MUC1/episialin: a critical barrier in the female reproductive tract

The female reproductive tract must resist microbial infections as well as s upport embryonic development, implantation and placentation. Reproductive t ract mucins, in general, and Muc1/episialin, in particular, play key roles in implantation related events and in protection from microbial infection. High levels of mucin expression in the lower reproductive tract presumably affords protection against infection while down-regulation of uterine mucin s has been suggested to provide access to the uterine surface. The present studies demonstrate that mucins, particularly Mud, are effective barriers t o embryo attachment. Furthermore, a strain of female Mud null mice in norma l housing displays chronic infection and inflammation of the lower reproduc tive tract and markedly reduced fertility rates. This phenotype is not obse rved when Mud nulls are housed in a pathogen-free environment indicating th at this phenotype results from chronic microbial exposure. Only normal endo genous flora were isolated from the reproductive tracts of affected Mud nul l mice, suggesting that these bacterial species become opportunistic with l oss of the mucin barrier. Staphylococcal adherence to lower reproductive tr act epithelia was found to be mediated by cell surface mucin carbohydrates. Collectively, these studies demonstrate a critical barrier role for Mud in various aspects of female reproductive tract physiology. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.