Abstract 5585: Inhibition of Notch Signalling by Soluble Form of Delta-like 4 Converts Reparative Angiogenesis Into Inefficient Inflammatory-like Neovascularization in a Murine Model of Peripheral Ischemia
Notch signalling by the ligand Delta-like 4 (Dll4) was previously shown to be absolutely required for normal embryonic vascular development and is involved in tumour angiogenesis. In this study, we aimed to define the effect of inhibition of Dll4-mediated signalling in ischemia-induced angiogenesis. An adenovirus encoding soluble Dll4 (AdsDll4) or empty vector (control) was injected in murine ischemic limb muscles (n=15 per group). Analysis of AdsDll4 treated muscles by PCR showed that Notch downstream genes were downregulated compared to control. Five days following ischemia induction, whole-mount immunostaining technique was applied to visualize and analyze vessel architecture in 3D by confocal microscopy. In AdsDll4-treated ischemic muscle, neo-vessel network was considerably disrupted and contained more sprouting endothelial cells (Fig⇓). Interestingly, we observed a strong accumulation of infiltrating inflammatory CD45 positive cells in the AdsDll4-treated ischemic muscle compared to control (958±252 vs 378±131 cell/mm2, p<0.0005). Blood flow recovery was impaired in AdsDll4 treated animals with compared to control measured by Laser Doppler Perfusion Imaging (perfusion ratio: 0.49±0.2 vs 0.74±0.1, p=0.02, 7 days after ischemia). Furthermore, the perfused vessels visualized by lectin infusion of live animals were markedly reduced in AdsDll4 treated group in comparison to control. In conclusion, our findings suggest that Notch/Dll4 signaling could play a crucial role in ischemia-induced angiogenesis not only by regulating vascular sprouting but also coordinating the cross-talk between infiltrating inflammatory cells and endothelial cells.