Isometric Contraction Of Skeletal Muscle And Other Role And Mechanism Of Ischemic Training Site Of Distant Ischemia Angiogenesis

Background: This study aimed to investigate the remote effect of physiological ischemia training induced by isometric exercise on angiogenesis in pathologic model of chronic myocardial ischemia and skeletal muscle ischemia.Methods: The whole experiment included three parts: Part one was the normal muscle experiment; part two was the skeletal muscle ischemia experiment and the part three was the myocardial ischemia experiment. The Part one was designed for confirmation of upregulation of VEGF by isometric exercise induced physiological ischemia per se. Subjects were devided into 3 groups: normal control (NC); isometric exercise (IE) induced by high intensity electrical stimulation (ES) with 2.5mA, 40Hz, 1ms and dynamic exercise (DE) induced by high intensity ES with 2.5mA, 1Hz and 1ms. Based on part one findings, high intensity IE was selected as the physiological ischemia model. The training period was one week, vascular endothelial growth factor (VEGF) protein detection were analyzed by western blot.Part two was designed for testing the effect of IE induced ischemia on the collateral formation on the contralateral skeletal muscle with pathological ischemia which was made of femoral artery occlusion (FAO). The subjects were divided into 4 groups: no intervention control (FAO-N); FAO on left limb and high intensity IE (FAO-HE) induced by ES with 2.5mA, 40Hz, 1ms on right limb; FAO on left limb and low intensity IE(FAO-LE) induced by ES with 0.3mA, 40Hz, 1ms on right limb; FAO atboth hind limbs and high intensity IE (BFAO-HE) on right limb.The part three experiment was designed for examing the effect of skeletalmuscle ischemia on myocardial collateral formation. The myocardialischemia (MI) model was produced by a balloon constrictor implanted inleft ventricular branch.The subjects were divided into groups of the shamoperation (MI-S), pure MI control (MI-N) and high intensity IE training(MI-HE).The training period for part 2 and part 3 was 4 weeks. Regional bloodflow was measured by microspheres technique. Collateralization wasevaluated by immunohistochemistry. VEGF mRNA and protein detectionwere analyzed by western blot and RT-PCR.Results: In part one, the expression of VEGF in IE was high than DE andNC (P＜0.01), There was no statistically significant difference betweenDE and NC.In part two, collateral blood flow (P＜0.01), capillary density (P<0.001),expression of VEGF mRNA (P＜0.001) and protein (P<0.01) remarkableincreased in FAO-HE, there was no statistically significant differenceamong other groups.In part three, collateral blood flow and capillary density were highest inMI-HE, these parameters in MI-N were also significantly higher than that in the MI-S. The level of VEGF mRNA and protein in MI-HE werehigher than that in the MI-N (P＜0.01, P<0.05), these parameters alsoincreased in MI-N (P＜0.01vs. MI-S). At the endpoint of experiment,significant relationship was found between myocardium VEGF proteinand serum VEGF protein in each group.Conclusion: This study provides the first in vivo experimental evidenceof the angiogenesis in heart and skeletal muscle facilitated byphysiological ischemia training induced by isometric exercise for 4 weeks.The mechanism is related to upregulation of VEGF.