[Administration of high dose dexamethasone impairs the function of thymus cells]

This study was purposed to investigate the effects of high-dose dexamethasone on structure and function of thymic epithelial cells (TEC). Male C57BL/6 mice aged 6 to 8 weeks were used as experimental animals. The mice were injected intraperitoneally with dexamethasone (20 mg/kg), and the other mice treated with saline were used as controls. Thymus was harvested at day 5 after treatment. The histological changes of the treated thymus were monitored by HE staining and in situ immunofluorescence staining. The ratio of each subset in the thymus were analyzed by using flow cytometry, and quantitative PCR was applied to detect the expression levels of IL-22 and Foxn1, which represent the regenerative function of thymus. The results showed that compared with control mice, the structure of TEC in mice treated with high-dose dexamethasone was damaged and the thymic cell number was declined dramatically (P < 0.05); the ratios of thymus cell subsets were changed, the number of double positive (DP) thymus cells among these subsets declined sharply (P < 0.05); the expression levels of Foxn1 and IL-22 increased by 34 and 8 folds respectively. It is concluded that the use of high-dose dexamethasone can lead to damage of the structure and function of TEC, and induce up-regulation of the expression of genes related to thymus repair.