Histostructural organization of the cerebellum of human fetuses for 8-9 weeks of prenatal development

Abstract

The high incidence of anomalies in the hindbrain is due to the fact that neurulation in the cranial compartment lasts the longest time. Therefore, for more detailed study of embryogenesis and understanding of mechanisms of pathogenesis, occurrence of congenital malformations, there is a need to determine the morphometric (histometric) parameters of the cerebellum at different gestational times. The purpose of the study is to determine the morphometric parameters of the cerebellum of human embryos for 8-9 weeks of prenatal development, as well as features of cytoarchitectonics of its structures, which is inherent in the given gestation period. Anatomo-histological, immunohistochemical and morphometric examination of the cerebellum of 10 human embryos was performed. Serial sections of cerebellum preparations 8-10 microns thick were stained with hematoxylin, eosin, toluidine blue and Van Gieson, and diagnostic monoclonal antibodies of “DacoCytomation” (Denmark): Vimentin, Ki-67 and Synaptophysin were used for immunohistochemical studies. The results of measurements of the total thickness of all layers, the density of neural stem cells (NSC), as well as the area of the right and left hemispheres of the cerebellum were obtained during the study. In immunohistochemical study, we determined the direction of NSC migration and cell proliferation of all layers of the cerebellum, as well as the length of radial glia fibers. In the cerebral hemispheres of embryos of 8-9 weeks there is a clear division into ventricular, intermediate, molecular and outer granular layers. The highest density of neural stem cells was observed in the outer granular layer – 151.0±4.1 cells per 0.01 mm2. The lowest cell density was observed in the molecular layer – 22.0±0.8 cells per 0.01 mm2. The most intense cell proliferation was established in the ventricular layer and the outer granular layer of the cerebellum, and the least intense in the intermediate layer. Synaptophysin expression was only slightly expressed in the ventricular layer of the cerebellum. The radial glial fibers begin from the ventricular layer and penetrate all layers of the cerebellum, ending in the outer granular layer. The average length of radial glial fibers was: short – 120.8±5.7 μm, long – 195.3±9.4 μm. The exterior granular layer is represented by spherical undifferentiated cells with an average area size of 641.1±28.9 μm2, the molecular layer – NSC with an area of 472.9±23.7 μm2, the intermediate layer – NSC with an area of 492.2±23.1 μm2, and the ventricular layer is represented by neuroblasts with an area of 436.1±21.8 μm2. Thus, it is established that there is a clear division of the cerebellum layers into the ventricular layer, which is represented by neuroblasts, the intermediate layer – NSC, the molecular layer – NSC, and the outer granular layer is represented by undifferentiated cells; the densest neural stem cells are located in the outer granular layer and less densely in the molecular layer.