Clock gene Per1 regulates the production of CCL2 and interleukin-6 through p38, JNK1 and NF-κB activation in spinal astrocytes

It has been previously reported that spinal clock genes controlled under circadian rhythm contribute to the regulation of astrocytic function, which in turn is involved in diverse processes such as nociceptive transduction and the induction of inflammation. However, how clock genes expressed in spinal cord astrocytes are associated with the modulation of the inflammatory response is poorly understood. In the current study, the role of Period1 (Per1), one of clock genes, in the expression of chemokine (C–C motif) ligand 2 (CCL2) and interleukin-6 (IL-6), which are typical pro-inflammatory mediators produced by spinal astrocytes, was investigated. It was found that the knockdown of Per1 by using RNA interference led to a significant increase of the expression of CCL2 and IL-6 in cultured rat spinal astrocytes. Moreover, the silencing of the Per1 gene also increased the phosphorylation of p38, c-Jun N-terminal kinase (JNK) 1 and IκBα, and led to the translocation of p65 from the cytosol to the nucleus. The induction of CCL2 and IL-6 was significantly inhibited by treatment with the inhibitors of p38, JNK, and NF-κB. By contrast, the overexpression of PER1 by transfection vector significantly blocked the expression of CCL2 and IL-6, and the activation of p38, JNK, and NF-κB. Together, these results suggest that down-regulation of Per1 induced the phosphorylation of p38 and JNK1 and the subsequent activation of NF-κB, and that these events contribute to neuroinflammatory state in the spinal cord via the induction of the release of inflammatory mediators.     

Endoplasmic reticulum stress transducer old astrocyte specifically induced substance contributes to astrogliosis after spinal cord injury

Old astrocyte specifically induced substance(OASIS) is an endoplasmic reticulum(ER) stress transducer specifically expressed in astrocytes and osteoblasts. OASIS regulates the differentiation of neural precursor cells into astrocytes in the central nervous system. This study aimed to elucidate the involvement of ER stress responses stimulated via OASIS in astrogliosis following spinal cord injury. In a mouse model of spinal cord contusion injury, OASIS m RNA and protein expression were evaluated at days 7 and 14. A significant increase in OASIS m RNA on day 7 and an increase in protein on days 7 and 14 was observed in injured spinal cords. Immunostaining on day 7 revealed co-localization of OASIS and astrocytes in the periphery of the injury site. Furthermore, anti-OASIS small interfering RNA(si RNA) was injected at the injury sites on day 5 to elucidate the function of OASIS. Treatment with anti-OASIS si RNA caused a significant decrease in OASIS m RNA on day 7 and protein on days 7 and 14, and was associated with the inhibition of astrogliosis and hindlimb motor function recovery. Results of our study show that OASIS expression synchronizes with astrogliosis and is functionally associated with astrogliosis after spinal cord injury.     

Differential expression of cell fate determinants in neurons and glial cells of adult mouse spinal cord after compression injury

Cellular responses after spinal cord injury include activation of astrocytes, degeneration of neurons and oligodendrocytes, and reactions of the ependymal layer and meningeal cells. Because it has been suggested that tissue repair partially recapitulates morphogenesis, we have investigated the expression of several developmentally prominent molecules after spinal cord injury of adult mice where neurogenesis does not occur after injury. Cell fate determinants Numb, Notch-1, Shh and BMPs are abundantly expressed during development but mostly decline in the adult. In the present study, we investigated whether these genes are triggered by spinal cord injury as a sign of attempted recapitulation of development. Expression of Numb, Notch, Shh, BMP2/4 and Msx1/2 was analysed in the adult mouse spinal cord after compression injury by in situ hybridization up to 1 month after injury. The mRNA expression levels of Notch-1, Numb, Shh, BMP4 and Msx2 increased in the grey matter and/or white matter and in the ependyma rostral and caudal to the lesion site after injury. However, BMP2 and Msx1 were not up-regulated. Combining immunohistochemistry of cell type-specific markers with in situ hybridization we found that all the up-regulated genes were expressed in neurons. Moreover, Numb, BMP4 and Msx2 were also expressed by GFAP-positive astrocytes, while Shh was expressed by MBP-positive oligodendrocytes. In conclusion, the cell fate determinants Notch-1, Numb, Shh, BMP4 and Msx2 are expressed in neurons and/or glial cells after injury in a time-dependent manner, suggesting that these genes reflect to some extent an endogenous self-repair potential by recapitulating some features of development.     

