Characteristics and establishment of ischemic tolerance rat models with hypoxic preconditioning / 中国组织工程研究

ABSTRACT

BACKGROUND: We can investigate mechanism of endogenous neuroprotection in rat cerebral hypoxic tolerance trial. OBJECTIVE: To observe the characteristics of cerebral hypoxic tolerance in rat models with cerebral hypoxic preconditioning. DESIGN: Randomized controlled observation. SETTING: Department of Neurology, China-Japanese Friendship Hospital, Jilin University. MATERIALS The experiment was performed in the Basic Animal Experimental Center, China-Japan Friendship Hospital, Jilin University from April 2003 to April 2004. Inbred line healthy Wistar rats, of either sex, with the body mass of 200-300 g, were randomly assigned into normal control group (n=6), sham operation group (n=6), ischemic control group (n=20), hypoxic preconditioning (3 hours, 8% O2 and 92% N2) plus ischemic group (n=60) (according to different hypoxic phases, there were 5 time phases 30 minutes, 1, 3, 5 and 6 hours with 12 rats in each time phase), hypoxic preconditioning group (n=18) [according to different hypoxic phases, there were 3 time phases 1, 3 and 5 hours with 6 rats in each time phase, 3 rats received TTC staining and 3 rats received hematoxylin and eosin (HE) staining]. METHODS: ①Hypoxic preconditioning Firstly, natrica calx was put into closed glass container to absorb CO2 and O2, secondly, mixed gas of 8% O2 and 92% N2 was input, and then animals were put into the container, 3 rats each time. Temperature and humidity were kept steadily. ②Permanent ischemic middle cerebral artery rat models were established. ③The models were determined with a series in procedures neurological score, infarcted volume evaluation, pathological sample preparation, immunohistochemical staining, imaging analysis and so on. ④The data were compared in groups with variance analysis.MAIN OUTCOME MEASURES: Changes in cerebral infarcted volume, neurological score and pathological morphology in rats of experimental group and control group. RESULTS: Neurological score in the hypoxic preconditioning (8% O2, at hours 1, 3 and 5) plus ischemic group was lower than in the ischemic control group(P＜0.01). Neurological score at minute 30 and hour 6 after hypoxia (8% O2) had insignificant difference in the ischemic control group. Mean cerebral infarcted volume ratio in the hypoxic preconditioning (8% O2, at hours 1, 3 and 5) plus ischemic group was lower than in the ischemic control group(P＜0.01). Mean cerebral infarcted volume ratio after hypoxia (8% O2, at minute 30 and hour 6) had insignificant difference with ischemic control group (P＞0.05). CONCLUSION: Hypoxic preconditioning in rats can effectively release nerve injury induced by focal cerebral ischemia, suggesting that it has protective effect on brain. The procedure of establishing cerebral ischemic tolerance models with hypoxic preconditioning, which is simple and stable, with little injury on experimental animals, is a useful tool for studying cerebral ischemic tolerance.