Effect of glial cells on remyelination after spinal cord injury

Remyelination plays a key role in functional recovery of axons after spinal cord injury.Glial cells are the most abundant cells in the central nervous system.When spinal cord injury occurs,many glial cells at the lesion site are immediately activated,and different cells differentially affect inflammatory reactions after injury.In this review,we aim to discuss the core role of oligodendrocyte precursor cells and crosstalk with the rest of glia and their subcategories in the remyelination process.Activated astrocytes influence proliferation,differentiation,and maturation of oligodendrocyte precursor cells,while activated microglia alter remyelination by regulating the inflammatory reaction after spinal cord injury.Understanding the interaction between oligodendrocyte precursor cells and the rest of glia is necessary when designing a therapeutic plan of remyelination after spinal cord injury.

Arsenic exposure and glutamate-induced gliotransmitter release from astrocytes

The present study used cultures of primary astrocytes, isolated from neonatal rats, to verify the hypothesis that arsenite-induced neurotoxicity can influence neuronal function by altering glutamate-induced gliotransmitter release. Primary astrocytes were exposed to 0, 2.5, 5, 10, 20 or 30 μM arsenite for 24 hours. Cell viability and morphological observations revealed that 5 μM arsenic exposure could induce cytotoxicity. Cells were then cultured in the presence of 0, 2.5, 5, or 10 μM arsenite for 24 hours and stimulated with 25 μM glutamate for 10 minutes. Results showed that [Ca2＋]i in astrocytes exposed to 5 and 10 μM arsenite was significantly increased and levels of D-serine, γ-aminobutyric acid and glycine in cultures exposed to 2.5-10 μM arsenite were also increased. However, glutamate levels in the media were significantly increased only after treatment with 10 μM arsenite. In conclusion, our findings suggest that arsenic exposure may affect glutamate-induced gliotransmitter release from astrocytes and further disturb neuronal function.

In vitro differentiation of human adipose-derived adult stromal cells into neuron-like cells in hippocampal astrocyte conditioned medium

BACKGROUND: At present, researches on differentiating from human adipose-derived adult stromal cells (hADASC) to neuron-like cells are focus on inducing by artificial-synthetic compound solution; however, hippocampal astrocyte conditioned medium (HCAM) can induce in vitro differentiation from hADASC to neuron-like cells is still unclear. OBJECTIVE: To observe whether HCAM can induce in vitro differentiation from hADASC to neuron-like cells. DESIGN: Randomized control study. SETTING: Department of Neurology, Taixing People's Hospital; Central Laboratory, North China Coal Medical College. MATERIALS: Donor of adipose tissue was donated by female volunteers suffering from caesarean section in the department of obstetrics & gynecology in our hospital and aged 20-35 years. Adipose tissue was collected from subcutaneous tissue of abdomen during the operation. In addition, 8 male newborn Wistar rats within 24 hours with average body mass of 20 g were provided by Animal Institute of Chinese Academy of Medical Sciences. Rabbit-anti-human Nestin polyclonal antibody, rabbit-anti-human glial fibriliary acidic protein (GFAP) polyclonal antibody, rabbit-anti-human neuro-specific enolase polyclonal antibody and mouse-anti-human microtubal associated protein 2 (MAP-2) polyclonal antibody were provided by Wuhan Boster Company. METHODS: The experiment was carried out in the Central Laboratory of North China Coal Medical College from October 2004 to June 2005. hADASC was cultured with HCAM and its growth and morphological changes were observed under inverted phase contrast microscope. Immunocytochemistry, immunofluorescence and Western blotting were used to evaluate the expressions of Nestin, which was a specific sign of nerve precursor, neuro-specific enolase and MAP-2, which was a specific sign of nerve cell, and GFAP, which was a specific sign of neuroglial cells. MAIN OUTCOME MEASURES: Nestin, which was a specific sign of nerve precursor, neuro-specific enolase and MAP-2, which was a specific sign of nerve cell, and GFAP, which was a specific sign of neuroglial cells. RESULTS: On the 3rd day of culture, partial hADASC started deformation from slender shuttle-shape cells to neuron-like cells. It suggested that cells stretched out apophysis, which were mainly double-pole or multiple-pole cells. Five days later, immunohistochemical detection suggested that expression of Nestin (10.5±0.037) was found out in cells; meanwhile, expressions of GFAP (38.4±0.052) and neuro-specific enolase (NSE) (15.7±0.023) were also found out in cells; however, expression of MAP-2 was not observed. Western blot indicated that, 5 days after effect of HCAM, Nestin was found out in hADASC; meanwhile, expressions of GFAP and neuro-specific enolase were also found out; however, expression of MAP-2 was not observed. CONCLUSION: HCAM can induce the differentiation from hADASC to neuron-like cells in vitro.

