Assisted hatching (AH), which is known to improve the hatching potential of mammalian embryos, has been used to increase the pregnancy rate in in vitro fertilization cycles. However, the effect of AH on a trypsin-like protease, which is known to be associated with the hatching process, has not been studied. In this study, we evaluate whether the intactness of zona pellucida affects the secretion of a trypsin-like protease from mouse blastocyst. Four- to 8-cell stage mouse embryos were collected at 66- to 68 hr after hCG injection and divided into 3 groups according to the manipulation of zona pellucida. The groups are no treatment (control), drilling of zona pellucida (ZD) and thinning of zona pellucida (ZT). The activity of a trypsin-like protease, blastocyst development and hatching rate were compared among the three groups at 110 and 135 hr after hCG injection, respectively. The protease activity and blastocyst development were not significantly different among control, ZD and ZT groups at 110 and 135 hr after hCG injection, respectively. However, the hatching rate of ZD and ZT groups was significantly higher than that of control group at each time, respectively (p>0.001). Even in the zona pellucida removed embryos, the protease activity did not differ from the control group. In conclusion, the secretion of a trypsin-like protease from mouse blastocyst does not seem to be affected by the intactness of zona pellucida.
Animal ; Blastocyst/secretion ; Blastocyst/enzymology* ; Female ; Fertilization in Vitro/methods ; Gonadotropins, Chorionic/pharmacology ; Mice ; Mice, Inbred C57BL ; Mice, Inbred CBA ; Pregnancy ; Serine Endopeptidases/secretion ; Serine Endopeptidases/metabolism* ; Zona Pellucida/physiology* ; Zona Pellucida/drug effects

OBJECTIVETo investigate the effects of mouse preimplantation embryos on the expressions of DNA methyltransferase 1(Dnmt1) of mouse oviduct epithelial cells.

METHODSThe histological location of Dnmt1 protein was detected by immunohistochemical staining and the expression levels of Dnmt1 mRNA and protein in mouse oviduct were assayed by real-time reverse transcription-PCR(RT-PCR) and Western blotting in both pregnant and pseudopregnant mice at the 2-cell, 4-cell and 8-cell stages.

RESULTSThe expressions of Dnmt1 protein were mainly located in the epithelial cells of mouse oviduct. It was found that during all three stages, the expression levels of Dnmt1 mRNA in the epithelial cells of the pregnant mice were significantly lower than those in the pseudopregnant mice (P< 0.05), and the level of Dnmt1 protein expression in the pregnant mice was significantly decreased as compared with that in pseudopregnant mice at the 4-cell stage.

CONCLUSIONExpressions of both Dnmt1 mRNA and protein in the epithelial cells of mouse oviduct could be regulated by mouse preimplantation embryos, which might play an important role in the expression changes of some genes in oviduct epithelial cells during the preimplantation period.

Animals ; Blastocyst ; physiology ; Blotting, Western ; DNA (Cytosine-5-)-Methyltransferase 1 ; DNA (Cytosine-5-)-Methyltransferases ; genetics ; metabolism ; Epithelial Cells ; cytology ; enzymology ; metabolism ; Female ; Gene Expression ; Immunohistochemistry ; Male ; Mice ; Mice, Inbred ICR ; Oviducts ; cytology ; Random Allocation ; Reverse Transcriptase Polymerase Chain Reaction