Stereological study of the Wistar rats` thymus after application of high therapeutic doses of dexamethasone and medroxyprogesterone acetate

Abstract

Aim: The aim of our study was to evaluate the eventual immunosuppressive effect of high therapeutic dose of medroxyprogesterone acetate (MPA), to determine morphological and stereological thymic tissue characteristics and to compare them with the morphological characteristics induced by the high therapeutic dexamethasone (Dex) dose. Material and Methods: A total of 36 female Wistar rats were divided into three groups. The control group of rats were administered physiological solution, whereas the experimental groups received Dex at a dose of 3 mg/kg bw and MPA at a dose of 150 mg/kg bw. Drugs were administered intramuscularly every day, in a period of 7 days. Thymus paraffin sections were stained according to the following methods: hematoxylin-eosin, periodic acid-Schiff and elastica-van Gieson. The stereological measurements were performed by using the Weibel’s multipurpose test system (M-42). Results: Histological analysis in the drug-treated rats showed disrupted thymic cytoarchitecture, lymphocyte density reduction which in some areas was to a degree of lymphocyte depletion, presence of Hassal’s corpuscles in thymic lobules medulla and abundant presence of interstitial connective tissue. Stereological analysis showed a significant reduction in the thymic parenchyma volume density, which was due to the more pronounced decrease in the thymic lobules cortex volume density and a significant increase of the interstitial connective tissue volume density. Conclusion: Our results showed that the high therapeutic dose of MPA provoked a marked reduction in immunocompetent lymphoid tissue, which led in changing the proportion of thymic structural components. These resulted in an immunosuppressive effect. Almost identical changes were caused by the high therapeutic dose of Dex, but thymic parenchyma was significantly more sensitive substrate for Dex than for MPA.