Regenerating axons emerge far proximal to the coaptation site in end-to-side nerve coaptation without a perineurial window using a T-shaped chamber.

BACKGROUND: Considerable controversy exists concerning the mechanism of axonal regeneration in end-to-side neurorrhaphy. The authors studied the mode of axonal regeneration in end-to-side neurorrhaphy without a perineurial window using a rat sciatic nerve model. METHODS: Twenty-seven rats were used. A 10-mm segment of peroneal nerve was harvested and coapted to the ipsilateral tibial nerve in end-to-side fashion using a T-shaped silicone chamber to minimize the tibial nerve damaged by surgery. To explain the role of nerve damage on axonal regeneration in end-to-side neurorrhaphy, we also used an isogenic nerve transplantation model in which the peroneal nerve remained intact. The mode of axonal regeneration was studied with electron microscopy, morphometric analysis, immunofluorescence, and immunohistochemistry. RESULTS: Both morphometric analysis and immunolabeling of neurofilaments demonstrated that regenerating axons emerge at sites far proximal to the coaptation site, travel within the tibial nerve, traverse the perineurium circumferentially around the coaptation site, and then invade into the peroneal nerve. Electron microscopy and a double-labeled immunofluorescence study with antibodies against neurofilament and tenascin-C confirmed large-scale axonal penetration into the perineurium around the coaptation site. Immunofluorescence with antibody against NG2, a marker of axonal regeneration, prevented the possibility of collateral sprouting at the coaptation site. In addition, an end-to-side neurorrhaphy model with an isogenic peroneal nerve clearly demonstrated that nerve damage is a prerequisite for axonal regeneration through end-to-side neurorrhaphy. CONCLUSIONS: The authors could not locate the site of axonal sprouting in end-to-side neurorrhaphy without a perineurial window; however, this study cast doubts on current hypothesis on the mode of axonal regeneration in end-to-side neurorrhaphy.

Enhancement of perineurial repair and inhibition of nerve adhesion by viscous injectable pure alginate sol.

BACKGROUND: Clinical treatment of recurrent symptoms following peripheral nerve decompression is problematic. Removal of scar tissue can produce an inappropriately pronounced healing response and thereby lead to more serious tethering or compression of the nerve. The goal of the present study was to test the ability of viscous injectable pure alginate sol to prevent perineurial adhesion using a rat neurolysis model. METHODS: The antiadhesive effect of viscous injectable pure alginate sol after neurolysis was evaluated histologically and biomechanically. A total of 40 rats were used in this study. The viscous injectable pure alginate sol was applied topically on the right side after external (six rats) or extensive internal (six rats) neurolysis, whereas the left side received no treatment. The nerves were harvested over 6 weeks, and histologic analysis was performed with hematoxylin and eosin staining and Masson trichrome staining. Functional analysis of the blood and perineurial barriers was also evaluated with Evans blue albumin (four rats). Sixteen rats were used for biomechanical analysis, and eight rats were used as a control group. The results were analyzed statistically using a post hoc test. RESULTS: Histologic examination showed that the use of viscous injectable pure alginate sol was associated with excellent biocompatibility and strong inhibition of perineurial granulation. Viscous injectable pure alginate sol was absorbed completely within 6 weeks without inducing inflammation. In addition, viscous injectable pure alginate sol enhanced repair of the perineurium associated with regeneration of epithelial-like cell layers, a key structure necessary for barrier function of the inner layer of the perineurium. Functional analysis with Evans blue albumin clearly demonstrated that, although blood nerve barrier function recovered by 6 weeks postoperatively in all nerves, the perineurial barrier function recovered only in the sol-treated nerves. Biomechanical study showed a significant antiadhesive effect of viscous injectable pure alginate sol. CONCLUSIONS: Viscous injectable pure alginate sol inhibited adhesion formation around nerves and enhanced regeneration of the perineurium with barrier function. Because excessive perineurial fibrosis and tethering at the neurolysis or neurorrhaphy site is a common postoperative problem in peripheral nerve surgery, viscous injectable pure alginate sol appears to have potentially broad clinical applications.

Effect of viscous injectable pure alginate sol on cultured fibroblasts.

BACKGROUND: Alginates have a wide variety of potential clinical applications, including use in cell encapsulation, drug delivery, and tissue engineering. Although the compounds are typically used in the form of a calcium hydrogel, alginates in this form possess several disadvantages, including low biodegradability, induction of foreign body reactions, and cytotoxicity secondary to Ca2+ efflux and contamination with bioincompatible substances. Thus, the goal of the present study was to develop a new method of obtaining sterilized, pure, highly viscous alginate sol from seaweed alginates and to determine its utility as an injectable antiadhesion drug. METHODS: Viscous injectable pure alginate sol was produced from a commercially available sodium alginate, and its molecular and physical characteristics were analyzed. The biological properties of the viscous injectable pure alginate sol were analyzed using cultured fibroblasts prepared from the dorsal skin of neonatal rats to determine its biocompatibility and its effects on cell proliferation, cell migration, and collagen lattice contraction. RESULTS: The mannuronic acid-to-glucuronic acid ratio of viscous injectable pure alginate sol, as determined by nuclear magnetic resonance studies, was 1.2, and its viscosity at 5 percent was 17,800 mPa. Purification used to produce viscous injectable pure alginate sol decreased contamination by insoluble particles by 20 percent and decreased polyphenol concentration by 17 percent. In vitro analyses with cultured fibroblasts demonstrated that viscous injectable pure alginate sol had excellent biodegradability and biocompatibility and that viscous injectable pure alginate sol inhibited fibroblast proliferation and migration. Furthermore, assessment of collagen contraction with floating fibroblast-loaded collagen lattices indicated that viscous injectable pure alginate sol enhanced wound healing in surrounding connective tissues. CONCLUSIONS: The authors conclude that viscous injectable pure alginate sol can inhibit scar formation by presenting a physical barrier to invading fibroblasts and by enhancing wound healing of surrounding tissues.

