14TSB_NAT A novel integrated BBB-brain model for comprehensive drug permeability and toxicity testing

The blood-brain barrier (BBB) is a highly organised microvasculature system composed of different cell types including brain endothelial cells, pericytes and astrocytes. Disruption of the BBB results in various brain diseases including stroke and Alzheimer's disease. Understanding of BBB integrity and maintenance is, therefore, essential to developing measures for preventing its disruption and also for effective drug delivery to the brain. Currently, most studies on BBB integrity and damage are performed on in vivo models and the current in vitro models do not reflect the cellular interactions that occur in in vivo, as different BBB cell types are cultured and studied in different types of media. The present project aims to develop a three dimensional (3D) in vitro BBB construct within the Kirkstall Quasi-Vivo culture system, which allows multiple cell types to be cultured in inter-connected chambers. Real time tracking of solutes across the BBB will be undertaken using a novel combination of laser and electrochemical biosensor based interrogation. Once developed, this in vitro model will be more accessible than an in vivo animal model for investigation of drug transport across the BBB

The blood-brain barrier (BBB) is a diffusion resistant barrier with complex permeability properties mediated by both the cellular and associated extracellular biopolymer matrix. The former comprises an integrated complex of endothelial cells, pericytes and astrocytes. Baseline barrier properties and their changes in disease states serves as both a criterion of what is 'normal' and as a basis for quantitaive understanding of structure/function relationships. The Kirkstall Quasi-Vivo culture system secures a two compartment model for culture of BBB cell types and, specifically, allows correlation of cell populations with permeability. Importantly, the project will use continuous tracking electrochemical (as well as optical) sensors for monitoring selected organics/metabolites and will give quantitative diffusion coefficient data in Fickian terms rather than as a semi-quantitative index. The eventual integration of sensors and cultured cells will serve as a platform for future bioreactors for endothelial and other barrier tissue constructs. By selection of diffusants with different molecular properties (charge, polarity, size), it will be possible to establish different types of barrier function, and in addition its relation to structural changes in the BBB (ageing/disruption), including the relative balance of transcellular and paracellular transport. The 3D construct provided by Leeds University and the controlled flow system of Kirkstall will be key to meaningful data generation, especially since flow control will enable an assessment shear force effects at the endothelial surface, and thus its direct impact on cell properties as well the indirect effect on solute transport from the bulk solution. The integrated system will provide a basis for future analysis of transport asymmetry, hysterisis, saturation effects and competitive transport. A further aspect of the work will be the design of protein support layers as a basement membrane equivalent.

This project supports the government agenda of the 3Rs for animal welfare and will offer both DEFRA and MHRA reliable tests to implement their animal free policies. We will inform these policy developers of options for in vitro tests to lead the requirements of new medical technologies and products at international level.

The overall society will benefit from the economic gains, as well as from the medical advances to treat neurobiological diseases, including new drugs developed using animal free platforms. Society will also gain from workforce capacity building for the training of highly qualified interdisciplinary specialised professionals.

Public perception of science and technology will also be enhanced by tangible medical benefits to society, and by involving public and patient groups to provide feedback.