Gonadotropin Stimulation May Not Affect the Expression of Heparin-Binding Epidermal Growth Factor-Like Growth Factor in the Murine Endometrium

Abstract

Background: Present human data reveal that gonadotropin stimulation for in vitro fertilization and embryo transfer (IVF-ET) is detrimental to uterine receptivity. Heparin-binding epidermal growth factor-like growth factor (HB-EGF) is important in the early stage of mouse embryonic implantation since it is expressed in the murine endometrium before the attachment reaction. Gonadotropin receptors have been found on the murine endometrium. In this study, we assessed the expression of HB-EGF mRNA on the gonadotropin-stimulated murine endometrium and sought evidence of whether the gonadotropin-induced, altered uterine receptivity is associated with a change in the HB-EGF expression. Methods: Quantitative, competitive reverse-transcription polymerase chain reaction (PCR) and immunohistochemistry were performed to evaluate the expression of HB-EGF mRNA on the stimulated murine endometrium from pregnant uteri of gestation day (g.d.) 5.0 after injection of saline, or pregnant mare serum gonadotropin (PMSG) 5 or 10 IU. Results: The expression of HB-EGF mRNA showed no significant increase or decrease in the endometrial expression in PMSG groups, compared to the control group (natural coitus with saline injection), on g.d. 5.0. This finding was consistent with the immunostaining of HB-EGF protein, and there was no significant difference in the staining intensity among the 3 groups. Conclusion: This study reveals that ovarian stimulation by gonadotropin may not influence the expression of HB-EGF in the murine endometrium. Further investigations are necessary to elucidate whether embryonic HB-EGF receptor status relative to endometrial HB-EGF expression is affected by ovarian stimulation.