Stereological Analysis of Adolescent Placentas and Anthropometric Characteristics of Newborns.

INTRODUCTION: Knowledge of the size of surfaces available for transport is important for assessing the amount of nutrients that can be transmitted to the fetus for its normal growth and development. AIM: The aim of our study, was to determine the stereological structural parameters of the parenchymal part of placenta, ratio of birth weight and placental weight, and to determine their correlation with the body length and head circumference of the newborns of adolescent pregnant women. METHODS: The study was conducted on a total of 60 human placentas of term pregnancy, divided into two groups according to the age of pregnant women. The experimental group consisted of 30 placenta of pregnant women aged 13-19. The control group consisted of 30 placenta of pregnant women aged 20-35. Computer assisted morphological analysis of images of histological preparations using stereological methods was performed. RESULTS: Surface density of terminal villi of adolescent placentas is significant higher than the control group (t = 14,179, df = 29, p <0,0001). The T-test (t = -5,868, df = 29, p <0,0001) showed statistically significant difference in the surface density of fibrinoid in two compared groups. T-test (t = 6.438, df = 29, p <0.0001) found that total surface of terminal villi was significantly higher in adolescent placentas. The T-test (t = -6,747, df = 29, p <0,0001) found that total surface of fibrinoid was significantly lower in adolescent group. The T-test (t = 4.203, df = 29, p <0.0001) found that the ratio of birth weight of newborn and adolescent placental weight was significantly higher in relation to the control group. CONCLUSION: Adolescent placentas was more efficient in increasing the weight of newborns, compared to the control group placentas.

The volume of villi with γ-sm-actin positive perivascular cells correlates with placental weight and thickness.

INTRODUCTION: The classification of histologically stained villous cross sections in villous types (terminal, intermediate and stem villi) by stromal peculiarities is known to be observer predicated. Therefore, quantitative histology of villous trees has not become a routine endpoint of studies on the role of the placenta in prenatal programming, as opposed to the gross placental parameters weight and thickness. The classification of villous cross sections in central (stem) and peripheral (terminal) parts based on the presence or absence, respectively, of immunohistochemical detection of myofibroblasts in perivascular position is less observer dependent. We hypothesized that it will, possibly, identify microscopic correlates of placental weight and thickness within the villous tree. METHODS: 50 placentas from clinically normal pregnancies were processed for the present study. Thin villous cross sections, obtained in a systematic random manner, were stained immunohistochemically to detect γ-smooth muscle (sm) actin and to classify them subsequently as part of central or peripheral villous tree. The volume fractions of histological structures visible in villous cross sections (stroma, lumen, endothelium and syncytium) were estimated by design-based stereology. RESULTS: The present study reveals a significant correlation of placental weight and thickness with the volume estimate of stroma that have myofibroblasts in perivascular position. DISCUSSION: The positive linear correlation between the volume of central parts of villous trees and the placental weight and thickness is new. Surprisingly, the volume of more peripheral parts of villous trees, which is the main site of materno-fetal exchange does not correlate with placental weight and thickness.

Clarification and confocal imaging of the nonhuman primate placental micro-anatomy.

Geometry of the placental villous vasculature is a key determinant of maternal-fetal nutrient exchange for optimal fetal growth. Recent advances in tissue clarification techniques allow for deep high-resolution imaging with confocal microscopy; however, the methodology lacks a signal:noise ratio of sufficient magnitude to allow for quantitative analysis. Thus, we sought to develop a reproducible method to investigate the 3D vasculature of the nonhuman primate placenta for subsequent data analysis. Fresh placental tissue was dissected, formalin fixed, clarified using a modified Visikol® protocol and immunolabeled for CD31 (fetal endothelium) and cytokeratin-7 (villous trophoblast) for confocal imaging of the microanatomy. We present a detailed clarification and staining protocol augmented for imaging of nonhuman primate placental tissue. The image stacks generated by this refined staining method and our data acquisition parameters can be analyzed quantitatively to provide insights regarding the villous and vascular micro-anatomy of the placenta.

