Early Human Placenta Research Articles

Kinetic and immunologic evidence for the absence of glucose-6-phosphatase in early human chorionic villi and term placenta

The existence of the enzyme glucose-6-phosphatase (G6Pase) in early and term human placenta was investigated by comparing the characteristics of placental microsomal glucose 6-phosphate (G6P) hydrolytic activity and liver G6Pase. Placental microsomes exhibited similar apparent Km values for G6 P and β-glycerophosphate in intact and deoxycholate-treated microsomes, heat stability at acidic pH, low latency of mannose 6-phosphate hydrolysis, very low activity of pyrophosphate:glucose phosphotransferase, and undetectable [U-14C]G6 P transport into the placental microsomes, all of which indicated that specific G6Pase activity does not exist in placenta. Immunological evidence of the absence of both 36.5 kDa and T2 proteins, which represent the G6Pase catalytic protein and the phosphate / pyrophosphate transporter protein, respectively, confirmed that early and term human placenta are devoid of the multicomponent G6Pase enzyme.

Fibronectin and laminin in the early human placenta

The distribution of fibronectin and laminin was investigated in early intrauterine and ectopic tubal pregnancy using a standard immunoperoxidase technique on paraffin-embedded tissues. Localization of both fibronectin and laminin appeared identical in intrauterine and in ectopic pregnancy. Fibronectin was demonstrated in chorionic villous stroma, in the distal cytotrophoblast cell columns, in infiltrating mononuclear extravillous trophoblast and in endovascular trophoblast. Villous trophoblast and multinucleate interstitial trophoblast did not label. Extracellular fibronectin was demonstrated amidst sheets of infiltrating extravillous trophoblast. Laminin distribution was similar to that described for fibronectin but laminin was also present in the basement membrane of villous cytotrophoblast. Both fibronectin and laminin showed a pericellular distribution around decidual stromal cells. This study demonstrates further heterogeneity of human trophoblast populations. The presence of fibronectin in infiltrating extravillous trophoblast, endovascular trophoblast and in the distal columns may enhance trophoblast adhesion to maternal tissues and facilitate trophoblast migration.

Insulin-like growth factor 2 and short-range stimulatory loops in control of human placental growth.

Substructures of the first-trimester human placenta (within 3 months post-conception) display 'pseudo-malignant' properties. We show here, by in situ hybridization, that the insulin-like growth factor 2 (IGF-2) gene expression is particularly active in the cytotrophoblasts, which dominate these structures. Because the majority of placental IGF-2 mRNA is polysomal in extracts of first-trimester placenta, the spatial pattern of IGF-2 transcripts generally also defines the pattern of IGF-2 production. In primary trophoblast cultures, rendered quiescent by serum starvation. IGF-2 performs as a human embryonic growth factor by activating cell cycle entry/progression. Although both type 1 and 2 IGF receptor mRNAs can be found co-distributed with IGF-2 mRNA during placental development (supporting an autocrine role for IGF-2), these occasional patterns are confined to cytotrophoblasts with low proliferative potential. The reciprocity in ligand and receptor expression patterns are discussed in terms of rate-limiting steps in the involvement of IGF-2 in the proliferative phenotype of the early human placenta.

Ultracytochemical localization of adenylate cyclase in early human placenta.

A cytochemical study was carried out on adenylate cyclase (AC) activity in the early human placenta. Samples of placental villi were incubated in a medium containing adenylyl-imidodiphosphate (AMP-PNP) as specific substrate. No AC reaction product was encountered in placenta villi taken at 5 and 7 weeks of pregnancy. AC activity appeared at 9 weeks. At 9 and 10 weeks, AC reaction product was localized on the basal plasma membranes and on apposed plasma membranes of the Langhans cytotrophoblast. At 11 weeks AC activity was also clearly visible on Langhans cytotrophoblast and syncytiotrophoblast apposed plasma membranes. No AC reaction product was ever detected on the syncytiotrophoblast microvillar membrane. These results are in agreement with biochemical studies that localize AC on the villous trophoblast plasma membranes associated with the fetal circulation.

Immunohistochemical study of tissue polypeptide antigen (TPA) and cancer antigen 125 (CA125) in the human and cynomolgus monkey placenta, umbilical cord and decidua

