The Effect Of IGF-1 On Biological Behavior Of Cytotrophoblasts Of Early Pregnancy And The Relationship Between This Effect And Hypertensive Disorder Complicating Pregnancy

IntroductionHypertensive disorder complicating pregnancy remains a main cause of leading increase of maternal and prenatal morbidity and mortality, the etiology of which is always an important topic of obstetrics. It is accepted that superficial implantation of placenta and poorly transformed spiral arteries are central etiology and pathology of hypertensive disorder complicating pregnancy. Moderate proliferation, differentiation, migration, infiltration and apoptosis of cytotrophoblasts at right time are the key points of implantation and formation of placenta during the pregnancy, which can be finely regulated by trophocytes and excretion in local microenvironment, if this regulation is out of control, a series of pathological processes such as hypertensive disorder complicating pregnancy will occur resulting from biological behavioral abnormality of trophocytes.Insulin-like growth factor-1 (IGF-1), a member of insulin-like growth factor family, having insulin-like metabolic effect, plays different parts in many physiological systems, whose effects on proliferation, differentiation, apoptosis and canceration of cell are specially concerned, and produces biological effect in local microenvironment by autocrine and paracrine.The biological effect of IGF-1 is mainly mediated by IGF-1 receptor(IGF-1R), and regulated by insulin-like factor binding proteins(IGFBPS). The fact that IGF-1R and IGFBPS are widely distributed in uterus and placental tissues manifests that IGF-1 may play an important role in human generation. People pay close attention to IGF-1 in the study of etiology of hypertensive disorder complicating pregnancy, due to the decrease of its expression in the serum and placentas of the pregnant women complicating hypertensive disorder. Although the effect of IGF-1 on hypertensive disorder complicating pregnancy, which mainly refers to the effect of IGF-1 on proliferation of trophocytes, has been reported by many domestic and overseas researchers, the effects of IGF-1 on differentiation, infiltration, apoptosis of trophocytes and their mechanisms have never been reported.ObjectiveOur study is to investigate the effects of IGF-1 in both normal pregnancy and pathological pregnancy, by detecting the changes of the levels of IGF-1,IGFBP-3 in serum in preeclampsia, and the differences of expressions of IGF-1, IGF-1R and IGFBPS-3 in villous placenta between in preeclampsia and in normal pregnancy, then, checking the results in vitro to do the groundwork for further study on the relationship between IGF-1 and hypertensive disorder complicating pregnancy.MethodsWe checked the changes of the levels of IGF-1 and IGFBP-3 in serum in preeclampsia and in normal pregnancy by ELISA,and sampled villi and placentas in different gestational weeks, and detected the expressions of IGF-1, IGF-1R and IGFBP-3 in placentas in different periods of pregnancy by immunohistochemistry and RT-PCR, meanwhile, we sampled placentas in mid and late pregnancy, detected the expressions of IGF-1, IGF-1R and IGFBP-3 in placentas of preeclampsia to make a contrast with normal; in vitro, serum-free primary cell culture, flow cytometer, western blotting and gel zymogram analysis were used to observe the effects of IGF-1 on apoptosis, differentiation and infiltration towards vascular endothelial cells of trophocytes of early pregnancy. ResultsThe levels of IGF-1 and IGFBP-3 in serum in preeclampsia were obviously lower than in normal pregnancy,and the extent of decrease was positively correlated with the severity of the disease, meanwhile,the levels of IGF-1 were positively correlated with the levels of IGFBP-3 in both groups.And IGF-1, IGF-1R and IGFBP-3 were expressed in the villi of early pregnancy, mid and full-term placentas,and they were mainly expressed in cytotrophoblasts and syneytiotrophoblast of villus folial.The expressions of IGF-1 and IGF-1R appeared a trend to increase both in transcription and in protein level,which were up to a high level at gestation week 32,until term,then fell down a little, while the expression of IGFBP-3 appeared a trend to decrease as gestational weeks increased.It's quite different between the expressions of mRNA of IGF-1, IGFBP-3 in placental tissues in normal pregnancy and in preeclampsia, from gestation week 28 to term, the latter were apparently lower than the former, while, the expression of IGF-1R in preeclampsia was the same with that in normal pregnancy. And expressions of IGF-1 and IGFBP-3 in preeclampsia at gestation week 28 and 32 were lower than that at gestation week 38.In vitro, apoptosis of normal cytotrophoblasts of early pregnancy which were cultivated in serum-free primary cell culture can be induced by 10ng/ml TNF-à, but this apoptosis can be apparently inhibited by 10nMIGF-1 at physiological dose. And flow cytometer detected that the rate of apoptosis decreased apparently, apoptosis signal transmissional molecule Caspase-3 and apoptosis related protein Bax decreased, apoptosis related protein Bcl-2 and PI-3K/Akt increased; meanwhile, the expression of vascular endothelial growth factor increased when normal cytotrophoblasts of early pregnancy which were cultivated in serum-free primary cell was effected by IGF-1 at physiological dose, and this effection appeared time-dependent, although the secretion of matrix metalloproteinases2,9 trended to increase as the time extended, the difference was not significant. ConclusionsThis study shows that cytotrophoblasts of pregnancy is one of important sources of IGF-1 and clarifies the expressional characteristics of IGF-1, IGF-1R and IGFBP-3 during the whole pregnancy, and their abnormal low-expressions in serum and in placentas in preeclampsia. Study in vitro confirms that IGF-1 can inhibit the apoptosis of cytotrophoblasts, and promote cytotrophoblasts to excrete VEGF, combining with the study in vivo, explains the potential mechanism of effect of IGF-1 on hypertensive disorder complicating pregnancy.