The Role Of SDF-1/CXCR4 /CXCR7 Pathway In Neural Stem Cell Differentiation And Axon Growth

Background: Ischemic stroke is a common disease in modern society.The cause of the disease is due to brain blood supply artery stenosis or occlusion,brain tissue ischemia,hypoxia,necrosis,softening,thereby causing injury of neuronal cells,causing a series of neurological deletion symptoms,with high lethal rate and disability rate.At present,there is no effective treatment to improve the prognosis of ischemic stroke.Neural stem cells(NSCs)are considered to be the source of new nerve cells in the body,which can continuously self-renew through proliferation and differentiate into various nerve cells.Therefore,promoting the migration,proliferation and differentiation of NSCs in the infarct area to reconstruct the damaged neurovascular structure is the most promising treatment method at present.SDF-1 belongs to the subfamily of CXC chemokines,and is a class of small molecular proteins.Its two specific receptors,CXCR4/CXCR7,form a signaling pathway that can be involved in many reactions in vivo.Our previous experimental study confirmed that SDF-1 can promote the migration and differentiation of neural stem cells into neural progenitor cells in vivo and in vitro,and participate in the repair of stroke.The key steps for neural progenitor cells to participate in stroke repair include axonal bud burst,elongation and so on,and finally integrate into the original damaged neural network.However,the axonal growth of neural progenitor cells and its regulatory mechanism are still unclear.At present,it is believed that SDF-1 can promote axon growth,but the role of SDF-1/CXCR4 and SDF-1/CXCR7 signaling pathways in this process is not clear.Objective: To explore the effects of SDF-1/CXCR4 and SDF-1/CXCR7 signaling pathways on the axon growth of NSCs,and to preliminary investigate whether there is interaction between the two pathways,so as to provide a therapeutic target for improving the prognosis of stroke patients.Methods:Firstly extracted from fetal rats cortex and hippocampus neural stem cells in vitro,then cell immunofluorescence staining was used to identify neural stem cells in culture,with Nistin antibodies to marker of neural stem cells,and application of CXCR4 and CXCR7 specificity antibodies tag and looked at the two receptors expressed in neural stem cells on the surface of the situation.The neural stem cells in group A were cultured normally,the neural stem cells in group B were treated with OGD/R,and the neural stem cells in group C were treated with SDF-1 and OGD/R.The cell viability of each group was measured by CCK-8 method.To prove that SDF-1 has a protective effect on the survival of neural stem cells.Then the neural stem cells after modeling can be divided into two groups,experimental group medium,chemokines,join the SDF-1 control group culture factor,excluding SDF-1 and induce neural stem cells to differentiate into neurons,and then analyzed two groups of neurons axon length,in order to verify the SDF-1 on the role of the growing axons neural stem cell differentiation.Then,si RNA was transfected to inhibit the expression of the corresponding receptor,and the expression of the receptor after inhibition was detected by Western blot.Finally,the OGD/R model of neural stem cells transfected with si RNA was divided into four groups,and differentiation was induced.The effects of SDF-1/CXCR4 and SDF-1/CXCR7 signaling pathways on axon growth in the differentiation process of neural stem cells were studied by statistical analysis of the synaptic length of neurons in each group.Results: 1.After NESTIN identification,the cultured cells were neural stem cells,and CXCR4/CXCR7 were stably expressed on the surface of NSCs.2.The difference of OD value between OGD/R group and control group was statistically significant(P<0.01),indicating that the activity of NSCs decreased significantly after OGD/R treatment;Compared with the control group and the OGD/R group,the difference of OD value in SDF-1/OGD/R group was statistically significant(P<0.01),indicating that SDF-1has a protective effect on the survival of NSCs.3.The difference of axon length between SDF-1 group and control group was statistically significant(P<0.01),suggesting that SDF-1 could promote the growth of axons during the differentiation of NSCs.4.The CXCR4 si RNA group and CXCR7 si RNA group were statistically significant compared with the control group(P<0.001),indicating that both CXCR4 and CXCR7 could be effectively inhibited by the corresponding si RNA.5.Compared with the control group,axon growth was inhibited in the CXCR4 si RNA group,and the difference was statistically significant(P<0.01),and the axon growth in the CXCR7 si RNA group was inhibited compared with the control group,the difference was statistically significant(P<0.01),indicating that both SDF-1/CXCR4 and SDF-1/CXCR7 signaling pathways can promote the growth of axons during the differentiation of NSCs.Compared with the CXCR4/CXCR7 si RNA groups,the axon growth in both the CXCR4 si RNA group and the CXCR7 si RNA group was significantly prolonged,and the difference was statistically significant(P<0.01),indicating that the SDF-1/CXCR4 and SDF-1/CXCR7 signaling pathways may have mutually promoting synergistic effects.Conclusion:1.SDF-1 can promote the growth of axons during the differentiation of NSCs.2.The effect of SDF-1 on promoting axon growth is realized through CXCR4 and CXCR7 signaling pathways,and the two have a synergistic effect of mutual promotion.