Progesterone and interferon tau-regulated genes in the ovine uterine endometrium: identification of periostin as a potential mediator of conceptus elongation.

During early pregnancy in ruminants, progesterone (P(4)) and interferon tau (IFNT) act on the endometrium to regulate genes hypothesized to be important for conceptus development and implantation. The present study was conducted to verify several candidate genes (actin alpha-2, smooth muscle, aorta (ACTA2), collagen, type III, alpha-1 (COL3A1), periostin (POSTN), secreted protein acidic cysteine-rich (SPARC), S100 calcium-binding protein A2 (S100A2), STAT5A and transgelin (TAGLN)) regulated by pregnancy, P(4), and/or IFNT in the endometrium determined using a custom ovine cDNA array. S100A2 mRNA was detected primarily in endometrial epithelia and conceptuses. S100A2 mRNA increased in endometrial epithelia from days 10 to 16 in cyclic ewes and from days 10 to 14 in pregnant ewes and declined thereafter. The abundance of S100A2 mRNA was less in endometrial luminal epithelium of IFNT-infused ewes receiving P(4). Expression of COL3A1, SPARC, ACTA2, and TAGLN was independent of pregnancy, P(4), or IFNT. POSTN mRNA was detected primarily in compact stroma of intercaruncular and caruncular endometria, but not in the conceptus. Endometrial POSTN mRNA increased between days 12 and 14 in pregnant but not cyclic ewes, and POSTN mRNA was more abundant in uterine stroma of ewes treated with P(4). POSTN protein was detected in uterine flushings of pregnant ewes and found to mediate attachment and stimulate migration of ovine trophectoderm cells in vitro. These results support the ideas that POSTN and S100A2 are regulated by P(4) and IFNT respectively, and that POSTN is involved in conceptus elongation during early pregnancy.