PLAC8, a new marker for human interstitial extravillous trophoblast cells, promotes their invasion and migration.

Proper differentiation of trophoblast cells in the human placenta is a prerequisite for a successful pregnancy, and dysregulation of this process may lead to malignant pregnancy outcomes, such as preeclampsia. Finding specific markers for different types of trophoblast cells is essential for understanding trophoblast differentiation. Here, we report that placenta-specific protein 8 (PLAC8) is specifically expressed in the interstitial extravillous trophoblast cells (iEVTs) on the fetomaternal interface. Using model systems, including placental villi-decidua co-culture, iEVTs induction by using primary trophoblast cells or explants, etc., we found that PLAC8 promotes invasion and migration of iEVTs. Mechanistically, time-lapse imaging, GTPase activity assay, co-immunoprecipitation and RNA-seq studies show that PLAC8 increases the Cdc42 and Rac1 activities, and further induces the formation of filopodia at the leading edge of the migratory trophoblast cells. More interestingly, PLAC8 is significantly upregulated under hypoxia and expression of PLAC8 is higher in iEVTs from preeclamptic placentas when compared with those from the normal control placentas. Together, PLAC8 is a new marker for iEVTs and plays an important role in promoting trophoblast invasion and migration.

Pattern of adhesive molecules expression in placenta of non-complicated ART pregnancies.

OBJECTIVE: To investigate changes occurring in the morphometric parameters of chorionic villi and their vessels as well as in adhesive molecules expression in placenta of ART pregnancies. METHODS: Case-control study including a total of 52 placentas of non-complicated pregnancies of women delivered by spontaneous conception (SC) (n = 26) compared with those of ART (n = 26). Histological and morphometric assessment of fetal chorionic villi as well as the expression of various adhesive molecules (ICAM-1, VCAM-1 and PECAM-1) were performed in fetal plasma and placenta. RESULTS: Although we did not observe any obvious changes in the histological structure of placenta of ART pregnancies, it showed a significant (p < 0.05) decrease in the syncytiotrophoblast cytoplasmic area accompanied with a significant increase (p < 0.05) in the vessel area and syncytiotrophoblast nuclear area without remarkable change in the total villous area or total syncytiotrophoblast % area. In addition, almost all levels of the assayed adhesive molecules were significantly increased (p < 0.05) in placenta as well as in fetal plasma of ART pregnancies compared with SC. CONCLUSION: We suggested in the current study that the altered adhesive molecules expression accompanying the increased vessel area and decreased syncytial cytoplasm area may indicate a subclinical endothelial stress in placenta of non-complicated ART pregnancies.

Villus packing density and lacunarity: Markers of placental efficiency?

We evaluate, in routine H&E histology slides, villus quantity in a given area (villous packing density, VPD) and the pattern or "gappiness" of villous distribution (lacunarity), and test for correlations with a proxy for fetoplacental metabolic rate, ß calculated as (ln (placental weight)/ln (birthweight)) from Kleiber's law [1]. Three ∼4.3 mm2 images each were obtained from 88 term placentas. Ranges of VPD and lacunarity were each correlated with ß (r = 0.31, p = 0.003, r = 0.23, p = 0.03 and respectively). The relationship between ß and within-placenta variation in VPD and lacunarity highlights the need to study not merely the mean but the variance of villous geometries and spatial distributions.

Differential expression of toll-like receptors in the human placenta across early gestation.

