Fine structure of anchoring villi of the human placenta

Anchoring villi from the first trimester, early second trimester, and term were examined with the electron microscope. It was found that the small anchoring villi of the third and fourth month were particularly informative, since at this stage the cytotrophoblast is still proliferating, yet these cells form a compact discoidal region at the surface of the basal plate. Transitions from relatively undifferentiated cytotrophoblast cells adjacent to the stroma of the villus to large isolated cells surrounded by fibrinoid could readily be followed. These highly differentiated cytotrophoblast cells were found to have extensive regions of fine filaments, in addition to their pronounced endoplasmic reticulum, and were designated fibrous cytotrophoblast cells. The nature of the frequently incomplete epithelium covering anchoring villi at term was described, and some of the functions of the cytotrophoblast are discussed in relation to the observations of their fine structure.     

Histochemical study of metrial gland cells through the last week of pregnancy in the albino rat.

The metrial gland cells of the rat were studied from day 16 to 21 of pregnancy through enzyme histochemistry. The following enzyme activities were tested: 2 carboxylic esterases, 4 phosphatases, 1 aminopeptidase and 10 dehydrogenases including 4 which are involved in steroid metabolism. Although acid phosphatase activity was strong in mesenchymal cells, it remained undetected in large, sometimes binucleate cells lining central and subplacental vessels of the mesometrial triangle. 5-Bromo-indoxyl acetate esterase was likewise absent from the parietal vascular cells of the central artery. The study of 6 enzyme activities, i.e., GPDH, 3-OU-BDH, G6PDH, 3-B-HSDH, primary and secondary alcohol dehydrogenases, allowed to conclude that metrial gland cells are actively involved in steroidogenesis and lipid catabolism. Maternal origin of this gland can be sustained with reference to the pattern of acid phosphatase, indoxyl-esterase and some oxidoreductases II activities distribution which appears to be different from what is found in the trophospongium area.     

解聚素和金属蛋白酶19在早孕绒毛中的表达及其与自然流产的相关性研究

目的通过对解聚素和金属蛋白酶19（ADAM19）在早孕自然流产和正常早孕绒毛中表达的研究,探讨其在妊娠过程中的作用及其与流产的关系。方法早期妊娠和难免流产的绒毛组织各30例,应用免疫组织化学链霉素抗生物素-过氧化物酶法,检测ADAM19的表达。结果在正常妊娠的绒毛中,ADAM19主要表达在细胞膜上,在细胞滋养细胞、细胞滋养层细胞柱中均有较强的表达,表达强度均强于合体滋养细胞;在流产组绒毛中,ADAM19在细胞滋养细胞、细胞滋养层细胞柱中的表达均明显低于正常绒毛组,二者比较差异有统计学意义（P〈0.01）。结论ADAM19在妊娠早期滋养细胞的侵入中有重要的作用,早期流产的发生与绒毛中ADAM19水平下降有关。     

Analysis of the number and distribution of macrophages, lymphocytes, and granulocytes in the mouse uterus from implantation through parturition.

The metrial gland and decidua basalis are uterine structures which, during pregnancy in mice and rats, contain bone marrow derived cells. The current study demonstrates that large numbers of bone marrow derived cells, identified by common leukocyte antigen (CLA) positivity, accumulate in the mesometrial uterus between days 6 and 10 and contribute significantly to the cellularity of both the metrial gland and the decidua basalis. The distribution of F4/80+ cells (macrophages) is similar, suggesting that CLA+ cells in the metrial gland and decidua basalis are macrophages. Disappearance of luminal epithelium in the mesometrial uterus between days 11 and 12 leads to regression of metrial gland and decidua basalis and coincident disappearance of CLA+ and F4/80+ cells. A second population of CLA+ and F4/80+ cells appears in association with the development of new uterine luminal epithelium which surrounds the fetus and placenta during the final week of pregnancy. These very large accumulations of macrophages invariably are related to presence of epithelium.     

