Potential role of hippocampal neurogenesis in spinal cord injury induced post-trauma depression

It has been reported both in clinic and rodent models that beyond spinal cord injury directly induced symptoms, such as paralysis, neuropathic pain, bladder/bowel dysfunction, and loss of sexual function, there are a variety of secondary complications, including memory loss, cognitive decline, depression, and Alzheimer's disease. The largescale longitudinal population-based studies indicate that post-trauma depression is highly prevalent in spinal cord injury patients. Yet, few basic studies have been conducted to address the potential molecular mechanisms. One of possible factors underlying the depression is the reduction of adult hippocampal neurogenesis which may come from less physical activity, social isolation, chronic pain, and elevated neuroinflammation after spinal cord injury. However, there is no clear consensus yet. In this review, we will first summarize the alteration of hippocampal neurogenesis post-spinal cord injury. Then, we will discuss possible mechanisms underlie this important spinal cord injury consequence. Finally, we will outline the potential therapeutic options aimed at enhancing hippocampal neurogenesis to ameliorate depression.

Inhibition of LncRNA Vof-16 expression promotes nerve regeneration and functional recovery after spinal cord injury

Our previous RNA sequencing study showed that the long non-coding RNA ischemia-related factor Vof-16(lncRNA Vof-16)was upregulated after spinal cord injury,but its precise role in spinal cord injury remains unclear.Bioinformatics predictions have indicated that lncRNA Vof-16 may participate in the pathophysiological processes of inflammation and apoptosis.PC12 cells were transfected with a pHBLV-U6-MCS-CMV-ZsGreen-PGK-PURO vector to express an lncRNA Vof-16 knockdown lentivirus and a pHLV-CMVIE-ZsGree-Puro vector to express an lncRNA Vof-16 overexpression lentivirus.The overexpression of lncRNA Vof-16 inhibited PC12 cell survival,proliferation,migration,and neurite extension,whereas lncRNA Vof-16 knockdown lentiviral vector resulted in the opposite effects in PC12 cells.Western blot assay results showed that the overexpression of lncRNA Vof-16 increased the protein expression levels of interleukin 6,tumor necrosis factor-α,and Caspase-3 and decreased Bcl-2 expression levels in PC12 cells.Furthermore,we established rat models of spinal cord injury using the complete transection at T10.Spinal cord injury model rats were injected with the lncRNA Vof-16 knockdown or overexpression lentiviral vectors immediately after injury.At 7 days after spinal cord injury,rats treated with lncRNA Vof-16 knockdown displayed increased neuronal survival and enhanced axonal extension.At 8 weeks after spinal cord injury,rats treated with the lncRNA Vof-16 knockdown lentiviral vector displayed improved neurological function in the hind limb.Notably,lncRNA Vof-16 knockdown injection increased Bcl-2 expression and decreased tumor necrosis factor-αand Caspase-3 expression in treated animals.Rats treated with the lncRNA Vof-16 overexpression lentiviral vector displayed opposite trends.These findings suggested that lncRNA Vof-16 is associated with the regulation of inflammation and apoptosis.The inhibition of lncRNA Vof-16 may be useful for promoting nerve regeneration and functional recovery after spinal cord injury.The experiments were approved by the Institutional Animal Care and Use Committee of Guangdong Medical University,China.

A core scientific problem in the treatment of central nervous system diseases:newborn neurons

It has long been asserted that failure to recover from central nervous system diseases is due to the system's intricate structure and the regenerative incapacity of adult neurons.Yet over recent decades,numerous studies have established that endogenous neurogenesis occurs in the adult central nervous system,including humans'.This has challenged the long-held scientific consensus that the number of adult neurons remains constant,and that new central nervous system neurons cannot be created or renewed.Herein,we present a comprehensive overview of the alterations and regulatory mechanisms of endogenous neurogenesis following central nervous system injury,and describe novel treatment strategies that to rget endogenous neurogenesis and newborn neurons in the treatment of central nervous system injury.Central nervous system injury frequently results in alterations of endogenous neurogenesis,encompassing the activation,proliferation,ectopic migration,diffe rentiation,and functional integration of endogenous neural stem cells.Because of the unfavorable local microenvironment,most activated neural stem cells diffe rentiate into glial cells rather than neurons.Consequently,the injury-induced endogenous neurogenesis response is inadequate for repairing impaired neural function.Scientists have attempted to enhance endogenous neurogenesis using various strategies,including using neurotrophic factors,bioactive materials,and cell reprogramming techniques.Used alone or in combination,these therapeutic strategies can promote targeted migration of neural stem cells to an injured area,ensure their survival and diffe rentiation into mature functional neurons,and facilitate their integration into the neural circuit.Thus can integration re plenish lost neurons after central nervous system injury,by improving the local microenvironment.By regulating each phase of endogenous neurogenesis,endogenous neural stem cells can be harnessed to promote effective regeneration of newborn neurons.This offers a novel approach for treating central nervous system injury.

