BDNF-exercise interactions in the recovery of symmetrical stepping after a cervical hemisection in rats

Clinical evidence indicates that motor training facilitates functional recovery after a spinal cord injury (SCI). Brain-derived neurotrophic factor (BDNF) is a powerful synaptic facilitator and likely plays a key role in motor and sensory functions. Spinal cord hemisection decreases the levels of BDNF below the injury site, and exercise can counteract this decrease [Ying Z, Roy RR, Edgerton VR, Gomez-Pinilla F (2005) Exercise restores levels of neurotrophins and synaptic plasticity following spinal cord injury. Exp Neurol 193:411-419]. It is not clear, however, whether the exercise-induced increases in BDNF play a role in mediating the recovery of locomotion after a SCI. We performed a lateral cervical ( approximately C4) hemisection in adult rats. Seven days after hemisection, the BDNF inhibitor trkB IgG was injected into the cervical spinal cord below the lesion ( approximately C5-C6). Half of the rats were exposed to voluntary running wheels for 14 days. Locomotor ability was assessed by determining the symmetry between the contralateral (unaffected) vs. the ipsilateral (affected) forelimb at the most optimum treadmill speed for each rat. Sedentary and exercised rats with BDNF inhibition showed a higher level of asymmetry during the treadmill locomotion test than rats not treated with the BDNF inhibitor. In hemisected rats, exercise normalized the levels of molecules important for synaptic function, such as cyclic AMP response element binding protein (CREB) and synapsin I, in the ipsilateral cervical enlargement, whereas the BDNF blocker lessened these exercise-associated effects. The results indicate that BDNF levels play an important role in shaping the synaptic plasticity and in defining the level of recovery of locomotor performance after a SCI.     

臂丛损伤再生中GAP-43 mRNA及其蛋白的表达

目的：分析臂丛损伤后脊髓前角运动神经元表达GAP-43 mRNA及其蛋白的变化规律，探讨神经损伤再生的机制。方法：建立3种臂丛损伤模型：右C₇前根撕脱（A组）；右C₇前根撕脱＋同侧C5-T₁后根断离（B组）；右C₇前根撕脱+右C₅C₆间脊髓半横断（C组）。用荧光定量RT-PCR方法检测术后14 d时 C₇前角GAP-43 mRNA的表达量。用免疫组化方法检测术后1、 3、 7、14 d脊髓前角GAP-43免疫阳性运动神经元的表达。结果：对照组C₇前角GAP-43 mRNA呈低表达，损伤组GAP-43 mRNA表达显著上调。损伤组术后1 d、3 d时均未见C₇前角 GAP-43免疫阳性神经元，术后7 d各损伤组GAP-43免疫阳性神经元开始出现，14 d时免疫阳性神经元数目达到高峰。3组间比较，C组表达量最高，B组最低，A组居中。结论：臂丛损伤诱导运动神经元GAP-43 mRNA及其蛋白表达上调，GAP-43合成增加是神经元蛋白重组所致，与轴索再生和神经功能重建有关。     

Recovery of inspiratory intercostal muscle activity following high cervical hemisection

Anatomical and neurophysiological evidence indicates that thoracic interneurons can serve a commissural function and activate contralateral motoneurons. Accordingly, we hypothesized that respiratory-related intercostal (IC) muscle electromyogram (EMG) activity would be only modestly impaired by a unilateral cervical spinal cord injury. Inspiratory tidal volume (VT) was recorded using pneumotachography and EMG activity was recorded bilaterally from the 1st to 2nd intercostal space in anesthetized, spontaneously breathing rats. Studies were conducted at 1-3 days, 2 wks or 8 wks following C2 spinal cord hemisection (C2HS). Data were collected during baseline breathing and a brief respiratory challenge (7% CO(2)). A substantial reduction in inspiratory intercostal EMG bursting ipsilateral to the lesion was observed at 1-3 days post-C2HS. However, a time-dependent return of activity occurred such that by 2 wks post-injury inspiratory intercostal EMG bursts ipsilateral to the lesion were similar to age-matched, uninjured controls. The increases in ipsilateral intercostal EMG activity occurred in parallel with increases in VT following the injury (R=0.55; P<0.001). We conclude that plasticity occurring within a "crossed-intercostal" circuitry enables a robust, spontaneous recovery of ipsilateral intercostal activity following C2HS in rats.     

