The human placenta – An alternative for studying foetal exposure

Antibiotic Treatment of Dogs and Cats during Pregnancy

The use of pharmacological agents in pregnant females poses a major clinical challenge due to the marked physiological changes that may modify the pharmacokinetics of drugs and to the potential effects on the fetus. The purpose of this paper is to review briefly our knowledge on the use of antibacterial drugs during pregnancy and to provide information for the judicious selection of an antimicrobial treatment for use in pregnant bitches and queens. The risk to the fetus is a result of the ability of a drug to reach the fetal circulation and to produce toxic effects. The placenta functions as a barrier that protects the fetus due to the presence of transporters and metabolising enzymes; however, during pregnancy, the presence and activity of both enzymes and transporters may change. Antimicrobial agents that have been shown to be safe for use during pregnancy include betalactams, macrolides, and lincosamides. Pharmacotherapy during pregnancy in all species may affect adversely the developing fetus; therefore, it should be avoided when possible.

Heavy metals (lead, cadmium and mercury) in maternal, cord blood and placenta of healthy women

Lead, cadmium and mercury were measured in placental tissue, umbilical cord and maternal blood samples of 1578 women who delivered at the Al-Kharj King Khalid Hospital between 2005 and 2006. The aim of this study was to evaluate the status of heavy metal exposure in mothers and their newborns and to identify predictors of maternal exposure. Lead was detected in all cord and maternal blood and in 96% of placental tissues. Only in 0.89% and 0.83% of cord and maternal blood samples were the levels of lead above the CDC threshold limit of 10 μg/dl. Maternal blood lead was also higher (2.3%) than the German Reference value in women of 7 μg/dl. Approximately 9.3% of women had a placental lead above the 95th percentile in the range of 0.83-78 μg/g dry wt., a level of possible developmental toxicity. Cadmium was detected in 94.8% and 97.9% of cord and maternal blood samples respectively, though only five newborns had a cadmium level above the OSHA threshold limit of 5 μg/l. Comparing our results to the newly revised German Reference value for nonsmokers, 48.6% of mothers had blood cadmium levels >1.0 μg/l. We found as well that 25% of women had placental cadmium in the >75th percentile, in the range of 0.048-4.36 μg/g dry wt., which is likely to affect fetal growth and development. Of the maternal and cord blood samples, 11.2% and 13%, respectively, had mercury levels >5.8 μg/l, which is the EPA reference dose. Nearly 49% of women had mercury levels >2.0 μg/l, the German Reference value for those who consume fish ≤3 times a month. Around 50% of the mothers had placental mercury in the range of 0.031-13.0 μg/g dry wt. Regression analyses indicated that the levels of metals in the blood and placenta were influenced by several factors. This study provides informative baseline biomonitoring data and reveals a substantial exposure to heavy metals in non-occupationally exposed Saudi mothers and their newborns that might jeopardize the health of both. Additional research is also urgently needed to explore factors such as environment, diet, lifestyle and/or cultural habits contributing to maternal and fetal exposures. Preventive measures to eliminate or minimize the unnecessary risk of fetus exposure to heavy metals or other pollutants during pregnancy should be initiated once these factors are identified.

[Contributions of the ex vivo human perfused placenta in the study of placental transfer of drugs]

Perfused human placental lobule was developed during the 1970s. Only this model respects the anatomical features of the human placenta. This approach allows different technical conditions (concentrations of drugs…) without ethical problems. Limitations of this ex vivo model are detailed in this review, also its recent contributions in better understanding of placental passage of drugs.

Polybrominated diphenyl ethers in paired samples of maternal and umbilical cord blood plasma and associations with house dust in a Danish cohort

