Effects of intravaginal lactic acid bacteria on bovine endometrium: Implications in uterine health

Infection and inflammation of the endometrium after calving compromise uterine health, contributing to decreased reproductive efficiency in dairy cows. Twenty multiparous cows were distributed in two groups and treated intra-vaginally with a combination of lactic acid bacteria (LAB) composed by Lactobacillus rhamnosus, Pedioccocus acidilactici, and Lactobacillus reuteri, or with a sterile carrier (CON) twice per week during 3 wk. At the slaughterhouse, vaginal and endometrial swabs were taken for E. coli and Lactobacillus quantification. Endometriums were collected and cut forming explants that were analyzed for the expression of 10 genes related to innate immunity and infection or submitted to an ex vivo inflammation model. In the ex vivo experiment, explants were infected with E. coli or inflammated by treating them with IL-1β and also E. coli. The secretion of IL-8, IL-1β, and IL-6 was evaluated by ELISA in the supernatants of the ex vivo cultures. Lactobacillus counts did not differ between endometria of LAB and CON cows, although E. coli vaginal counts tended to be lower in LAB than in CON cows. The expression of B-defensins and MUC1, indicators of infected uterus, was down-regulated in explants of LAB-treated cows. No differences were observed between LAB and CON explants in the ex vivo inflammation experiment. These results indicate that the vaginal application of the LAB combination used herein was unable to reach the endometrium and regulating the innate immunity at uterine level when applied into the vagina; however, it may be capable of modulating the pathogenic environment in the vaginal tract.