Toll-like receptors (TLRs) are an essential component of the innate immune system. While a number of studies have described TLR expression in the female reproductive tract, few have examined the temporal expression of TLRs within the human placenta. We hypothesized that the pattern of TLR expression in the placenta changes throughout the first and second trimester, coincident with physiological changes in placental function and the demands of innate immunity. We collected first and second trimester placental tissue and conducted quantitative PCR analysis for TLRs 1-10, followed by immunohistochemistry to define the cell specific expression pattern of a subset of these receptors. Except for the very earliest time points, RNA expression for TLRs 1-10 was stable out to 20 weeks gestation. However, the pattern of protein expression evolved over time. Early first trimester placenta demonstrated a strong, uniform pattern predominantly in the inner villous cytotrophoblast layer. As the placenta matured through the second trimester, both the villous cytotrophoblasts and the pattern of TLR expression within them became disorganized and patchy, with putative Hofbauer cells now identifiable in the tissue also staining positive. We conclude from this data that placental TLR expression changes over the course of gestation, with a tight barrier of TLRs forming a wall of defense along the cytotrophoblast layer in the early first trimester that breaks down as pregnancy progresses. These data are relevant to understanding placental immunity against pathogen exposure throughout pregnancy and may aid in our understanding of the vulnerable period for fetal exposure to pathogens.

A multiscale model of placental oxygen exchange: The effect of villous tree structure on exchange efficiency.

The placenta is critical to fetal health during pregnancy as it supplies oxygen and nutrients to maintain life. It has a complex structure, and alterations to this structure across spatial scales are associated with several pregnancy complications, including intrauterine growth restriction (IUGR). The relationship between placental structure and its efficiency as an oxygen exchanger is not well understood in normal or pathological pregnancies. Here we present a computational framework that predicts oxygen transport in the placenta which accounts for blood and oxygen transport in the space around a placental functional unit (the villous tree). The model includes the well-defined branching structure of the largest villous tree branches, as well as a smoothed representation of the small terminal villi that comprise the placenta's gas exchange interfaces. The model demonstrates that oxygen exchange is sensitive to villous tree geometry, including the villous branch length and volume, which are seen to change in IUGR. This is because, to be an efficient exchanger, the architecture of the villous tree must provide a balance between maximising the surface area available for exchange, and the opposing condition of allowing sufficient maternal blood flow to penetrate into the space surrounding the tree. The model also predicts an optimum oxygen exchange when the branch angle is 24 °, as villous branches and TBs are spread out sufficiently to channel maternal blood flow deep into the placental tissue for oxygen exchange without being shunted directly into the DVs. Without concurrent change in the branch length and angles, the model predicts that the number of branching generations has a small influence on oxygen exchange. The modelling framework is presented in 2D for simplicity but is extendible to 3D or to incorporate the high-resolution imaging data that is currently evolving to better quantify placental structure.

Three-dimensional modeling of human placental terminal villi.

INTRODUCTION: Placental transport is the main factor affecting the health and development of the fetus. Due to the placenta's geometrical and mathematical complexity, the structure-function relations of placental terminal villi have not been successfully modeled. Hence, a novel modeling approach is proposed. METHODS: Computational models of four different specimens were generated from the three-dimensional reconstruction of confocal laser scanning microscopic image stacks. To evaluate the capabilities of the proposed methodology, stationary oxygen diffusion transport was calculated in the terminal villus volumes. RESULTS: The reconstructions automatically provided the spatial arrangement of the fetal capillaries inside the terminal villi. The surface and volume ratios between the fetal capillaries and the villus were also calculated, and the effects of model parameters on the placental diffusive capacity were assessed by parametric analysis. DISCUSSION: The potential of three-dimensional reconstructions combined with finite element analysis as a research tool for the human placenta was tested. The methodology herein could serve in the future as a simulation platform for complicated in vivo and in vitro scenarios.

Novel 3D light microscopic analysis of IUGR placentas points to a morphological correlate of compensated ischemic placental disease in humans.

The villous tree of the human placenta is a complex three-dimensional (3D) structure with branches and nodes at the feto-maternal border in the key area of gas and nutrient exchange. Recently we introduced a novel, computer-assisted 3D light microscopic method that enables 3D topological analysis of branching patterns of the human placental villous tree. In the present study we applied this novel method to the 3D architecture of peripheral villous trees of placentas from patients with intrauterine growth retardation (IUGR placentas), a severe obstetric syndrome. We found that the mean branching angle of branches in terminal positions of the villous trees was significantly different statistically between IUGR placentas and clinically normal placentas. Furthermore, the mean tortuosity of branches of villous trees in directly preterminal positions was significantly different statistically between IUGR placentas and clinically normal placentas. We show that these differences can be interpreted as consequences of morphological adaptation of villous trees between IUGR placentas and clinically normal placentas, and may have important consequences for the understanding of the morphological correlates of the efficiency of the placental villous tree and their influence on fetal development.

