Falkowski Anna, Hammond Rob, Han Victor, Richardson Bryan
CIHR Group in Fetal and Neonatal Health and Development, Department of Obstetrics and Gynaecology, The Lawson Heath Research Institute, University of Western Ontario, London, Canada.
Brain Res Dev Brain Res. 2002 Jun 30;136(2):165-73. doi: 10.1016/s0165-3806(02)00361-9.
Programmed cell death or apoptosis plays a central role during the development of the brain, but can also be activated by hypoxic/ischemic insult. The purpose of the present study was to determine the regional distribution of apoptotic cells in the preterm and near term ovine fetal brain and thus in relation to the maturation of neurobehavioural activity, and the effect of intermittent umbilical cord occlusion (UCO), which might then contribute to adverse neurodevelopment. Fetal sheep (control and experimental groups at 0.75 and 0.90 of gestation) were studied over 4 days with UCOs performed in the experimental group animals by complete inflation of an occluder cuff for 90 s every 30 min for 3 to 5 h each day. Animals were then euthanized and the fetal brain perfusion-fixed and prepared for subsequent histology and apoptosis staining using the TUNEL assay method. The number of TUNEL positive cells for both the preterm and near term control group animals was low but with a significant regional hierarchy whereby values were higher in the cerebellar peduncle and cortex and lower in the cortical grey and white matter, hippocampus, and pons. While the apoptotic indices (expressed as TUNEL positive cells/1000 cells or high powered field) for most brain regions were not significantly changed between the preterm and near term control group animals, that for the hippocampus and pons were increased approximately 5- and 4-fold, respectively, (both P<0.05), in the near term animals. Intermittent UCO with severe but limited hypoxemia and no cumulative acidosis to ensure longer term survival, had no significant effect on apoptotic indices in the brains of either the preterm or near term animals, although hippocampal values for both occlusion groups were increased approximately 2-3-fold. Levels of apoptosis noted for the ovine fetal brain at 0.75 to 0.90 of gestation are thus low and likely approaching the basal levels of later life, but there are regional differences and changes over this period although little change in response to intermittent cord occlusion as studied, with implications for behavioural state activity and antenatal hypoxic insults in the brain's development.
程序性细胞死亡或凋亡在大脑发育过程中起核心作用，但也可由缺氧/缺血性损伤激活。本研究的目的是确定早产和近足月绵羊胎儿大脑中凋亡细胞的区域分布，从而确定其与神经行为活动成熟的关系，以及间歇性脐带阻塞（UCO）的影响，这可能会导致不良神经发育。对胎羊（妊娠0.75和0.90时的对照组和实验组）进行了4天的研究，实验组动物每天进行3至5小时的UCO，每30分钟用阻塞袖带完全充气90秒。然后对动物实施安乐死，对胎儿大脑进行灌注固定，并使用TUNEL检测法进行后续组织学和凋亡染色。早产和近足月对照组动物的TUNEL阳性细胞数量均较低，但存在显著的区域层次结构，小脑脚和皮质中的值较高，而皮质灰质和白质、海马体和脑桥中的值较低。虽然早产和近足月对照组动物大多数脑区的凋亡指数（以TUNEL阳性细胞/1000个细胞或高倍视野表示）没有显著变化，但近足月动物海马体和脑桥的凋亡指数分别增加了约5倍和4倍（均P<0.05）。间歇性UCO导致严重但有限的低氧血症且无累积性酸中毒以确保长期存活，对早产或近足月动物大脑中的凋亡指数没有显著影响，尽管两个阻塞组的海马体值均增加了约2至3倍。因此，妊娠0.75至0.90时绵羊胎儿大脑中的凋亡水平较低，可能接近成年后的基础水平，但在此期间存在区域差异和变化，尽管如研究中所示，对间歇性脐带阻塞的反应变化不大，这对行为状态活动和大脑发育中的产前缺氧损伤具有影响。