Reducing host aldose reductase activity promotes neuronal differentiation of transplanted neural stem cells at spinal cord injury sites and facilitates locomotion recovery

Neural stem cell(NSC)transplantation is a promising strategy for replacing lost neurons following spinal cord injury.However,the survival and differentiation of transplanted NSCs is limited,possibly owing to the neurotoxic inflammatory microenvironment.Because of the important role of glucose metabolism in M1/M2 polarization of microglia/macrophages,we hypothesized that altering the phenotype of microglia/macrophages by regulating the activity of aldose reductase(AR),a key enzyme in the polyol pathway of glucose metabolism,would provide a more beneficial microenvironment for NSC survival and differentiation.Here,we reveal that inhibition of host AR promoted the polarization of microglia/macrophages toward the M2 phenotype in lesioned spinal cord injuries.M2 macrophages promoted the differentiation of NSCs into neurons in vitro.Transplantation of NSCs into injured spinal cords either deficient in AR or treated with the AR inhibitor sorbinil promoted the survival and neuronal differentiation of NSCs at the injured spinal cord site and contributed to locomotor functional recovery.Our findings suggest that inhibition of host AR activity is beneficial in enhancing the survival and neuronal differentiation of transplanted NSCs and shows potential as a treatment of spinal cord injury.

Crocetin Potentiates Neurite Growth in Hippocampal Neurons and Facilitates Functional Recovery in Rats with Spinal Cord Injury

Crocetin is an ingredient of traditional Chinese medicine and has therapeutic potential in various diseases due to its pharmacological properties, such as neuroprotection, anti-oxidative stress, and anti-inflammation. These properties might benefit the treatment of spinal cord injury.In the present study, we tested the effect of crocetin on neurite growth and sensorimotor dysfunction in a rat model of spinal cord injury. We evaluated the viability of cultured hippocampal neurons with tetrazolium dye and lactate dehydrogenase assays, visualized neurites and axons with antibody staining, and monitored motor and sensorimotor functions in rats with spinal cord injury using the Basso,Beattie, and Bresnahan assay and the contact plantar placement test, respectively, and measured cytokine expression using enzyme-linked immuno-absorbent assays.We found that crocetin（1） did not alter the viability of cultured hippocampal neurons;（2） accelerated neurite growth with preference for the longest process in individual hippocampal neurons;（3） reversed the inhibition of neurite growth by chondroitin sulfate proteoglycan and Nogo A;（4） facilitated the recovery of motor and sensorimotor functions after spinal cord injury; and（5） did not inhibit pro-inflammatory responses, but restored the innervation of the descending 5-HT system in injured spinalcord. Crocetin promotes neurite growth and facilitates the recovery of motor and sensorimotor functions after spinal cord injury, likely through repairing neuronal connections.

脊髓损伤小鼠中甘草苷通过抑制MAPK通路抑制炎症和神经元凋亡

目的 研究甘草苷对脊髓损伤小鼠中炎症和神经元凋亡的影响。方法 将48只C57BL/6小鼠随机均分为假手术组(Sham组)、脊髓损伤模型组(SCI组)、低剂量甘草苷组(LQ-L组)、高剂量甘草苷组(LQ-H组),每组12只。采用脊髓打击器撞击脊髓建立脊髓损伤模型,LQ-L组和LQ-H组分别予以低剂量(30 mg/kg)和高剂量(60 mg/kg)甘草苷灌胃。采用后肢运动功能评分(BMS)评估小鼠运动功能。取脊髓组织,HE染色观察病变面积,比色法检测髓过氧化物酶活性,TUNEL检测细胞凋亡,Nissl染色观察神经元丢失,免疫荧光双染检测caspase 3阳性神经元数量,Western blotting检测MAPK通路蛋白表达。结果 脊髓损伤明显降低了小鼠运动功能,促进了脊髓炎症、病变面积、神经元凋亡及p-ERK、p-p38 MAPK、p-JNK蛋白表达(P <0.05)。LQ-H组术后第14、21天,脊髓损伤小鼠运动功能明显提高(P <0.05)。LQ-L组和LQ-H组脊髓炎症、病变面积、神经元凋亡及p-ERK、p-p38 MAPK、p-JNK蛋白表达均明显抑制(P <0.05)。LQ-H组与LQ-L组相比,在抑制炎症、病变面积、神经元凋亡、p-ERK和p-p38 MAPK蛋白表达方面效果更明显(P <0.05)。结论 甘草苷可能通过抑制MAPK通路抑制炎症和神经元凋亡,减轻小鼠脊髓损伤。

The protocadherin alpha cluster is required for axon extension and myelination in the developing central nervous system

