The human placenta in idiopathic intrauterine growth retardation: a light and electron microscopic study

Multiscale and multimodal imaging of utero-placental anatomy and function in pregnancy

Placental structures at the nano-, micro-, and macro scale each play important roles in contributing to its function. As such, quantifying the dynamic way in which placental structure evolves during pregnancy is critical to both clinical diagnosis of pregnancy disorders, and mechanistic understanding of their pathophysiology. Imaging the placenta, both exvivo and invivo, can provide a wealth of structural and/or functional information. This review outlines how imaging across modalities and spatial scales can ultimately come together to improve our understanding of normal and pathological pregnancies. We discuss how imaging technologies are evolving to provide new insights into placental physiology across disciplines, and how advanced computational algorithms can be used alongside state-of-the-art imaging to obtain a holistic view of placental structure and its associated functions to improve our understanding of placental function in health and disease.

Proteomic analysis of hypoxia-induced responses in the syncytialization of human placental cell line BeWo

Syncytiotrophoblast formation is affected by a number of pathological conditions and suppressed syncytiotrophoblast formation due to hypoxia may play a role in the pathogenesis of preeclampsia. However, the molecular basis of hypoxia-inhibited trophoblast syncytialization is poorly understood. To determine the effect of hypoxia on trophoblast syncytialization, a proteomic analysis was performed in the human cytotrophoblast cell line BeWo using two-dimensional electrophoresis and MALDI-TOF-TOF-MS. Hypoxia induced marked inhibition of BeWo cell fusion and differentiation. The proteomic profiling was established under hypoxia in BeWo cell syncytialization. The results showed that twenty proteins were significantly up-or down-regulated under hypoxia, compared with cells under normoxia. In response to hypoxia, three antioxidants, peroxiredoxin 1, peroxiredoxin 2 and 1-Cys peroxiredoxin, were down-regulated, two proteins involved in glycolysis pathway (malate dehydrogenase and enolase) were up-regulated. The expression of two members of the annexin family (annexin A2 and annexin A5) increased. We also found a decreased expression of 14-3-3 tau protein in hypoxia treated cells. Proteins implied in protein degradation and folding were also identified. The expression of two cytoskeleton components (keratin 1 and beta-actin) was found to be down-regulated. In addition, galectin-3 was up-regulated. These proteins have been implicated in regulating cellular oxidative stress, glycolysis, signal transduction, protein folding and degradation, cell mobility and cytoskeletal structure formation. Western blot analysis revealed that the levels of peroxiredoxin 1 and 14-3-3 tau decreased, whereas the levels of annexin A5 and annexin A2 increased in BeWo cells under hypoxia. These findings provided new insights into the molecular mechanisms in mediating cellular response to hypoxia in trophoblast syncytialization.

Ultraviolet-inactivated human cytomegalovirus induces placental syncytiotrophoblast apoptosis in a Toll-like receptor-2 and tumour necrosis factor-alpha dependent manner

Placentae obtained from newborns with congenital human cytomegalovirus (HCMV) infection often display chronic villitis and disruptions of the syncytiotrophoblast (ST). Little is known about how HCMV infection induces inflammation in the villous placenta and loss of the trophoblast. We propose that the inflammation is initiated with innate defence responses of the ST to maternal blood-borne virus. In this paper we show with a culture model (ST derived from primary cytotrophoblasts) that UV-inactivated HCMV (UV-HCMV) doubled the frequency of ST apoptosis. ST cultures challenged with UV-HCMV increased transcription and secretion of the inflammatory cytokines tumour necrosis factor alpha (TNFalpha) and interleukin-8, and antibody to TNFalpha inhibited UV-HCMV-induced apoptosis. Treatment with cycloheximide, an inhibitor of protein translation, did not reduce UV-HCMV-induced TNFalpha gene transcription, indicating that upregulation was independent of de novo protein synthesis. Neutralizing antibody to Toll-like receptor (TLR)2 inhibited UV-HCMV-induced transcription and translation of TNFalpha, and consequently inhibited the increase in ST apoptosis. Our results show that even transcriptionally inactive HCMV binding to TLR2 on ST can initiate inflammation, including secretion of TNFalpha, which leads to trophoblast death.