Tissue polypeptide antigen (TPA) and cancer antigen 125 (CA125) were studied immunohistochemically by the avidin-biotin immunoperoxidase technique in human and cynomolgus monkey placentae, membranes, umbilical cords and decidua. In early human placentae, TPA was localized mainly in the cell membranes of villous syncytio- and cyto-trophoblast. The cytoplasm of those trophoblastic cells were weakly stained with TPA. The membrane of basal chorionic trophoblast cells was strongly stained with TPA and the cytoplasm stained weakly. In early cynomolgus placentae, similar immunostaining results were obtained. However, the positive stainings for TPA was more marked in the cytoplasm of villous syncytiotrophoblast and basal chorionic trophoblast, and less marked in the cell membrane of villous cytotrophoblast. In early human and cynomolgus placentae, CA125 was not demonstrated immunohistochemically in the villi and basal chorion. In human and cynomolgus term placentae, the villous syncytiotrophoblast and basal and reflected chorionic trophoblast showed similar immunostaining as the early placentae. In addition, TPA was found in the amniotic epithelium in both sorts of placentae. TPA was not detected immunohistochemically in the umbilical cord and decidual cells. While weakly positive stains for CA125 were observed in decidual cells, CA125 was localized mainly in the membrane and cytoplasm of amniotic epithelium in both human and cynomolgus term placentae. TPA and CA125 are thus oncoplacental antigens and the monkey could serve as a model for their investigation.

Intracellular binding proteins for retinol and retinoic acid in early and term human placentas.

Specific binding of both [3H]retinol and [3H]retinoic acid was observed in the cytosol fraction from term placentas and specific binding of [3H]retinol but not [3H]retinoic acid was detected in the cytosol fraction from placentas of 8-12 week pregnancies. The elution volume of the bound radioactivity on Sephadex G-100 column chromatography was within the range expected for proteins of molecular weight 14 500, in agreement with the results of others for cellular retinol- and retinoic acid-binding proteins from other tissues. The role of these proteins in mediating the effects of vitamin A on growth and differentiation of the placenta and fetus has yet to be determined.

Immunohistological and biochemical evidence for a role for hyaluronic acid in the growth and development of the placenta

A monoclonal antibody, designated NDOG1, has been used to stain a series of human and monkey placentae as well as several adult human tissues using immunoperoxidase techniques. In early placentae, NDOG1 was found to stain extracellular material associated with proliferating, extravillous cytotrophoblast cell columns and with the cytotrophoblast shell at the feto-maternal junction. The immunohistology suggests that NDOG1 antigen may be secreted by the anchoring cytotrophoblast into the immediately adjacent maternal tissues. NDOG1 antibody also shows extracellular staining in the stroma of early human placentae and reacted with the apical villous syncytiotrophoblast plasma membrane throughout pregnancy. Biochemical experiments demonstrated that extracts of this latter membrane contained NDOG1 antigenic activity which was susceptible to digestion with bovine testicular hyaluronidase. Hyaluronic acid was the only glycosaminoglycan found in this membrane, thereby implying a reaction between NDOG1 antibody and hyaluronic acid. Whilst no such direct interaction could be demonstrated in vitro. NDOG1 was shown to compete with two other antibodies which themselves demonstrated specificity for hyaluronic acid. The proposed identity between the NDOG1 antigen and hyaluronic acid is discussed particularly in terms of placentation where the distribution of NDOG1 staining may confirm the role of hyaluronic acid in providing an open matrix structure during stages of cell proliferation, migration and invasion.

Absence of major histocompatibility complex antigens in choriocarcinoma

Human trophoblastic cells are of fetal origin, and are not rejected or recognized as a target by cytotoxic T cells. The mechanism for this may not be easily explained, but whether trophoblastic cells express major histocompatibility complex antigens remains a most important topic. The recent introduction of monoclonal antibodies of defined major histocompatibility complex specificities has clarified that two types of trophoblastic cells are present in normal human early placenta.’ The one is a villous trophoblast (syncytiotrophoblast) which lacks both class I and class II major histocompatibility complex antigens, and the other is a extravillous trophoblast (nonvillous cytotrophoblast) which expresses at least class I major histocompatibility complex antigens. These findings stimulated us to analyze choriocarcinoma since it is a ma1ignar.t tumor

Cells of the fetomaternal interface: their role in the maintenance of viviparous pregnancy.

An immune system capable of discriminating between self and nonself evolved in nature long before the appearance of the viviparous mode of pregnancy, which brings maternal cells into a direct physical contact with genetically disparate cells of fetal origin. In the hemochorial type of placentation, the former include cells of the maternal immune system. This article briefly reviews the possible mechanisms that may protect the semiallogeneic conceptus in nature, with special reference to the role of the cells at the fetomaternal interface. We also present some new data on the antigenicity of pre- and postimplantation trophoblast cells and the immunobiology of decidual cells. Systemic changes in the maternal immune system appear to represent homeostatic responses to the presence of a semiallogeneic conceptus, unrelated to its protection; mechanisms for this protection must reside locally at the fetomaternal interface. We find that the lack of immunogenicity of the outer (trophoblast) cells of the preimplantation blastocyst can be explained by a transient disappearance of the major histocompatibility (MHC) antigens on their cell surface. However, following implantation and the formation of the placenta, class 1 MHC antigens reappear on certain classes of trophoblast cells, i.e., labyrinthine and spongiotrophoblast cells of the murine placenta. Similarly, cytotrophoblast cells of the early human placenta exhibit the presence of class 1 MHC antigens. An absence of class 2 MHC antigens despite the presence of class 1 antigens cannot entirely explain the lack of trophoblast immunogenicity. A local immunosuppression mediated by trophoblast cells themselves as well as maternal cells of hemopoietic origin in the decidua remain as a strong possibility. Typical decidual cells appear to play a central role in the maintenance of pregnancy because of their numerous functions: nutritive, endocrine, and immunoregulatory. Our studies reveal that they are descendants of bone-marrow-derived precursors, have unique surface markers recognizable with monoclonal antibodies nonreactive with other hemopoietic cell lineages, and have the ability to abrogate mixed lymphocyte reactions in vitro in a genetically unrestricted manner. Further studies directed at the cells of the fetomaternal interface should provide a better insight into the mode of survival of the nature's most commonplace allograft.

