USE OF A RAT Y-CHROMOSOME PROBE TO DETERMINE THE LONG-TERM SURVIVAL OF GLIAL-CELLS TRANSPLANTED INTO AREAS OF CNS DEMYELINATION

A lack of suitable markers for cells which undergo division following transplantation has hindered studies assessing the long-term survival of glial cell grafts in the CNS. A probe specific to the rat Y chromos ome was used to identify male glial cells grafted into an area of ethi dium bromide-induced demyelination in syngeneic adult female rat spina l cord 4 weeks, 6 months and 12 months post-transplantation. At all ti me points there was extensive oligodendrocyte remyelination of transpl anted lesions, and graft-derived cells were present within the lesion up to 12 months post-transplantation. In order to demonstrate graft-de rived oligodendrocytes in the remyelinated region at 6 and 12 months, double-labelling studies were performed using the oligodendrocyte-spec ific antibodies carbonic anhydrase II or phosphatidyl ethanolamine-bin ding protein in combination with the Y chromosome probe. It was found that the majority of oligodendrocytes in the transplanted region were graft-derived. Graft-mediated remyelination was associated with a redu ction in myelin sheath thickness and increase in nodal frequency simil ar to that observed in spontaneous remyelination, suggesting that, lik e axons remyelinated spontaneously, axons remyelinated by grafted cell s will be capable of secure conduction. An alteration in the immunorea ctivity of oligodendrocytes from carbonic anhydrase II-negative in the unlesioned dorsal funiculus to carbonic anhydrase II-positive in the remyelinated dorsal funiculus was considered to reflect a reduction in the amount of myelin supported by each oligodendrocyte, leading to th e proposal that carbonic anhydrase II immunoreactivity may provide a m eans of identifying areas of remyelination in normally carbonic anhydr ase II-negative white matter tracts.