Foot pad skin biopsy in mouse models of hereditary neuropathy

Numerous transgenic and knockout mouse models of human hereditary neuropathies have become available over the past decade. We describe a simple, reproducible, and safe biopsy of mouse skin for histopathological evaluation of the peripheral nervous system (PNS) in models of hereditary neuropathies. We compared the diagnostic outcome between sciatic nerve and dermal nerves found in skin biopsy (SB) from the hind foot. A total of five animal models of different Charcot-Marie-Tooth neuropathies, and one model of congenital muscular dystrophy associated neuropathy were examined. In wild type mice, dermal nerve fibers were readily identified by immunohistochemistry, light, and electron microscopy and they appeared similar to myelinated fibers in sciatic nerve. In mutant mice, SB manifested myelin abnormalities similar to those observed in sciatic nerves, including hypomyelination, onion bulbs, myelin outfolding, redundant loops, and tomacula. In many strains, however, SB showed additional abnormalities--fiber loss, dense neurofilament packing with lower phosphorylation status, and axonal degeneration-undetected in sciatic nerve, possibly because SB samples distal nerves. SB, a reliable technique to investigate peripheral neuropathies in human beings, is also useful to investigate animal models of hereditary neuropathies. Our data indicate that SB may reveal distal axonal pathology in mouse models and permits sequential follow-up of the neuropathy in an individual mouse, thereby reducing the number of mice necessary to document pathology of the PNS.     

Content validity of symptom‐based measures for diabetic,chemotherapy, and HIV peripheral neuropathy

Introduction: No treatments for axonal peripheral neuropathy are approved by the United States Food and Drug Administration (FDA). Although patient‐ and clinician‐reported outcomes are central to evaluating neuropathy symptoms, they can be difficult to assess accurately. The inability to identify efficacious treatments for peripheral neuropathies could be due to invalid or inadequate outcome measures. Methods: This systematic review examined the content validity of symptom‐based measures of diabetic peripheral neuropathy, HIV neuropathy, and chemotherapy‐induced peripheral neuropathy. Results: Use of all FDA‐recommended methods to establish content validity was only reported for 2 of 18 measures. Multiple sensory and motor symptoms were included in measures for all 3 conditions; these included numbness, tingling, pain, allodynia, difficulty walking, and cramping. Autonomic symptoms were less frequently included. Conclusions: Given significant overlap in symptoms between neuropathy etiologies, a measure with content validity for multiple neuropathies with supplemental disease‐specific modules could be of great value in the development of disease‐modifying treatments for peripheral neuropathies. Muscle Nerve 55 : 366–372, 2017     

An approach to the evaluation of peripheral neuropathies

Requests for an evaluation for a peripheral neuropathy are common in the clinic and electrodiagnostic laboratory. Lists of types of neuropathies are long as are diagnostic tests. An approach to the evaluation of peripheral neuropathies is valuable as it permits full characterization of the neuropathy after which the lists of possible types and tests becomes much shorter and manageable. In this article, the author presents such an approach, focusing on the clinical aspects.     

Treatment of peripheral neuropathies with neutrotrophic factors: animal models and clinical trials

In vitro experiments and works with knock-out mice have demonstrated the physiological importance of neurotrophic factors (NF) in the development and the survival of peripheral nervous system neurons. Therefore, NF may be useful in the treatment of peripheral neuropathies. These pathologies may be more amenable than central nervous diseases to the systemic delivery of NF. Indeed, NF can readily access peripheral nerves from blood whereas penetration into the central nervous system is limited by the blood-brain barrier. The objectives of NF treatment are: 1) to compensate a putative deficiency of NF associated with the pathogenesis of some neuropathies, such as diabetic neuropathy; 2) to stop or slow disease progression by acting on the biochemical pathways involved in the neurodegenerative cascade; and 3) to enhance the physiological compensatory mechanism of axonal sprouting. The efficacy of treatment with NF has been demonstrated in animal models mimicking various neuropathies, such as neuropathies related to diabetes or treatment with chemotherapeutic agents. However, a phase 3 trial in diabetic neuropathy and a phase 2 trial in HIV-related neuropathy have failed to demonstrate any substantial effect of treatment with NGF. In this review, we discuss the factors that may explain these negative results. A major limitation of systemic administration is the poor bioavailability of NF due to their short half-life. Alternative modes of delivery may be more appropriate than systemic administration of the recombinant protein. In particular, muscular-based gene therapy allows the delivery of sustained levels of neurotrophic factor into the circulation. This strategy has shown to be effective in animal models of motor and sensory neuropathies. Another promising treatment is the use of small molecules that induce the endogenous synthesis of NF, such as xaliprodene or 4-methylcathecol.     

