Introduction

Non-alcoholic steatohepatitis (NASH) is a liver disorder marked by inflammation, fat deposition and fibrosis that leads to cirrhosis and liver cancer. NASH is a massive disease worldwide with millions of people affected, and no cure. Older research models (animal models, 2D cell cultures, etc) cannot encapsulate the intricate liver microenvironment. 3D bioprinting technology has reshape biomedical science and provides a way to build realistic tissue models. In this post we will describe how 3D printed NASH micromodels are helping to advance NASH research by showing how they were created, used and how they could be the future of drug discovery and therapy.

Figure 1. Steatosis-like phenotype and lipid accumulation in NASH-treated hLiMTs. (Ströbel S, et al.; 2021)

Creation of 3D Printing NASH Micromodels

1. Principles of 3D Bioprinting

Layer by layer bioinks (composed of cells, growth factors and biomaterials) are laid down for tissue structures in 3D bioprinting. This technology is spatially controlled to accurately place cells in precise locations, mimicking the complex organisation of natural tissues. Bioprinting can generate liver tissue models with several cell types and ECM elements – which are more physiologically active than standard models – for NASH research.

2. Bioink Composition

To build bioinks that can work with NASH micromodels is to choose the right cells, biomaterials, and biochemical signals. It is liver cells, stellate cells, Kupffer cells and endothelial cells that are required for replicating liver function and pathology. Unlike the ECM, biomaterials such as collagen, gelatin and alginate anchor and mimic the structure. It is also possible to use growth factors and cytokines in bioinks to stimulate cell differentiation and recreate the inflammatory environment of NASH.

3. Printing Process

To make 3D bioprints of NASH micromodels, the designer starts by building a digital model of the structure of liver tissue. It is this pattern that's translated into print instructions, telling the bioinks how to deposit themselves to achieve the shape. The creations grow in bioreactors, after they're printed, and regain tissue specific functions and a structure. Printing parameters like nozzle size, pressure and temperature should be optimized to maintain cell integrity and fidelity of the construction.

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Application of 3D Printing NASH Micromodels

1. Disease Modeling

3D printed NASH micromodels model the microenvironment of NASH, allowing analysis of the disease mechanism. Scientists can understand the relationship between different cell types, how metabolic perturbations cause inflammation and fibrosis, and how NASH becomes more complex by genes and environment. Such models give you data you cannot find in animal models or 2D cultures, and can show us what pathology in human liver is really like.

2. Drug Discovery and Testing

And that the NASH hasn't received effective treatment – better drug discovery platforms will come in handy. NASH micromodels 3D printed to serve as cutting edge test-beds for treatments. They allow screening drug candidates with high throughput for impact on liver cells, ECM and disease markers. These models can also measure drug toxicity and pharmacokinetics, predicting clinical effects better and without having to use animals.

3. Personalized Medicine

Personalised medicine will try to prescribe the best possible treatments to patients based on genetic and phenotypic profile. NASH micromodels printed on 3D printers can be enriched with patient cells for an individualised disease model. These models can test individual drugs and treatments, and reveal what works best for particular patients. This technique could help with better treatment efficiency and less side effects.

4. Mechanistic Studies

It's imperative that we understand the intricate processes that drive NASH so that we can target treatments. These 3D-printed micromodels can be used by scientists to study different cellular and molecular pathways in NASH. Scientists can for example turn certain genes or signalling pathways in the micromodels on or off to investigate their effects on the course of the disease. That kind of control and accuracy makes it possible to pinpoint new therapeutic targets and biomarkers.

Benefits of 3D Printed NASH Micromodels

1. Physiological Relevance

NASH micromodels 3D printed are more accurately modeled, in the microenvironment and structure of the native liver tissue and offer more physiologically relevant information than conventional models. Because the cell types and ECM elements are all included, cell-cell and cell-matrix interactions can be mimicked, which is important for NASH pathology research.

2. High Throughput and Scalability

Bioprinting allows one to produce many micromodels at once for the high-throughput screening of drug candidates. This scalability is needed for large-scale research and makes drug discovery faster.

3. Reduction in Animal Testing

As an accurate and more sustainable substitute for animal models, 3D printed NASH micromodels aid in reducing animal testing. These models can mimic the human dimensions of NASH, making research findings more readable in the clinic.

4. Customizability

Micromodels can be created in 3D bioprinting to study a wide range of aspects of NASH. Researchers can adjust the model's chemistry, architecture and cellular layout to study different stages of disease, genetic backgrounds and environmental conditions.

Challenges and Future Directions

1. Technical Challenges

Although promising, 3D printed NASH micromodels lack technical infrastructure: standardised protocols, better bioinks, and more powerful bioreactors for tissue growth are required. It is important that the models are reproducible and scalable, otherwise they will not be widespread in research and industry.

2. Integration with Other Technologies

The future of NASH research is the combination of 3D bioprinting with other advanced technologies including microfluidics, organ-on-a-chip, and new forms of imaging. Both of these methods can be used in tandem to make NASH micromodels more functional and analytic, giving greater insights into disease processes and treatment response.

3. Regulatory Considerations

With 3D printed NASH micromodels closer to clinical trials, regulations need to keep up with new technologies. We need to create rules of thumb for the validation and standardization of bioprinted models before they can be accepted for drug development and personalized medicine.

Conclusion

NASH micromodels printed 3D are an exciting development in liver disease research. Providing a physiologically appropriate environment for studying NASH pathology, such models present new potential for drug discovery, individualised medicine and mechanistic investigation. Technical and regulatory hurdles still exist, but 3D bioprinting technologies are being developed and integrated, with the greatest potential to transform NASH research and patient care. In the future, 3D printed micromodels could be an indispensable part of the battle to discover and overcome NASH.

Reference

1. Ströbel S, et al.; A 3D primary human cell-based in vitro model of non-alcoholic steatohepatitis for efficacy testing of clinical drug candidates. Sci Rep. 2021, 11(1):22765.