Induction of mucin expression by estrogen and lipopolysaccharide in the lower oviductal segments in hens

Abstract

Mucins play an essential role as mucosal barrier to prevent invasion of pathogens in the oviductal tissue of hens. The aim of this study was to determine the effect of estradiol and lipopolysaccharide (LPS) on the mucin expression in the lower oviductal segments (vagina and uterus) of hens. The mucosal tissues of the vagina and uterus were collected from White Leghorn laying and molting hens, and molting hens with or without intramuscular injection with 1 mg of estradiol-benzoate (EB) daily for 7 d. Part of these tissues was cultured in TCM-199 culture medium with or without LPS (10, 100, or 1,000 ng/mL) for 1.5 or 3 h. Mucin expression in the mucosa of laying, molting, and EB-treated molting hens (EB-group) and in those tissues cultured with or without LPS was analyzed by quantitative reverse-transcription PCR. Cultured tissues were also processed for paraffin sections and stained with Alcian blue (AB). In both the vagina and uterus, mucin expression and density of AB-positive mucopolysaccharide were reduced in molting hens compared with laying hens, and upregulated by EB. Mucin expression in the cultured vagina and uterus tissues of laying and molting hens was upregulated by LPS in a dose- and time-dependent manner. However, there was no response to LPS for induction of mucin in the tissues of EB-group hens. The mucin expression level in the vagina and uterus tissues stimulated by LPS was lower in the EB-group hens than in laying and molting hens, and that in the uterus was lower in the molting hens than in laying hens. These results suggest that mucin expression is stimulated by LPS in the vagina and uterus of laying and molting hens. Estrogen may upregulate mucin expression in those tissues in association with epithelial development, whereas it may suppress the response to LPS for mucin induction. The mucin expression caused by LPS may enhance mucosal barrier function and play a role in preventing infections by bacteria in the vagina and uterus.