Differential expression and regulation of angiopoietin-3 in mouse uterus during preimplantation period.

Angiogenesis is necessary for successful implantation and decidualization. This study was to investigate the differential expression of angiopoietin-3 (Ang-3) in mouse uterus during early pregnancy and its regulation by steroid hormones using in situ hybridization and reverse transcription polymerase chain reaction (RT-PCR). There was no detectable Ang-3 mRNA signal on days 1-5 of pregnancy by in situ hybridization. On day 6 of pregnancy, a low level of Ang-3 mRNA signal was seen in the primary decidua. Ang-3 mRNA expression gradually increased on days 7 and 8 of pregnancy along with the development of decidua, and its expression scope was also expanded. The RT-PCR result indicated that Ang-3 mRNA expression was low on days 1-4 of pregnancy. On day 5, as embryo implanted, Ang-3 mRNA was highly expressed in mouse uterus, and the expression gradually increased on days 6-8 of pregnancy, with peak level on day 8 of pregnancy. Similarly, Ang-3 mRNA was also strongly expressed in decidualized cells under artificial decidualization. Compared with the delayed uterus, a high level of Ang-3 mRNA expression was detected in activated implantation uterus by RT-PCR. In the ovariectomized mouse uterus, Ang-3 mRNA expression increased and reached the highest level at 12 hr after injection of estrogen, progesterone, and estrogen plus progesterone, respectively. These results suggest that Ang-3 may play an important role during the process of mouse decidualization. Both estrogen and progesterone can induce the expression of Ang-3 in ovariectomized mouse uterus.