Involvement of apoptosis during deciduomal regression in pseudopregnant hamsters effect of progesterone

Menstrual-like breakdown and apoptosis in human endometrial explants

BACKGROUND

Apoptosis occurs in late secretory and menstrual human endometrium and is thought to play an important role in endometrial physiology. Menstrual-like breakdown has been observed in vitro in endometrial explants. The purpose of this study was to assess the role of apoptosis in menstrual-like breakdown in human endometrial explants.

METHODS

Human endometrial tissue was obtained during the mid-secretory phase and cultured with or without estrogen and progesterone. The occurrence of breakdown was assessed by histology. Apoptosis was determined by gel electrophoresis for the detection of DNA fragmentation and by immunohistochemistry using the M30 CytoDEATH and anti-cleaved caspase-3 (CASP3) antibodies for the detection of caspase activity. Expression of BCL2 and BAX was quantified using real-time PCR analysis.

RESULTS

Apoptosis occurred in human endometrial explants at all time-points studied. Cleaved CASP3 and M30 antigen expression increased in all explants, suggesting the involvement of CASP3 in the apoptosis. Low BCL2:BAX ratios were observed in all samples when compared with pre-culture controls. Estradiol and progesterone supplementation of the culture media reduced or eliminated menstrual-like breakdown but did not affect the degree of apoptosis observed.

CONCLUSIONS

The apoptosis observed in endometrium during the late secretory phase and menstrual phase does not appear to be mechanistically related to the tissue breakdown but rather may be involved in the impending remodelling that occurs in the endometrium in the transition from secretory to proliferative phase following the menses.

Human chorionic gonadotropin contributes to maternal immunotolerance and endometrial apoptosis by regulating Fas-Fas ligand system

The first known hormonal signal of the conceptus during implantation is human chorionic gonadotropin (hCG). Interestingly, increased apoptosis in human endometrium coincides with the implantation window. Factors from the fetal or placental origin as well as maternal hormonal factors are likely to have a potential role in the regulation of apoptotic signaling molecules. We hypothesized that hCG may be a placental link for the development of local maternal immunotolerance. Fas-Fas ligand (FasL) system is one of the apoptotic signaling pathways, shown to be important in the development of local immune tolerance during and after implantation. We report that hCG treatment decreases cell proliferation and increases apoptosis in endometrial cells. Moreover, hCG stimulates FasL mRNA and protein expression without affecting Fas mRNA in these cells. Interestingly, in coculture experiments, hCG-treated endometrial cells induce an increase in T cell apoptosis. Our in vivo results reveal that cells of early pregnancy decidua express strong FasL immunoreactivity, and decidual areas containing interstitial cytotrophoblasts have numerous TUNEL-positive cells. Compared with decidual areas devoid of interstitial cytotrophoblasts, we observed in decidual areas containing interstitial cytotrophoblasts clearly less amount of TUNEL-positive cells. These results suggest that hCG may be a link in the development of peritrophoblastic immune tolerance and may facilitate the trophoblast invasion by regulating proapoptotic molecules such as FasL in endometrial cells.

Expression of apoptosis in placentae from mice lacking the prostaglandin F receptor

This study aimed to investigate the changes in apoptosis in the placenta and decidua of pregnant mice lacking the prostaglandin F receptor. Mouse placentae were removed from fetuses on days 10-23 of pregnancy. Apoptotic cells were examined by a DNA fragmentation assay and the terminal deoxynucleotidyl transferase-mediated dUDP nick end-labelling (TUNEL) technique. The placenta and decidual weight increased before day 18 and 14 of pregnancy, and then decreased with gestational day. After day 19, the fetuses gradually died in the uterus. All fetuses died in the uterus on day 23 of pregnancy. The number of apoptosis was not significantly different between wild type and FP-deficient mice before day 18 of pregnancy by DNA fragmentation and TUNEL staining. The DNA fragmentation was always more pronounced in decidual tissue on each day of pregnancy. DNA laddering on placentae was more extensive on day 22 than day 18. In placenta, most TUNEL-positive cells were detected in trophoblast and stromal cells. A higher intensity of apoptotic cells was in the decidual basalis. The main area was the centre of the decidual basalis, and was in decrease toward to margin of placenta. The index of TUNEL positive cells increased as gestation progressed toward termination. Especially, it was prominent in the placentae on day 22 compared with that day 18 of pregnancy. The increased TUNEL-positive staining in syncytiotrophoblast surface was found in placenta at post-term, compared with those at term. Apoptosis may provide insights into both normal placental development and placental dysfunction during an abnormal pregnancy from post-term pregnancy.