How to effectively adopt and leverage Organ-on-a-chip

Dr Audrey Dubourg, product manager, and Ayisha I. A. Malik, content marketing manager CN Bio, discuss how to effectively adopt and leverage Organ-on-a-chip to drive more effective drug development.

The pharmaceutical industry has experienced tremendous growth over the last century, through innovation, technological advancements and globalisation. So, it is surprising that late-stage drug development failures remain high, at approximately 90%. With the advent of advanced drug modalities and more personalised approaches to medicine, innovative New Advanced Methodologies (NAMs), such as Organ-on-a-chip (OOC), are essential for improving drug development efficiency and outcomes.  

OOC platforms, also known as microphysiological systems (MPS), condense all the technologies needed to build functional tissues that model organ-level responses into a miniaturised format. These lab-grown mimics are perfused by media which delivers nutrients and replicates blood flow. This simulates the biological environment of human organs, providing a more accurate model for studying human physiology, disease, and response to drugs. They can be linked together to simulate processes such as drug absorption and metabolism, or to understand interactions between organs which drive disease and cause unexpected toxicities. 

OOC technology bridges the gap between traditional 2D in vitro cell culture, in vivo animal models, and the human to better inform drug development. Their use avoids scenarios where traditional preclinical methods leave you with unanswered questions or data discrepancies. By helping to justify the progression of only the most promising candidates into in vivo testing, they support the more ethical use of animal models and 4Rs objectives. Plus, they offer a viable path forward for the development of newer drug modalities where animal use is less suited. So, ask yourself, could your workflows benefit from OOC? 

Choosing the right OOC solution 

To embark on your OOC journey, here are seven key considerations to ensure you adopt the right system and assay(s) for your needs.  

1. Determining the best OOC model for preclinical testing needs 

OOC models provide insight into how drugs interact with human organs. Therefore, it is important to identify the physiological aspects that you need to replicate and check that these are achievable. The best model doesn’t need to be complex. In fact, it is best to avoid using an overcomplicated one unnecessarily as this will increase your cost. Your choice really depends on your context of use and needs.  

For instance, for drug metabolism studies, using a simple Primary Human Hepatocyte (PHH) Liver-on-a-chip model enables you to identify rare or human-specific metabolites and predict in vivo clearance, without the unnecessary complication of additional cell types. When investigating Drug-induced liver injury (DILI), a co-culture with Kupffer cells (KC) enables you to go beyond what’s possible using traditional in vitro approaches by offering greater sensitivity, plus the ability to flag immune activation. In 2020, these relatively simple assays were recognised by the US FDA, as delivering superior performance over traditional approaches (Rubiano et. al., 2020). 

More sophisticated models are required to recapitulate complex disease phenotypes such as metabolic-associated steatohepatitis (MASH). A tri-culture of PHH, KC, and stellate cells is the best bet here to enable the quantification of inflammation, steatosis and fibrosis. The ability of this assay to overcome the inter-species limitations of murine models has led to its use in supported a successful regulatory filing. 

Going beyond single-organ models, interconnected multi-organ systems also provide a complementary alternative to address the limitations of animals. For example, animals are notoriously poor predictors of human oral bioavailability (Musther et al., 2014), however, using a Gut/Liver-on-a-chip, it is now possible to uniquely simulate the process of human first pass metabolism in vitro.  

2. What are your da

ta output requirements? 

Next it is crucial to identify the most important endpoints, and the level of mechanistic detail required. A general rule of thumb is to opt for larger volumes of recoverable tissue and media if detailed studies are necessary for profiling drug action.  

Feasible endpoints include biomarker analysis, cell health, functional assays, ~omics etc. But, to translate in vitro OOC insights into human outcomes, the ability to detect clinically relevant markers is critical. For example, in a DILI assay, detecting biomarkers such as ALT, AST, and albumin (to assess liver function and damage) enables more accurate real-world scenario predictions. 

