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  • Fletcher Hauge posted an update 3 months ago

    Mplantation period. IFN (IFNT) is unique to ruminants and has been identified as their conceptus’ signal for maternal recognition of pregnancy. Besides, IFNs are involved in the regulation of uterine receptivity, decidualization, as well as placental growth and development. They induce the expression of IFNstimulated genes in the uterus in a temporal and cellspecific manner [70]. IFN (IFND) has been demonstrated not only in pigs [79], but also in horses [80]. In this species, two IFND genes have been identified and are expressed between days 16 and 22 of pregnancy. This suggests involvement of IFND jasp.12117 in conceptus-maternal interactions in the horse, but the expression occurs beyond the time of maternal recognition of pregnancy. Duration of the pre-implantation period varies considerably among species, but is prolonged in the horse. The outer trophoblast layer of the allantochorion finally establishes a stable, microvillous contact with the luminal epithelium of the endometrium around days 40 to 42 and placentation commences thereafter [81]. Before placentation, the equine conceptus is completely dependent on nutritional support by histotroph secreted from the luminal epithelium and the endometrial glands [82]. Histotroph is produced in all mammalian uteri and consists of a complex mixture of proteins and molecules. Its production depends on progesterone action and ?in sheep has been demonstrated to be IFNT-stimulated [6, 70]. At the Nisms and features ?some of them quite unique among domestic animals blastocyst stage, the energy substrate for mammalian conceptuses switches from pyruvate to glucose. In sheep, concentrations of glucose and the amino acids arginine, leucine and glutamine increase in the uterine lumen between days 10 and 15 of pregnancy. This is paralleled by increased expression of specific transporters of those nutrients in the uterine epithelia. These changes are indispensable for the survival and development of the conceptus [6]. The same level of knowledge does not exist for the horse so far. However, changes at the mRNA level of the maternal endometrium during equine early pregnancy have been investigated utilizing microarray techniques. Pronounced changes occurred around the time of recognition of pregnancy. A high proportion of genes with altered transcription is regulated by estrogens, progesterone or PGE2. It is thus feasible that in the mare changes in mRNA abundance are also directly related to maternal progesterone secretion and/or conceptus-derived factorsAurich and Budik Journal of Animal Science and Biotechnology (2015) 6:Page 6 ofsuch as estrogens or PGE2. Because several of the affected genes are also involved in regulation of early gestation in species other than the horse it is suggested that a subset of genes crucial to endometrial receptivity is highly conserved among species [83, 84]. The importance of progesterone for histotroph production and maintenance of pregnancy in j.jebo.2013.04.005 the horse has been long emphasized (reviewed by Sharp 2000). Similar to ruminants, a pronounced rise in progestins during the early post-ovulatory phase in pregnant mares contributes to improved development of the conceptus [45, 85] while deprivation of progesterone due to luteolysis leads to immediate changes in endometrial protein secretion [86]. Among others retinol binding protein [87], uteroferrin [88], uterocalin [82] and SLC36A2 (solute carrier family 36 (proton/amino acid symporter), member 2) [83] have been suggested to be of significance for maintenance of early pregnancy in the horse. Uterocal.