Artificial nerve guidance conduits (NGCs) are synthetic nerve grafts that are capable of providing the structural and nutritional support for nerve regeneration. The ideal NGCs have plenty of requirements on biocompatibility, mechanical strength, topological structure, and conductivity. Therefore, it is necessary to continuously improve the design of NGCs and establish a better therapeutic strategy for peripheral nerve injury in order to meet clinical needs. Although current NGCs have made certain process in the treatment of peripheral nerve injury, their nerve regeneration and functional outcomes on repairing long-distance nerve injury remain unsatisfactory. Herein, we review the nerve conduit design from four aspects, namely raw material selection, structural design, therapeutic factor loading and self-powered component integration. Moreover, we summarize the research progress of NGCs in the treatment of peripheral nerve injury, in order to facilitate the iterative updating and clinical transformation of NGCs.
Humans ; Peripheral Nerve Injuries/therapy* ; Guided Tissue Regeneration ; Nerve Regeneration/physiology* ; Sciatic Nerve

The sensor of the taste is the taste bud. The signals originated from the taste buds are transmitted to the central nervous system through the gustatory taste nerves. The chorda tympani nerve (innervating the taste buds of the anterior tongue) and glossopharyngeal nerve (innervating the taste buds of the posterior tongue) are the two primary gustatory nerves. The injuries of gustatory nerves cause their innervating taste buds atrophy, degenerate and disappear. The related taste function is also impaired. The impaired taste function can be restored after the gustatory nerves regeneration. The rat model of cross-regeneration of gustatory nerves is an important platform for research in the plasticity of the central nervous system. The animal behavioral responses and the electrophysiological properties of the gustatory nerves have changed a lot after the cross-regeneration of the gustatory nerves. The effects of the injury, regeneration and cross-regeneration of the gustatory nerves on the taste function in the animals will be discussed in this review. The prospective studies on the animal model of cross-regeneration of gustatory nerves are also discussed in this review. The study on the injury, regeneration and cross-regeneration of the gustatory nerves not only benefits the understanding of mechanism for neural plasticity in gustatory nervous system, but also will provide theoretical basis and new ideas for seeking methods and techniques to cure dysgeusia.
Animals ; Chorda Tympani Nerve ; physiology ; Glossopharyngeal Nerve ; physiology ; Nerve Regeneration ; Neuronal Plasticity ; Rats ; Taste ; physiology ; Taste Buds ; physiology ; Tongue ; innervation

OBJECTIVETo explore the regeneration of mechanical sensory fibers after free nerve transplantation.

METHODNeuroelectrophysiological technique (single nerve fiber recording) was used to test the regeneration rate of mechanical sensory fibers, the proportion of rapidly and slowly adapting receptors, the stimulating thresholds of regenerated mechanoreceptors and conduction velocity of regenerated fibers. The regeneration pattern of the mechanoreceptors after free nerve transplantation to the rabbit reconstructed penis was also analyzed.

RESULTS9 months after operation, the number of regenerated mechanical sensory fiber was almost normal. The regenerated rapidly adapting receptors had a higher proportion with higher mature degree than the regenerated slowly adapting receptors. 9 months after nerve transplantation the stimulating thresholds of regenerated mechanoreceptors and conduction velocity of regenerated fibers remained below normal.

CONCLUSIONAfter free nerve transplantation to the rabbit reconstructed penis, the function of both rapidly and slowly adapting sensory nerve fiber partially recovered, but in different extent.

Animals ; Ganglia, Sensory ; physiology ; Male ; Mechanoreceptors ; physiology ; Nerve Fibers ; transplantation ; Nerve Regeneration ; Penis ; surgery ; Rabbits

Rats ; Animals ; Sciatic Neuropathy ; Muscle, Skeletal ; Sciatic Nerve/physiology* ; Sequence Analysis, RNA ; Nerve Regeneration/physiology*

The intrinsic regrowth ability of injured neurons is essential for axon regeneration and functional recovery. Recently, numerous intrinsic pathways that regulate axon regeneration have been discovered, among which the mitogen-activated protein kinase (MAPK) pathway and the phosphatidylinositol 3-kinase/protein kinase B (PI3K/Akt) pathway are arguably the best characterized examples. MAPK signaling pathway is involved in multiple processes including sensing injury signals, initiating and promoting axonal regrowth through regulating cytoskeleton dynamics and protein synthesis. The PI3K/Akt signaling pathway regulates axon regeneration mainly through gene transcription and translation. Combinatory manipulation of multiple regeneration-promoting signals can further improve the extend of axonal regrowth. This paper summarizes current progresses on axon regeneration studies in various organisms and discuss their potentials in promoting functional recovery .
Axons ; physiology ; Nerve Regeneration ; Neurons ; Phosphatidylinositol 3-Kinases ; Regeneration ; Signal Transduction

It has been well established that the recovery ability of central nervous system (CNS) is very poor in adult mammals. As a result, CNS trauma generally leads to severe and persistent functional deficits. Thus, the investigation in this field becomes a "hot spot". Up to date, accumulating evidence supports the hypothesis that the failure of CNS neurons to regenerate is not due to their intrinsic inability to grow new axons, but due to their growth state and due to lack of a permissive growth environment. Therefore, any successful approaches to facilitate the regeneration of injured CNS axons will likely include multiple steps: keeping neurons alive in a certain growth-state, preventing the formation of a glial scar, overcoming inhibitory molecules present in the myelin debris, and giving direction to the growing axons. This brief review focused on the recent progress in the neuron regeneration of CNS in adult mammals.
Animals ; Axons ; physiology ; Central Nervous System Diseases ; complications ; metabolism ; pathology ; Humans ; Mammals ; physiology ; Nerve Regeneration ; physiology

OBJECTIVETo study the effect of nerve growth factor (NGF) and Schwann cells on axon regeneration of the inferior alveolar nerve following mandibular lengthening with distraction osteogenesis.