Impact of trisomy 21 on human trophoblast behaviour and hormonal function

Although trisomy 21 (T21) is the most frequent genetic abnormality and some maternal serum markers for this fetoplacental aneuploidy are of placental origin, little is known of its impact on placental development. We therefore studied the influence of T21 on trophoblast behaviour. Using cultured cells from 46 human T21 pregnancies, we confirmed the defective morphological and functional differentiation of the villous cytotrophoblast in this setting; indeed, villous cytotrophoblast cells aggregate normally but fuse inefficiently to form the syncytiotrophoblast. This is in part related to the abnormal oxidative status of the T21 cytotrophoblast, characterized by a gene dosage-related increase in SOD-1 (copper-zinc superoxide dismutase) expression and activity. This was associated with a significant (P < 0.01) increase in catalase activity but no significant change in glutathione peroxidase activity. On the basis of these in vitro findings and studies of large panels of maternal serum, we propose a pathophysiological explanation for trisomy 21 maternal serum markers of placental origin.

The relationship between placental histopathology findings and perinatal outcome in preterm infants

OBJECTIVE

To determine the correlation between placental histopathology findings and perinatal outcome in preterm infants.

METHODS

Placental histopathology in 774 neonates delivered at 24-32 weeks between 1992 and 2000 was classified as follows: 254 (33%) had histological chorioamnionitis, 263 (34%) had coagulation-related lesions, 228 (30%) had vasculopathy. Perinatal outcome was compared between cases positive and negative for each histopathological classification.

RESULTS

Histological chorioamnionitis occurred in 46% of cases with premature rupture of membranes and 45% with preterm labor. Positivity versus negativity for histological chorioamnionitis was associated with earlier presentation (191 vs. 205 days, p = 0.0001) and delivery (199 days vs. 209 days, p = 0.0001), increased risk of intraventricular hemorrhage (71% vs. 23%, p = 0.001, odds ratio (OR) 2.2), bronchopulmonary dysplasia (26% vs. 15%, p = 0.0001, OR 2), retinopathy (36% vs. 24%, p = 0.001, OR 1.8), neonatal sepsis (28% vs. 13%, p = 0.0001, OR 2.5) and neonatal death (12% vs. 7%, p = 0.012, OR 2). Vasculopathy versus no vasculopathy was associated with decreased birth weight (1245 g vs. 1341 g, p = 0.011), decreased Apgar score at 5 min (20% vs. 13%, p = 0.011, OR 1.7) and necrotizing enterocolitis (6% vs. 2%, p = 0.001, OR 4). Cases positive for coagulation-related lesions correlated only with necrotizing enterocolitis (5% vs. 2%, p = 0.02, OR 2.6).

CONCLUSIONS

The presence of histological chorioamnionitis significantly increases the risk of earlier delivery and neonatal mortality. Vascular and coagulation placental findings increase the risk of necrotizing enterocolitis.

Human cytomegalovirus-caused damage to placental trophoblasts mediated by immediate-early gene-induced tumor necrosis factor-alpha

Infection of the fetal epithelium (trophoblast) lining the villous placenta by human cytomegalovirus (HCMV) accompanies placental inflammations and fetal intrauterine growth restriction. However, the consequences of infection on the villous trophoblast have not been explored. We show that HCMV infection of primary immature (cytotrophoblast-like) or mature (syncytiotrophoblast-like) cultures results in loss of half of the cells within 24 hours of virus challenge. Two-color immunofluorescence of HCMV immediate early (IE) gene expression and apoptosis (terminal dUTP nick-end labeling) revealed apoptosis only in uninfected cells. Antibody to tumor necrosis factor (TNF)-alpha completely inhibited infection-induced trophoblast apoptosis and cell loss, as did co-incubation with epidermal growth factor, known to inhibit trophoblast apoptosis. Transfection with HCMV immediate early- (IE)1-72 and IE2-86, but not IE2-55, expression plasmids induced paracrine trophoblast apoptosis inhibitable by epidermal growth factor or antibody to TNF-alpha. These results show that HCMV infection of villous trophoblasts leads to rapid loss of neighboring cells mediated by viral IE protein-induced TNF-alpha secretion. We propose that HCMV infection damages the placental trophoblast barrier by accelerating trophoblast turnover and decreasing its capacity for renewal.

Hypoxia limits differentiation and up-regulates expression and activity of prostaglandin H synthase 2 in cultured trophoblast from term human placenta

OBJECTIVE

We determined the effect of hypoxic conditions on cellular differentiation and prostaglandin H synthase expression in cultured human term trophoblast.

