Immunocytochemical study of PC12 cells grafted to the brain of immature rats.

Aggregated PC12 cells were transplanted to the brain of infant Sprague Dawley (SD) rats and grown for up to two months. Histochemical and immunocytochemical methods served to identify and characterize the grafted PC12 cells. It was found that PC12 cells persist and continue to proliferate within the brain of SD rats whereas it has previously been reported that grafts placed into peripheral sites do not proliferate. Dispersed and aggregated PC12 cell grafts contained immunoreactivity to tyrosine hydroxylase and aromatic amino acid decarboxylase, but failed to express phenylethanolamine n-methyl-transferase. Acetylcholinesterase activity was below histochemical detection levels in grafts of all ages. In aggregate grafts most PC12 cells were round but some small clusters of PC12 cells formed short processes. Process-forming PC12 cells were most prominent when positioned adjacent to deep layers of the cerebral cortex in one month old grafts. Host-derived capillaries and astroglia became incorporated into the PC12 aggregate grafts at successive stages. The blood brain barrier of the grafts was incomplete. This study indicates that grafted PC12 cells have some potential to restore function in brains that exhibit an endogenous dopamine deficiency, providing that mitosis in PC12 cells can be inhibited.