| Objectives: Ischemic stroke does harm to people's health seriously. It becomes a hot topic to study the pathophysiologic mechanism of ischemic stroke and search for efficient way to cure it. Following the study carrying out, some people has pointed out that there is a rim of mild to moderately ischemic tissues (ischemic penumbra) between the normal perfused brain and the evolting infarct. It's size varies according to the time and the therapy. The theory of ischemia-reperfusion injury contains several reactive mechanisms, such as inflammation and apoptosis and excitotoxic amino acids injury and so on. The cascade of damage takes place mainly in the ischemic penumbra. In the course of these studies, many people pay attention to Platelet-Derived Growth Factor (PDGF) with multifunction, which is associated with lots of physiologic and pathophysiologic processes in bodies. There is little study about PDGF-BB in ischemia-reperfusion injury. In our experiment we study the expression of PDGF-BB in middle cerebral artery occlusion/reperfusion rat model and discussed the protective machenisms.Methods: There are 60 healthy male Sprague-Dawley rats , and they weight 250~300g respectively. They were divided randomly into two groups:①middle cerebral artery occlusion/reperfusion (MCAO/R) group: it was further divided into five subgroups evenly at different time point such as 6 h, 24 h, 48 h, 72 h, 7 d reperfused after suffering ischemia 3 hours,six rats each subgroup.②sham-operated group: it was also further divided into five subgroups at different time point such as 6 h, 24 h, 48 h, 72 h, 7 d after operation, six rats each subgroup. The rats in MCAO/R group were operated according to the improved MCAO model. The rats in sham-operated were operated as the MCAO/R group, except of not pulling the mononalon line into the ECA.Motor behavior was evaluated using 3 tests in each rat at 6 h, 24 h, 48 h, 72 h and 7 d after MCAO/R operation. The specific 3 tests included Longa behavioral test, Berderson behavioral test and Beam walking test. At 6 h, 24 h, 48 h, 72 h and 7 d, after the motor-behavior tests were done, each rat was killed by pentobarbital overdose. The brain was quickly removed and placed on a cooled surface, and the frontal pole (approximately 4 mm thick), the cerebellum and brain stem were removed. The cerebrum was coronally cut. The first part (almost 2 mm thick) was used for brain edema measurement and was cut into two sections: ipsilateral and contralateral. Each section was wrapped in preweighed aluminum foil and weighed to obtain the wet weight (WW), then dried for 72 h in an oven at 95～110℃and weighed again to obtain the dry weight (DW). Brain water content was calculated as the percentage change between wet weight and dry weight using the following formula: (WW-DW)/WW×100%.The vestigial brain were embed in paraffin wax. Serial coronary sections (4μm) were used for immunohistochemistry to detect the expression of PDGF-BB at different time point to explore the mechanisms, and some sections were hemotoxylin-esion (HE) stained to observe the pathological structure.Results:⒈Behavioral evaluation: after MCAO/R operation, rats all existed motor deficit. There is no difference existed between MCAO/R group and sham group at 6 h because of the anesthesia and injuries during the operation. At 24 h~72 h, the scores of the MCAO/R group leveled high until all the rats recovered and the scored began to fall at 7d.⒉Brain water content:①The results showed that brain water contents were 79.58±0.179 (mean±standard error) versus 77.62±0.174 between the MCAO/R group and the sham group at the ipsilateral at 6 h, P>0.05, which had no differences; 82.42±0.118 versus 77.62±0.174 at 24 h, P<0.05,which had differences; 85.40±0.099 versus 77.62±0.174 at 48 h, P<0.01; 84.87±0.154 versus 77.62±0.174 at 72 h, P<0.05; 80.87±1.846 versus 77.62±0.174 at 7 d, P>0.05.②in MCAO/R group, the result of brain water contents in the ipsilateral and the contralateral were: 79.58±0.179 versus 78.05±0.117 at 6 h after operation, P>0.05; 82.42±0.118 versus 78.75±0.055 at 24 h after operation, P<0.05; 85.40±0.099 versus 78.32±0.094 at 48 h after operation, P<0.05; 84.87±0.154 versus 79.26±0.242 at 72 h after operation, P<0.05; 80.87±1.846 versus 79.35±0.224 at 7 d after operation, P>0.05.③Sham subgroups at different time points after intracerebral infusion have no significant differences.⒊HE staining: There is no infarction in sham operation group, the shape and structure of the neurons were normal, there is no edema interstitial. There are obvious infarction in MCAO/R group, the infarct zone were located extensively among striatum and cortex, the neurons were found deformed and shrunken, nucleus and cytoplasm were concentrated, edema was obvious. The infiltration of polymorphonuclear leukocyte(PMN)was most obvious at MCAO 3 h/R 72 h; the proliferation of glial cells was most obvious at MCAO 3 h/R 7 d.⒋the expression of PDGF-BB: immunohistochemistry demonstrated that PDGF-BB expressed very little in sham group, but in the model group PDGF-BB expressed increasingly at 6 h, reached maximum at 7 d.①PDGF-BB positive cells in the MCAO/R group and the sham group were 11.83±1.60 versus 5.52±1.78 at 6 h after operation, P<0.05; 15.67±2.07 versus 6.02±1.99 at 24 h after operation, P<0.05; 22.67±1.63 versus 5.89±1.45 at 48 h after operation, P<0.05; 25.33±2.51 versus 5.69±1.86 at 72 h after operation, P<0.05; 28.83±3.19 versus 6.13±2.01 at 72 h after operation, P<0.05.②In MCAO/R group,there is difference between every two subgroups, P<0.05; especially, there was significant deviation between MCAO 3 h/R 6 h(11.83±1.60)and MCAO 3 h/R 24 h(15.67±2.07),P<0.01.Conclusions: ischemia and reperfusion can induse expression of PDGF-BB. This neuroprotection factor can protect and regulate itself and promote blood vessels proliferation surrounding ischemic zone and help recovery.
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