Temporal changes in the level of neurotrophins in the spinal cord and associated precentral gyrus following spinal hemisection in adult Rhesus monkeys

Neurotrophins (NTs) appear to be crucial for the survival and potential regeneration of injured neurons. However, their temporal changes and remote regulations following spinal cord injury (SCI) have been only partially determined, especially in primates. In this study, ELISA was performed on the extracts of injured spinal cord and the associated precentral gyrus contralateral to the site of spinal cord hemisection to investigate the temporal changes in the levels of nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT-3) and neurotrophin-4 (NT-4) in adult rhesus monkeys subjected to T8 spinal hemisection. Animals were allowed to survive 3, 7, 14, 30 and 90 days post-operation (dpo). In the spinal cord, the levels of NGF, BDNF and NT-3 sharply decreased between 3 and 7 dpo. Thereafter, the levels of NGF and BDNF were transiently elevated while NT-3 level continuously increased and recovered to normal level at 30 dpo. In the contralateral precentral gyrus (cPG), only the NT-3 level was altered and in fact elevated above the normal value. No obvious changes were observed in NT-4 level in any of the regions studied. Taken together, the present findings indicated that intrinsic NGF, BDNF and NT-3 may play a local role in the responses to the SCI in primates. Especially, the increase of NT-3 level occurred continuously in both the cPG and the spinal cord pointed to a possible transportation of NT-3 to the cord following SCI.     

Temporal changes in the level of neurotrophins in the spinal cord and associated precentral gyrus following spinal hemisection in adult Rhesus monkeys

Neurotrophins (NTs) appear to be crucial for the survival and potential regeneration of injured neurons. However, their temporal changes and remote regulations following spinal cord injury (SCI) have been only partially determined, especially in primates. In this study, ELISA was performed on the extracts of injured spinal cord and the associated precentral gyrus contralateral to the site of spinal cord hemisection to investigate the temporal changes in the levels of nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT-3) and neurotrophin-4 (NT-4) in adult rhesus monkeys subjected to T8 spinal hemisection. Animals were allowed to survive 3, 7, 14, 30 and 90 days post-operation (dpo). In the spinal cord, the levels of NGF, BDNF and NT-3 sharply decreased between 3 and 7dpo. Thereafter, the levels of NGF and BDNF were transiently elevated while NT-3 level continuously increased and recovered to normal level at 30dpo. In the contralateral precentral gyrus (cPG), only the NT-3 level was altered and in fact elevated above the normal value. No obvious changes were observed in NT-4 level in any of the regions studied. Taken together, the present findings indicated that intrinsic NGF, BDNF and NT-3 may play a local role in the responses to the SCI in primates. Especially, the increase of NT-3 level occurred continuously in both the cPG and the spinal cord pointed to a possible transportation of NT-3 to the cord following SCI.     

小鼠颈脊髓半侧挫伤模型的建立及其组织学特点

目的　建立基于位移控制的C57/6J小鼠C5脊髓半侧挫伤模型,观察其脊髓组织学改变。 方法　C57BL/6小鼠在麻醉状态下行C5左侧椎板切除术,打击头（直径0.75 mm）对准C5左侧,由电磁伺服材料试验机驱动挫伤脊髓,设定打击位移0.9 mm,打击速度50 mm/s。损伤后1周脊髓标本取材,EC染色,作组织学定量分析。 结果　打击参数结果稳定性与重复性良好。打击位移、打击速度和打击力分别为（0.880±0.035）mm、（48.146±4.367）mm/s、（0.407±0.129）N,损伤中心的脊髓组织学表现为：伤侧脊髓有明显的出血及正常组织结构破坏,脊髓背侧束、脊髓后角和部分前角有破坏;健侧脊髓结构基本保持完整。计算损伤中心平面的残存灰质比例、残存白质比例及损伤面积比例分别为（19±7）%、（88±9）%及（28±4）%。 结论　本研究成功建立小鼠颈脊髓半侧挫伤模型,此模型具有重复性较好的力学参数,表现出典型的单侧颈脊髓损伤的组织学特征,可为脊髓损伤分子机制和治疗研究奠定基础。     

Expression of GAP-43 mRNA in the adult mammalian spinal cord under normal conditions and after different types of lesions,with special reference to motoneurons

