Comparison of adrenal medullary, carotid body and PC12 cell grafts in 6-OHDA lesioned rats

The survival and functional properties of dispersed cell implants of catecholaminergic cells obtained from the peripheral nervous system of adult rats (adrenal medulla and carotid body glomus cells) and PC12 cells from a rat pheochromocytoma cell line were examined following transplantation into the striatum of the adult rat. The host animals, all with unilateral 6-hydroxydopamine (6-OHDA) nigrostriatal lesions, were divided into 5 groups: (1) PC12 cells transplanted into Cyclosporin-A treated hosts; (2) PC12 cell grafts into hosts without Cyclosporin-A treatment; (3) grafts of adrenal medullary cells; (4) grafts of glomus cells; and (5) vehicle controls. All animals were sacrificed one month after transplantation. Immunocytochemical staining for tyrosine hydroxylase, the rate-limiting enzyme for catecholamine synthesis, was used to identify and characterize the grafted cells. PC12 cells were detected in four of six Cyclosporin-A treated rats, and two of these grafts developed into tumors. However, only one of the six non-Cyclosporin-A treated hosts was found to have surviving PC12 cells, and none of these rats developed tumors. No significant differences in rotational behavior were seen in either of the PC12 cell recipient groups. Grafted cells could be identified in all of the adrenal medullary and glomus cell recipients. However, the number of surviving cells was quite limited, with not more than 100 tyrosine hydroxylase-positive grafted cells found in any one recipient. Tyrosine hydroxylase-positive fibers were present adjacent to the transplants in these latter graft recipients, but the fibers appeared to be of host origin rather than from the grafts. The behavioral data showed that the implantation of both adrenal medullary and glomus cells significantly (p<0.05) reduced the amphetamine-induced rotational behavior in 6-OHDA lesioned rats compared to the control group. Due to the small number of surviving grafted chromaffin and glomus cells and the apparent sprouting of host tyrosine hydroxylase-containing fibers, the present study raises questions about whether the behavioral recovery is due to catecholamine released by the grafted cells or from graft induced-recovery of host systems.