Protection of Salidroside on Primary Astrocytes from Cell Death by Attenuating Oxidative Stress

Objective To investigate whether salidroside（SAL） has protective and anti-oxidative effects on astrocytes. Methods Firstly, SAL was extracted from the roots of Rhodiola rosea with 70% ethanol and butanol to obtain crude phenylethyl alcohol glycosides which have been known as bioactive part of R. rosea; Secondly, WST-1 assay was carried out to assess the cell viability of astrocytes and cortical neurons under the treatment of the purified（〉 95%） SAL. Moreover, WST-1 assay was also used to evaluate the cytoprotective effects of SAL preventing astrocytes from staurosporine-induced cell death; Thirdly, we examined the spontaneous reactive oxygen species（ROS） and staurosporine-induced ROS generation in astrocytes in the absence or presence of SAL.Results SAL was observed to improve the astrocytes viability but not cortical neurons. In addition, SAL was able to ameliorate staurosporine-induced cell death. Moreover, SAL was able to attenuate the spontaneous ROS and staurosporine-induced ROS generation. Conclusion We here confirm that the anti-oxidative effect of SAL on primary astrocytes might be an important mechanism accounting for the cytoprotective effects from SAL.

An experimental study on astrocytes promoting production of neural stem cells derived from mouse embryonic stem cells

Background The production of neural stem cells （NSCs） derived from embryonic stem （ES） cells was usually very low according to previous studies, which was a major obstacle for meeting the needs of clinical application. This study aimed at investigating whether astrocytes could promote production of NSCs derived from ES cells in vitro.Methods Mouse ES cells line-D3 was used to differentiate into NSCs with astrocytes as inducing stromal cells by means of three-stage differentiation procedure. Another group without astrocytes served as control. The totipotency of ES cells was identified by observation of cells＇ morphology and formation of teratoma in severe combined immunodeficiency disease （SCID） mice. The quantity and purity of NSCs derived from ES cells were analyzed using clonogenic assay, immunohistochemical staining and flow cytometry assay. The plasticity of NSCs was detected by differentiating test. Octamer-binding transcription factor 4 （Oct-4） and nestin, the specific marker genes of ES cells and NSCs respectively, were detected continuously using reverse transcription- polymerase chain reaction （RT-PCR） method to monitor the process of cell differentiation.Results The ES cells of D3 line could maintain the ability of differentiating into cellular derivations of all three primary germ layers after continuous passage culture. At the end of two-stage of inducing process, 23.2±3.5 neurospheres per plate formed in astrocyte-induced group and only 0. 8±0.3 per plate in the control group （ elonogenic assay, P 〈 0.01 ）, and the ratio of nestin positive cells was （50. 2±2. 8） % in astrocyte-induced group and only （ 1.4±0. 5） % in the control group （flow cytometry, P 〈0. 01 ）. With the induction undergoing, the expression of Oct-4 gradually decreased and then disappeared, while the expression of nestin was increased step by step, and the ratio of nestin positive cells was up to 91.4% by the three-stage differentiation. The nestin positive cells could be further induced into neurons, astrocytes, and oligodendrocytes in differentiating medium supplemented with fetal calf serum. The results of differentiating test showed that the ratio of NF-200 and NSE positive cells was （42. 7±2. 6） % in astroeyte-indueed group and only （ 11.2 ±1.8 ） % in the control group （P〈0.01）.Conclusions Astrocytes can not only increase the production of NSCs derived from ES cells but also promote the differentiation of NSCs toward neuronal lineage.

Connexins in neurons and glia: targets for intervention in disease and injury

Both neurons and glia throughout the central nervous system are organized into networks by gap junctions. Among glia, gap junctions facilitate metabolic homeostasis and intercellular communication. Among neurons, gap junctions form electrical synapses that function primarily for communication. However, in neurodegenerative states due to disease or injury gap junctions may be detrimental to survival. Electrical synapses may facilitate hyperactivity and bystander killing among neurons, while gap junction hemichannels in glia may facilitate inflammatory signaling and scar formation. Advances in understanding mechanisms of plasticity of electrical synapses and development of molecular therapeutics to target glial gap junctions and hemichannels offer new hope to pharmacologically limit neuronal degeneration and enhance recovery.

Connecting Malfunctioning Glial Cells and Brain Degenerative Disorders

The DNA damage response（DDR） is a complex biological system activated by different types of DNA damage.Mutations in certain components of the DDR machinery can lead to genomic instability disorders that culminate in tissue degeneration,premature aging,and various types of cancers.Intriguingly,malfunctioning DDR plays a role in the etiology of late onset brain degenerative disorders such as Parkinson＇s,Alzheimer＇s,and Huntington＇s diseases.For many years,brain degenerative disorders were thought to result from aberrant neural death.Here we discuss the evidence that supports our novel hypothesis that brain degenerative diseases involve dysfunction of glial cells（astrocytes,microglia,and oligodendrocytes）.Impairment in the functionality of glial cells results in pathological neuro-glial interactions that,in turn,generate a ‘‘hostile＂ environment that impairs the functionality of neuronal cells.These events can lead to systematic neural demise on a scale that appears to be proportional to the severity of the neurological deficit.