Effect of low-voltage electrical stimulation on angiogenic growth factors in ischaemic rat skeletal muscle

1. Low-voltage electrical stimulation (LVES) in skeletal muscle at a level far below the threshold of muscle contraction has been reported to promote local angiogenesis. However, the mechanism underlying the promotion of local angiogenesis by LVES has not been fully elucidated. In the present study, we evaluated whether angiogenic factors, such as vascular endotherial growth factor (VEGF), hepatocyte growth factor (HGF) and fibroblast growth factor (FGF), as well as other disadvantageous factors, such as inflammation (interleukin (IL)-6) and hypoxia (hypoxia-inducible factor (HIF)-1alpha), contribute to the local angiogenesis produced by LVES. 2. We completely excised bilateral femoral arteries of male Sprague-Dawley rats. After the operation, electrodes were implanted onto the centre of the fascia of the bilateral tibialis anterior (TA) muscles, tunnelled subcutaneously and exteriorized at the level of the scapulae. The right TA muscles of rats were stimulated continuously at a stimulus frequency of 50 Hz, with a 0.1 V stimulus strength and no interval, for 5 days. The left TA muscles served as controls. 3. We found that both VEGF and HGF protein were significantly increased by LVES in stimulated muscles compared with control. The VEGF level of the LVES group was 89.10 +/- 17.19 ng/g, whereas that of the control group was 65.07 +/- 12.88 ng/g, as determined by ELISA (P < 0.05). The HGF level of the LVES and control groups was 8.52 +/- 1.96 and 5.80 +/- 2.14 ng/g, respectively (P < 0.05). In contrast, there was no difference in FGF, IL-6 and HIF-1alpha between the LVES and control groups. 4. These results suggest that LVES in a hindlimb ischaemia model of rats increases not only VEGF, but also HGF, production, which may be the main mechanism responsible for the angiogenesis produced by LVES.