Immunohistochemical localization of HLA antigens and placental proteins (alpha hCG, beta hCG CTP, hPL and SP1 in villous and extravillous trophoblast in normal human pregnancy: a distinctive pathway of differentiation of extravillous trophoblast

Immunohistochemical localization of HLA antigens and placental proteins (alpha hCG, beta hCG CTP, hPL and SP1) in villous and extravillous trophoblast at various stages of normal human gestation were studied, using hysterectomy specimens. In the chorionic villi, the capacity for synthesizing placental proteins seemed to develop in parallel with the morphological change from mononuclear cells to multinucleated syncytiotrophoblast and no villous trophoblast expressed HLA antigens. In contrast, extravillous trophoblast, including the multinucleated trophoblastic cells at the deciduomuscular junction, expressed HLA-A, -B, and -C, and their capacity for synthesizing placental proteins did not seem to correspond with the degree of morphological change: the location of alpha hCG, beta hCG CTP and SP1 was restricted to mononuclear trophoblast in the superficial decidua, while hPL was present extensively in extravillous trophoblast. These findings strongly suggest that extravillous trophoblast possesses many distinctive biological features and differentiates in an independent manner. Mononuclear trophoblast forming the cell columns was also positive for HLA-A, -B, and -C, and no placental protein was demonstrated in these cells; this, together with previous morphological observations, may indicate the germinative nature of these cells.     

Morphological and immunohistochemical study on specimens of trophoblastic diseases in which the presence of a villous formation could not be established

The histopathological discrimination between malignant trophoblastic diseases and benign trophoblastic diseases depends on the presence or absence of a villous structure. However, molar extravillous trophoblasts and cells in some placental site trophoblastic tumors (PSTT) of a benign nature, lack a villous structure. We therefore observed the morphology of trophoblastic cells which do not constitute a villous structure, including choriocarcinoma cells, and analyzed the location of placental proteins in these cells immunohistochemically. The results were as follows: 1. Molar extravillous trophoblasts were composed of large mononuclear cells and multinuclear cells. Most of them were positive for hPL and negative for hCG and SP1. 2. Choriocarcinoma consisted of cytotrophoblast-like cells, syncytiotrophoblast-like cells, large mononuclear cells and multinuclear cells resembling large mononuclear cells. HCG was noted in syncytiotrophoblast-like cells and large mononuclear cells, while hPL and SP1 were found only in syncytiotrophoblast-like cells. 3. PSTT was made up of large mononuclear cells and multinuclear cells which contained abundant hPL and very little hCG and SP1 or none at all. Molar extravillous trophoblasts were clearly distinguishable from choriocarcinoma cells in terms of their morphology and the location of placental proteins. In contrast, it seemed difficult to distinguish cells of PSTT from molar extravillous trophoblasts on a cell level.     

Stimulation of hCG and inhibition of hPL in isolated human trophoblast cells in vitro by glycodelin A

The immunosuppressive protein glycodelin A (formerly named PP14) is produced by human decidua and secreted in the maternal circulation. Glycodelin A concentrations in serum have been used as indicators of endometrial function. The purpose of this study was to investigate the effect of glycodelin A on human chorionic gonadotropin (hCG) and human placental lactogen (hPL) release by freshly isolated cytotrophoblasts (in vitro). Cytotrophoblasts have been prepared from human term placenta by the three-step trypsin-DNase dispersion method of villous tissue followed by a percoll gradient centrifugation step. When placed in culture, the isolated mononuclear trophoblasts differentiated into syncytial counterparts within 12-72 h after plating. Trophoblasts were incubated with varying concentrations (60-300 microg/ml) of glycodelin A. Glycodelin A was isolated and purified by chromatographic methods from amnion fluid. Supernatants of the trophoblast cell cultures were assayed for hCG and hPL by immunological methods. The release of hCG is increased in glycodelin A-treated trophoblast cell cultures compared to untreated trophoblast cells. Glycodelin A inhibits the production of hPL in vitro. Differences in Glycodelin A stimulated cells and untreated controls are statistical significant. hCG and hPL are markers for the differentiation process of trophoblast cells to syncytial trophoblasts. The results imply that glycodelin A secreted by decidualised endometrium modulates endocrine function, as well as the differentiation of trophoblasts in culture.     