Brominated flame retardants (BFRs), in particular the polybrominated diphenyl ethers (PBDEs), have been used in consumer products for many years to increase fire resistance. Recently, developmental neurotoxicity at very low levels has increased the concern about these compounds. The major objectives of this study were to investigate the maternal and fetal exposure to PBDEs on the basis of maternal and umbilical cord plasma samples and to study the extent of placental transfer for different PBDE congeners. The findings were also compared with previously observed PBDE levels and patterns determined in placental tissue from the same individuals, and the relationship with the external exposure from house dust from the participants' homes was explored. Samples of maternal and umbilical cord plasma from a cohort of 51 pregnant women from the Copenhagen area were collected. Paired maternal and umbilical cord plasma were analysed for BDE-28, 37, 47, 85, 99, 100, 119, 138, 153, 154, 183, 209 and the brominated biphenyl BB-153 using automated SPE extraction and GC-HRMS for the tri- to hepta-BDEs and GC-LRMS (ECNI) for BDE-209. PBDEs were detected in all maternal and umbilical cord plasma samples. The sum of tri- to hexa-BDEs (SigmaPBDE) in maternal plasma varied between 640 and 51,946 pg/g lipid weight (lw) with a median level of 1765 pg/g lw. In the umbilical cord samples SigmaPBDE varied between 213 and 54,346 pg/g lw with a median of 958 pg/g lw. The levels observed in fetal and maternal plasma were highly correlated, but the placental transport of PBDE congeners was found to decrease with increasing diphenyl ether bromination. Maternal concentrations were significantly correlated (p<0.05) for most congeners with the previously determined concentrations in placental tissue from the same individuals. Furthermore, positive correlations (p<0.05) were found for BDE-28, 47, 100, 209 and SigmaPBDE in maternal plasma and house dust as well as for SigmaPBDE in umbilical cord plasma and house dust. The positive correlations for PBDEs for both maternal and umbilical cord plasma with house dust showed that domestic house dust is a significant source of human exposure to PBDEs in Denmark including in utero exposure.

Optimization of the matrix solid phase dispersion extraction procedure for the analysis of polybrominated diphenyl ethers in human placenta

Characterization of prenatal exposure to hazardous chemicals most often relies upon the analysis of cord blood. However, human placenta is an appropriate tissue alternative with noteworthy advantages. Owing to analytical challenges, reports on placental levels of toxic chemicals are limited. The purpose of this study was to establish a reliable, cost-effective, and relatively fast and simple method to extract polybrominated diphenyl ethers (PBDEs) from human placenta for analysis using gas chromatography coupled with mass spectrometry (GC/MS). The matrix solid phase dispersion (MSPD) method was optimized for the extraction and analysis of 43 PBDEs (including BDE209) from human placenta samples. Different sorbents, sample conditions, grinding methods, elution solvents, and single and repeated extractions were compared for their effects on the extraction efficiency. The performance of the optimized method was validated by analyzing spiked placenta samples and a standard reference material of fish tissue. Congener specific PBDE recovery ranged from 91% to 114% for the spiked samples and 89% to 115% for a standard reference material (SRM) of fish tissue. The optimized MSPD procedure was compared with two conventional extraction methods. The extraction efficiency of MSPD was found to be comparable with that of the traditional Soxhlet method and superior to that using a liquid extraction method. Twenty two PBDEs were detected in all of the five samples collected in Chicago in 2008. This is the first description of PBDEs detected in human placentas in the U.S.

Nitrofurantoin transport by placental choriocarcinoma JAr cells: involvement of BCRP, OATP2B1 and other MDR transporters

OBJECTIVE

To determine the role of BCRP in nitrofurantoin (NF) transport in JAr cells and the possible contribution of OATP2B1, P-gp and MRPs to this transport.

METHODS

Cells were incubated with various BCRP, P-gp, MRPs, organic anion transporting polypeptide (OAT) and OATP2B1 inhibitors for 15 min, followed by incubation for 30 min with NF, with or without the inhibitors mentioned earlier. NF cytotoxicity was examined using neutral red (NR) assay. Intracellular NF levels were analyzed by HPLC.

RESULTS

NR assay showed that incubation conditions with NF (as carried out in our experiments) were not cytotoxic. Incubation with specific inhibitors of BCRP (FTC, Chrysin and Novobiocin), showed a significant increase in NF accumulation in the cells. Inhibitors of OATP2B1 (EGCG and BSP) had no influence on NF accumulation. Specific inhibitors of P-gp and MRPs (Verapamil and Indomethacin, respectively) also had no influence on NF accumulation in JAr cells.

