Antoine Malek

Evolution of maternofetal transport of immunoglobulins during human pregnancy

PROBLEM: We determined the evolution of the maternal‐fetal transport of immunoglobulins during human pregnancy.

Barrier Capacity of Human Placenta for Nanosized Materials

Background Humans have been exposed to fine and ultrafine particles throughout their history. Since the Industrial Revolution, sources, doses, and types of nanoparticles have changed dramatically. In the last decade, the rapidly developing field of nanotechnology has led to an increase of engineered nanoparticles with novel physical and chemical properties. Regardless of whether this exposure is unintended or not, a careful assessment of possible adverse effects is needed. A large number of projects have been carried out to assess the consequences of combustion-derived or engineered nanoparticle exposure on human health. In recent years there has been a growing concern about the possible health influence of exposure to air pollutants during pregnancy, hence an implicit concern about potential risk for nanoparticle exposure in utero. Previous work has not addressed the question of whether nanoparticles may cross the placenta. Objective In this study we investigated whether particles can cross the placental barrier and affect the fetus. Methods We used the ex vivo human placental perfusion model to investigate whether nanoparticles can cross this barrier and whether this process is size dependent. Fluorescently labeled polystyrene beads with diameters of 50, 80, 240, and 500 nm were chosen as model particles. Results We showed that fluorescent polystyrene particles with diameter up to 240 nm were taken up by the placenta and were able to cross the placental barrier without affecting the viability of the placental explant. Conclusions The findings suggest that nanomaterials have the potential for transplacental transfer and underscore the need for further nanotoxicologic studies on this important organ system.

Maternal-fetal transport of immunoglobulin G and its subclasses during the third trimester of human pregnancy

PROBLEM: We determined the maternal‐fetal transport of immunoglobulin G (IgG) during the third trimester of human pregnancy.

Multipotent mesenchymal stem cells from human placenta: critical parameters for isolation and maintenance of stemness after isolation

OBJECTIVEnThis study was undertaken to isolate and characterize multipotent mesenchymal stem cells from term human placenta (placenta-derived mesenchymal stem cells, PD-MSCs).nnnSTUDY DESIGNnSequential enzymatic digestion was used to isolate PD-MSCs in which trypsin removes the trophoblast layer, followed by collagenase treatment of remaining placental tissue. Karyotype, phenotype, growth kinetics, and differentiability of PD-MSC isolates from collagenase digests were analyzed.nnnRESULTSnPD-MSC isolation was successful in 14 of 17 cases. Karyotyping of PD-MSC isolates from deliveries with a male fetus revealed that these cells are of maternal origin. Flow cytometry and immunocytochemistry confirmed the mesenchymal stem cell phenotype. Proliferation rates of PD-MSCs remained constantly high up to passage 20. These cells could be differentiated toward mesodermal lineage in vitro up to passage 20. Nonconfluent culture was critical to maintain the MSC stemness during long-term culture.nnnCONCLUSIONnTerm placenta constitutes a rich, very reliable source of maternal mesenchymal stem cells that remain differentiable, even at high passage numbers.

Human Placental Transport of Oxytocin

Oxytocin (OX) has been suggested as a signal for parturition. Although OX is produced by both mother and fetus, concentrations are higher in umbilical than maternal blood. In addition, umbilical artery OX concentrations (15-40 pg/ml) are higher than umbilical vein (4-12 pg/ml) and maternal (1-10 pg/ml) concentrations. The umbilical A-V difference suggests that placental uptake and transport may be one path from fetal (F) to maternal (M) circulation. However, this difference may also reflect placental oxytocinase activity, which is known to metabolize biologically active peptides such as OX. We have investigated placental transport of OX from F to M and M to F circulation using in vitro dually perfused isolated cotyledons from term human placenta. Term human placentae from uncomplicated pregnancies were obtained immediately after delivery. A single peripheral cotyledon and corresponding lobule was cannulated and perfused. After stabilization and demonstration of adequate M to F perfusion-perfusion overlap, we studied the transport of OX (3H) with 14C-inulin (14C-IN) as permeability reference in both M to F (n = 8) and F to M (n = 6) directions during 2 h of perfusion. In addition to the higher tissue uptake observed in M to F than F to M transport direction as measured by the drop in the concentration of both 3H-OX and 14C-IN in the circuits in which both compounds were added, the same trend was found for the transfer rates of both compounds. These transfer rates which reflect the permeability of placental tissue to OX and IN were 15.17 +/- 2.79 (mean +/- SD) and 6.28 +/- 0.93 microliters/min/g (M to F) and 11.79 +/- 1.77 and 4.91 +/- 0.81 microliters/min/g (F to M). Although the permeability of both compounds is higher in the M to F than in the F to M transport direction, comparing these permeability values with respect to their molecular weight (MW) showed a significant correlation when known permeability values of polar compounds between MW 60 and 68,000 daltons were included. This correlation indicates that OX crosses the placenta in both directions by simple diffusion. High-performance liquid chromatography analysis showed that there is little evidence of placental metabolism and degradation of OX over the period of these experiments. Oxytocin is the main therapeutic drug that is frequently used in obstetrics for the induction of labor and parturition. Under such circumstances and with respect to the placental permeability results, oxytocin could reach the fetal circulation.

Transport of proteins across the human placenta.

PROBLEM: The transport of various proteins across the human placenta was investigated by comparing maternal and fetal concentrations of tetanus antigen (TT‐AG), anti‐tetanus (TT)‐immunoglobulin G (IgG) (following maternal vaccination), IgA, human chorionic gonadotropin (hCG), human placental lactogen (hPL), and alpha‐fetoprotein (AFP) at term.

Reproductive toxicity: male and female reproductive systems as targets for chemical injury.

