In vitro and in vivo characterization of hNT neuron neurotransmitter phenotypes

The hNT neuron exhibits many characteristics of neuroepithelial precursor c ells, making them an excellent model to study neuronal plasticity in vitro and in vivo. These cells express a number of neurotransmitters in vitro, in cluding dopamine, gamma -aminobutyric acid and acetylcholine, However, ther e have been few reports of the neurotransmitters that hNT neurons express i n vivo. The present study examined whether hNT neurons express the same neu rotransmitters in vivo as they do in vitro. First, the expression of tyrosi ne hydroxylase (TH), glutamic acid decarboxylase (GAD), choline acetyltrans ferase (ChAT) and the human specific nuclear marker NuMA by hNT neurons was confirmed. Nineteen normal animals were then transplanted with 80,000 hNT neurons aimed at the striatum, hippocampus or cerebral cortex. Five additio nal animals received injections of medium. All animals received daily intra peritoneal injections of cyclosporine (10 mg/kg) and survived 30 days. Sect ions through the transplants were examined for NuMA-positive hNT neurons, a nd for the presence of the three neurotransmitter markers: TH, GAD and ChAT . The hNT neurons were found in the striatum and cortex. Of the hNT neurons found within the rat striatum, 33% were ChAT-positive. In the cortex, only 4% of the neurons expressed ChAT. No GAD-positive hNT neurons were detecte d at either site. No NuMA-positive neurons were found in the hippocampus. T he implanted hNT neurons did not induce activation of astrocytes as determi ned by immunocytochemistry for glial fibrillary acidic protein (GFAP). More over, no hNT neuron was found to express GFAP in vivo. Together, these data suggest that the hNT neurons engraft in the new host tissue, maintain thei r neuronal identity and may be guided in differentiation according to local environmental cues. (C) 2000 Elsevier Science Inc.