174 EPIDERMAL GROWTH FACTORS AND CALBINDIN-D9k GENE EXPRESSIONS DURING PREGANCY IN THE PORCINE UTERUS

Abstract

To stably maintain pregnancy, several genes are expressed in the uterus. In particular, the endometrial expression of genes encoding growth factors appears to play a key role in maternal–fetal communication. Previous studies have characterized the endometrial expression kinetics of the genes encoding epidermal growth factor (EGF), its receptor (EGFR), transforming growth factor-alpha (TGF-α), amphiregulin (Areg), heparin-binding (Hb) EGF, and calbindin-D9k (CaBP-9k) in the pig during implantation. Here, we further characterized the expression patterns of these molecules during the entire porcine pregnancy. Porcine (n = 3 per PD) were collected at pregnancy days (PD) 12, 15, 30, 60, 90, and 110 and subjected to semi-quantitative RT-PCR. The data were analyzed with a nonparametric one-way analysis of variance using the Kruskal-Wallis test, followed by Dunnett's test for multiple comparisons to the negative control. EGF and EGFR showed similar expression patterns, being highly expressed around implantation time and then disappearing. TGF-α and Areg expression levels rose steadily until they peaked at PD30, after which they gradually decreased to PD12 levels. The Areg mRNA expression pattern was confirmed by real-time PCR, and similar Areg protein expression patterns were observed. Immunohistochemical analysis of PD60 uteri revealed Areg in the glandular and luminal epithelial cells. Hb-EGF was steadily expressed throughout the entire pregnancy while CaBP-9k was expressed strongly on PD12, and then declined sharply in PD15 before recovering slightly for the remainder of the pregnancy. Thus, the EGF family may play a key role during implantation in pigs. In addition, CaBP-9k may help maintain uterine quiescence during pregnancy by sequestering cytoplasmic Ca²⁺.