Cellular and molecular mechanisms involved in placental separation in the bovine: A review

Abstract

SUMMARYRetention of fetal membranes (RFM), where the fetal placenta is not expelled within 8À12 hr after calving, lowers bovine productivity and fertility, resulting in significant economic loss to the dairy industry. Several risk factors that predispose an individual to RFM are known, but a unifying pathogenesis remains elusive due to its multifactorial etiology. Fetal membrane separation and expulsion after parturition involves structural and immunological changes of the bovine placentome that are governed predominantly by steroid hormones and the prostaglandin milieu of late pregnancy and parturition. Maturation of the placentome, a gradual and concerted event of late gestation, is likely initiated by the up-regulation of fetal major histocompatibility complex class I in the interplacentomal regionÀ Àwhich increases the apoptosis of binucleate and other trophoblastic cells, the degradation of collagen in the extracellular matrix by matrix metalloproteinases, and an influx of phagocytic leukocytes. Shear force further distorts the crypt architecture of the mature placentomes when they are forced against the fetus during the second stage of labor. Cotyledon dehiscence from the caruncular crypts is completed following fetal expulsion as a result of acute shrinkage of the cotelydonary villi as well as reduced perfusion to the caruncle; the secundinae is expelled by uterine contractions. A better understanding of placentomal maturation, intra-partum, and immediate postpartum changes of the placentome should help develop strategies for the treatment and prevention of RFM. The present review proposes a model of placentome maturation and separation of fetal membranes in the dairy cow. We hypothesize that the increased estrogen-toprogesterone ratio facilitates [an] MHC-I-dependent inflammatory response, thus driving the process of placentome maturation.

Gamma/Delta T Cells in the Course of Healthy Human Pregnancy: Cytotoxic Potential and the Tendency of CD8 Expression Make CD56+ γδT Cells a Unique Lymphocyte Subset

“…Besides the regulatory aspect of γδT cells, their cytotoxic potential and its regulation could also be essential for heathy pregnancy. A basic level of cytotoxicity seems necessary for defense against pathogens and tissue remodeling ( 62 ). On the contrary, cytotoxicity against the fetus must be prevented.…”

Expression of C–C motif chemokines and their receptors in bovine placentomes at spontaneous and induced parturition

“…R etained fetal membrane (RFM) in cows, defined as the fetal membrane still present at least 12 h postpartum, occurs in approximately 5-15% of the pregnant cows and is associated with reduced fertility and milk production [1]. Degradation of the extracellular matrix (ECM) is involved in tissue remodeling during placental separation in the postpartum uterus [2]. Several studies have suggested that matrix metalloproteinase (MMP) 2 and MMP9 possess collagenase activity and play essential roles in the detachment of the fetal membrane from the caruncle [3,4].…”

Serum Biochemical Investigations on Retained Placenta in Egyptian Buffaloes

“…The normal sequence of parturition is influenced by number of endocrine and paracrine factors. It begins with gradual decrease of placental P 4 concentration and increased production of E 2 hormone where E 2 has a vital role in the growth of placentomes and PG release (Attupuram et al, 2016). The role of albumin during normal parturition occupies huge significance as it is a source of endogenous amino acids which are required postpartum (Bhat et al, 2018).…”

“…Moreover, RP is associated with imbalances in E 2 and P 4 levels. High P 4 and low E 2 levels were occurred due to failure of the placenta to produce sufficient amounts of cytochrome P450 aromatase enzyme which has a role in catalyzing the rate limiting step in E 2 biosynthesis (Attupuram et al, 2016). Further, lower levels of IL-6 in RP syndrome affected buffaloes may lead to reduction in the expression of Cyp19 gene which encodes cytochrome P450 aromatase enzyme so; inadequate E 2 production will be happened leading to the formation of undeveloped placentomes which aren't expelled out naturally causing RP (Ghai et al, 2012).…”