CONCLUSIONS

NF is probably a specific substrate of BCRP, and BCRP has a major active role in NF transport in JAr cells. For the first time, we showed, that P-gp, MRPs, and the OATP2B1, probably have a negligible contribution to NF transport in JAr cells.

Modeling placental transport: correlation of in vitro BeWo cell permeability and ex vivo human placental perfusion

The placental passage of three compounds with different physicochemical properties was recently investigated in ex vivo human placental perfusion experiments (caffeine, benzoic acid, and glyphosate) [Mose, T., Kjaerstad, M.B., Mathiesen, L., Nielsen, J.B., Edelfors, S., Knudsen, L.E., 2008. Placental passage of benzoic acid, caffeine, and glyphosate in an ex vivo human perfusion system. J. Toxicol. Environ. Health, Part A 71, 984-991]. In this work, the transport of these same three compounds, plus the reference compound antipyrine, was investigated using BeWo (b30) cell monolayers. Transport across the BeWo cells was observed in the rank order of caffeine>antipyrine>benzoic acid>glyphosate in terms of both the apparent permeability coefficient and the initial slope, defined as the linear rate of substance transferred to the fetal compartment as percent per time, a parameter used to compare the two experimental models. The results from the in vitro studies were in excellent agreement with the ex vivo results (caffeine approximately antipyrine>benzoic acid>glyphosate). However the transfer rate was much slower in the BeWo cells compared to the perfusion system. The advantages and limitations of each model are discussed in order to assist in the preparation, prediction, and performance of future studies of maternal-fetal transfer.

Patterns and concentration levels of polybrominated diphenyl ethers (PBDEs) in placental tissue of women in Denmark

The levels and congener patterns of PBDEs were investigated in human placental samples in Denmark. The median concentrations of sigmaPBDE(tri-hepta) and BDE-209 in the 50 samples were 1.22 and 1.14 ng g(-1) lw, respectively, with the total sum ranging from 0.51 to 17.1 ng g(-1) lw, which is similar to previous placental studies. The PBDE content in placental tissue was dominated by BDE-209, which accounted for approximately 50% of the total amount of PBDEs. BDE-47, -99, and -153 were detected in all samples. Approximately equal amounts of BDE-47 and BDE-153 were observed in the placental tissue, which is in agreement with previous European studies of human serum. Principal Component Analysis (PCA) was performed to analyze congener patterns within and between mothers. The loading plot showed groupings of the measured PBDE variables in three groups, representative of Penta-, Octa- and Deca-BDE technical mixtures. Congeners representing the individual technical mixtures were close to orthogonal or inversely correlated, indicating variation in the congener patterns of internal exposure corresponding to the patterns of technical mixtures used in products. Visualisation of the participant objects according to body mass index (BMI), revealed inherent congener patterns (19% X-variance) showing increased frequency for participants within the highest BMI group to have elevated concentrations of BDE-209 in the placental tissue.

Is serum gamma-glutamyltransferase a marker of exposure to various environmental pollutants?

It was previously hypothesized that serum gamma-glutamyltransferase (GGT) within its reference range predicts various clinical outcomes as a sensitive marker of oxidative stress in humans. This study further hypothesizes that serum GGT can mark exposure to various environmental pollutants, based both on recent epidemiological findings and on well-established biochemical features of cellular GGT. Cellular GGT is a prerequisite for metabolism of GSH conjugates that detoxify xenobiotics to mercapturic acid. Under this concept, serum GGT may increase with increasing exposure to environmental pollutants which need to be conjugated to GSH. Supporting this concept, it was recently reported that serum GGT within its reference range was linearly associated with important environmental pollutants, including lead, cadmium, dioxin and organochlorine pesticides. As a marker of the amount of conjugated xenobiotics, recent epidemiological findings about serum GGT imply the possibility of harmful effects of various environmental pollutants at background levels currently regarded as safe.

Carrier-mediated uptake of Levofloxacin by BeWo cells, a human trophoblast cell line

OBJECTIVE

Placental transfer of Levofloxacin (LF), a broad spectrum fluoroquinolone antibiotic, and its inhibition was investigated in BeWo cells, a human trophoblast cell line.

