Nerve expansion in nerve regeneration: effect of time on induction of ornithine decarboxylase and Schwann cell proliferation

Acute Putrescine Supplementation with Schwann Cell Implantation Improves Sensory and Serotonergic Axon Growth and Functional Recovery in Spinal Cord Injured Rats

Schwann cell (SC) transplantation exhibits significant potential for spinal cord injury (SCI) repair and its use as a therapeutic modality has now progressed to clinical trials for subacute and chronic human SCI. Although SC implants provide a receptive environment for axonal regrowth and support functional recovery in a number of experimental SCI models, axonal regeneration is largely limited to local systems and the behavioral improvements are modest without additional combinatory approaches. In the current study we investigated whether the concurrent delivery of the polyamine putrescine, started either 30 min or 1 week after SCI, could enhance the efficacy of SCs when implanted subacutely (1 week after injury) into the contused rat spinal cord. Polyamines are ubiquitous organic cations that play an important role in the regulation of the cell cycle, cell division, cytoskeletal organization, and cell differentiation. We show that the combination of putrescine with SCs provides a significant increase in implant size, an enhancement in axonal (sensory and serotonergic) sparing and/or growth, and improved open field locomotion after SCI, as compared to SC implantation alone. These findings demonstrate that polyamine supplementation can augment the effectiveness of SCs when used as a therapeutic approach for subacute SCI repair.

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.

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.

Repair of nerve gap with the elongation of Wallerian degenerated nerve by tissue expansion

We have found previously that expansion of the Wallerian degenerated nerve was accompanied by accelerated Schwann cell proliferation. In this study, we investigated the usefulness of the elongation of Wallerian degenerated nerve for the repair of short nerve gap. Male Wistar rats were used. After the left sciatic nerve was transected the rats were divided into 4 groups. In the control group, nerve coaptation was not performed. In group 1, tensionless coaptation was performed immediately. In group 2, delayed tensionless coaptation was performed with the elongation of Wallerian degenerated nerve. In group 3, coaptation was performed immediately with autologous interposition nerve graft. The ideal tensionless nerve repair of group 1 was considered to produce the best result. Rats in group 2 showed functional recovery as good as rats in group 1. On histologic assessment, in group 2, a fibrous capsule that was very rich in vascularity was formed around the tissue expander. After 14 weeks, the capsule was diminished markedly in size, but the vascularity was rich around the sciatic nerve. We think that the excellent functional recovery seen in group 2 can be attributed to the increased activity of Schwann cell proliferation and increased vascularity.