Linkage of human chorionic gonadotrophin and placental lactogen biosynthesis to trophoblast differentiation and tumorigenesis

Normal trophoblast of the human placenta elaborates at least two major protein hormones, chorionic gonadotrophin (hCG) and placental lactogen (hPL). Molar and choriocarcinoma tissues characteristically synthesize large amounts of hCG and hPL. To examine the role of trophoblast differentiation in the expression of the hCG and hPL genes, we studied the cytological distribution of their mRNAs in tissue sections of human hydatidiform mole and choriocarcinoma by in situ hybridization. Histologically, these tissues are in different stages of cellular differentiation. In normal placenta, hCG alpha/beta mRNA can be localized to some cytotrophoblasts and primarily to the syncytium, whereas hPL mRNA appears only in the syncytial layer. In hydatidiform mole, which still retains placental villous morphology, the hPL gene and hCG alpha and beta genes are expressed but are poorly localized because of the admixture of cyto- and syncytiotrophoblasts. By contrast, choriocarcinoma, which is devoid of placental villous pattern but in which the cyto- and syncytiotrophoblast-like components are distinguishable, expresses hCG alpha and beta in the syncytial-like areas but little, if any, hPL. These results suggest that a certain level of trophoblast differentiation, such as villous formation, is associated with hPL expression, while the hCG alpha gene and the hCG beta gene can be expressed in more disorganized tissues which contain cytotrophoblastic elements.     

The concentrations of SP1 beta and SP1 alpha in retroplacental and peripheral blood at term

The concentrations of the two components of Schwangerschaftsprotein 1 (SP1 beta and SP1 alpha), human chorionic gonadotrophin (hCG) and human placental lactogen (hPL), were measured in peripheral venous blood and in retroplacental blood at term delivery in 22 women. Like hCG and hPL, the values of SP1 alpha were higher in the retroplacental than in the peripheral blood, as might be expected with placental secretory products. On the other hand, the concentration of SP1 beta showed a reverse gradient, being higher in the peripheral than in retroplacental blood.     

The relation between the concentration of placental specific proteins in retroplacental and peripheral blood.

Concentrations of four placental proteins: human placental lactogen (hPL), placental protein 5 (PP5), pregnancy specific beta 1 glycoprotein (SP1) and human chorionic gonadotrophin (hCG), and a normal serum component, alpha 2 macroglobulin, were measured in the peripheral circulation and in blood obtained from the retroplacental space in 20 women at term delivery. Levels of hPL and PP5 were higher in the retroplacental blood than in the peripheral circulation in all patients. By contrast, levels of SP1 and hCG were consistently lower in retroplacental blood than in the peripheral circulation. Similarly, levels of alpha 2 macroglobulin were lower in the retroplacental blood. It is suggested that this 'reverse' gradient is a technical arterfact. These findings are discussed in relation to synthesis of placental proteins in a site distal to the retroplacental space, and the introduction of a technical artefact in the collection of samples.     

Molecular biological analysis of the DNA in trophoblastic disease--with special reference to genetic information of hPL and hCG(alpha, beta)

Genomic DNAs extracted from normal placenta, while blood cells, hydatidiform mole and choriocarcinoma were examined to see if they had the same coding structure for hPL, hCG alpha and hCG beta using each of the complementary DNAs. The restriction analysis of these genomic DNAs showed the same pattern even for the DNA of choriocarcinoma that transcribed no hPL mRNA but a relatively high level of hCG(alpha,beta)mRNA. We considered that during trophoblastic malignant transformation, neither the gene deletion for hPL nor the gene amplification for hCG occurred. Moreover, the genomic DNA sequence in hCG alpha gene has polymorphic restriction sites designated as R+/- and H+/-. Using these polymorphisms, we confirmed the hypothesis that a hydatidiform mole develops from an androgenetic origin. We also observed that it is possible that a hydatidiform mole having R- and H+ homozygous DNA may develop into a choriocarcinoma. These observation suggested that some intervening sequence between these polymorphic sites is related to the tumorigenesis of choriocarcinoma.     

