A study of neovascularization in the rat ischemic hindlimb using Araldite casting and Spalteholtz tissue clearing.

Understanding neovascularization is an important prerequisite for therapeutic advances aimed at the salvation of ischemic tissues. We explored an alternative strategy to corrosion casting for visualizing neovascularization in a rat hindlimb ischemia model. Rats were subjected to hindlimb ischemia by femoral artery ligation. Directly after femoral artery occlusion and at 7, 14, 21 and 28 days postsurgery, rats were sacrificed, and neovascularization was evaluated by vascular casting with Araldite plastic and subsequent Spalteholtz tissue clearing. Semitransparent preparations were obtained, in which the casted arteries could be directly and three-dimensionally visualized in detail and in relation to the surrounding tissue. In the vascular casts, collateral formation and recanalization of previously thrombosed arteries were demonstrated. We describe an alternative approach to study neovascularization in animal models. This method, which combines Araldite plastic vascular casting with Spalteholtz tissue clearing, preserves all vasculature as well as the surrounding tissue. In a small time series in rat ischemic hindlimbs, we show that restoration of blood flow after ischemia not only involves newly formed collaterals, but also recanalization of previously thrombosed arterial segments.