Introduction: Expression of murine CSP-1/Dcpp secretory proteins was first identified in sublingual salivary glands and subsequently in secretory epithelia of several other tissues, including the mouse female reproductive tract where expression is regulated by oestrogen. Preliminary studies indicated that HRPE773, the human CSP-1/Dcpp orthologue, displayed a similar pattern of expression to its murine counterparts. We therefore hypothesized that HRPE773 might be expressed in human endometrium and uterine decidua under the influence of steroid hormones.
Methods: Timed endometrial biopsies were collected with informed consent from patients undergoing elective hysterectomy or investigation for benign gynaecological conditions and during spontaneous miscarriage or termination of pregnancy. Quantitative Real-Time PCR and immunohistochemistry were used to determine HRPE773 mRNA levels and protein localization. HRPE773 expression was also measured in telomerase-immortalized human endometrial epithelial cells (hTERT-EECs) treated with oestradiol, medroxyprogesterone acetate (MPA), or both oestradiol and MPA for 8 and 24 h at physiological doses. Statistical analyses were performed using the KruskalWallis test (CI 95%) with appropriate post hoc testing.
Results: HRPE773 was expressed in human endometrium in all phases of the menstrual cycle, but was significantly higher in the early-secretory phase compared to proliferative, mid-secretory, late-secretory or menstrual phases, while decidual expression was elevated in women with miscarriage, but not in extra-uterine (tubal) or viable intrauterine termination of pregnancy. HRPE773 immunoreactivity was located primarily in the cytoplasm of endometrial luminal and glandular epithelia, with some staining also in stromal cells. HRPE773 mRNA levels in hTERT-EECs treated with oestradiol alone and both oestradiol and MPA was significantly lower after 24 h compared to vehicle.
Conclusion: HRPE773 expression is elevated in endometrial luminal and glandular epithelia during the early secretory phase of the menstrual cycle and in uterine decidua following miscarriage, while cell culture experiments suggest that HRPE773 expression is likely to be inhibited by oestrogen.