Renin Gene Transfer Restores Angiogenesis and VEGF Expression in Dahl S Rats
To evaluate the importance of the renin angiotensin system (RAS) in VEGF expression and angiogenesis in skeletal muscle, we compared the angiogenic response to electrical stimulation in congenic strains of SS/Jr/Hsd rats using a complementation test design. We have previously demonstrated that both increases in VEGF expression and angiogenesis induced by electrical stimulation of skeletal muscle were absent in inbred Dahl S rats having a wildtype renin allele (S/renss). In contrast, the congenic S/renrr in which a 10 cM segment of chromosome 13 containing the normally functioning salt resistant renin allele was transferred onto the Dahl S background, exhibit the expected changes in renin. In the present study we investigate the effects of electrical stimulation on VEGF expression and angiogenesis in these rats. Congenic S/renrr and S/renss rats, fed a 0.4% salt diet were surgically prepared by chronic implantation of an electrical stimulator. Another group of S/renrr rats was treated with lisinopril, 2 days before the surgery and throughout the stimulation protocol. Rats without any drug treatment were used as control. The right tibialis anterior (TA) and extensor digitorum longus (EDL) were stimulated (10 Hz, 0.3 ms duration) for 8 hours per day for 7 days. The contralateral muscles served as controls. Western blot analysis was performed to identify VEGF protein expression in these muscles. Seven days of electrical stimulation of the skeletal muscles produced no change in vessel density of S/renss (Δ=5.50 ± 3.8 % and 8.14 ± 2.0 % for EDL and TA respectively). Transfer of the resistant renin allele (S/renrr) restored the angiogenic response (Δ=16% and 30% for EDL and TA, respectively) despite a significantly higher blood pressure (113.5 ± 2.25 mmHg and 148.67 ± 1.12 mmHg for S/renss and S/renrr, respectively). Blockade of the RAS in S/renrr restored the phenotype observed in the S/renss (Δ=1.46% and 1.9% to EDL and TA, respectively, p<0.05). In addition, increases in VEGF expression to electrical stimulation were observed only in S/renrr. These results demonstrate that RAS plays an important role in the regulation of VEGF expression and angiogenesis in skeletal muscle.