METHODS

The experiments of LF uptake by BeWo cells were performed after preincubation and in the presence of the P-glycoprotein inhibitors (Cyclosporin A, Verapamil and Quercetin), the organic anion/cation transporter inhibitor (Cimetidine) and the MCT substrates (lactic acid and salicylic acid).

RESULTS

P-glycoprotein inhibitors increased the uptake of LF by BeWo cells. The increase in LF accumulation by Cyclosporin A, Verapamil and Quercetin was by 30, 90 and 80%, respectively. Cimetidine, the organic cation inhibitor, increased the transport of LF by 48%. Lactic acid and salicylic acid, the MCT substrates, initially decreased the accumulation of LF by 30% and subsequently increased the uptake of LF by 500 and 53%, respectively.

CONCLUSIONS

The uptake of LF by human trophoblast cells is mediated by multiple transporters as well as passive diffusion.

Progesterone levels in cesarean and normal delivered term placentas

BACKGROUND

One of the most important hormones synthesized by the placenta during pregnancy is progesterone. The regulating mechanisms of progesterone synthesis and the mechanism responsible for the spontaneous onset of labor in women are still not fully understood. Progesterone is thought to have been involved in human parturition. The objective of this study was to compare the levels of progesterone in the human placentas, at the end of the gestation (37-41 weeks) in vaginal versus cesarean deliveries, and to evaluate the pattern of progesterone accumulation, instantly following its synthesis by the human placenta at the end of the pregnancy.

METHODS

Progesterone levels in human placental tissue were determined by immunochemiluminescent analysis, following tissue homogenization. Progesterone secretion and accumulation pattern in the placental tissue was demonstrated using the ex vivo, closed, dual perfusion system of isolated human placental cotyledon.

RESULTS

Immunochemiluminescent analysis of progesterone levels in human normal and cesarean-delivered placentas showed that placentas following normal vaginal delivery store higher concentrations of progesterone, and produce progesterone more intensively. Results obtained from 120-min perfusions (of vaginal and cesarean-delivered placentas) showed that progesterone tended to accumulate in the maternal rather than the fetal compartment.

CONCLUSIONS

These data indicate that progesterone levels continuously rise till the end of pregnancy, with no apparent drop in progesterone levels during the labor process. In addition, progesterone is released from the syncytiotrophoblast preferably into the maternal component of the placental tissue.

Perinatal exposure to brominated flame retardants and polychlorinated biphenyls in Japan

Brominated flame retardants (BFRs) are used to prevent combustion in consumer products. Examples of BFRs are polybrominated diphenyl ethers (PBDEs), tetrabromobisphenol A (TBBPA), and tribromophenol (TBP). These compounds are reported to have adverse effects on human health and endocrine disrupting effects. The purpose of this study was to identify the Japanese perinatal exposure to PBDEs, hydroxylated PBDE metabolites (OH-PBDEs), TBBPA, and TBP compared with polychlorinated biphenyls (PCBs) and hydroxylated PCB metabolites (OH-PCBs). We investigated the concentrations of these compounds in maternal blood, maternal milk, cord blood, and umbilical cords from 16 Japanese mother-infant pairs by HRGC/HRMS. PBDEs were detected in all samples of maternal blood (mean+/-SD; median=25+/-23 pg/g; 18 pg/g wet weight), maternal milk (140+/-220 pg/g; 59 pg/g wet weight), cord blood (4.8+/-6.5 pg/g; 1.6 pg/g wet weight), and umbilical cords (3.1+/-3.1 pg/g; 2.1 pg/g wet weight). The mothers were divided into two groups, a high-concentration group and a low-concentration group. The percentage of BDE-47 showed the greatest difference between the two groups. 6-OH-BDE-47, TBBPA, and TBP were detected in all umbilical cord samples (mean+/-SD; median=8.4+/-8.1 pg/g; 8.0 pg/g, 16+/-5.5 pg/g; 15 pg/g, and 33+/-8.2 pg/g; 32 pg/g wet weight respectively), but not in all maternal blood or cord blood samples. These results indicate that OH-PBDEs, TBBPA, and TBP, in addition to PBDEs, PCBs, and OH-PCBs, pass through the blood-placenta barrier and are retained in the umbilical cord.