Gestational trophoblastic diseases: the ratio of choriogonadotropin to specific pregnancy protein, hCG/SP1, provides useful diagnostic and prognostic evidence

Serum levels of human chorionic gonadotropin (hCG), specific pregnancy protein (SP1), and hPL were measured in 675 samples from women with uneventful pregnancy, and serially from the time of presentation in 125 patients with hydatidiform mole (HM), 43 with invasive mole (IM), and 34 with choriocarcinoma (CC). In HM serum levels of hCG and SP1 declined steadily from presentation to remission; when gestational age at the time of molar evacuation was shorter than 11 weeks, hCG declined to the normal range later than SP1 (57% patients), and when the age was longer--at the same rate as SP1 (26% patients) or earlier (17% patients). Serum levels of either marker were higher in IM than in HM and tended to increase, and in CC were either lower or higher than in IM. Treatment was followed by parallel decline of either marker, although SP1 declined to the normal range later than hCG in 12% of patients with IM and in 10% with CC. The hCG/SP1 ratios in normal pregnancy declined exponentially between the beginning and 23rd week of gestation and stayed level thereafter. The ratios calculated for the gestational age at the time of initial evacuation of the uterus or delivery were close to those of normal pregnancy in 80%, slightly increased in 20% of patients with spontaneously regressing HM, and markedly increased in 70% of patients with IM and in 74% of patients with CC. The ratios tended to increase during chemotherapy. An increase in the hCG/SP1 ratio seemed to be a characteristic sign of malignant change when compared with this ratio in normal pregnancy and hydatidiform mole. Determination of SP1 for monitoring therapy seemed redundant, and hPL assay was useful for discrimination between relapse and pregnancy.     

Characteristic differences in immunohistochemical localization of new placental proteins (PP1, PP19, PP21) in the human placenta

The immunohistochemical localization in the human placenta of new placental proteins PP1, PP19, and PP21 was clarified using modified indirect enzyme-labeled antibody method and compared with that of pregnancy-specific beta 1-glycoprotein (SP1). The major results are as follows: positive staining for PP1 was seen at the nucleus and cytoplasm of villous cytotrophoblasts, the X cells at the basal plate, and of chorionic trophoblasts, while the decidua cells and amnion were not stained. PP19 was characteristically seen in the nucleus and cytoplasm of syncytiotrophoblasts. X cells in basal plate, chorionic trophoblasts, and maternal leukocytes. The villous cytotrophoblasts, decidua cells, and amnion were not stained. PP21 localization was found at the microvilli and basal membrane of syncytiotrophoblasts and at the cytotrophoblast plasma membrane of the chorionic villus in early gestation. In late gestation, increased staining was seen at the syncytiotrophoblast microvilli and the villous basement membrane, and moderate staining at plasma membrane of the amniotic epithelium and chorionic trophoblasts. SP1 was found only at the syncytiotrophoblast cytoplasm of chorionic villi. Studies using these four placental proteins simultaneously may therefore provide a new key learning about unknown metabolic functions of trophoblasts.     

Circulating levels of pregnancy proteins in early and late pregnancy in relation to placental tissue concentration.

The concentrations of human chorionic gonadotrophin (hCG), human placental lactogen (hPL), pregnancy specific beta 1 glycoprotein (SP1), ferritin (PP2) and placental protein 5 (PP5) were examined in maternal serum and placental tissue in early and late pregnancy. The circulating concentration of hPL, SP1, and PP5 were higher during late pregnancy than early pregnancy, that of hCG lower, and ferritin (PP2) levels showed no difference. Placental tissue levels of hPL and SP1 were higher in late pregnancy, hCG levels lower, and ferritin (PP2) and PP5 showed no change. The ratio of the concentration in maternal serum to that in placental tissue increased during pregnancy for all proteins with the exception of ferritin. It is proposed that the mechanism of secretion of trophoblast specific proteins varies widely and that this should be taken into account in the clinical interpretation of circulating levels in the mother.     