Induction of type IV collagen and other basement-membrane-associated proteins after spinal cord injury of the adult rat may participate in formation of the glial scar.

We investigated the spatial and temporal expression of basement-membrane-forming and neurite-outgrowth-supporting matrix proteins after a unilateral dorsal root injury combined with a collagen I/laminin-1 graft and a stab wound lesion to the dorsal horn of the adult rat spinal cord. Ten days after injury, the gamma1 laminin was induced in the reactive glia. At this early stage, the glial cells failed to express type IV collagen and the alpha1 laminin. One month after injury, reactive astrocytes in the dorsal horn of the lesioned side expressed gamma1 laminin, type IV collagen, and the alpha1 laminin whereas astrocytes of the normal spinal cord or the uninjured contralateral dorsal horn were negative. Both astrocytes and neurons of the ipsilateral ventral horn were induced to express laminin-1 and gamma1 laminin. Astrocytes of the ipsilateral ventral horn also expressed type IV collagen. Simultaneously with the changes in expression of the extracellular matrix proteins, the expression pattern of basic fibroblast growth factor (FGF-2) was markedly altered after spinal cord injury. In normal and contralateral spinal cord, FGF-2 was expressed in nerve fibers, but its expression changed from neuronal into glial in the ipsilateral spinal cord within 1 month after injury. Four months after injury, expression of both type IV collagen and the alpha1 laminin had declined, but the astrocytes at the injury site continued expressing the gamma1 laminin. Cultured astrocytes were negative for type IV collagen, but several cytokines, including IL-1beta and TGFbeta1, induced expression of type IV collagen in the astrocytes. These factors also increased deposition of type IV collagen matrix in the glial cultures. These results indicate that type IV collagen and the alpha1 laminin are induced in reactive astrocytes after spinal cord injury in vivo. Induction of type IV collagen in astrocytes in vitro by cytokines indicates that blood-borne or local factors at the injury site may induce the spinal cord glial expression of type IV collagen in vivo. Simultaneous expression of laminin-1 and alpha1 laminin with type IV collagen is known to lead to production of basement membranes. This may hamper the neurite-outgrowth-promoting potential of the gamma1 laminin by initiating formation of the glial scar.     

Key genes expressed in different stages of spinal cord ischemia/reperfusion injury ischemia/reperfusion injury

The temporal expression of microRNA after spinal cord ischemia/reperfusion injury is not yet fully understood.In the present study,we established a model of spinal cord ischemia in Sprague-Dawley rats by clamping the abdominal aorta for 90 minutes,before allowing reperfusion for 24 or 48 hours.A sham-operated group underwent surgery but the aorta was not clamped.The damaged spinal cord was removed for hematoxylin-eosin staining and RNA extraction.Neuronal degeneration and tissue edema were the most severe in the 24-hour reperfusion group,and milder in the 48-hour reperfusion group.RNA amplification,labeling,and hybridization were used to obtain the microRNA expression profiles of each group.Bioinformatics analysis confirmed four differentially expressed microRNAs(miR-22-3p,miR-743b-3p,miR-201-5p and miR-144-5p) and their common target genes(Tmem69 and CxcllO).Compared with the sham group,miR-22-3p was continuously upregulated in all three ischemia groups but was highest in the group with no reperfusion,whereas miR-743b-3p,miR-201-5p and miR-144-5p were downregulated in the three ischemia groups.We have successfully identified the key genes expressed at different stages of spinal cord ischemia/reperfusion injury,which provide a reference for future investigations into the mechanism of spinal cord injury.     

