Enhanced reinnervation after neurotization with Schwann cell transplantation

Porcine Acellular Nerve-Derived Hydrogel Improves Outcomes of Direct Muscle Neurotization in Rats

Background: The ability to reinnervate a muscle in the absence of a viable nerve stump is a challenging clinical scenario. Direct muscle neurotization (DMN) is an approach to overcome this obstacle; however, success depends on the formation of new muscle endplates, a process, which is often limited due to lack of appropriate axonal pathfinding cues. Objective: This study explored the use of a porcine nerve extracellular matrix hydrogel as a neuroinductive interface between nerve and muscle in a rat DMN model. The goal of the study was to establish whether such hydrogel can be used to improve neuromuscular function in this model. Materials and Methods: A common peroneal nerve-to-gastrocnemius model of DMN was developed. Animals were survived for 2 or 8 weeks following DMN with or without the addition of the hydrogel at the site of neurotization. Longitudinal postural thrust, terminal electrophysiology, and muscle weight assessments were performed to qualify and quantify neuromuscular function. Histological assessments were made to qualify the host response at the DMN site, and to quantify neuromuscular junctions (NMJs) and muscle fiber diameter. Results: The hydrogel-treated group showed a 132% increase in postural thrust at 8 weeks compared with that of the DMN alone group. This was accompanied by an 80% increase in the number of NMJs at 2 weeks, and 26% increase in mean muscle fiber diameter at 8 weeks. Conclusions: These results suggest that a nerve-derived hydrogel may improve the neuromuscular outcome following DNM.

Reinnervation of segmented latissimus dorsi muscle with the distal stump of the thoracodorsal nerve: A preliminary experimental study in rats

To date, nerve stumps have been dissected at the proximal side of the donor muscle for reinnervation of the muscle in free neurovascular muscle transfer. Herein, we examined the use of the distal thoracodorsal nerve, dissected from the muscle belly at the distal side of the latissimus dorsi muscle, for the reinnervation of muscle. The rat right latissimus dorsi muscle was employed as the model for our study. Twenty Wistar rats were used in this study. A rectangular muscle segment was dissected with the distal stump of dominant thoracodorsal nerve. After rotation of muscle, the distal nerve stump was sutured to a severed proximal recipient thoracodorsal nerve (n = 5). The degree of reinnervation through the distal nerve stump was compared with control groups that received proximal-to-proximal nerve sutures (n = 5), nerves that were not severed (n = 5), and severed nerves that were not sutured (n = 5) using electrophysiological, histological, and muscular volume assessments. Reinnervation of the distal nerve stump was confirmed by the contraction of the muscle following electrical stimulation and electromyography. Crossing of axons into motor endplates was confirmed by histology. Results of these assays were similar to that of the proximal nerve suture group. The volume of muscle in the distal nerve suture group was not significant different from that of the proximal nerve suture group (P = 0.63). It was demonstrated that the distal stump of the thoracodorsal nerve can be used to innervate segmented latissimus dorsi muscle. This novel procedure for the reinnervation of transplanted muscle deserves further investigations.

Autocrine motility factor injection for motor plate regeneration and muscle function restoration--a pilot study

BACKGROUND

Autocrine motility factor (AMF) is a multifunctional cytokine that promotes cellular adhesion, proliferation, motility, anti-apoptosis, and tissue repair. Direct nerve implantation (DNI) is considered to be effective in peripheral motor nerve injuries with disuse of the distal nerve; however, the repaired muscle function is not satisfactory. In our study, purified AMF was injected in reinnervated muscle after DNI with the intention of assessing if AMF, as a malignant tumor-related cytokine, could improve motor plate regeneration and neuromuscular function restoration.

METHODS

Purified AMF, which was extracted from AMF-transfected myoblast-conditioned medium, was regularly injected into the rat gastrocnemius in an established rat gastrocnemius denervation and reinnervation model. The nerve conduction velocity (NCV) of the tibial nerve, peak-to-peak value (PPV), area under the curve (AUC) of the compound muscle action potential (CMAP) and the Tibial Functional Index (TFI) were measured at 8, 16 and 24 weeks after injection. The regenerated endplates in gastrocnemius were examined by histochemical staining. In another group, an AMF-free solution was injected as the control.

RESULTS

After the AMF injection, the direct-nerve-implanted muscle function recovery was better in terms of both the nerve velocity and the quality. The endplates in the experimental group also had a quantitative advantage in restoration. After comparing the histochemical-stained tissues, no indications of tumorigenesis were detected.

CONCLUSIONS

AMF had positive effects on neuromuscular reparation and need more detailed research to determine the signalling pathways and side effects of AMF.

Construction of tissue engineered nerve grafts and their application in peripheral nerve regeneration

Surgical repair of severe peripheral nerve injuries represents not only a pressing medical need, but also a great clinical challenge. Autologous nerve grafting remains a golden standard for bridging an extended gap in transected nerves. The formidable limitations related to this approach, however, have evoked the development of tissue engineered nerve grafts as a promising alternative to autologous nerve grafts. A tissue engineered nerve graft is typically constructed through a combination of a neural scaffold and a variety of cellular and molecular components. The initial and basic structure of the neural scaffold that serves to provide mechanical guidance and optimal environment for nerve regeneration was a single hollow nerve guidance conduit. Later there have been several improvements to the basic structure, especially introduction of physical fillers into the lumen of a hollow nerve guidance conduit. Up to now, a diverse array of biomaterials, either of natural or of synthetic origin, together with well-defined fabrication techniques, has been employed to prepare neural scaffolds with different structures and properties. Meanwhile different types of support cells and/or growth factors have been incorporated into the neural scaffold, producing unique biochemical effects on nerve regeneration and function restoration. This review attempts to summarize different nerve grafts used for peripheral nerve repair, to highlight various basic components of tissue engineered nerve grafts in terms of their structures, features, and nerve regeneration-promoting actions, and finally to discuss current clinical applications and future perspectives of tissue engineered nerve grafts.

Neuronal regeneration in denervated muscle following sensory and muscular neurotization

BACKGROUND AND PURPOSE

Neurotization of denervated muscles has been shown to improve muscle bulk, but the neuronal regeneration response has not been compared previously in different surgical techniques of neurotization. Thus, using a rat model of experimental skeletal muscle denervation, we studied neuronal regeneration following sensory neurotization by two methods: sensory nerve to motor branch of muscle and direct sensory nerve implantation to muscle.

MATERIAL AND METHODS

The lateral head of the gastrocnemius muscle was denervated in 36 rats, of which the first 12 served as denervated controls. In the second group of 12, the sural nerve was anastomosed to the motor branch of the gastrocnemius muscle (sensory-to-motor nerve neurotization) and in the remaining 12 rats the sural nerve was split into 4 fascicles and embedded into 4 quadrants of the muscle (direct sensory nerve-to-muscle neurotization). Immunohistochemistry was used to examine nerve fibers in muscle containing the sensory neuropeptides substance P (SP) and calcitonin gene-related peptide (CGRP), and general neuronal marker protein gene product 9.5 (PGP 9.5).

RESULTS

Semiquantitative analysis showed that, compared to the control side, the number of nerve fibers on the experimental side was highest (p < 0.01) for group III (direct sensory nerve-to-muscle neurotization) for all 3 markers. The difference was 71%, 298%, and 254% for PGP 9.5, CGRP, and SP, respectively.

INTERPRETATION

This method may be a good option for inducing neuronal regeneration in denervated muscles, and has therapeutic implications for prevention of atrophy of denervated muscles and as an adjunct for reconstruction of soft tissue defects.