Brain-derived neurotrophic factor expression in dorsal root ganglion neurons in response to reanastomosis of the distal stoma after nerve grafting

Studies have shown that retreatment of the distal stoma after nerve grafting can stimulate nerve regeneration. The present study attempted to verify the effects of reanastomosis of the distal stoma, after nerve grafting, on nerve regeneration by assessing brain-derived neurotrophic factor expression in 2-month-old rats. Results showed that brain-derived neurotrophic factor expression in L 2-4 dorsal root ganglia began to increase 3 days after autologous nerve grafting post sciatic nerve injury, peaked at 14 days, decreased at 28 days, and reached similar levels to the sham-surgery group at 56 days. Brain-derived neurotrophic factor expression in L 2-4 dorsal root ganglia began to increase 3 days after reanastomosis of the distal stoma, 59 days after autologous nerve grafting post sciatic nerve injury, significantly increased at 63 days, peaked at 70 days, and gradually decreased thereafter, but remained higher compared with the sham-surgery group up to 112 days. The results of this study indicate that reanastomosis of the distal stoma after orthotopic nerve grafting stimulated brain-derived neurotrophic factor expression in L 2-4 dorsal root ganglia.     

Biodegradable magnesium wire promotes regeneration of compressed sciatic nerves

Magnesium(Mg) wire has been shown to be biodegradable and have anti-inflammatory properties. It can induce Schwann cells to secrete nerve growth factor and promote the regeneration of nerve axons after central nervous system injury. We hypothesized that biodegradable Mg wire may enhance compressed peripheral nerve regeneration. A rat acute sciatic nerve compression model was made, and AZ31 Mg wire(3 mm diameter; 8 mm length) bridged at both ends of the nerve. Our results demonstrate that sciatic functional index, nerve growth factor, p75 neurotrophin receptor, and tyrosine receptor kinase A m RNA expression are increased by Mg wire in Mg model. The numbers of cross section nerve fibers and regenerating axons were also increased. Sciatic nerve function was improved and the myelinated axon number was increased in injured sciatic nerve following Mg treatment. Immunofluorescence histopathology showed that there were increased vigorous axonal regeneration and myelin sheath coverage in injured sciatic nerve after Mg treatment. Our findings confirm that biodegradable Mg wire can promote the regeneration of acute compressed sciatic nerves.     

Effects of minocycline on apoptosis and angiogenesis-related protein expression in a rat model of intracerebral hemorrhage

In the present study, a rat model of non-traumatic intracerebral hemorrhage was established by type IV collagenase injection into the right globus pallidus. Bax and Bcl-2 expression in tissues surrounding hematomas was significantly increased within 14 days after injury, and it then gradually decreased. Vascular endothelial growth factor, Flk-1 and Flt-1 mRNA expression gradually increased over time. After intraperitoneal injection with minocycline, Bax expression was decreased 1 day after intracerebral hemorrhage. Flk-1 and Flt-1 mRNA expression was decreased after minocycline injection, but Bcl-2 expression was increased, and vascular endothelial growth factor mRNA expression was decreased between 4-14 days. These results indicated that protective effects of minocycline on nerve tissues were associated with increased Bcl-2 expression and decreased Bax expression in the early stage after intracerebral hemorrhage. In the late stage, minocycline downregulated vascular endothelial growth factor and its receptor expression to inhibit brain tissue self-repair.     

Apelin inhibits motor neuron apoptosis in the anterior horn following acute spinal cord and sciatic nerve injuries

Rat models of acute spinal cord injury and sciatic nerve injury were established.Apelin expression in spinal cord tissue was determined.In normal rat spinal cords,apelin expression was visible;however,2 hours post spinal cord injury,apelin expression peaked.Apelin expression increased 1 day post ligation of the sciatic nerve compared with normal rat spinal cords,and peaked at 3 days.Apelin expression was greater in the posterior horn compared with the anterior horn at each time point when compared with the normal group.The onset of neuronal apoptosis was significantly delayed following injection of apelin protein at the stump of the sciatic nerve,and the number of apoptotic cells after injury was reduced when compared with normal spinal cords.Our results indicate that apelin is expressed in the normal spinal cord and central nervous system after peripheral nerve injury.Apelin protein can reduce motor neuron apoptosis in the spinal cord anterior horn and delay the onset of apoptosis.     

