The Effect And The Signaling Mechanism Of TGFβ1-mediated Cell Proliferation In Bovine Mammary Epithelial Cells And Fibroblasts

Currently，with the rapid development of Chinese dairy industry, dairy cattlebreeding has reached more than95%. However, due to differences in feed and breed,there is a gap in the quality of dairy products between China and the other developedcountries, such as: Holland, New Zealand, Japan. In2010, China released a newversion of "the standards of food safety：milk ", which seted that the content of milkprotein is not less than2.8g/hg. while the standard in developed countries was noless than3.0%. It is seriously hampered the development of our dairy industry. TheNerve-endocrine-immune network plays a important role in the development,functional differentiation and lactation in mammary gland. This study aims to findout the biological function of TGFβ1in the development and the lactation capacityof bovine mammary gland. Therefore, we conducted some work as follows:We randomly sampled360milk samples from an intensive dairy farm in thesouth. We detected the protein rate by milk composition analyzer and detected theTGFβ1content by ELISA (enzyme-linked immunosorbent assay). Then, weanalysised the correlation between the concentration of TGFβ1and the rate ofprotein in milk. The results show that: there is a significant negative correlationbetween TGFβ1and the rate of protein in milk.For further explore the internalmechanism of the negative correlation between TGFβ1and the rate of protein inmilk, we studied the biological functions of TGFβ1in. First of all, we isolated andcultured bovine mammary epithelial cells and fibroblasts with high purity. Then, wedetected the function of TGFβ1in proliferation, cell cycle and apoptosis in broblastsby MTT, flow cytometry, qPCR and so on. We also detected the effect of TGFβ1incell proliferation and the expression of casein. The results show that TGFβ1cansignificantly up-regulated cell proliferation in fibroblasts by promoting DNA synthesis and cell cycle in a range of physiological concentrations. TGFβ1also canresiste the serum-deprivation-induced apoptosis in fibroblast. On the other hand,TGFβ1can significantly down-regulated the cell proliferation and the expression ofCNS2mRNA in bovine mammary epithelial cells. Finally, to further clarify thesignal transduction mechanisms of TGFβ1in cell proliferation, we detected theexpression of the ERK1/2by qPCR and Western blotting. Meanwhile, we detectedTGFβ1-mediated cell proliferation and the expression of casein after adding theinhibitor of ERK(PD98059). The results showed that TGFβ1can significantlyup-regulated the expression of ERK1/2mRNA and p-ERK1/2protein in fibroblast.TGFβ1can significantly down-regulated the expression of ERK1/2mRNA inmammary epithelial cells. However, PD98059can significantly reduceTGFβ1-mediated cell proliferation both in bovine mammary epithelial cells andfibroblasts.Above all, it can be concluded: TGFβ1is a key factor of influencing the rate ofprotein in milk. However, it can significantly down-regulated the proliferation inbovine mammary epithelial cells while up-regulated the proliferation in fibroblast.ERK1/2signaling pathway plays a important role in TGFβ1-mediated cellproliferation. TGFβ1can inhibite the proliferation of bovine mammary epithelial andpromote the proliferation of fibroblast through ERK1/2signaling pathway.This studylay a foundation of TGFβ1for the further exploration in lactation mechanism.