Immunohistochemical characteristics of the gray matter of the human spinal cord in the late prenatal period

The study is dedicated to the relevant problem of studying the patterns of age-related (prenatal) restructuring in the brain and spinal cord and provides opportunities for predicting and correcting the occurrence of congenital defects. The aim of the research was to establish the nature of immunohistochemical marker expression in the gray matter structures of the human spinal cord during the late prenatal period. The material for the study consisted of spinal cord preparations from 27 human fetuses at gestational age 35-40 weeks. The following methods were used during the research: anatomical, general histological, special histological, immunohistochemical, morphometric, and statistical analysis of the obtained data. It was found that at 35-36 weeks of the gestational period, the proliferation of neural stem cells (NSCs) occurs more intensively in the ventral neuroepithelium of spinal cord segments compared to the dorsal neuroepithelium. In the ventral neuroepithelium, there are 5-6 mitotic or post-mitotic NSCs, while in the dorsal part, there are only 2-3 cells. In fetuses at 39-40 weeks, the proliferative activity of neural stem cells in the dorsal neuroepithelium is higher in cervical and lumbar segments, where Ki-67 expression is detected in 6 % of cells (reactive in 7-8 cells), and in thoracic and sacral segments, it is 4 % (reactive in 3-4 cells). In contrast to the dorsal neuroepithelium, in the ventral part of the neuroepithelium of the segments, the proliferative activity of neural stem cells is slightly less intense. In cervical and lumbar segments, Ki-67 expression occurred in 4 % of cells (reactive in 3-4 cells), and in thoracic and sacral segments, it was 2 % (reactive in 1-2 cells). At 35-36 weeks of gestation, high vimentin expression was observed around the neuroepithelium, at the base of the posterior horns, and along the posterior median septum. Vimentin expression in the mantle layer was relatively weak and persisted along blood vessels and in the area of spinal cord root formation. Before birth, relatively weak vimentin expression was detected in the remnants of radial glia surrounding the neuroepithelial layer. Vimentin expression was absent in the neuroepithelium proper, but focal vimentin expression was observed around blood vessels. The absence of vimentin expression in the neuroepithelium indicates the disappearance of radial cells. At 35-40 weeks of the gestational period, relatively strong synaptophysin expression was observed in the mantle layer of spinal cord segments, indicating the intensity of neuronal connectivity establishment and myelination of nerve fibers. These processes continue after birth. Synaptophysin expression was absent in the neuroepithelium proper.