Immunohistochemical localization of oncostatin M expression in radicular cyst

Objectives: Oncostatin M (OSM), a member of the IL-6 family, is a proinflammatory cytokine. OSM participates in variable physiological processes such as inflammatory response, cellular differentiation and proliferation. Radicular cyst is composed of fibrous connective tissue containing chronic inflammatory cell infiltrates. However, little is known about the OSM expression in radicular cysts. The aim of this study was to investigate the in situ location of OSM in radicular cysts. Methods: Thirty formalin-fixed, paraffin-embedded biopsy specimens of radicular cysts were examined using immunohistochemistry. In addition, another section from each radicular cyst specimen was stained with hematoxylin and eosin to assess the presence of inflammatory infiltrates. Differences in OSM expression between tissue with low and high levels of inflammation were subsequently analyzed by Fisher's exact test. Results: The results demonstrated that OSM expression was significantly higher in radicular cysts with higher levels of inflammatory infiltrates (p<0.05). OSM stain was detected in the lining epithelium, subepithelial fibroblasts, and endothelial cells in all specimens. Conclusions: OSM expression is significantly higher in radicular cysts. OSM demonstrates a positive relationship with the grade of inflammation in the radicular cysts.