STUDY DESIGN

Cytotrophoblasts isolated from term placentas were cultured for 24-72 hours in a standard (20% oxygen) or hypoxic (1% to 2% oxygen) atmosphere. Trophoblast biochemical differentiation was determined by release of human chorionic gonadotropin. Morphologic differentiation was evaluated by epifluorescent and confocal microscopic examination of cultures after dual cytochemical staining for surface membrane desmosomes and intracytoplasmic nuclei. Prostaglandin H synthase 2 expression was determined by Western blot analysis and correlated with enzyme activity by immunoassay of 2 prostaglandin H synthase 2 products, prostaglandin E2 and thromboxane.

RESULTS

Human chorionic gonadotropin levels in media and syncytiotrophoblast formation were markedly diminished in trophoblast cultured in hypoxia, compared with trophoblast in control cultures, whereas viability was unchanged. Hypoxia up-regulated expression of trophoblast prostaglandin H synthase 2 but not of prostaglandin H synthase 1 and increased prostaglandin E2 and thromboxane release.

CONCLUSIONS

Hypoxia limits differentiation and enhances prostaglandin H synthase 2 expression in cultured villous trophoblast. These responses may account for the cytotrophoblast prominence characteristic of placentas exposed to attenuated oxygen delivery.

Specificity of intertubular capillary changes: comparative ultrastructural studies in renal allografts and native kidneys

The pathophysiology of chronic rejection of renal allografts is poorly understood and specific morphologic markers are being sought for its diagnosis. Ultrastructural splitting and reduplication of the basal lamina of the intertubular capillaries (ITCs) have been shown to be consistently associated with transplant glomerulopathy (TG) in renal allografts and have been used as a marker of chronic allograft rejection. Although the presence of ITC abnormalities is extremely helpful diagnostically and has been considered a surrogate for the diagnosis of TG when glomeruli are not available for examination, their specificity has not been tested. This study examined 135 biopsy specimens from renal allografts and native kidneys and categorized the ITC basal lamina alterations into 5 patterns. The results showed that although marked ITC basal lamina abnormalities are characteristically seen in association with TG, lesser degrees of these changes may also be found in native kidneys and in transplants with other types of glomerulopathies. In native kidneys, splitting and reduplication of the ITC basal lamina were observed in cases of active lupus nephritis, membranoproliferative glomerulonephritis type I, crescentic glomerulonephritis, cryoglobulinemia, and hypertension. In allografts, ITC changes were seen in postinfectious proliferative glomerulonephritis, acute cyclosporin toxicity, and hemolytic uremic syndrome, in addition to cases with TG. The histopathologic diagnosis in renal diseases relies heavily on clinical, immunofluorescence, and ultrastructural findings. Therefore, in the transplantation setting, with other less common pathological processes ruled out, the presence of abnormalities of the ITC basal lamina is highly indicative of TG. This association is particularly true for cases with severe ITC abnormalities.

The effects of the antihormones RU486 and tamoxifen on fetoplacental development and placental bed vascularisation in the rat: a model for intrauterine fetal growth retardation

OBJECTIVE

To examine the effect of administration of the antihormones RU486 and tamoxifen in early pregnancy during the period of maximal decidual development in the rat upon fetoplacental and placental bed development.

DESIGN

Case-control study in an experimental animal model.

SETTING

Academic department of obstetrics and gynaecology in a UK medical school.

ANIMALS

Small laboratory animal-the rat-exhibiting haemochorial placentation.

INTERVENTION

Administration of antiprogesterone or antioestrogen (RU486 and tamoxifen respectively) during early pregnancy.

MAIN OUTCOME MEASURES

Weight of the whole pregnancy implant, fetus, mesometrial decidua and placenta; incidence of intrauterine fetal death: and histological changes in the placental bed.

RESULTS

RU486 produced resorption of all implants when administered above a threshold dose, below which it had no effect upon subsequent fetoplacental development. Tamoxifen treatment on days 9 to 11 resulted in significant reduction of decidual weight (35.1% on day 12 of pregnancy, P < 0.001). This was associated with a higher rate of implants or fetuses weighing below the 10th centile (59.6% and 5.7% on day 12, P < 0.001; 42.9% and 7% on day 16, P < 0.001; 25.4% and 7.6% on day 20, P < 0.001 in treated and control animals, respectively). This was also associated with a higher rate of intrauterine fetal death (30.7% on day 16 compared with 4.5% in controls, P < 0.001; 47.8% on day 20 compared to 0.83% in controls, P < 0.001). Histologically, the placental bed of treated animals failed to develop a dilated uteroplacental artery although trophoblast cells migrated endovascularly to a level equivalent to untreated animals.