β-Hydroxybutyrate dehydrogenase activity in human placenta

It has been shown that mitochondria isolated from human placenta contain beta-hydroxybutyrate dehydrogenase activity. The properties of the beta-hydroxybutyrate dehydrogenase from human early placenta are very similar to those of the enzyme isolated from other mammalian tissues.

Identification and estimation of cell types in mixed primary cell cultures of early and term human placenta

Placental villi of early and term human placentae were dissociated with trypsin and mixed cell cultures were established. The different cell types were identified and estimated over a 14-day culture period using antibodies to keratin and vimentin filaments and their capacity to phagocytose yeast. The three main cell types were found to be epithelial-, macrophage- and fibroblast-like cells. The epithelial-like cells can be further divided into the multinucleated and the small- and medium-sized round cells, and these are most likely to be derived from the trophoblast. The cellular composition of cultures were different for early and term placentae and also varied characteristically over the 14-day cultures period.

Subcellular distribution of isocitrate dehydrogenase in early and term human placenta.

The activities of NAD-specific and NADP-specific isocitrate dehydrogenases were measured in early and term human placenta. In both tissues the activity of NADP-specific isocitrate dehydrogenase was severalfold higher than that of the NAD-dependent enzyme. Subcellular distribution of these two enzymes in the placental tissue was estimated. About 60% of the total NADP-specific isocitrate dehydrogenase activity was found in the mitochondrial fraction and about 40% in the cytosol fraction. Insignificant amounts of the total activity were bound to the microsomal fraction. The whole of the NAD-specific isocitrate dehydrogenase activity was localized in the mitochondrial fraction. The total mitochondrial NADP-specific isocitrate dehydrogenase activity in both early and term placenta was also estimated from the mitochondrial specific activity of this enzyme and the amount of mitochondrial protein in wet tissue, calculated from the activities of citrate synthase or cytochrome c oxidase assayed in the isolated mitochondrial fraction and in the tissue of early and term human placenta.

Beta-adrenergic receptors in early human placenta characterization of [ 3H]-dihydroalprenolol binding

The binding characteristics of beta-adrenergic ligand [ 3H]-dihydroalprenolol (DHA) were determined in particulate membranes of early human placenta (8 – 12 weeks of gestation). [ 3H]-DHA binding to crude membrane fractions was rapid, reversible, saturable and linearly correlated with the membrane protein concentration. Scatchard analysis of saturation experiments showed a K D of 2.80 ± 0.9 nM and a density of binding sites of 330.30 ± 93.5 fmol/mg protein. Agonist potency isoproterenol epinephrine norepinephrine indicated that early human placenta contains an adrenergic receptor of beta-2 subtype.

Tightly coupled mitochondria from human early placenta

1. A procedure for the isolation of tightly coupled mitochondria from human early placenta is described. 2. Mitochondria obtained by this method were able to oxidize Krebs cycle intermediates, pyruvate, glutamate, glutamine, palmitoyl-carnitine, alpha-glycerophosphate and beta-hydroxybutyrate. 3. These mitochondria incubated in the medium containing ethylene diamine tetraacetic acid and bovine serum albumin and no added Mg2+ ions exhibited a high respiratory control and adenosine diphosphate:oxygen (ADP:O) ratios corresponding to the theoretical values for all substrates tested. Addition of Mg2+ ions markedly reduced the respiratory control index and ADP:O ratio. 4. Adenosine triphosphatase (ATPase) activity in the obtained mitochondrial preparation was stimulated about tenfold by Mg2+. Oligomycin inhibited Mg2+-stimulated ATPase activity by about 25 per cent, but completely inhibited this activity in the absence of Mg2+ ions. 5. It is concluded that the effect of Mg2+ ions on the respiratory control and ADP:O ratio reported in this paper is exerted mainly through the Mg/+-stimulated oligomycin-insensitive ATPase activity.

