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 (COL1) 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.

Collagen and Eosinophils in Jenny's Endometrium: Do They Differ With Endometrial Classification?

“…A preliminary work on Masson's trichrome-stained histological sections of jenny endometrium classified as I, IIA, or IIB was not conclusive about putative differences in the total area occupied by COL fibers ( 34 ). In contrast, in the mare, COL3 was the most predominant type of collagen in healthy endometrium, in comparison to severe endometriosis where COL1 was mostly found ( 10 ).…”

“…In tissue repair, collagen type III (COL3) is the first one to be expressed, being replaced by collagen type I (COL1) in later stages of fibrogenesis (9). Nevertheless, in the mare endometrium at the transcript level, age appeared not to influence COL1 or COL3 mRNA (10). In contrast, quantification of the areas in the endometrium occupied by COL1 and COL3, stained with histochemical picrosirius red staining and visualized by polarized light microscopy (11,12), showed an increase in COL1 in the tissues with severe endometriosis, in comparison to healthy endometria or with mild fibrotic changes, where COL3 was the most predominant type (10).…”

“…A preliminary work on Masson's trichrome-stained histological sections of jenny endometrium classified as I, IIA, or IIB was not conclusive about putative differences in the total area occupied by COL fibers (34). In contrast, in the mare, COL3 was the most predominant type of collagen in healthy endometrium, in comparison to severe endometriosis where COL1 was mostly found (10). Interestingly, when evaluating the topographic histological distribution of COL1 and COL3 in jenny's endometrium, a different pattern was consistent, despite the histopathological classification and the progress of fibrosis.…”

“…Nevertheless, in the mare endometrium at the transcript level, age appeared not to influence COL1 or COL3 mRNA ( 10 ). In contrast, quantification of the areas in the endometrium occupied by COL1 and COL3, stained with histochemical picrosirius red staining and visualized by polarized light microscopy ( 11 , 12 ), showed an increase in COL1 in the tissues with severe endometriosis, in comparison to healthy endometria or with mild fibrotic changes, where COL3 was the most predominant type ( 10 ). A previous morphometric analysis of periglandular fibrosis in equine endometria using picrosirius red also referred a predominance of COL1 in severe endometriosis ( 13 ).…”

Collagen and Microvascularization in Placentas From Young and Older Mares

“…Aging of the mares has been related to increased fibrosis in the endometrium ( 15 , 16 ), and oviduct ( 17 ), and several pathological alterations in the placenta ( 13 , 18 ). In fact, during mare gestation, besides morphological alterations, and degenerative changes in the microplacentomes on the surface of the mare placenta, also the development of fetal and maternal capillary beds within each microplacentome is diminished, disturbing physical and hematological contact at the fetomaternal interface, and hence impairing fetal growth ( 13 , 18 ).…”