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Abstract
Embryo transport and embryo implantation are essential events in mammalian reproduction during pregnancy. This dissertation was conducted to investigate the effect of bisphenol A (BPA) on early pregnancy and the molecular mechanism (s) of embryo transport and embryo implantation. Timed pregnant female mice were treated subcutaneously with 0, 0.025, 0.5, 10, 40, and 100 mg/kg/day BPA from gestation day 0.5 (D0.5, mating night as D0) to D3.5. High dose of preimplantation BPA exposure resulted in delayed embryo transport and preimplantation embryo development, and delayed/failed embryo implantation, indicating the adverse effect of BPA on early pregnancy. Preimplantation 17-estradiol (E2) exposure at 1 and 10 g/kg/day from D0.5 to D2.5 delayed embryo transport in the ampulla-isthmus junction of oviduct in mice, which is associated with the oviductal epithelium hyperplasia. Microarray analysis revealed 53 differentially expressed genes in the oviduct upon 10 g/kg/day E2 treatment, which may have potential function in embryo transport regulation. Embryo implantation is a process that the receptive uterus accepts an embryo to implant into the uterine wall. Microarray analysis of the preimplantation D3.5 and postimplantation D4.5 uterine luminal epithelium (LE) identified 627 differentially expressed genes and 21 significantly changed signaling pathways upon embryo implantation. 12 of these genes were newly characterized and showed spatiotemporal expression patterns in the mouse periimplantation uterine LE. The most upregulated gene in the D4.5 LE Atp6v0d2 (34.7x) is a subunit of vacuolar-type H+-ATPase (V-ATPase) that regulates the cell acidification through ATP hydrolysis and proton translocation. LE acidification was significantly increased upon embryo implantation on D4.5 which was parallel with the differential expression pattern of Atp6v0d2. The V-ATPase inhibitor bafilomycin A1 inhibited embryo implantation and decreased LE acidification, indicating the critical role of LE acidification in embryo implantation. The most downregulated gene in the D4.5 LE N-acetylneuraminate pyruvate lyase (Npl) (35.4x) is highly expressed in D2.5 and D3.5 uterine LE, and was significantly decreased on D4.5. This spatiotemporal expression pattern of Npl is progesterone receptor mediated. However, Npl mutant females showed normal embryo implantation and fertility, indicating the dispensable role of Npl in female reproduction.