Histological Compatibility in Distal Neurotizations: A Systematic Review

AUTHORS

Cristina Schmitt Cavalheiro, João Carlos Nakamoto, Teng Hsiang Wei, Luiz Sorrenti, Erick Yoshio Wataya

ABSTRACT

Considering the importance of defining the minimum number of axons between recipient and donor branches, that is, the definition of histological compatibility in distal neurotizations for the success of the procedure and the surgeon's freedom to choose individualized strategies for each patient, this systematic review was conducted to find out the most recent studies on the subject. The objective of this systematic review was to determine the importance of the number of axons and the relationship between axon counts in the donor and recipient nerves in the success of nerve transfer. A literature review was performed on five international databases: Web of Science, Scopus, Wiley (Cochrane Database), Embase, and PubMed. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were followed (2020 version), a guide designed to guide the elaboration of systematic literature reviews. One hundred and fifty-seven studies were found, and 23 were selected based on the eligibility criteria. The articles presented were conclusive in determining the importance of the number of axons in the success of nerve transfer. Still, the relationship between the number of axons in the donor and recipient nerves seems more relevant in the success of transfers and is not always explored by the authors. The review of the articles has provided compelling evidence that the number of axons is a critical determinant of the success of nerve transfer procedures. However, the relationship between the number of axons in the donor nerve and that in the recipient nerve appears to be even more crucial for successful transfers, a factor that is not always adequately explored by authors in the existing literature.

Evaluation of the neuroprotective effects of methylprednisolone and surgical decompression in a rodent model of traumatic optic neuropathy

AUTHORS

Philippe Korn, Nils-Claudius Gellrich, Simon Spalthoff, Philipp Jehn, Ulf T. Eysel & Martin Zerfowski

ABSTRACT

Purpose of the study

Traumatic optic neuropathy (TON) is a rare but serious consequence of head injuries. The optimal therapy for TON remains controversial, and standardized recommendations are lacking. The most common therapies used are steroid administration and surgical decompression procedures. The aim of the present study was to compare two common conservative and surgical therapies in a rodent model with a standardized traumatic optic nerve lesion.

Materials and Methods

This study employed 59 male Wistar rats. After exposing the optic nerve, defined trauma was exerted on the optic nerve using a micromanipulator to trigger TON. Rats received either “megadose” methylprednisolone applied perioperatively or decompression via nerve sheath fenestration. The number of neurons was histologically evaluated in retinae explanted as whole mounts. Neuronal size was determined histomorphometrically.

Results

Neuronal loss was significantly lower following perioperative “megadose” steroid therapy (p = 0.017), especially in the central retinal area (p = 0.025). Compared to the control group without therapy, on average more than 400 neurons/mm2 were saved. In the central retinal area, more than 600 neurons/mm2 were rescued. In contrast, neuronal loss was not significantly affected by surgical decompression; however, this procedure was associated with a reduction in neuron size (p = 0.003).

Conclusions

The present model revealed significant neuroprotective effects following administration of methylprednisolone for TON treatment. Mitigation of neuronal loss may result in functional benefits. Neuroprotective effects were not observed following surgical therapy, suggesting that this approach should be reserved for individual cases such as hematomas in the area of nerve envelopes.

AAV1.NT-3 gene therapy in a CMT2D model: phenotypic improvements in GarsP278KY/+ mice

AUTHORS

Burcak Ozes, Kyle Moss, Morgan Myers, Alicia Ridgley, Lei Chen, Darren Murrey, Zarife Sahenk

ABSTRACT

Glycyl–tRNA synthetase mutations are associated to the Charcot–Marie–Tooth disease type-2D. The GarsP278KY/+ model for Charcot–Marie–Tooth disease type-2D is known best for its early onset severe neuropathic phenotype with findings including reduced axon size, slow conduction velocities and abnormal neuromuscular junction. Muscle involvement remains largely unexamined. We tested the efficacy of neurotrophin 3 gene transfer therapy in two Gars mutants with severe (GarsP278KY/+) and milder (GarsΔETAQ/+) phenotypes via intramuscular injection of adeno-associated virus setoype-1, triple tandem muscle creatine kinase promoter, neurotrophin 3 (AAV1.tMCK.NT-3) at 1 × 1011 vg dose. In the GarsP278KY/+ mice, the treatment efficacy was assessed at 12 weeks post-injection using rotarod test, electrophysiology and detailed quantitative histopathological studies of the peripheral nervous system including neuromuscular junction and muscle. Neurotrophin 3 gene transfer therapy in GarsP278KY/+ mice resulted in significant functional and electrophysiological improvements, supported with increases in myelin thickness and improvements in the denervated status of neuromuscular junctions as well as increases in muscle fibre size along with attenuation of myopathic changes. Improvements in the milder phenotype GarsΔETAQ/+ was less pronounced. Furthermore, oxidative enzyme histochemistry in muscles from Gars mutants revealed alterations in the content and distribution of oxidative enzymes with increased expression levels of Pgc1a. Cox1, Cox3 and Atp5d transcripts were significantly decreased suggesting that the muscle phenotype might be related to mitochondrial dysfunction. Neurotrophin 3 gene therapy attenuated these abnormalities in the muscle. This study shows that neurotrophin 3 gene transfer therapy has disease modifying effect in a mouse model for Charcot–Marie–Tooth disease type-2D, leading to meaningful improvements in peripheral nerve myelination and neuromuscular junction integrity as well as in a unique myopathic process, associated with mitochondria dysfunction, all in combination contributing to functional outcome. Based on the multiple biological effects of this versatile molecule, we predict neurotrophin 3 has the potential to be beneficial in other aminoacyl-tRNA synthetase-linked Charcot–Marie–Tooth disease subtypes.

