Arnold S E, Trojanowski J Q
Department of Psychiatry and Neurology, University of Pennsylvania School of Medicine, Philadelphia 19104, USA.
J Comp Neurol. 1996 Apr 1;367(2):274-92. doi: 10.1002/(SICI)1096-9861(19960401)367:2<274::AID-CNE9>3.0.CO;2-2.
To characterize better the process of anatomic development of the human hippocampus, we studied the cytoarchitecture, myeloarchitecture, and neuronal morphology in human fetal and postnatal hippocampi. Twenty cases were studied in which the ages ranged from 9 weeks gestation through 62 years. Fixed, paraffin-embedded, hippocampal sections were stained with cresyl violet for Nissl substance and immunolabeled for myelin basic protein. The hippocampal region at 9 weeks contains 4 layers: a ventricular zone, an intermediate zone, a homogeneous-appearing hippocampal plate comprised of bipolar-shaped neurons, and a wide marginal zone. At 15-19 weeks, individual subfields can be distinguished. A distal-to-proximal gradient of cytoarchitectural and neuronal morphologic maturity is seen, with the subiculum appearing more developed than the ammonic subfields and the dentate gyrus appearing least mature. Within each subfield, an "inside-out" gradient of maturity is also evident. By 32-34 weeks gestational age, neurons in CA2 and CA3 have undergone rapid enlargement and morphologic maturation, surpassing CA1, which still contains some immature neurons. The dentate gyrus is the latest area to develop, only assuming a mature cytoarchitecture after 34 weeks. The essential cytoarchitectural appearance of the hippocampal subfields is stable after birth, although there is progressive neuronal enlargement and a decrease in neuronal density throughout childhood into adulthood. Myelination is first evident near term, with strong myelin basic protein immunoreactivity present in the angular bundle, alveus, and fimbria and relatively scant immunoreactivity in the nascent perforant pathway. Myelination in the hippocampus increases in childhood until adolescence, after which the pattern remains unchanged. These studies delineate normal neuroanatomic development and can be used to understand better the mechanisms underlying human neurodevelopmental and neurodegenerative disorders of the hippocampal formation.
为了更好地描述人类海马体的解剖发育过程，我们研究了人类胎儿和出生后海马体的细胞结构、髓鞘结构和神经元形态。研究了20个病例，年龄范围从妊娠9周至62岁。固定的、石蜡包埋的海马体切片用甲酚紫染色以显示尼氏体，并进行髓鞘碱性蛋白免疫标记。9周时的海马区有4层：室管膜区、中间区、由双极神经元组成的外观均匀的海马板以及宽阔的边缘区。在15 - 19周时，可以区分出各个亚区。可见细胞结构和神经元形态成熟度从远端到近端呈梯度变化，下托比海马亚区更发达，齿状回最不成熟。在每个亚区内，成熟度的“由内向外”梯度也很明显。到妊娠32 - 34周时，CA2和CA3区的神经元经历了快速增大和形态成熟，超过了仍含有一些未成熟神经元的CA1区。齿状回是最晚发育的区域，在34周后才呈现成熟的细胞结构。海马体亚区的基本细胞结构在出生后是稳定的，尽管在整个儿童期到成年期神经元会逐渐增大且神经元密度会降低。髓鞘形成在接近足月时首次明显，角束、海马槽和伞中有强烈的髓鞘碱性蛋白免疫反应性，而新生的穿通通路中免疫反应性相对较少。海马体的髓鞘形成在儿童期直至青春期增加，之后模式保持不变。这些研究描绘了正常的神经解剖发育，可用于更好地理解人类海马结构神经发育和神经退行性疾病的潜在机制。
