Reducing number of mice required for drug testing via development of first in vitro automated screening platform of injured mammalian brain

Following CNS damage, regeneration of myelin (remyelination) reinstates nerve fiber integrity and function. However, remyelination often fails in prevalent neurodegenerative disorders, contributing to nerve dysfunction/ loss and clinical decline for which there is an unmet need for effective therapies. The status quo of in vivo testing for pro-regenerative drug candidates requires a large number of mice, as this necessitates sacrifice at every time point of interest due to difficulties with live-imaging deep brain white matter. In vivo testing is also incompatible with i) dose-responses, which in turn increases risk of failure (and waste of animals) from choice of an inefficient concentration, and ii) large scale approved drug screening, the most rapid and safest route to clinical trials. Indeed, recent screens aimed at identifying pro-remyelination drugs have been performed in developmental models without injury, by testing for effects on differentiation of isolated progenitors into myelin-producing cells (a process which can however be uncoupled from production of myelin) or myelin production in developing larval zebrafish; These models do not mimic the physiological microenvironment of the damaged CNS, precluding testing of regenerative capacity of drugs. In addition, the injured zebrafish remyelinates too quickly to be used for pro-regenerative drug testing. The drugs identified from the aforementioned screens are being evaluated in clinical trials for multiple sclerosis (MS), however it is unclear whether they will be broadly effective. Thus there is a demand for an in vitro drug screening system that assesses CNS remyelination directly, to identify a drug with proven pro-repair properties that could be repurposed for neurodegenerative diseases. Here, we describe a novel in vitro platform for remyelination assessment which we will use to identify regenerative drugs, while reducing the number of mice required for a comparable in vivo screen.

We propose to combine an established brain explant model of myelin injury with a novel set-up that allows automated confocal live-imaging and analysis, which together reduces the number of mice needed for a comparable drug screen by 28 fold. The objective is to perform the first unbiased drug screen in injured mammalian brain specifically for pro-remyelination capacity, achieved by i) setting up transgenic reporter and quantification systems that support automated assessment of remyelination, ii) validating the most effective scaffold platform for brain explant screening by live-imaging, and iii) applying a proof-of-concept approved drug library screen for remyelination enhancement.

This would be the first drug-screening platform of injured mammalian brain, allowing for rapid and unbiased identification of regenerative drugs for neurodegenerative disease. We anticipate that this setup could be repurposed for screening of i) other processes in brain explants (e.g. synaptic pruning, inflammation), ii) other types of libraries (e.g. chemical, CRISPR, siRNA), and iii) protection/repair in tissue explants from other organs (e.g. liver, pancreas, lung), thereby reducing the number of rodents needed for drug screening in a wide array of studies.