Effects of Theranekron and alpha-lipoic acid combined treatment on GAP-43 and Krox-20 gene expressions and inflammation markers in peripheral nerve injury

AUTHORS

Leman Sencar, Gülfidan Coşkun, Dilek Şaker, Tuğçe Sapmaz, Samet Kara, Alper Çelenk, Sema Polat, Derviş Mansuri Yılmaz, Y. Kenan Dağlıoğlu & Sait Polat

ABSTRACT

Peripheral nerve injury (PNI) is a major health problem that results in loss of motor and sensory functions. In treatment of PNI, various methods such as anastomosis, nerve grafts, nonneural tissue grafts, and nerve conduits are applied. In the present study, it was aimed to investigate the effects of Theranekron and Alpha-lipoic acid (ALA) combined treatment on nerve healing in experimental PNI by using histomorphometric, electron microscopic, immunohistochemical and molecular biological methods. Sixty-two Wistar rats were divided into six groups; the normal control group, sham operation group, experimental control group having a crush type injury with no treatment, Theranekron treatment group, ALA treatment group and Theranekron+ALA combined treatment group. Sciatic nerve tissue samples were obtained on days 1, 7 and 14 following injury in all groups. GAP-43 expression was upregulated in all PNI received groups compared to the control group. Krox-20 expression was downregulated in all groups that received PNI compared to the control group. While intensely positive TNF-α and IL-6 expressions were observed up to the 1st to the 14th day for the experimental control group, these expressions were seen as “weakly positive” in the treatment groups from the 1st day to the 14th day. The number of myelinated fibers was higher in the control and sham operation groups. Additionally, the number of myelinated nerve fibers increased in the combined treatment group. In conclusion, these findings suggest that combined therapy of Theranekron and ALA promotes structural recovery and it should be considered as an effective treatment protocol following PNI.

Nerve transfer for restoration of lower motor neuron-lesioned bladder function. Part 2: correlation between histological changes and nerve evoked contractions

AUTHORS

Mary F. Barbe, Courtney L. Testa, Geneva E. Cruz, Nagat A. Frara, Ekta Tiwari, Lucas J. Hobson, Brian S. McIntyre, Danielle S. Porreca, Dania Giaddui, Alan S. Braverman, Emily P. Day, Mamta Amin, Justin M. Brown, Michael Mazzei, Michel A. Pontari, Ida J. Wagner, and Michael R. Ruggieri Sr.

ABSTRACT

We determined the effect of pelvic organ decentralization and reinnervation 1 yr later on urinary bladder histology and function. Nineteen canines underwent decentralization by bilateral transection of all coccygeal and sacral (S) spinal roots, dorsal roots of lumbar (L)7, and hypogastric nerves. After exclusions, eight were reinnervated 12 mo postdecentralization with obturator-to-pelvic and sciatic-to-pudendal nerve transfers, then euthanized 8-12 mo later. Four served as long-term decentralized only animals. Before euthanasia, pelvic or transferred nerves and L1–S3 spinal roots were stimulated and maximum detrusor pressure (MDP) recorded. Bladder specimens were collected for histological and ex vivo smooth muscle contractility studies. Both reinnervated and decentralized animals showed less or denuded urothelium, fewer intramural ganglia, and more inflammation and collagen, than controls, although percent muscle was maintained. In reinnervated animals, pgp9.5+ axon density was higher compared with decentralized animals. Ex vivo smooth muscle contractions in response to KCl correlated positively with submucosal inflammation, detrusor muscle thickness, and pgp9.5+ axon density. In vivo, reinnervated animals showed higher MDP after stimulation of L1–L6 roots compared with their transected L7–S3 roots, and reinnervated and decentralized animals showed lower MDP than controls after stimulation of nerves (due likely to fibrotic nerve encapsulation). MDP correlated negatively with detrusor collagen and inflammation, and positively with pgp9.5+ axon density and intramural ganglia numbers. These results demonstrate that bladder function can be improved by transfer of obturator nerves to pelvic nerves at 1 yr after decentralization, although the fibrosis and inflammation that developed were associated with decreased contractile function.

AAV1.NT-3 gene therapy for X-linked Charcot–Marie–Tooth neuropathy type 1

AUTHORS

Burcak Ozes, Morgan Myers, Kyle Moss, Jennifer Mckinney, Alicia Ridgley, Lei Chen, Shasha Bai, Charles K. Abrams, Mona M. Freidin, Jerry R. Mendell & Zarife Sahenk

ABSTRACT

X-linked Charcot-Marie-Tooth neuropathy (CMTX) is caused by mutations in the gene encoding Gap Junction Protein Beta-1 (GJB1)/Connexin32 (Cx32) in Schwann cells. Neurotrophin-3 (NT-3) is an important autocrine factor supporting Schwann cell survival and differentiation and stimulating axon regeneration and myelination. Improvements in these parameters have been shown previously in a CMT1 model, TremblerJ mouse, with NT-3 gene transfer therapy. For this study, scAAV1.tMCK.NT-3 was delivered to the gastrocnemius muscle of 3-month-old Cx32 knockout (KO) mice. Measurable levels of NT-3 were found in the serum at 6-month post gene delivery. The outcome measures included functional, electrophysiological and histological assessments. At 9-months of age, NT-3 treated mice showed no functional decline with normalized compound muscle action potential amplitudes. Myelin thickness and nerve conduction velocity significantly improved compared with untreated cohort. A normalization toward age-matched wildtype histopathological parameters included increased number of Schmidt-Lanterman incisures, and muscle fiber diameter. Collectively, these findings suggest a translational application to CMTX1.