Puerarin accelerates neural regeneration after sciatic nerve injury

Puerarin is a natural isoflavone isolated from plants of the genus Pueraria and functions as a protector against cerebral ischemia. We hypothesized that puerarin can be involved in the repair of peripheral nerve injuries. To test this hypothesis, doses of 10, 5, or 2.5 mg/kg per day puerarin(8-(β-D-Glucopyranosyl-7-hydroxy-3-(4-hydroxyphenyl)-4H-1-benzopyran-4-one) were injected intraperitoneally into mouse models of sciatic nerve injury. Puerarin at the middle and high doses significantly up-regulated the expression of growth-associated protein 43 in the L4–6 segments of the spinal cord from mice at 1, 2, and 4 weeks after modeling, and reduced the atrophy of the triceps surae on the affected side and promoted the regeneration of nerve fibers of the damaged spinal cord at 8 weeks after injury. We conclude that puerarin exerts an ongoing role to activate growth-associated protein 43 in the corresponding segment of the spinal cord after sciatic nerve injury, thus contributing to neural regeneration after sciatic nerve injuries.     

Axonal autophagy during regeneration of the rat sciatic nerve**★

BACKGROUND: The removal of degenerated axonal debris during Wallerian degeneration is very important for nerve regeneration. However, the mechanism by which debris is removed is not been completely understood. Considerable controversy remains as to the clearance pathway and cells that are involved. OBJECTIVE: To investigate axonal autophagy during removal of degenerated axonal debris by transecting the sciatic nerve in a rat Wallerian degeneration model.DESIGN, TIME AND SETTING: Experimental neuropathological analysis. The experiment was conducted at the Laboratory Animal Service Center of the Southern Medical University between January and June 2005. MATERIALS: Fifty-four adult, Wistar rats of either sex, weighing 180-250 g, were obtained from the Laboratory Animal Service Center of the Southern Medical University. Animals were randomly divided into nine groups of six rats. METHODS: Wallerian degeneration was induced by transecting the rat sciatic nerve, and tissue samples from the distal stump were obtained 0.2, 0.4, 1, 2, 3, 4, 7, 10, and 15 days post-transection. Ultrathin sections were prepared for electron microscopy to study ultrastructure and enzyme cytochemistry staining. MAIN OUTCOME MEASURES: Ultrastructure (axon body, autophagic body, and cystoskeleton) of axons and myelin sheaths observed with electron microscopy; acidic phosphatase activity detected by Gomori staining using electron microscopy. RESULTS: The major changes of degenerating axons after transection were axoplasm swelling and separation of axons from their myelin sheath between five hours and two days post-transection. At four days post-transection, the axoplasm condensed and axons were completely separated from the myelin sheath, forming dissociative axon bodies. Vacuoles of different sizes formed in axons during the early phase after lesion. Larger dissociative axon bodies were formed when the axons were completely separated from the myelin sheath during a late phase. The axolemma surrounding the axon body was derived from the neuronal cell membrane; the condensed axoplasm contained many autophagic vacuoles at all levels. A large number of neurofilaments, microtubules, and microfilaments were arranged in a criss-cross pattern. The autophagic vacuoles exhibited acidic phosphatase activity. Axonal bodies were absorbed after degradation from day 7 onwards, and macrophages were observed rarely in the formative cavity. CONCLUSION: The degenerating axons were cleared mainly by axonal autophagy and Schwann cell phagocytosis during regeneration of the rat sciatic nerve, and macrophages exhibited only an assisting function.     

