Mineralised deposits in the uterine glands of mares with chronic endometrial degeneration

Chronic degenerative disease of the mare's endometrium is characterised by changes in the uterine glands, including cystic dilation, hyperplasia and periglandular fibrosis. Endometrial biopsies were taken from 23 mares with different grades of endometrial degeneration. Solid structures were identified within the lumina of the uterine glands and shown to be calcified by histochemical staining. Most of them were not homogenous but composed of a mixture of mineral and organic substances. Further examinations of these mineralised structures by immunohistochemical methods revealed the presence of the non-collagenous matrix proteins osteopontin, osteonectin and bone sialoprotein, which are known to be involved in calcification processes such as urolithiosis. Osteopontin and bone sialoprotein were identified within the calculi, frequently arranged in concentric layers. Osteonectin was the only matrix protein that was also present in the glandular epithelium. Osteocalcin was not found in either the calculi or the glandular epithelial cells.