HLA A, B, C antigens are expressed on nonvillous trophoblast of the early human placenta.

Samples were taken from the human chorionic sac at 6 wk postconception and were stained with monoclonal antibodies to trophoblast and to HLA antigens by means of an indirect immunoperoxidase technique. Antibody to HLA A, B, C antigens did not stain chorionic villous trophoblast in accordance with previous studies, but did stain nonvillous trophoblast of the cytotrophoblast cell columns and cytotrophoblastic shell. Antibody to HLA DR antigens showed no staining of trophoblast. This is the first demonstration of HLA antigens on a human fetal tissue in direct maternal contact. We have discussed the immunologic implications of this finding.

Corticosteroid metabolism in vitro by humanplacenta, fetal membranes and decidua in early and late gestation

Corticosteroid conversion by early (7 to 10 weeks) and late (36 to 42 weeks) human placenta, fetal membranes and decidua was studied. Tritiated cortisol, cortisone, corticosterone, 11-dehydrocorticosterone (DHC) and 11-deoxycorticosterone (DOC) were incubated in vitro with homogenates of these tissues and extracts chromatographed on Sephadex LH20 columns. 11 beta-hydroxysteroid dehydrogenase activity (11 beta-HSD; EC 1.1.1.146) was present in all these tissues from as early as the seventh week of pregnancy. In the fetal membranes the enzyme activity was present in the chorion, the amnion showing no activity. Only the decidua could convert cortisone and DHC to the biologically more active cortisol and corticosterone, respectively. DOC was not transformed by any of the tissues. No 11 beta-HSD activity was found in amniotic fluid, retroplacental serum, umbilical cord plasma or cord tissue.

Immunohistochemical demonstration of luteinizing hormone-releasing factor-like material in human syncytiotrophoblast and trophoblastic tumours.

Luteinizing hormone-releasing factor (LRF)-like immunoreactivity was demonstrated by a three layer bridge immunoperoxidase technique in the syncytiotrophoblast of early human placenta, hydatidiform mole and choriocarcinoma. Anti-LRF antiserum was prepared by immunizing rabbits with synthetic LRF coupled to bovine serum albumin (BSA). The immunoreactive site of LRF reacting with the antiserum resided between residues Tyr(5) and Gly(10)-NH2. Syncytiotrophoblast cells of the normal placenta from the first half of pregnancy and trophoblastic tumours, showed staining with anti-LRF antiserum after solid phase immuno-adsorption with Sepharose-coupled BSA. Adjacent control sections showed no staining when prepared with anti-LRF antiserum after immunoadsorption with a Sepharose-coupled LRF-BSA conjugate. The findings of LRF-like material in the placenta prompted us to examine the effect of exogenous LRF on the circulating levels of placental proteins and protein hormones synthesized by the syncytiotrophoblast. Serum levels of chorionic gonadotrophin, pregnancy-specific beta-l-glycoprotein, placental protein five, and placental lactogen remain unaltered for 2 h after an intravenous bolus of LRF (100-300 micrograms) to ten pregnant volunteers admitted for legal abortion between 8 and 18 weeks of gestation. The significance of LRF-like material for the endocrinology of the normal and malignant trophoblast remains to be elucidated.

Changes of the prostaglandin F2a metabolism in early human placenta.

The quantitative metabolism of PgF2a was studied in different ages of early human placentae in vitro. The 15-OH-Pg-dehydrogenase became minimal at about the 9th week.

Metabolism of prostaglandin F2alpha in early human placenta in vitro.

The authors were investigating the metabolism of prostaglandin F2alpha in human early placenta, in in vitro incubation experiments. They have identified both major metabolites, 15-keto-PGF2alpha and 15-keto-13,14 dehydro PGF2alpha. They have examined the change in the percentage of these, taken as a function of time. They have established that the main site of inactivating the endogenous PGF2alpha is the early human placenta. They suppose that the considerable Pg-inactiviting effect of the placenta has a part which acts as a protecting mechanism in preventing the uterotonic influence of the endogenous prostaglandins.

Enzymes of glucose and fatty acid metabolism in early and term human placenta

The activity of enzymes involved in glycolysis, gluconeogenesis, and lipogenesis in early and term human placenta was determined. A high activity of pyruvate kinase was found, indicating high glycolytic potential. The activity of this enzyme tended to decrease with gestation. The presence of phosphoenolpyruvate carboxylase activity was detected, suggesting the possibility of gluconeogenesis in the placenta. Very low activity of enzymes involved in fatty acid synthesis was found, whereas the activity o f the pentose shunt pathway enzymes, glucose-6-phosphate and 6-phosphogluconate dehydrogenases, was relatively high. This suggested a role of this pathway in the synthesis of lipids other than fatty acids in the placenta. The activities of enzymes in the human placenta and their changes during gestation where compared to previous observations on enzymes in rat placenta.