Does 2D-Histologic identification of villous types of human placentas at birth enable sensitive and reliable interpretation of 3D structure?

INTRODUCTION: The villous tree of human placentas is a complex three-dimensional (3D) structure which enables fetomaternal exchange. Current concepts of microscopic analyses are based on the analysis of two-dimensional (2D) histologic sections. For this approach, the assessment of the stromal core of sectioned villi is of key importance. The classification of stromal properties of sectioned villi allows allocation of villous sections to villous types which are named by their expected position in villous trees (terminal, intermediate, and stem villi). METHOD: The present study takes these current concepts of placental histology as hypothesis and validates them against predetermined 3D positions of branches of villous trees. The 3D positions were determined prior to histologic sectioning using a recently introduced 3D-microscopic approach. Individual histologic sections of villi were classified by their stromal structures and inter rater variability of these histologic assessments were determined. RESULTS/DISSCUSSION: Inter rater variability was high and indicates substantial observer influence on the outcome of histologic assessments. Cross-match of villous types with the predetermined positions of villous branches of villous trees revealed substantial mismatch between the outcome of stromal classification and 3D-position of the sectioned villi in the placental villous trees.

Novel 3D microscopic analysis of human placental villous trees reveals unexpected significance of branching angles.

The villous trees of human placentas delineate the fetomaternal border and are complex three-dimensional (3D) structures. Thus far, they have primarily been analyzed as thin, two-dimensional (2D) histological sections. However, 2D sections cannot provide access to key aspects such as branching nodes and branch order. Using samples taken from 50 normal human placentas at birth, in the present study we show that analysis procedures for 3D reconstruction of neuronal dendritic trees can also be used for analyzing trees of human placentas. Nodes and their branches (e.g., branching hierarchy, branching angles, diameters, and lengths of branches) can be efficiently measured in whole-mount preparations of isolated villous trees using high-end light microscopy. Such data differ qualitatively from the data obtainable from histological sections and go substantially beyond the morphological horizon of such histological data. Unexpectedly, branching angles of terminal branches of villous trees varied inversely with the fetoplacental weight ratio, a widely used clinical parameter. Since branching angles have never before been determined in the human placenta, this result requires further detailed studies in order to fully understand its impact.

The emerging roles of placenta-specific microRNAs in regulating trophoblast proliferation during the first trimester.

In the human placenta, eight 'placenta-specific' microRNAs (miRNAs) are exclusively expressed and are associated with high cloning frequencies. The expression of placenta-specific miRNAs is known to be involved in preeclampsia, but the understanding of these miRNAs is still limited. The goal of this study was to investigate the levels and localisations of eight placenta-specific miRNAs in placental villi with different proliferative abilities during the first trimester. Immunohistochemical analyses indicated that placental trophoblast proliferation ability was associated with the weight of villi in the same gestational week during the first trimester. Of the eight placenta-specific miRNAs, quantitative real-time RT-PCR demonstrated that the expression of miR-517b and miR-1283 was increased in the lightest villi and decreased in the heaviest one, the expression of miR-519a was increased in the heaviest villi and decreased in the lightest one. In situ hybridisation analysis showed that miR-517b and miR-519a were located primarily in the trophoblast layer, while miR-1283 were expressed not only in the villous trophoblasts but also in some villous stroma cells. These findings suggest that miR-517b and miR-519a may play an important role in trophoblast proliferation during the first trimester.

[Anchoring villi are sources of cytotrophoblastic invasion in the second trimester of physiologic pregnancy].

