Is the atherosclerotic phenotype of preeclamptic placentas due to altered lipoprotein concentrations and placental lipoprotein receptors? Role of a small-for-gestational-age phenotype.

Atherosis of spiral arteries in uteroplacental beds from preeclamptic women resemble those of atherosclerosis, characterized by increased plasma lipids and lipoproteins. We hypothesized that: 1) lipoprotein receptors/transporters in the placenta would be upregulated in preeclampsia, associated with increased maternal and fetal lipoprotein concentrations; and 2) expression of these would be reduced in preeclamptic placentae from women delivering small-for-gestational-age (SGA) infants. Placental biopsies and maternal and umbilical serum samples were taken from 27 normotensive and 24 preeclamptic women. Maternal/umbilical cord serum LDL, HDL, total cholesterol, and triglycerides were measured. Placental mRNA expression of lipoprotein receptors/transporters were quantified using quantitative RT-PCR. Protein localization/expression of LDL receptor-related protein 1 (LRP-1) in the preeclamptic placentae with/without SGA was measured by immunohistochemistry. Placental mRNA expression of all genes except paraoxonase-1 (PON-1), microsomal triglyceride transfer protein (MTTP), and protein disulfide isomerase family A member 2 (PDIA2) were observed. No differences for any lipoprotein receptors/transporters were found between groups; however, in the preeclamptic group placental LRP-1 expression was lower in SGA delivering mothers (n = 7; P = 0.036). LRP-1 protein was localized around fetal vessels and Hofbauer cells. This is the first detailed study of maternal/fetal lipoprotein concentrations and placental lipoprotein receptor mRNA expression in normotensive and preeclamptic pregnancies. These findings do not support a role of altered lipid metabolism in preeclampsia, but may be involved in fetal growth.

Possible roles for folic acid in the regulation of trophoblast invasion and placental development in normal early human pregnancy.

In addition to its role in the prevention of neural tube defects, folic acid has many other physiological functions, including cell proliferation, DNA replication, and antioxidant protection. The aim of this study was to determine the role that folic acid has in regulating placental trophoblast development. Placental explants from placentae at gestational age 7 wk (n = 3) were cultured in folic acid at concentrations of 10(-6) M, 10(-8) M, and 10(-10) M. Extravillous trophoblast (EVT) invasion was assessed following 6-day culture, and explants were used for immunohistochemical evaluation of proliferation (MKI67) and apoptosis (active caspase 3). In addition, an array was performed on cell culture supernatants to examine a range of matrix metalloproteinases (MMPs) and tissue inhibitors of MMPs (TIMPs). Folic acid increased the invasion of EVT cells in this explant model by between 83% and 19% (P = 0.005), and this was associated with increased MKI67 positivity and decreased active caspase 3 positivity; this effect was concentration dependent and showed a biphasic response. In addition, culture in folic acid increased vascular density, as determined by anti-CD31 immunostaining (P = 0.05). The increase in EVT invasion correlated with increased placental explant secretion of MMP2 (P = 0.01), MMP3 (P = 0.01), and MMP9 (P = 0.02). This study demonstrates that folic acid is potentially important in a number of crucial early stages of placental development, including EVT invasion, angiogenesis, and secretion of MMPs, and highlights the need for further studies to address the benefit of longer-term folic acid supplementation throughout pregnancy to prevent pregnancy disorders associated with deficient placental development, including preeclampsia.

Altered decidual leucocyte populations in the placental bed in pre-eclampsia and foetal growth restriction: a comparison with late normal pregnancy.

Alterations in the balance of leucocyte populations in uterine decidua may lead to the generation of an unfavourable cytokine environment that is associated with unsuccessful pregnancy. Single and double immunohistochemical labelling was used to examine leucocyte populations in decidua from normal third trimester, foetal growth-restricted and pre-eclamptic pregnancies. Placental bed biopsies from 12 women undergoing elective Caesarean section with no hypertension or foetal growth restriction (FGR), 8 women with FGR without maternal hypertension and 12 women with pre-eclampsia (PE) were used to quantify decidual CD56+ uterine NK cells, CD14+ macrophages, CD3+T-lymphocytes and CD8+ lymphocytes. CD3+CD56+, CD8+CD56+ and CD161+CD3+ double-labelled cells in decidua were compared in PE and control decidua. Decidual CD3+T-lymphocytes (P<0.01), CD8+ cytotoxic T-lymphocytes (P<0.05), CD14+ macrophages (P<0.0001) and CD56+ uterine natural killer (uNK) cells (P=0.01) were decreased in placental bed biopsies from women with PE compared with control third trimester decidua. By contrast, only CD56+ uNK cells were decreased in FGR decidua (P<0.05). Double-positive CD8+CD56+ cells were also decreased in PE compared with control third trimester decidua (P<0.05). The reduction in specific leucocyte subset numbers in PE and uNK cells in FGR suggests that altered local cytokine balance may be important in defective trophoblast invasion and spiral artery transformation in these pathological pregnancies.

The genetics of pre-eclampsia and other hypertensive disorders of pregnancy.

Hypertension is the most frequent medical complication occurring during pregnancy. In this chapter, we aim to address the genetic contribution to these disorders, with specific focus on pre-eclampsia. The pathogenic mechanisms underlying pre-eclampsia remain to be elucidated; however, immune maladaptation, inadequate placental development and trophoblast invasion, placental ischaemia, oxidative stress and thrombosis are all thought to represent key factors in the development of disease. Furthermore, all of these components have genetic factors that may be involved in the pathogenic changes occurring. The familial nature of pre-eclampsia has been known for many years and, as such, extensive genetic research has been carried out in this area using strategies that include candidate gene studies and linkage analysis. Interactions between fetal and maternal genotypes, the effect of environmental factors, and epistasis will also be considered.

The importance of antioxidant micronutrients in pregnancy.

Pregnancy places increased demands on the mother to provide adequate nutrition to the growing conceptus. A number of micronutrients function as essential cofactors for or themselves acting as antioxidants. Oxidative stress is generated during normal placental development; however, when supply of antioxidant micronutrients is limited, exaggerated oxidative stress within both the placenta and maternal circulation occurs, resulting in adverse pregnancy outcomes. The present paper summarises the current understanding of selected micronutrient antioxidants selenium, copper, zinc, manganese, and vitamins C and E in pregnancy. To summarise antioxidant activity of selenium is via its incorporation into the glutathione peroxidase enzymes, levels of which have been shown to be reduced in miscarriage and preeclampsia. Copper, zinc, and manganese are all essential cofactors for superoxide dismutases, which has reduced activity in pathological pregnancy. Larger intervention trials are required to reinforce or refute a beneficial role of micronutrient supplementation in disorders of pregnancies.

Immune cells in the placental bed.

Leukocytes are an important component of the human uterine decidua in normal pregnancy. The focus of research has been on the more abundant populations such as the uterine natural killer (uNK) cells and macrophages, but more recently interest has also extended to less abundant, but functionally significant populations. Investigation of function in human pregnancy is limited by the scope of in vitro studies and the inability to perform in vivo manipulation of cell populations. Investigation of pathological pregnancy may provide clues to function, although acquisition of samples is limited until after clinical presentation. Investigation of animal models may provide clues to function in humans and this has certainly been the case for the uNK cells. However, human placentation differs substantially from the usual laboratory animal models and any extrapolation to humans from animal studies should be made with this in mind. Considerable advances have been made over the last 25 years but many questions still remain; the next 25 years may provide more answers to the role of the endometrial leukocytes in normal pregnancy, so that further advances can be made in investigation of their role, if any, in pregnancy pathology.