抄録
Whereas there are many hypotheses on the causes of senescence of the body, it has not yet been elucidated whether the placenta, which is to be delivered from the mother after pregnancy for ten months, is also subjected to senescent changes. Namely, is the senescence already started in the placenta of late pregnancy, as it is a matured placenta?
In this paper, a gene, early population doubling level cDNA-1/pigment epithelium-derived factor(EPC-1/PEDF), was used as a marker to examine senescent changes. This gene has already been used as an ageing marker for tissues although its expression level is fluctuated according to cell cycle, ageing, cell differentiation, etc. We noticed that, when the expression of EPC-1/PEDF mRNA was detected by RT-PCR, its level was decreasing in the placenta of pregnant mice as pregnancy progressed. Next we performed real-time quantitative PCR to detect EPC-1/PEDF mRNA in 19 cases of human placentas at 27-40 weeks of gestation, obtained upon elective cesarean deliveries done prior to the onset of labor. Its expression was decreased as pregnancy progressed. The 8 cases of vaginal delivery and the 5 cases of emergency cesarean deliveries after onset of labor gave lower values than the cases subjected to elective cesarean delivery. In cases of 8 dizygotic twins pregnancy at 32-38 weeks of gestation including two cases of discordant twins, the expression of EPC-1/PEDF mRNA was detected by real-time quantitative PCR. The placentae from the smaller neonates gave extremely lower values than the normal placentae from the lager ones.
These findings indicated that the placenta is an organ subjected to senescent changes. The onset of labor may be related with ageing of the placenta. In addition, it was suggested that the placentas with intrauterine growth retardation could show placental dysfunction accompanying senescent changes in the uterus.
