The immunocytochemical localization of new soluble placental tissue proteins (PP14, 16, 17, 19, 20 and PP21) in human and cynomolgus monkey placentae

Apparently Placenta-specific placental tissue proteins (PP14 and PP17) and solitary tissue proteins (PP16, 19, 20 and PP21) were investigated by avidin-biotin immunoperoxidase technique in the human and cynomolgus monkey placentae, membranes, decidua and umbilical cords. In human early placentae, PP14, 16, 17, 19 and PP21 were localized mainly in the cytoplasm of villous syncytiotrophoblast. PP20 was localized in the cytoplasm of basal chorionic trophoblasts. In human term placentae, positive stainings for PP16, 19 and PP21 were observed mainly in all kinds of trophoblastic cells, while positive stainings for PP14, 17 and PP20 were weakened in the trophoblastic cells. PP20 was clearly localized in the cytoplasm of Hofbauer-like cells in the villous stroma. The membrane of villous syncytiotrophoblast showed strongly positive stainings for PP21. PP21 was also localized in the membrane of amniotic and umbilical epithelium. The umbilical epithelium was cytoplasmically positive for PP14, 16 and PP20. Clear positive stainings for PP14 and PP21 were found in the cytoplasm of fetal polymorphonuclear neutrophils. All of the placental proteins were immunocytochemically positive in the decidual large cells. In the cynomolgus monkey placentae, similar immunostaining results were obtained. The monkey could, thus, serve as a model for the investigation of the placental proteins.     

The content and immunohistochemical localization of placental protein 10 (PP10) in the fallopian tube

Summary. Radioimmunoassay; gel filtration and immunoperoxidase staining were used to study the content and localization of placental protein 10 (PP10) in 15 fallopian tubes removed on medical grounds from patients aged between 35 and 53 years. PP10 was consistently present in all parts of the tube at all ages and in all phases of the menstrual cycle. The PP10 concentration in tissue ranged from 0.08 to 2–95 μg/g of tuba1 cytosol protein. Irnmunoperoxidase staining localized PP10 in monocytic and lymphoid cells that were unevenly scattered in the subepithelial layer of the mucosa. In gel filtration, PP10 from the fallopian tube and purified placental PP10 eluted in the same volume, and graded amounts of PP10-immunoreactive material from the tube and purified PP10 gave parallel dose-response curves in radioimmunoassay. We conclude that PP10 is another 'placental protein' that has been identified in the fallopian tube.     

The content and immunohistochemical localization of placental protein 10 (PP10) in the fallopian tube

Radioimmunoassay, gel filtration and immunoperoxidase staining were used to study the content and localization of placental protein 10 (PP10) in 15 fallopian tubes removed on medical grounds from patients aged between 35 and 53 years. PP10 was consistently present in all parts of the tube at all ages and in all phases of the menstrual cycle. The PP10 concentration in tissue ranged from 0.08 to 2.95 micrograms/g of tubal cytosol protein. Immunoperoxidase staining localized PP10 in monocytic and lymphoid cells that were unevenly scattered in the subepithelial layer of the mucosa. In gel filtration, PP10 from the fallopian tube and purified placental PP10 eluted in the same volume, and graded amounts of PP10-immunoreactive material from the tube and purified PP10 gave parallel dose-response curves in radioimmunoassay. We conclude that PP10 is another 'placental protein' that has been identified in the fallopian tube.     

Isolation and characterization of five new soluble placental tissue proteins (PP22, PP23, PP24, PP25, PP26)

Summary Five new soluble placental tissue proteins (PP₂₂, PP₂₃, PP₂₄, PP₂₅, PP₂₆) were isolated to purity from saline extracts of human term placentas and characterized by their physico-chemical properties. Specific antisera to the new proteins were obtained by immunizing animals with the corresponding purified proteins. They were used to detect and quantitate the new proteins in extracts of placentas and other human tissues by immunochemical methods such as gel diffusion tests. The immunhistochemical localization of the new proteins as well as measurement of their concentrations in body fluids by sensitive radioimmunoassays are presently under investigation.     

