Arteriolar remodeling following ischemic injury extends from capillary to large arteriole in the microcirculation.

OBJECTIVE: Skeletal muscle vasculature undergoes arteriogenesis to restore tissue perfusion and function following loss of blood flow. This process has been shown to occur in large vessels following ischemia, although recent studies suggest this may occur in the microcirculation as well. We tested the hypothesis that ischemia induces microvascular remodeling in the skeletal muscle microcirculation on the scale of capillary to sub-35 mum diameter arterioles. METHODS: Ligations of a feeding arteriole to the caudal-half of the spinotrapezius muscle were performed on C57BL/6 mice. At 5 days, microvascular remodeling responses were quantified using intravital and whole-mount confocal microscopy. Immunohistochemistry was performed to visualize vessels, incorporated leukocytes, and regions of hypoxia. RESULTS: Ischemic tissue underwent localized microvascular remodeling characteristic of arteriogenesis, including pronounced vessel tortuosity. In patent microvessels (diameters 15-35 microm), we observed increases in vascular density (38%), branching (90%) and collateral development (36.5%). The formation of new arterioles (diameters 6-35 microm) increased by 24.3%, while chronic hypoxia was absent from all tissues. CONCLUSIONS: Ischemic injury induces arteriogenesis in skeletal muscle microcirculation. Furthermore, this surgical model enables en face analysis of microcirculatory adaptations with single-cell resolution and can provide investigators with morphometric data on a microscale that is difficult to achieve using other models.