Neuron-glial relations of the posterior horns of the spinal cord of human fetuses

Despite the relatively sufficient study of the structure and functioning of the nervous system, interest in the problem of neuron-glial relationships continues to grow steadily, as this parameter reflects the dynamics of the development of nervous tissue and can be used to assess the quality level of morphological changes. The purpose of the study: to establish the morphogenesis and neuron-glial relationships of the posterior horns of the human spinal cord in the fetal period of ontogenesis. This study was performed on the preparations of 104 human fetuses from 8-9 weeks to 39-40 weeks using anatomical, histological, immunohistochemical and morphometric methods. Statistical processing of the numerical data of the obtained results was carried out using the licensed software package “Statistica 6.1” of the StatSoft company using parametric and non-parametric methods. During the research, it was established that in the fetal period, the greater proliferative activity of the dorsal neuroepithelium is determined at 8-9 weeks: in the cervical segments – 10 % (р<0.05), in the thoracic, lumbar and sacral segments – 9 % (р<0.05). By 39-40 weeks, this indicator gradually becomes smaller: in the cervical and lumbar segments, 4 % of cells (2-3 cells reacted) (p<0.05) and in the thoracic and sacral segments – 3 % (1-2 cells reacted) (p<0.05). It was found that throughout the fetal period there is a tendency to a gradual decrease in the density of neurons and gliocytes. The glial index, on the contrary, up to 39-40 weeks increases, and at the time of birth it is equal to 2.1 in the cervical, thoracic and lumbar segments, and 2.0 in the sacral segments. It was found that at 11-12 weeks, radial glia fibers form mesh structures within the neuronal complexes, which coincides with the beginning of the formation of neuron-glial complexes of the posterior horns. At 17-18 weeks, the fibers of radial glia keep the radial direction only in the middle part of the posterior horns. At 34-35 weeks, vimentin expression was determined to be relatively moderate in the remnants of radial glia near the dorsal neuroepithelium and focal expression of vimentin around vessels within the posterior horns. Expression of vimentin in the neuroepithelium of fetuses of 39-40 weeks was absent. In this age period, the neuroepithelium is structured from ependymocytes and radial glia cells are absent, as there is a relatively strong expression of S-100 in the neuroepithelium. Relatively strong expression of synaptophysin occurred in the posterior horns of 8-9 week fetuses. This age period is the beginning of the establishment of synaptic connections.