Puerperal involution in the mare - A comparison of clinical signs and pathology

Abstract

A detailed morphological and functional description of equine endometrial involution is necessary for the understanding of alterations leading to a reduced fertility rate following peripartal disturbances. A complete involution of the microcaruncles, glands and stroma by the 9th day post parturition and the return to cyclical activity is essential for an early post partal pregnancy. After normal parturition, a loss of the glandular cytokeratin-expression, the absence of laminin in the glandular basal lamina and an intraepithelial expression of vimentin occurs especially on the 3rd and 6th day post partum (p.p.). The expression of estrogen receptors and progesterone receptors of intact glandular epithelial cells decreases from the 3rd to the 6th day p.p. and increases from the 6th to 9th day p.p.. Decreased fertility rate in the first post-partum heats in mares with dystocia or retained placental delivery may be due to a higher incidence of periglandular fibrosis and a disturbed glandular redifferentiation, which is characterized by a delayed inset of epithelial cytokeratin-expression and an unphysiological expression of the hormone receptors. Moreover, in mares with dystocia a disturbed microcaruncular involution may contribute to the decreased conception rate.