Ghrelin promotes thymopoiesis during aging

• Published in: The Journal of clinical investigation Vol. 117; no. 10; pp. 2778 - 2790
• Main Authors: Dixit, Vishwa Deep, Yang, Hyunwon, Sun, Yuxiang, Weeraratna, Ashani T., Youm, Yun-Hee, Smith, Roy G., Taub, Dennis D.
• Format: Journal Article
• Language: English
• Published: United States American Society for Clinical Investigation 01.10.2007
• Subjects: Adaptive immunity; Adipocytes; Age; Aging; Aging - immunology; Animals; Binding sites; Biomedical research; Bone marrow; Cells; Complications and side effects; Cytokines; Ghrelin; Ghrelin - genetics; Ghrelin - metabolism; Ghrelin - pharmacology; Growth hormones; Health aspects; Leptin - pharmacology; Lymphocytes; Mice; Mice, Mutant Strains; Peptides; Receptors, Antigen, T-Cell - metabolism; Receptors, Ghrelin - analysis; Receptors, Ghrelin - genetics; Receptors, Ghrelin - metabolism; T-Lymphocytes - immunology; Thymus; Thymus gland; Thymus Gland - cytology; Thymus Gland - drug effects; Thymus Gland - immunology; United States
• ISSN: 0021-9738; 1558-8238
• DOI: 10.1172/JCI30248

The decline in adaptive immunity, T lymphocyte output, and the contraction of the TCR repertoire with age is largely attributable to thymic involution. The loss of thymic function with age may be due to diminished numbers of progenitors and the loss of critical cytokines and hormones from the thymic microenvironment. We have previously demonstrated that the orexigenic hormone ghrelin is expressed by immune cells and regulates T cell activation and inflammation. Here we report that ghrelin and ghrelin receptor expression within the thymus diminished with progressive aging. Infusion of ghrelin into 14-month-old mice significantly improved the age-associated changes in thymic architecture and thymocyte numbers, increasing recent thymic emigrants and improving TCR diversity of peripheral T cell subsets. Ghrelin-induced thymopoiesis during aging was associated with enhanced early thymocyte progenitors and bone marrow-derived Lin(-)Sca1(+)cKit(+) cells, while ghrelin- and growth hormone secretagogue receptor-deficient (GHS-R-deficient) mice displayed enhanced age-associated thymic involution. Leptin also enhanced thymopoiesis in aged but not young mice. Our findings demonstrate what we believe to be a novel role for ghrelin and its receptor in thymic biology and suggest a possible therapeutic benefit of harnessing this pathway in the reconstitution of thymic function in immunocompromised subjects.