Study On NG2 Cells And Stroke

In 1981, Bill Stallcup and colleagues try to identify cell surface antigens expressed by different cell types in the brain, activities in cross-absorbed antisera were identified (NG1 and NG2) that recognized cell lines with properties that were intermediate between those that were purely neuronal or glial (NG). Thus, the name NG represents neuron/glial. Recently, observations made over the past two decades have revealed another new cell population that is distributed throughout the developing and mature central nervous system (CNS), these cells have been known as NG2 cells. NG2 cells that are distinct from neurons, oligodendrocytes, astrocytes and microglia. They can be identified by the expression of the proteoglycan NG2. Biochemical analysis revealed NG2 to be a chondroitin sulfate proteoglycan. The mammalian protein of 330kDa (also termed CSPG-4) is encoded by a single gene with multiple exons coding for 2327 amino acids. The NG2 proteoglycan is a type 1-transmembrane protein, with a large extracellular domain and a short cytoplasmic tail. NG2 cells have previously been assumed to represent oligodendrocyte precursor cells(OPC): new work using transgenic mice has shown that NG2 cells generate oligodendrocytes, protoplasmic astrocytes and in some instances neurons in vivo, speculated that it may be a neural precursor cells.Far from being restricted to developing and mature CNS, NG2 is expressed by a variety of mesenchymal cell types, such as immature chondroblasts, immature smooth muscle cells, developing skeletal muscle and bone, epidermal stem cells, human melanoma cells, in large vessels it is expressed by smooth muscle cells, and in microvasculature it is present on pericytes. In the current reporting, NG2 cells have the features: differentiation and migration; self-renewal and unequal division; form excitatory or inhibitory synaptic connections with neurons; record long-term potentiation (LTP), may have an important function in synaptic plasticity. Current, there is not very clear about the function and significance of NG2 cell, many questions have yet to be further research.Visfatin/Nampt is an very important protein in life activities,molecular weight of 52kDa, containing 491 amino acids. In accordance with its functions which has been discovered, named as pre-B cell colony-enhancing factor (PBEF), a visceral fat-derived adipokine visfatin, the rate-limiting enzyme in mammalian NAD biosynthesis—nicotinamide phosphoribosyl transferase(Nampt). Visfatin/Nampt widely distribute in vivo, not confined to visceral adipose tissue, it expression of the major organs and tissues have visceral fatblood nucleated cell, liver, brain, heart, spleen, pancreas, musscle, bone marrow, lung. The expression of visfatin can be changed by many external factors, such as hypoxia, low-sugar, cytokine stimulation, inflammation and so on.Visfatin with a wide range of biological functions. First, it controls the synthesis of NAD, which greatly regulation of various biological functions of organism. Furthermore, it can also promote cell proliferation, involved in inflammatory response, regulating cell differentiation, anti-apoptosis, involved in cell cycle, regulation of insulin secretion and so on.We have demonstrate that visfatin/Nampt expressed in brain. Remarkably, visfatin was significantly upregulated in peri-infarct area and infarct core of MCAO model. Inhibition of visfatin by FK866, the infarction in MCAO rats augmented. Whereas overexpression of visfatin in local brain protected against stroke injury in MCAO rats, indicating visfatin is a critical protective factor in ischemic stroke. During post-ischemic reperfusion in the adult rat brain, the number of NG2-positive cells are significantly increased within the peri-infarct area of rat brain, this upregulation of NG2 cells may be an adaptive mechanism attempting to remyelinate rat brain tissue after ischemic insult. These findings suggest that the function of these cells might be closely associated with neuroprotection and adaptive repair mechanisms in response to ischemic stress, but their precise role should be clarified in future studies.However, there is no report on visfatin for NG2 cell proliferation capabilities of the adjustment, there is no report of study NG2 cells in the Stroke-prone spontaneously hypertensive rats (SHR-SP) genetic stroke model. The topic for the visfatin role in the brain, especially study the effect on NG2 cell proliferation after cerebral ischemia injury. In addition, study the features of NG2 cells in the genetic stroke model SHR-SP, as well as the impact of visfatin. We tried to find a reactivator that can lead to NG2 cell proliferation, involved in nerve repair and functional recovery of brain damage, thereby play a role in nerve regeneration of stroke.In the first section, we establish transient focal cerebral ischemia model at first. The MCAO is a common used model of stroke, which is based on the occlusion of the middle cerebral artery (MCA) by a monofilament suture via intraluminal approach.The MCAO model has been widely used in experimental research, however, the impact factors are so many. To make the MCAO model in the success rate, infarct volume, subarachnoid hemorrhage(SAH) incidence and animal death achieve specifications and optimization, we must closely monitor those variables that affect the experimental results and keep a constant. Our model preparation process, the experimental conditions were strictly controlled, such as: the weight of rats, suture preparation, anesthesia, surgical operation and room temperature, of animal physiological parameters: blood pressure, blood gases, rectal temperature, to monitor and to keep constant, in the laser Doppler flowmetry aid of the model to improve the success rate, finally adoption of neurological behavioral score and TTC staining to determine the success rate and infarct volume of MCAO model.In the second section, we study the impact of visfatin on NG2 cells after brain ischemic insult. We have demonstrate that visfatin expressed in brain. In pre-experiment, we give the normal rats with FK866(specific enzyme inhibitor of visfatin), didn't find any unusual behavior in rats.The treatment group rats, use FK866 to inhibite visfatin, brain slices for immuno- fluorescence staining detected. In the sham group, there is no change found in NG2 cells in the brain, therefore, there is no influence on NG2 cells of normal rats by inhibiting visfatin. After cerebral ischemia-reperfusion, when visfatin was inhibited, the NG2 cells in penumbra is still show a significant proliferation, it didn't affect the NG2 cell proliferation in penumbra, we didn't find any differ of NG2 cells that in the infarct core and the contralateral region with the control group yet.Our results show that whether in normal brain or different regions of cerebral ischemic injury,visfatin don't have effect on NG2 cells.In the third section,we detect the NG2 cells in the genetic stroke model SHR-SP. The results showed that the number of NG2 cells significantly reduced in 6-month-old SHR-SP, but the number of NG2 cells in 3-month-old SHR-SP show no change, it suggest that the number of NG2 cells is related with the age of SHR-SP. Reported in the literature, the SHR-SP appears demyelination, suggesting that the demyelination may be related to the decrease in the number of NG2 cells. The link between stroke-prone and the change of NG2 cells in the SHR-SP, we will continue to study.In the forth section, we study the effect of visfatin on NG2 cells in the genetic stroke model SHR-SP. Inhibition of visfatin/Nampt accelerated the death of 6-month-old SHR-SP rats, indicating visfatin/Nampt is a critical protective factor in ischemic stroke. We give the SHR-SP with FK866 for two weeks in order to inhibit visfatin, both in 3-month-old and 6-month-old SHR-SP, the number of NG2 cells didn't have any change at all. Thus, according to our results, visfatin has no effect on NG2 cells in the genetic stroke model SHR-SP. Conclusion: In this paper, we first test whether in the normal rats, or the experimental model of focal cerebral ischemia, and genetic stroke model of SHR-SP, according to the experimental results, can't find the effect of visfatin on the NG2 cells, it seems that there is no correlation between them. The second, inhibition of visfatin accelerated the death of 6-month-old SHR-SP, suggesting visfatin is a critical protective factor in ischemic stroke. We find that the number of NG2 cells significantly reduced in 6-month-old SHR-SP, and the phenomenon is related with the age of SHR-SP. These findings suggest that the decrease of NG2 cells may be a predisposing factor in stroke-prone, we need to study further to clarify the relationship.