PPAR-gamma signaling pathway in placental development and function: a potential therapeutic target in the treatment of gestational diseases

BACKGROUND

PPAR-gamma is a target for the treatment of metabolic disorders, as Pioglitazone and Rosiglitazone are already used against type 2 diabetes. Pleiotropic functions, such as antiproliferative and anti-inflammatory effects against several pathological states, including cardiovascular disease and cancer, are currently being explored in clinical studies.

OBJECTIVE

Evidence indicates that PPAR-gamma is expressed in the placenta, playing a crucial role in placental development and function, while PPAR-gamma ligands appear to modulate fetal membrane signals. Thus, in the last few years, the pivotal role of PPAR-gamma in placental biology has been the focus of extensive research, as diabetes appears to be the most common metabolic dysfunction in pregnancy.

METHODS

We aim to present data concerning the expression of PPAR-gamma in animal and human placenta, underlining its significance in normal placental development and several gestational diseases. The effects of PPAR-gamma ligands as modulators of placental biology in normal and certain pathological conditions are also discussed.

RESULTS/CONCLUSION

Current research provides substantial evidence that PPAR-gamma plays a pivotal role in placental biology and may reveal new perspectives in the treatment of gestational diseases.

In Vitro Models Using the Human Placenta to Study Fetal Exposure to Drugs

Over the recent years there has been a gradual rise in the use of pharmaceuticals during pregnancy. Knowledge on placental drug transfer and metabolism has increased during the past decades as well. Investigation of the transplacental transfer of any therapeutically useful drug is essential to the understanding of its metabolic processes and is a prerequisite for its use during pregnancy. The purpose of this review is to give insight on the various techniques that have been developed to evaluate transplacental transfer of drugs and xenobiotics.

An animal model of cigarette smoke-induced in utero growth retardation

Maternal/fetal genetic constitution and environmental factors are vital to delivery of a healthy baby. In the United States (US), a low birth weight (LBW) baby is born every minute and a half. LBW, defined as weighing less than 5.5 lbs at birth, affects nearly 1 in 12 infants born in the US with resultant costs for the nation of more than 15 billion dollars annually. Infant birth weight is the single most important factor affecting neonatal mortality. Various environmental and genetic risk factors for LBW have been identified. Several risks are preventable, such as cigarette smoking during pregnancy. Over one million babies are exposed prenatally to cigarette smoke accounting for over 20% of the LBW incidence in the US. Cigarette smoke exposure in utero results in a variety of adverse developmental outcomes with intrauterine growth restriction and infant LBW being the most well documented. However, the mechanisms underlying the causes of LBW remain poorly understood. The purpose of this study was: (1) to establish an animal model of cigarette smoke-induced in utero growth retardation and LBW using physiologically relevant inhalation exposure conditions which simulate "active" and "passive" tobacco smoke exposures, and (2) to determine whether particular stages of development are more susceptible than others to the adverse effects of in utero smoke exposure on embryo/fetal growth. Pregnant C57BL/6J mice were exposed to cigarette smoke during three periods of gestation: pre-/peri-implantation (gestational days [gds] 1-5), post-implantation (gds 6-18), and throughout gestation (gds 1-17). Reproductive and fetal outcomes were assessed on gd 18.5. Exposure of dams to mainstream/sidestream cigarette smoke, simulating "active" maternal smoking, resulted in decreases in fetal weight and crown-rump length when exposed throughout gestation (gds 1-17). Similar results were seen when dams were exposed only during the first 5 days of gestation (pre-/peri-implantation period gds 1-5). Exposure of dams from the post-implantation period through gestation (gds 6-18) did not result in reduced fetal weight, although a significant reduction in crown-rump length remained evident. Interestingly, maternal sidestream smoke exposure, simulating exposure to environmental tobacco smoke (ETS), during the pre-/peri-implantation period of development also produced significant decreases in fetal weight and crown-rump length. Collectively, results from the present study confirm an association between prenatal exposure to either "active" or "passive" cigarette smoke and in utero growth retardation. The data also identify a period of susceptibility to in utero cigarette smoke exposure-induced growth retardation and LBW during pre-/peri-implantation embryonic development.