Differentiation of endogenous neural precursors following spinal cord injury in adult rats☆

BACKGROUND： Studies have shown that cell death can activate proliferation of endogenous neural stem cells and promote newly generated cells to migrate to a lesion site.
OBJECTIVE： To observe regeneration and differentiation of neural cells following spinal cord injury in adult rats and to quantitatively analyze the newly differentiated cells.
DESIGN, TIME AND SETTING： A cell biology experiment was performed at the Institute of Orthopedics and Medical Experimental Center, Lanzhou University, between August 2005 and October 2007.
MATERIALS： Fifty adult, Wistar rats of both sexes; 5-bromodeoxyuridine （BrdU, Sigma, USA）; antibodies against neuron-specific enolase, glial fibrillary acidic protein, and myelin basic protein （Chemicon, USA）.
METHODS： Twenty-five rats were assigned to the spinal cord injury group and received a spinal cord contusion injury. Materials were obtained at day 1, 3, 7, 15, and 29 after injury, with 5 rats for each time point. Twenty-five rats were sham-treated by removing the lamina of the vertebral arch without performing a contusion.
MAIN OUTCOME MEASURES： The phenotype of BrdU-labeled cells, i.e., expression and distribution of surface markers for neurons （neuron-specific enolase）, astrocytes （glial fibrillary acidic protein）, and oligodendrocytes （myelin basic protein）, were identified with immunofluorescence double-labeling. Confocal microscopy was used to detect double-labeled cells by immunofluorescence. Quantitative analysis of newly generated cells was performed with stereological counting methods.
RESULTS： There was significant cell production and differentiation after adult rat spinal cord injury. The quantity of newly-generated BrdU-labeled cells in the spinal cord lesion was 75-fold greater than in the corresponding area of control animals. Endogenous neural precursor cells differentiated into astrocytes and oligodendrocytes, however spontaneous neuronal differentiation was not detected. Between 7 and 29 d after spinal cord injury, newl     

Expression and localization of absent in melanoma 2 in the injured spinal cord

In traumatic brain injury, absent in melanoma 2(AIM2) has been demonstrated to be involved in pyroptotic neuronal cell death. Although the pathophysiological mechanism of spinal cord injury is similar to that of brain injury, the expression and cellular localization of AIM2 after spinal cord injury is still not very clear. In the present study, we used a rat model of T9 spinal cord contusive injury, produced using the weight drop method. The rats were randomly divided into 1-hour, 6-hour, 1-day, 3-day and 6-day(post-injury time points) groups. Sham-operated rats only received laminectomy at T9 without contusive injury. Western blot assay revealed that the expression levels of AIM2 were not significantly different among the 1-hour, 6-hour and 1-day groups. The expression levels of AIM2 were markedly higher in the 1-hour, 6-hour and 1-day groups compared with the sham, 3-day and 7-day groups. Double immunofluorescence staining demonstrated that AIM2 was expressed by NeuN+(neurons), GFAP+(astrocytes), CNPase+(oligodendrocytes) and CD11 b+(microglia) cells in the sham-operated spinal cord. In rats with spinal cord injury, AIM2 was also found in CD45+(leukocytes) and CD68+(activated microglia/macrophages) cells in the spinal cord at all time points. These findings indicate that AIM2 is mainly expressed in neurons, astrocytes, microglia and oligodendrocytes in the normal spinal cord, and that after spinal cord injury, its expression increases because of the infiltration of leukocytes and the activation of astrocytes and microglia/macrophages.     