Axonal autophagy during regeneration of the rat sciatic nerve**★

BACKGROUND: The removal of degenerated axonal debris during Wallerian degeneration is very important for nerve regeneration. However, the mechanism by which debris is removed is not been completely understood. Considerable controversy remains as to the clearance pathway and cells that are involved. OBJECTIVE: To investigate axonal autophagy during removal of degenerated axonal debris by transecting the sciatic nerve in a rat Wallerian degeneration model. DESIGN, TIME AND SETTING: Experimental neuropathological analysis. The experiment was conducted at the Laboratory Animal Service Center of the Southern Medical University between January and June 2005. MATERIALS: Fifty-four adult, Wistar rats of either sex, weighing 180-250 g, were obtained from the Laboratory Animal Service Center of the Southern Medical University. Animals were randomly divided into nine groups of six rats. METHODS: Wallerian degeneration was induced by transecting the rat sciatic nerve, and tissue samples from the distal stump were obtained 0.2, 0.4, 1, 2, 3, 4, 7, 10, and 15 days post-transection. Ultrathin sections were prepared for electron microscopy to study ultrastructure and enzyme cytochemistry staining. MAIN OUTCOME MEASURES: Ultrastructure (axon body, autophagic body, and cystoskeleton) of axons and myelin sheaths observed with electron microscopy; acidic phosphatase activity detected by Gomori staining using electron microscopy. RESULTS: The major changes of degenerating axons after transection were axoplasm swelling and separation of axons from their myelin sheath between five hours and two days post-transection. At four days post-transection, the axoplasm condensed and axons were completely separated from the myelin sheath, forming dissociative axon bodies. Vacuoles of different sizes formed in axons during the early phase after lesion. Larger dissociative axon bodies were formed when the axons were completely separated from the myelin sheath during a late phase. The axolemma surrounding the axon body was derived from the neuronal cell membrane; the condensed axoplasm contained many autophagic vacuoles at all levels. A large number of neurofilaments, microtubules, and microfilaments were arranged in a criss-cross pattern. The autophagic vacuoles exhibited acidic phosphatase activity. Axonal bodies were absorbed after degradation from day 7 onwards, and macrophages were observed rarely in the formative cavity. CONCLUSION: The degenerating axons were cleared mainly by axonal autophagy and Schwann cell phagocytosis during regeneration of the rat sciatic nerve, and macrophages exhibited only an assisting function. Key Words: axon; autophagy; nerve regeneration     

Effects of subcutaneous implant of peripheral nerve allograft on the regeneration of defected sciatic nerve

IN T R O D U C T IO NPeripheralnerve regeneration m ainly depends on m icroenvironem nt, w hich is com posed ofS chw ann cells and extracellularm atrix.M ostof extracellular m atrix is synthesized and released by S chw ann cells [1]. Therefore, the determ…     

Parthenolide：a novel pharmacological approach to promote nerve regeneration

正Traumatic axonal lesions disrupt the connections between neurons and their targets,leading to loss of motoric and sensory functions.Although lesioned peripheral nerves can principally regenerate,the rate of recovery depends on the mode and severity of the respective injury(Grinsell and Keating,2014).While injuries close to the innervation site have good chances of recovery,long distance regeneration     

Effects of tacrolimus （FK506） on sciatic nerve regeneration in rats

BACKGROUND： Tacrolimus （FK506） protects peripheral nerves located in damaged regions by inhibiting T lymphocyte proliferation and activation. OBJECTIVE： To evaluate the effect of FK506 on promoting regeneration of rat sciatic nerve. DESIGN, TIME AND SETTING： A randomized, controlled, animal study was performed at the Laboratory of the Department of Orthopedic Surgery, Dalian Medical University, China, from September 2007 to September 2008. MATERIALS： A total of 60 adult, male, Sprague-Dawley rats were equally and randomly divided into model, local administration and systemic administration groups. All rats received a neurotomy of bilateral sciatic nerves to establish models of nerve regeneration chambers. The powder and injection of FK506 were supplied by Fujisawa Pharmaceutical, Japan. METHODS： The regeneration chambers of the model group were infused with 0.2 mL saline. The systemic group were injected with 0.2 mL saline, followed by daily subcutaneous injections of FK506 （1 mg/kg）, for 14 days. The local administration group was infused with 0.2 mL FK506 （1 μg/mL）. MAIN OUTCOME MEASURES： Local immune response was observed using hematoxylin-eosin staining. Myelinated nerve fiber number, myelin sheath and nerve fiber thickness were observed using toluidine blue staining. Wet weight of gastrocnemius was evaluated. Compound muscle action potential amplitude, latency, and conduction time were recorded, and motor nerve conduction velocity was calculated using electrophysiology. RESULTS： The total number of myelinated nerve fibers in the local and systemic administration groups was significantly higher than in the model group. The density of myelinated nerve fibers, myelin sheath thickness and mean axon diameter were significantly increased in the systemic administration group compared with the model group （P 〈 0.05）. Lymphocyte infiltration was decreased in the local and systemic administration groups compared with the model group. The wet weight of rat gastrocnemius in the local and systemic administration groups were significantly greater compared with the model group （P 〈 0.05）. Motor nerve conduction velocity was the fastest in the systemic administration group, and the slowest in the model group. Compound muscle action potential amplitude was larger in the systemic administration group compared with the local administration and model groups （P 〈 0.05）. CONCLUSION： Systemic administration of FK506 can promote regeneration of rat sciatic nerve and recovery of neural function. Systemic administration produced better regeneration and recovery of function than local administration of FK506.     