Target inhibition of caspase-8 alleviates brain damage after subarachnoid hemorrhage

Caspase-8 plays an important role in the mediation of inflammation and the effect of its role in subarachnoid hemorrhage remains elusive.The nucleotide-binding oligomerization domain-like receptor protein 3 inflammasome has been postulated to mediate inflammation during SAH.The aim of the present study was to investigate the effects of caspase-8 inhibition on SAH injury and further elucidate the molecular mechanisms.In this study,a subarachnoid hemorrhage model was established by endovascular perforation process in adult male Sprague-Dawley rats.Z-IETD-FMK(0.5,1,2 mg/kg;an inhibitor of caspase-8)was delivered via intravenous(tail vein)injection immediately after subarachnoid hemorrhage.After 12 hours of subarachnoid hemorrhage,western blot assay showed that the expression of cleaved caspase-8 was significantly increased at 12 hours,peaked at 24 hours,and then decreased at 72 hours after subarachnoid hemorrhage.Immunofluorescence staining demonstrated that caspase-8 was expressed in microglia after subarachnoid hemorrhage.Z-IETDFMK significantly improved neurological deficits and reduced brain water content 24 hours after subarachnoid hemorrhage.The Morris water maze and rotarod test confirmed that Z-IETD-FMK significantly improved spatial learning and memory abilities and motor coordination at 21–27 days after subarachnoid hemorrhage.Furthermore,inhibition of caspase-8 activation reduced the expression of pyrin domain-containing 3,caspase-1,and interleukin-1βafter subarachnoid hemorrhage.In conclusion,our findings suggest that caspase-8 inhibition alleviates subarachnoid hemorrhage-induced brain injuries by suppressing inflammation.The study was approved by the Institutional Animal Ethics Committee of the First Affiliated Hospital,School of Medicine,Zhejiang University,China(approval No.2016-193)on February 25,2016.     

神经生长因子对氧合血红蛋白诱导鼠神经细胞凋亡的作用研究

目的 研究神经生长因子(NGF)对氧合血红蛋白(OxyHb)诱导的小鼠神经细胞凋亡的作用,进一步探讨OxyHb诱导细胞凋亡及NGF对神经元保护作用的可能机制.方法 蛛网膜下腔注射OxyHb建立蛛网膜下腔出血的动物模型,尾静脉注射NGF,TUNEL法检测神经细胞凋亡,免疫组织化学法检测Bcl-2、Bax、P75NTR和TrkA表达的情况.结果 注射OxyHb后出现神经细胞凋亡,Bcl-2表达降低,Bax和P75NTR表达增加,在NGF给药组,神经细胞凋亡数明显减少,Bcl-2表达增加.而Bax和P75NTR表达则明显降低.结论 小鼠局部脑组织蛛网膜下腔注射OxyHb可引起小鼠神经细胞发生凋亡,Bax和P75NTR表达增加可能是诱导凋亡的一个主要原因,而静脉注射NGF可以抑制OxyHb诱导的细胞凋亡,其机制可能是通过与受体结合,增加Bel-2蛋白表达,降低Bax和P75NTR表达水平以实现其保护作用.     

Vitamin B complex and vitamin B12 levels after peripheral nerve injury

The aim of the present study was to evaluate whether tissue levels of vitamin B complex and vitamin B12 were altered after crush-induced peripheral nerve injury in an experimental rat model. A total of 80 male Wistar rats were randomized into one control (n = 8) and six study groups (1, 6, 12, 24 hours, 3, and 7 days after experimental nerve injury;n = 12 for each group). Crush-induced peripheral nerve injury was per-formed on the sciatic nerves of rats in six study groups. Tissue samples from the sites of peripheral nerve injury were obtained at 1, 6, 12, 24 hours, 3 and 7 days after experimental nerve injury. Enzyme-linked immunosorbent assay results showed that tissue levels of vitamin B complex and vitamin B12 in the injured sciatic nerve were signiifcantly greater at 1 and 12 hours after experimental nerve injury, while they were signiifcantly lower at 7 days than in control group. Tissue level of vitamin B12 in the injured sciatic nerve was signiifcantly lower at 1, 6, 12 and 24 hours than in the control group. These results suggest that tissue levels of vitamin B complex and vitamin B12 vary with progression of crush-induced peripheral nerve injury, and supplementation of these vitamins in the acute period may be beneficial for acceleration of nerve regeneration.     

