1.Introduction
Preeclampsia (PE) is a kind of pregnancy complications diagnosed with newly occurring hypertension and proteinuria after 20 gestation weeks1, which is a primary reason that lead to the death of pregnant women, fetus and newborn and is also related to fetal growth retardation and premature births. As the pathogenesis of PE has not been fully interpreted, the current understanding is still based on abnormal placenta and inflammation2. Under normal physiological conditions, placentation is closely correlated with spiral artery formation and placental trophoblasts cells invasion. In the process of PE, when the adaptation process of spiral arteries cannot be performed ideally, manifesting an obvious decline in the proportion of vascular remodeling which may result obstructive lesions. Besides, the insufficient trophoblastic invasion will cause the hypoxia and inflammation reaction, which in turn promote the trophoblastic apoptosis.
Under physiological conditions, placental trophoblast cells located at the maternal-fetal interface produce a variety of growth factors, such as neurotrophic factors3. Studies have indicated that neurenergen contributes to angiogenesis and energy homeostasis, probably playing a important role in early vascular development of fetus4, 5. Brain-derived neurotrophic factor (BDNF) , belonging to the member of neurotrophin family, plays a leading part in the formation of new vessels with the placental environment from the early phase of embryo development by binding the tyrosine kinase receptor B(TkrB)6. The TrkB signaling pathway is a new paracrine pathway that can regulate the growth of human trophoblast and promote trophoblast differentiation, proliferation and survival, so this signaling pathway plays an important role in the growth of human trophoblasts. Besides, BDNF can penetrate the maternal-fetal barrier, contributing to fetal phylogeny7. Previous study8, 9 have demonstrated that there is an association between BDNF and PE. The level of expression of BDNF showed an obvious difference between PE pregnant women and healthy women8, 10.
With the understanding of the PE pathogenesis, many researchers begin to focus on the important role of single-nucleotide polymorphism (SNP) in process of PE. Previous studies have indicated that certain candidate genetic loci SNPs associated with thrombosis, inflammation, oxidative stress and the renin angiotensin system11, 12 are related to the occurrence of PE13. BDNF Val66Met (rs6265)(G to A) may cause transfer of amino acid residues from valine (Val) in position 66 (nucleotide 196) to Methionine (Met) at the anterior region of BDNF, which have a functional effect on the BDNF activity14. In this study, we focus on exploring the relationship between BDNF Val166Met site and occurrence of PE, meantime initially discuss the transmission from mother to infant of this SNP and the connection between BDNF Val66Met and new born poor prognosis associated with PE.