Arisio Riccardo, Bonissone Mariagrazia, Piccoli Ettore, Panzica Giancarlo
Servizio di Anatomia e Istologia Patologica e Citodiagnostica, Ospedale Sant'Anna, Corso Spezia 60, 10136 Torino, Italy.
Adv Clin Path. 2002 Jul-Oct;6(3-4):125-9.
It is thought that arterioles penetrating the central nervous system behave as terminal arteries and lack for anastomosys. The purpose of our study was to define the angiogenesys in the fetal encephalon at different stages of development. To this purpose, we examinated 13 fetal and newborn encephalons between the 10th and 33rd week. To label blood vessels, we used an immunohistochemical procedure based on the detection of two antigens located within endothelial cells: CD31 and CD34. The cerebral vascularization modifies in quantity and in structure during pregnancy, with important topographic differences between cerebral cortex and striatal-limbic areas. We observed two microarchitectural patterns: 1. Rectangular mesh pattern, characterized by capillaries that join transversally to one or more branches that deepen orthogonally from the surface of the meninges; 2. Hexagonal mesh pattern, which surrounds small groups of neurons and develops with a honeycomb shape. The rectangular mesh pattern is mostly observed from the 13th to 26th week in the white matter, in the hippocampus and in the cortex. The hexagonal mesh pattern is typical of the basal nuclei, and of the cerebral cortex during the 10th-12th week and after the 26th-27th week. Until the 26th week the vascularization increases mainly in the hippocampus and in the basal nuclei. The cortex shows a vascularization increment, greater than in the limbic system, with a pattern prevalently hexagonal in areas were the neurons' number increases. Our data demonstrate that, in the human fetus, cerebral capillaries are not of terminal type. On the contrary, they show a rich anastomotic network that has different patterns in white matter (rectangular pattern) or in grey matter (hexagonal pattern). The functional meaning of this difference is unknown, but we can suppose that its role is to warrant availability of nutritional substances within regions where a high number of neurons is present. Recent findings in computational neuroanatomy show that computer simulated axonall symmetric bifurcation can generate a dendritic tree with close similarities with real observed vascular patterns in fetal cortex.
人们认为，穿透中枢神经系统的小动脉起着终末动脉的作用，且缺乏吻合支。我们研究的目的是确定胎儿脑在不同发育阶段的血管生成情况。为此，我们检查了13例孕10周到33周的胎儿和新生儿的脑。为了标记血管，我们采用了一种基于检测内皮细胞内两种抗原（CD31和CD34）的免疫组织化学方法。孕期脑血管在数量和结构上会发生变化，大脑皮层和纹状体 - 边缘区域存在重要的地形差异。我们观察到两种微观结构模式：1. 矩形网格模式，其特征是毛细血管横向连接到从脑膜表面垂直深入的一个或多个分支；2. 六边形网格模式，它围绕着小群神经元并呈蜂窝状发展。矩形网格模式主要在白质、海马体和皮层中于第13周到26周被观察到。六边形网格模式是基底核以及第10 - 12周和第26 - 27周之后大脑皮层的典型模式。直到第26周，血管生成主要在海马体和基底核中增加。皮层的血管生成增加，比边缘系统更明显，在神经元数量增加的区域其模式主要为六边形。我们的数据表明，在人类胎儿中，脑毛细血管不是终末型的。相反，它们显示出丰富的吻合网络，在白质（矩形模式）或灰质（六边形模式）中有不同的模式。这种差异的功能意义尚不清楚，但我们可以推测其作用是确保在存在大量神经元的区域内营养物质的供应。计算神经解剖学的最新发现表明，计算机模拟的轴突对称分支可以生成与胎儿皮层中实际观察到的血管模式非常相似的树突树。
