Implantation of Xenogeneic Transgenic Neural Plate Tissues into Parkinsonian Rat Brain

Xenografting must be considered as a means of establishing neural transplantation therapy and of securing fetal neural tissues as donor material. The early stage (embryonic day 8.5, E8.5) embryonic mesencephalic neural plate (NP) from transgenic mice was examined for possible application in effective xenografting therapy. As recipients, Parkinsonian rats treated with 6-hydroxydopamine were used, and as donors, GT4-2 mice into which a β-galactosidase gene was introduced to allow brain tissue differentiation from the recipients by X-gal staining. Three microscopic pieces of E8.5 GT4-2 mice NP were injected into the striatum of the Parkinsonian rats. Some hosts were given immunosuppressants (cyclophosphamide and FK506) (IS group), others were not (non-IS group). Amphetamine-induced rotation was examined at days 11 and 21 after grafting (D11 and D21, respectively), and morphological investigations were performed using hematoxylin-eosin (H-E), X-gal, and thyrosine hydroxylase (TH) staining. The rotations were counted in 30 of the 38 transplanted rats before and after grafting. Histological data were obtained from 19 of these 30 rats. In 11 of them the grafts survived (survival group) and in the remaining 8, the grafts were unsuccessful (rejection group). In the survival group at D11, the mean number of rotations made by transplanted rats expressed as a percentage of the number before grafting (rotation percentage) decreased to 43.8% (n = 9), which, in comparison with the average of 125.9% (n = 6) in the rejection group, reveals significant behavioral recovery (p < 0.01). The rotation percentage at D21 was 23.8% in the survival group (n = 4) and 84.5% in the rejection group (n = 3). Behavioral recovery was thus seen to improve with time in the survival group. In the IS group (n = 19), the rotation percentages averaged 74.9% (D11, n = 15) and 51.1% (D21, n = 7), while the non-IS group averages were 136.7% (D11, n = 9) and 140.7% (D21, n = 9), indicating a tendency for better behavioral recovery in the IS group than in the non-IS group (p < 0.05). Fifteen IS group rats were studied histologically, 10 (sacrificed on D11, D21) from the survival group and 5 (sacrificed on D11, D21) from the rejection group. In the non-IS group (n = 4), there was a graft in only one rat sacrificed on D11. There were many X-gal positive and TH positive cells in the grafts, suggesting that mouse NP survived, and differentiated into TH positive neurons in the rat brain. Xenografted NP has the potential to cure central nervous system diseases.