Neurotrophic factors and diabetic peripheral neuropathy

Recent evidence from animal models of diabetes and human diabetic subjects suggests that the reduced availability of neurotrophic factors may contribute to the pathogenesis of diabetic peripheral neuropathy (DPN). Of these proteins, nerve growth factor (NGF), brain-derived neurotrophic factor, neurotrophin (NT-3) and NT-4/5 appear to be important for the development and maintenance of peripheral neurons, but others, including insulin-like growth factors (IGFs), may also be involved. Studies with NGF, NT-3, IGF-I and IGF-II both in vitro and in animal models of neuropathies (including DPN) suggest that these factors ameliorate nerve degeneration. Recombinant human NGF is the first neurotrophic factor to enter clinical trials for DPN and is currently being tested in two phase III studies.     

Modèles animaux dans la maladie de Charcot-Marie-Tooth et applications de la compréhension de la maladie chez l’homme

Charcot-Marie-Tooth neuropathies (CMT) are inherited neuromuscular disorders caused by length-dependent neurodegeneration of peripheral nerves. More than 900 mutations in 60 different genes are responsible for Charcot-Marie-Tooth neuropathy. Despite significant progress in therapeutic strategies, the disease remains incurable. The increasing number of genes linked to the disease, and their considerable clinical and genetic heterogeneity renders the development of these strategies particularly challenging. In this context, cellular and animals models provide powerful tools. Efficient motor and sensory tests have been developed to assess the behavioral phenotype in transgenic animal models (rodents and fly). When these models reproduce a phenotype comparable to CMT, they allow therapeutic approaches and the discovery of modifiers and biomarkers. The majority of these models concern the demyelinating form (type 1) of the disease. The axonal form (type 2) is less common. Both forms can further be divided into multiple subtypes reflecting the heterogeneity of the disease. In this review, we describe the most convincing transgenic rodent and fly models of CMT and how some of them led to clinical trials.     

Evaluation tools and animal models of peripheral neuropathies

Peripheral neuropathies are common and frequently debilitating disorders linked to degeneration of peripheral nerves that supply mainly the distal muscles of the extremities. Due to the diverse origin of the pathology (genetic, systemic or environmental), peripheral neuropathies exhibit different clinical forms: acute or chronic, symmetrical or asymmetrical, demyelinating or axonal. In the last 30 years, to gain insight into cellular and molecular mechanisms underlying neuropathies, numerous animal models--either spontaneous or induced by chemical compounds, physical injury or genetic engineering--have been extensively developed and used. In this review, we present (1) the methods used to assess the peripheral neuropathies in the major available animal models and their main pathological characteristics and (2) the main models and their relevance to the human pathology, and, consequently, their usefulness for preclinical studies. Finally, we discuss the emerging, recently developed tools, that should allow to gain a better insight into the mechanisms underlying the peripheral neuropathies.     

Biological actions of nerve growth factor in the peripheral nervous system

Since the discovery of nerve growth factor (NGF), its role in the physiology/pathophysiology of nerve function has been under intense investigation. More recently, the potential of recombinant human NGF (rhNGF) as a putative treatment for peripheral neuropathies, in particular diabetic polyneuropathy and HIV-associated sensory neuropathy, is being explored. In animal models of diabetes, depletion of endogenous NGF levels has been demonstrated in foot skin and skeletal muscle; these levels reduce further with increasing disease duration. Preclinical studies in animal models of diabetes have shown that administration of NGF can reverse or alleviate impairment in nerve function.     

Impairment,disability, or handicap in peripheral neuropathy: analysis of the use of outcome measures in clinical trials in patients with peripheral neuropathies.

Outcome measures can be classified into measures of impairment, disability, and handicap. To investigate the biological effect of treatment, measures of impairment are appropriate. Studies investigating whether patients benefit from treatment in terms of improvement of functional health, however, require disability or handicap measures. In a review of the medical literature between 1978 and 1993, 73 controlled intervention studies in patients with peripheral neuropathies were found. Disability or handicap measures were used in two of 54 studies in patients with diabetic neuropathy, in two of six studies in patients with chronic inflammatory demyelinating polyneuropathy, in none of five studies in a mixed group of patients, and in all eight studies in patients with Guillain-Barré syndrome. The limited use of disability and handicap measures in patients with diabetic and mixed neuropathies can be explained by the experimental nature of most studies. In four of six studies, however, in patients with chronic inflammatory demyelinating polyneuropathy or neuropathy associated with monoclonal gammopathy that were designed to assess effectiveness of treatment, the choice of outcome measures was not appropriate. It is concluded that in the design of intervention studies in patients with peripheral neuropathy more attention should be paid to a proper choice of suitable outcome measures to assess the effectiveness of treatment.     