Bioinformatic identification of key candidate genes and pathways in axon regeneration after spinal cord injury in zebrafish

Zebrafish and human genomes are highly homologous;however,despite this genomic similarity,adult zebrafish can achieve neuronal proliferation,regeneration and functional restoration within 6–8 weeks after spinal cord injury,whereas humans cannot.To analyze differentially expressed zebrafish genes between axon-regenerated neurons and axon-non-regenerated neurons after spinal cord injury,and to explore the key genes and pathways of axonal regeneration after spinal cord injury,microarray GSE56842 was analyzed using the online tool,GEO2R,in the Gene Expression Omnibus database.Gene ontology and protein-protein interaction networks were used to analyze the identified differentially expressed genes.Finally,we screened for genes and pathways that may play a role in spinal cord injury repair in zebrafish and mammals.A total of 636 differentially expressed genes were obtained,including 255 up-regulated and 381 down-regulated differentially expressed genes in axon-regenerated neurons.Gene Ontology and Kyoto Encyclopedia of Genes and Genomes enrichment results were also obtained.A protein-protein interaction network contained 480 node genes and 1976 node connections.We also obtained the 10 hub genes with the highest correlation and the two modules with the highest score.The results showed that spectrin may promote axonal regeneration after spinal cord injury in zebrafish.Transforming growth factor beta signaling may inhibit repair after spinal cord injury in zebrafish.Focal adhesion or tight junctions may play an important role in the migration and proliferation of some cells,such as Schwann cells or neural progenitor cells,after spinal cord injury in zebrafish.Bioinformatic analysis identified key candidate genes and pathways in axonal regeneration after spinal cord injury in zebrafish,providing targets for treatment of spinal cord injury in mammals.     

Key genes expressed in different stages of spinal cord ischemia/reperfusion injury

The temporal expression of microRNA atfer spinal cord ischemia/reperfusion injury is not yet fully understood. In the present study, we established a model of spinal cord ischemia in Sprague-Dawley rats by clamping the abdominal aorta for 90 minutes, before allowing reperfusion for 24 or 48 hours. A sham-operated group underwent surgery but the aorta was not clamped. The damaged spinal cord was removed for hematoxylin-eosin staining and RNA extraction. Neuronal degeneration and tissue edema were the most severe in the 24-hour reperfusion group, and milder in the 48-hour reperfusion group. RNA ampliifcation, labeling, and hybridization were used to obtain the microRNA expression proifles of each group. Bioinformatics analysis conifrmed four differentially expressed microRNAs (miR-22-3p, miR-743b-3p, miR-201-5p and miR-144-5p) and their common target genes (Tmem69 and Cxcl10). Compared with the sham group, miR-22-3p was continuously upregulated in all three ischemia groups but was highest in the group with no reperfusion, whereas miR-743b-3p, miR-201-5p and miR-144-5p were downregulated in the three ischemia groups. We have successfully identiifed the key genes expressed at different stages of spinal cord ischemia/reperfusion injury, which provide a reference for future investigations into the mechanism of spinal cord injury.     

Methotrexate combined with methylprednisolone for the recovery of motor function and differential gene expression in rats with spinal cord injury

Methylprednisolone is a commonly used drug for the treatment of spinal cord injury, but high doses of methylprednisolone can increase the incidence of infectious diseases. Methotrexate has anti-inflammatory activity and immunosuppressive effects, and can reduce in-flammation after spinal cord injury. To analyze gene expression changes and the molecular mechanism of methotrexate combined with methylprednisolone in the treatment of spinal cord injury, a rat model of spinal cord contusion was prepared using the PinPoint? preci-sion cortical impactor technique. Rats were injected with methylprednisolone 30 mg/kg 30 minutes after injury, and then subcutaneously injected with 0.3 mg/kg methotrexate 1 day after injury, once a day, for 2 weeks. TreadScan gait analysis found that at 4 and 8 weeks after injury, methotrexate combined with methylprednisolone significantly improved hind limb swing time, stride time, minimum longitudinal deviation, instant speed, footprint area and regularity index. Solexa high-throughput sequencing was used to analyze differential gene ex-pression. Compared with methylprednisolone alone, differential expression of 316 genes was detected in injured spinal cord treated with methotrexate and methylprednisolone. The 275 up-regulated genes were mainly related to nerve recovery, anti-oxidative, anti-inflammatory and anti-apoptotic functions, while 41 down-regulated genes were mainly related to proinflammatory and pro-apoptotic functions. These results indicate that methotrexate combined with methylprednisolone exhibited better effects on inhibiting the activity of inflammatory cytokines and enhancing antioxidant and anti-apoptotic effects and thereby produced stronger neuroprotective effects than methotrexate alone. The 316 differentially expressed genes play an important role in the above processes.     

