Participation of astroglia in morphological and functional integration of neurotransplants with the recipient’s brain

Histological and electron microscopic studies of dentate fascia neurotransplants in the somatosensory region of the rat neocortex were performed. It was shown that mature nerve tissue developed in the transplants with reproduction of the organotypic characteristics of differentiated neurons and glial cells. Particular attention was paid to the study of the cellular organization of the boundary between the transplanted and neocortical tissues (interface) as well as the possibility of neuronal processes growing through it. The leading role in the integrative process belonged to different subpopulations of astrocytes. Mature protoplasmic and fibrous astrocytes, as well as astrocytic precursors, and ependymal cells were identified at different sites of the interface. The cellular composition of the border influenced the degree of integration of the transplants with the adjacent brain, ranging from maximum integration in the astrocytic type of border to limited exchange of axonal and dendritic processes in the ependymal type. Fibrous astrocyte processes accompanied and guided bundles of axons and dendrites through interface. The only barrier to the growing nerve processes were the interface regions, into which large blood vessels penetrated from the pia mater.