紧密连接蛋白Occludin在早孕绒毛组织中的表达及其意义

背景：Occludin蛋白是否在人早孕期胚泡植入中发挥作用,目前尚不能确定。 目的：探讨紧密连接蛋白Occludin在早孕绒毛组织中的表达及意义。 方法：早孕的正常人流绒毛组织和稽留流产绒毛组织各30例,用半定量RT-PCR,Western blot和免疫组化表达等各方法验证紧密连接蛋白Occludin在各组绒毛组织中的表达。 结果与结论：紧密连接蛋白Occludin主要表达在于绒毛外的合体滋养细胞的胞浆,胞核和少许间质,细胞滋养细胞Occludin表达低。半定量RT-PCR,Western blot和免疫组化表达等各方法验证紧密连接蛋白Occludin在正常人流和稽留流产绒毛组织中均有表达,前者的表达低于后者,但差异无显著性意义(P > 0.05)。说明紧密连接蛋白Occludin在绒毛组织有表达,细胞滋养细胞Occludin低表达可能是细胞滋养细胞极性消失的原因之一,参与细胞滋养细胞浸润能力形成,但胚胎发育停滞并不单是细胞滋养细胞侵润能力不足引起。     

Changes in the metrial gland of the rat uterus following ovariectomy on day 10 of pregnancy

Summary Rats were subjected to ovariectomy or a control operation on day 10 of pregnancy and light and electron microscope studies carried out to examine the cells of the decidua basalis and the mesometrial triangle. Degeneration of the decidua basalis was rapid but proliferation in the mesometrial triangle and differentiation of the typical granulated cells continued for some time, and resulted in the formation of a metrial gland. The earliest effect noted in the metrial gland was the appearance of inclusions in the fibroblast-like stromal cells one day after ovariectomy. During the next four days many stromal cells became packed with a variety of inclusions and it is suggested that some of these may represent phagocytosed cellular debris. Some debris appeared to be in intercellular spaces and was probably derived from granulated cells. Some granulated cells appeared to develop apparently empty vacuoles and this may be a preliminary stage in degeneration. Although granulated cells decreased to become very few in number five days after ovariectomy, the precise mechanism of their loss and the relationship of this to the hormonal environment could not be established.     

Ultrastructural analysis of folliculogenesis in the ovary of the yellow spotted stingray, Urolophus jamaicensis.

The ovary of the yellow spotted ray, Urolophus jamaicensis, is embedded in the epigonal gland, a lymphomyeloid organ. The covering of the ovary is composed of a germinal epithelium that is cuboidal and dome-shaped with microvilli. Adjacent cells have elaborate intercellular folds that create dilated intercellular spaces. In previtellogenic follicles, the follicle cells are simple cuboidal and contain modest amounts of synthetic or transport organelles. As vitellogenesis proceeds, the epithelium becomes multilaminar. Follicle cells are columnar as yolk precursors are transported from the maternal circulation, through the follicle cell cytoplasm, to the oocyte. Large, round cells occur in the follicle wall that contain lipid-like substances. These cells decrease in size and number as folliculogenesis proceeds and eventually disappear prior to ovulation. Columnar follicular cells and the oocyte have cellular extensions that impinge upon the zona pellucida. Transosomes are follicle cell extensions that indent the oocyte membrane. Tips of transosmes become enclosed by a layer of oocyte plasmalemma. The tips of transosomes pinch off and become resident in the ooplasm. Dense staining material occurs on the inner surface of the transosome membrane derived from the follicle cell. In Other animals, this material has been described as ribosome-like. This study is the first to document the presence of transosomes in a group other than Aves or reptiles. Follicle cells are supported by an extremely thick basal lamina. Subjacent to the lamina is the vascularized theca with fibroblasts embedded in a collagenous network. There is no differentiation into definitive theca interna and externa. In vitellogenic eggs, extensive inward folding of the follicular epithelium occur thereby generating more surface area for the transport of yolk precursors to the oocyte. Atretic follicles are common.     

Differentiation of the chorionic plate of the placenta: Cellular and extracellular matrix changes during development in the macaque

Background: The chorionic plate forms the fetal side of the placental disc, and its proper growth and development is important to the formation of a normal placenta. The development and structure of the chorionic plate has received little attention. Therefore, we have conducted a developmental and immunohistochemical study of the chorionic plate of the macaque placenta. Methods: Conventional light and transmission electron microscopy techniques were used to study macaque placental tissues collected from 22 days of gestation to near term. Standard immunoperoxidase methods were used to identify type IV collagen, laminin, and fibronectin in paraffin sections. Results: Early in gestation the chorionic plate trophoblast consisted of an outer layer of syncytiotrophoblast and a single underlying layer of cytotrophoblast. Beginning at about 100 days of gestation, the cytotrophoblast layer became stratified. The cytotrophoblast cells also became surrounded by variable amounts of extracellular matrix containing type IV collagen, laminin, and fibronectin. Ultrastructurally, the matrix contained abundant 10–12 nm diameter microfibrils. During later gestation the syncytiotrophoblast had a tendency to separate from the cytotrophoblast. Conclusions: The chorionic plate of the macaque placenta undergoes several distinctive morphological changes over the course of gestation. During the period of rapid diametrical growth of the disc, the chorionic plate trophoblast consists of a layer of syncytiotrophoblast and a single layer of cytotrophoblast. During later gestation the cytotrophoblast layer stratifies at a time coincident with that at which diametrical growth of the disc slows. The cytotrophoblast cells of later gestation appear synthetically active and at least some of their products are extracellular matrix components that encapsulate many of these cells. These components include type IV collagen, laminin, fibronectin, and microfibrils. © 1994 Wiley-Liss, Inc.     

