Abstract 233: Intra-arterial Uridine 5’-triphosphate (UTP) Increases Macrophage/Monocyte Recruitment in the Developing Collateral After Femoral Artery Ligation

Abstract

Objectives: Arteriogenesis is a process by which small resistance vessels mature into large caliber collateral arteries in response to arterial occlusive disease. Inflammatory cells of monocyte/macrophage lineage are necessary to promote vascular remodeling. We have previously reported that mice lacking the P2Y2 receptor, a purinergic receptor whose agonists include ATP and UTP, exhibited impaired collateral development and persistently reduced perfusion when subjected to femoral artery ligation (FAL). Thus, we hypothesize that purinergic signaling via the P2Y2 receptor mediates inflammatory cell recruitment during arteriogenesis. Methods: C57Bl6 mice underwent FAL and intra-arterial infusion of 200uL of PBS or 100uM UTP in PBS (N=3 each group). Hindlimb perfusion was assessed with laser Doppler imaging at day 7. In a separate experiment, P2Y2 -/- mice underwent femoral artery ligation alongside C57Bl/6 (wild type receptor) mice without UTP infusion. Thigh adductor muscles were fixed, sectioned, and immunostaining was performed for inflammatory cells (anti-CD45) and macrophages/monocytes (anti-F4/80). Two collateral vessels were analyzed per animal, and positive cells were quantified per high-power field. Results: UTP treated mice showed a trend toward increased peri-collateral CD45 positive cells at 12hr, and significantly increased F4/80 positive cells at day 3 (18.3+/-3.3 vs 11.5+/-1.3, p=0.044). This corresponded to improved perfusion at 7 days in UTP treated mice (58.5%+/-3.9 vs 36.0%+/-2.8, p=0.026). P2Y2 -/- mice recruited fewer F4/80 positive cells to the collateral vessels at day 3 when compared to the wild type (1.8 ± 1.3 vs 11.8 ± 2.9, p=.012). Conclusion: UTP treatment increases macrophage recruitment to the immature collateral vessel wall and improves perfusion recovery following FAL. In the absence of P2Y2 receptor, macrophage recruitment was significantly inhibited. These findings suggest that purinergic signaling via the P2Y2 receptor is an important mediator of vascular inflammation which is required for collateral growth. Ongoing studies will focus on the cellular mechanisms involved and whether enhanced collateral maturation and limb perfusion can be driven by the pharmacologic administration of nucleotides.