CONCLUSIONS

RU486 had an all or none dose-dependent effect on fetoplacental development, resulting in either abortion or normal development of pregnancy. Tamoxifen produced significant impairment of decidual development, which was associated with altered blood vessel transformation in the placental bed, impaired fetoplacental development and higher incidence of growth retarded fetuses and fetal death.

Maternal placental vasculopathy and infection: two distinct subgroups among patients with preterm labor and preterm ruptured membranes

OBJECTIVE

Our aim was to find out whether patients delivered preterm because of preterm labor or preterm premature rupture of membranes can be categorized according to clinical characteristics and placental pathologic findings.

STUDY DESIGN

We performed a case-control study of 105 patients who were delivered preterm, 42 because of preterm labor and 63 because of premature rupture of membranes, and 105 patients who were delivered at term after uncomplicated pregnancies.

RESULTS

Maternal placental vascular lesions were present in 14 (34.1%) patients with preterm labor, 19 (35.1%) patients with premature rupture of membranes, and 9 (11.8%) control patients (odds ratios 3.8 and 4.0, 95% confidence intervals 1.3 to 11.1 and 1.5 to 10.8, p = 0.0065 and 0.0022, respectively). Infection of the products of conception was found in 16 patients (38%) with preterm labor, 23 patients (36.5%) with premature rupture of membranes, and 19 control patients (18%) (odds ratios 2.7 and 2.6, 95% confidence intervals 1.1 to 6.6 and 1.2 to 5.6, p = 0.017 and 0.01, respectively). Patients with maternal placental vasculopathy had significantly different characteristics compared with those of infected patients.

CONCLUSIONS

It is possible to identify two subgroups of patients among those who are delivered preterm because of preterm labor or premature rupture of membranes, one with infection of the products of conception and another with maternal placental vasculopathy.

Multiple vascular profiles in the umbilical cord; an indication of maternal smoking habits and intrauterine distress

A total of 644 umbilical cords were examined over a period of 5 years, 40 cords (6.2 per cent) showed more than the normal three vascular profiles on cross-section. Both the umbilical arteries and vein showed multiple profiles, although arterial profiles were far more commonly multiple. Clinical data were correlated with the histological findings. Heavy smoking was significantly associated with multiple vascular profiles. Maternal age and rhesus group were not significantly related however, but there was some association with primiparity. Fetuses with a gestational age between 33 and 38 weeks were significantly more likely to have multiple vessels than either fetuses beyond 38 weeks or less than 33 weeks gestation. Multiple channels also occurred significantly more frequently in still birth than in live birth cords. We suggest that multiple vascular profiles represent a response to intrauterine hypoxia. Inflammation of the cord was associated with multiple channels and suggests linkage between these two indications of fetal distress.

Intertubular capillary changes in kidney allografts: an ultrastructural study in patients with transplant glomerulopathy

Fifteen kidney allograft specimens from 14 patients with transplant glomerulopathy were investigated by electron microscopy. Intertubular capillaries of all patients showed splitting and multilayering of the basement membranes, a change recalling that observed in the glomerular basement membranes in transplant glomerulopathy. Although the severity of the lesions varied from case to case, it was, to a certain extent, constant in each specimen and correlated well with the severity of the glomerular basement membrane changes in the same patient. The similarity of the two lesions suggests a possible common pathogenetic mechanism. The constant finding of intertubular capillary splitting and multilayering in patients with transplant glomerulopathy leads to the suspicion of this condition when such changes are found in kidney samples in which glomeruli are lacking. Therefore electron microscopy could achieve a specific diagnostic relevance in this field of nephropathology.

Responsiveness to norepinephrine of the vessels supplying the placenta of growth-retarded fetuses

The effects of intravenous norepinephrine infusions on uteroplacental blood flow were studied in seven awake, chronically catheterized guinea pigs at 63 to 64 days' gestation after unilateral uterine artery ligation at days 31 to 37. An initial subpressor dose of norepinephrine (1.54 +/- 0.18 nmol/kg.min) (+/- SEM) was given, followed by a pressor dose (4.57 +/- 0.59 nmol/kg.min) that caused a 14% increase in mean arterial blood pressure. Placental blood flow as measured by the microsphere technique decreased by 24% in 11 placentas with normal-sized fetuses during the subpressor dose and by 46% during the pressor dose. In 11 placentas with growth-retarded fetuses the two norepinephrine doses reduced blood flow by 19% and 43%, respectively. These results indicate that there is no difference in adrenergic responsiveness between the vessels supplying the placenta of a normal-sized fetus and the arteries of the placenta of a growth-retarded guinea pig. It is suggested that an increase in circulating maternal catecholamine levels would affect a growth-retarded fetus more severely than the normal-sized fetus because the growth-retarded fetus even during normal conditions exists at, or even beyond, the border of imminent asphyxia and hypoglycemia.

