P14: Analysis of the morphological and antigenic phenotype of radial glia after transplantation into the developing rat ventricular system in utero

Gliogenesis in the spinal cord has been studied extensively, but questions remain relating to glial origins and lineage, particularly the fate of radial and radial glial cells. Recent reports have raised doubts about the distinction between radial glia and neuronal precursor cells by demonstrating that radial glia, at least in the cerebral cortex, are themselves neuronal progenitor cells. It remains unknown whether radial glial cells can give rise to neurons in the spinal cord. Transplantation in utero of enriched populations of radial glia into the ventricular zone (VZ) of host animals at different developmental ages can reveal the lineage, developmental potential and their interaction with the host microenvironment. The in utero transplantation of cell suspensions of primary tissue may allow for determination of developmental capacity of progenitor cells. An enriched population of radial glial cells has been isolated from rat embryonic day (E)14 spinal cords by negative immunoselection with a neuronal cell surface antigen. Isolated radial glia are labelled with a fluorescent dye and injected into the telencephalic vesicles and 4th ventricles of E14-20 rat fetuses in utero. Recipient animals are killed after 15 h, 5, 10 and 20 days survival and brains and spinal cords of these embryos are fixed, sectioned transversely and analysed using confocal microscopy. Initial observations show that implanted cells leave the ventricular system and penetrate the host VZ. Longer survival times allowed greater integration and migration of cells into the host brain. Transplant cells became more branched as age and survival time increased and they differentiated sooner in older aged host environments. A detailed analysis of the immunohistochemical characterization at different ages and survival intervals should enable precise fate mapping of the transplanted radial glia and further elucidation of their function, especially in the spinal cord. Precursor cells in the developing spinal cord will also be examined using a replication incompetent enhanced GFP-expressing retrovirus.