Nerve growth factor promotes in vitro proliferation of neural stem cells from tree shrews

Neural stem cells promote neuronal regeneration and repair of brain tissue after injury,but have limited resources and proliferative ability in vivo.We hypothesized that nerve growth factor would promote in vitro proliferation of neural stem cells derived from the tree shrews,a primate-like mammal that has been proposed as an alternative to primates in biomedical translational research.We cultured neural stem cells from the hippocampus of tree shrews at embryonic day 38,and added nerve growth factor(100 μg/L) to the culture medium.Neural stem cells from the hippocampus of tree shrews cultured without nerve growth factor were used as controls.After 3 days,fluorescence microscopy after DAPI and nestin staining revealed that the number of neurospheres and DAPI/nestin-positive cells was markedly greater in the nerve growth factor-treated cells than in control cells.These findings demonstrate that nerve growth factor promotes the proliferation of neural stem cells derived from tree shrews.     

Early expressions of hypoxia-inducible factor 1alpha and vascular endothelial growth factor increase the neuronal plasticity of activated endogenous neural stem cells after focal cerebral ischemia

Endogenous neural stem cells become "activated" after neuronal injury, but the activation sequence and fate of endogenous neural stem cells in focal cerebral ischemia model are little known. We evaluated the relationships between neural stem cells and hypoxia-inducible factor-1α and vascular endothelial growth factor expression in a photothromobotic rat stroke model using immunohistochemistry and western blot analysis. We also evaluated the chronological changes of neural stem cells by 5-bromo-2′-deoxyuridine(BrdU) incorporation. Hypoxia-inducible factor-1α expression was initially increased from 1 hour after ischemic injury, followed by vascular endothelial growth factor expression. Hypoxia-inducible factor-1α immunoreactivity was detected in the ipsilateral cortical neurons of the infarct core and peri-infarct area. Vascular endothelial growth factor immunoreactivity was detected in bilateral cortex, but ipsilateral cortex staining intensity and numbers were greater than the contralateral cortex. Vascular endothelial growth factor immunoreactive cells were easily found along the peri-infarct area 12 hours after focal cerebral ischemia. The expression of nestin increased throughout the microvasculature in the ischemic core and the peri-infarct area in all experimental rats after 24 hours of ischemic injury. Nestin immunoreactivity increased in the subventricular zone during 12 hours to 3 days, and prominently increased in the ipsilateral cortex between 3–7 days. Nestin-labeled cells showed dual differentiation with microvessels near the infarct core and reactive astrocytes in the peri-infarct area. BrdU-labeled cells were increased gradually from day 1 in the ipsilateral subventricular zone and cortex, and numerous BrdU-labeled cells were observed in the peri-infarct area and non-lesioned cortex at 3 days. BrdU-labeled cells rather than neurons, were mainly co-labeled with nestin and GFAP. Early expressions of hypoxia-inducible factor-1α and vascular endothelial growth factor after ischemia made up the microenvironment to increase the neuronal plasticity of activated endogenous neural stem cells. Moreover, neural precursor cells after large-scale cortical injury could be recruited from the cortex nearby infarct core and subventricular zone.     

Expression of Endopeptidase-24.11 (Common Acute Lymphoblastic Leukaemia Antigen CDI0) in the Sciatic Nerve of the Adult Rat After Lesion and During Regeneration

