Perineurium talin immunoreactivity decreases in diabetic neuropathy

Structural Nerve Remodeling at 3-T MR Neurography Differs between Painful and Painless Diabetic Polyneuropathy in Type 1 or 2 Diabetes

Background The pathophysiologic mechanisms underlying painful symptoms in diabetic polyneuropathy (DPN) are poorly understood. They may be associated with MRI characteristics, which have not yet been investigated. Purpose To investigate correlations between nerve structure, load and spatial distribution of nerve lesions, and pain in patients with DPN. Materials and Methods In this prospective single-center cross-sectional study, participants with type 1 or 2 diabetes volunteered between June 2015 and March 2018. Participants underwent 3-T MR neurography of the sciatic nerve with a T2-weighed fat-suppressed sequence, which was preceded by clinical and electrophysiologic tests. For group comparisons, analysis of variance or the Kruskal-Wallis test was performed depending on Gaussian or non-Gaussian distribution of data. Spearman correlation coefficients were calculated for correlation analysis. Results A total of 131 participants (mean age, 62 years ± 11 [standard deviation]; 82 men) with either type 1 (n = 45) or type 2 (n = 86) diabetes were evaluated with painful (n = 64), painless (n = 37), or no (n = 30) DPN. Participants who had painful diabetic neuropathy had a higher percentage of nerve lesions in the full nerve volume (15.2% ± 1.6) than did participants with nonpainful DPN (10.4% ± 1.7, P = .03) or no DPN (8.3% ± 1.7; P < .001). The amount and extension of T2-weighted hyperintense nerve lesions correlated positively with the neuropathy disability score (r = 0.37; 95% confidence interval [CI]: 0.21, 0.52; r = 0.37; 95% CI: 0.20, 0.52, respectively) and the neuropathy symptom score (r = 0.41; 95% CI: 0.25, 0.55; r = 0.34; 95% CI: 0.17, 0.49, respectively). Negative correlations were found for the tibial nerve conduction velocity (r = -0.23; 95% CI: -0.44, -0.01; r = -0.37; 95% CI: -0.55, -0.15, respectively). The cross-sectional area of the nerve was positively correlated with the neuropathy disability score (r = 0.23; 95% CI: 0.03, 0.36). Negative correlations were found for the tibial nerve conduction velocity (r = -0.24; 95% CI: -0.45, -0.01). Conclusion The amount and extension of T2-weighted hyperintense fascicular nerve lesions were greater in patients with painful diabetic neuropathy than in those with painless diabetic neuropathy. These results suggest that proximal fascicular damage is associated with the evolution of painful sensory symptoms in diabetic polyneuropathy. © RSNA, 2019 Online supplemental material is available for this article.

Disruption of peripheral nerve development in a zebrafish model of hyperglycemia

Diabetes mellitus-induced hyperglycemia is associated with a number of pathologies such as retinopathy, nephropathy, delayed wound healing, and diabetic peripheral neuropathy (DPN). Approximately 50% of patients with diabetes mellitus will develop DPN, which is characterized by disrupted sensory and/or motor functioning, with treatment limited to pain management. Zebrafish ( Danio rerio) are an emerging animal model used to study a number of metabolic disorders, including diabetes. Diabetic retinopathy, nephropathy, and delayed wound healing have all been demonstrated in zebrafish. Recently, our laboratory has demonstrated that following the ablation of the insulin-producing β-cells of the pancreas (and subsequent hyperglycemia), the peripheral nerves begin to show signs of dysregulation. In this study, we take a different approach, taking advantage of the transdermal absorption abilities of zebrafish larvae to extend the period of hyperglycemia. Following 5 days of 60 mM d-glucose treatment, we observed motor axon defasciculation, disturbances in perineurial glia sheath formation, decreased myelination of motor axons, and sensory neuron mislocalization. This study extends our understanding of the structural changes of the peripheral nerve following induction of hyperglycemia and does so in an animal model capable of potential DPN drug discovery in the future.

NEW & NOTEWORTHY Zebrafish are emerging as a robust model system for the study of diabetic complications such as retinopathy, nephropathy, and impaired wound healing. We present a novel model of diabetic peripheral neuropathy in zebrafish in which the integrity of the peripheral nerve is dysregulated following the induction of hyperglycemia. By using this model, future studies can focus on elucidating the underlying molecular mechanisms currently unknown.

Dystrophin Dp116: A yet to Be Investigated Product of the Duchenne Muscular Dystrophy Gene

The Duchenne muscular dystrophy (DMD) gene is one of the largest genes in the human genome. The gene exhibits a complex arrangement of seven alternative promoters, which drive the expression of three full length and four shorter isoforms. Dp116, the second smallest product of the DMD gene, is a Schwann cell-specific isoform encoded by a transcript corresponding to DMD exons 56–79, starting from a promoter/exon S1 within intron 55. The physiological roles of Dp116 are poorly understood, because of its extensive homology with other isoforms and its expression in specific tissues. This review summarizes studies on Dp116, focusing on clinical findings and alternative activation of the upstream translation initiation codon that is predicted to produce Dp118.

The normal and neoplastic perineurium: a review

Peripheral nerves consist of 3 layers with differing characteristics: the endoneurium, perineurium, and epineurium. The perineurium represents a continuum with the pia-arachnoid from the central nervous system and extends distally with the sheath of capsular cells of peripheral sensorial organs and propioceptive receptors. It is made of layers of flattened cells surrounded by a basement membrane and collagen fibers, forming concentrically laminated structures around single nerve fascicles. Functionally, the perineurium modulates external stretching forces (that could be potentially harmful for nerve fibers), and along with endoneurial vessels, forms the blood-nerve barrier. Multiple pathologic conditions associated with the perineurium have been described. Perineurial invasion is considered an important prognostic factor in several malignant neoplasms. Perineuriomas are true benign infrequent perineurial cell neoplasms that have been divided in 2 categories: those with intraneural localization and a more common extraneural (soft tissue) group, including sclerosing and reticular variants. Sporadic cases of malignant perineuromas have been reported. Interestingly, neurofibromas and malignant peripheral nerve sheath tumors may also display perineurial cell differentiation. The histologic appearance of perineuriomas may overlap with other soft tissue spindle cell neoplasms. Immunohistochemistry is imperative for the diagnosis, although in certain cases ultrastructural studies may be needed. Typical perineuriomas are positive for epithelial membrane antigen, glucose transporter-1-1, and claudin-1, and negative for S-100 protein and neurofilaments. Perineuriomas have mostly simple karyotypes, with one or few chromosomal rearrangements or numerical changes and it seems that specific cytogenetic aberrations may correlate with perineurioma subtype.