人早孕期蜕膜和绒毛外滋养层细胞的免疫组织化学研究

侵入蜕膜组织的绒毛外滋养层细胞在HE染色标本上不易辨认。我们用免疫组织化学,ABC法,过氧化物-抗过氧化物酶标记蜕膜组织中的hCG与hPL阳性细胞。结果证明,子宫内膜中只要有一个绒毛外滋养层细胞存在就能被显示出来。这对提高妊娠诊断,防止残留滋养层细胞的增生与恶性病变很有意义。我们在蜕膜组织中还发现3类胎盘激素阳性细胞:hCG阳性细胞,hPL阳性细胞及hCG与hPL均为阳性的细胞。这一发现,证明了蜕膜有内分泌功能。     

Human choriogonadotropin (hCG) and placental lactogen (hPL) inhibit interleukin-2 (IL-2) and increase interleukin-1 beta (IL-1 beta), -6 (IL-6) and tumor necrosis factor (TNF-alpha) expression in monocyte cell cultures.

The effect of the human trophoblast hormones chorionic gonadotropin (hCG) and placental lactogen (hPL) on the expression of cytokines in peripheral blood mononuclear cell cultures was followed under a variety of culture conditions, (a) phytohemagglutinin stimulated cells (PHA-MSC), (b) allogenic mixed cells (AMC) and (c) spontaneously proliferating cells (SPC). A dose dependent enhanced release of IL-6, IL-1 beta and TNF-alpha by hCG and hPL was observed under all culture conditions. However, an inhibitory effect on the IL-2 release was seen in PHA-MSC by hPL and in AMC by hPL and hCG. The role of the suppression of IL-2 production/release on cytotoxicity towards trophoblast is discussed. These results suggest a sensitive, dose dependent hormonal control of the modulation of the immune response during pregnancy and strengthen the concept of a distinct regulation of monocytes and lymphocyte subpopulation by trophoblast hormones.     

In vitro secretory patterns of human chorionic gonadotrophin, placental lactogen and pregnancy-specific beta 1-glycoprotein

The control of secretion of the placental hormones human chorionic gonadotrophin (hCG) and human placental lactogen (hPL), and the trophoblastic protein pregnancy-specific beta-glycoprotein (SP1), is not well understood. During pregnancy, the hCG concentrations peak in the first trimester then decrease, while hPL and SP1 increase steadily throughout gestation. In order to determine whether the discordance between hCG secretion and that of hPL and SP1 observed in vivo also occur in vitro, we cultured placental explants with and without dibutyryl cyclic AMP (dbcAMP) and theophylline. Between 5 and 12 explants were used for each treatment in each experiment. The concentration of the proteins secreted into the media each day was measured by specific radioimmunoassays. The quantities of hPL and SP1 secreted per day declined in a parallel fashion after 24 hours under both basal and dbcAMP-stimulated conditions. The hCG output progressively decreased in the unstimulated cultures until 48 hours, at which time an increase in hCG secretion was observed. The dbcAMP-stimulated placentae significantly increased their hCG output at both 48 and 72 hours. These data show that hCG secretion is regulated differently from that of hPL and SP1. The results do not negate the possibility that term placental tissue may contain an inhibitor of hCG release that is removed by experimental manipulation in vitro.     

