Background: Immunisation during pregnancy is now recognised as an efficient approach to protect the fetus and/or the infant from life-threatening infection. However, the mechanisms underlying the transmission of pathogens and the transfer of passive immunity from the mother to the fetus remain obscure. The structure that lies at the interface between mother and fetal environment is the placenta, an intricate organ made up of cellular and vascular networks that serve the functions of kidney, lung, gut and liver altogether in order to promote fetal growth and viability. Owing to the ethical issues associated with the study of human pregnancy, a variety of in vivo, ex vivo and in vitro models have been developed. However, while the in vivo animal models fail to match the structural and/or functional properties of the human placenta, ex vivo human models are impractical, difficult to set up, of limited capability, and in vitro models lack physiological relevance by virtue of their monolayer and/or static set-up.
Proposed solution: To address the caveats inherent to current experimental models of the human placenta, we propose to develop a novel and easy-to-set-up in vitro platform that will help reduce and/or replace the use of both murine and non-murine models. Our model will be validated through the analyses of placenta-blood barrier functions and cross-placental transport of pathogens and antibodies using a 3D microfluidic bioengineered platform i.e., the Organoplate® (Mimetas).
Experimental approach: Trophoblasts represent the most outer layer of the placenta whereby nutrients, chemical and gas feto-maternal exchanges are regulated. With the support of our industrial partner, we will develop an unprecedented trophoblast-based microfluidic dynamic model, that mimics the feto-maternal interface. This will be achieved using the commercially available and imaging-friendly 3-line OrganoPlate® system (Mimetas BV), we will create a tubular culture system that mimics the three-dimensional, quasiphysiological environment where (fetal) endothelial cells will be luminally exposed to physiological levels of flow and co-cultured with abluminal trophoblasts to form a functional placental barrier. Our platform will be unique in that it will also offer real-time and high-throughput imaging capability.
The major outcomes of this project will be:
- The development of a microphysiological model that reconstitutes the functional unit of the human placenta, and establishment of SOPs disseminated via local and international networks including the OOAC (organ-on-a-chip) Technologies (MRC-Innovate UK) and iPlacenta (Horizon 2020) and/or via sponsored workshops
- The provision of in vitro platform offering versatility and high predictive value to replace animals that would otherwise be used to investigate maternal passive immunity and vertical disease transmission
- The establishment of optimal methodologies for theimaging of antibodies and pathogens to promote a wider use of dynamic in vitro imaging.
3R impact: An immediate benefit will be the potential for a significant reduction in the number of experimental animals used for research. Our novel platform could be used specifically as in vitro substitutes for infectivity studies where pathogens are injected into or ingested by the host to determine the quantity required to induce clinical symptoms; infection biology studies which are aimed primarily at improving our knowledge of basic pathogen biology, pathogenesis and host-pathogen interaction; drug testing and/or vaccine screening where drugs or vaccines are administered at a range of concentrations to determine effective dose. Although clinical drug and vaccine trials are unlikely to be avoided completely, these could be considerably refined if more relevant in vitro testing were possible.