The review summarizes data of recent experimental studies on spinal microglia, the least explored cells of the spinal cord. It focuses on the origin and function of microglia in mammalian spinal cord embryogenesis. The main approaches to the classification of microgliocytes based on their structure, function, and immunophenotypic characteristics are analyzed. We discuss the results of studies conducted on experimental models of spinal cord diseases such as multiple sclerosis, amyotrophic lateral sclerosis, systemic inflammation, and some others, with special emphasis on the key role of microglia in the pathogenesis of these diseases. The review highlights the need to detect the new microglia-specific marker proteins expressed at all stages of ontogeny. New sensitive and selective microglial markers are necessary in order to improve identification of spinal cord microgliocytes in normal and pathological conditions. Possible morphometric methods to assess the functional activity of microglial cells are presented.

In neurobiological studies, crucial is the selection of most appropriate and informative experimental methods, one of which is immunohistochemistry. This review briefly summarizes the experience of adaptation of immunohistochemical methods to nervous system studies accumulated over years the Laboratory of Functional Morphology of the Central and Peripheral Nervous System (Institute of Experimental Medicine). The aim of this work was to determine the most effective and reliable immunomarkers for neurobiological studies. The article contains theoretical basis and practical recommendations for use of key cytospecific and functional markers used in studies of structural and functional organization of brain and spinal cord of mammalian animals and human. In particular, the results of immunohistochemical reactions to neural markers (NeuN, neurofilament proteins, alpha-tubulin, alpha-synuclein), neurotransmitter synthesizing enzymes (tyrosine hydroxylase, glutamate decarboxylase, choline acetyltransferase, NO synthase) and glial markers (GFAP, glutamine synthetase, Iba-1, vimentin) are demonstrated. The presented methodology is useful for experimental neurobiology and clinical morphological diagnostics.

We studied the reaction of the microglia of the anterior horns of the rat spinal cord to intraperitoneal administration of bacterial LPS. Immunohistochemical analysis showed that acute systemic inflammation leads to activation of more than half of microglial cells as soon as in 24 h after LPS injection, while the total number of microglial cells does not change significantly. It was hypothesized that activated microglial cells are involved in the reorganization of synaptic connections, but do not have a neurotoxic effect.

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Quantitative analysis of blood vessels in the distal segment of rat sciatic nerve after its ligation for 40 sec and subperineurial administration of mesenchymal stem cells or dissociated cells of rat embryonic spinal cord was carried our by immunohistochemical tracing of von Willebrand factor, a marker of endothelial cells of blood vessels. It was found that the number of blood vessels per unit area of the nerve trunk in 21 days after injury and administration of mesenchymal stem cells increased by more than 1.5 times in comparison with the control (damaged nerve). After administration of dissociated cells of the embryonic spinal cord, this effect was not observed. It is assumed that mesenchymal stem cells stimulate the growth of vessels of the damaged nerve via production of angiogenic factors.