Once seen as a thing of the future, organ-on-a-chip (OoC) systems and CRISPR gene editing have now matured into tools that are being widely used and developed across the world. Each brings new opportunities to biomedical research, with OoC providing more relevant physiological testing conditions and CRISPR making gene editing an accessible procedure. Now, however, it is their convergence that has the potential to reshape the landscape of disease modelling.
When used together, these systems make it possible to recapitulate patient-specific physiology and model multi-organ interactions in real time. As such, CRISPR-on-a-chip technology can provide the answer to the limitations posed by traditional animal models and static cultures.
Why CRISPR and OoC fit together
CRISPR and OoC are two very trendy topics within the field of drug development right now. It’s practically impossible to attend a conference without stumbling across talks on either one. As with all new and popular things, these two research areas attract a lot of scrutiny.
OoC is a name used to describe research in which cells and organoids are grown in an environment that is more physiologically relevant than static 2D culture. Here, microfluidic devices containing miniaturized, 3D tissues that mimic organs are used in combination with fluid flow systems. Fluid flow can be created in a variety of ways, ranging from simple devices that make use of gravity to more complex versions that use external syringe pumps or pressure controllers. This makes it possible to mimic the internal fluid flow and sheer stresses that our cells and tissues experience. Afterall, cells might appear happy to grow on hard tissue culture plastic whilst completely static, but is their behaviour in these conditions actually meaningful when our bodies are complex, dynamic systems?
CRISPR, on the other hand, is a genome editing tool that makes it possible to introduce specific mutations into cells, amongst other things. Though its applications are broad (and the technology is still in its infancy) we’re now seeing a host of papers being published in which drugs are being tested on CRISPR-modified cells that have been genetically modified to contain mutations that the drugs are intended to address. Naturally, this is leading to rapid experimentation with more relevant conditions. Previously, researchers would either have to wait to obtain needed patient cells or test drugs on healthy cells, which likely would overlook many things and not provide the detailed insight needed.
Both CRISPR and OoC bridge the gap between in vitro and in vivo modelling by making it possible to test drugs in a way that is closer to how the drugs would actually be used. As such, it is no surprise that they can also be used in tandem to create even better in vitro models. Imagine being able to grow highly specific modified cell cultures in dynamic, organ-like conditions; this is the reality that these two technologies can provide.
Applications in disease modeling
Consider applications in rare genetic disorders. Traditional disease models often rely on knockout or knock-in mice, where genes linked to a condition are silenced or overexpressed, respectively. While this provides useful information, and has contributed to significant advances in drug discovery, these models are known for oversimplifying complex human diseases. CRISPR-Cas9 has built upon this by providing a tool that makes precise genetic edits possible, creating highly specific animal models of rare genetic disorders. However, the use of animals remains an issue, and the fundamental differences between humans and animals frequently results in therapies that succeed in animals but go on to fail in human trials.
An example of where OoC and CRISPR could come together is in cystic fibrosis (CF) research. CF is caused by mutations in the CFTR gene, leading to thick mucus buildup and progressive organ damage. CRISPR can be used to engineer CF-specific mutations in human cells, while OoC platforms have already been used to model hallmark features such as mucus hypersecretion, inflammation, and infection. Together, these tools allow researchers to study disease mechanisms and drug responses in a human-relevant system, without relying on patient samples or animal models.
Other potential applications exist in neurodegenerative diseases, which are notoriously difficult to model because they primarily impact the brain – arguably the most complex system in the body. Modelling diseases like Alzheimer’s in 2D culture lacks much of the physiological context that is important for assessing the impact they have on tissue. OoC systems help to provide some of this context, by incorporating 3D architectures that include neurons, and exposing cells to shear stresses and flow dynamics that mimic vasculature in the brain.
CRISPR makes it possible to create the cells that go within the models. For example, CRISPR can create isogenic pairs of cell populations to compare the impact of a specific mutation.
Let’s take the PSEN1 gene for example, mutations to which are the most common cause of familial Alzheimer’s disease. With CRISPR, these mutations can either be induced in a healthy iPSC cell line, or corrected in patient-derived iPSCs. From here, the isogenic pairs of cells (a healthy versus mutated form) can be differentiated and grown in an OoC model, and several outputs such as synaptic function and protein aggregation can be directly compared. This provides us with a clear look at how these mutations alter real-time neural function over a longer period of time – and in much more detail than 2D models can provide.
The combination of CRISPR and OoC also gives us the tools to engineer disease at a patient level, and functionally test how to reverse it. In other words, personalized medicine. It is not always possible to safely remove cells from a patient to grow them in culture, and diseased cells may have other comorbidities that prevent them from growing in a suitable way.
With CRISPR, a specific set of mutations found in a person with a genetic disease can be inserted into a relevant, healthy cell line. The cells can then be grown in an OoC model, and various drugs and therapies can be tested. For example, for a patient with long QT syndrome, cardiomyocytes derived from iPSCs could be edited to carry a KCNQ1 mutation, along with any other mutations that the patient's cells exhibit. These could then be cultured on a heart-on-a-chip to screen for safe antiarrhythmic therapies that are specific to that patient, reducing much of the guessing game that’s still involved with managing long QT syndrome.
Limitations and challenges
Although there is significant promise surrounding the combination of CRISPR and OoC systems, there are still technical and regulatory hurdles preventing the tools from becoming routine in translational research.
One of the biggest challenges is being able to create multi-organ systems that combine individual OoCs to assess the systemic effects of drugs. This is a big topic of focus within microfluidics research, as drugs can often impact multiple parts of the body beyond just their intended target.
Additionally, genetic diseases often have an impact on more than one part of the body, and as such, accurate modelling of these diseases requires looking at whole systems and the interactions between them. Multi-organ chips are already in development with some success. For example, a chip containing individual chambers to represent the liver, heart, and lung have been created to analyze the inter-organ response to drug administration.
As for regulatory hurdles, both the EMA and the FDA have shown interest in OoC and CRISPR individually, but combined use cases are still in early exploratory phases. There is a lack of standardization across research regarding protocols and materials for OoC, and no formal validation pathway for these to be used as stand-alone preclinical models. This creates a catch-22: without validation, industry uptake is limited. But without widespread use, validation is difficult to justify.
The future of CRISPR-on-a-Chip
Both CRISPR and OoC are developing at a rapid pace, and at this stage their combination seems more like an inevitability rather than a possibility. Regulatory bodies are moving away from mandatory animal testing and towards more advanced methodologies to validate new treatments, which these technologies fall under.
The potential applications of CRISPR-on-a-Chip within genetic disease research are vast and span therapeutics development, companion diagnostics, and rapid-response pathogen modelling. Additionally, beyond being combined, OoC could be used as a preclinical screening platform for CRISPR-based therapies in which organ models are used to check for off-target effects and organ-specific toxicity, helping to get more CRISPR-based therapies to vulnerable patients quicker.
Ultimately, the convergence of CRISPR and OoC offers a real step towards truly personalized medicine. It’s a vision that can change how we study genetic disease and assess safety before a single dose is given.
But for all the promise, some important challenges still remain surrounding the standardization of chip fabrication and ensuring that these complex systems are robust and reproducible enough for clinical decision-making. Still, momentum is building. With every new proof-of-concept study, this once-hypothetical future moves closer to reality. The path to personalized and predictive disease modelling may not be simple, but it’s never looked more possible.
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