In adult mammals, axon regeneration after central nervous system injury is very poor, resulting in persistent functional loss. Enhancing the ability of axonal outgrowth may be a potential treatment strategy because mature neurons of the adult central nervous system may retain the intrinsic ability to regrow axons after injury. The protocadherin （Pcdh） clusters are thought to function in neuronal morphogenesis and in the assembly of neural circuitry in the brain. We cultured primary hippocampal neurons from E17.5 Pcdhα deletion （del-α） mouse embryos. After culture for 1 day, axon length was obviously shorter in del-α neurons compared with wild-type neurons. RNA sequencing of hippocampal E17.5 RNA showed that expression levels of BDNF, Fmod, Nrp2, OGN, and Sema3d, which are associated with axon extension, were significantly down-regulated in the absence of the Pcdhα gene cluster. Using transmission electron microscopy, the ratio of myelinated nerve fibers in the axons of del-α hippocampal neurons was significantly decreased; myelin sheaths of P21 Pcdhα-del mice showed lamellar disorder, discrete appearance, and vacuoles. These results indicate that the Pcdhα cluster can promote the growth and myelination of axons in the neurodevelopmental stage.

中枢神经系统与周围神经系统发育和损伤过程中微管动态性的差异比较

目的:通过比较微管蛋白的酪氨酸化、去酪氨酸化水平,分析中枢神经和周围神经系统神经元发育和损伤后微管动态变化。方法:分离培养Sprague-Dawley(SD)大鼠孕18 d(E18)胎鼠的背根神经节神经元和海马神经元,采用免疫细胞荧光化学方法检测不同修饰微管蛋白的表达和定位,对培养的神经元进行划伤,采用活细胞拍摄对神经元胞体及轴突生长进行分析比较。提取SD大鼠生后发育不同时间点的坐骨神经和脊髓组织,同时建立SD大鼠的脊髓挫伤和坐骨神经夹伤模型,于术后不同时间提取蛋白,通过Western Blot方法检测不同修饰(酪氨酸化、去酪氨酸化)的微管蛋白表达情况。结果:免疫细胞化学结果显示,与神经元种植1 d相比,在3 d时,背根神经节神经元,酪氨酸化、去酪氨酸化微管蛋白均维持较高水平,而海马神经元中酪氨酸化微管蛋白表达较低;活细胞摄像观察显示,背根神经节神经元和海马神经元在体外发育和损伤再生过程中轴突的平均生长速率差异无统计学意义,但背根神经节神经元胞体运动速率显著高于海马神经元胞体。中枢神经和周围神经发育过程中,坐骨神经组织维持较高的酪氨酸化微管蛋白水平,而在脊髓组织中酪氨酸化微管蛋白的表达逐步下降;在神经损伤后,酪氨酸化微管蛋白在坐骨神经组织中表达显著高于脊髓酪氨酸化微管蛋白。结论:与中枢神经相比,周围神经在发育和损伤后酪氨酸化修饰微管蛋白水平均高于中枢神经,提示周围神经具有更强的微管动态性。

X线照射治疗脊髓损伤大鼠的效果及其可能机制

目的分析X线照射治疗脊髓损伤(SCI)大鼠的效果,并探讨其可能的作用机制。方法将75只雌性SD大鼠随机分为假手术组(Sham组)、SCI组、SCI+2 Gy组、SCI+10 Gy组、SCI+20 Gy组,每组15只。除Sham组外,其他组均采用Allen法建立SCI模型。术后2 h,给予SCI+2 Gy组、SCI+10 Gy组和SCI+20 Gy组大鼠相应剂量的X线单次照射治疗。于术前及术后第1天、第14天,采用巴索-贝蒂-布雷斯纳汉(BBB)量表和斜板试验评估大鼠运动功能的情况;术后第14天,取脊髓组织观察空腔面积比例和尼氏小体所占的面积比例,采用免疫组织化学染色和蛋白免疫印迹法检测髓鞘碱性蛋白(MBP)、肿瘤坏死因子α(TNF-α)、白细胞介素1β(IL-1β)、胶质纤维酸性蛋白(GFAP)、波形蛋白(Vimentin)的表达情况。结果(1)与Sham组相比,其他组大鼠术后各时间点的BBB评分、最大倾斜度降低或减小,术后第14天的脊髓空腔面积比例增大,而尼氏小体所占的面积比例降低(均P<0.05);术后第14天,SCI组、SCI+2 Gy组、SCI+20 Gy组、SCI+10 Gy组大鼠的BBB评分和最大倾斜度依次增加,脊髓空腔面积比例依次减小,而尼氏小体所占面积比例依次增加(均P<0.05)。(2)术后第14天,与Sham组相比,其他组大鼠脊髓组织中MBP的相对表达量均降低,TNF-α、IL-1β、GFAP、Vimentin的相对表达量均增加(均P<0.05);SCI组、SCI+2 Gy组、SCI+20 Gy组、SCI+10 Gy组大鼠脊髓组织中MBP相对表达量依次升高、TNF-α、IL-1β、GFAP、Vimentin的相对表达量均依次降低(均P<0.05)。结论X线照射治疗可有效地改善SCI大鼠的神经功能,其机制可能为通过抑制炎症和胶质瘢痕形成为神经元存活和髓鞘再生提供有利的微环境。