Gene Therapy for Hypertension: Recombinant Adeno-Associated Virus Vector Delivery of Angiotensin Type 1 Receptor Antisense in Hypertensive Double Transgenic Mice
Introduction: The goal of gene therapy for hypertension is to produce prolonged reductions of high blood pressure with a single administration of a transgene. We have developed gene therapy using adeno-associated virus (AAV)antisense (AS) as a vector because it is safe, stable and effective. However, because large quantities of AAV are not yet available, our previous studies were in baby rats or by brain injections to achieve an effective concentration of AAV. Since mice are one-tenth the size of rats, systemic injection of AAV-AS achieves higher concentrations than in rats. To test systemic injection in an adult hypertensive model, this study uses double transgenic (dt) mice, with human renin (hR) and human AGT (hAGT) transgenes. In these mice, plasma Ang II levels are elevated and blood pressure increased (∼156 mmHg), compared to controls (∼ 100 mmHg). Methods: dt mice with established baseline BP of >156 mmHg (n=5) were injected (100 μl) with a single dose of 4x1010 infectious particles of rAAV-AT1R-AS. Blood pressure recordings by the tailcuff method were made once per week for 6 months. Results: One week after intracardiac injection of rAAV-AT1R-AS, blood pressure decreased by 35-50 mmHg (p<0.01,compared to baseline). The normalized blood pressure persisted for the full length of the study, 28 weeks. Individual mice were sacrificed at 14-28 weeks and tissues taken for detection of rAAV-AT1R- AS, At both time periods, the neor transgene was present in lung, kidney, liver, heart, adrenal gland and fat. The rAAV was not detected in the brain. Renal arterioles (n=3) showed a reduced (50%)contractile response to doses of Ang II, compared to controls (n=3). Conclusion: The results demonstrated that a single systemic delivery of rAAV-AT1R-AS in adult, hypertensive mice produces a profound decrease in blood pressure for at least 6 months. The prolonged effect is due to the continuous expression of the AT1-R antisense transgene inhibiting AT1 receptors.