Fractal dimensions and branching characteristics of placental chorionic surface arteries

Prenatal exposure to phthalates and phthalate replacements in relation to chorionic plate surface vasculature at delivery

Pregnant people are ubiquitously exposed to endocrine-disrupting phthalates through consumer products and food. The placenta may be particularly vulnerable to the adverse effects of phthalates, with evidence from animal models suggesting impacts on placental development and vascularization. We translate this research to humans, examining gestational exposure to phthalates and phthalate replacements in relation to novel markers of chorionic plate surface vascularization. Phthalate and phthalate replacement metabolites were measured in first trimester urine from pregnant participants in the Understanding Pregnancy Signals and Infant Development (UPSIDE) cohort (n = 154). At delivery, placentae underwent specialized 2D and 3D digital imaging to quantify chorionic plate surface vasculature. Using weighted quantile g-computation mixtures methods as well as multivariable linear regression models examining individual metabolites, we evaluated associations with overall chorionic plate surface area and five chorionic plate surface vascular measures, adjusting for covariates. We additionally examined interactions with placental sex. Exposure to a phthalate mixture was associated with longer total arterial arc length (β = 9.64 cm; 95%CI: 1.68, 17.59), shorter mean arterial arc length (β = -0.07 cm; 95%CI: -0.14, -0.01), and more arterial branch points (β = 5.77; 95%CI: 1.56, 9.98), but not chorionic plate surface area. In models considering individual metabolites and their molar sums, results were strongest for the metabolites of Di-isobutyl phthalate (DiBP), Di-isononyl phthalate (DiNP), and Di(2-ethylhexyl) phthalate (DEHP). Associations with metabolites of phthalate replacements tended to be in the same direction but weaker. Few sex differences were observed. Gestational phthalate exposure may be associated with alterations in placental chorionic plate surface vasculature characterized by more branching and shorter segments. These alterations may have implications for placental perfusion and suggest a placental mechanism by which phthalates may impact fetal development.

PFAS alters placental arterial vasculature in term human placentae: A prospective pregnancy cohort study

INTRODUCTION

Perfluoroalkyl substances (PFAS) are synthetic chemicals used in industrial and consumer goods that are widely detected in human populations and are associated with adverse health outcomes, including perinatal health risks and child health. One mechanism of influence may be the impact of PFAS exposure on placental structure and function.

OBJECTIVES

The objective of this study is to investigate the relationship between maternal prenatal exposure to PFAS and measures of placental vascularization, and to assess whether changes in vascularization play a role in mediating the impact of PFAS on birth outcomes.

METHODS

Using data from a prospective cohort study, we examined associations between second trimester PFAS (individually and as mixtures using Bayesian kernel machine regression) and placental arterial vasculature in term placentae (N = 158); secondarily we evaluated the degree to which alterations in placental arterial vasculature explained associations between PFAS exposure and birth outcomes. Placental arterial vasculature features were collected from arterial tracings of each placental image.

RESULTS

In both linear regression and mixture models, natural log-transformed perfluorooctanoic acid concentrations were negatively associated with surface vasculature, indexed by the mean distance from arterial end point to perimeter (β = -0.23, 95% CI: -0.41, -0.041); additionally, maximum arterial tortuosity was negatively associated with placental weight (β = -0.19, 95% CI: -0.34, -0.051). There were no reliable differences in effect by fetal sex.

DISCUSSION

The findings provide some of the first evidence of PFAS exposure shaping a key measure of placental vascular function, which may underlie the impact of PFAS on perinatal and child health risks.

Cell dynamics in human villous trophoblast

BACKGROUND

Villous cytotrophoblast (vCTB) is a precursor cell population that supports the development of syncytiotrophoblast (vSTB), the high surface area barrier epithelium of the placental villus, and the primary interface between maternal and fetal tissue. In light of increasing evidence that the placenta can adapt to changing maternal environments or, under stress, can trigger maternal disease, we consider what properties of these cells empower them to exert a controlling influence on pregnancy progression and outcome.

OBJECTIVE AND RATIONALE

How are cytotrophoblast proliferation and differentiation regulated in the human placental villus to allow for the increasing demands of the fetal and environmental challenges and stresses that may arise during pregnancy?

SEARCH METHODS

PubMed was interrogated using relevant keywords and word roots combining trophoblast, villus/villous, syncytio/syncytium, placenta, stem, transcription factor (and the individual genes), signalling, apoptosis, autophagy (and the respective genes) from 1960 to the present. Since removal of trophoblast from its tissue environment is known to fundamentally change cell growth and differentiation kinetics, research that relied exclusively on cell culture has not been the main focus of this review, though it is mentioned where appropriate. Work on non-human placenta is not systematically covered, though mention is made where relevant hypotheses have emerged.

OUTCOMES

The synthesis of data from the literature has led to a new hypothesis for vCTB dynamics. We propose that a reversible transition can occur from a reserve population in G0 to a mitotically active state. Cells from the in-cycle population can then differentiate irreversibly to intermediate cells that leave the cycle and turn on genes that confer the capacity to fuse with the overlying vSTB as well as other functions associated with syncytial barrier and transport function. We speculate that alterations in the rate of entry to the cell cycle, or return of cells in the mitotic fraction to G0, can occur in response to environmental challenge. We also review evidence on the life cycle of trophoblast from the time that fusion occurs, and point to gaps in knowledge of how large quantities of fetal DNA arrive in maternal circulation. We critique historical methodology and make a case for research to re-address questions about trophoblast lifecycle and dynamics in normal pregnancy and the common diseases of pre-eclampsia and fetal growth restriction, where altered trophoblast kinetics have long been postulated.

WIDER IMPLICATIONS

The hypothesis requires experimental testing, moving research away from currently accepted methodology towards a new standard that includes representative cell and tissue sampling, assessment of cell cycle and differentiation parameters, and robust classification of cell subpopulations in villous trophoblast, with due attention to gestational age, maternal and fetal phenotype, disease and outcome.

Structure-function relationships in the feto-placental circulation from in silico interpretation of micro-CT vascular structures

A well-functioning placenta is critical for healthy fetal development, as the placenta brings fetal blood in close contact with nutrient rich maternal blood, enabling exchange of nutrients and waste between mother and fetus. The feto-placental circulation forms a complex branching structure, providing blood to fetal capillaries, which must receive sufficient blood flow to ensure effective exchange, but at a low enough pressure to prevent damage to placental circulatory structures. The branching structure of the feto-placental circulation is known to be altered in complications such as fetal growth restriction, and the presence of regions of vascular dysfunction (such as hypovascularity or thrombosis) are proposed to elevate risk of placental pathology. Here we present a methodology to combine micro-computed tomography and computational model-based analysis of the branching structure of the feto-placental circulation in ex vivo placentae from normal term pregnancies. We analyse how vascular structure relates to function in this key organ of pregnancy; demonstrating that there is a 'resilience' to placental vascular structure-function relationships. We find that placentae with variable chorionic vascular structures, both with and without a Hyrtl's anastomosis between the umbilical arteries, and those with multiple regions of poorly vascularised tissue are able to function with a normal vascular resistance. Our models also predict that by progressively introducing local heterogeneity in placental vascular structure, large increases in feto-placental vascular resistances are induced. This suggests that localised heterogeneities in placental structure could potentially provide an indicator of increased risk of placental dysfunction.