Expression of cyclooxygenase-2 in the endometrium of gilts with different stages of endometritis

The present study determined the association among the expression of COX-2, stages of endometritis, and types and number of local immune cells infiltrating into the gilts' endometrium. The uterine tissues from 24 Landrace x Yorkshire gilts identified as acute endometritis (n = 7), chronic endometritis (n = 7), and normal endometrium (n = 10) were included. The tissues were prepared for both histological and immunohistochemical investigations. The immunoexpression of COX-2 in every layer of the gilts' endometria was appraised by avidin-biotin-peroxidase complex method via image analysis; and was reported as percentage of positive area and staining index. The results revealed that the immunoexpression of COX-2 was found only in the surface epithelial layer. The gilts with acute endometritis possessed higher both percentage of positive area (68.99% versus 4.50% and 3.43%, P < 0.001) and staining index (1.13 versus 0.05 and 0.04, P < 0.001) than those with chronic endometritis and normal endometrium, respectively. Positive correlations between the number of surface epithelial neutrophils and percentage of COX-2 positive area (r = 0.47, P = 0.022), as well as mean staining index (r = 0.44, P = 0.032) were observed. In conclusion, the immunoexpression of COX-2 was found strongest in the gilts with acute endometritis, meanwhile it was not different between those with chronic endometritis and normal endometrium. This suggested that the expression of COX-2 might be dependent not only on the infiltration of local immune cells in the endometrium, but also on the duration of exposure with inflammatory agents.