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Apelin is an endogenous ligand of the human orphan receptor APJ. This peptide is produced through processing from the C-terminal portion in the pre-proprotein consisting of 77 amino acid residues and exists in multiple molecular forms. Although the main physiological functions of apelin have not yet been clarified, it is known that apelin is involved in the regulation of blood pressure, blood flow and central control of body fluid homeostasis in different organs. Since human placenta is a tissue where vasculogenesis, blood pressure and flow are dramatically important to allow a normal embryonic and fetal growth and development, the aim of the present study was to investigate the immunohistochemical distribution of apelin and APJ in normal placentas throughout pregnancy and in preeclampsia-complicated placentas. Specifically, we observed that in normal placentas the expression levels of apelin decreased from the first to the third trimester of gestation in both cytotrophoblast and syncytiotrophoblast cells and in the stroma of placental villi, in contrast with increased expression levels of APJ in the cytoplasm of cytotrophoblast cells and in the cytoplasm of endothelial cells of normal placenta samples. In contrast, in preeclampsia-complicated pregnancies, we observed a very strong increase of expression levels of both apelin and APJ receptor in all the placental compartments, cytotrophoblast, syncytiotrophoblast and stroma with a particular increase in endothelial cells inside preeclamptic placental villi. Our data seem to indicate an important role of apelin and APJ in the regulation of fetal development through a correct regulation of human placenta formation during pregnancy. Moreover, the strong expression levels of apelin and APJ in preeclamptic placentas, suggest their possible involvement in the onset of this pathology.

The objective of this study was to investigate correlates of risk for having microalbuminuria in individuals with one or more cardiovascular risk factors.The study involved 1919 individuals who attended general practice settings, were aged 55 to 75 yr, and did not have a history of cardiovascular events or diabetes but had one or more cardiovascular risk factors. A tree-based regression technique and multivariate analysis were used to identify distinct, homogeneous subgroups of patients with different likelihood of having microalbuminuria; interaction between correlates of microalbuminuria and risk for microalbuminuria was also investigated.The prevalence of microalbuminuria was 5.9%. Patients who did not have hypertension and had postload glycemia140 mg/dl showed the lowest prevalence of microalbuminuria (1.9%) and represented the reference class. The likelihood of microalbuminuria was seven times higher in men with hypertension and homeostatic model assessment levels in the upper tertile and four times higher in women with the same characteristics. Individuals with hypertension and lower homeostatic model assessment levels and normotensive individuals with postload glycemiaor = 140 mg/dl had a more than three-fold increased likelihood of having microalbuminuria. Treatment with statins was associated with a 54% reduction in the likelihood of having microalbuminuria, whereas levels of triglycerides150 mg/dl and fibrinogen levels in the upper tertile were associated with a significantly higher risk for microalbuminuria.The likelihood of having microalbuminuria in a population-based study of elderly individuals is strongly related to the interaction between the components of the metabolic syndrome, particularly hypertension, insulin resistance, and impaired glucose tolerance.

The balance between cell death and cell proliferation and its regulation are essential features of many physiological processes and are particularly important in fetal morphogenesis and adult tissue homeostasis. Apoptosis is a type of cell suicide that is activated in two main ways: through a receptor-mediated pathway or through a mitochondrial pathway. We have investigated the immunohistochemical distribution of proteins belonging to these two pathways in human placenta during gestation by comparing their expression levels between the first and third trimester of gestation. In the first trimester, the receptor-mediated pathway prevails over the mitochondrial pathway with a moderate/intense expression of its three components, viz., Fas ligand (FasL), Fas, and caspase-8, and weak positivity of anti-apoptotic FLIP, these proteins being mainly localized in the cytotrophoblast compartment. In the third trimester of gestation, there is an increased expression of mitochondrial pathway proteins, viz., Apaf-1 and caspase-9. We have also investigated the expression level of caspase-3, the primary effector caspase of both pathways, and have observed that it is moderately expressed during gestation, being mainly localized in the cytotrophoblast during the first trimester and in both placental compartments during the third trimester of gestation. Thus, both pathways actively function in human placenta to execute cell death. By means of immunoelectron microscopy, we have further shown that, in human placenta, the two proteins of the mitochondrial pathway together with caspase-3 are localized both in the cytoplasm and in the nucleus. In particular, Apaf-1 and caspase-9 are distributed near to the nuclear envelope suggesting an important role for these two proteins in disrupting the nuclear-cytoplasmic barrier.

