Treadmill exercise training produced initial 3- to 6-fold increases in VEGF, VEGF receptors, Tie-2, and eNOS mRNA, which dissipated before the increase in capillarity.
Exercise training induces an early, transient upregulation of angiogenic growth factors in skeletal muscle that precedes histological increases in capillarity.
Angiogenesis occurs in skeletal muscle in response to exercise training. To gain insight into the regulation of this process, we evaluated the mRNA expression of factors implicated in angiogenesis over the course of a training program. We studied sedentary control (n = 17) rats and both sedentary (n = 18) and exercise-trained (n = 48) rats with bilateral femoral artery ligation. Training consisted of treadmill exercise (4 times/day, 1-24 days). Basal mRNA expression in sedentary control muscle was inversely related to muscle vascularity. Angiogenesis was histologically evident in trained white gastrocnemius muscle by day 12. Training produced initial three- to sixfold increases in VEGF, VEGF receptors (KDR and Flt), the angiopoietin receptor (Tie-2), and endothelial nitric oxide synthase mRNA, which dissipated before the increase in capillarity, and a substantial (30- to 50-fold) but transient upregulation of monocyte chemoattractant protein 1 mRNA. These results emphasize the importance of early events in regulating angiogenesis. However, we observed a sustained elevation of the angiopoietin 2-to-angiopoietin 1 ratio, suggesting continued vascular destabilization. The response to exercise was (in general) tempered in high-oxidative muscles. These findings place importance on cellular events coupled to the onset of angiogenesis.
Lloyd et al. (2003) studied Skeletal muscle angiogenesis (n=83). Treadmill exercise training vs. Sedentary rats was evaluated on mRNA expression of factors implicated in angiogenesis. Treadmill exercise training produced initial 3- to 6-fold increases in VEGF, VEGF receptors, Tie-2, and eNOS mRNA, which dissipated before the increase in capillarity.