Immunocytochemical localization of human chorionic gonadotropin and placental lactogen in normal placentae

Preliminary observations on immunocytochemical localization of human chorionic gonadotropin (hCG) and human placental lactogen (hPL) were made in 35 placentae of normal pregnancy at various stages of development. By analysing the processing regularities of the two hormones and comparing the characteristics of immunocytochemical localization and hematoxylin-eosin stain on various trophoblasts in the normal placentae, the findings showed: (1) presence of the three types of trophoblasts, namely, cytotrophoblast (CT), intermediate trophoblast (IT), and syncytiotrophoblast (ST) was confirmed in normal placentae of first-trimester pregnancy. (2) IT has distinctive immunocytochemical features that distinguishes itself from CT and ST. In the first-trimester, ST contains a large amount of hCG which sharply diminishes thereafter, but hPL in ST increases with the fetal age. IT contains hPL all through the pregnancy period and the peak-value occurs in the second trimester. CT is devoid of hCG and hPL. The results indicated: (1) IT is more like ST but different from CT. (2) IT contains chiefly hPL and hCG only locally in early pregnancy which demonstrates that the processing of hPL is in the more well differentiated cells whereas hCG is in the less differentiated cells.     

Oxygen tension directs the differentiation pathway of human cytotrophoblast cells

During placental development, human cytotrophoblast cells can differentiate to either villous syncytiotrophoblast cells or invasive extravillous trophoblast cells. We hypothesize that oxygen tension plays a critical role in determining the pathway of cytotrophoblast differentiation. A highly purified preparation of cytotrophoblast cells from human third trimester placenta was cultured for 5 days in either 20% or 1% oxygen tension. The cells incubated at 20% oxygen formed a syncytium as determined by immunohistochemistry using an anti-desmosomal protein antibody that identifies cell membranes. In addition, the mRNA was markedly induced for syncytin, a glycoprotein shown to be essential for syncytiotrophoblast formation, and for human placental lactogen (hPL), which is a specific marker for syncytiotrophoblast cells. In contrast, the cell incubated at 1% oxygen tension did not fuse by morphologic analysis and did not express syncytin or hPL mRNA. However, these cells expressed abundant amounts of HLA-G, a specific marker for extravillous trophoblast cells, which was not seen in cells incubated at 20% oxygen tension. These results suggest that low oxygen tension directs differentiation along the extravillous trophoblast cell pathway while greater oxygen tension directs differentiation along the villous trophoblast cell pathway.     

Cytomorphological reappraisal of choriocarcinoma cells--a proposal of a four cell pattern

It is generally accepted that choriocarcinoma is composed of two cell types: syncytiotrophoblast (ST)-like cells and cytotrophoblast (CT)-like cells. In normal and molar pregnancy, there is another population of trophoblast in the cell column, the decidua and so forth. They are designated intermediate trophoblast (IT) and multinuclear IT. It remains to be clarified whether IT-like cells and multinuclear IT-like cells are observed in choriocarcinoma. In the present study, choriocarcinoma cells were reappraised cytomorphologically in three cases of uterine choriocarcinoma and additional three cases of metastatic choriocarcinoma. The results were as follows: 1. Choriocarcinoma cells could be classified into four cell types: ST-like cells, CT-like cells, IT-like cells and multinuclear IT-like cells. 2. IT-like cells predominated in metastatic lesions as compared with primary lesions. It seemed that choriocarcinoma shows both differentiations which take place in villous and extravillous trophoblasts of normal and molar pregnancy. IT-like cells were found to infiltrate into vessel walls, which, together with the predominance of IT-like cells in metastatic lesions, suggests that IT-like cells contribute greatly to the hematogenous metastasis in choriocarcinoma. The presence of ST-like cells, CT-like cells and multinuclear IT-like cells in metastatic lesions may indicate a germinative nature of IT-like cells.     

Increased expression of interleukin-1 beta is associated with persistence of the disease and invasion in complete hydatidiform moles (CHM)

Complete hydatidiform moles (CHM), a post-conceptual pathologic condition of the placenta, have a high prevalence rate (12/1,000 deliveries) in Kerala, India. This study addresses the expression of IL-1 alpha and beta by immunohistochemistry in relation to persistence and invasion of the disease. Mild to moderate expression of IL-1 alpha in the villous cytotrophoblasts, syncytiotrophoblasts and decidua of the first trimester in the normal placenta and all gestational ages in the molar placenta were observed. IL-1 beta expression was observed in the extravillous trophoblasts, syncytiotrophoblasts and decidua in both the normal and molar placentae and also in the villous cytotrophoblasts and the stromal Haufbaur cells in molar placentae. Strong expression of IL-1 beta in the placenta suggests its involvement in placental physiology supporting earlier reports. Higher expression of IL-1 beta correlated well with the invasive and persistent nature of the tumour and holds potential as a marker of persistence and invasion in CHM.     

