Thymic aging in ICR female mice is suspended by prolonged hydrocortisone exposure

Age-related decline of the thymus in ICR female mice was studied following long-term (three month) weekly exposure to hydrocortisone acetate. When examined one week after cortisone injections, the well-known thymic atrophy was observed. Five weeks after 12 hydrocortisone injections, the cortical volume fraction (Vc), cortical/medullary ratio (C/M), the number of thymocytes and CD4/CD8 profiles were in the range that characterizes younger mice, compared with PBS-injected mice, uninjected controls, or mice given a single hydrocortisone injection 5 weeks earlier. It seems as if thymic involution with age was suspended during the period of glucocorticoid exposure.