Summary In situ hybridization histochemistry was used to detect cell bodies expressing mRNA encoding for the phosphoprotein GAP-43 in the lumbosacral spinal cord of the adult rat, cat and monkey under normal conditions and, in the cat and rat, also after different types of lesions. In the normal spinal cord, a large number of neurons throughout the spinal cord gray matter were found to express GAP-43 mRNA. All neurons, both large and small, in the motor nucleus (Rexed's lamina IX) appeared labeled, indicating that both alpha and gamma motoneurons express GAP-43 mRNA under normal conditions. After axotomy by an incision in the ventral funiculus or a transection of ventral roots or peripheral nerves, GAP-43 mRNA was clearly upregulated in axotomized motoneurons, including both alpha and gamma motoneurons. An increase in GAP-43 mRNA expression was already detectable 24 h postoperatively in lumbar motoneurons both after a transection of the sciatic nerve at knee level and after a transection of ventral roots. At this time, a stronger response was seen in the motoneurons which had been subjected to the distal sciatic nerve transection than was apparent for the more proximal ventral root lesion. An upregulation of GAP-43 mRNA could also be found in intact motoneurons located on the side contralateral to the lesion, but only after a peripheral nerve transection, indicating that the concomitant influence of dorsal root afferents may play a role in GAP-43 mRNA regulation. However, a dorsal root transection alone did not seem to have any detectable influence on the expression of GAP-43 mRNA in spinal motoneurons, while the neurons located in the superficial laminae of the dorsal horn responded with an upregulation of GAP-43 mRNA. The presence of high levels of GAP-43 in neurons has been correlated with periods of axonal growth during both development and regeneration. The role for GAP-43 in neurons under normal conditions is not clear, but it may be linked with events underlying remodelling of synaptic relationships or transmitter release. Our findings provide an anatomical substrate to support such a hypothesis in the normal spinal cord, and indicate a potential role for GAP-43 in axon regeneration of the motoneurons, since GAP-43 mRNA levels was strongly upregulated following both peripheral axotomy and axotomy within the spinal cord. The upregulation of GAP-43 mRNA found in contralateral, presumably uninjured motoneurons after peripheral nerve transection, as well as in dorsal horn neurons after a dorsal root transection, indicates that GAP-43 levels are altered not only as a direct consequence of a lesion, but also after changes in the synaptic input to the neurons.     

α-硫辛酸对大鼠全横断脊髓损伤后GAP-43和Caspase-3表达的影响

目的:研究α-硫辛酸对脊髓全横断损伤(SCI)大鼠损伤部位神经生长相关蛋白(GAP-43)、神经细胞凋亡相关蛋白(Caspase-3)的表达,探讨α-硫辛酸对大鼠脊髓全横断损伤功能恢复的作用。方法:制作并评价SD大鼠SCI模型后,64只大鼠随机分为假手术组、脊髓损伤组(SCI组)、SCI+游泳训练组(游泳组)和SCI+α-硫辛酸组(硫辛酸组)。各组按手术后7、14、21、28 d等4个时间点收集标本,每个时间点大鼠均为4只。各组大鼠进行BBB评分。各组4个时间点的GAP-43和Caspase-3表达用免疫组化测定,同时用Western Blot检测GAP-43表达。结果:游泳训练和用硫辛酸均能提高脊髓损伤大鼠的BBB评分(P0.05)。与SCI组比较,游泳组和硫辛酸组GAP-43表达显著增加,Caspase-3表达则明显降低(P0.05),且硫辛酸组比游泳组的GAP-43表达增加和Caspase-3表达降低更为明显(P0.05)。结论:游泳训练和α-硫辛酸可以上调脊髓损伤大鼠GAP-43表达和抑制Caspase-3表达促进损伤神经修复,对改善大鼠运动功能有一定疗效。     

Increase of extensor tonus of forelimbs in chronic cats with bilateral serial hemisections of the spinal cord at different levels

An increase of extensor tonus of the forelimbs was observed in chronic cats with serial double hemisections of the spinal cord, first at a lower thoracic level followed by a contralateral hemisection at the midthoracic cord at intervals of 5-18 weeks. A similar increase in forelimb extensor tonus was observed in chronic cats with serial double hemisections, first at the high cervical cord followed by a contralateral hemisection of the mid-thoracic cord at intervals of 3-7 weeks. The results suggest that the augmentation of extensor tonus was brought about by release of bulbar centers from ascending inhibitory mechanisms from the lower spinal cord.     

Transcranial magnetic stimulation: Cortical motor maps in acute spinal cord injury

Summary This investigation examined the motor pathways of four, C5-6 spinal cord injured (SCI) patients within 6–17 days of injury. Mapping of the motor cortex was achieved by transcranial magnetic stimulation (TMS) applied to the scalp. Motor evoked potentials were recorded from target muscle groups (Biceps brachii and Abductor pollicis brevis m.). Evidence of an expanded cortical map of the preserved contralateral biceps muscle was demonstrated in these patients as early as 6 days. These findings suggested that early motor re-organization may occur following acute cervical spinal cord injury in man.     

