Decreasing of S100A4 in bovine endometritis in vivo and in vitro

Endometritis is a prevalent reproductive disease in dairy cows, and is a superficial inflammation of the endometrium. S100 calcium-binding protein A4 (S100A4) is suggested to be implicated in the progression of inflammation. However, to our knowledge, no study has reported the changes of S100A4 during bovine endometritis. The objective of this study was to investigate S100A4 gene expression and protein levels in the uterus with endometritis in dairy cows. Vaginal mucus samples were collected for diagnosis of the severity degree of endometritis and the detection of S100A4 protein content. Blood samples and endometrial biopsies were collected and divided into the control (CN), mild endometrtis (M), and severe endometritis (S) groups according to the characteristics of the vaginal mucus type. The isolated bovine endometrial epithelial cells (BEECs) were challenged with E. coli (2 × 10⁶ CFU/mL, 2 × 10⁷ CFU/mL) or lipopolysaccharide (LPS, 3 and 10 μg/mL) as an inflammatory model. RT-qPCR was used to detect the gene expression levels of S100A4 and cytokines, including interleukin-1β (IL-1β), interleukin-6 (IL-6), interleukin-10 (IL-10), and tumour necrosis factor-alpha (TNF-α), in tissues or cells. Enzyme-linked immunosorbent assay (ELISA) was used for S100A4 protein level detection in tissues, cells, cell supernatant, vaginal mucus, and serum samples. The results showed that S100A4 gene and protein levels decreased in bovine endometrium with endometritis and in E. coli- or LPS-stimulated BEECs. We failed to detect S100A4 in the cell supernatant, vaginal mucus, and serum samples. This study suggested that S100A4 is a pathogenesis-related protein of endometritis, and decreased expression of S100A4 may pave the way for the development of endometritis in dairy cows.