If you need to recover OOC tissue for ~omics studies, ensure the system allows easy access and that the microtissue is large enough. If you require high volumes of media for secreted biomarker analysis or metabolite identification, make sure that a given solution provides a) sufficient media b) easy sampling during an experiment and c) relevant cell: volume ratio. If imaging over time is necessary, choose a chip-based solution that is transparent but also be mindful of the caveats of using optically suited PDMS-based solutions. 

3. Off-the-shelf options or pre-validated models? 

The next question to ask is can your requirements be served by an off-the-shelf kit-based approach? OOC kits provide a faster route to adoption by eliminating the need for model/ assay development and validation. They provide a robust starting point for your journey, even without prior OOC experience, to deliver reproducible and reliable results. 

As most OOC models utilise primary cells, one of their key benefits is eliminating the need for prior cell validation work. Unvalidated cells cause experiments to fail. In our experience, 60% of donors do not adequately form 3D tissue, and it is time, labour and cost intensive to find ones that do. By utilising kits, the hard work of finding suitable donors and validating their use in assays has been done for you. Furthermore, primary cells have limited availability, once a batch runs out, the validation process begins again. Optimising media for OOC culture is also critical and increase resources spent on developing models. Using off-the-shelf kits, offering qualified primary cells and optimised media, can further fast-track successful adoption into workflows.  

When Kit-based options are not available, collaborating with suppliers offering pre-validated models and supporting protocols, saves time and resources. Many suppliers and experts publish studies that highlight successful implementations. Should you need to create your own assays, reviewing case studies and best practices from those who have successfully developed or adapted models provides valuable inspiration. 

4. Effective experimental design 

Like any other scientific experiment, a well-thought-out design is the foundation for successful OOC assays. Ensure that your experiments incorporate controls and replicates to ensure the reliability and reproducibility of your results. Consider a multi-chip plate-based approach, which provides the best of both worlds: the ability to derive deeper mechanistic insights (from large scale media and tissue), plus the throughput (up to 72 samples/run) to incorporate good experimental practise. 

5. Drug binding concerns 

The OOC chip/plate materials can impact the accuracy of your OOC data. For instance, if you are conducting an ADME-Tox study, non-specific binding to the plastic is not ideal. Many OOC utilise polydimethylsiloxane (PDMS), which enables in situ imaging, however, the crucial disadvantage of PDMS is its lipophilicity. PDMS can bind up to 70% of a drug, making it difficult to accurately quantify drug exposure-responses, or pharmacokinetics. While measures can be applied to normalise data, materials with lower binding properties, such as cyclic olefin copolymer (COC), are available. 

6. Fluidic flow 

Fluidic flow is a crucial component of OOC systems as it promotes enhanced culture function, viability and longevity over several weeks, plus it enables models to be interconnected. OOC systems achieve fluidic flow in different ways. High throughput gravity-driven systems benefit from a simple design but do not capture the single directional flow of blood. Single-path systems offer enhanced physiological-relevance over rockers but can dilute secreted biomarker concentrations and do not allow for circulating immune cells. Alternatively loop-based systems provide the truest replication of blood flow without diluting analytes but require additional media changes before drug dosing. Some even tailor the type of flow (strong and pulsatile, or slow and steady) to match organ type. Choosing the flow that suits your experimental needs, the organ you are recreating, and your experimental timeframe is necessary to ensure that you get the most from OOC experiments. 

7. Setting up your lab and team  

If you already have a cell culture setup, integrating OOC technology is straight forward. Ideally, choose a system where the majority of the “working parts” are housed outside of the incubator to ensure reliability.  

Developing your in-house OOC expertise is also easy, especially when utilising kits to get started.  Finally, it is also important to remember that you are not on your own in this journey. Suppliers provide training and technical assistance to help your team to become proficient and to troubleshoot challenges that may arise, so if you are new to OOC, leverage the experience of experts to fast-track your route to success.  

Conclusion 

Laboratories worldwide have adopted OOC to get more detailed data earlier and be more prepared for the clinic – so why delay? With multiple OOC suppliers offering a range of models, assays and capabilities, you should be able to find the right solution to meet your need, and rapidly on board to improve the efficiency of your drug development workflow.