抗BDNF血清对小鼠坐骨神经损伤后脊髓前角运动神经元内GAP-43表达的影响

小鼠坐骨神经压榨损伤后 ,腹腔注射抗 BDNF血清 ,动物存活 2周。用组织原位杂交技术与免疫组织化学方法观察生长相关蛋白 ( GAP-4 3)在脊髓腰骶膨大部前角运动神经元的表达 ,并对实验结果进行图像分析。结果发现 ,注射抗 BDNF血清后坐骨神经损伤侧脊髓前角 GAP-4 3m RNA的阳性神经元与 GAP-4 3免疫反应阳性神经元的数目减少 ,阳性神经元的光密度也降低 ,上述改变在统计学上均有显著意义。结果提示 ,小鼠坐骨神经损伤后内源性 BDNF可能参与脊髓前角运动神经元 GAP-4 3的表达     

银杏酮酯对大鼠坐骨神经损伤后生长相关蛋白43表达的影响

目的:研究银杏酮酯对大鼠坐骨神经损伤后生长相关蛋白43(GAP-43)表达的影响。方法:SD大鼠78只,随机分成正常组、损伤对照组与实验组,给予不同处理,后两组切断右侧坐骨神经并缝合。实验组给予银杏酮酯200mg·kg-1.d-1溶于1ml生理盐水中灌胃,损伤对照组给予生理盐水1ml灌胃,正常组不做处理。分别于术后1、3、7、14、21及28d取吻合口远段的神经、相应节段的脊神经节及脊髓,应用免疫组织化学和图像分析的方法研究所取组织中GAP-43蛋白的表达并进行定量分析。结果:实验组坐骨神经、脊神经节及脊髓中GAP-43蛋白免疫阳性区域面积和平均光密度值在术后7、14和21d明显高于对照组。结论:大鼠坐骨神经损伤后用银杏酮酯治疗,在早期可促使坐骨神经及相应节段脊神经节和脊髓组织中的GAP-43蛋白表达增加。     

Evaluation of cellular organization and axonal regeneration through linear PLA foam implants in acute and chronic spinal cord injury

There are few studies of neural implants in spinal cord injury (SCI) focused on supporting directed axon growth. In this study, we fabricated a macroporous poly (lactic acid) (PLA) foam with oriented inner channels. Amorphous foam without linear channels served as a control in an acute SCI injury model, and the effectiveness of foam with linear channels was further investigated in a chronic SCI model. Implants were placed into a 2 mm hemisection lesion cavity at the T8 spinal cord level in adult rats. Two weeks post-implantation, tissue sections including the implants were examined using antibodies against GFAP, p75, ED-1, laminin, GAP-43, and CGRP. Foam implants were well-integrated with the host spinal cord. In linear foams, numerous DAPI-stained cells were found within the inner channels. Schwann cells but not astrocytes had migrated within the channels. Intense laminin staining was observed throughout the extracellular matrix substrate. GAP-43- and CGRP-positive axons grew through the implants following the linear channels. In the amorphous control foams, DAPI staining distributed evenly through the pores. However, the growth of GAP-43 or CGRP-positive axons was misguided and impeded at the entrance area of the foam. Higher numbers of GAP-43 and CGRP-positive axons grew into linear foam implants after chronic SCI than acute SCI. These results suggest the potential application of linear foam implants in cell and axon guidance for SCI repair, especially for chronic SCI.     

5-HT_(1A)受体亚型mRNA在坐骨神经分支选择性损伤模型大鼠脊髓和背根节中的表达变化(英文)

坐骨神经分支选择性损伤 (SNI)模型是一种新型神经病理痛模型。本实验用 SD雄性大鼠 ,分支结扎并切断左侧坐骨神经干的胫神经和腓总神经 ,保留腓肠神经分支 ,右侧仅暴露坐骨神经。术后 1、2、3、4、7、14、2 1和 2 8d,用 RT-PCR的方法对 5 -HT1 A受体 m RNA在腰髓的背角和背根神经节 (DRG)的表达水平进行检测。结果显示 ,5 -HT1 A受体 m RNA在损伤侧腰髓背角内的表达水平于 1d后开始升高 ,7d时达高峰 ,随后逐渐下降 ,但仍高于正常水平。其表达水平在对侧脊髓背角内没有明显变化。在损伤侧 DRG内 ,5 -HT1 A受体 m RNA的表达水平于 1d后开始增高 ,4d时达高峰 ,随后开始下降 ,但仍维持较高的表达水平 ;而损伤对侧 DRG内的 5 -HT1 A受体 m RNA的表达没有变化。上述结果提示 5 -HT1 A受体亚型可能在脊髓及外周伤害性信息的传递和调节中发挥着重要作用 ,本研究的结果为进一步了解 5 -HT1 A受体在神经病理性痛中的作用机制提供了依据。     