Peripheral neuropathy associated with mitochondrial disease in children

Mitochondrial diseases in children are often associated with a peripheral neuropathy but the presence of the neuropathy is under-recognized because of the overwhelming involvement of the central nervous system (CNS). These mitochondrial neuropathies are heterogeneous in their clinical, neurophysiological, and histopathological characteristics. In this article, we provide a comprehensive review of childhood mitochondrial neuropathy. Early recognition of neuropathy may help with the identification of the mitochondrial syndrome. While it is not definite that the characteristics of the neuropathy would help in directing genetic testing without the requirement for invasive skin, muscle or liver biopsies, there appears to be some evidence for this hypothesis in Leigh syndrome, in which nuclear SURF1 mutations cause a demyelinating neuropathy and mitochondrial DNA MTATP6 mutations cause an axonal neuropathy. POLG1 mutations, especially when associated with late-onset phenotypes, appear to cause a predominantly sensory neuropathy with prominent ataxia. The identification of the peripheral neuropathy also helps to target genetic testing in the mitochondrial optic neuropathies. Although often subclinical, the peripheral neuropathy may occasionally be symptomatic and cause significant disability. Where it is symptomatic, recognition of the neuropathy will help the early institution of rehabilitative therapy. We therefore suggest that nerve conduction studies should be a part of the early evaluation of children with suspected mitochondrial disease.     

269例周围神经病的初步分析

目的分析周围神经病的临床特点。方法收集2010年1月至2015年12月住院的具有完整临床资料的周围神经病患者269例。对疾病诊断、病因、起病形式、首发症状进行回顾性分析,并对3例典型病例(舌下"神经鞘瘤"、嗜伊红肉芽肿伴多血管炎、多灶性运动神经病)资料进行报道。结果 269例周围神经病患者中,男女比例为1.58:1。单根周围神经损害152例(56.51%),最常见为面神经麻痹;末梢神经损害94例(34.94%)。糖尿病引起的周围神经损害84例(31.23%),运动神经元病21例(7.81%)。急性起病多见147例(54.65%)。大部分以肌力减退为首发症状169例(62.82%)。结论糖尿病引起的周围神经损害发病率最高。     

Autonomic and peripheral neuropathy in endstage liver disease and following liver transplantation

Severe chronic liver disease may be associated with a peripheral somatic and an autonomic neuropathy. There are only a limited number of reports on the incidence and features of these neuropathies. In addition the effects of liver transplantation on these neuropathies have not been well studied. We examined peripheral somatic and autonomic nerve function in 42 patients with endstage liver disease prior to transplantation and also examined the effect of liver transplantation on these neuropathies in 14 patients. Peripheral somatic neuropathy (93%) and autonomic neuropathy (50%) were common in patients with endstage liver disease and were more frequent than previously reported. Abnormalities improved in some patients after liver transplantation, particularly if there was return of normal hepatic function.     

Charcot–Marie–Tooth neuropathies: Current gene therapy advances and the route toward translation

Charcot–Marie–Tooth (CMT) neuropathies are a group of genetically and phenotypically heterogeneous disorders that predominantly affect the peripheral nervous system. Unraveling the genetic and molecular mechanisms, as well as the cellular effects of CMT mutations, has facilitated the development of promising gene therapy approaches. Proposed gene therapy treatments for CMTs include virally or non-virally mediated gene replacement, addition, silencing, modification, and editing of genetic material. For most CMT neuropathies, gene- and disease- and even mutation-specific therapy approaches targeting the neuronal axon or myelinating Schwann cells may be needed, due to the diversity of underlying cellular and molecular-genetic mechanisms. The efficiency of gene therapies to improve the disease phenotype has been tested mostly in vitro and in vivo rodent models that reproduce different molecular and pathological aspects of CMT neuropathies. In the next stage, bigger animal models, in particular non-human primates, provide important insights into the translatability of the proposed administration and dosing, demonstrating scale-up potential and safety. The path toward clinical trials is faced with further challenges but is becoming increasingly feasible owing to the progress and knowledge gained from clinical applications of gene therapies for other neurological disorders, as well as the emergence of sensitive outcome measures and biomarkers in patients with CMT neuropathies.     

