Transgenic neural plate contributes neuronal cells that survive greater than one year when transplanted into the adult mouse central nervous system

Abstract

Neural plate cells from the early embryo may have a number of important advantages as donor material for the delivery of foreign genes into the diseased adult central nervous system (CNS). Mesencephalic neural plate from transgenic GT4-2 mice was used as a source of marked donor cells to determine whether transgene-expressing embryonic CNS progenitor cells can be used as donor material for implantation into the adult mouse brain. Transgenic mouse embryos from this line express the Escherichia coli beta-galactosidase (beta-gal) gene throughout early CNS development. At the early somite stage (Embryonic Day 8.5), mesencephalic neural plate tissue from heterozygous embryos was dissected out and either transferred into culture for characterization or immediately implanted into the striatum or lateral ventricle of adult wild-type CD-1 mice. Explants of neural plate tissue possessed intense beta-gal activity and produced extensive outgrowth of neurofilament-positive processes after 6 days in vitro. Many beta-gal-positive cells migrated away from the explanted tissue mass. Grafts of transgenic neural plate tissue in the normal adult mouse striatum, sampled 2 weeks to 1 year after implantation, possessed healthy beta-gal-positive cells. More detailed analysis of grafts 3 months after implantation indicated that most beta-gal-positive cells were also immunoreactive for neurofilament and microtubule-associated proteins, two neuron-specific markers. In addition, extensive neurofilament-positive axonal tangles were evident within the grafts among the beta-gal-positive cells. Electron microscopic (EM) findings of implanted tissue stained with Bluo-Gal revealed many beta-gal-positive neurons received synaptic contacts from other cells. A few donor-derived astrocytes were also found in the grafts by EM analysis. No obvious signs of immunological rejection, or of significant decrease in graft volume, were observed at any age. Some beta-gal-positive cells were observed to lie up to 230 microns away from the main graft mass in both striatal and intraventricular implantations. These data suggest that the neural plate can contribute a long-surviving population of neuronal and astrocytic cells when transplanted into the adult CNS.