Increased expression of the close homolog of the adhesion molecule L1 in different cell types over time after rat spinal cord contusion

The close homolog of the adhesion molecule L1 (CHL1) is important during CNS development, but a study with CHL1 knockout mice showed greater functional recovery after spinal cord injury (SCI) in its absence. We investigated CHL1 expression from 1 to 28 days after clinically relevant contusive SCI in Sprague-Dawley rats. Western blot analysis showed that CHL1 expression was significantly up-regulated at day 1 and further increased over 4 weeks after SCI. Immunohistochemistry of tissue sections showed that CHL1 in the intact spinal cord was expressed at low levels. By 1 day and through 4 weeks after SCI, CHL1 became highly expressed in NG2(+) cells. Hypertrophic GFAP(+) astrocytes also expressed CHL1 by 1 week after injury. The increase in CHL1 protein paralleled that of NG2 in the first week and GFAP between 1 and 4 weeks after injury. At 4 weeks, NG2(+) /CHL1(+) cells and GFAP(+) /CHL1(+) astrocytes were concentrated at the boundary between residual spinal cord tissue and the central lesion. NF200(+) spinal cord axons approached but did not penetrate this boundary. In contrast, CHL1(+) cells in the central lesion at 1 week and later colabeled with p75 and NG2 and were chronically associated with many NF200(+) axons, presumably axons that had sprouted in association with CHL1(+) Schwann cells infiltrating the cord after contusion. Thus, our study demonstrates up-regulation of CHL1 in multiple cell types and locations in a rat model of contusion injury and suggests that this molecule may be involved both in inhibition of axonal regeneration and in recovery processes after SCI.     

Differentiation of endogenous neural precursors following spinal cord injury in adult rats

BACKGROUND:Studies have shown that cell death can activate proliferation of endogenous neural stem cells and promote newly generated cells to migrate to a lesion site.OBJECTIVE:To observe regeneration and differentiation of neural cells following spinal cord injury in adult rats and to quantitatively analyze the newly differentiated cells.DESIGN,TIME AND SETTING:A cell biology experiment was performed at the Institute of Orthopedics and Medical Experimental Center,Lanzhou University.between August 2005 and October 2007.MATERIALS:Fifty adult,Wistar rats of both sexes;5-bromodeoxyuridine(BrdU,Sigma,USA);antibodies against neuron-specific enolase,glial fibrillary acidic protein,and myelin basic protein(Chemicon,USA).METHODS:Twenty-five rats were assigned to the spinal cord injury group and received a spinal cord contusion injury.Materials were obtained at day 1,3,7,15,and 29 after injury,with 5 rats for each time point.Twenty-five rats were sham-treated by removing the lamina of the vertebral arch without performing a contusion.MAIN OUTCOME MEASURES:The phenotype of BrdU-labeled cells,i.e.,expression and distribution of surface markers for neurons(neuron-specific enolase),astrocytes(glial fibrillary acidic protein),and oligodendrocytes(myelin basic protein),were identified with immunofluorescence double-labeling.Confocal microscopy was used to detect double-labeled cells by immunofluorescence.Quantitative analysis of newly generated cells was performed with stereological counting methods.RESULTS:There was significant cell production and differentiation after adult rat spinal cord injury.The quantity of newly-generated BrdU-labeled cells in the spinal cord lesion was 75-fold greater than in the corresponding area of control animals.Endogenous neural precursor cells differentiated into astrocytes and oligodendrocytes,however spontaneous neuronal difierentiation was not detected.Between 7 and 29 d after spinal cord injury,newly generated cells expressed increasingly more mature oligodendrocyte and astrocyte markers.CONCLUSION:Spinal cord injury is a direct inducer of regeneration and differentiation of neural cells.Endogenous neural precursor cells Can difierentiate into astrocytes and oligodendrocytes following adult rat spinal cord injury.     

