The Effect Of HUC-MSCs On Learning And Memory Of Hypoxic-Ischemic Brain Damage In Young Rats And Its Mechanism

Background:Hypoxic ischemic brain damage（HIBD）is a common cause of nervous system damage in infants.Children often have motor and cognitive impairment.Adequate neurotrophic support is the key to the treatment of HIBD.However,there is a lack of effective nerve repair treatment,which leads to more and more children leaving sequelae of nervous system damage.In recent years,stem cells play an important role in the treatment of HIBD,but the specific mechanism is unknown.With the development of research,it has been found that the paracrine effect of stem cells plays a major role in the treatment of injury and repair by secreting a variety of nutritional factors,such as neurotrophic factor and angiogenic factor.Brain derived neurotrophic factor（BDNF）is the most abundant neurotrophic factor in the brain.The BDNF-ERK-CREB signaling pathway mediated by BDNF is a neurotrophic pathway,which plays an important role in the consolidation of learning,memory and cognitive function,CREB plays an important role in the consolidation of learning and memory,so it also provides a new direction for the mechanism research of stem cells in the treatment of HIBD.Objective:To search the influences of human umbilical cord mesenchymal stem cells（hUC-MSCs）on learning and memory function of HIBD rats,and to search the mechanism of hUC-MSCs.Methods:（1）Healthy 7-day-old SD rats were selected and divided into 3 groups（10 rats in each group）:control group（sham+0.9%Na Cl）,treatment group（HIBD+HUC MSCs）,injury group（HIBD+0.9%Na Cl）.HIBD model was established by ligation of right common carotid artery+hypoxia（8%O₂+92%N₂）.Sham operation was performed in control group.（2）The day of modeling was set as the 0th day and the7th day,each young rat in the treatment group was injected 200μL hUC-MSCs（5×10⁶cells/ml）via tail vein.Each rat in the control group and the injury group was injected200μL 0.9%Na Cl solution via tail vein.（3）On the 16th day,water maze test was carried out to evaluate the learning and memory function of young rats,and lasted until the 21st day.（4）On the 21st day,the frontal cortex of young rats in each group was taken,and the damage of frontal cortex was observed by HE staining;NeuN immunohistochemical staining was used to detect the survival of neurons in frontal cortex;Apoptosis was detected by apoptosis staining;Western blot（WB）was used to detect the phosphorylation of BDNF and CREB in frontal cortex.Results:（1）After modeling,the young rats showed abnormal muscle tension,contralateral hemiplegia and turning to the opposite side when walking,which can be preliminarily judged as successful modeling.（2）Water maze test showed that compared with the control group,the escape latency of the model group was increased,and the number of times of crossing platform was decreased,the differences were statistically significant（P<0.05）;Compared with the injury group,the escape latency of the treatment group was less than that of the injury group,and the number of times of crossing platform was increased,the differences were statistically significant（P<0.05）.（3）He staining showed that the morphology of prefrontal cortex in the control group was normal,and the model group was damaged,but the damage of prefrontal cortex in the treatment group was less than that in the injury group.（4）Immunohistochemical staining showed that compared with the control group,the number of NeuN positive cells in the prefrontal cortex of the model group decreased,and the difference was statistically significant（P<0.05）;Compared with the injury group,the number of NeuN positive cells in the prefrontal cortex of the treatment group was significantly increased（P<0.05）.（5）Apoptosis staining showed that compared with the control group,the number of apoptotic neurons in the prefrontal cortex of the model group was significantly increased（P<0.05）;Compared with the injury group,the number of apoptotic neurons in the prefrontal cortex of the treatment group was significantly reduced（P<0.05）.（6）Western blot showed that compared with the control group,the expression levels of BDNF and p-CREB in the prefrontal cortex of the injury group were significantly decreased（P<0.05）;Compared with the injury group,the expression levels of BDNF and p-CREB in the prefrontal cortex of the treatment group were increased,and the difference was statistically significant（P<0.05）.Conclusion:1.hUC-MSCs intervention can improve the learning and memory function of HIBD young rats.2.hUC-MSCs can promote the survival of prefrontal cortex neurons and reduce the apoptosis of nerve cells,so as to alleviate the brain injury of HIBD young rats.3.hUC-MSCs can improve the learning and memory function of HIBD rats,which may be related to up regulating the expression of BDNF and p-CREB in prefrontal cortex.