Studies on the immunohistochemical localization of coagulation fibrinolysis factors in the placenta, especially of placental plasminogen activator (PPA)

We succeeded for the first time in extracting and purifying a coagulation fibrinolysis factor in the placenta, that is, a placental plasminogen activator (PPA). Using the enzyme-labeled antibody technique (indirect method), we investigated the localization of PPA, fibrinogen (FBG) and fibronectin (FN) in the placenta. And we tried to elucidate the physiological significance of the above three. The F(ab')2 fragments of their antibodies were produced by pepsin digestion, because there were various Fc receptors in the placenta. The results are summarized as follows: PPA was produced in the trophoblast, and was secreted out of the microvilli. FBG was located in the plasma. But, in the placenta, it was not in the cells and the connective tissue of which chorionic villi was composed. FN was located in the ground substances of connective tissue in the chorionic villi, and was associated with the cell structure. Because PPA, FBG and FN showed the same distribution on the fibrinoid material, it is expected that coagulation fibrinolysis activity proceeds in that fibrinoid material.     

Circulating levels of placental proteins, placental protein 5 (PP5), placental lactogen and Schwangerschafts-protein 1 (SP1), in antepartum eclampsia

Summary. Placental protein 5 (PP5), Schwangerschaftsprotein 1 (SP1) and human placental lactogen (hPL) were measured in 36 serum samples from seven women with antepartum eclampsia. PP5 levels were generally elevated, hPL levels were reduced and SP1 levels were within the usual ranges.     

Human term placenta releases placental protein 10 (PP10) in tissue culture

Placenta, decidua, chorion and amnion were studied to determine the tissue concentration of placental protein 10 (PP10). As measured by radio-immunoassay, all tissues studied were found to contain approximately the same concentration of PP10, in both early and late pregnancy. The release of PP10 was studied in tissue culture, first by using explants of placenta, decidua, amnion and chorion in four preliminary studies. Only the placenta released significant amounts of PP10 into the culture medium and, therefore, further studies were carried out with placental explants. In gel filtration, the bulk of PP10 in the culture medium eluted in the same position as purified PP10, and the dose-response curves of the two materials were parallel. The total secretion of PP10 into the culture medium was studied throughout 96 hours of incubation. Cycloheximide, a protein synthesis inhibitor, reduced the release of PP10 into medium by 31.3 +/- 12.5%. In cycloheximide-treated tissue cultures, the secretion of PP10 recovered when cycloheximide was replaced by original culture medium without cycloheximide. There results show that placenta is a major source of PP10.     

The relationship of placental protein 14 (PP14) in the mother and fetus to specific products of the human placenta

Levels of placental protein 14 (PP14), human placental lactogen (hPL) and unconjugated oestriol (E3) were measured in maternal peripheral and umbilical arterial and venous blood obtained from 65 normal pregnancies at term delivery. PP14 levels were one order of magnitude higher in the mother than in the fetus. Neither maternal nor fetal levels of PP14 were related to the birthweight of the fetus. There was a relationship between maternal and umbilical venous levels of PP14, which suggests that fetal PP14 is derived by transfer from the mother, or that there is an independent fetal source with a control mechanism similar to that of the mother. The findings are compatible with earlier observations to the effect that PP14, in contrast to products such as hPL and E3, is not specific to the trophoblast.     

