Autologous transplantation with fewer fibers repairs large peripheral nerve defects.

Peripheral nerve injury is a serious disease and its repair is challenging. A cable-style autologous graft is the gold standard for repairing long peripheral nerve defects; however, ensuring that the minimum number of transplanted nerve attains maximum therapeutic effect remains poorly understood. In this study, a rat model of common peroneal nerve defect was established by resecting a 10-mm long right common peroneal nerve. Rats receiving transplantation of the common peroneal nerve in situ were designated as the in situ graft group. Ipsilateral sural nerves (10-30 mm long) were resected to establish the one sural nerve graft group, two sural nerves cable-style nerve graft group and three sural nerves cable-style nerve graft group. Each bundle of the peroneal nerve was 10 mm long. To reduce the barrier effect due to invasion by surrounding tissue and connective-tissue overgrowth between neural stumps, small gap sleeve suture was used in both proximal and distal terminals to allow repair of the injured common peroneal nerve. At three months postoperatively, recovery of nerve function and morphology was observed using osmium tetroxide staining and functional detection. The results showed that the number of regenerated nerve fibers, common peroneal nerve function index, motor nerve conduction velocity, recovery of myodynamia, and wet weight ratios of tibialis anterior muscle were not significantly different among the one sural nerve graft group, two sural nerves cable-style nerve graft group, and three sural nerves cable-style nerve graft group. These data suggest that the repair effect achieved using one sural nerve graft with a lower number of nerve fibers is the same as that achieved using the two sural nerves cable-style nerve graft and three sural nerves cable-style nerve graft. This indicates that according to the 'multiple amplification' phenomenon, one small nerve graft can provide a good therapeutic effect for a large peripheral nerve defect.

Morphological study on the collaterals developed by one axon during peripheral nerve regeneration.

Outgrowth of collateral sprouts from axons is a natural process that arises during development of and regeneration in the peripheral nervous system. Our previous study showed that if there are enough distal endoneurial tubes into which the proximal regenerative axons can grow, one axon can support three to four collaterals, at most. Here, the proximal half tibial nerve was fixed to the distal stump and served as the donor nerve. The number of myelinated axons was calculated after 4 months. The ratio of distal regenerative myelinated axon number to proximal donor nerve axon number was 1.83 with the tibial function index and the nerve conduction velocities of - 48.6 ± 6.8 and 27.8 ± 5.3 m/s. The regenerated collaterals were isolated and observed to sprout from the node of Ranvier with almost the same features of normal fibers, but with different electrophysiological characteristics. This finding shows the evidence of one-axon trunk several-collateral model in peripheral nerve regeneration and suggests that such multi-collateral regeneration model may be useful in peripheral nerve reconstruction.

Can "dor to dor+rec neurorrhaphy" by biodegradable chitin conduit be a new method for peripheral nerve injury?

This study aims to estimate the effects of using one donor nerve to repair the injured nerve and itself simultaneously by biodegradable chitin conduit. Proximal median nerve served as donor nerve to repair the distal median and whole ulnar nerve. Four months postoperation, the number of myelinated axons and nerve conduction velocities of the distal median and ulnar nerve were (2085 ± 215 and 24.4 ± 5.9 m/s), and (1193 ± 102 and 30.7 ± 11.2 m/s). Recovery of the tetanic muscle forces of the reinvervated muscles were also observed. It suggests that Dor to Dor+Rec neurorrhaphy is a practical method for severe peripheral nerve injury.

Maximum number of collaterals developed by one axon during peripheral nerve regeneration and the influence of that number on reinnervation effects.

This study investigated the maximum number of collaterals that can be maintained by 1 axon during regeneration of rat peripheral nerve. The tibial nerve was transected, the proximal residual, with its variable number of axons, was fixed to the distal stump and served as the donor nerve. The number of myelinated axons was calculated after 12 weeks. An increasing ratio of distal stump axon numbers to proximal donor nerve axon numbers of 1.0, 1.83, 3.64 and 7.97 yielded ratios of regenerative myelinated axon numbers to proximal donor axon numbers of 0.98, 1.51, 2.39, 2.89, respectively, with an estimated maximum value of approximately 3.3 using the Hill function. The tibial function indexes and nerve conduction velocities of the regenerated tibial nerve were -44.1 +/- 5.1 and 43.2 +/- 5.3 m/s, -57.5 +/- 4.7 and 18.6 +/- 4.3 m/s, -80.2 +/- 7.1 and 12.7 +/- 3.7 m/s, and -85.4 +/- 5.7 and 10.5 +/- 3.9 m/s, respectively. It has been suggested that 1 axon can regenerate and maintain up to 3 or 4 collaterals in regenerated rat peripheral nerve.

Alterations in the expression of ATP-sensitive potassium channel subunit mRNA after acute peripheral nerve and spinal cord injury.

ATP-sensitive potassium channels (K(ATP)) are involved in the regulation of potassium homeostasis in the nervous system, and they may play an important role in acute peripheral nerve and spinal cord injury. Here, the expression of the K(ATP) genes was monitored by reverse transcription polymerase chain reaction (RT-PCR) in the rat dorsal root ganglion, spinal cord and cerebral cortex following acute sciatic nerve and spinal cord injury. Electrophoresis of the RT-PCR products showed that in comparison with the normal rats, the K(ATP) mRNA expression level was up-regulated for the Kir6.2 subunit in the rat dorsal root ganglion 4 and 24 h after the acute sciatic nerve injury (142.7 +/- 23.0 and 135.5 +/- 21.0%, p < 0.05, vs. control, n = 3), and both Kir6.1 and sulphonylurea receptor 2 mRNA were increased in the spinal cord during the same time period after the acute spinal cord injury (266.5 +/- 67.1 and 248.7 +/- 67.7%; 145.1 +/- 42.6 and 152.6 +/- 44.3%, p < 0.05, vs. control, n = 3). No significant changes of K(ATP) genes were observed in the cerebral cortex among both sciatic-nerve- and spinal-cord-injured animals. These results suggest that acute peripheral nerve and spinal cord injury provoke different regulations of K(ATP) gene expression in the peripheral and central nervous system.