Intrauterine growth retardation: morphometry of the microvillous membrane of the human placenta

The syncytiotrophoblast microvillous membrane of the human placenta has been investigated with quantitative analyses in cases of severe fetal growth retardation associated with a marked reduction in the surface area of exchange at the peripheral villous level. This study has shown that, in placentae of intrauterine growth-retarded infants of unknown origin, there were morphological changes in the microvillous membrane characterized by an increase in the microvillous surface density and surface enlargement factor, associated with a reduction of the intermicrovillous space. It is not possible to state whether these morphological changes represent a delayed maturation of the placental tissue, or compensatory mechanisms to improve the functional efficiency of the placenta. In pre-eclampsia, these placental changes were much less pronounced, possibly due to severe uteroplacental ischaemia in this complication of pregnancy. Despite these morphological changes, both groups of placentae showed significant reductions in absolute values for the microvillous and total trophoblastic surface areas, which can have major implications on the functional efficiency of the placenta.

Fetal microcirculation of abnormal human placenta. I. Scanning electron microscopy of placental vascular casts from small for gestational age fetus

The latex injection-corrosion cast technique coupled with scanning electron microscopy was applied to the study of small for gestational age placentas. The main ultrastructural changes observed in the fetal vasculature of small for gestational age placentas were less branching of arteries and veins, capillaries with variable diameters, and many capillary bud projections; also numerous "H"-shaped anastomoses were present in the capillary network. The corrosion/cast technique approach enabled us to visualize the three-dimensional distribution of arteries, veins, and capillary network as well as the ultrastructural alterations among the various-sized vessels in the abnormal placenta. Light microscopic examination of these placentas revealed numerous syncytial knots and fibrinoid deposits pressing on arteriolar and capillary vessels at different locations. We suggest that the numerous capillary buds and anastomoses are characteristics of neovascularization and may be a compensatory phenomenon of the capillary network. This information could shed new light on alterations of physiologic functions of the pathologic placenta.

Behavioural states in growth-retarded human fetuses

Behavioural state observations were carried out on 12 fetuses which subsequently had birthweights below the 10th percentile. Their gestational ages at the time of study ranged from 32 to 40 weeks. Real-time ultrasound scanning was used to detect fetal body and eye movements, and the fetal heart rate was continuously recorded using a clinical fetal monitor. None of these fetuses was severely acidemic or depressed at birth. Findings in the growth-retarded fetuses were compared with those obtained in the fetuses of 14 low risk nulliparae and 14 low risk multiparae by means of the same techniques (van Vliet et al. (1985) Early Hum. Dev., 12, 121-135.; Nijhuis et al. (1982) Early Hum. Dev., 6, 177-195). The appearance of states seemed to be delayed in the growth-retarded fetuses. States were present in only three of eight growth-retarded fetuses studied at 40 weeks, whereas only one of 16 low risk fetuses did not show states at this age. Also at 40 weeks, the proportion of discordant association of the state variables was increased in the growth-retarded fetuses in comparison to the low risk group. There were no consistent differences between the two groups in the occurrence of defined combinations of parameters of the state variables at earlier ages. The growth-retarded fetuses showed differences in the quality and quantity of somatic motility in comparison to low risk fetuses of equivalent gestational age. These observations suggest that some aspects of central nervous system function are disturbed in growth-retarded fetuses, even in the absence of fetal distress.

Quantitative structural studies on human placentas associated with pre-eclampsia, essential hypertension and intrauterine growth retardation

Placentas from pregnancies complicated by pre-eclampsia, essential hypertension, hypertension complicated by pre-eclampsia and from normotensive pregnancies resulting in the birth of a singleton small-for-dates (SFD) infant have been studied by quantitative morphometry. The findings have been compared with those from placentas of uncomplicated pregnancies. The placentas from pregnancies complicated by pre-eclampsia and those resulting in a SFD baby had a significantly lower total volume, volume of parenchyma and villous surface area when compared with normal pregnancies of comparable gestation. They also had an increase in areas of multiple infarction and in the volume proportions occupied by fetal capillaries. The placentas from women with essential hypertension uncomplicated by pre-eclampsia were as large as those from normal pregnancies and the villous surface areas were as high. Villous surface area measurements in the different groups were related to gestation and to fetal weight.