Abnormal myofiber morphology and limb dysfunction in claudication

Background Peripheral artery disease (PAD), which affects an estimated 27 million people in Europe and North America, is caused by atherosclerotic plaques that limit blood flow to the legs. Chronic, repeated ischemia in the lower leg muscles of PAD patients is associated with loss of normal myofiber morphology and myofiber degradation. In this study, we tested the hypothesis that myofiber morphometrics of PAD calf muscle are significantly different from normal calf muscle and correlate with reduced calf muscle strength and walking performance. Methods Gastrocnemius biopsies were collected from 154 PAD patients (Fontaine stage II) and 85 control subjects. Morphometric parameters of gastrocnemius fibers were determined and evaluated for associations with walking distances and calf muscle strength. Results Compared with control myofibers, PAD myofiber cross-sectional area, major and minor axes, equivalent diameter, perimeter, solidity, and density were significantly decreased (P \u3c 0.005), whereas roundness was significantly increased (P \u3c 0.005). Myofiber morphometric parameters correlated with walking distances and calf muscle strength. Multiple regression analyses demonstrated myofiber cross-sectional area, roundness, and solidity as the best predictors of calf muscle strength and 6-min walking distance, whereas cross-sectional area was the main predictor of maximum walking distance. Conclusions Myofiber morphometrics of PAD gastrocnemius differ significantly from those of control muscle and predict calf muscle strength and walking distances of the PAD patients. Morphometric parameters of gastrocnemius myofibers may serve as objective criteria for diagnosis, staging, and treatment of PAD

Abnormal Accumulation of Desmin in Gastrocnemius Myofibers of Patients with Peripheral Artery Disease: Associations with Altered Myofiber Morphology and Density, Mitochondrial Dysfunction and Impaired Limb Function

Patients with peripheral artery disease (PAD) develop a myopathy in their ischemic lower extremities, which is characterized by myofiber degeneration, mitochondrial dysfunction and impaired limb function. Desmin, a protein of the cytoskeleton, is central to maintenance of the structure, shape and function of the myofiber and its organelles, especially the mitochondria, and to translation of sarcomere contraction into muscle contraction. In this study, we investigated the hypothesis that disruption of the desmin network occurs in gastrocnemius myofibers of PAD patients and correlates with altered myofiber morphology, mitochondrial dysfunction, and impaired limb function. Using fluorescence microscopy, we evaluated desmin organization and quantified myofiber content in the gastrocnemius of PAD and control patients. Desmin was highly disorganized in PAD but not control muscles and myofiber content was increased significantly in PAD compared to control muscles. By qPCR, we found that desmin gene transcripts were increased in the gastrocnemius of PAD patients as compared with control patients. Increased desmin and desmin gene transcripts in PAD muscles correlated with altered myofiber morphology, decreased mitochondrial respiration, reduced calf muscle strength and decreased walking performance. In conclusion, our studies identified disruption of the desmin system in gastrocnemius myofibers as an index of the myopathy and limitation of muscle function in patients with PAD

LC3 and p62 as diagnostic markers of drug-induced autophagic vacuolar cardiomyopathy: a study of 3 cases

Autophagic vacuolar cardiomyopathy is an underrecognized, but potentially fatal, complication of treatment with chloroquine (CQ) and its derivative hydroxychloroquine (HCQ), which are used as therapy for malaria and common connective tissue disorders. Currently, the diagnosis of autophagic vacuolar cardiomyopathy is established through an endomyocardial biopsy and requires electron microscopy, which is not widely available and has a significant potential for sampling error. Recently, we have reported that immunohistochemistry for autophagic markers LC3 and p62 can replace electron microscopy in the diagnosis of HCQ-induced and colchicine-induced autophagic vacuolar skeletal myopathies. In the current study, we use 3 cases of CQ-induced or HCQ-induced cardiomyopathy and 1 HCQ-treated control case to show that the same two markers can be used to diagnose autophagic vacuolar cardiomyopathies by light microscopy. CQ-induced or HCQ-induced autophagic vacuolar cardiomyopathy is not universally fatal, but successful treatment requires early detection. By lowering the barriers to diagnosis, the application of these immunohistochemical markers will decrease the number of misdiagnosed patients, thus increasing the likelihood of favorable clinical outcomes

LC3 and p62 as Diagnostic Markers of Drug-induced Autophagic Vacuolar Cardiomyopathy

