Neuro-glial neurotrophic interaction in the S-100β retarded mutant mouse (Polydactyly Nagoya). III. Transplantation study

The hippocampus and caudo-dorsal cortex of the homozygote of polydactyly mutant mouse (Polydactyly Nagoya, Pdn/Pdn) were markedly reduced in S-100β positive astrocytes and serotonergic fibers as compared to the heterozygote (Pdn/+) and wild type (+/+). The Pdn/Pdn mice die within 2 days after birth, so it is impossible to examine postnatal changes. To demonstrate the developmental change of Pdn/Pdn hippocampal tissue, we transplanted hippocampal pieces of neonatal Pdn/Pdn and +/+ mice into the right and left hippocampus of the same adult +/+ mice, respectively, and immunocytochemically examined them. Two weeks after transplantation, +/+ hippocampal tissue contained a large number of glial fibrillary acidic protein (GFAP) and S-100β positive astrocytes and a number of serotonergic fibers. While Pdn/Pdn hippocampal tissue contained numerous GFAP positive astrocytes, S-100β positive astrocytes and serotonergic fibers were not observed. Two months after transplantation, GFAP and S-100β were expressed in the Pdn/Pdn hippocampal tissue similar to the +/+ tissue. Serotonergic fibers were distributed in the +/+ tissue, while no serotonergic fibers were observed in the Pdn/Pdn transplant tissue. In contrast, no difference was observed in the tyrosine hydroxylase positive fibers between Pdn/Pdn and +/+ grafts. The expression of 5-HT1A receptor-like immunoreactivity was higher in the +/+ tissue than that of Pdn/Pdn tissue. The present results suggest that the expression of S-100β in the astrocytes of early stage of transplantation is a critical event for fiber ingrowth of serotonergic neurons and expression of 5-HT1A receptor.