The effect of pregnancy on the elastic membranes of mesometrial arteries in the guinea pig

Mesometrial arteries were obtained at various stages from adult virgin and primiparous guinea pigs beginning at pregnancy and ending at 40 days post-partum. The tissues were processed routinely and then stained with hematoxylin and eosin, and various elastic tissue stains. Picro-indigo-carmine and Van Gieson were used as counterstains. It was found that during the early stages of pregnancy the subendothelial cells of mesometrial arteries began to proliferate and the internal elastic membrane showed signs of fragmentation. By term the subendothelial cells formed a several layer thick cushion and the elastic fibers were virtually absent. About 22 days post-partum the subendothelial cells had disappeared and a new internal elastic membrane had formed. These changes are found mainly in the placental mesometrial arteries and to a lesser degree in the peripheral ones. Guinea pigs with unilateral pregnancies exhibited the above changes only on the side of the pregnant horn. It is suggested that the above changes are due to pregnancy and that local hormones elaborated by the placenta may be largely responsible for the alterations in the mesometrial arteries during pregnancy.     

Granulated metrial gland cells and interstitial trophoblast in the uterine wall of the bank vole, Clethrionomys glareolus, in early pregnancy

The morphology and distribution of granulated metrial gland cells and of interstitial trophoblast cells in the uterine wall was studied in the first half of pregnancy in the bank vole, Clethrionomys glareolus . The morphology and distribution of granulated metrial gland cells was generally similar to that found in other members of the Rodentia, although they were absent from the walls of the arterial vessels passing through the decidua basalis. Interstitial trophoblast invaded the decidualising endometrium mesometrial to, and antimesometrial to, the implanted embryos. There was no apparent spatiotemporal relationship between the distribution of granulated metrial gland cells and interstitial trophoblast cells.     

The development of daughter sporocysts inside the mother sporocyst ofSchistosoma mansoni with special reference to the ultrastructure of the body wall

The development of the mother sporocyst and the differentiation of the daughter sporocyst ofSchistosoma mansoni inBiomphalaria pfeifferi are described. The tegumental structure of the mother sporocyst, consisting of an outer layer connected to internally situated nucleated cell bodies, forms extensions which enwrap the germinal cells. The parenchyma cells, in which the germinal cells were embedded before, degenerate. When daughter sporocyst embryos develop from germinal cells they are enveloped by a primitive epithelium which is formed by fusion of the extensions of the tegumental structure of the mother sporocyst. Somatic cells located peripherally in the developing daughter sporocyst expand and coalesce beneath the primitive epithelium to form the future outer layer of the tegumental structure of the daughter sporocyst. The primitive epithelium degenerates, the newlyformed layer looses its nuclei, and becomes connected to internally situated nucleated cell bodies. Further developments in the tegumental structure of the daughter sporocyst include the formation of microvillus-like projections, a surface coat, spines, and a basement membrane.     

Light and electron microscopic examination of the mature decidual cells of the rat with emphasis on the antimesometrial decidua and its degeneration

Rat gestation sites were obtained on days 10 through 16 of normal pregnancy. Light and electron microscopic examination of day-10 sites revealed a consistent complex pattern of stromal cell morphologies. Six distinct regions were identified: an antimesometrial region of epithelioid decidual cells that form the gestation chamber containing the embryo and extraembryonic membranes; an abembryonic antimesometrial decidual region, the decidual crypt, where the cells are separated by large extracellular spaces; a mesometrial region with granule-containing cells and mesometrial decidual cells; a region of spiny cells that are lateral to the antimesometrial decidual cells and continuous with the mesometrial decidual cells; and a region of undifferentiated stromal cells adjacent to the myometrium. Between days 12 and 16, the antimesometrial decidua becomes thinner and is eventually sloughed into the newly formed uterine lumen. The role of the antimesometrial decidual cells is discussed with reference to trophoblast invasiveness, protein synthesis, and especially remodeling of the gestation chamber. Differences between decidua and deciduoma are considered.     

