Expression of hypoxia inducible factor-1 alpha and ischemic erythropoietin tolerance in the brain of cerebral ischemic tolerance model rats

BACKGROUND： Hypoxia inducible factor-1 alpha （HIF-1 （x） and erythropoietin（EPO）, possessing neuroprotective effect in the cerebral ischemia, might play an important role in the formation of cerebral ischemic tolerance （IT）. OBJECTIVE：To observe the neuroprotective effect of cerebral ischemic preconditioning（IPC） of rats, and the expression and mechanism of HIF-1α and target gene erythropoietin in the brain tissue following the formation of cerebral IT. DESIGN ： A randomized and controlled observation SETTING： Department of Neurology, the Affiliated Hospital of Medical College, Qingdao University MATERIALS： Totally 84 enrolled adult healthy male Wistar rats of clean grade, weighing 250 to 300 g, were provided by the Animal Experimental Department, Tongji Medical College of Huazhong University of Science and Technology. Ready-to-use SABC reagent kit and rabbit anti-rat HIF-1α monoclonal antibody were purchased from Boshide Bioengineering Co.Ltd （Wuhan）; Rabbit anti-rat EPO monoclonal antibody was purchased from Santa Cruz Company （USA）. METHODS： This experiment was carried out in the Department of Anatomy, Medical College, Qingdao University during March 2005 to March 2006. ① The 84 rats were divided into 3 groups by a lot： IPC group （n=40）, sham-operation group （n=40） and control group （n=4）. In the IPC group, middle cerebral artery was occluded for 2 hours respectively on the 1^st, 3^rd, 7^th, 14^th and 21^st days of the reperfusion following 10-minute preischemia was made using a modified middle cerebral artery second suture method from Zea-Longa. The rats were sacrificed 22 hours after reperfusion in the end of middle cerebral artery occlusion （MCAO）. That was to say, after 10-minute preischemia, suture was exited to the extemal carotid artery and embedded subcutaneously. Middle cerebral artery was occluded again to form the second reperfusion at the set time point after reperfusion. Twenty-two hours later, rats were sacrificed; In the sham-operation group,the preischemia was substituted by sham-operation（only common carotid artery and crotch were exposed, and MCAO by suture was omitted）, and the other procedures were the same as those in the IPC group. In the control group, rats were given sham-operation twice at an interval of one day, and they were sacrificed 24 hours after the second sham-operation. ② Brain tissue was taken from the rats in each group. Cerebral infarction area of each layer was measured with TTC staining, and total cerebral infarction volume （The total cerebral infarction area of each layerxinterspace ） was calculated. After brain tissue was stained by haematoxylin-esoin （HE）, the form of nerve cells was observed under an optical microscope, and the expressions of HIF-1α（and EPO protein in the brain tissue were detected with immunohistochemical method. MAIN OUTCOME MEASURES： ①Cerebral infarction volume;②form of nerve cell; ③ the expression of HIF-1α and EPO protein in the brain tissue. RESULTS：Totally 84 rats were enrolled in the experiment. The dead rats were randomly supplied during the experiment, and finally 84 rats entered the stage of result analysis. ① Detection of cerebral infarction volume of rats in each group： Cerebral infarction volume in the IPC group was significantly smaller than that in the sham-operation group on the 1^st, 3^rd and 7^th days after reperfusion respectively [（161.2±6.9） mm^3 vs （219.9±11.2） mm^3, （134.9±9.0） mm^3 vs （218.6±13.0） mm^3, （142.9±13.7） mm^3 vs （221.3±14.2） mm^3, t=-8.924, 10.587,7.947, P〈 0.01]. ② Observation of nerve cell form of brain tissue： HE staining showed that the ischemic degree, range and cerebral edema degree of IPC group were significantly milder than those of sham-operation group. ③ The expressions of HIF-1α and EPO protein in cerebral cortex and hippocampus ： The expression of HIF-1αof IPC group was significantly higher than that of sham-operation group on the 1^st, 3^rd and 7^th days after reperfusion respectively （125.93±3.79 vs 117.65±5.60, 140.63±4.64 vs 119.33±4.26, 131.15±2.74 vs 107.60±3.89, t=2.449, 6.763,9.899,P 〈 0.05-0.01）. The expression of EPO of IPC group was significantly higher than that of sham-operation group on the 3^rd and 7^th days after perfusion respectively （141.68±3.29 vs 126.33±4.51, 138.88±2.59 vs 125.58±6.18,t=5.499,3.970, P〈 0.05）. CONCLUSION ： ①IPC can protect the never cells in rat brain and the best time to onset of cerebral IT induced by IPC is 1 to 7 days after reperfusion. ② Neuroprotective effect of cerebral IT might be related to the expression of HIF-1α and its target gene EPO.

