Investigation of the roles of mast cells in lipopolysaccharide (LPS) induced mastitis model in mice

Mastitis, one of the most important and the most widespread disease of diary cattle worldwide and in our country, causes serious economic loses. In addition to milk yield, public health and animal welfare issues presented during acute phase, chronic inflammation associated fibrosis can result in functional unit loss and eventually total loss of mammary tissue. Mast cells, the sentinel cells of the immune system, play active roles during diverse physiological and pathological processes and fibrosis. Although the roles of these cells in the inflammatory process of different organs and tissues are widely known, the information about their roles in mastitis is extremely limited. In this thesis, presence, microanatomical localization, immunophenotypes, and activities of mast cells and the presence of fibrosis were examined in the mammary glands of naturally occuring mastitis cases and in LPS induced acute and chronic mastitis model in mice. In addition, the effects of mast cell stabilization on inflammatory reaction profile and fibrosis were investigated in vivo. Finally, the proliferative capacity and collagen synthesis potential of cultured bovine and mouse mammary tissue fibroblasts were evaluated in the presence of mast cell tryptase and chymase enzymes. Mast cell number and activity were increased in mammary tissues with mastitis and were correlated with the severity of fibrosis. Mast cell stabilization reduced the severity of inflammation and alleviated fibrosis. Tryptase increased proliferative activity of bovine and mouse mammary fibroblast and stimulated collagen synthesis. Similar proliferative effect were also detected in fibroblasts cultured with chymase enzyme. In this regard, it was concluded that mast cells play important roles in the pathogenesis of mastitis and mast cell stabilization may be beneficial to alleviate the severity of inflammation and fibrosis.