Histological and Immunohistochemical Study on Rat Spleen in Experimentally Induced Liver Cirrhosis

Introduction: The present study aimed to examine the histological changes in the spleen of rats with liver cirrhosis, and to determine the immunohistochemical expression of endothelial nitric oxide synthase (e-OS), and its upstream effectors; tumor necrosis factor (TNF-α) and vascular endothelial growth factor (VEGF). Materials and Methods: Twenty male adult albino rats were divided into two equal groups. The first was control. In the second group, liver cirrhosis was induced by intraperitoneal (ip) injection of thioacetamide 200 mg/kg twice weekly for 12 weeks. Splenic index (spleen weight / body weight) was determined and the spleens of rats which developed liver cirrhosis were subjected to the following stains: hematoxylin and eosin (H E), silver impregnation, and immunostaining with specific antibodies for e-NOS, TNF-α and VEGF. Quantitative assessments were carried out using image analyzer with statistical analysis of the results. Results: Splenic sections of cirrhotic rats showed in addition to congestion of venous sinuses, significant increase in reticular fibers in capsule and trabeculae as well as throughout the red pulp. The percentages of red pulp and fibrous trabeculae areas were significantly higher in cirrhotic rats, while the percentage of the white pulp areas was significantly smaller. Immunohistochemical staining of both e-NOS and TNF- α in spleen sections of group II rats were significantly lower than control, while VEGF immunostaining was significantly higher. Conclusion: Splenomegaly in liver cirrhosis was not only congestive but there was also significant increase of reticular fibers, red pulp area and angiogenesis. Moreover, nitric oxide (NO) reduction resulting from suppression of e-NOS and TNF-α seen in this study contributed to the increased volume of the spleen.