Endopeptidase-24.11, which is identical with the common acute lymphoblastic leukaemia antigen CD1O (CALLA), is a cell surface Zn²⁺ metalloprotease that regulates peptide-induced responses in different tissues, including the nervous and immune systems. In the peripheral nervous system, high levels of the enzyme are present in all neonatal and early postnatal Schwann cells, while as myelination proceeds it is gradually suppressed in the majority of cells that form myelin but retained in non-myelin-forming cells in the adult animal. In the present study we have investigated the effects of transection, crush and regeneration of the adult rat sciatic nerve on the expression of the endopeptidase by Schwann cells in situ. Endopeptidase-24.11 was monitored by immunocytochemistry using the monoclonal anti-endopeptidase antibody 23811. For comparison, a parallel study was carried out with a monoclonal antibody directed against the rat nerve growth factor receptor. We found that (i) all Schwann cells of the distal segment re-expressed endopeptidase-24.11 as early as 4 days after axotomy, the level of immunostaining reaching a maximum after 2 weeks, (ii) axonal regeneration repressed Schwann cell expression of endopeptidase-24.11, and (iii) the induction of the nerve growth factor receptor followed a similar pattern to that of endopeptidase-24.11 in the transected and crushed nerve. Enzymatic amplification of endopeptidase-24.11 cDNA from normal and axotomized adult rat sciatic nerve confirmed the expression of endopeptidase-24.11 in these tissues. Our results show that the expression of endopeptidase-24.11 in Schwann cells, as is the case with the nerve growth factor receptor, is induced by the loss of the normal axon-Schwann cell contact. The significant increase in the expression of endopeptidase-24.11 by Schwann cells after axonal damage suggests that the enzyme could play a role in axonal regeneration.     

Human umbilical cord blood-derived mesenchymal stem cells promote regeneration of crush-injured rat sciatic nerves

Several studies have demonstrated that human umbilical cord blood-derived mesenchymal stem cells can promote neural regeneration following brain injury. However, the therapeutic effects of human umbilical cord blood-derived mesenchymal stem cells in guiding peripheral nerve regeneration remain poorly understood. This study was designed to investigate the effects of human umbilical cord blood-derived mesenchymal stem cells on neural regeneration using a rat sciatic nerve crush injury model. Human umbilical cord blood-derived mesenchymal stem cells (1 × 10 6 ) or a PBS control were injected into the crush-injured segment of the sciatic nerve. Four weeks after cell injection, brain-derived neurotrophic factor and tyrosine kinase receptor B mRNA expression at the lesion site was increased in comparison to control. Furthermore, sciatic function index, Fluoro Gold-labeled neuron counts and axon density were also significantly increased when compared with control. Our results indicate that human umbilical cord blood-derived mesenchymal stem cells promote the functional recovery of crush-injured sciatic nerves.     

A decline in glial cell-line-derived neurotrophic factor expression is associated with impaired regeneration after long-term Schwann cell denervation.

In the peripheral nervous system, regeneration of motor and sensory axons into chronically denervated distal nerve segments is impaired compared to regeneration into acutely denervated nerves. In order to find possible causes for this phenomenon we examined the changes in the expression pattern of the glial cell-line-derived neurotrophic factor (GDNF) family of growth factors and their receptors in chronically denervated rat sciatic nerves as a function of time with or without regeneration. Among the GDNF family of growth factors, only GDNF mRNA expression was rapidly upregulated in Schwann cells as early as 48 h after denervation. This upregulation peaked at 1 week and then declined to minimal levels by 6 months of denervation. The changes in the protein expression paralleled the changes in the expression of the GDNF mRNA. The mRNAs for receptors GFRalpha-1 and GFRalpha-2 were upregulated only after maximal GDNF upregulation and remained elevated as late as 6 months. There were no significant changes in the expression of GFRalpha-3 or the tyrosine kinase coreceptor, RET. When we examined the expression of GDNF in a delayed regeneration paradigm, there was no upregulation in the distal chronically denervated tibial nerve even when the freshly axotomized peroneal branch of the sciatic nerve was sutured to the distal tibial nerve. This study suggests that one of the reasons for impaired regeneration into chronically denervated peripheral nerves may be the inability of Schwann cells to maintain important trophic support for both motor and sensory neurons.     