Granulated metrial gland cells at implantation sites of the pregnant mouse uterus

Summary A study has been made of the distribution of, and synthesis of DNA by, granulated metrial gland cells at implantation sites in the pregnant mouse uterus. Granulated cells were found in small numbers randomly distributed throughout the endometrium on day 41/2 of pregnancy. Subsequently cells of this type were lost from the antimesometrial and lateral decidua but increased dramatically in number in the developing decidua basalis. From day 71/2 granulated cells populated the mesometrial triangle to form the metrial gland. A high proportion of granulated cells was found to incorporate tritiated thymidine and the distribution of such cells is described. However, no granulated cells were found to incorporate tritiated thymidine at or after day 12 of pregnancy. In addition the loss of granulated metrial gland cells from the implantation site is described and is accounted for by degeneration in situ and also by migration via vascular channels. It is suggested that this latter route could be of functional significance.     

Ultrastructure and development of a thick basement membrane-like layer in the anchoring villi of macaque placentas

Background: Anchoring villi and cytotrophoblastic cell columns are important structural components involved in placental morphogenesis. We have previously described the presence of an unusual basement membrane-like layer (BMLL) that separates these placental compartments. The purpose of the present study was to identify developmental changes in the ultrastructure of the BMLL and to assess its changes in extracellular matrix composition over the course of gestation. Methods: Conventional techniques were used to examine macaque placental tissue by transmission electron microscopy. Standard immunoperoxidase methods were used to identify type IV collagen, laminin and fibronectin in paraffin sections. Results: Until day 35 of gestation the BMLL was 70–100 nm thick and appeared similar to basement membranes seen in other regions of the villus, although it usually lacked a lamina lucida along the surface adjacent to the cytotrophoblast cells. Immunohistochemistry revealed the presence of laminin and type IV collagen in the BMLL. By 53 days of gestation the BMLL had hypertrophied at the junction of the anchoring villus and cell column, measuring 2,000–5,000 nm in thickness. The BMLL retained immunoreactivity for laminin and type IV collagen. Ultrastructural examination revealed the presence of a new component in the form of 10 nm microfibrils. By 89 days of gestation the BMLL was not reactive for laminin or type IV collagen but otherwise maintained the structural organization seen at 53 days. No additional changes were observed in the BMLL during late pregnancy. Conclusions: The BMLL is a distinct extracellular matrix region that separates the distal aspect of the anchoring villus from the proximal portion of the cell columns. Evidence indicates that adjacent cytotrophoblast plays a prominent role in the production of the BMLL. The BMLL may serve to organize this complex tissue by separating fetal mesenchyme from cytotrophoblast cells that are proliferating, differentiating, and migrating. Modifications to the composition of the BMLL may indicate changes in the role this matrix plays in the development of the placenta. © 1994 Wiley-Liss, Inc.     

Chorioallantoic placenta formation in the rat: II. Angiogenesis and maternal blood circulation in the mesometrial region of the implantation chamber prior to placenta formation

Rat gestation sites were examined on days 7 through 9 of pregnancy by light microscopy and transmission and scanning electron microscopy to determine the extent of vascular modifications in the vicinity of the mesometrial part of the implantation chamber (mesometrial chamber). At a later time, the mesometrial chamber is, in conjunction with the uterine lumen, the site of chorioallntoic placenta formation. On day 7, in the vicinity of the mesometrial chamber, vessels derived from a subepithelial capillary plexus and venules draining the plexus were dilating. By early day 8, this network of thin-walled dilated vessels (sinusoids) was further enlarged and consisted primarily of hypertrophied endothelial cells with indistinct basal laminas. Sinusoids were frequently close to the mesometrial chamber's luminal surface which was devoid of epithelial cells but was lined by decidual cell processes and extracellular matrix. By late day 8, cytoplasmic projections of endothelial cells extended between healthy-appearing decidual cells and out onto the mesometrial chamber's luminal surface, and endothelial cells were sometimes found on the luminal surface indicating that endothelial cells were migrating. The presence of maternal blood cells in the mesometrial chamber lumen suggested that there was continuity between the chamber and blood-vessel lumens. On day 9, the mesometrial chamber was completely lined with hypertrophied endothelial cells, and sinusoid lumens were clearly continuous with the lumen of the mesometrial chamber. Mesometrial sinusoids and possibly the mesometrial chamber lumen were continuous with vessels in the vicinity of the uterine lumen that were fed by mesometrial arterial vessels. Clearing of the mesometrial chamber lumen during perfusion fixation via the maternal vasculature indicated the patency of this luminal space and its confluence with mesometrial arterial vessels and sinusoids. The conceptus occupied an an-timesometrial position in the implantation chamber on days 7 through 9, and it was not in direct contact with uterine tissues in the vicinity of the mesometrial chamber. These observations suggest that angiogenesis, not trophoblast invasion or decidual cell death, plays a major role in the opening of maternal vessels into the mesometrial chamber lumen before the formation of the chorioallantoic placenta.     

