Study On The Role Of Defensins Expressed In Male Reproductive System In Vivo And Establishment Of Related Methodology

Many antimicrobial peptides are expressed in mammalian male reproductive system. One major family of them is theβ-defensin that is secreted by the epithelial cells and play an important role in innate immune system. Bin1b is the firstβ-defensin protein that is discoved in male reproductive system. Besides its antimicrobial function, it was considered to be related with reproduction functions. In this paper, we constructed the transgenic mice with the Bin1b over-expressed in epididymis and studied the antimicrobial function of Bin1b in vivo. The expression pattern of transgenic mBin1b was consistent with that of endogenous mBin1b but with more than 30 folds higher. The transgenic mice were normal, health and fertility without obvious difference with wild mice in behavior. However, when they were challenged with Escherichia coli by injection into epididymis, higher resistance to bacterial and with more sperm survived than wild mice were observed. The changes in cytokines and other defensin proteins were investigated in transgenic mice during the epididymitis caused by bacterial. The antibacterial function of Bin1b and another two epididymis derived defensins, mBD-12 and mBD-37, were also studied in vitro. The results showed that mBin1b,mBD-12 and mBD-37 possess obvious antibacterial bioactivity both against Gram positive and Gram negative bacteria, however, the antibacterial activity against Escherichia coli is more strong than that against S.aureus. Moreover, the bioactivity of above defensins is salt concentration sensitivity. In this research work, we also developed a very effective conditional RNA interference system controlled by tetracycline that may be helpful for studies on the role of defensins in vitro or in vivo.