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We compared the expression of Sox2, Oct4, Nanog, Pax6, Prox1 genes associated with plasticity of neural stem and progenitor cells during human neocortex and retina development and in cell cultures. At the analyzed stages of neurogenesis, Pax6 gene is expressed in the neocortex and retina at constant levels, the expression is by one order of magnitude higher in the retina. The dynamics of Sox2 and Pax6 expression in the neocortex was similar. The expression of Oct4 and Nanog genes during neurogenesis in the neocortex and human fetal retina reflects the existence of a high-plasticity cell pool. The dynamics of βIII-tubulin expression indicates that the retina develops more rapidly than the neocortex. Our experiments showed that genetically determined cell potencies typical of native cells are realized in primary cultures without specific stimulation.

The population of neurosphere cells was studied by staining for the radial glial marker BLBP protein. An immunohistochemical study of cultures showed that neurosphere cells proliferate and retain the ability for pluripotent differentiation over 9 passages. BLBP-immunoreactive cells were present in neurospheres at all passages. However, they did not belong to the population of proliferating multipotent precursors or GFAP-positive cells. BLPB expression was detected in S-100b-positive cells of astrocyte differentiation. Our results suggest that BLBP-immunopositive cells of the radial glia in vitro loss the state of multipotent precursors and differentiate into the astroglia. Otherwise, some heterogeneous cells of the radial glia include a previously unknown linear population that differentiates into S-100b-positive astrocytes.

The structure and cell composition of spheres obtained by culturing human fetal retinal cells after 15, 18, 22-23, and 24 weeks of gestation were studied. The cells were cultured as neurospheres: in serum-free medium with growth factors, in which they formed floating spheres. Immunocytochemical analysis showed that cell proliferation in the spheres decreased with increasing fetal age. Stem/progenitor cells, neuroblasts, and photoreceptors were detected in the spheres. Glial cells were detected only in spheres originating from 22- and 24-week fetuses. All spheres, irrespective of age and duration of culturing, consisted of numerous cell rosettes, each histotypically similar to the neuroblastic layer of the developing retina.

The fate of human fetal stem/progenitor cells transplanted into rat brain depends on conditions of preculturing (long or short) and state and site of transplantation. Human nestin-positive stem cells cultured according to the short protocol did not migrate into hypoxic and normal brain after transplantation, but actively migrated in damaged spinal cord. After transplantation of long-cultured cells into the brain mainly committed neuroblasts and solitary nestin-positive cells migrated from the site of transplantation into the brain.