Notch signaling is an evolutionarily conserved mechanism used by invertebrates and vertebrates to control cell fates through close-range cell interactions. Four Notch receptors have been identified in vertebrates and different ligands, divided into Delta-like and Serrate-like (Jagged). Several studies have demonstrated that Notch signaling is involved in different branches of the cell fate decision tree: differentiation, proliferation and apoptosis. These three processes are finely regulated in human placenta in order to allow a successful pregnancy and a correct fetal growth. Moreover, Notch and its ligands participate in the vascular remodelling and stabilization, other two processes much important and ticklish in human placenta. So, we decided to investigate the pattern of expression of Notch-1, Notch-4 and Jagged-1, together with two members related to Notch pathway and involved in angiogenesis: VEGF and p21, in human placenta during gestation by immunoblotting and immunohistochemistry. We showed a modulation of Notch proteins throughout the pregnancy; in particular we showed a slight decrease of Notch-1 throughout pregnancy, with a decreased cytoplasmic staining from the first to the third trimester of gestation in cytotrophoblast and syncytiotrophoblast. In contrast Jagged-1 showed an increase throughout pregnancy especially in syncytiotrophoblast and stroma during the third trimester of gestation. In addition, we found by immunoblotting an increase of VEGF expression from the first to the third trimester and an intense VEGF expression inside endothelial cells throughout the gestation as also confirmed by immunohistochemistry. We also showed a decrease of p21 expression during the pregnancy both through immunoblotting and immunohistochemistry assays. Moreover, we observed Notch localization in extravillous trophoblast cells that are able to invade the decidualized endometrium. Our results suggest an involvement of Notch signaling in regulation of placental cell fate decision and in angiogenesis that are dramatically important to maintain a normal physiology of this organ during pregnancy.

The placenta has a dynamic and continuous capacity for self-renewal. The molecular mechanisms responsible for controlling trophoblast proliferation are still unclear. It is generally accepted that the simultaneous activity of proteins involved in cell proliferation, apoptosis, and extracellular matrix degradation plays an important role in correct placental development. We investigated in depth the expression of the serine protease HtrA1 during pregnancy in human placenta by in situ hybridization and immunohistochemistry, we demonstrated that HtrA1 displayed a low level of expression in the first trimester of gestation and a strong increase of HtrA1 expression in the third trimester. Finally, by electron microscopy, we demonstrated that HtrA1 was localized either in the cytoplasm of placental cells, especially close to microvilli that characterized the plasma membrane of syncytiotrophoblast cells, or in the extracytoplasmic space of the stroma of placental villi, particularly in the spaces between collagen fibers and on collagen fibers themselves. The expression pattern of HtrA1 in human placentas strongly suggests a role for this protein in placental development and function. Moreover, on the basis of its subcellular distribution it can be postulated that HtrA1 acts on different targets, such as intracellular growth factors or extracellular matrix proteins, to favor the correct formation/function of the placenta. (J Histochem Cytochem 52:885–892, 2004)

Progression through the cell cycle in eukaryotic cells is controlled by a family of protein kinases, termed cyclin-dependent kinases (CDKs), and their specific partners, the cyclins. In particular, the control of mammalian cell proliferation occurs largely during the G1 phase of the cell cycle. Five mammalian G1 cyclins have been enumerated to date: cyclins D1, D2, and D3 (D-type cyclins), and cyclins E and E2. By the use of immunohistochemistry and immunoelectron microscopy, we observed that in the first trimester of gestation of human placenta, cyclin D1 was distributed in the nuclei of the cytotrophoblast compartment together with a weak positivity of endothelial cells surrounding blood vessels. The endothelial positivity of cyclin D1 strongly increased in the third trimester of gestation. Moreover, we observed the subcellular localization of cyclin D1 that was present both in the stroma of placental villi and in the nuclei of syncytiotrophoblast cells. Therefore, we observed that CDK4 was localized in the nuclei of the cytotrophoblast compartment during the first and third trimesters and it also had a nuclear positivity in the endothelial cells of blood vessels at the end of the third trimester of gestation. In conclusion we may hypothesize that cyclin D1/CDK4 complex functions to regulate the cell cycle progression in the proliferative compartment of human placenta, the cytotrophoblast, during the first trimester through interaction with p107 and p130. Therefore, cyclin D1 and CDK4 seem to be involved in the control of placental angiogenesis during the third trimester of gestation.