GH3 pituitary adenoma cells can reverse thymic aging in rats.
Thymic size and T-cell function decrease with age, and it has not yet been possible to totally reverse this thymic atrophy and completely restore T-cell-dependent immune functions. In this study, GH3 pituitary adenoma cells, which secrete growth hormone and prolactin, were implanted subcutaneously into 16- and 22-month-old female Wistar-Furth rats and the rats were sacrificed approximately 2 months later. Only thymic remnants were detected in aged, non-implanted rats, but thymus glands were found in both the 18- and the 24-month-old rats that had been implanted with GH3 cells. Thymus glands from the GH3-implanted 18-month-old rats contained distinct cortical thymocytes and medullary epithelial cells. Depending on the concentration of phytohemagglutinin or concanavalin A, T-cell proliferative responses of splenocytes from these implanted rats were 2- to 5-fold greater than those of 18-month-old controls. At the optimal concentration of mitogen, proliferative responses to either lectin could be restored to those levels observed in splenocytes from 3-month-old Wistar-Furth females. Thymus glands from 24-month-old GH3-implanted rats contained more cortical thymocytes and fewer fat vacuoles than controls, but they were not totally reconstituted. No significant lectin-induced T-cell proliferative responses or IL-2 secretion were detected in 24-month-old control rats, but splenocytes from GH3-implanted rats showed augmented T-cell proliferative responses and increased synthesis of IL-2. Fluorescence-activated cell-sorter analysis of thymocytes revealed that 24-month-old rats implanted with GH3 cells had a higher proportion of lymphocytes with the Thy-1.1 and helper-T-cell phenotypes. These data show that it is possible to regenerate normal thymic tissue in situ and reverse the natural loss in cell-mediated immunity that occurs with aging.
D000236:Adenoma / Q000503:physiopathology; D000375:Aging; D000818:Animals; D000954:Antigens, Surface / Q000032:analysis; D001854:Bone Marrow Cells; D000949:Histocompatibility Antigens Class II / Q000032:analysis; D007376:Interleukin-2 / Q000096:biosynthesis; D008938:Mitosis; D010907:Pituitary Hormones / Q000502:physiology*; D010911:Pituitary Neoplasms / Q000503:physiopathology; D051381:Rats; D013154:Spleen / Q000166:cytology; D013601:T-Lymphocytes / Q000166:cytology; D006377:T-Lymphocytes, Helper-Inducer / Q000166:cytology; D018800:Thy-1 Antigens; D013950:Thymus Gland / Q000166:cytology / Q000502:physiology*
D000954:Antigens, Surface; D000949:Histocompatibility Antigens Class II; D007376:Interleukin-2; D010907:Pituitary Hormones; D018800:Thy-1 Antigens