Immunohistochemical detection of alpha-smooth muscle actin and S-100 in bovine mammary gland with mastitis

Fibrosis is a common finding in chronic mastitis. Epithelial-mesenchymal transition (EMT) plays a prominent role in fibrogenesis in adult tissues. The aim of this study was to investigate whether EMT occurs in bovine mastitis by assessing the expression or localization of alpha-smooth muscle actin (alpha-SMA), S-100 protein and caspase-3. Two normal bovine mammary gland tissue samples and five mastitic samples were used in the study. Antibodies to alpha-SMA, S-100 and caspase-3 were used for immunohistochemical studies. In mastitis there was increased expression of S-100 in the alveolar epithelial cells. Alpha-SMA was highly expressed in the areas where there is fibrosis in chronic mastitis. Further caspase-3 was observed in alveolar cells in mastitic tissue. Overexpression of S-100 and alpha-SMA directly correlates to the severity of mastitis.S-100 and alpha-SMA may serve as biomarkers to know the extent of tissue structural changes in mastitis. EMT could be one of the mechanistic pathways underlying the pathogenesis of fibrosis in mastitis.