不同时间点静脉移植嗅鞘细胞修复脊髓损伤

背景:嗅鞘细胞具有促进轴突再生、为受伤的宿主细胞提供营养支持以及调节炎症反应的能力,是修复脊髓损伤具有潜力的细胞。目的:探讨通过静脉移植嗅鞘细胞治疗脊髓损伤的最佳移植时间窗。方法:SPF雄性SD大鼠30只,采用脊髓半横断建立大鼠脊髓损伤模型,并随机分为5组:脊髓损伤后注射嗅鞘细胞1 d移植组、3 d移植组、7 d移植组、10 d移植组及PBS对照组。应用荧光量子点标记嗅鞘细胞;分别于1,3,7,10 d时间点通过尾静脉移植应用量子点标记的嗅鞘细胞;PBS对照组脊髓损伤后注射PBS。注射后1 d取损伤处的脊髓;应用小动物成像仪测定不同时间点转移到损伤处荧光的数值,通过荧光的强度衡量转移到损伤处细胞的量;应用嗅鞘细胞Anti-p75 NGF Receptor抗体做损伤处脊髓的免疫组织化学。实验方案经宁夏医科大学动物实验伦理委员会批准(编号:2017-073)。结果与结论:①荧光量子点可以标记嗅鞘细胞;②荧光测定结果与免疫组织化学染色结果:1,3,7,10 d时间点通过尾静脉移植的嗅鞘细胞均有细胞转移到损伤处,7 d移植的嗅鞘细胞转移到损伤处的最多;③结果说明,脊髓损伤不同时间点注射的嗅鞘细胞均可以转移到脊髓损伤处,损伤后7 d移植的嗅鞘细胞转移到损伤处的细胞数量最多,可以作为移植的最佳时间窗。     

Increased [Met]enkephalin and decreased substance P in spinal cord following thermal injury to one limb.

Thermal injury to one hind limb of rats was induced by immersion into water at 62 degrees C. Both a mild (15 s) or severe (30 s) lesion caused inflammation of the limb when observed 24 h later; but at this time the animals used the injured limb when they walked. Animals with a severe lesion of the injured limb subsequently withdrew it from use when walking. Limb withdrawal did not occur following a mild lesion. At 24 h following the lesion, lumbar spinal cord levels of [Met]enkephalin, as measured by radioimmunoassay, were elevated (70%) bilaterally in both hemisegments, ipsi- and contralateral to the lesion. At seven days following either mild or severe hind limb lesion [Met]enkephalin levels were elevated only in the ipsilateral lumbar hemisegment. At that time no changes in thoracic [Met]enkephalin levels were observed. Substance P levels were decreased (20-25%) bilaterally in the lumbar cord 24 h following a severe limb lesion, but no change was observed at seven days in any cord segment following a mild or severe lesion. Changes in spinal cord [Met]enkephalin content occur in response to thermal injury to one hind limb. However, the changes do not appear to be related to the withdrawal of the damaged limb from use following a severe lesion. Peptide changes in the spinal cord may reflect pain or injury to the damaged limb following a thermal lesion. In contrast, limb withdrawal may be a physiological rest mechanism related to altered basal ganglia peptide function.     

Up-regulation of GAP-43 and growth of axons in rat spinal cord after compression injury