Nonhuman primate models of focal cerebral ischemia

Rodents have been widely used in the production of cerebral ischemia models. However, successful therapies have been proven on experimental rodent stroke model, and they have often failed to be effective when tested clinically. Therefore, nonhuman primates were recommended as the ideal alternatives, owing to their similarities with the human cerebrovascular system, brain metabolism, grey to white matter ratio and even their rich behavioral repertoire. The present review is a thorough summary of ten methods that establish nonhuman primate models of focal cerebral ischemia; electrocoagulation, endothelin-1-induced occlusion, microvascular clip occlusion, autologous blood clot embolization, balloon inflation, microcatheter embolization, coil embolization, surgical suture embolization, suture, and photochemical induction methods. This review addresses the advantages and disadvantages of each method, as well as precautions for each model, compared nonhuman primates with rodents, different species of nonhuman primates and different modeling methods. Finally it discusses various factors that need to be considered when modelling and the method of evaluation after modelling. These are critical for understanding their respective strengths and weaknesses and underlie the selection of the optimum model.

Middle cerebral artery occlusion methods in rat versus mouse model of transient focal cerebral ischemic stroke

Experimental stroke research commonly employs focal cerebral ischemic rat models （Bederson et al., 1986a; Longa et al., 1989）. In human patients, ischemic stroke typically results from thrombotic or embolic occlusion of a major cerebral artery, usually the mid- dle cerebral artery （MCA）. Experimental focal cerebral ischemia models have been employed to mimic human stroke （Durukan and Tatlisumak, 2007）. Rodent models of focal cerebral ischemia that do not require craniotomy have been developed using intraluminal suture occlusion of the MCA （MCA occlusion, MCAO） （Rosamond et al., 2008）. Furthermore, mouse MCAO models have been wide- ly used and extended to genetic studies of cell death or recovery mechanisms （Liu and McCullough, 2011）. Genetically engineered mouse stroke models are particularly useful for evaluation of isch- emic pathophysiology and the design of new prophylactic, neuro- protective, and therapeutic agents and interventions （Armstead et al., 2010）. During the past two decades, MCAO surgical techniques have been developed that do not reveal surgical techniques for mouse MCAO model engineering. Therefore, we compared MCAO surgical methods in rats and mice.

Electrical stimulation upregulates angiopoietin-1/Tie-2 mRNA expression in a rat model of focal cerebral ischemia

Angiopoietin-1/tyrosine kinase with immunoglobulin and epidermal growth factor homology domains 2 （Tie-2） is a newly discovered signaling pathway of angiogenesis. Angiogenesis benefits recovery of neurological functions such as swallowing. In the present study, a rat model of dysphagia following stroke was induced by middle cerebral artery occlusion to investigate the influence of low frequency electrical stimulus with bidirectional square waves and triangular waves on angiopoietin-1/-13e-2 mRNA expression. Reverse transcription-polymerase chain reaction results showed that low frequency electrical stimulus significantly improved the neurological scores of the model rats, and increased angiopoietin-1/＇13e-2 mRNA expression. This demonstrates that low frequency electrical stimulation can ameliorate neurological function in rats with focal brain ischemia, potentially through regulation of angiopoietin-1/-13e-2 expression in the angiogenesis pathway.

Meta-analysis of Buyang Huanwu decoction in animal model of cerebral ischemia

Objective:To evaluate the clinical efficacy of Buyang Huanwu decoction in treating animal model of cerebral ischemia.Methods:We searched PubMed,EMbase,Cochrane,CNKI,VIP,WanFang(1983 to 2021)for randomized control trials about Buyang Huanwu decoction treating animal model of cerebral ischemia.Results:According to the inclusion and exclusion criteria and assessment the quality of included trials(RCTs),the extraction of effective data,7 randomized clinical trials and their efficiency were evaluated,statistical analysis was conducted by using RevMan 5.3 software.The outcome measures assessed were neurological score and/or infarction volume.Meta-analysis showed that the neurological behavior scores of Buyang Huanwu decoction on animal model of cerebral ischemia was lower than the control group(SMD=2.06,95%CI(1.75,2.37),P<0.00001);The cerebral infarct volume of Buyang Huanwu decoction on animal model of cerebral ischemia were smaller than the control group(SMD=4.08,95%CI(3.57,4.58),P<0.00001).Conclusion:It was effective by using Buyang Huanwu decoction to reduce neurological behavior scores and the volume of animal model of cerebral ischemia.

