Differentiation of choroid plexus ependymal cells into astrocytes after grafting into the pre-lesioned spinal cord in mice

Choroid plexus epithelial cells represent a continuation of, and have the same origin as, ventricular ependymal cells, and are regarded as modified ependymal cells. To extend previous studies of the use of choroid plexus ependymal cell (CPEC) grafting for nerve regeneration in the spinal cord, we investigated the capacity of cultured choroid plexus ependymal cells to differentiate into other types of glial cells in the spinal cord tissue. The choroid plexuses were excised from the fourth ventricle of green fluorescent protein (GFP)‐transgenic mice and the cells were dissociated and cultured for 4–6 weeks. CPECs were harvested from the monolayer cultures and injected into the pre‐lesioned spinal cords of wild‐type mice of the same strain using a Hamilton syringe. One week after injection, some GFP‐positive transplanted cells became immunohistochemically positive for glial fibrillary acidic protein (GFAP) but negative for neurofilament and myelin basic protein. All the GFAP‐positive transplanted cells were negative for vimentin. Two weeks after grafting, immunoelectron microscopy showed that the GFP‐positive transplanted cells that had gained GFAP immunoreactivity contained numerous bundles of intermediate filaments, a morphological characteristic similar to that of astrocytes, and were in close contact with adjacent host tissue. These results indicate that, when grafted into the spinal cord, at least some cultured choroid plexus ependymal cells have the capacity to differentiate into astrocytes. GLIA 36:364–374, 2001. © 2001 Wiley‐Liss, Inc.