Thymus Hypertrophy in Orchidectomized Rats: An Immunohistochemical Study

Background: The thymus is considered to be a primary sex hormone-responsive organ, which plays an important role in maintaining a competent immune system. Aim  of  the Work: This research was conducted to study the orchidectomy-induced changes in the lymphocytic as well as the non-lymphocytic contents of the rat thymus using histological, immunohistochemical and histometrical methods. Material and Methods: Twenty male adult rats were randomly divided into two groups (control and orchidectomized). The animals were housed in cages with softwood granules as bedding. They had free access to standard diet and drinking water. Animals were sacrificed by cervical dislocation after four weeks of orchidectomy. The entire thymuses were dissected out, plot dried and weighed. Organ weights were expressed as absolute and relative weight (g/100g body weight). Five-μm sections were stained using Weigert’s haematoxylin and van Gieson’s stains for fibrous tissue, Periodic acid Schiff (PAS) for glycoproteins, methyl green-pyronin for plasma cells, Unna stain for mast cells and S-100 immunoperoxidase stain for interdigitating cells. Results: In orchidectomized rats the absolute and relative thymic weight, the mean thickness of the cortex and the cortex/medullary ratio were significantly increased in comparison to the control rats. Using image analysis and color subtraction, the area% of the interdigitating cells in cortex and medulla was calculated, there was a significant decrease in the area% of the interdigitating cells both in the cortex and the medulla of the orchidectomized rats versus the control. Conclusions: Thymus is an androgen – responsive tissue. The extract role of interdigitating cells in age induced thymic atrophy remain to be elucidated