The Experimental And Clinical Studies On Apoptosis Of Neural Cells And Its Relationship To Caspase-3 Gene Expression After Acute Traumatic Brain Injury

There are three parts in our study. Apoptosis of neural cells and its relationship to caspase-3 gene expression following acute traumatic brain injury was investigated in rats and patients. Abstract of each part described below:Part 1:A experimental study on apoptosis of neural cells in rat afterskull impact and the role of high dose methylprednisolone on it Objective To investigate the temporal and spatial characteristics of apoptosis ofneural cells and the effect of high dose methylpredinisolone on it after acute traumatic brain injury (TBI).Methods A total of 232 adult Spraque-Dawley (SD) rats were divided into a normal control group (n = 8),a mild brain injury group (n = 56),a moderate brain injury group (n = 56),a severe brain injury group (n = 56) and a post-treatment with methylpredinisolone group (n = 56). TBI models of rats were made with Feeney's method,high dose methylprednisolone (30mg/kg) were administered by intravenous injections,the rats were sacrificed at 1 hour,6 hours,24 hours,48 hours,72 hours,7 days and 14 days postinjury (n = 8 for each time-point). The specimens of the injured cerebral cortex,the injured subcortical white matter,hippocampus,dentate gyrus and contralateral corresponding brain tissues were taken for detecting apoptosis of neuralcells and the effect of high dose methylpredinisolone on it by terminal deoxynucleotide transferase-mediated deoxyuridine-biotin nick end labeling (TUNEL),flow cytometry,DNA gel electrophoresis,microscopy and transmission electron microscopy (TEM).Results Microscopy and TEM examination showed that intensive distribution of necrotic neural cells would be seen in the injured cerebral cortex and diffusive distribution of apoptotic neural cells including astrocytes,microgliocytes,oligodendrocytes and neurons in the injured subcortical white matter,hippocampus and dentate gyrus at various time points. Apoptotic neural cells were identified asearly as 1 hour post injury,reached a peak at 48 to 72 hours,and still observed at 14 days. Two types of TUNEL-positive neural cells were represented by TEM,including type I cells that displayed morphological features of necrotic cells and type II cells that displayed morphological features of classic apoptotic cells. As early as 1 hour post injury,type II TUNEL-positive neural cells were detected in the injured side brain tissues,reached their peak at 24 to 72 hours,and then declined after 14 days. Apoptotic neural cells in the groups of moderate brain injury were more than those in the groups of severe brain injury that were more than those in the groups of mild injury. Neural cells apoptosis indexes (AI) at 1 hour post injury were significantly higher than those of the normal control group (P < 0.01),and kept at high levels up to 14 days (P < 0.01). Flow cytometry of damaged brain tissues at various time points showed a typical Ap wave. The percentage of apoptotic cells hi various brain regions increased quickly,significantly higher than that of the normal control group at 1 hour post injury (P < 0.05),and reached its peak at 48 to 72 hours,then decreased slQwly,but still higher than normal at 14 days (P < 0.05). Gel electrophoresis of DNA extracted from the injured subcortical white matter and hippocampus presented typical "ladder" break in mild brain injury groups at 6 hours to 7 days,and in moderate and severe brain injury groups at 1 hour to 14 days. The treatment with high dose methylprednisolone reduced significantly the number of apoptotic neural cells that we counted hi the various brain regions at various tune points,and compared with the controls at 30 minutes,6 hours 7 days and 14 days,AI and the percentage of apoptotic cells were no significant difference at various brain regions (P > 0.05). DNA extracted from the injured subcortical white matter and hippocampus presented no "ladder" break at various tune points except at 24-72 hours in the treated rats.Conclusions These results indicate that acute TBI can induce apoptosis of neural cells,the efficiency of apoptosis is related to...