Autophagic vacuolar cardiomyopathy is an under recognized, but potentially fatal, complication of treatment with chloroquine (CQ) and its derivative hydroxychloroquine (HCQ), which are used as therapy for  malaria and common connective tissue disorders. Currently, the diagnosis of autophagic vacuolar cardiomyopathy is established through an endomyocardial biopsy and requires electron microscopy, which is not widely available and has a significant potential for sampling error. Recently, we have reported that immunohistochemistry for autophagic  markers LC3 and p62 can replace electron microscopy in the diagnosis of HCQ- and  colchicine-induced autophagic vacuolar skeletal myopathies. In the current study, we use three cases of CQ- or HCQ-induced cardiomyopathy and one HCQ-treated control case to show that the same twomarkers can be used to diagnose autophagic vacuolar cardiomyopathies by light microscopy. CQ- or HCQ-induced autophagic vacuolar cardiomyopathy is not universally fatal, but successful treatment requires early detection. By lowering the barriers to diagnosis, the application of these immunohistochemical markers will decrease the number of misdiagnosedpatients, thus increasing the likelihood of favorable clinical outcomes

LC3 and p62 as Diagnostic Markers of Drug-induced Autophagic Vacuolar Cardiomyopathy

Autophagic vacuolar cardiomyopathy is an under recognized, but potentially fatal, complication of treatment with chloroquine (CQ) and its derivative hydroxychloroquine (HCQ), which are used as therapy for  malaria and common connective tissue disorders. Currently, the diagnosis of autophagic vacuolar cardiomyopathy is established through an endomyocardial biopsy and requires electron microscopy, which is not widely available and has a significant potential for sampling error. Recently, we have reported that immunohistochemistry for autophagic  markers LC3 and p62 can replace electron microscopy in the diagnosis of HCQ- and  colchicine-induced autophagic vacuolar skeletal myopathies. In the current study, we use three cases of CQ- or HCQ-induced cardiomyopathy and one HCQ-treated control case to show that the same twomarkers can be used to diagnose autophagic vacuolar cardiomyopathies by light microscopy. CQ- or HCQ-induced autophagic vacuolar cardiomyopathy is not universally fatal, but successful treatment requires early detection. By lowering the barriers to diagnosis, the application of these immunohistochemical markers will decrease the number of misdiagnosedpatients, thus increasing the likelihood of favorable clinical outcomes

Oxidative damage in the gastrocnemius of patients with peripheral artery disease is myofiber type selective

Background: Peripheral artery disease (PAD), a manifestation of systemic atherosclerosis that produces blockages in the arteries supplying the legs, affects approximately 5% of Americans. We have previously, demonstrated that a myopathy characterized by myofiber oxidative damage and degeneration is central to PAD pathophysiology. Objectives: In this study, we hypothesized that increased oxidative damage in the myofibers of the gastrocnemius of PAD patients is myofiber-type selective and correlates with reduced myofiber size. Methods: Needle biopsies were taken from the gastrocnemius of 53 PAD patients (28 with early PAD and 25 with advanced PAD) and 25 controls. Carbonyl groups (marker of oxidative damage), were quantified in myofibers of slide-mounted tissue, by quantitative fluorescence microscopy. Myofiber cross-sectional area was determined from sarcolemma labeled with wheat germ agglutinin. The tissues were also labeled for myosin I and II, permitting quantification of oxidative damage to and relative frequency of the different myofiber Types (Type I, Type II and mixed Type I/II myofibers). We compared PAD patients in early (N=28) vs. advanced (N=25) disease stage for selective, myofiber oxidative damage and altered morphometrics. Results: The carbonyl content of gastrocnemius myofibers was higher in PAD patients compared to control subjects, for all three myofiber types (p<0.05). In PAD patients carbonyl content was higher (p<0.05) in Type II and I/II fibers compared to Type I fibers. Furthermore, the relative frequency and cross-sectional area of Type II fibers were lower, while the relative frequencies and cross-sectional area of Type I and Type I/II fibers were higher, in PAD compared to control gastrocnemius (p<0.05). Lastly, the type II-selective oxidative damage increased and myofiber size decreased as the disease progressed from the early to advanced stage. Conclusions: Our data confirm increased myofiber oxidative damage and reduced myofiber size in PAD gastrocnemius and demonstrate that the damage is selective for type II myofibers and is worse in the most advanced stage of PAD