In vitro models of the BBB and applications in pharmacological and toxicological screenings
© Manu Friederich / Universität Bern

ESR 1 vision / project

Marjolein Heymans - Universite D’artois

ESR 1: March 18, 2019; PhD Health Sciences

In vitro models of the BBB and applications in pharmacological and toxicological screenings

Project Results

In the framework of BtRAIN, ESR1, reviewed the traditional use of in vitro BBB models, thereby focusing on one of the most extensively used BBB-related parameters, i.e. BBB permeability. BBB permeability is considerably influenced by different factors that are often neglected when performing interstudy comparisons. The influence of one of these factors, namely brain tissue binding, has been evaluated by incorporation into the traditional in vitro method to assess BBB permeability. A total of 27 marketed CNS compounds were therefore screened using this new method of BBB permeability assessment (Pvitro). Our results reinforce the known influence of brain tissue binding on BBB permeability of compounds that are characterized by a low unbound brain fraction (i.e. high tendency to bind lipophilic entities) and show a considerable better prediction of in vivo brain permeability (Pvivo) using the optimized method (Pvitro) compared to the traditional method (Pe).

In a second part, ESR1 focuses on how to improve our understanding of the functioning of the BBB and of the mechanisms and regulation behind this functioning. This is crucial to further improve development of BBB in vitro models. BBB functioning depends largely on the communication between the BBB endothelial cells (ECs) and other cell types (e.g. brain pericytes, astrocytes, glial cells and neurons). Therefore, the contribution of brain pericytes on BBB formation and BBB maintenance in stem cell-derived brain-like ECs has been studied by a transcriptomic approach. Our results describe the transcriptomic landscape of ECs upon coculturing with brain pericytes. In addition, this data provides intelligence on how and to what purpose in vitro BBB models can be used, as proper characterization of a model is crucial for its use in pharmaceutical CNS drug discovery and CNS drug delivery programs. Finally, the potential of a human in vitro BBB model to predict brain distribution has been evaluated. The unbound brain-to-plasma concentration ratio was therefore measured for 16 marketed CNS compounds using a human in vitro BBB model and a rat in vitro BBB model and compared to in vivo human findings. These comparisons enable to investigate the predictive power of both in vitro models with respect to CNS drug distribution and allow to evaluate the existence of potential species differences between rodents and humans. Our preliminary data supports the use of the human in vitro model rather than the rat in vitro model to predict CNS drug distribution in humans, however, further experiments are necessary to generate more conclusive verdicts.

Altogether, the thesis work of ESR1 has provided intelligence on how to employ different in vitro BBB models to obtain useful information on BBB-related parameters including brain penetration and CNS distribution of drugs.

Hosting institution

UNIVERSITE D’ARTOIS, BBB Lab, Arras, France

Supervisor

Maxime Culot

Early Stage Researcher

Marjolein Heymans