Short-Term Immunosuppression Enhances the Survival of Intracerebral Grafts of A7-Immortalized Glial Cells

Abstract

The A7 cell line is an astrocyte cell line produced by immortalizing optic nerve astrocytes from the embryonic Sprague-Dawley rat with SV40 large T antigen. In a previous study, we found that grafts of A7 cells into Sprague-Dawley rats survived unreliably and only for a short time after grafting into the striatum. The current experiment was designed to investigate whether short-term immunosuppression with cyclosporin A could enhance the survival of the A7 cells grafted into the adult rat striatum. A7 cells were labeled with 1,1′-dioctadecyl-3,3,3′,3′ -tetramethylindocarbocyanine (DiI) and stereotactically grafted into the left striatum of adult rat brains. Some of the host animals received cyclosporin A until 30 or 60 days after grafting. Animals were sacrificed after periods of up to 90 days, and the number and location of surviving A7 cells were determined by counting the DiI-labeled A7 cells. The possible infiltration of the host animal immune cells into the A7 grafts was evaluated using antibodies that recognize lymphocyte and macrophage antigens (anti-CD8 and anti-CD4). There was a dramatic loss of cells with time in the untreated control animals. Short-term immunosuppression with cyclosporin A significantly increased the average number of surviving A7 cells at all time points examined (30, 60, and 90 days). There was no difference in the number of surviving A7 cells between animals that received a short course of immunosuppression and those that received continuous immunosuppression for 60 days. In general, the levels of CD4 immunoreactivity in the vicinity of the A7 grafts were inversely correlated with A7 cell survival. This suggests that the host animals reacted to the A7 grafts as allografts. These results indicate that the short-term immunosuppression regimen is capable of enhancing the survival of intrastriatal grafts of the A7 astrocyte cell line.