大鼠脑出血后不同时期神经营养因子受体p75、神经生长因子前体、酪氨酸激酶A的表达及其与细胞凋亡的相关性

目的研究脑出血后血肿周围组织中神经营养因子受体p75(p75NTR)、神经生长因子前体(pro NGF)、酪氨酸激酶A(TrkA)的表达及细胞凋亡率,进一步探讨其在脑出血后的细胞凋亡中所发挥的作用。方法制作大鼠脑出血模型,于术后6 h、24 h、72 h、10 d处死各组大鼠获取所需脑组织标本,应用流式细胞仪检测细胞凋亡率,免疫组化SP法检测p75 NTR、TrkA、pro NGF的蛋白表达水平,实时荧光定量PCR检测p75 NTR、TrkA的基因表达水平。结果脑出血后p75 NTR、proNGF表达水平及p75 NTR/TrkA值与对照组比较显著升高(P 0. 01),且动态变化规律与脑细胞凋亡率相似;72 h后TrkA的动态变化规律与细胞凋亡率相反。结论脑出血后pro NGF与p75 NTR的结合可能参与介导脑细胞凋亡,p75 NTR/TrkA值增高时,pro NGF及p75 NTR以介导细胞凋亡为主; TrkA在脑出血后72 h内神经营养作用被抑制,72 h后可能发挥神经营养作用。     

Expression of Nogo-A mRNA after injury of the rat central nervous system

BACKGROUND： Nogo protein has been identified as an inhibitor of axonal growth, which was highly expressed in central nervous system; however, there are only a few studies on changes of Nogo-A expression following central nervous system injury. OBJECTIVE： To investigate the dynamic expression of Nogo-A mRNA after rat central nervous system injury. DESIGN： Randomized controlled animal study. MATERIALS： Thirty-five rats were randomly divided into two groups, normal animal group （n = 5） and model group （n = 30）. The model group was then divided into six subgroups at six time points： 12, 24 hours and 3, 9, 15, and 21 days post-injury, with five rats in each subgroup. METHODS： The left parietal lobe of rats was contused by free-fall strike, and total RNA was extracted from the entire brain tissue. Semi-quantitative RT-PCR was used to detect Nogo-A mRNA expression, and the ratio between expression of the target gene and glyceraldehyde phosphate dehydrogenase was used to determine the relative expression level. MAIN OUTCOME MEASURES： To determine whether Nogo-A mRNA expression was higher than usual following brain injury. RESULTS： The level of Nogo-A mRNA started to increase 12 hours after injury （P 〈 0.05） and decreased slightly by 24 hours post-injury. Expression increased again on day 3 and reached a peak on day 9. Nogo-A mRNA expression started to decrease on day 15, and then decreased to normal levels at days 21 （P 〉 0.05）. CONCLUSION： After injury of the central nervous system, Nogo-A may play a pivotal role in obstructing regeneration of the nerve.     

Study on molecular mechanism for improving neural regeneration after repair of sciatic nerve defect in rat by acellular nerve allograft

Objective: Discuss the molecular mechanism for improving neural regeneration after repair of sciatic nerve defect in rat by acellular nerve allograft (ANA). Methods: Randomly divide 36 Wistar rats into six groups as normal control group, autografting group, and bridging groups of 2, 4, 8, 12 weeks, six rats for each group. Observe the expression of brain‐derived neurotrophic factor (BDNF) in L₄ spinal cord and anterior tibial muscle at the injury site, calcitonin gene‐related peptide (CGRP) protein as well as mRNA, respectively. 12w after operation, histopathological observation was performed. Results: 2w after ANA bridging the sciatic nerve defect in rats, it was observed that the expression level of BDNF in spinal cord at the injury site and CGRP protein increased, reaching the peak level at 4w, lasting till 8w, then decreased but still significantly higher than that in normal control group at 12w, and was not significantly different compared with that in autografting group. However, the expression level of BDNF in anterior tibial muscle decreased gradually within the initial 4w, then increased progressively, reaching normal level at 12w, and was not significantly different compared with that in autografting group. The expression of BDNF mRNA and CGRPmRNA was essentially the same. 12w after operation, there was nerve regeneration in bridging group of 12w and autografting group. Conclusions: ANA possessed fine histocompatibility, and might substitute autograft to repair long‐segment defect of sciatic nerve in rats. This action might be related to upregulation of protein and mRNA expression for BDNF and CGRP in spinal cord. Synapse, 2012. © 2011 Wiley Periodicals, Inc.     

