Expression of tenascin and BDNF during the migration and differentiation of grafted Purkinje and granule cells in the adult rat cerebellum.

It is believed that 'cell-adhesion molecules' and neurotrophic factors play important roles in the host-graft interactions during the reconstruction of injured brain by neural transplantation. In this study, we have examined the expression of such molecules and factors during the migration and differentiation of grafted Purkinje and granule cells in the adult rat cerebellum. Cerebellar primordium at the 14th gestational day (E14) was transplanted into adult rat cerebellum. Purkinje cells which had migrated from the grafted tissue into the host molecular layer were identified immunohistochemically with a specific marker, anti-spot 35 antibody, as well as by labeling them with bromodeoxyuridine (BrdU) during their final mitotic period. In the grafted site, transient expression of a neuron-glia cell adhesion molecule, tenascin, was detected immunohistochemically. This molecule was expressed transiently in the host tissue adjacent to the migratory Purkinje cells, as well as within the grafted tissue. Tenascin was not detected in intact host tissue apart from the grafted tissue. In the light of tenascin expression in the migratory process of Purkinje and granule cells during cerebellar development, the induction of this molecule in the host tissue might be involved in the migration of grafted Purkinje and granule cells. Furthermore, gene expression of brain-derived neurotrophic factor (BDNF) was found by in situ hybridization and the expression of NGF receptor was found immunohistochemically in the areas where grafted Purkinje and granule cells developed. These findings suggest the involvement of the neurotrophic factor in the growth and differentiation of the grafted cerebellar primordium.