MMP-2 expression is associated with rapidly proliferative arteriosclerosis in the flexor tenosynovium and pain severity in carpal tunnel syndrome.

Due to the lack of correlation between symptom severity and electrophysiology or nerve function, the 'container hypothesis' has emerged as a new concept in carpal tunnel syndrome (CTS). This proposes that symptoms relate to connective tissue alteration rather than to nerve fibre pathology. This study was conducted to investigate the pathology of the flexor tenosynovium and its relationship with symptomatology. The subjects comprised 40 patients with electrophysiologically proven CTS who underwent open carpal tunnel release (age range: 31-79 years). In all patients, subjective symptom severity was assessed with a Likert scale and symptom duration was recorded preoperatively. Flexor tenosynovium biopsied during surgery was analysed for arterial and connective tissue alteration. Proliferative arteriosclerosis was graded using the modified Banff score. Gelatin zymography and immunohistochemistry were also performed to investigate the role of gelatinase in CTS. Relationships were evaluated using Spearman rank correlation coefficients. Proliferative arteriosclerosis occurred with disease progression in the flexor tenosynovium, in the absence of inflammation. This event did not correlate with patient age but correlated closely with symptom duration. Immunohistochemistry with antibodies against MMP-2 and elastic van Gieson staining revealed that arterioles express high levels of MMP-2 within 3 months of symptom onset and that intimal hyperplasia proceeded rapidly between 4 and 7 months, resulting in severe vascular narrowing. Gelatin zymography showed that MMP-2 activity correlated negatively with symptom duration and positively with pain severity.

Enhanced reinnervation after neurotization with Schwann cell transplantation.

We investigated the feasibility of using Schwann cell transplantation to enhance reinnervation after direct nerve-to-muscle neurotization (NMN). The denervated anterior tibial muscle was neurotized by tibial nerve implantation, and Schwann cell suspension (transplantation group) or an equivalent volume of culture medium (control group) was injected at the implantation site. In the control group, few axons invaded the muscle, demonstrating that skeletal muscle was poorly permissive to the advancement of axons. In the transplantation group, a large number of regenerating axons grew for a longer distance throughout the muscle, and reinnervated motor endplates were significantly more abundant. Enhanced reinnervation and functional recovery of the muscle in the transplantation group was confirmed by a significant increase in the compound muscle action potential and in muscle weight. These results suggest that intramuscular Schwann cell transplantation has potential as a cell therapy to improve functional recovery after NMN.

The relationship of VEGF and PGE2 expression to extracellular matrix remodelling of the tenosynovium in the carpal tunnel syndrome.

Tenosynovial thickening within the confined space of the carpal tunnel is thought to be the cause of the carpal tunnel syndrome (CTS). However, little is known about the pathological mechanism of tenosynovial thickening. In this study, the role of prostaglandin E(2) (PGE(2)) and vascular endothelial growth factor (VEGF) (two representative molecules that can induce oedema by increasing vascular permeability) was analysed in CTS by using immunohistochemistry and enzyme-linked immunosorptive assay (ELISA). Expression of these molecules was compared with the patients' clinical histories and a temporary increase in production of these molecules was found in cells within the vessels and synovial lining during the intermediate phase of the syndrome when the histology of the tenosynovium changes from oedematous to fibrotic. Statistical analysis clearly demonstrated that there is a close correlation between the expression of PGE(2) and VEGF. Furthermore, immunohistochemical analysis with anti-proliferating cell nuclear antigen (PCNA) revealed that the area with distinct VEGF expression closely matched the area where endothelial cells, vascular smooth muscle cells, and synovial lining cells proliferate. In contrast, despite marked alteration in the extracellular matrix (ECM) component of the tenosynovium, the fibroblasts responsible for most ECM framework production do not proliferate during any phase of CTS. Histological analysis demonstrated that angiogenesis takes place only during the intermediate phase. Since clusters of capillaries and arterioles are often surrounded by type III collagen-rich, disorganized, degenerate connective tissue, which contains fewer fibroblasts than normal, angiogenesis appears to take place as a part of a regenerative reaction that results in fibrosis. These findings strongly indicate that both PGE(2) and VEGF are expressed in the tenosynovium in CTS during the intermediate phase and induce the histological changes seen in the tenosynovium.

Irreducible volar subluxation of the metacarpophalangeal joint of the thumb.

An unusual case of irreducible volar metacarpophalangeal (MCP) joint subluxation of the thumb is described. The tendon of the extensor pollicis longus (EPL) was trapped palmar to the metacarpal head and open reduction was necessary.