Targeting astrocyte signaling for chronic pain

Clinical management of chronic pain after nerve injury (neuropathic pain) and tumor invasion (cancer pain) is a real challenge due to our limited understanding of the cellular mechanisms that initiate and maintain chronic pain. It has been increasingly recognized that glial cells, such as microglia and astrocytes in the CNS play an important role in the development and maintenance of chronic pain. Notably, astrocytes make very close contacts with synapses and astrocyte reaction after nerve injury, arthritis, and tumor growth is more persistent than microglial reaction, and displays a better correlation with chronic pain behaviors. Accumulating evidence indicates that activated astrocytes can release proinflammatory cytokines (e.g., interleukin [IL]-1β) and chemokines (e.g., monocyte chemoattractant protein-1 [MCP-1]/also called CCL2) in the spinal cord to enhance and prolong persistent pain states. IL-1β can powerfully modulate synaptic transmission in the spinal cord by enhancing excitatory synaptic transmission and suppressing inhibitory synaptic transmission. IL-1β activation (cleavage) in the spinal cord after nerve injury requires the matrix metalloprotease-2. In particular, nerve injury and inflammation activate the c-Jun N-terminal kinase in spinal astrocytes, leading to a substantial increase in the expression and release of MCP-1. The MCP-1 increases pain sensitivity via direct activation of NMDA receptors in dorsal horn neurons. Pharmacological inhibition of the IL-1β, c-Jun N-terminal kinase, MCP-1, or matrix metalloprotease-2 signaling via spinal administration has been shown to attenuate inflammatory, neuropathic, or cancer pain. Therefore, interventions in specific signaling pathways in astrocytes may offer new approaches for the management of chronic pain.     

成年大鼠脊髓损伤后损伤区血管变化及其与星形胶质细胞的关系

目的研究成年大鼠脊髓损伤后损伤区内血管的变化及其与星形胶质细胞的关系。方法通过单宁酸-氯化铁灌注，结合形态学与免疫组织化学方法，观察正常大鼠脊髓以及挤压损伤后0h、24h、72h．1周、2周、4周时的血管形态及其与星形胶质细胞的关系。结果正常脊髓血管形态清晰，可见胶质纤维酸性蛋白（GFAP）免疫反应阳性细胞突起附着于血管壁上；脊髓损伤后0h损伤区血管连续性中断，未见GFAP免疫反应阳性细胞；72h时损伤区出现血管；1周时损伤区内血管数目较多，可见GFAP免疫反应阳性细胞；2周时损伤区空洞形成，周围可见少量GFAP免疫反应阳性细胞附着于血管；4周时损伤区内围绕空洞的血管交错排列，与GFAP免疫反应阳性细胞突起形成广泛关联。结论脊髓损伤后72h内推测是治疗脊髓损伤后损伤区组织缺血的有效时间窗，损伤后星形胶质细胞参与了血管结构的恢复。     

RhoA, RhoB, RhoC, Rac1, Cdc42, and Tc10 mRNA levels in spinal cord, sensory ganglia, and corticospinal tract neurons and long-lasting specific changes following spinal cord injury

