Individual Peculiarities of the Development and Differentiation of Embryonic Neocortex Transplants in Intact Adult Mouse Brain

We studied individual peculiarities of the development and differentiation of allogeneic transplants of neocortical cells isolated from embryos at different stages of development in intact brain of adult mice. Despite standard transplantation technique, intraparenchymal grafts considerably varied in size, morphology, and structural organization. The cells in the transplants developing inside the brain ventricles of the recipient formed histotypical structures resembling organoids. Transplants of each age group (12.5, 14.5, and 19.5 days) demonstrated individual peculiarities of cell migration, differentiation, and fiber growth. Only from cells of 12.5-day transplants formed spiny pyramidal neurons typical of V layer of the cerebral cortex. Differentiation of catecholaminergic neurons untypical of brain cortex was observed only in 14.5-day transplants. In few transplants of each age group, extensive cell migration from the transplant was observed. In some transplants, dense astrocyte accumulation was seen. In all cases (n=52), the response of the recipient’s glia to the transplant was observed, but formation of an extensive glial barrier was noted only in one case. Our findings suggest that the entire range of the results determined by individual peculiarities of the transplant growth and recipient’s response should be thoroughly realized when introducing the methods of neurotransplantation into regenerative medicine.