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. 2024 Oct 7:23:1208-1225.
doi: 10.17179/excli2024-7592. eCollection 2024.

Ultrastructural alterations and mitochondrial dysfunction in skeletal muscle of peripheral artery disease patients: implications for early therapeutic interventions

Affiliations

Ultrastructural alterations and mitochondrial dysfunction in skeletal muscle of peripheral artery disease patients: implications for early therapeutic interventions

Dylan Wilburn et al. EXCLI J. .

Abstract

Peripheral artery disease (PAD) is an atherosclerotic condition that impairs blood flow to the lower extremities, resulting in myopathy in affected skeletal muscles. Improving our understanding of PAD and developing novel treatment strategies necessitates a comprehensive examination of cellular structural alterations that occur in the muscles with disease progression. Here we aimed to employ electron microscopy to quantify skeletal muscle ultrastructural alterations responsible for the myopathy of PAD. Fifty-two participants (22 controls, 10 PAD Stage II, and 20 PAD Stage IV) were enrolled. Gastrocnemius biopsies were obtained to determine mitochondrial respiration and oxidative stress. Skeletal muscle sarcomere, mitochondria, lipid droplets, and sarcoplasm were assessed using transmission electron microscopy and focused ion beam scanning electron microscopy. Controls and PAD Stage II patients underwent walking performance tests: 6-minute walking test, 4-minute walking velocity, and maximum graded treadmill test. We identified several prominent ultrastructural modifications in PAD gastrocnemius, including reduced sarcomere dimensions, alterations in mitochondria number and localization, myofibrillar disorientation, changes in lipid droplets, and modifications in mitochondria-lipid droplet contact area. These changes correlated with impaired mitochondrial respiration and increased ROS production. We observed progressive deterioration in mitochondrial parameters across PAD stages. Stage II PAD showed impaired mitochondrial function and structure, while stage IV exhibited further deterioration, more pronounced structural alterations, and a decrease in mitochondrial content. The walking performance of Stage II PAD patients was significantly reduced. Our findings suggest that pathological mitochondria play a key role in the skeletal muscle dysfunction of PAD patients and represent an important target for therapeutic interventions aimed at improving clinical and functional outcomes in this patient population. Our data indicate that treatments should be implemented early and may include therapies designed to preserve and enhance mitochondrial biogenesis and respiration, optimize mitochondrial-lipid droplet interactions, or mitigate oxidative stress. Translational Perspective: Peripheral artery disease (PAD) is characterized by skeletal muscle and mitochondrial dysfunction. Ultrastructural changes in skeletal muscle myofibers and mitochondria morphology can provide significant information on the PAD pathophysiology. Here, we investigated skeletal muscle and mitochondria morphological and functional changes at the sarcomere level and across the disease progression and have found that sarcomere lengths and mitochondria count and function are associated with disease progression, indicating loss of skeletal muscle contractile and metabolic function. Ultrastructural changes in the PAD skeletal muscle can provide significant information in the development of new treatments.

Keywords: intramyocellular lipids; mitochondria; muscle; peripheral artery disease; sarcomere atrophy; sarcoplasm.

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Conflict of interest statement

The authors declare no conflict of interest. The funding agencies had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.

