166 DIFFERENTIAL EXPRESSION OF AMPHIREGULINE, EPIDERMAL GROWTH FACTOR, AND CALBINDIN-D9k IN THE UTERUS OF RODENTS AND PIGS DURING IMPLANTATION

Abstract

Implantation in mammalian species is a complex process that involves embryo apposition and attachment to the apical surface of the uterine epithelium. This process involves a variant of molecules that are not unique in themselves but play unique roles in the process of implantation. Among them, the epidermal growth factor (EGF) family, the cytokines, cell adhesion molecules, and calcium-binding proteins appear to be important in embryonic attachment. Amphireguline (Areg), its receptor (EGFR), and calbindin-D9k (CaBP-9k) were highly expressed before implantation. Thus, in the present study, using rodent and porcine models, the expression levels of Areg, EGFR, and CaBP-9k gene were analyzed in the uterus during the estrous cycle and pregnancy by means of RT-PCR to elucidate their roles in implantation. Areg and CaBP-9k were significantly up-regulated at diestrus; however, these transcripts disappeared at proestrus in mice. In addition, EGFR mRNA was primarily observed at diestrus in mice. Although CaBP-9k and EGFR transcripts of rats increased at proestrus, no Areg mRNA was observed in this model. To clarify the regulator of the mouse Areg gene, immature mice were injected with sex steroid hormones. No transcripts of Areg were detected in these models, suggesting that mouse Areg may require other puberty factors. Porcine expressions of uterine Areg, EGFR, and CaBP-9k mRNA fluctuated during pregnancy (Days 12, 15, 30, 60, 90, and 110 of pregnancy). CaBP-9k transcripts were highly expressed on Day 12 and decreased on Days 15 to 90. On Day 110, CaBP-9k mRNA was expressed as well. Areg mRNA increased on Days 12 to 30, and decreased on Days 30 to 110. EGFR transcripts were detected on Day 12 and gradually disappeared till the end of pregnancy. Uterine Areg and CaBP-9k mRNAs were regulated by progesterone (P4) in the mouse model. Areg transcripts of porcine uteri appear to be expressed after implantation, but CaBP-9k mRNA was induced before embryo attachment. Taken together, these results indicate taht uterine Areg, EGFR, and CaBP-9k are differentially regulated during pregnancy in these species, and porcine CaBP-9k could act as an important factor in implantation. A further spatial expression of these genes will contribute to the understanding of their complex molecular actions involved in embryo attachment.