Lack of apoptosis in mitochondrial encephalomyopathies.

BACKGROUND/OBJECTIVE: Apoptosis, or programmed cell death, is an evolutionary conserved mechanism essential for morphogenesis and tissue homeostasis, but it plays an important role also in pathologic conditions, including neurologic disorders. Its execution pathway is critically regulated at the mitochondrial level. Evidence of apoptosis in muscle specimens was investigated in patients with genetically defined mitochondrial encephalomyopathies. METHODS: Thirty-three muscle biopsies from patients with genotypically different mitochondrial diseases (single and multiple deletions, A3243G/A8344G point mutations of the mitochondrial DNA) were studied. The terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) reaction was used as a marker of nuclear DNA fragmentation, as well as antibodies against pro- (Fas) or anti- (Bcl-2) apoptotic factors. Also, because one hallmark of apoptosis is morphologic, ultrastructural studies were performed on skeletal muscle from 18 of 33 patients, examining both phenotypically normal and ragged red fibers. RESULTS: In all muscle biopsies, no significant expression of either pro (Fas) and inhibiting (Bcl-2) apoptosis-related proteins was found, nor TUNEL positivity. This latter finding is confirmed by lack of morphologic evidence of apoptosis in all the fibers examined at the ultrastructural level. CONCLUSION: The authors' findings suggest that genetically determined defects of oxidative phosphorylation do not induce the apoptotic process and that apoptosis is not involved in the pathogenesis of mitochondrial disorders.

Critically ill patients: immunological evidence of inflammation in muscle biopsy.

AIM AND METHOD: To verify whether muscle necrosis in critically ill patients could be due to an inflammatory process, we tested muscle biopsies from five intensive care patients with different inflammation-specific immunocytochemical markers (antibodies anti-class I major histocompatibility complex products (class I MHCP or HLA I), membrane attack complex (MAC), T lymphocytes helper-inducer (CD4), cytotoxic (CD8) and pan-B-lymphocytes). RESULTS: In three patients muscle biopsy showed class I MHCP positivity on the surface membrane of several groups of fibres, mainly perifascicular, and scattered microvascular deposits of MAC. In the other two patients muscle biopsy did not show class I MHCP and MAC positivity. CONCLUSION: Our results suggest that inflammation may be a component of muscle damage in some critically ill patients.

Mitochondrial myopathy: correlation between oxidative defect and mitochondrial DNA deletions at single fiber level.

In situ hybridization combined with immunohistochemical techniques has been applied to study patients affected by mitochondrial myopathies with large mitochondrial (mt)DNA deletions. All patients' muscle biopsies showed ragged red fibers (RRFs) and cytochrome oxidase (COX) deficiency. Two digoxigenin-labeled, polymerase chain reaction (PCR)-amplified DNAs were used as probes. One probe was designed to hybridize only with wild-type mtDNAs, while the other recognized both wild-type and deleted mtDNAs. Concomitant immunocytochemical analysis using antibodies against subunits II, III, (encoded by mtDNA) and IV (encoded by nuclear DNA) of COX was carried out. In our patients deleted mtDNAs are overexpressed in COX-negative RRFs, while wild-type mtDNAs are decreased in the same fibers. Immunohistochemistry studies show that COX IV is overexpressed in RRFs and that COX II and COX III subunits are still present. Deleted mtDNAs are spatially segregated in muscle fibers, where they interfere with the local population of normal mitochondrial genomes, causing a regional deficiency of the mitochondrial respiratory activity.

Severe polyneuropathy in a patient with Churg-Strauss syndrome.

We describe the clinicopathologic features of a 56-year-old woman affected with Churg-Strauss syndrome with major peripheral nerve involvement. The patient presented with a 1-month history of mainly distal upper-limb symmetrical paresthesias and hypostenia (bilateral "wrist drop"), palpable purpura and eosinophilia. Multiple pulmonary infiltrates and asthma had been present since the age of 52. Skin biopsy demonstrated an eosinophilic necrotizing vasculitis. During the hospitalization she was submitted to cardiac, bronchopulmonary, renal, and gastrointestinal evaluation and EMG. Peripheral nerve and skeletal muscle biopsies were performed. Sural nerve biopsy showed a marked degree of demyelination. A perivascular cellular infiltrate within the epineurium was immunoreactive for T lymphocytes and macrophages. Strong HLA-DR immunostaining was present in the endoneurium. IgM, IgE and fibrinogen deposition was found in some epi- and endoneurial vessels. Muscle biopsy showed neurogenic changes and 1 thrombosed vessel surrounded by mononuclear cells. Membrane attack complex (MAC) deposition was present in a few capillaries and major histocompatibility complex products I (MHCP I) was expressed at the subsarcolemmal level in a few isolated perivascular muscle fibers. After immunosuppressive therapy, the patient showed progressive improvement of both clinical symptoms and neurophysiological parameters.

Sarcoglycan deficiency in a large Italian population of myopathic patients.

Autosomal recessive limb-girdle muscular dystrophies are a heterogeneous group of genetic diseases with a wide spectrum of clinical severity and age of onset; mutations in the gene encoding the dystrophin-associated sarcoglycan proteins (alpha, beta, gamma and delta) have recently been shown to cause some cases of these myopathies (primary sarcoglycanopathies, types 2D, 2E, 2C and 2F, respectively). In this study we have examined a large population of Italian myopathic patients to determine the frequency of (alpha-, beta- and gamma-sarcoglycan deficiency and to correlate molecular defects with clinical phenotypes; to exclude the presence of primary dystrophinopathies both genetic and immunological analysis of dystrophin was performed. We report 12 patients (10 male and 2 female) with deficiency of either one or more sarcoglycan proteins. They were aged 8-56 years with onset between 4 and 30 years of age; they all presented with either mild, moderate or severe limb-girdle involvement associated with elevated blood creatine kinase levels and myopathic pattern at EMG; one was also affected with a mild dilation cardiomyopathy. All patients, except one, showed pathological muscle histological changes. Absence of all three proteins always correlates with severe forms, whereas mild protein deficiencies or isolated partial alpha-sarcoglycan deficiency correlate with either severe, moderate or mild forms.