On the basis of current knowledge of reproductive biology and toxicology, it is apparent that chemicals affecting reproduction may elicit their effects at a number of sites in both the male and the female reproductive system. This multiplicity of targets is attributable to the dynamic nature of the reproductive system, in which the hypothalamic-pituitary-gonadal axis is controlled by precise positive and negative feedback mechanisms among its components. Interference by a xenobiotic at any level in either the male or the female reproductive system may ultimately impair hypothalamic or pituitary function. Normal gonadal processes such as spermatogenesis or oogenesis, ejaculation or ovulation, hormone production by Leydig or granulosa cells, and the structure or function of the accessory reproductive structures (e.g., epididymis, fallopian tube) also appear vulnerable to xenobiotics. The reproductive system is a complex one that requires local and circulating hormones for control. This brief review illustrates a system for characterizing the mechanism of action of reproductive toxicants, as well as for defining the sites available for disruption of reproduction. Unfortunately, at present, data addressing the actual vulnerability of reproduction are sorely lacking. However, when experiments have been conducted and combined with epidemiologic data or clinical observation, it has been possible to demonstrate impairment of reproductive processes by xenobiotics. The role of environmental exposure to xenobiotics in the increase in infertility that has been observed remains to be defined.

Transport of immunoglobulin G and its subclasses across the in-vitro perfused human placenta

OBJECTIVEnThe transport of immunoglobulin G and its subclasses 1 to 4 was investigated in the in vitro-perfused isolated cotyledon of the human placenta.nnnSTUDY DESIGNnAn in vitro system with separate perfusion of the villous capillary system (fetal compartment) and the corresponding intervillous space (maternal compartment) was set up in an isolated cotyledon of human term placenta. After a 2-hour control phase with both compartments perfused in a closed circuit with NCTC-135 tissue culture medium together with Earls balanced salt solution (2:1), media were exchanged in both circuits and for the experimental phase immunoglobulin G (Sandoglobulin) together with carbon 14-labeled bovine serum albumin (5-10 microCi) was added to the maternal compartment at a concentration of 6 gm/L. During the experimental phase, lasting between 2 and 5 hours, samples were taken from the maternal and fetal compartments every 30 minutes up to 2 hours and every 60 minutes thereafter.nnnRESULTSnDuring the control phase immunoglobulin G appeared in the maternal perfusate and reached a plateau at 60 to 80 mg/L, whereas the concentration in the fetal perfusate did not exceed 20 mg/L. A similar pattern of release was observed for hemoglobin, suggesting a washout of remains of blood from the intervillous space and the villous vascular compartment. After addition of immunoglobulin G to the maternal circuit during the first 2 hours in three of four experiments, no change in immunoglobulin G concentration was seen in the fetal circuit, and only in the fourth and fifth hours did the fetal concentration increase to 0.6% of the maternal concentration. In contrast, carbon 14-labeled bovine serum albumin was already detectable in the fetal circuit after 1 hour, but the level remained constant at 0.1% of the maternal concentration. Total immunoglobulin G transfer was estimated at 0.5% of the amount added to the maternal circulation, which was five times higher than total transfer of bovine serum albumin. Transfer was shown for all four subclasses. At the end of the experiment the ratio of immunoglobulin G1 to immunoglobulin G2 in the fetal perfusate was significantly higher than in the maternal perfusate (3.8 vs 1.8), suggesting preferential transfer of immunoglobulin G1.nnnCONCLUSIONnTransfer of all four immunoglobulin G subclasses of a commercially available immunoglobulin G preparation across the human placenta from the maternal to the fetal side was demonstrated by the dual in vitro perfusion system. There is a preferential transfer for immunoglobulin G1.

Protein Transport Across the In Vitro Perfused Human Placenta

PROBLEM: Placental transport of various proteins present in human serum, such as immunoglobulins (IgG, IgA), specific anti‐tetanus IgG (anti‐TT‐IgG), and tetanus toxoid‐antigen (TT‐AG), was investigated. In addition, the transport of IgG modified with biotin (IgG‐BT) and 14C‐bovine serum albumin (14C‐BSA, a permeability marker for macromolecules), was assessed.

The impact of cocaine and heroin on the placental transfer of methadone

BackgroundMethadone is the therapeutic agent of choice for the treatment of opiate addiction in pregnancy. The co-consumption (heroin, cocaine) which may influence the effects of methadone is frequent. Therefore, the impact of cocaine and heroin on the placental transfer of methadone and the placental tissue was investigated under in vitro conditions.MethodsPlacentae (n = 24) were ex-vivo perfused with medium (m) (control, n = 6), m plus methadone (n = 6), m plus methadone and cocaine (n = 6) or m plus methadone and heroin (n = 6). Placental functionality parameters like antipyrine permeability, glucose consumption, lactate production, hormone production (hCG and leptin), microparticles release and the expression of P-glycoprotein were analysed.ResultsMethadone accumulated in placental tissue. Methadone alone decreased the transfer of antipyrine from 0.60 +/- 0.07 to 0.50 +/- 0.06 (fetal/maternal ratio, mean +/- SD, P < 0.01), whereas the combination with cocaine or heroin increased it (0.56 +/- 0.08 to 0.68 +/- 0.13, P = 0.03 and 0.58 +/- 0.21 to 0.71 +/- 0.24; P = 0.18). Microparticles (MPs) released from syncytiotrophoblast into maternal circuit increased by 30% after cocaine or heroin (P < 0.05) and the expression of P-glycoprotein in the tissue increased by ≥ 49% after any drug (P < 0.05). All other measured parameters did not show any significant effect when methadone was combined with cocaine or heroine.ConclusionThe combination of cocaine or heroin with methadone increase antipyrine permeability. Changes of MPs resemble findings seen in oxidative stress of syncytiotrophoblast.