Differential effects of dibutyryl cyclic AMP and epidermal growth factor on the synthesis and secretion of human chorionic gonadotropin and its subunits by trophoblastic and non-trophoblastic cells

The effects of dibutyryl cyclic adenosine 3',5'-monophosphate (cAMP) and epidermal growth factor (EGF) on the synthesis and secretion of human chorionic gonadotropin (hCG) and its subunits by normal and malignant trophoblasts as well as by non-trophoblastic cells were investigated in vitro. The explants of normal early placental tissues, choriocarcinoma cell line BeWo and non-trophoblastic tumor cell line CaSki from epidermoid carcinoma of the cervix, respectively, were cultured in the presence or absence of dibutyryl cAMP or EGF. The addition of either dibutyryl cAMP (1 mM) or EGF (100 ng/ml) caused significant increases in the synthesis and secretion of hCG and its subunits in cultures of normal and malignant trophoblasts, but had no stimulatory effect on hCG beta synthesis and secretion in culture of non-trophoblastic cell line CaSki that secretes predominantly hCG beta-like material. The magnitude of the stimulatory effects of dibutyryl cAMP and EGF on hCG (alpha,beta) synthesis and secretion by BeWo cells was much greater than that observed in normal trophoblasts. The time course of these stimulatory effects indicated that EGF-stimulated increase in hCG synthesis and secretion required a lag period longer than that for the dibutyryl cAMP-stimulated increase. These results suggest that there were no differences in normal and malignant trophoblasts in the mechanism for the stimulatory regulation of hCG (alpha, beta) synthesis and secretion, but immunoreactive hCG beta synthesis and secretion in non-trophoblastic tumor cells are regulated by a mechanism different from that in trophoblastic cells.     

Interrelationships of human chorionic gonadotropin, human placental lactogen, and pregnancy-specific beta 1-glycoprotein throughout normal human gestation

Human chorionic gonadotropin (hCG), human placental lactogen (hPL), and pregnancy-specific beta 1-glycoprotein (PSBG) were measured by radioimmunoassay in 270 samples of serum from women with uncomplicated pregnancies. All three proteins were significantly correlated with each other in individual samples of serum and with the estimated trophoblastic mass during the first trimester. No significant correlation could be demonstrated between the concentrations of hCG and PSBG in maternal serum during the second or third trimesters or between the concentrations of hCG and hPL during the second trimester. Levels of PSBG and hPL in serum were significantly correlated throughout all three trimesters. These findings suggest that the secretion of hCG, hPL, and PSBG may be regulated by similar control mechanisms during the first trimester of pregnancy. However, after this period, the factors that modulate the production of hCG differ from those that regulate the production of hPL and PSBG.     

A histologic and functional evaluation of non-villous trophoblasts in the basal plate of human placenta

This investigation of trophoblasts (Trs) in early gestation was performed by histologic and immunohistochemical evaluation of the Trs of the basal plate, decidua and myometrium, in an attempt to determine the changes in structure and function dependent on their location. The structural evaluation was performed by both light and electron microscopy and the functional evaluation by the localization of hCG, its subunits and hPL. In the syncytiotrophoblastic cell layer both hCG, its subunits and hPL are localized intracellularly. In the decidua, the so-called invasive Trs, only hPL could be detected. Histologically, the Trs in the deeper decidua tend to coalesce and become multinucleated. Thus, villous Trs and invasive Trs differ not only structurally, but also functionally, as can be seen by the differences in the synthesis of hCG and hPL, leading to the assumption that Trs have varying functions dependent upon their location.