Summary The growth-associated protein-43 (GAP-43) is an axonal phosphoprotein which is expressed at high levels during development and is reinduced by regeneration in the PNS. Consequently it is believed to be a key molecule in the regulation of axonal growth. However, injury to the CNS does not result in significant regeneration and this has been suggested to correlate with a failure of central neurons to up-regulate GAP-43 after axotomy. We have examined a model of spinal cord injury which is unique in two respects; first dural integrity is maintained by compression of the cord with smooth forceps (thus excluding connective tissue elements) and, secondly, considerable axonal growth has been reported through the resulting lesion. Our previous studies have shown that GAP-43 is extensively distributed in the rat spinal cord (see accompanying paper), but here we have used anti-GAP-43 antiserum at a dilution which did not yield any immunostaining in normal cord. However, supranormal levels of GAP-43 were detected in cell bodies and axons around the lesion within four days of compression injury. Double immunostaining with the RT97 monoclonal antibody indicated that a small subpopulation of neurons local to the site of compression were axotomized and expressed GAP-43 and phosphorylated neurofilament epitopes in their cell bodies. Although damage to long axon tracts was extensive, there was no evidence of regeneration in white matter. On the other hand cavities which formed in grey matter provided an environment for axonal elongation. Immunolabelling with markers for astrocytes and endothelial cells was used to evaluate the interaction of elongating axons with endogenous CNS cell types. Sprouting axons, identified by the presence of elevated levels of GAP-43, did not appear to grow in contact with astrocytes but preliminary evidence suggested that newly formed capillaries provided an appropriate substrate.     

神经生长相关蛋白GAP-43在脊髓损伤后不同时段的表达

目的探讨成年大鼠脊髓损伤后不同时段神经生长相关蛋白GAP-43表达的改变及其在脊髓损伤修复中的意义。方法应用改良的Allen’s法和数字化脊髓损伤模型制备仪建立大鼠脊髓损伤模型,用免疫组织化学方法检测脊髓在损伤后不同时段GAP-43的表达,分析免疫阳性细胞数和细胞的积分光密度值,资料用q检验进行统计分析。结果GAP-43表达于脊髓神经元胞浆及突起中,在前角运动神经元中更为明显,损伤后一周内免疫反应逐渐增强,损伤后第5天积分光密度值（10D）达到高峰（P〈0．01）,2周后明显下调（P〈0．05）。结论脊髓损伤可能诱导损伤区GAP-43表达,在损伤后7d左右表达高峰期出现,提示其可能参与了脊髓损伤神经的生长修复过程。     

Neurologic recovery according to early magnetic resonance imaging findings in traumatic cervical spinal cord injuries

The aim of this study was to determine the usefulness of early magnetic resonance imaging findings in predicting neurologic recovery at or below the injured level in traumatic cervical spinal cord injuries. Thirty patients with traumatic cervical spinal cord injuries were included. All of the patients received a magnetic resonance imaging and a neurologic examination in the emergency room, within 7 days of injury and at 6 months following the injury. To quantify neurologic recovery below the injured level, we modified clinical scales, particularly the motor ratio and the sensory ratio. We used the neurologic level to quantify recovery around the injured level. We assessed neurologic recovery according to MRI patterns and lesion extents. The pure hemorrhagic MRI pattern was not observed. In edematous and mixed types, the improvement of neurologic levels was not significantly different. The motor ratio and sensory ratio improved significantly more in edematous type patients than in mixed type patients. Based on MRI lesion extent, the improvement of neurologic levels was not significantly different, and motor ratio and sensory ratio improved significantly more in those with one or two segments involved than in those with more than two segments involved. In conclusion, early MRI pattern and lesion extent after traumatic cervical spinal cord injury may provide important information to help predict neurologic recovery, especially below the injured level.     

Embryonic stem cells inhibit expression of erythropoietin in the injured spinal cord

Recent observations have demonstrated neuroprotective role of erythropoietin (Epo) and Epo receptor in the central nervous system. Here we examined Epo function in the murine spinal cord after transplantation of pluripotent mouse embryonic stem (ES) cells pre-differentiated towards neuronal type following spinal cord injury. Expression of Epo was measured at both mRNA and protein levels in the ES cells as well as in the spinal cords after 1 and 7 days. Our data demonstrated that expression of Epo mRNA, as well as its protein content, in ES cells was significantly decreased after differentiation procedure. In the spinal cords, analysis showed that Epo mRNA level was significantly decreased after 1 day of ES cell injections in comparison to media-injected control. Epo protein level detected by Western blot was diminished as well. Examination of Epo production in the injured spinal cords after media or ES cells injections by indirect immunofluorescence showed increased Epo-immunopositive staining after media injections 1 day after injection. In contrast, ES cell transplantation did not induce Epo expression. Seven days after ES cell injections, Epo-immunopositive cells’ distribution in the ipsilateral side was not changed, while the intensity of immunostaining on the contralateral side was increased, approaching levels in control media-injected tissues. Our data let us to presume that previously described immediate positive effects of ES cells injected into the injured zone of spinal cord are not based on Epo, but on other factors or hormones, which should be elucidated further.