AAV9-MRTF-A ameliorates peripheral artery disease in a pig model (GeneVaPAD)

Background

Peripheral artery disease is a disabling and prognostically unfavorable condition, caused by impairment of lower limb perfusion. Though narrowing or complete occlusion of a large artery is nowadays treatable by surgical or interventional means (bypasses or ballon angioplasty and stenting, respectively), smaller arteries are not amenable for these techniques. The objective of the translational project GeneVaPad is to test a complementary treatment by growth and maturation of small vessels which are often rarefied or absent due to prolonged hypoxia and/or microvascular inflammation caused by cardiovascular risk factors (diabetes, hyperlipidemia).

Methods

As therapeutic agent to regrow functional microvessel networks we used the long expressing adeno-associated viral vectors encoding for MRTF-A, which promotes microvessel sprouting and stabilisation. AAV9-MRTF-A is tested in a pig model of femoral artery occlusion in control and diabetic or hyperlipidemic pigs. As a model of porcine hindlimb ischemia, we established implantation of a modified Bentley reduction stent into the superficial femoral artery. As application route, we found intraarterial application more homogeneous than intramuscular application and more efficacious than retrograde intravenous application.

Results

A dose of 5x1014vgs per animal was efficiently increasing microvessel densities (from 287+/-13 to 391+/- 22 capillaries/mm2) and pericyte coverage as an indicator of mature and functional capillaries (182+/-6 to 213+/-5 pericyte covered capillaries/mm2) in wildtype animals. Collateral number and collateral score (a branching index) both rose significantly upon AAV9-MRTF-A treatment, whereas the framecount for the contrast agent to travel from stent to ankle was significantly reduced (from 27+/-2 to 21+/-0.5 frames). Similar results were obtained in a diabetic pig cohort, using the InsC94Y pig, where significant increases of capillary and collateral growth, and a corresponding reduction in frame count score could be observed upon treatment.

In summary, we have established efficacy of AAV9-MRTF-A as a vasoactive agent for micro- and macrovessel growth in a preclinical large animal model, extending to a diabetic cohort as one of the most prevalent cardiovascular risk factor populations.