The basal laminas and fixed on them anchoring villi after late abortion on 18-28 weeks of pregnancy have been studied. The pregnancies were without complication and abortions were activated by "Enzaprost" injection. 4 types of anchoring villi were studied: without cytotrophoblastic invasion, with maximal, medium and minimal density of cytotrophoblastic distribution and depth of its invasion into endometrium from villi's base. The maximum of its migration activity was in 18-20 and 22-23 weeks of pregnancy. The activity decay of cytotrophoblastic invasion was been found in the end of the second trimester Anatomic contact of villi's base with endometrium increased by them parallel attachment or horseshoe-shaped form. The estimation of villi's quantity and density of cytotrophoblastic distribution in their base can use for definition of cytotrophoblastic invasion rate in the adjacent myometrium of pregnant women on the second trimester.

The effect of smoking on early chorionic villous vascularisation.

The aim of the study was to investigate whether first trimester chorionic villous vascularisation is different in women who smoked cigarettes before and during pregnancy in comparison with women who did not smoke. Placentas of smoking (>10 cigarettes/day, n = 13) and non-smoking women (n = 13), scheduled for a legal termination of a viable first trimester pregnancy for social indications, were retrieved. Placental tissues of 3-5 mm³ were whole mount CD31 immunofluorescence stained. Images of the CD31 immunofluorescence and contour of the villi were captured using an Optical Projection Tomography scanner. An immersive BARCO virtual reality system was used to create an enlarged interactive 3-dimensional hologram of the reconstructed images. Automatic volume measurements were performed using a flexible and robust segmentation algorithm that is based on a region-growing approach in combination with a neighbourhood variation threshold. The villous volume, vascular volume and vascular density were measured for the total chorionic villous tree as well as for its central and peripheral parts. No differences in maternal age and gestational age were found between non-smoking and smoking women. No differences were found in the total, central and peripheral villous tree volume and vascular volume. The central (13.4% vs. 9.5%, p=0.03) and peripheral (8.4% vs. 6.4%, p=0.02) villous tree vascular densities were increased in the smoking women as compared with the non-smoking women. In conclusion, chorionic villous vascularisation is already altered in first trimester of pregnancy in women who smoked cigarettes before and during pregnancy.

Caspase-mediated apoptosis of trophoblasts in term human placental villi is restricted to cytotrophoblasts and absent from the multinucleated syncytiotrophoblast.

Human placental villi are surfaced by a multinucleated and terminally differentiated epithelium, the syncytiotrophoblast, with a subjacent layer of mononucleated cytotrophoblasts that can divide and fuse to replenish the syncytiotrophoblast. The objectives of this study were i) to develop an approach to definitively identify and distinguish cytotrophoblasts from the syncytiotrophoblast, ii) to unambiguously determine the relative susceptibility of villous cytotrophoblasts and syncytiotrophoblast to constitutive and stress-induced apoptosis mediated by caspases, and iii) to understand the progression of apoptosis in villous trophoblasts. Confocal microscopy with co-staining for E-cadherin and DNA allowed us to clearly distinguish the syncytiotrophoblast from cytotrophoblasts and identified that many cytotrophoblasts are deeply interdigitated into the syncytiotrophoblast. Staining for specific markers of caspase-mediated apoptosis indicate that apoptosis occurs readily in cytotrophoblasts but is remarkably inhibited in the syncytiotrophoblast. To determine if an apoptotic cell or cell fragment was from a cytotrophoblast or syncytiotrophoblast, we found co-staining with E-cadherin along with a marker for apoptosis was essential: in the absence of E-cadherin staining, apoptotic cytotrophoblasts would easily be mistaken as representing localized regions of apoptosis in the syncytiotrophoblast. Regions with perivillous fibrin-containing fibrinoid contain the remnants of trophoblast apoptosis, and we propose this apoptosis occurs only after physical isolation of a region of the syncytium from the main body of the syncytium. We propose models for the progression of apoptosis in villous cytotrophoblasts and for why caspase-mediated apoptosis does not occur within the syncytium of placental villi.

Histomorphometric characteristics of first trimester chorionic villi in pregnancies with low serum pregnancy-associated plasma protein-A levels: relationship with placental three-dimensional power doppler ultrasonographic vascularization.