Neuroprotective effects of salidroside on focal cerebral ischemia/reperfusion injury involve the nuclear erythroid 2-related factor 2 pathway

Salidroside,the main active ingredient extracted from Rhodiola crenulata,has been shown to be neuroprotective in ischemic cerebral injury,but the underlying mechanism for this neuroprotection is poorly understood.In the current study,the neuroprotective effect of salidroside on cerebral ischemia-induced oxidative stress and the role of the nuclear factor erythroid 2-related factor 2（Nrf2）pathway was investigated in a rat model of middle cerebral artery occlusion.Salidroside（30 mg/kg）reduced infarct size,improved neurological function and histological changes,increased activity of superoxide dismutase and glutathione-S-transferase,and reduced malon-dialdehyde levels after cerebral ischemia and reperfusion.Furthermore,salidroside apparently increased Nrf2 and heme oxygenase-1 expression.These results suggest that salidroside exerts its neuroprotective effect against cerebral ischemia through anti-oxidant mechanisms and that activation of the Nrf2 pathway is involved.The Nrf2/antioxidant response element pathway may become a new therapeutic target for the treatment of ischemic stroke.

A more consistent intraluminal rhesus monkey model of ischemic stroke

Endovascular surgery is advantageous in experimentally induced ischemic stroke because it causes fewer cranial traumatic lesions than invasive surgery and can closely mimic the pathophysiology in stroke patients. However, the outcomes are highly variable, which limits the accuracy of evaluations of ischemic stroke studies. In this study, eight healthy adult rhesus monkeys were randomized into two groups with four monkeys in each group： middle cerebral artery occlusion at origin segment （M1） and middle cerebral artery occlusion at M2 segment. The blood flow in the middle cerebral artery was blocked completely for 2 hours using the endovascular microcoil placement technique （1 mm × 10 cm） （undetachable）, to establish a model of cerebral ischemia. The microcoil was withdrawn and the middle cerebral artery blood flow was restored. A reversible middle cerebral artery occlusion model was identified by hematoxylin-eosin staining, digital subtraction angiography, magnetic resonance angiography, magnetic resonance imaging, and neurological evaluation. The results showed that the middle cerebral artery occlusion model was successfully established in eight adult healthy rhesus monkeys, and ischemic lesions were apparent in the brain tissue of rhesus monkeys at 24 hours after occlusion. The rhesus monkeys had symptoms of neurological deficits. Compared with the M1 occlusion group, the M2 occlusion group had lower infarction volume and higher neurological scores. These experimental findings indicate that reversible middle cerebral artery occlusion can be produced with the endovascular microcoil technique in rhesus monkeys. The M2 occluded model had less infarction and less neurological impairment, which offers the potential for application in the field of brain injury research.

Neurite Orientation Dispersion and Density Imaging of Rat Brain Microstructural Changes due to Middle Cerebral Artery Occlusion at a 3T MRI

The purpose of this work was to demonstrate the feasibility of neurite orientation dispersion and density imaging(NODDI)in characterizing the brain tissue microstructural changes of middle cerebral artery occlusion(MCAO)in rats at 3T MRI,and to validate NODDI metrics with histology.A multi-shell diffusion MRI protocol was performed on 11 MCAO rats and 10 control rats at different post-operation time points of 0.5,2,6,12,24 and 72 h.NODDI orientation dispersion index(ODI)and intracellular volume fraction(V_(ic))metrics were compared between MCAO group and control group.The evolution of NODDI metrics was characterized and validated by histology.Infarction was consistent with significantly increased ODI and V_(ic)in comparison to control tissues at all time points(P<0.001).Lesion ODI increased gradually from 0.5 to 72 h,while its V_(ic)showed a more complicated and fluctuated evolution.ODI and V_(ic)were significantly different between hyperacute and acute stroke periods(P<0.001).The NODDI metrics were found to be consistent with the histological findings.In conclusion,NODDI can reflect microstructural changes of brain tissues in MCAO rats at 3T MRI and the metrics are consistent with histology.This study helps to prepare NODDI for the diagnosis and management of ischemic stroke in translational research and clinical practice.

Effects of Tongmai Huoxue Yin(通脉活血饮) on Tumor Necrosis Factor-alpha in the Acute Cerebral Ischemia Model Rat

