| Power frequency magnetic fields, generated by 50 or 60 Hz alternating current, usually exists around industry and agriculture electric appliances, household electric appliances and electric transmission apparatus. In recent decades, with rapid development of electric power and widely application of electric appliances, power frequency electromagnetic fields in people's daily life and working environment is increasing greatly and becoming a new source of pollution.In the latest three decades, there have been continuous epidemiologic studies reporting that exposure to power frequency magnetic fields during pregnancy may induce adverse pregnancy outcomes such as abortion, intrauterine growth retardation, low birth weight, stillbirth, sexual ratio change and so on, and several in vivo and in vitro experiments support the epidemiologic findings. However, there are also other epidemiologic studies, in vivo and in vitro tests reporting that exposure to power frequency magnetic fields has no adverse effects on pregnancy outcomes. So there isstill no consistent conclusion.Because pregnancy outcomes are directly associated with the quality of mankind, it is urgent to enforce study on this area. It appeared difficult to compare the contradictory laboratory data which was partly due to different exposure systems, research models, EMF exposure parameters and various endpoints for analysis, and the more important reason is no mechanism of EMF action available. Thus, it is critical and helpful to explore the biological effects induced by EMF and its possible mechanism.Pregnancy maintainence depends on normal function of placenta, the main functional cells of which are trophoblasts. On one hand, trophoblasts are the main source of human chorionic gonadotropin (HCG) and progesterone. On the other hand, they constitute placenta, which is the barrier between mother and fetus. It is proved that HCG and progesterone are quite necessary for normal pregnancy, especially at early stage. If they decrease, abortion may occure. Some harmful factors can induce excess apoptosis of trophobasts. As a result, the intactness of placenta is destroyed, the secretion of HCG and progesterone reduce, and deleterious procreation effects happen, which is one of the main mechanisms leading to adverse pregnancy outcomes.In the present study, the first-trimester human villi was chosen to explore the effects of power frequency magnetic fields exposure on function of trophoblasts, which is the crucial target of pregnancy diseases. It will provide direct evidences for the effects of power frequency electromagnetic fields on reproduction health and its possible mechanism.Part 1. The effect on secretion of human villous trophoblasts exposd to 50 Hz magnetic field.Trophoblasts separated from each villus were cultured in 10 wells and divided into two groups randomly. 5 wells served as the exposure groups and were put inexposure system, exposed to 50 Hz 0.4 mT or 0.2 mT magnetic fields for 6,12, 24, 48, 72 hours respectively. The other 5 wells served as control groups which were cultured in the same conditions as the exposure groups except for power frequency magnetis fields. At the corresponding times, both groups' curlture medium were collected, the content of HCG and progesterone was detected with electrochemiluminescence immunoassay. The results showed, after exposure to 0.4 mT magnetic fields for 72 hours, the content of HCG and progesterone decreased significantly (P<0.05, P<0.01) to 0.77±0.18 and 0.54±0.21 compared to the control. However, during exposure for 72 hours, 0.2 mT 50 Hz magnetic field did not affect the secretion of HCG and progesterone. The data suggested that exposure to 50 Hz magnetic field for a relative long time can affect the secretion of human villus trophoblasts cultured in vitro, and the intensity threshold may be between 0.2 mT to 0.4 mT.Part 2. The effect on apoptosis-related gene expression of human villous trophoblasts exposed to 50 Hz magnetic fields.Trophoblasts separated from each villus were cultured in 6 wells and divided into two groups randomly. 3 wells served as the exposure groups and were put in exposure system, exposed to 50 Hz 0.4 mT magnetic fields for 6, 48, 72 hours respectively. The other 3 wells served as control groups which were cultured in the same conditions as the exposure groups except for power frequency magnetis fields. At the corresponding times, trophoblasts of both the exposure and control groups were harvested at the same time, then we extracted the total RNA and detected the changing folds of Bcl-2, Bax, Caspase, Fas and p53 gene expression using real-time reverse transcription-polymerase chain reaction (RT-PCR) assay. The results showed that after exposure to 0.4 mT magnetic field for 6,48,72 hours, the average changing folds of gene expression were approximate to 1.00, and there are no significant difference. It is suggested that exposure to 50 Hz magnetic field within 0.4 mT for 72hours does not affect the apoptosis-related gene expression of human villus trophoblasts cultured in vitro.ConclusionAccording to the study, we get the following conclusions:1. Exposure to 50 Hz magnetic fields for a relative long period of time at relative high intensity depresses the secretion of villous trophoblasts cultured in vitro;2. Exposure to 0.4 mT 50 Hz magnetic field for 6, 48, 72 hours will not affect gene expression of Bcl-2, Bax, Caspase-3, p53, and Fas, suggesting that the secretion decease may not be through trophoblast apoptosis. |
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