Neither lymphotoxin alpha nor lymphotoxin beta receptor expression is required for biogenesis of lymphoid aggregates or differentiation of natural killer cells in the pregnant mouse uterus

Gene ablation studies in mice indicate that lymphotoxin (LT)alpha, LTbeta and LTbetaR are essential for the genesis of lymph nodes (LN), normal structural development of peripheral lymphoid tissues and the differentiation of natural killer (NK) cells. LTbetaR binds to the heterotrimeric cytokines LTalpha1beta2 and LIGHT. LTs also regulate stromal cell expression of lymphocyte homing chemokines. Uterine decidualization in normal (+/+) mice is accompanied by the appearance and maturation of large numbers of uterine NK (uNK) cells that differentiate from precursors mobilized to the uterus from secondary lymphoid tissues. uNK cells accumulate in a transient, lymphocyte-rich region known as the metrial gland or, more recently, the mesometrial lymphoid aggregrate of pregnancy (MLAp). To determine if LTs contribute to development of the MLAp, and to the differentiation and/or localization of uNK cells, a histological study was undertaken of implantation sites from LTalpha null, LTbetaR null and gestation day-matched, normal mice. Implantation sites from the gene-ablated mice contained abundant numbers of uNK cells that localized appropriately. This indicates that the stromally derived molecules supporting NK cell differentiation in the uterus differ from those used in secondary lymphoid organs.     

Anaphase lag as the most likely mechanism for monosomy X in direct cytotrophoblasts but not in mesenchymal core cells from the same villi.

A 36 year old white female was referred for chorionic villus sampling for advanced maternal age. Direct (cytotrophoblast) preparations of chorionic villi were 45,X, but cultured mesenchymal core cells from the same villi were 46,XX. Study of embryonic and extraembryonic tissues showed the aneuploidy to be limited to cytotrophoblasts from specific placental sites. In aggregate, the cytogenetic findings can best be explained by anaphase lag during development of the cytotrophoblast, suggesting that this cytological mechanism and not non-disjunction is responsible for the common occurrence of monosomy X in villi.     

European collaborative research on mosaicism in CVS (EUCROMIC)—fetal and extrafetal cell lineages in 192 gestations with CVS mosaicism involving single autosomal trisomy

Cytogenetic information on cells from cytotrophoblast, villus mesenchyme, and one or more fetal tissues was available for 192 gestations with mosaicism or non-mosaic fetoplacental discrepancy involving a single autosomal trisomy in the chorionic villus sample (CVS), registered in a collaborative study (EUCROMIC) during the period 1986–1994. In order to identify predictors of confined placental mosaicism (CPM), generalized mosaicism and/or uniparental disomy (UPD), distribution of the mosaic and non-mosaic aneuploid cell lines in the different fetal and extrafetal cell lineages were analyzed. Data were related to existing hypotheses on mechanisms leading to fetoplacental discrepancies and early extraembryonic cell differentiation. Trisomy 21 mosaicism was the one most frequently confirmed in the fetus. Non-mosaic trisomy 13, 18, and 21 in the villus mesenchyme indicated the presence of a trisomic cell line in the fetus proper. Non-mosaic trisomy 2, 7, and 16 in villus mesenchyme was always found with concomitant mosaic or non-mosaic trisomy in the cytotrophoblast, but was never recovered in the fetus. Mosaic trisomy 3, 7, and 20 was predominantly restricted to the cytotrophoblast, mosaic trisomy 2 to the villus mesenchyme. Trisomies 15 and 16 were most often found in both cytotrophoblast and villus mesenchyme and not in fetal cells. This supports the hypothesis that mosaicism/discrepancy for trisomies 15 and 16 results more often than for the other trisomies from trisomic zygote rescue, enhancing their risk for UPD. We recommend, due to the risk of fetal trisomy, amniocentesis in all gestations involving mosaic autosomal trisomy in villus mesenchyme. In gestations with mosaic or non-mosaic autosomal trisomy in both cytotrophoblast and villus mesenchyme we recommend, in order to exclude fetal trisomy and/or UPD, depending on the chromosome involved, further examination by amniocentesis, ultrasound and/or test for UPD. We also recommend, due to a small but not negligible risk of false negative and false positive diagnoses, not to solely use direct preparation. Am. J. Med. Genet. 70:179–187, 1997. © 1997 Wiley-Liss, Inc.