Abstract 335: Macrophage Interleukin-1 Beta Dependent Angiogenesis During Wound Healing

Abstract

Angiogenesis during wound healing is thought to require an inflammation suppressed state. However, there is growing evidence that early infiltrating inflammatory macrophages may play an important role in setting the stage for angiogenesis. Here we sought to understand the relationship between the potent inflammatory cytokine, IL-1β, and vascular endothelial growth factor-A (VEFG-A) in the context of two experimental models of angiogenesis-dependent healing: skin punch biopsy and hind limb ischemia. We established a macrophage-specific IL-1 β -deletion model ( mIL-1 β ) to study the relationship between IL-1β and VEGF-A in the context of these models. Using a punch biopsy model, wounds were quantified, showing remarked expansion of the wounds in mIL-1 β -deleted mice on day 2 of the healing process, resulting in slower wound closure. Analysis from mIL-1 β -deleted mice confirmed decreased macrophage expression of IL-1β and VEGF-A early at day two post-wounding by punch biopsy. In our second approach, we used femoral artery ligation to demonstrate hind limb ischemia. We hypothesized that mIL-1 β -deleted mice would exhibit reduced blood flow recovery due to impaired angiogenesis. Analysis from mIL-1 β -deleted mice indicates reduced IL-1β and VEGF-A expression. In establishing a pathway of IL-1β-dependent macrophage VEGF-A upregulation in the acute injury state, we examined transcriptional factors STAT3 and NF-κB. Constitutively active STAT3 and IKK-2 (NF-κB activator) appear to increase VEGF-A expression, while inhibition of STAT3 and NF-κB exhibits a dose-dependent reduction of VEGF-A expression. In summary, two models of angiogenesis-dependent healing from injury indicate that macrophage VEGF-A expression is dependent on IL-1β expression during early inflammation. Strategies to alleviate impaired wound healing where VEGF-A levels may not be sufficient could require upregulation of the downstream effectors of IL-1β to restore macrophage VEGF-A expression levels required for adequate angiogenesis.