Diabetic neuropathy: models, mechanisms and mayhem.

Rational treatment of diabetic polyneuropathy depends upon establishing its cause, which is at present unknown. A number of animal models of diabetes have been examined and although abnormalities are detectable in the peripheral nervous system they do not duplicate the degenerative neuropathy encountered in the human. The relevance of these abnormalities is therefore uncertain, although they may reflect the earlier changes in man. For human neuropathy, it is likely that vascular lesions or an abnormal susceptibility to mechanical injury are responsible for focal neuropathies. The evidence that ischaemia and hypoxia are responsible for the diffuse sensory neuropathy and autonomic polyneuropathy is still equivocal and it is often difficult to establish whether the vascular changes are primary or secondary. Metabolic explanations, such as sorbitol accumulation in nerve, have not so far been adequately validated by responses to treatment. The manifestations of diabetic neuropathy are complex and a single explanation should not be sought.     

Respiratory muscle weakness in peripheral neuropathies

Common peripheral neuropathies do not usually cause diaphragmatic weakness and subsequent respiratory compromise. However, respiratory involvement is relatively common in Guillain-Barré syndrome (GBS). Experience in GBS has led to a standardized approach to manage respiratory problems in peripheral neuropathies. Diaphragmatic weakness is not common in chronic inflammatory demyelinating polyneuropathy and extremely rare in multifocal motor neuropathy. The linkage has been described between certain subtypes of Charcot-Marie-Tooth (CMT) disease such as CMT2C and CMT4B1 and diaphragmatic weakness. A correlation usually has not been found between electrophysiologic findings and clinical respiratory signs or spirometric abnormalities in peripheral neuropathies except in amplitudes of evoked phrenic nerve responses. Careful and frequent assessment of respiratory function by a qualified team of healthcare professionals and physicians is essential. Criteria established for mechanical ventilation in GBS cases may be applied to other peripheral neuropathies with respiratory compromise as necessary.     

Clinical utility of peripheral nerve biopsy

Histopathologic evaluation of nerve biopsy specimens provides important diagnostic information in some patients with peripheral neuropathy. The role of nerve biopsy is more restricted than that of muscle biopsy. Nerve biopsy is utilized mainly for diagnosis of vasculitis and infiltrative neuropathies. It is also utilized in diagnosis of atypical inflammatory demyelinating neuropathies in which the clinical, electrodiagnostic, and laboratory features are inconclusive. In addition, the study of nerve histopathology can also enhance our understanding of disease pathogenesis.     

Animal models of immune-mediated neuropathies

PURPOSE OF REVIEW: This article gives an overview on animal models for immune-mediated demyelinating disorders of the peripheral nervous system. As insight into human disease is mainly based on biopsy material and ex-vivo analysis, an understanding of the pathogenetic mechanism of these complex and heterogeneous disorders is mainly based on animal models. RECENT FINDINGS: Besides experimental autoimmune neuritis in rats, recent efforts to establish this model in mice are discussed. In addition, models for spontaneous autoimmune neuropathies and secondary immune reactions in degenerative disorders of the peripheral nervous system are reviewed. SUMMARY: Recently described animal models offer the possibility to analyse the complex interaction of genetic and immunological factors. The entire panel of animal models for immune-mediated disorders of the peripheral nervous system provides a rational basis for studying the mechanisms of pathogenesis and new immunotherapeutic strategies for human autoimmune demyelinating neuropathies.     

Paraneoplastic peripheral neuropathies

Paraneoplastic peripheral neuropathies constitute a heterogeneous group of conditions. A link between the tumor and the neuropathy has been demonstrated in a subgroup only. Definite paraneoplastic neuropathies correspond to neuropathies associated with antibodies reacting with antigens common to the peripheral nervous system and the cancer. Neuropathies associated with anti-Hu antibodies are the most frequent and consist mainly in subacute sensory neuronopathy. Sensory or sensory-motor neuropathies with anti-CV2 antibodies are less frequent. The link between the cancer and the neuropathy is less clear in the other forms. The frequency of cancer in this group varies from 1 to 18 p.cent.These neuropathies include inflammatory demyelinating neuropathies, neuropathy and vasculitis, lower motor neurone diseases, and autonomic neuropathies. Occasionally, the neuropathy improves with treatment of the tumor. Recent data suggest that gangliosides may be the target of the immune process in neuropathies associated with melanoma.