The Morphological Development Of Pyramidal Neurons Of Human Fetal Hippocampal CA3

Hippocampus is an important part of the limbic system, one of the most important areas of medical research. Currently, research on hippocampus CA3pyramidal neurons mainly focus on rats, monkeys, cats and other animals. It lacks of morphological development in the human hippocampus CA3pyramidal neurons. In this study, rapid GolgiStain and Neurolucida software technology were used in investigating cell body circumference, cell body area, dendrite length, dendrite nodes and spines density of hippocampus CA3pyramidal neurons in different periods, in order to study the morphological development progress of human fetus hippocampus CA3pyramidal neurons and probe the regularity.Objective:To investigate the morphological development of hippocampus CA3pyramidal neurons of human fetus.Method:Take19,20,26,35,38gestation weeks(GW) fetus (induction labor with water bag)and one8-year-old (Y) child (Died in an accident), using the rapid Golgi staining method and Neurolucida software technology, measure the cell body length, area, neuron apical dendrites and base dendrites length respectively.Results:Golgi-impregnated CA3pyramidal neurons in fetuses at19,20,26,35and38GW and a child at8Y were analyzed by Neurolucida morphometry. The somal size of the impregnated CA3cells increased age-dependently among the cases. The length of the apical and basal dendrites of these neurons increased between26GW to38GW, and appeared to remain stable to8Y. The branching points of the dendrites increased from26GW to38GW, with that on the apical dendrites slightly reduced at8Y. Spine density on both the apical and basal dendrites increased progressively from26GW to8Y-At19GW and20GW, the CA3neurons have non-typical pyramidal shape. At26weeks, cell body formed the shape into three formats: triangular, round and oval, a small number of cells already take the pyramidal shape. At26,35,38GW and8Y, the cell body area is363.8±15.8(μm2),474.3±115.5(μm2),449.5±116.8(μm2),656.8±125.7(μm2) respectively. The basal dendrite length is146.0±65.6μm,1445.6±586.8μm,2329.1±815.6μm,2397.0±250.7μm respectively. The apical dendrite length is248.5±103.5μm,1720.0±795.2μm,1506.7±555.7μm,2076.1±664.9μm respectively; the basal dendrite nodes is3.3±1.0,22.4±6.3,26.0±10.3,17.8±2.2respectively; the apical dendrite nodes is4.0±2.9,8.9±4.2,16.5±3.8,12.4±6.1respectively; the basal dendrite spines density is3.8±0.3,3.8±0.5,5.14±0.8,7.4±1.6respectively; the apical dendrite spines density is3.3±1.1,4.1±0.2,5.6±1.0,7.0±0.5respectively. At35GW,38GW and8Y, the soma became wider and higher compared to that in26GW, appeared to be over60%triangular at35GW,38GW, predominantly triangular(over90%) at8Y. Meanwhile, their soma area were obviously increased compared to that in26GW,(35GW,38GW VS26GW:P<0.05,8Y VS26GW, P<0.01). But the changes became subtle with the mean area remained relatively constant between35GW to38GW and subsequently increased markedly from38GW to8Y. The soma area in8Y is the biggest among all (p<0.01). It may reach to an adult size according to the previous report: Neuronal soma grows rapidly after birth, due to the postnatal anatomical changes increase significantly.Conclusions:In the human development process, it may be a crucial period about the development of hippocampus CA3pyramidal neurons from26GW to38GW. Spine development and likely synaptogenesis on the CA3pyramidal cells progress during the third prenatal trimester, but may continue throughout the childhood.