Is mare endometrosis linked to oviduct fibrosis?

Abstract

Endometrosis is a chronic degenerative disease of the mare's endometrium characterized by the presence of collagen fibers. Besides several causes, such as recurrent endometritis, endometrosis has been highly related to mare aging. Biopsy of mare endometrium has been used either as a diagnostic tool to assess inflammatory and fibrotic changes, or as a prognosis means of reproductive performance. We have evaluated if the presence of mare endometrial fibrosis was related to fibrosis in the oviduct. Collagen type I (COLl) and collagen type III (COL3) fibers were present in mare endometrium and in all portions of the oviduct (infundibulum, ampulla, isthmus), as detected by specific collagen protein staining with picrosirius red (PSR), and by real-time polymerase chain reaction (qPCR). When the oviduct was considered as a whole, a decrease in COL3 mRNA levels was noted in the oldest mares (>17), when compared to the youngest ones. A correlation between oviduct and endometrium fibrosis was examined. The protein COL3 was mostly found in the youngest mares' endometria and oviducts, in contrast to COL1 detected in older mares with endometrosis. In conclusion, since collagen increased in equine endometrium and oviduct with mares aging, the existence of a possible correlation between fibrosis in the endometrium and oviduct is suggested. To the best of our knowledge this is the first study that relates endometrosis to the presence of fibrosis in the mare oviduct. Thus, the histopathological evaluation of mare endometrium could give additional information on oviduct fibrosis, where a biopsy for diagnostic purposes cannot be performed.