Mitochondrial and Microvascular Impairments in a Novel Swine Model of Peripheral Artery Disease

Introduction: Impaired skeletal muscle mitochondria and microvascular function have been reported in human peripheral artery disease (PAD). However, no large animal models of PAD have mimicked these impairments. Purpose: The purpose of this study was to examine the skeletal muscle microvasculature and mitochondria in a novel swine model of PAD. Hypothesis: We hypothesized that hindlimb ischemia leads to dysfunction of skeletal muscle microvessels and mitochondria. Methods: Ossabaw swine (n=5) with metabolic syndrome underwent endovascular coil occlusion of the right external iliac artery to generate hindlimb ischemia (ISC). The left leg served as a non-ischemic control (CON). After 4-weeks, biopsies were collected from both legs (lateral gastrocnemius). Skeletal muscle arterioles were assessed using video microscopy. Microvascular vasodilatory function was assessed in response to flow (Shear stress), acetylcholine (ACh), and sodium nitroprusside (SNP). Skeletal muscle mitochondrial function was assessed using high-resolution respirometry. Substrates were administered as follows: malate (M) & glutamate (G), adenosine diphosphate (ADP), succinate (S), oligomycin, and ascorbate (Asc) & N,N,N,N-tetramethyl-phenylenediamine (TMPD). Complex I state 2 (CI-S2) was assessed as M+G, complex I state 3 (CI-S3) was assessed as (M+G+ADP)-(M+G), complex II state 3 (CII-S3) was assessed as (M+G+ADP+S)-(M+G+ADP), complex I&II state 3 (CI&II S3) was assessed as (M+G+ADP+S)-(M+G), state 4 (S4) was assessed after oligomycin, and complex IV (CIV) respiration was assessed after Asc+TMPD. The respiratory control ratio (RCR) was calculated as CI&II-S3/S4. Results: Vasodilation in response to flow was reduced in ISC vs. CON (Δ-13.1±13.7%, p=0.01). but not in response to ACh (Δ-6.2±17.7%, p=0.23) or SNP (Δ1.7±11.0%, p=0.53). Additionally, CI-S2 (Δ-0.3±3.7 pmolO 2 ·s −1 ·mg −1 , p=0.65), S4 (Δ-1.7±4.4 pmolO 2 ·s −1 ·mg −1 , p=0.14), and CIV (Δ-2.8±20.9 pmolO 2 ·s −1 ·mg −1 , p=0.65) were not different between ISC and CON. However, CI-S3 (Δ-4.7±5.0 pmolO 2 ·s −1 ·mg −1 , p<0.01), CII-S3 (Δ-3.5±5.0 pmolO 2 ·s −1 ·mg −1 , p=0.02), CI&II-S3 (Δ-8.5±8.7 pmolO 2 ·s −1 ·mg −1 , p<0.01), and RCR (Δ-0.8±1.3 pmolO 2 ·s −1 ·mg −1 , p=0.04) were all reduced in ISC vs. CON. Conclusions: We found that skeletal muscle microvessels and mitochondria were impaired in our swine model. Based on the present findings, we conclude that our novel porcine model closely replicates the pathophysiology PAD, making it a promising large animal model for studying human PAD. This research was supported by the National Institutes of Health (R01HD106911, R01AG062198, R01AG0778031) and the Great Plains IdeA-CTR (U54 GM115458). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.