Detection and Characterisation of Lactobacillus spp. in the Bovine Uterus and Their Influence on Bovine Endometrial Epithelial Cells In Vitro

Bacterial infections and inflammation of the uterus are common in dairy cattle after parturition. In particular, pathogenic bacteria that cause endometritis have been the focus of research in cattle reproduction in the last ten years. The aim of the present study was to identify commensal lactobacilli in the bovine uterus and to examine their influence on the synthesis of pro-inflammatory factors in bovine endometrial epithelial cells in vitro. Lactobacillus species were isolated from healthy bovine uteri and further characterised. Bovine endometrial epithelial cells in the second passage (n = 5 animals) were co-cultured with the autochthonous isolates L. buchneri, L. ruminis and L. amylovorus as well as with a commercially available L. vaginalis in different multiplicities of infection (MOI = 1, 5 and 10, respectively). Endometrial epithelial cells cultured without bacteria served as controls. At distinct points in time (2, 4 and 6 h) total RNA was extracted from co-cultured epithelial cells and subjected to reverse transcription quantitative PCR of pro-inflammatory factors. Furthermore, the release of such factors by co-cultured epithelial cells was measured by ELISA or EIA after 24 and 48 h. L. ruminis and L. amylovorus induced increased interleukin (IL) IL1A, IL6, IL8 and prostaglandin-endoperoxide synthase 2 mRNA levels and the release of IL8 and prostaglandin F(2α) in endometrial epithelial cells compared with control cells. In contrast, L. buchneri did not significantly influence the expression and release of these factors. Toll-like receptors 2 and 6 transcripts were found unchanged in co-cultured and untreated epithelial cells in vitro. However, endometrial epithelial cells of each animal showed individual differences in the response to bacterial load. These results suggest that Lactobacillus species are present in the bovine uterus, revealing immunomodulatory properties.