Delayed peripheral nerve repair: methods,including surgical ‘cross-bridging' to promote nerve regeneration

Despite the capacity of Schwann cells to support peripheral nerve regeneration, functional recovery after nerve injuries is frequently poor, especially for proximal injuries that require regenerating axons to grow over long distances to reinnervate distal targets. Nerve transfers, where small fascicles from an adjacent intact nerve are coapted to the nerve stump of a nearby denervated muscle, allow for functional return but at the expense of reduced numbers of innervating nerves. A 1-hour period of 20 Hz electrical nerve stimulation via electrodes proximal to an injury site accelerates axon outgrowth to hasten target reinnervation in rats and humans, even after delayed surgery. A novel strategy of enticing donor axons from an otherwise intact nerve to grow through small nerve grafts(cross-bridges) into a denervated nerve stump, promotes improved axon regeneration after delayed nerve repair. The efficacy of this technique has been demonstrated in a rat model and is now in clinical use in patients undergoing cross-face nerve grafting for facial paralysis. In conclusion, brief electrical stimulation, combined with the surgical technique of promoting the regeneration of some donor axons to ‘protect' chronically denervated Schwa nn cells, improves nerve regeneration and, in turn, functional outcomes in the management of peripheral nerve injuries.     

Progesterone and peripheral nerve regeneration

IN T R O D U C T IO NVarious factors are involved in the process of regeneration after pe- ripheralnerve injury, including the m icroenvironm entofregeneration, neurotrophic factor, horm ones, etc. R ecent studies have found that progesterone plays an im …     

Propofol's effect on the sciatic nerve: Harmful or protective?

Propofol can inhibit the inflammatory response and reduce the secretion and harmful effects of astrocyte-derived proinflammatory cytokines.In this study,after propofol was injected into the injured sciatic nerve of mice,nuclear factor kappa B expression in the L4-6 segments of the spinal cord in the injured side was reduced,apoptosis was decreased,nerve myelin defects were alleviated,and the nerve conduction block was lessened.The experimental findings indicate that propofol inhibits the inflammatory and immune responses,decreases the expression of nuclear factor kappa B,and reduces apoptosis.These effects of propofol promote regeneration following sciatic nerve injury.     

Is the postganglionic sympathetic neuron zinc-enriched? A stop-flow nerve crush study on rat sciatic nerve.

Axonal transport of endogenous zinc ions in the rat sciatic nerve was studied by a stop-flow/nerve crush technique combined with zinc selenide autometallography (ZnSeAMG) at light and electron microscopic levels. Distinct accumulations of ZnSeAMG grains were detected, in particular proximal but also distal to the crushes, 1.5 h after the operation, and the amounts of zinc ions increased further in the following 3-8 h. Ultrastructurally, ZnSeAMG grains were located predominantly in unmyelinated axons. The data suggest that a subpopulation of sciatic nerve axons contains and transports zinc ions both antero- and retrogradely, indicating that the second neuron in the sympathetic nervous system is zinc enriched (ZEN).     

Does ventricular opening promote remote cerebellar haemorrhage?

Cerebellar haemorrhage after supratentorial craniotomy is a rare complication Because of its significant morbidity and mortality rates, being aware of this complication is important for early diagnosis. In a 30-year-old male with multiple intracranial cavernomas, remote cerebellar haemorrhage (RCH) was observed after removal of symptomatic left temporal lesion. The lateral wall of the temporal horn that was tightly attached to the cavernoma was also opened and excessive drainage of the CSF occurred. The haemorrhage is attributed to opening of the ventricle wall and excessive drainage of cerebrospinal fluid (CSF) during the procedure.     

What can Drosophila axonal development teach us about nerve regeneration?

