Novel method to assess arterial insufficiency in rodent hind limb

Abstract

Background Lack of techniques to assess maximal blood flow capacity thwarts the use of rodent models of arterial insufficiency to evaluate therapies for intermittent claudication. We evaluated femoral vein outflow (VO) in combination with stimulated muscle contraction as a potential method to assess functional hindlimb arterial reserve and therapeutic efficacy in a rodent model of subcritical limb ischemia. Materials and methods VO was measured with perivascular flow probes at rest and during stimulated calf muscle contraction in young healthy rats (Wistar Kyoto, WKY; lean Zucker, LZR) and rats with cardiovascular risk factors (Spontaneously Hypertensive, SHR; Obese Zucker, OZR) with acute and/or chronic femoral arterial occlusion. Therapeutic efficacy was assessed by administration of Ramipril or Losartan to SHR after femoral artery excision. Results VO measurement in WKY demonstrated the utility of this method to assess hindlimb perfusion at rest and during calf muscle contraction. While application to diseased models (OZR, SHR) demonstrated normal resting perfusion compared to contralateral limbs, a significant reduction in reserve capacity was uncovered with muscle stimulation. Administration of Ramipril and Losartan demonstrated significant improvement in functional arterial reserve. Conclusion The results demonstrate that this novel method to assess distal limb perfusion in small rodents with subcritical limb ischemia is sufficient to unmask perfusion deficits not apparent at rest, detect impaired compensation in diseased animal models with risk factors, and assess therapeutic efficacy. The approach provides a significant advance in methods to investigate potential mechanisms and novel therapies for subcritical limb ischemia in pre-clinical rodent models.

Assessing the hemodynamic contribution of capillaries, arterioles, and collateral arteries to vascular adaptations in arterial insufficiency

“…Similarly, the gradual increase in diameter and number of vessels that results in trained animals or people is assumed to be similar to the expected capacity for structural adaptation on a chronic time frame to an occlusion, as described in Ref . The model is also used to predict the degree of collateral dilation required to achieve experimentally observed flow values in the rat hindlimb following a major arterial occlusion under resting and maximal exercise conditions . The theoretical modeling procedure is summarized in the sections below.…”

“…Previously obtained experimental measures of flow in the rat hindlimb are used in this study to predict the degree of collateral vessel dilation that would be necessary to achieve the flow measured in these experiments in the presence or absence of other simulated vascular adaptations. Ziegler et al measured hindlimb perfusion in young healthy Wistar Kyoto rats under non‐occluded and occluded conditions at rest and during electrically stimulated calf muscle contraction.…”

“…Model predicted flow values when simulating acute vascular responses are compared with venous flow data collected within three minutes of occlusion . Model predicted flow values when simulating chronic vascular responses are compared with venous flow data collected two weeks post‐ligation .…”

“…Model predicted flow values when simulating acute vascular responses are compared with venous flow data collected within three minutes of occlusion . Model predicted flow values when simulating chronic vascular responses are compared with venous flow data collected two weeks post‐ligation . Femoral venous outflow values at contraction frequencies of 0 Hz and 12 Hz induced by electrical field stimulation were used to compare model simulations of resting and exercising conditions, respectively.…”

“…Femoral venous outflow values at contraction frequencies of 0 Hz and 12 Hz induced by electrical field stimulation were used to compare model simulations of resting and exercising conditions, respectively. Table provides a summary of the flow ratios (defined as the ratio of experimental case flow to resting non‐occluded flow) measured by Ziegler et al in the rat hindlimb under resting and maximally stimulated conditions.…”