Spencer Thomas E, Johnson Greg A, Bazer Fuller W, Burghardt Robert C, Palmarini Massimo
Center for Animal Biotechnology andGenomics, Department of Animal Science, Texas A&M University, College Station, TX 77843, USA.
Reprod Fertil Dev. 2007;19(1):65-78. doi: 10.1071/rd06102.
The present review highlights new information on pregnancy recognition and conceptus development and implantation in sheep with respect to regulation by progesterone, interferons and endogenous retroviruses. After formation of the corpus luteum, progesterone acts on the endometrium and stimulates blastocyst growth and elongation to a filamentous conceptus (embryo/fetus and associated extra-embryonic membranes). The envelope of endogenous retroviruses related to Jaagsiekte sheep retroviruses appears to intrinsically regulate mononuclear trophectoderm cell proliferation and differentiation into trophoblast giant binucleate cells. The mononuclear trophectoderm cells of elongating sheep conceptuses secrete interferon-tau, which acts on the endometrium to prevent development of the luteolytic mechanism by inhibiting transcription of the gene for the oestrogen receptor alpha in the luminal and superficial ductal glandular epithelia. These actions prevent oestrogen-induced transcription of the oxytocin receptor gene and, therefore, oxytocin-induced luteolytic pulses of prostaglandin F2alpha. Progesterone down regulation of its receptors in luminal and glandular epithelia correlates temporally with a reduction in anti-adhesive mucin land induction of secreted galectin 15 (LGALSI5) and secreted phosphoprotein 1, which are proposed to regulate trophectoderm proliferation and adhesion. Interferon-c acts on the endometrial lumenal epithelium to induce WNT7A and to stimulate LGALS 15, cathepsin L and cystatin C, which are candidate regulators of conceptus development and implantation. The number of potential contributors to maternal recognition and establishment of pregnancy continues to grow and this highlights our limited appreciation of the complexity of the key molecules and signal transduction pathways that intersect during these key developmental processes. The goal of improving reproductive efficiency by preventing embryonic losses that occur during the peri-implantation period of pregnancy in domestic ruminants provides the challenge to increase our knowledge of endometrial function and conceptus development.
本综述着重介绍了绵羊妊娠识别、孕体发育和着床方面的新信息，涉及孕酮、干扰素和内源性逆转录病毒的调控作用。黄体形成后，孕酮作用于子宫内膜，刺激囊胚生长并伸长为丝状孕体（胚胎/胎儿及相关的胚外膜）。与绵羊肺腺瘤逆转录病毒相关的内源性逆转录病毒包膜似乎内在地调节单核滋养外胚层细胞增殖并分化为滋养层巨双核细胞。伸长的绵羊孕体的单核滋养外胚层细胞分泌干扰素 -τ，它作用于子宫内膜，通过抑制腔上皮和浅表导管腺上皮中雌激素受体α基因的转录来阻止黄体溶解机制的发展。这些作用可防止雌激素诱导的催产素受体基因转录，从而防止催产素诱导的前列腺素F2α黄体溶解脉冲。孕酮下调其在腔上皮和腺上皮中的受体，这在时间上与抗粘附粘蛋白1的减少以及分泌型半乳糖凝集素15（LGALSI5）和分泌型磷蛋白1的诱导相关，它们被认为可调节滋养外胚层的增殖和粘附。干扰素 -γ作用于子宫内膜腔上皮，诱导WNT7A并刺激LGALS 15、组织蛋白酶L和胱抑素C，它们是孕体发育和着床的候选调节因子。对母体识别和妊娠建立有潜在作用的因素数量不断增加，这凸显了我们对这些关键发育过程中相互交叉的关键分子和信号转导途径复杂性的认识有限。通过防止家畜反刍动物妊娠植入前期发生的胚胎损失来提高繁殖效率的目标，对增加我们对子宫内膜功能和孕体发育的了解提出了挑战。