<正>Assembly,maintenance and repair of nervous systems rely on the precise coordination in the presentation of guidance signals and the correct reception and processing of these signals.During embryonic development,considerable progress has already been made in identifying the extracellular cues and the receptors mediating axonal guidance(Araújo and Tear,2003).Axons are particularly vulnerable to injury and disease and axonal     

The progress in optic nerve regeneration,where are we?

Optic nerve regeneration is an important area of research. It can be used to treat patients suffering from optic neuropathy and provides insights into the treatment of numerous neurodegenerative diseases. There are many hurdles impeding optic regeneration in mammals. The mammalian central nervous system is non-permissive to regeneration and intrinsically lacks the capacity for axonal regrowth. Any axonal injury also triggers a vicious cycle of apoptosis. Understanding these hurdles provides us with a rough framework to appreciate the essential steps to bring about optic nerve regeneration: enhancing neuronal survival, axon regeneration, remyelination and establishing functional synapses to the original neuronal targets. In this review article, we will go through current potential treatments for optic nerve regeneration, which includes neurotrophic factor provision, inlfammatory stimulation, growth inhibition suppression, intracellular sig-naling modiifcation and modeling of bridging substrates.     

Does the vagus nerve mediate the sixth sense?

Can sensations originating from the internal environment modulate attitude and behaviour? Can the feedback about the operation of the viscera provide a calming and relaxing influence? Information from the chest and abdomen is delivered continuously by the vagus nerve, the largest visceral sensory nerve in the body. Because various 'stress-related' diseases can be associated with impaired functions in sensory vagal fibres, a better understanding of how sensory vagal information is processed in the CNS might offer new strategies for the treatment and/or prevention of several disorders, including 'drug-resistant' forms of eating disorder, anxiety, chronic depression and epilepsy. A neuronal circuitry that has been suggested by experimental data to mediate sensory vagal inputs to those brain areas that are involved in the generation of 'stress-related' disorders is outlined.     

Nerve allograft regeneration and immunological tolerance of rats with sciatic nerve transplantation after intragastric pretreatment with ultraviolet B-irradiated donor splenocytes★

BACKGROUND: Nerve allograft rejection is an unavoidable problem for nerve allografts. Traumatic peripheral nerve injuries are commonly reconstructed using autogenous nerve grafts. However, this form of reconstruction is limited by insufficient autologous nerves for large gap repairs and by morbidity at the nerve donor site. OBJECTIVE: To examine sciatic nerve regeneration and immune tolerance reaction after intragastric administration of ultraviolet B-irradiated (UVB) donor splenocytes. DESIGN, TIME AND SETTING: A complete randomized grouping design and controlled experiment. The experiments were conducted in the Department of Orthopedics, the First Affiliated Hospital to Shanxi Medical University, China, between March and October 2007. MATERIALS: Fourteen adult male SD rats and fourteen male Wistar rats, weighing 250–300 g, were randomly matched as donors and acceptors. A further seven male SD rats (weight 250–300 g, age 12–16 weeks) were used for nerve isografts. Immune preparations and the Epics XL flow cytometer were purchased from B-D Company, USA. A computer-assisted electromyograph machine was provided by Keypoint P, Dantel Company, Denmark. METHODS: Splenocytes from Wistar rats were isolated, purified, and cultured, and then irradiated with ultraviolet B. In the first control group (Group 1), the SD rats received a syngeneic SD nerve isograft. In the second control group (Group 2), the SD rats received a nerve allograft from Wistar rats without pretreatment. In the oral-tolerance treated group (Group 3), the SD recipient rats were inoculated with 2.5×107 Lewis UVB-irradiated donor splenocyte cells by intestinal tract administration at seven days before transplantation. MAIN OUTCOME MEASURES: (1) The recent end and the middle and distal end of the transplanted nerve were cut at 8 and 12 weeks after operation. Recovery of nerve regeneration was measured with HE staining using the total number, density, and diameter of the nerve fibers. (2) The level of CD25+T lymphocytes in peripheral blood was detected with the Epics XL flow cytometer at one week after operation. (3) The bilateral sciatic nerves were exposed from the sciatic notch up to 0.5 mm beyond the distal graft site at eight weeks post-engraftment. Bipolar platinum stimulating electrodes were placed under the sciatic nerve proximally and the mean conduction velocity was recorded with recording electrodes on the posterior tibial nerve at 0.3 cm distal to the nerve graft. RESULTS: Eight weeks after operation, total axon number and fiber density in Group 3 were higher than that in Group 1 (P < 0.05), neural regeneration in Group 3 was lower than that in Group 1 (P < 0.05) , The level of CD25+T lymphocytes in peripheral blood of Group 3 was significantly lower than that of Group 2 (P < 0.05). There was no significant difference between Group 3 and Group 1 (P > 0.05). At eight weeks post-engraftment the mean conduction velocity of Group 3 approximated that of Group 1. The untreated allografts in Group 2 demonstrated no measurable recovery of conduction velocity. CONCLUSION: Pretreatment with a single intragastric dose of UVB-modified donor antigen specifically induced tolerance to peripheral nerve allografts in rats. Key Words: sciatic nerve; transplantation, homologous; immune tolerance     

