Comparison of calcium-binding proteins expressed in cultured hNT neurons and hNT neurons transplanted into the rat striatum

An alternative source of cells for neural transplantation and brain repair that has many characteristics of immature neurons is the hNT neuron, derive d from an embryonal human teratocarcinoma (NTera2) cell line that is termin ally differentiated in vitro with retinoic acid. The majority of hNT neuron s are GABAergic in cell culture. We have determined the calcium-binding pro tein (CBP) phenotypes of hNT neurons for three CBPs, calretinin (CR), calbi ndin D-28K (CB), and parvalbumin (PV), in cell culture and after transplant ation into the rat striatum, In cell culture, 95% of all cell profiles were human nuclear matrix antigen (NuMA) positive. PV-positive hNT neurons cons tituted 50% of all neuron-like profiles, with CB+ and CR+ constituting 14 a nd 6% of cells, respectively. In contrast, when the striatal grafts were ex amined after 30 days survival using confocal microscopy, only 10% of hNT ne urons immunopositive for NuMA were PV+; 19% were CB+/NuMA+, approximately t he same percentage as was seen in vitro, and 82% of grafted hNT neurons wer e CR+, These results suggest that hNT neurons can be subdivided into at lea st three subpopulations based on the CBP phenotype that they express and th at there is a CBP phenotypic shift following transplantation. Three related hypotheses are proposed to account for this phenotypic shift of hNT neuron s after transplantation: (a) selective survival of the CR+ subpopulation of hNT neurons, (b) selective transitory quiescence of the transplanted PV+ c ells due to transplantation stress, or (c) dedifferentiation of the hNT neu rons following transplantation, which may allow them to respond to local en vironmental cues during the engraftment process, (C) 2001 Academic Press.