OBJECTIVE: To evaluate histomorphometric vascular characteristics from samples obtained by chorionic villus sampling (CVS) in pregnancies with low serum pregnancy-associated plasma protein-A (PAPP-A) levels and to relate these findings to three-dimensional (3D) placental volume and power Doppler vascularization. METHODS: Immediately before CVS, placental 3D-power Doppler ultrasonography was performed at 11 + 0 to 13 + 6 weeks in 12 pregnancies with PAPP-A concentrations <0.3 multiples of median (MoM) as well as in 11 control women. Using a standardized setting placental volume, vascularization index (VI), flow index (FI), and vascularization flow index (VFI) were measured. Histomorphometric parameters of villi were blindly evaluated with a video-computerized-image-analysis system. RESULTS: Pregnancies with low PAPP-A showed a significantly reduced number of capillary vessels per villus cross-section (p = 0.005) and a smaller capillary diameter (p = 0.041). Placental vascular indices were significantly related to the number of fetal capillary vessels per villus (VI: r = 0.51, p = 0.03; FI: r = 0.48, p = 0.04; VFI: r = 0.56, p = 0.01). CONCLUSIONS: Differences in placental vascularization are present in first trimester in pregnancies with low PAPP-A and they are associated to altered 3D placental Doppler indices.

Fontes proteicas e idades de abate sobre a estrutura e ultraestrutura do intestino delgado de leitões desmamados / Sources of protein and slaughtering ages on the structure and ultra structure of the small intestine of weaned piglets

Foram realizados dois experimentos (experimento 1 - alimentação convencional e experimento 2 - alimentação das matrizes, a partir de 109 dias de gestação, na lactação e dos leitões lactentes com ração sem farelo de soja), com o objetivo de avaliar os efeitos de fontes proteicas (farelo de soja - FS, soja semi-integral extrusada - SSIE e produtos lácteos - PL) sobre a morfologia intestinal de leitões abatidos aos 0,5 e 15 dias após a desmama. Foram utilizados 27 leitões, desmamados aos 25 dias de idade, sendo que em cada idade, nove leitões foram abatidos. Utilizou-se o delineamento em blocos ao acaso, em esquema fatorial 3 x 3 (três dietas x três idades de abate). Os resultados demonstraram que os animais recebendo FS apresentaram menores alturas das vilosidades e relação vilosidade:cripta, quando comparados àqueles que receberam SSIE ou PL, não havendo, entretanto, diferenças entre estes. A altura da vilosidade e a relação vilosidade:cripta não foram afetadas pela alimentação diferenciada das matrizes e dos leitões antes da desmama. A profundidade das criptas não foi afetada pelas dietas ou idades de abate, dentro de cada experimento, em nenhum dos segmentos estudados, sendo, no entanto, menor no duodeno e maior no jejuno e íleo dos animais do exp. 2, quando comparados àqueles do exp. 1. Concluiu-se que o FS afetou negativamente a altura das vilosidades e a relação vilosidade:cripta após a desmama; que a morfologia intestinal foi mais afetada aos cinco dias, mostrando sinais de recuperação aos 15 dias após a desmama e que a alimentação das matrizes não afetou a morfologia dos segmentos do intestino delgado.

Two experiments (experiment 1 - conventional feeding and experiment 2 - feeding of the sows, starting at 109 days of pregnancy and during lactation, and the lactating piglets, with rations without soybean meal) were conducted to evaluate the effects of sources of protein (soybean meal-SBM, extruded semi-integral soybean-ESISB, and milk products-MP) on the intestinal morphology of piglets slaughtered at the 0, 5 and 15 days later at weaning. Twenty-seven piglets weaned with 25 days of age were used, being nine piglets slaughter in each slaughtering age. A 3 x 3 factorial (3 diets x 3 slaughtering ages) was studied, according to a randomized block design. The results showed that animals receiving SBM, presented lower values of villi height and villus:crypt ratio when compared to those that received ESISB or MP. The villi height and the villus:crypt ratio were not affected by the differential feeding of the sows and of the piglets before the weaning. The depth of the crypt was not affected by diets or slaughtering ages in none of the segments studied being, however, smaller in the duodenum and bigger in the jejunum and ileo of the animals of exp. 2. It was concluded that the SBM was the affected the height of the villi and the relationship villi:crypt negatively after it weans. The intestinal morphology was more affected at five days, showing signals of recovering at 15 days after weaning and that the feeding of the sows did not affect the morphology of the segments of the thin intestine.