Immunohistochemical localization of ECE-1 in the human placenta

Over the last several years, endothelin (ET-1) has emerged as an important mediator in the pathogenesis of pre-eclampsia and preterm labour, as well as in the normal function of gestational tissues. While the distribution of ET and its binding sites in the human placenta have been well studied, much less has so far been reported about the distribution of placental ET-1 processing enzymes. By immunohistochemical analysis and immunofluorescence, endothelin-converting enzyme-1 (ECE-1), the enzyme that synthesizes ET-1, is localized to five distinct cell populations in the human placenta: (1) the endothelial cells lining the maternal basal plate blood vessels, (2) the intermediate trophoblasts, (3) the endothelial cells lining the chorionic villous blood vessels, (4) the chorionic villous stromal cells and (5) the chorionic villous trophoblasts. The localization of ECE-1 corresponds with the previously reported distribution of ET-1 in the human placenta and is in accordance with the function of this enzyme in regulating vascular tone through synthesis of ET-1. The abundance of ECE-1 in the basal plate is consistent with a second possible function of this enzyme in affecting uterine contractions. ECE-1 may serve as a target for prognosis and therapy in states of pathologically altered vascular tone and/or altered myometrial smooth muscle tone in gestation.     

Regional ultrastructural differences in placental villi in cotyledons of a mature human placenta

Earlier histological, histochemical, biochemical and autoradiographic studies revealed a marked difference in the morphology and biology of placental villi dependence upon their localization within the materno-fetal circulation units (placentones).The quantitative differences demonstrated characterize the villi in the centres of the circulation units as morphologically and functionally less differentiated than the villi in the periphery.In the present study it should be scrutinized whether these differences can also be proven on the ultramicroscopic level. Small and large villi from both regions (centre and periphery) were studied. Two well-defined syncytial areas, namely syncytium directly overlying a fetal vessel and syncytium over a Langhans cell were studied separately. The following structures were chosen for study and counted by the ‘grid’ method.Microvilli, rough endoplasmic reticulum with parallel channels, vesicular rough endoplasmic reticulum, and the number of mitochondria.The ultrastructural studies support the earlier histological, enzyme-histochemical, biochemical and autoradiographic findings, which suggested that the villi in the periphery of the placentones have a higher degree of differentiation (maturation) than those in the centre. There are no qualitative differences between the two regions of the placentone but only quantitative differences which reflect the maturity of the villi.     

Circulating placental proteins (hCG, SP1 and PP5) in trophoblastic disease

Summary. Scrum human chorionic gonadotrophin (hCG), pregnancyspecific β₁-glycoprotein (SP₁) and placental protein 5 (PP5) levels have been measured by radioimmunoassay in 20 patients (116 samples) with hydatidiform mole, one patient (nine samples) with invasive mole and 10 patients (103 samples) with choriocarcinoma. Measurement of both serum SP₁ and hCG are useful in the monitoring of these diseases. The presence of PP5 in hydatidiform mole and its absence in choriocarcinoma support the hypothesis that PP5 is closely associated with the invasive activity of malignant trophoblast.     

Identification and localization of divalent metal transporter-1 (DMT-1) in term human placenta

The mechanism by which iron is transported from mother to fetus is incompletely understood. Whereas transferrin receptor (TfR) is responsible for iron uptake from maternal serum by the syncytiotrophoblast, the proteins responsible for intracytoplasmic transport and for delivery to the fetal serum remain unknown. The aim of this study was to determine whether the recently characterized endosomal membrane iron transporter, divalent metal ion transporter-1 (DMT-1), is expressed in human syncytiotrophoblast, and whether its cellular localization would support roles for cytoplasmic and placental-fetal iron transport. Six micron sections of frozen, term human placenta were assessed immunohistochemically using a polyclonal antibody to rat DMT-1 and a monoclonal antibody to human TfR. DMT-1 was found both in the cytoplasm and at the junction of the fetal (basal) membrane and fetal vessels, while TfR was localized predominantly to the maternal (apical) side of the syncytiotrophoblastic membrane. Double staining demonstrated no overlap between the two proteins on the apical membrane and minimal areas of overlap in the cytoplasm. We postulate that the syncytiotrophoblast takes up diferric transferrin from serum via TfR, subsequently incorporating the transferrin : TfR complex via endosomes. Subsequent transport of iron out of the endosome and across the basal membrane to the fetus may occur via DMT-1.