Properties of PC12 pheochromocytoma cells transplanted to the adult rat brain.

The possibility of employing PC12 pheochromocytoma cells for transplantation into the rat brain as a substitute for adrenal chromaffin cells was examined. Cultured PC12 cells were implanted into the striatum of rats and examined after one day to 20 weeks by fluorescence histochemistry and immunocytochemical staining for tyrosine hydroxylase and a surface antigen of PC12 cells. Between 800 and 3000 cells survived the implantation procedure and persisted relatively unchanged for about one week. Long-term survival of small numbers of PC12 cells was observed in nine of 14 animals, although the number of surviving cells was reduced after 7.5-20 weeks as compared to earlier time periods. By 14-20 weeks after implantation, most of the remaining cells had developed processes. In other animals, there appeared to have been an initial large increase in the number of cells, followed by complete death of the graft. In many of these animals with no surviving cells, large deposits of hemosiderin were found at the implantation site, an apparent residue of earlier tumor growth. Thus in some animals, the number of PC12 cells apparently increased initially, but in these animals the graft was ultimately rejected. In other animals, small numbers of PC12 cells survived for up to 20 weeks, and many of these cells eventually developed neurite-like processes. Continued uncontrolled tumor growth was not observed.