Placental stem cell differentiation into islets of Langerhans-like glucagon-secreting cells.

BACKGROUND AND PURPOSE: For the past few years, in an attempt to find new sources of cells that may be used in cell therapy, numerous researchers have highlighted the particular properties of mesenchymal stem cells. Mesenchymal stem cells can be isolated from adult tissues such as the bone marrow or adipose tissue, but also from other organs such as the human placenta. Our study focuses adult stem cells isolated from the chorionic villi in an attempt to differentiate them into islets of Langerhans in order to study their differentiation potential, as a future background for cell therapy. EXPERIMENTAL DESIGN: Full-term placentas were prelevated from volunteer women that have just delivered a normal pregnancy. After a mechanical fragmentation of the placenta, the chorion fragments are transferred in a dish with dispase before the enzyme is inactivated using fetal calf serum. The cell suspension is filtered in order to obtain a single-cell suspension. After the adherence of the first cells, the proliferation rate increased progressively and cell morphology is kept the same for several passages. In order to correctly differentiate placental stem cells into glucagon-secreting cells, we used a culture method on a scaffold with sequential exposure to different growth factors. The underlying substrate used contained type IV collagen, chytosan, Matrigel and laminin. Molecular biology techniques were carried out to investigate the gene expression of the stem cells. RESULTS: Our results show that exendin-4 is able to induce the differentiation of placental stem cells into glucagon-secreting cells. We also notice the absence of the insulin gene, a conclusion that may be explained by the fact that our phenotype is a partial one, incomplete, closer to islet cell progenitors than to insulin-producing progenitors. CONCLUSIONS: The identification of the placenta as a valid source for stem cells has important practical advantages because it is easily accessible, it raises no ethical issues and cells are easily to isolate in a large enough number to use. The future knowledge and manipulation of the signaling pathways that determines the dramatic phenotype shift may provide the basis for efficient cell differentiation, with great impact on regenerative medicine and tissue engineering.

Quantitative research of capillaries in terminal villi of mature placentae.

Advanced maternal age is known to be a risk factor for placental dysfunctions. The most common obstetric complications among older women would be considered as follows: gestational diabetes; pre-eclampsia; placenta praevia; preterm premature rupture of membranes and the risk of preterm delivery. The aims of research were to determine the impact of maternal age on the structure of terminal villi. The study was conducted on 60 human placentae of term pregnancy divided into two groups: the control group (30 placentae in pregnant women of age between 20 and 34) and the experimental group (30 placentae in pregnant women of 35 years of age and older). Stereological methods were applied to determine the volume density, surface density, total volume and total capillary surface area in terminal villi of placenta. The mean value of volume density of capillaries in terminal villi of placentae in older pregnant women is: Vvkks = (0,376 +/- 0,033) mm(0), and the mean value of total volume is: Vkks = (157,047 +/- 25,022) cm(3). The mean value of surface density is: Svkks = (64,783 +/- 2,543) mm(-1), and the mean value of total surface area is: Skks = (29,959 +/- 7,873) m(2). Volume density of capillaries in terminal villi of placentae is significantly lower in older pregnant women (p<0.001) in comparison to the younger pregnant women. The total volume, surface density and total capillary surface area in terminal villi of placentae are also significantly lower in older pregnant women (p<0.005) in comparison to the younger pregnant women. Statistically significant lower values of volume density, total volume, surface density and total capillary surface area indicate that there is a decreased metabolic transfer between mother and foetus.