Abstract 15176: Development of Femoral Artery Denervation Models for Vascular Remodeling

Abstract

Introduction: Restenosis is a common cause of vascular device failure. An important contributor is the transdifferentiation of vascular smooth muscle cells (VSMCs) from a contractile to synthetic phenotype. Healthy arteries are innervated by sympathetic nerves to regulate VSMC contractility and phenotype, yet this interaction has been overlooked in pathological vascular remodeling such as restenosis. Hypothesis: Sympathetic denervation of the femoral artery will lead to transdifferentiation of arterial VSMC and pathological remodeling of the arterial structure. Methods: The femoral arteries of male BALB/c mice were surgically exposed and treated with specific dopaminergic neurotoxin 6-hydroxydopamine (6-OHDA) or vehicle for 5 minutes. In the model of long-term denervation, the mice were subcutaneously injected with 6-OHDA or vehicle weekly for 4 weeks. Femoral arteries and peri-adventitial tissue were harvested for histology. Innervation density was calculated as the number of sympathetic nerve fibers (tyrosine hydroxylase-positive) normalized to the medial layer area (α-smooth muscle actin-positive). Extracellular matrix (ECM) composition was visualized with Masson’s trichrome and Verhoeff's elastic staining. Results: One week after surgery, 6-OHDA-treated arteries had a notable reduction in sympathetic nerve density compared to controls (2.9 vs. 11.7 fibers/10,000 μm 2 [P=.22, n=2]). This difference decreased at 2 weeks (6.8 vs. 8.0 fibers/10,000 μm 2 [P=0.50, n=3]) and at 4 weeks (4.4 vs. 5.0 fibers/10,000 μm 2 [P=0.83, n=3]), suggesting nerve recovery. No difference was observed in ECM composition. Tissues harvested at 1 and 4 weeks in the 6-OHDA injection model demonstrate qualitative denervation of the treated limb compared to control. Conclusions: Sympathetic denervation of murine femoral arteries can be achieved by direct surgical application or subcutaneous injection of 6-OHDA. Future work will characterize vascular remodeling after long-term denervation and combine denervation with vascular injury. If a causal relationship can be identified between sympathetic denervation and VSMC pathology, engineering reinnervation could be a viable approach for future graft design.