ICAM1 expression by the microvasculature impairs capillary perfusion which compromises hind limb ischemia recovery in diabetic mice

Abstract

Chronic limb threatening ischemia (CLTI), which is one of the major complications of diabetes, is associated with poor limb and cardiovascular prognoses, along with a dramatic decrease in life expectancy. However, the pathophysiology of this disease is poorly understood and therapeutic targets are missing. Our objective is to explore the contribution of endothelial dysfunction in the development of CLTI in diabetic mice. Hind limb ischemia (HLI) was induced by ligation and resection of the femoral artery in C57BL6/J male mice, in which insulin resistance was induced by a high fat diet, and hyperglycaemia was induced one month later by low dose streptozotocin administrations. According to our previous investigations, ischemic foot re-perfusion, assessed via laser doppler perfusion imaging, was significantly reduced in diabetic animal 28 days after HLI surgery was performed (ratio blood flow in the ischemic leg vs non ischemic leg = 0.27 ± 0.09 vs 0.44 ± 0.21 in control mice; P = 0.03), even though angiogenesis was identical in both groups. On the contrary, we found that impaired ischemic foot re-perfusion was associated with an increased endothelial cell activation attested by an increased ICAM1 expression (P < 0.0001). We then hypothesized that ICAM1, by interacting with white blood cells (WBC), may compromise the perfusion of capillaries with a diameter smaller than a WBC. Accordingly, we found that WBC circulation velocity in the microvasculature was significantly diminished in diabetic mice (533 ± 169 μm/s vs 960 ± 188 in control mice; P = 0.004) and associated with a decreased percentage of capillaries perfusion by BS-1 lectin (78.5 ± 10.5% vs 96.1 ± 5.7 in control mice; P = 0.03). With the aim to test whether ICAM1 overexpression may be responsible for impaired ischemic foot re-perfusion, diabetic mice were administered with anti-ICAM1 antibodies or isotype control for 14 days, starting 14 days after HLI surgery was performed. We found that anti-ICAM1 therapy significantly increased WBC circulation velocity within the microvasculature (779 ± 113 μm/s vs 447 ± 107 in mice treated with isotype control; P < 0.0001) and the percentage of perfused capillary (P = 0.009). Altogether, our results demonstrate that ICAM1 overexpression may compromise hind limb ischemia recovery in diabetic mice by decreasing WBC circulation velocity and impairing capillary perfusion.