METHODSUnilateral mandibular osteodistraction was performed in 9 healthy adult male goats with a distraction rate of 1 mm/d. Every 3 goats were killed on days 7, 14 and 28 after mandibular lengthening, respectively. The inferior alveolar nerves in the distraction callus were harvested and processed for ultrastructural and NGF immunohistochemical study. The inferior alveolar nerves from the contralateral side were used as controls.

RESULTSOn day 7 after distraction, axon degeneration and Schwann cell proliferation were observed, and very strong staining of NGF in the distracted nerve was detected. On day 14 after distraction, axon regeneration and remyelination were easily observed, and NGF expression started to decline. On day 28 after distraction, the gray scale of NGF immunoreactivity recovered to the normal value and the Schwann cells almost recovered to their normal state.

CONCLUSIONSGradual mandibular osteodistraction can result in mild or moderate axon degeneration of the inferior alveolar nerve. Nerve trauma may stimulate the proliferation of Schwann cells and promote the synthesis and secretion of NGF in the Schwann cells. Schwann cells and NGF might play important roles in axon regeneration of the injured inferior alveolar nerve following mandibular lengthening.

Animals ; Axons ; pathology ; physiology ; Goats ; Immunohistochemistry ; Male ; Mandible ; surgery ; Mandibular Nerve ; physiology ; Nerve Growth Factor ; physiology ; Nerve Regeneration ; physiology ; Osteogenesis, Distraction ; Schwann Cells ; physiology

OBJECTIVETo fabricate artificial nerves with tissue engineering methods in vitro.

METHODSSchwann cells (SCs) were cultured and seeded on polyglactin 910 fibers wrapped by biomembrane coated with rat tail glue and laminin for 2 weeks. The absorbability on the scaffolds, growth and migration of SCs were assessed with a light microscope, a scanning electron microscope and a transmission electron microscope.

RESULTSSCs could migrate and proliferate on polyglactin 910 fibers. They were well distributed between scaffolds and absorbed on surface of scaffolds and formed a bungner band, on which SCs produced more matrices. SCs seeded on the biomembrane could also grow well. Axon regeneration in the distal nerve stump was observed at 8 weeks.

CONCLUSIONSAdult SCs can be expanded on coated fibers and biomembrane. Three-dimensional scaffold of SCs has the basic characteristics of artificial nerves. These findings offer a novel method to fabricate artificial nerves with tissue engineering methods for repairing defected long nerves.

Animals ; Cells, Cultured ; Male ; Microscopy, Electron ; Nerve Regeneration ; physiology ; Rabbits ; Schwann Cells ; physiology ; Sciatic Nerve ; physiology ; Tissue Engineering ; methods

OBJECTIVETo evaluate the influence of mandibular distraction osteogenesis on inferior alveolar nerve function.

METHODS16 young Macaca rhesus monkeys were used as experiment animals. 5 days after mandibular osteotomy under general anesthesia, 10 male monkeys were distracted at right side and 6 females were bilaterally distracted at a rate of 0.5 mm x 2/day, for 15 days. The mandible was lengthened to an average of 13.5 mm. The Sensory Nerve Action Potential (SNAP) test was successfully applied in 16 monkeys before operation and at 0, 2, 4, 6, 9 and 12 weeks after distraction finished. Eight-channel EMG equipment was used for SNAP wave recording. The recordings were made with needle electrodes at foramen ovale and the stimulation was done at the mental foramen with two surface electrodes. The metal ground electrode was fixed on the right forearm. The stimulation intensities were five times of thresholds of each animal. The latency was measured at the first wave peak and the amplitude was measured between two wave peaks.

RESULTSJust after distraction finished, the latency period was 22.18% longer than before operation and gradually shortened as time lapsed. When distraction finished, the amplitude of SNAP wave was only 28.54% of that before operation, and after 12 weeks, it increased to the level of 99.84% of that before operation.

CONCLUSIONSThe mandibular distraction osteogenesis has temporary influence on the function of inferior alveolar nerve, but it is little and reversible, along with the regeneration of nerve sheath and axon, the nerve function can gradually return to normal level.

Action Potentials ; Animals ; Female ; Macaca mulatta ; Male ; Mandible ; surgery ; Mandibular Nerve ; physiology ; Nerve Regeneration ; Osteogenesis, Distraction

Animals ; Macaca mulatta ; Nerve Regeneration ; Peripheral Nerve Injuries ; physiopathology ; Peripheral Nerves ; physiology ; Rats