Interview: Advancing neuroscience drug discovery through the generation of predictable human CNS models

Diseases of the central nervous system (CNS) impact many people with varying severity and are associated with a diverse range of conditions, including neurodegenerative diseases. Yet this area continues to have the highest unmet needs in terms of intervention. Tackling this issue requires a coordinated effort to identify targets, screen for drug candidates, and test the leads in clinically-relevant models that are predictive.

Medicines Discovery Catapult (MDC) is addressing a key need in neuroscience drug discovery by developing in vitro CNS cell models, which include human iPSC-derived neurons, astrocytes, and microglia. In this exclusive interview, Simon Bennett, Regional Business Manager at Sartorius spoke with Dr Emma Jones, Lead Scientist, In Vitro Neurobiology, and Dr Eve Corrie, Scientist, In Vitro Neurobiology at Medicines Discovery Catapult about their neuronal cell models and ongoing pharma collaborations. We also discussed how technologies like the Incucyte^® Live-Cell Analysis System enable them to study the effects of drugs on CNS cell behavior.
 

Question: We really enjoyed the video you recently posted and would like to learn more about your work. Can you start by describing the goal of your organization? 

Emma Jones

MDC is an independent, not-for-profit, national innovation centre reshaping drug discovery for patient benefit by transforming great UK science into better treatments through partnership. MDC supports drug discovery innovators by making world-class expertise, facilities, complex technologies and advanced analytics accessible – accelerating business growth and improving patient outcomes.

Our aim is to improve drug discovery across the whole spectrum of diseases, and one of our focus areas is neuroscience.

Emma Jones

In thinking about the end goal, our first challenge is creating neuronal models that are physiologically relevant and predictive. So, we’re thinking about what type of neurons we have; are they glutamatergic or inhibitory neurons? Or what culture properties do we need to model different CNS diseases? So that could be done either by using cells that have disease-causing mutations, Or by stimulating the cells with different kinds of stress or disease-causing stimuli.

Next, are the technical issues of working with neurons, which are quite challenging. To get healthy, reproducible cultures in vitro that are at the right maturity we need to optimize the growth conditions. So, we think about the type of media and try monocultures or co-cultures with different cell types, such as astrocytes, whilst also thinking about their attachment to the dish. It can be quite challenging technical work, particularly when working with human models like iPSC-derived neurons, which are different from an immortalized cell line. Differentiated neurons don't divide, so their quantity is limited, making them very expensive to work with.

Eve Corrie

Lifespan is a big issue with neurons because they're post-mitotic and no longer proliferating. Also, they're more limited in number than other cell types, so if they're just on their own in monoculture, you generally only get a handful of weeks out of them before they start getting unhealthy. That is why we try and co-culture with astrocytes because that also increases their survival and maturity. 
 

Emma Jones

We're interested in how cultures mature over time. What's nice about Incucyte is that we can take continuous measurements over time, where the cells are maintained in the proper CO2 and temperature conditions. It really allows us to track electrical activity and look at different time points. So, for example, we can add drugs and look and see how they affect activity or observe activity as the circuitry matures. 

Eve Corrie

Without the Incucyte, we would rely solely on endpoint experiments to do our neuronal activity and neurite outgrowth studies. We'd have to do many time-point experiments, which massively increases the hands-on time and the number of cells you need because it's a separate experiment each time. So, it's really nice to follow the same cells over time with the Incucyte.

Emma Jones

The other advantage of Incucyte is the different fluorescence channels. It gives us the option to simultaneously look at the viability and the effects of drugs or disease phenotypes. We can also look at transfection or viral transduction and use different kinds of reporters. So, if a biotech comes to us with their drug, we can use the Incucyte to track both neuronal growth and neurotoxicity over time.
 

Emma Jones

We do many collaborations with small biotech companies that want to know if their drug can modulate neurite outgrowth, while simultaneously monitoring neuron viability.

For these types of experiments, we plate iPSC-derived neurons with a concentration range of the therapeutic and then monitor the outgrowth of neurons. We can measure outgrowth from the branching dynamics and monitor possible toxic effects of the drugs at the same time.

In another example, a biotech was interested in whether their therapeutic could affect neuronal activity in some way. We used iPSC-derived glutamatergic neurons, co-cultured with rat astrocytes. We cultured these neurons for several weeks in vitro and tracked the increase in activity over time. At around three weeks, while the neurons and the network activity were maturing, we applied the therapeutic to see if there was any change. Even if the target of the therapeutic is not an ion channel or something that would be expected to affect activity, it is useful to investigate neuronal activity as a safety aspect for drug development.

Emma Jones

We want to help companies validate their targets more efficiently and with more information. To do that, our goal is to have the best CNS models that are robust, reproducible, and predictive. 

In terms of neural activity, we will continue to build on the models we have by using different types of iPSC-neurons or culture systems, such as incorporating inhibitory neurons with the iPSC-derived glutamatergic neurons or using neurons with disease-causing mutations. We are also working with tri-cultures of human iPSC-derived neurons, astrocytes and microglia, and plan to look at the activity of those cultures. 

The neuronal activity assay and outgrowth assays are just two of the assays we have, but we are looking at many other readouts to assess cell profile and behavior in our CNS models. For example, what are the cells producing? What biomarkers? What cytokines and growth factors? We’re also doing advanced imaging to look at morphological changes and other aspects of cell function. We can carry out bulk/single-cell RNA-seq or proteomics to look at how the molecular profile of the cells change in response to a particular therapeutic. 

This information can help companies better plan and design clinical trial studies. For example, it might help them to better understand the action of their therapeutic or identify biomarkers that translate to human patients.

Emma Jones

That is the other good point about reducing the number of animals you might need. For example, you can identify pathways that might be changed in the cells before you get to a clinical trial. These data are helpful when you think about dosage and safety while planning studies in animals or in patients. Given the tremendous cost and high failure rates of drug development, having highly predictive models is what every drug company hopes for.