The overarching research objective of the Wallingford Lab is to advance fundamental knowledge of placental vascular development and pathophysiology and to improve obstetric cardiovascular medicine by supporting the development of greatly needed diagnostic tools and treatment options for placental disorders. We investigate molecular mechanisms that control vascular development and pathophysiology of the least understood organ: the placenta. Normal growth and function of the placenta are essential for maternal and fetal health, both during pregnancy and later in life. Placental dysfunction can lead to preterm birth, preeclampsia (a hypertensive disorder caused by placental dysfunction), and loss of life. Mothers who have had preeclampsia are at a higher risk of cardiovascular disease and coronary artery calcification. Babies who were exposed to preeclampsia are at a higher risk for hypertension and increased BMI into their teenage years and have an increased stroke risk later in life. Currently, there are few diagnostic tools and no curative therapeutic options for preeclampsia besides immediate delivery of the placenta, often necessitating preterm delivery. The dearth of early diagnostics and treatments stems in part from a lack of understanding of how the human placenta and placental diseases develop.
Morphogenetic Analysis of Placentation (MAP)
The Wallingford Lab MAP project investigates developmental mechanisms that control subsequent placental blood vessel formation, vascular remodeling, and vascular mimicry during placentation. Dynamic vascular remodeling of the mouse placenta is well exemplified by examination of trophoblast, vascular and structural markers (Figure 1). Building on Dr. Wallingford’s previous peri-implantation development work (Wallingford et al 2013), the MAP group applies vascular morphometric and cellular phenotyping to developmental models and tractable 3D culture systems in order to determine how blood vessel formation, vascular remodeling, and vascular mimicry are controlled at the molecular level.
Figure 1. Vascular Remodeling in Mouse Placentation. A. Implanting mouse embryo at E4.0. Laminin (LMN) highlights vascular structures in the decidua and E-Cadherin (CDH1) highlights the breakdown of uterine luminal epithelium. B-C. E9.5 Mouse placenta labelled with antibodies against Slc20a2, trophoblast cytokeratin 7 (CK7), LMN and endothelial von Willebrand’s Factor (vWF) localization. E-H. E15.5 placenta with PiT-2, CK7, LMN, vWF, and pericyte (CD13) localization.
The placenta is the least understood human organ partly because access to the developing tissue is limited and there are marked differences in comparative anatomy between eutherian species. A recent publication from the NIH reported that pregnant women and their babies are frequently viewed as a vulnerable patient population, and as a result they have been relatively underserved and functionally neglected in biomedical research – constituting a deprived population in need of more effective therapeutic interventions. New approaches are greatly needed to advance clinical care options.
One way in which our lab is directly addressing this need is by pioneering the development of 3D culture systems that model placental vascular development. We aim to combine embryology and bioengineering techniques to generate tractable tools that better recapitulate the physiology of in vivo systems. We are developing a 3D cell culture approach to investigate how vascular tissue and specialized niches in the placenta develop and function in order to more accurately and reliably model physiological placental vascular development and generate novel data they may be used to improve biomedical understanding of human placental development and disease, including preeclampsia (Figure 2). As we expand our systems, our lab would gladly serve as a unique resource to local investigators who wish to expand into collaborative placenta research.
Application of 3D Culture Systems to Advance Reproductive Health. Complimentary 3D cell culture vascular models will be used to examine the interaction of four developmental pathways on trophoblast vascular mimicry and patterning. Impact on vascular morphometrics and cellular phenotyping will be determined by multivariate analysis. Future applications are numerous, including analysis of genetic variant function, developmental therapeutics, and other investigations.
Maternal-Fetal Phosphate Transport (M-FPT)
Phosphate is an essential molecule that plays numerous roles in human health. It is a primary component of the mineral that our bones are made of, but it also performs many other important functions. While a large body of scientific research describes phosphate biology in the adult, very little is known about how phosphate gets to the developing baby. The Wallingford Lab M-FPT project is closing this knowledge gap by defining maternal-fetal phosphate transport routes, testing hypotheses on the basic science of phosphate transport across the placenta, and developing new biological assays for maternal-fetal phosphate homeostasis that may one day be useful for assessment and interpretation of maternal and fetal health in the clinic. Their work has identified a critical role for the placental sodium-dependent phosphate transporter Slc20a2 in fetal growth and development and protection from placental vascular calcification (Wallingford et al. 2016
and Yamada and Wallingford et al. 2018a)
LacZ expression driven by the Slc20a2 promoter highlights physiologically relevant expression domains of Slc20a2 in the mouse placenta (Figure 3). Coinciding with initiation of impaired fetal bone ossification, Slc20a2 mice develop increased levels of ectopic mineralization in Slc20a2 deleted expression domains, providing the first genetic link to placental calcification. Clinically, vascular calcification in the placenta has been observed, but the biomedical significance of placental calcification is poorly understood, and may underlie hemodynamic alterations in conditions such as preeclampsia, placental thrombosis, and intrauterine growth restriction. The biomedical significance and prognostic value of placenta calcification are discussed in a recent publication from our lab which also reports on novel microcalcification patterns in human placenta (Wallingford et al. 2018b
. Slc20a2 is expressed at the mouse maternal-fetal interface. Regional Slc20a2 expression during mouse placentation is indicated in blue. Slc20a2 expression detected by beta-galactosidase staining of Slc20a2-driven LacZ was observed in the ectoplacental cone, chorion, allantois, parietal endoderm, fetal endothelial cells, trophoblasts, and pericytes.
In future work the M-FPT project will evaluate actions of Slc20a2 at the molecular level during placentation and embryonic development. This project is supported by NIH/NICHD R00HD090198 (PI: Wallingford, MC) Determination of maternal-fetal phosphate transport mechanisms and the role of sodium-dependent phosphate transporters in extraembryonic tissues and has previously received support from NIH/NHLBI T32HL007828 (PI: Dichek, D) Phosphate Transporters and Cardiovascular Development and Disease in the Mouse.
Placental Vascular Structure-Function Relationships (PVS-FR)
The PVS-FR project is a suite of beta testing initiatives coordinated by Dr. Wallingford. PVS-FR initiatives and collaborators include:
- New Approaches to Placental Ultrasound Interpretation
- Manjiri Dighe, Department of Radiology, University of Washington. Ezgi Mercan, Seattle Children’s Research Institute
- Evaluation of Triad Ovine Physiology (Maternal, Placentome, Fetal). Martin Frasch, Department of Obstetrics, University of Washington.
- Quantitative Placenta Phenotyping Assessment. Murat Maga, Center for Developmental Biology and Regenerative Medicine, Seattle Children’s Research Institute.
- Development of Noninvasive Imaging Techniques. Howard Chen, Molecular Cardiology Research Institute (MCRI), Tufts Medical Center.
Previous Lab Members
Simon Shulman: Simon Shuman is an undergraduate at the University of Massachusetts Amherst where he is pursuing a BS in Biology as a member of the Commonwealth Honors College. Mr. Shulman worked in the Wallingford Lab in the Mother Infant Research Institute (MIRI) during the summer of 2018 as a Tufts Medical Center Volunteer. Mr. Shulman’s primary interest was to develop the research skills needed to link cell biological processes to protein function and gene expression. While in the lab Mr. Shulman developed skills in conducting scientific literature reviews, developmental phenotyping, immunofluorescence, and laboratory teaching, and he became a member of the American Society of Nephrology. Mr. Shulman has also gained valuable leadership experience coaching volleyball at the SMASH Volleyball camp. As his research training continues, Mr. Shulman plans to work towards a career in biomedical research and/or medical practice.