Inhibition of RhoA has been shown to enhance axonal regeneration following spinal cord injury. Here we mapped mRNA expression patterns of RhoA, B, and C, Rac1, Cdc42, and Tc10 in spinal cord, sensory ganglia, and sensorimotor cortex in uninjured rats, and following spinal cord injury or sham laminectomy. In the intact spinal cord, neurons displayed high levels of Rac1, Cdc42, and Tc10 mRNA hybridization signal. GFAP-immunoreactive astrocytes expressed primarily RhoB and Rac1, while oligodendrocyte-like cells expressed RhoA, Rac1, and Cdc42. Injury caused profound, long-lasting upregulation of RhoA, Rac1, Cdc42, and Tc10 mRNA in the spinal cord, while RhoB was modestly increased and RhoC did not change. GFAP-immunoreactive reactive astrocytes exhibited a dramatic increase of RhoA mRNA expression along with increases of Rac1 and Cdc42. Injury also led to elevation of RhoA, Cdc42, and Tc10 in neurons and modest increases of RhoA, Rac1, and Tc10 in oligodendrocyte-like cells. Laminectomy caused similar, but less pronounced alterations of investigated mRNA species. In dorsal root ganglia neuronal RhoA, Rac1, Cdc42, and Tc10 mRNA levels were increased similarly by spinal cord injury and sham surgery. The CST pyramidal cells expressed Tc10 mRNA and the CST itself was Tc10-immunoreactive. Tc10-immunoreactivity disappeared distal to injury. We conclude that there are gene-specific patterns of expression of the six different Rho-GTPases in normal spinal cord and dorsal root ganglia, and that specific changes of temporal and spatial expression patterns occur in response to spinal cord injury, suggesting different roles of these GTPases in the cellular sequelae of CNS injury.     

Upregulation of the HLH Id gene family in neural progenitors and glial cells of the rat spinal cord following contusion injury.

Spinal cord injury (SCI) leads to a complex sequence of cellular responses, including astrocyte activation, oligodendrocyte death, and ependymal cell proliferation. Inhibitors of DNA binding (Id1, Id2, Id3) belong to a helix-loop-helix (HLH) gene family. Id genes have been implicated in playing a vital role in the proliferation of many cell types, including astrocytes and myoblasts. In the present study, the expression of Id family members in spinal cord after contusion injury was investigated by in situ hybridization. Id1, Id2, and Id3 mRNA expression was upregulated 5 mm rostral and caudal to the lesion center, and reached maximal levels 3 days after SCI. In addition, cell populations expressing Id1, Id2, and Id3 mRNA were maximally increased 3 days after SCI. The increase in Id2 and Id3 mRNA expression and Id2 and Id3 mRNA+ cells was still observed at 8 days. The Id mRNA expressing cells were phenotyped by combining immunostaining of cell-specific markers with in situ hybridization. Glial fibrillary acidic protein (GFAP)+ astrocytes were found to express all three Id mRNA, whereas S-100alpha+ astrocytes only expressed high levels of Id2 and Id3 mRNA. Cells having a neural progenitor morphology and the marker nestin appeared after SCI and they expressed Id1, Id2, and Id3 mRNA. Interestingly, some Rip+ oligodendrocytes located in the areas close to the central canal expressed Id3 mRNA after injury. In conclusion, Id genes are upregulated in a time-dependent manner in astrocytes, oligodendrocytes, and neural progenitor subpopulations after SCI, suggesting that they play major roles in cellular responses following SCI.     

Transplantation of bone marrow mesenchymal stem cells reduces lesion volume and induces axonal regrowth of injured spinal cord

It has been demonstrated that transplantation of bone marrow mesenchymal stem cells (BMSCs) improves recovery of injured spinal cord in animal models. However, the mechanism of how BMSCs promote repair of injured spinal cord remains under investigation. The present study investigated the neural differentiation of BMSCs, the lesion volume and axonal regrowth of injured spinal cord after transplantation. Seven days after spinal cord injury, 3 × 10⁵ BMSCs or PBS (control) was delivered into the injury epicenter of the spinal cord. At 8 weeks after spinal cord injury, transplantation of BMSCs reduced the volume of cavity and increased spared white matter as compared to the control. BMSCs did not express the cell marker of neurons, astrocytes and oligodendrocytes in injured spinal cord. Transmission electron microscopic examination displayed an increase in the number of axons in BMSC rats. The effect of BMSCs on growth of neuronal process was further investigated by using a coculture system. The length and the number of neurites from spinal neurons significantly increased when they cocultured with BMSCs. PCR and immunochemical analysis showed that BMSCs expressed brain‐derived neurotrophic factor (BDNF) and glia cell line‐derived neurotrophic factor (GDNF). These findings demonstrate that transplantation of BMSCs reduces lesion volume and promotes axonal regrowth of injured spinal cord.