Fine structure of astroglial integration into host brain following xenografting

Previous investigations showed that fragments of fetal rabbit brain transplanted into striatum of neonatal shiverer mouse give rise to cells that migrate through host tissue and differentiate into astroglia and oligodendroglia within 2 weeks. We studied the integration of transplanted astroglia at the ultrastructural level using pre-embedding labeling with a monoclonal antibody which recognizes an epitope associated with rabbit but not mouse glial fibrillary acidic protein. The morphology of early migrating donor cells does not distinguish them from cells arising in host germinal matrix. Once the cells complete their migration they integrate into host brain in a structurally normal manner. Transplanted astroglia form perivascular foot plates with host capillaries. They also send extensive processes into the neuropil where intimate contacts with neurons and synaptic structures are formed. Oligodendroglia send processes to nearby axons where they form normal-appearing myelin. During the rejection process, which may begin at 4 weeks, donor astroglia show evidence of reaction with increased intermediate filament content. Donor cells are attacked by leukocytes, including eosinophils, and subsequently degenerate. We conclude that cross-species transplantation of glial cells can result in entirely normal structural integration into host brain.