| Mastitis is a series of inflammation responses caused by the changes of metabolic and physiological state due to injury or pathogenic microorganism invasion to mammary glands.Bovine mastitis seriously affects the development of dairy industry.At the early state of mastitis,pathogens in mammary gland tube intrude into the surface of mammary glands,and further affect the physiological characteristics of the mammary gland epithelial cells and result in abnormal secretion of inflammatory cytokine.These inflammatory cytokines have effects on the physiological characteristics of stromal cells within the inner organization by the internal environment and make stromal cells preliminarily show many characteristics of the inflammatory response.Fibroblasts are predominant stromal cells in mammary tissue.The change of growth state on fibroblasts may directly affect the structure and function of normal breast tissue.Therefore,the study of the influence on stromal fibroblasts exerted by mammary gland epithelial cells in the inflammatory state means a great significance to the prevention and control of dairy mastitis.Staphylococcus aureus and Escherichia coli are the main two kinds of bacteria causing mastitis.Lipopolysaccharide(LPS)and Lipoteichoic acid(LTA)are the principal virulences of these two kinds of bacteria.In this thesis,we acquired mammary epithelial cells of the original generation from mammary tissue of Holstein cows.Firstly,we used a serie of concentrations or time periods of LPS and LTA to treat mammary epithelial cells to determine the optimum condition to establishe an in vitro cells model of bovine mastitis.Then we simulate the influence process of inflammatory bovine mammary epithelial cells on fibroblasts by co-culturing inflammatory epithelial cells from mastitic model with normal stromal fibroblasts.We investigated the influence of proliferation,migration,apoptosis,and the secretion of inflammatory cytokines of the inflammatory mammary epithelial cells on stromal fibroblasts.Meanwhile,we also explored the molecular mechanisms of the changes on these characteristics in stromal fibroblasts.Results showed that the inflammatory epithelial cells induced by LPS and LTA can promote the activation of the stromal fibroblasts.Induced inflammatory epithelial cells inhibited proliferation of fibroblasts via MAPK signal pathways and promoted the migration of stromal fibroblasts through the WNT/beta-catenin signaling pathways.Meanwhile,inflammatory epithelial cells enhanced the secretion of inflammatory related cytokines including TNF–α,CCL5,CXCL2,IL6 and IL8,and induced the deposition of extracellular matrix protein including fibronection and collagen I.These results indicated that the inflammatory epithelial cells had effects on normal stromal fibroblasts in inflammatory bovine mammary gland tissue.All this findings may provide a certain theoretical basis to further study the function of mammary stromal fibroblasts in the inflammatory response and the prevention and therapy of bovine mastitis. |