Figures

Table 1
Table 1. Patient demographics
Table 2
Table 2. Correlations of mitochondrial morphology with mitochondrial function
Figure 1
Figure 1. Mitochondrial morphology is abnormal in PAD patients. In control sarcomeres, mitochondria located around the Z-disc (A1-2; black arrows) and in some cases extended throughout the length of the sarcomere and transversely near the locations where a Z-disc would typically be present (A2; dotted black arrow). In Stage II PAD patients (B1-2), there were less mitochondria per Z-disc (B1-2; black arrows) and mitochondrial clusters (MC) were evident (B2). In Stage IV PAD patients (C1-2), there were sparse mitochondria around the Z-disc with some mitochondria being present in the IMF (C1; white arrows). Quantitative measurements (D-G) demonstrated several abnormalities in the mitochondrial morphology in both PAD stages compared to controls.
Figure 2
Figure 2. Mitochondrial respiration and mitochondrial H2O2 production demonstrate significant limitations in PAD groups. Mitochondrial respiration was significantly reduced in several parameters (A-F) within the PAD stages when compared to controls, while H2O2 production (G-L) was significantly increased.
Figure 3
Figure 3. Figure 3 demonstrates the differences in sarcomere changes between control (A1-2), stage II (B1-2), and stage IV (C1-2) PAD patients. M-lines (M), Z-discs (Z), lipids (white arrows), triad (tr; black arrow), and intramyocellular lipids (IMCL). Quantitative measurements of relative myofibril area (D), number of z-discs per 250 μm2 (E), sarcomere M-line length (F), relative sarcoplasmic area (G), relative lipid droplet area (H), number of lipids droplets (I), average lipid droplet CSA (J), and IMCL-mitochondria contact length (K) are demonstrating significant differences between the groups.
Figure 4
Figure 4. Common abnormal structural features within stage II and stage IV PAD patients. A) Shows compartmentalized regions of linear z-discs (LZ) and wavy Z-discs (WZ) found directly adjacent to each other within a single fiber. B) Shows disorganization and disruption of individual myofibers that appear to have Z-disc smearing and a loss of normal identifiable features (arrows). C) Shows a larger region of sarcomere that appear to have also lost their identifiable features (arrows). D1-D3) Regions that display granular filamentous (GFM) material that is disorganized and electron dense (*) in the intermyofibrillar space. E1-E3) Shows irregular myofibril alignment (Imyo) with myofibrils displaying an oblique/anatomical orientation (O/A) directly adjacent to longitudinally oriented myofibrils. In E3, the lattice structure of the actin and myosin (A&M) filaments is visible next to sarcomeres in longitudinal orientation.
Figure 5
Figure 5. Video still image of the mitochondrial network (green) and IMCL (blue) in control (A), stage II (B), and stage IV (C) PAD patients. The mitochondrial network of Stage II PAD patients seems to be segmented compared to control and stage IV PAD patients.

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References

    1. Aweida D, Rudesky I, Volodin A, Shimko E, Cohen S. GSK3-beta promotes calpain-1-mediated desmin filament depolymerization and myofibril loss in atrophy. J Cell Biol. 2018;217:3698–3714. doi: 10.1083/jcb.201802018. doi: 10.1083/jcb.201802018. Available from: - DOI - DOI - PMC - PubMed
    1. Badin PM, Langin D, Moro C. Dynamics of skeletal muscle lipid pools. Trends Endocrinol Metab. 2013;24:607–615. doi: 10.1016/j.tem.2013.08.001. doi: 10.1016/j.tem.2013.08.001. Available from: - DOI - DOI - PubMed
    1. Bakeeva LE, Chentsov YS, Skulachev VP. Mitochondrial framework (reticulum mitochondrial) in rat diaphragm muscle. Biochim Biophys Acta. 1978;501:349–369. doi: 10.1016/0005-2728(78)90104-4. doi: 10.1016/0005-2728(78)90104-4. Available from: - DOI - DOI - PubMed
    1. Bapat GM, Bashir AZ, Malcolm P, Johanning JM, Pipinos, II, Myers SA. A biomechanical perspective on walking in patients with peripheral artery disease. Vasc Med. 2023;28(1):77–84. doi: 10.1177/1358863X221146207. doi: 10.1177/1358863X221146207. Available from: - DOI - DOI - PMC - PubMed
    1. Bergman BC, Hunerdosse DM, Kerege A, Playdon MC, Perreault L. Localisation and composition of skeletal muscle diacylglycerol predicts insulin resistance in humans. Diabetologia. 2012;55:1140–1150. doi: 10.1007/s00125-011-2419-7. doi: 10.1007/s00125-011-2419-7. Available from: - DOI - DOI - PMC - PubMed

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