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3D Biomaterials for a Blood Brain Barrier Vasculature Model
Secondary Supervisor(s): Dr Samuel Wilson-Whitford, Professor Roslyn Bill
University of Registration: Aston University
BBSRC Research Themes:
Project Outline
The blood brain barrier (BBB) is a complex structure providing nutrient exchange throughout the central nervous system (CNS); this is vital for maintenance of homeostasis and functionality. Changes to the BBB are present in a variety of devastating neurological disorders, such as traumatic brain injury (TBI) and Alzheimer’s disease (AD). Modelling these changes is necessary to understand disease progression, and how it can be predicted, reversed or prevented. The biological community is currently moving towards using 3D in vitro models that are built using human cells, as animal models do not fully recapitulate human processes. 3D models are more physiological than standard 2D cultures, allowing cells to be in a more natural conformation with physical cues from all angles.
Current models of the BBB tend to be ex vivo animal models or not fully 3D when in vitro, limiting the relevance to the human 3D in vivo environment (Wei et al., 2024). Here we will produce a fully 3D human in vitro model utilising micro-hollow fibre biomaterial scaffolds. These structures will provide the support the cells need, whilst also allowing for the functional diffusion required, due to their porous structure. These will be modifiable in order to enhance cell attachment, maturation and function through chemical modification, and can also be optimised to be biodegradable to have a material free system once the cell structures have been formed. This will remove barriers between cells, allowing for better cell connectivity and therefore function. This will be a challenge, requiring optimisation of the chemical composition of the fibre to form a stable model before removal.
The project will use micro-hollow fibres with human endothelial cells, pericytes and astrocytes to produce a BBB model that can be used to interrogate BBB functionality before and after damage and disease. This model is unique due to the inclusion the relevant human cell types, along with appropriate flow. The mechanical forces on the cells will alter their maturation and functionality, mimicking the in vivo mechanical environment.
To begin, human cell lines will be used to optimise cellular organisation of the model. This may then progress to the use of human induced pluripotent stem cell (hiPSC) derived cells. Here, the student will differentiate hiPSCs toward relevant cell types, namely endothelial cells, pericytes and astrocytes.
The successful candidate will optimise a novel micro-hollow fibre, making changes to the material, diameter, porosity, degradability and flow rate. These parameters will be tuned to closely mimic the physiology and pathophysiology of the CNS vasculature. The student will validate the model by assaying cell functionality with and without flow. BBB permeability will be measured using a fluorescent probe such as fluorescein isothiocyanate-labelled dextran. Tight-junction formation will be measured by immunocytochemistry to determine the relative expression of endothelial cell tight junctions (Claudin-5) and astrocyte end feet (AQP-4), compared with current model systems.
Introduction of fibre degradability, via materials selection, will allow for the development of unsupported models. Further optimisation will be done with the Quantum x Bio 3D bioprinter once sufficient optimisation has been performed with the current methods. Metabolic and functional assessments will be undertaken to determine what is able to pass through the barrier, and how the cells are functioning when compared with a planar culture and the current BBB in vitro models.
Throughout this project, the student will be working at the cutting edge of the field of 3D models of the BBB, using state of the art equipment and advancing their own knowledge and that of the scientific community. This will give them the tools and skill to go beyond this PhD into academia, industry and many other opportunities.
References
Wei Wei, Fernando Cardes, Andreas Hierlemann, Mario M. Modena, Advanced Science, 2024.
