Abstract
The aim of the present study was to determine the possible roles of chemokines in regulating bovine endometrial function during early pregnancy. The expression of six chemokines, including CCL2, CCL8, CCL11, CCL14, CCL16, and CXCL10, was higher in the endometrium at 15 and 18 days of pregnancy than at the same days in non-pregnant animals. Immunohistochemical staining showed that chemokine receptors (CCR1, CCR2, CCR3, and CXCR3) were expressed in the epithelial cells and glandular epithelial cells of the bovine endometrium as well as in the fetal trophoblast obtained from a cow on day 18 of pregnancy. The addition of interferon-τ (IFNT) to an endometrial tissue culture system increased CCL8 and CXCL10 expression in the tissues, but did not affect CCL2, CCL11, and CCL16 expression. CCL14 expression by these tissues was inhibited by IFNT. CCL16, but not other chemokines, clearly stimulated interferon-stimulated gene 15 (ISG15) and myxovirus-resistance gene 1 (MX1) expression in these tissues. Cyclooxygenase 2 (COX2) expression decreased after stimulation with CCL8 and CCL14, and oxytocin receptor (OTR) expression was decreased by CCL2, CCL8, CCL14, and CXCL10. Collectively, the expression of chemokine genes is increased in the endometrium during early pregnancy. These genes may contribute to the regulation of endometrial function by inhibiting COX2 and OTR expression, subsequently decreasing prostaglandin production and preventing luteolysis in cows.
Highlights
The establishment of pregnancy is the result of successful communication between the conceptus and the maternal endometrium
Microarray analysis detected 344 and 1336 differentially expressed genes in the bovine endometrium at 15 and 18 days of pregnancy compared with the same days in non-pregnant cows (>2-fold change; p < 0.05)
Transcripts of CCL2, CCL8, CCL14, CCL16, and CXCL10 were more abundant in the endometrium at day 15 of pregnancy than at day 15 in non-pregnant cows (Figure 1; p < 0.05)
Summary
The establishment of pregnancy is the result of successful communication between the conceptus and the maternal endometrium. The corpus luteum (CL) remains functional and the dynamics of prostaglandin (PG) F2α secretion from uterus in early pregnancy changes from that in the comparable stages of the estrous cycle [1,2,3]. At the time of recognition of pregnancy, the bovine conceptus produces interferon-τ (IFNT) to prevent luteolysis, which is induced by a pulsatile release of PGF2α from the uterus [2,3]. The physiological roles of these pregnancy-dependently regulated genes in the mechanism of maternal recognition are not yet fully understood. Understanding the role of the fetal-maternal interaction during early pregnancy might help to determine a way to improve reproductive efficiency and alleviate deficiencies
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