Abstract 21467: Femoral Artery Regeneration by Hypoxia-Regulated Conditionally Silenced Vegf Delivered to Severely Ischemic Muscle by Aav9.
Introduction: Clinical trials of therapeutic angiogenesis for coronary and peripheral artery disease have shown limited success.
Rationale: Previous gene therapy protocols focused on angiogenesis with two major flaws: (1) inadequate delivery vehicles (2) use of unregulated genes with no directional cues for new vessel growth.
Hypothesis: VEGF gene delivery in a semi-permanent muscle-tropic AAV9 vector with tight hypoxia-regulation supports sustained, directional arteriogenesis and limb salvage.
Methods: The human (h)VEGF gene driven by a PGK promoter containing tandem arrays of HIF-1α and neuronal silencer factor (NSF) binding sites was cloned into AAV9 (CS-AAV-VEGF). Gene expression and conditional silencing (CS) were confirmed in vitro and in vivo in skeletal and cardiac myocytes and ischemic hind limbs of BalbC mice. Arteriogenesis was visualized in ischemic limbs by scanning confocal imaging of DiI-stained muscle and MRI up to 1-yr follow up.
Results: CS-AAV-VEGF showed high tropism for ischemic muscle with an intense wave of gene expression that reached >100-fold that of non-ischemic muscle 1-week after ischemia and declined thereafter in parallel with HIF-1α. Fig. 1 shows representative sections of CS-AAV-VEGF-treated muscle at 1, 12, 16, and 52 weeks; the arrows indicate the femoral groove and nerve underlying the excised femoral artery. The figure shows progressive growth and expansion of an artery within the groove that reached equivalent dimensions to the excised FA at 1-year post-treatment. Such FA regeneration was not seen with PBS (bottom panel) or Ad-CMV-VEGF (not shown) and only CS-AAV-VEGF conferred 100% limb salvage.
Conclusions: Sustained, ischemia-regulated VEGF expression supports FA regeneration and limb salvage. Down-regulation of the transgene coincident with revasculatization provides a safety switch that will allow clinical translation of this strategy to treat peripheral artery disease.
- © 2010 by American Heart Association, Inc.