Objective:To observe the interfering action of Tongmai Huoxue Yin(通脉活血饮) on the acute cerebral ischemia model rat.Methods:Total 60 SD rats,30 females and 30 males,were randomly divided into 4 groups,sham-operation group,model group,Nimodipine group and Tongmai Huoxue Yin group,15 rats in each group.The acute cerebral ischemia rat model was duplicated,the middle cerebral artery(MCA) were ligated and the thread was inserted for the rats in the model group,Nimodipine group and Tongmai Huoxue Yin group,for the rats in the sham-operation group,the arteries were separated without ligature and the thread was not inserted.After the modeling has succeed,the water-decocted concentrated solution of 20-fold Tongmai Huoxue Yin clinical dosage was intragastrically administrated in a dose of 3 mL /100 g · d divided into twice,1.5 mL /100 g once.Distilled water 3 mL /100 g·d was intragastrically administrated,1.5 mL /100 g once,for the rat in the model group,Nimodipne suspension 3 mL /100 g·d(0.6 mg /100 g) for the Nimodipine group and 3 mL /100 g · d(5.4g /100 g) for the Tongmai Huoxue Yin group,no drugs for the sham-operation group.And changes of tumor necrosis factor-alpha(TNF-α) contents in the serum and brain tissue were investigated.Results:Compared with the model group,compared with the sham-operation group,serum TNF-α content at 5 h of focal cerebral ischemic ischemia in the model group started to increase and reached to the high peak at 12 h,but in both the Tongmai Huoxue Yin group and the Nimodipine group decreased in varying degrees at the same time;compared with the sham-operation group,brain TNF-α content at 6 h of focal cerebral ischemic ischemia in the model group started to increase and reached to the high peak at 12 h,but in both the Tongmai Huoxue Yin group and the Nimodipine group decreased in varying degrees,with the most obviously decreased at 24 h of ischemia.Tongmai Huoxue Yin could significantly decrease TNF-α content in the brain tissue.Conclusion:Tongmai Huoxue Yin has a protective action on acute cerebral ischemia injury in the rat.

Cluster Analysis for Acupoint Specificity of Acupuncture Effect Based on Cerebral Infarction Rat Model

Objectives： To study the acupoint specificity through the comprehensive evaluation of the acupuncture effect on rat model with the middle cerebral artery occlusion （MCAO）. Methods： Duplicated MCAO model by Zea-longa＇s thread ligation was assessed by Zausinger＇s six-point method, and rats with 1-3 scores were chosen to be grouped. According to the randomized and controlled principle, rats were divided into 6 basic control groups （including normal group, sham group, model control group, model group without intervention, Nimodipine group, lateral-to-Renzhong group） and 6 acupuncture groups [including Neiguan （PC6） group, Weizhong （BL40） group, Chize （LU5） group, Sanyinjiao （SP6） group, Renzhong （DU6） group and non-acupoint group]; in each acupoint or non-acupoint 9 different parameter combinations were respectively set by orthogonal intersection method. There were in total 60 groups, and each group had 12 rats. The rats were treated by acupuncture with the lifting-thrusting manipulation every 12 h, in total 6 times. Indices of neurobehavioral scores, cerebral blood flow, infarction rate, microcirculation, and light microscope, etc. were measured. In order to comprehensively evaluate the acupuncture effect to research the specificity of acupoint, a cluster analysis was made with SPSS17.0 for the comprehensive effect scores of the samples computed according to the comprehensive evaluation models, and then sorting and classification were made for the comprehensive effect scores. Results： In the acupuncture groups every acupoint had different therapeutic effect due to different acupuncture parameter combinations; among the acupuncture groups the orders of curative effect were as followings： Neiguan group was of exceptional result, Weizhong group and Sanyinjiao group were of valid results in upper level, Chize group and Renzhong group were of valid results in lower level, and non-acupoint group was of invalid result; the therapeutic result of acupoint group was superior to non-acupoint group; and the curative effect of acupuncture group was also superior to basic control group. Conclusion： The acupoint has the specificity of acupuncture effect, and the acupoint specificity is relative.

Evaluation of murine models of permanent focal cerebral ischemia

Background To date murine models of permanent focal cerebral ischemia have not been well characterized. The purposes of this paper were to compare three different permanent middle cerebral artery occlusion (MCAo) models with or without cra niectomy, and to identify an ideal mouse model of permanent focal cerebral ischemia. Methods Experiments were performed on 45 healthy adult male Kunming mice, weighing 28 to 42 g. The animals were randomly assigned to three groups (n=15 in every group) based on surgical procedure: MCAo via the external carotid artery (ECA), MCAo via the common carotid artery (CCA), and direct ligation of the middle cerebral artery (MCA). Each day post-ischemia, the animals were scored using an eight-grade n eurological function scale, and mortality was also recorded. Seven days post-ischemia, the brains were removed for lesion size determination using triphenyltetrazoli um chloride staining. Correlation analysis of lesion volume and neurological score was carried out. Results Mortality in the group receiving direct MCA ligation was lowest among the three groups, and there was a significant difference between the direct MCA ligation group and the two intraluminal occlusion groups (P<0.05). In all groups, neurological scores gradually increased with prolongation of ischemic duration, peaking after two days, then gradually decreasing. In the direct MCA ligation group, however, neurological scores were relatively stable. There was a significant correlation between infarct volume and neurological score 7 days after MCAo in every group (all r>0.7, P<0.05), suggesting good reproducibility of lesion volume in the three groups, but the infarct volume was more constant in the direct MCA ligation group. Conclusion The direct ligation model of MCAo provides an optimal means of studying permanent focal cerebral ischemia, and is preferable to the models using intraluminal sutures.