Activities of matrix metalloproteinases-9 and-2 in uterine fluid during induced equine endometritis

Chronic degenerative changes to the endometrium include endometrial fibrosis, involving a deposition of fibrous tissue in the endometrial stroma and around the endometrial glands. In this study it is hypothesised that endometrial fibrosis is a result of extracellular matrix (ECM) remodelling following endometritis involving MMP-9 and -2 and the tissue inhibitors of MMPs (TIMPs). Endometrial biopsies and low volume uterine flushes were collected from five mares at oestrus and dioestrus before inducing endometritis. Endometritis was induced by introducing Streptococcus zooepidemicus into the uterus in oestrus and dioestrus, and by breeding the mares in oestrus. Gelatin zymography on uterine lavage fluid revealed that basal activities of MMP-2 and MMP-9 did not differ significantly between oestrus and dioestrus. A significant increase (p<0.05) in MMP-9 and -2 activities was detected post-inoculation in oestrus and dioestrus, and post-breeding in oestrus when compared to controls. In situ zymography demonstrated MMP-9 activity in eosinophils in endometrial biopsies. Basal activity of TIMP-2 was significantly higher (p<0.05) during dioestrus than during oestrus, and activity decreased during induced endometritis. The study showed that MMP-9 and MMP-2 are likely to play a role in the repair processes following endometritis and that MMP-9 is secreted by eosinophils in the endometrial stroma. Furthermore, the inhibitory activity of TIMP-2 is decreased during endometritis, in concert with the increased activity of MMP-9 and -2.