Differential regulation of S100 beta and mRNAs coding for S100-like proteins (42A and 42C) during development and after lesion of rat sciatic nerve

The changes in the levels of S100 beta (a protein that stimulates neurite extension and neuronal survival) and 42A and 42C (S100-like proteins whose mRNAs are induced in PC12 cells by nerve growth factor) during development and after rat sciatic nerve lesions were analyzed. S100 beta, 42A, and 42C mRNAs showed differential regulation during development. S100 beta mRNA was present both in sciatic nerve and brain, and increased more than 11-fold during the first 3 wk of nerve postnatal development. 42A and 42C mRNAs were essentially restricted to sciatic nerve, with little found in either embryonic or adult brain. The levels of 42C and 42A mRNAs in sciatic nerve increased 4- and 14-fold, respectively, by postnatal day 23 compared to postnatal day 2. 42A, 42C, and S100 beta mRNAs also showed a differential regulation during sciatic nerve degeneration and regeneration. Axotomized and control sciatic nerves were examined by Northern blots at various times after a crush or cut injury. 42A and 42C mRNA levels increased rapidly in the distal segment of axotomized nerve, remained two- to five-fold higher than controls at day 14 after injury but returned to control levels by 40 days. In contrast, S100 beta mRNA showed a three-fold decrease in the axotomized nerve between days 1 and 3 after injury, and slowly returned towards control levels over the next few weeks. The decrease in S100 beta mRNA was reflected by a corresponding decrease in S100 beta protein levels. The induction of 42A and 42C mRNAs and repression of S100 beta mRNA remained if nerve regeneration was prevented.(ABSTRACT TRUNCATED AT 250 WORDS)     

Time- and cell-type speciifc changes in iron,ferritin, and transferrin in the gerbil hippocampal CA1 region after transient forebrain ischemia

In the present study, we used immunohistochemistry and western blot analysis to examine changes in the levels and cellular localization of iron, heavy chain ferritin (ferritin-H), and transferrin in the gerbil hippocampal CA1 region from 30 minutes to 7 days following transient forebrain ischemia. Relative to sham controls, iron reactivity increased signiifcantly in the stratum pyramidale and stratum oriens at 12 hours following ischemic insult, transiently decreased at 1–2 days and then increased once again within the CA1 region at 4–7 days after ischemia. One day after ischemia, ferritin-H immunoreactivity increased significantly in the stratum pyramidale and decreased at 2 days. At 4–7 days after ischemia, ferritin-H immunoreactivity in the glial components in the CA1 region was signiifcantly increased. Transferrin im-munoreactivity was increased signiifcantly in the stratum pyramidale at 12 hours, peaked at 1 day, and then decreased signiifcantly at 2 days after ischemia. Seven days after ischemia, Transferrin immunoreactivity in the glial cells of the stratum oriens and radiatum was signiifcantly increased. Western blot analyses support-ed these results, demonstrating that compared to sham controls, ferritin H and transferrin protein levels in hippocampal homogenates significantly increased at 1 day after ischemia, peaked at 4 days and then decreased. These results suggest that iron overload-induced oxidative stress is most prominent at 12 hours after ischemia in the stratum pyramidale, suggesting that this time window may be the optimal period for therapeutic intervention to protect neurons from ischemia-induced death.     

Minocycline inhibits the production of the precursor form of nerve growth factor by retinal microglial cells

A rat model of acute ocular hypertension was established by enhancing the perfusion of balanced salt solution in the anterior chamber of the right eye. Minocycline (90 mg/kg) was administered intraperitoneally into rats immediately after the operation for 3 consecutive days. Immunofluorescence, western blot assay and PCR detection revealed that the expression of the precursor form of nerve growth factor, nerve growth factor and the p75 neurotrophin receptor, and the mRNA expression of nerve growth factor and the p75 neurotrophin receptor, increased after acute ocular hypertension. The number of double-labeled CD11B- and precursor form of nerve growth factor-positive cells, glial fibrillary acidic protein- and p75 neurotrophin receptor-positive cells, glial fibrillary acidic protein- and caspase-3-positive cells in the retina markedly increased after acute ocular hypertension. The above-described expression decreased after minocycline treatment. These results suggested that minocycline inhibited the increased expression of the precursor form of nerve growth factor in microglia, the p75 neurotrophin receptor in astroglia, and protected cells from apoptosis.