Nerve allograft regeneration and immunological tolerance of rats with sciatic nerve transplantation after intragastric pretreatment with ultraviolet B-irradiated donor splenocytes★

BACKGROUND: Nerve allograft rejection is an unavoidable problem for nerve allografts. Traumatic peripheral nerve injuries are commonly reconstructed using autogenous nerve grafts. However, this form of reconstruction is limited by insufficient autologous nerves for large gap repairs and by morbidity at the nerve donor site. OBJECTIVE: To examine sciatic nerve regeneration and immune tolerance reaction after intragastric administration of ultraviolet B-irradiated (UVB) donor splenocytes. DESIGN, TIME AND SETTING: A complete randomized grouping design and controlled experiment. The experiments were conducted in the Department of Orthopedics, the First Affiliated Hospital to Shanxi Medical University, China, between March and October 2007. MATERIALS: Fourteen adult male SD rats and fourteen male Wistar rats, weighing 250–300 g, were randomly matched as donors and acceptors. A further seven male SD rats (weight 250–300 g, age 12–16 weeks) were used for nerve isografts. Immune preparations and the Epics XL flow cytometer were purchased from B-D Company, USA. A computer-assisted electromyograph machine was provided by Keypoint P, Dantel Company, Denmark. METHODS: Splenocytes from Wistar rats were isolated, purified, and cultured, and then irradiated with ultraviolet B. In the first control group (Group 1), the SD rats received a syngeneic SD nerve isograft. In the second control group (Group 2), the SD rats received a nerve allograft from Wistar rats without pretreatment. In the oral-tolerance treated group (Group 3), the SD recipient rats were inoculated with 2.5×107 Lewis UVB-irradiated donor splenocyte cells by intestinal tract administration at seven days before transplantation. MAIN OUTCOME MEASURES: (1) The recent end and the middle and distal end of the transplanted nerve were cut at 8 and 12 weeks after operation. Recovery of nerve regeneration was measured with HE staining using the total number, density, and diameter of the nerve fibers. (2) The level of CD25+T lymphocytes in peripheral blood was detected with the Epics XL flow cytometer at one week after operation. (3) The bilateral sciatic nerves were exposed from the sciatic notch up to 0.5 mm beyond the distal graft site at eight weeks post-engraftment. Bipolar platinum stimulating electrodes were placed under the sciatic nerve proximally and the mean conduction velocity was recorded with recording electrodes on the posterior tibial nerve at 0.3 cm distal to the nerve graft. RESULTS: Eight weeks after operation, total axon number and fiber density in Group 3 were higher than that in Group 1 (P < 0.05), neural regeneration in Group 3 was lower than that in Group 1 (P < 0.05) , The level of CD25+T lymphocytes in peripheral blood of Group 3 was significantly lower than that of Group 2 (P < 0.05). There was no significant difference between Group 3 and Group 1 (P > 0.05). At eight weeks post-engraftment the mean conduction velocity of Group 3 approximated that of Group 1. The untreated allografts in Group 2 demonstrated no measurable recovery of conduction velocity. CONCLUSION: Pretreatment with a single intragastric dose of UVB-modified donor antigen specifically induced tolerance to peripheral nerve allografts in rats. Key Words: sciatic nerve; transplantation, homologous; immune tolerance