protein-bound NO was higher. MbTg had attenuated perfusion recovery at d21 (0.37±0.03 versus 0.47±0.02, P<0.05), d28 (0.40±0.03 versus 0.50±0.04, P<0.05), greater limb necrosis (65.2% versus 15%, P<0.001), a lower capillary density, and greater apoptosis versus WT.

Conclusion— Increased Mb expression in myocytes attenuates angiogenesis after hind-limb ischemia by binding NO and reducing its bioavailability. Myoglobin can modulate the angiogenic response to ischemia even in the setting of normal endothelium.

We hypothesized that myocyte specific overexpression of myoglobin (Mb) would attenuate ischemia-induced angiogenesis, despite normal endothelium. Mb overexpressing transgenic and wild-type mice underwent unilateral femoral artery ligation/excision. Increased Mb expression attenuates angiogenesis after hind-limb ischemia by binding NO and reducing its bioavailability, even in the setting of normal endothelium.

Key Words: angiogenesis • animal models of human disease • genetically altered mice • endothelium/vascular type/nitric oxide