How organoids can redefine pre-clinical research

Slices of mini–brain organoids with neural stem cells (red) and cortical neurons (green) [Credit: Hajime Ozaki, Watanabe lab/UCI].

Organoid technologies are becoming an invaluable solution for preclinical research, with the ability to augment the development of personalised medicine, drug discovery and gene therapies.

These 3D cultured structures that are derived from healthy individuals or patients’ cells, such as human pluripotent stem cells (hPSCs)¹ or adult stem cells (ADSCs)² are changing the paradigm of scientific understanding. They have the capacity to differentiate tissue-specific cell types that mimic the architecture and complexity of human organs, from brain,³ to gut,⁴ providing a platform for preclinical testing of new drugs, high-throughput drug screening and long-term toxicity screening.

The substantial value of organoids is becoming increasingly recognised by supportive government initiatives developing novel drugs, with a growth rate of 22 percent between 2023 and 2030 and a market size predicted to reach over US $6.5 billion by 2030.

Organoid development

The development process of organoids begins with the extraction of adult stem cells or pluripotent stem cells from an organ, followed by their incubation in a specialised in vitro environment containing various growth factors (eg, EGF, FGF, NOG, RSPO1, BMP2) to support the growth, proliferation, and differentiation into specialised cells. This ultimately leads to the formation of a 3D structure that resembles the desired organ.

The incubation time varies from a couple of weeks to a few months, depending on the targeted tissue, and sizes typically range from around 100 micrometres (µm) to a few millimetres (mm) in diameter (5). Comprehensive analytical methods are then employed to evaluate the organoid’s cellular composition (e.g., transcriptomics, scRNA-seq), structure (eg, immunofluorescent staining, bright-field imaging), and functions (eg, ELISA, Luciferase assays).⁵

Organoids are recognised as New Alternative Methods (NAMs) in drug development. This recognition was codified by the United States Food and Drug Administration (FDA) in 2022 with the signing of the FDA Modernisation Act 2.0 into law.⁶ As such, in vitro organoid methods can now be accepted either as substitutes for, or in conjunction with, animal studies such as mouse models, which have been extensively used for preclinical validation due to their physiological and genetic similarity to humans.

Mouse model challenges

The use of mouse models has ethical considerations, but additionally, there are inherent drawbacks, including inter-species variability, which can limit the translatability of findings. Mice are often expensive and time-consuming to maintain and breed.⁷ Apart from bypassing ethical issues, organoids can provide faster and more robust outcomes than animal models, as they are more readily accessible and economical to use. Moreover, their intricate 3D structure and cellular diversity offer a more precise replication of specific structures and functions, making them promising candidates in disease modelling and drug testing.

Organoid challenges

Despite the promising developments in organoid cultures, there are several technical challenges. Among these challenges is the complexity of replicating the environment of the human body, which can consequently lead to variations in the structure and function of organoids. This heterogeneity, present within the same structure or between various organoids, could complicate our understanding of specific mechanisms of action when testing novel drugs in vitro.

Maintaining long-term stability is also a hurdle, as organoids frequently exceed the limit for passive diffusion of oxygen, which can lead to the formation of necrotic tissue in the core.⁸ Furthermore, the absence of immune, mesenchymal, or endothelial cells limits the applicability of organoids for the assessment of certain therapies, such as immuno-oncology treatments or drug metabolism studies where more complex models are needed.⁹

Using automation to drive the future of organoids

Nevertheless, the field of organoid research is rapidly progressing to address such technological challenges, matching the demands and expectations of preclinical research. Technological advancements include incorporating automation systems to foster the robustness and reproducibility of organoid systems, streamlining drug development stages and high-throughput drug screening. ^10,11 Applying more advanced analytical tools and imaging (eg, high-resolution live imaging, mass spectrometry imaging) will aid real-time tracking and analysis of cellular and molecular processes within the organoids.¹²

There is also a need for further improvement in the composition and functionality of the organoid systems. This includes the development of multi-lineage organoids aiming to represent interactions among various cells within an organ.¹³ Another direction involves using CRISPR/Cas9 gene-editing technology to generate genetically modified stem cell-derived organoids for investigating the onset, cause, and treatment of human diseases.¹⁴ Finally, implementing micro-manufacturing techniques such as 3D printing or laser cutting can help better control the shape and morphology of organoids.⁸

These technological advancements allow for the creation of more complex organoid systems that offer advantages over standard 2D culture or animal models. One example, still in the research phase involves organoids from a rectal biopsy from two patients, which has indicated a positive response to the ivacaftor via forskolin-induced swelling assay. The derived drug was given to both patients, to which researchers report the patients saw significant improvement.¹⁵

As research and workflows evolve, organoids are becoming an integral part of mainstream drug development, personalised medicine, and testing protocols. This can aid in the development of safer, more effective therapeutic strategies.

References

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