Establishment Of A Mouse Model Of Mammary Fibrosis Induced By Escherichia Coli And Study On The Expression Of Transforming Growth Factor-β

Mastitis can cause the damage of mammary gland tissue.If the damage is not repaired completely for a long time,it can cause the cow mammary gland fibrosis or even sclerosis,which brings huge loss to the cow industry.Persistent infection of the breast by pathogenic microorganisms can cause varying degrees of desmoplasia in breast tissue and develop into severe fibrosis.Escherichia coli(E.coli)is one of the main pathogens of cow mastitis.Transforming growth factor beta factor(Transforming growth factor-β,TGF-β)is one of the key factors in the process of tissue and organ fibrosis.The purpose of this study is to explore the application of E.coli to induce breast fibrosis in mice and to promote the expression of TGF-β1 in the process of breast fibrosis.In this study,Balb/c mice were injected with different concentrations of E.coli suspension,after repeated challenge stimulation,and set up blank control group(no treatment)and reagent control group(PBS),established E.coli model of breast fibrosis in mice;at different time points,breast tissue was collected for pathological section,hematoxylin-eosin(HE)staining,and Masson trichrome staining to observe the production and distribution of collagen fibers in the breast to determine the degree of fibrosis,the expression and distribution of TGF-β1 in breast tissue were detected by immunohi stochemi stry.The experimental results show that the mammary acinar was clear and the epithelial structure was intact in the blank control group(Control)and reagent control group(PBS).Different concentrations of E.coli infected the mammary gland of mice,the acinar structure of mice was damaged in different degrees,inflammatory cells and interstitial cells proliferated,mammary epithelial cells(BMEC)necrotic shed off,the acinar structure was disorder gradually,mammary fibroblasts(BMFB)proliferated,collagenous fiber diffuse proliferation,clear E.coli-induced breast fibrosis of the development process.In the group of 108 cfu/ml,the acinus atrophied at the initial stage of infection,the inflammatory cells such as lymphocyte oozed out,the tissues were further infiltrated by a large number of inflammatory cells at the middle stage of infection,the BMFB proliferated obviously,some of the mammary glands necrosed and the structure disintegrated,at the later stage of infection,the structure of acini was disordered,a large number of fibroblasts proliferated and collagen fibers were produced.E.coli was determined to be the concentration of bacterial solution in inducing mouse mammary fibrosis;Masson staining showed that the collagenous fibers in acinar stroma,mammary lobular stroma and perivascular collagen staining increased significantly with the time of infection;TGF-β1 was mainly expressed in macrophages in inflammatory reaction.TGF-β1 positive signal could be seen in macrophages and BMEC at early stage and in BMFB and BMEC at late stage,TGF-β1 positive signal penetrated the whole process of fibrosis and its expression was gradually increased.E.coli can promote the expression of TGF-β1 during the development of fibrosis.Studies have shown that 108 cfu/ml E.coli can be used as the suitable concentration of infection bacteria in the mouse model of breast fibrosis;and the collagen fiber production increases gradually in the course of the development of the fibrosis,and distributes diffusely in the mammary gland tissue;E.coli can promote the expression of TGF-β1 in the development of mammary fibrosis in mice,and the expression level of TGF-β1 increases gradually with the development of the disease.