Improvement and evaluation of establishing middle cerebral artery occlusion model by nylon strand / 中国组织工程研究

ABSTRACT

BACKGROUND: Focal ischemic model made by middle cerebral artery occlusion (MCAO) is much similar to the process of onset in human cere bral infarction, whereas in the process of modeling some problems such as selection of nylon strand with improper diameter and inserted depth would result in modeling failure. OBJECTIVE: To improve MCAO model of focal cerebral infarction. DESIGN: Single-factor design, animal experiment. SETTING: Department of Pediatrics, Affiliated Maternal and Children's Hospital of Guangzhou Medical College. MATERIALS: The experiment was conducted in the Experimental Center of Guangdong Province from January. 2002 to March 2004. A total of 24 healthy Wistar rats were randomly divided into sham-operation group and model group with 10 rats in each group.METHODS: In rats of the model group, the common carotid artery (CCA) and external carotid artery (ECA) were isolated and ligated. A strand was inserted via the incision on CCA near the furcation between CCA and ECA as deep as possible with the depth of (2.0±0.2) mm. The diameter of nylon strand was 0.2 mm, the top of nylon strand was treated by melting paraffin. The interrupted time of blood circulation was 3 hours. Rats in the sham-operation group were treated by slightly drawing back the nylon strand to the CCA immediately after inserting.MAIN OUTCOME MEASURES: ①Neurobehavioral rating: It was conducted at 3 and 12 hours after ischemia with the score ranged 0-4 points.The higher the score was, the severer the neural functional deficit was, 1-3 points signified successful modeling. ②Area of cerebral infarction: Rats wereexecuted at 12 hours after ischemia. Then, brains were quickly removed and stained with tetrazolium chloride (TTC). The percentage of cerebral infarction area was calculated. ③Observation on pathological changes under light microscope.RESULTS: All of 20 rats entered the final analysis.①Eight out of 10 rats in the model group represented contra lateral tumble or draw outward circles, positive Homer's syndrome can be seen in the ligated side (3 points);One rat was disable to completely extend the claws in the contra lateral side of ligation (1 point), one rat had no neural symptoms.②Some pathological changes can be seen in the model group such as swelled cerebral tissues in the ligated side, which were bigger than the contra lateral side and were in pale; The cortex, basal ganglia and thalamus in the ligated side after TTC staining were in pale, whereas the cerebral tissues in the sham-operation group were in red with clear border.③There was no infarct in the sham-operation group, and the percentage of cerebral infarction area in the model group was (22.40±4.52)%, the infarct area of rats in groups were fundamentally same.CONCLUSION: It is necessary to adapt the strand with appropriate diameter, inserted depth and interrupting time for successful modeling.