The successful exploitation of human stem cells for clinical use has long been hampered by the inability to maintain and expand adult stem cells while retaining their multi-lineage potential in vitro. However, advances in the understanding of stem cell niches and the role of key signaling modulators in controlling stem cell maintenance and differentiation have fuelled the development of new 3D in-vitro culture technologies that sustain stem-cell-driven formation of near-physiological, self-renewing and self-organizing tissues, called organoids (Fatehullah et al., 2016). These in-vitro 3D cellular clusters are derived exclusively from primary tissue, ESCs or iPSCs and they feature similar organ functionality as the tissue of origin. The widespread implementation of organoid-based technologies across academia and industry is testament to their importance as near-physiological models for use in both basic and translational research (Fatehullah et al., 2016).
Another advantage is that organoids can be expanded indefinitely, cryopreserved as bio-banks and easily manipulated using techniques similar to those established for traditional 2D monolayer cultures. Finally, the fact that primary-tissue-derived organoids lack mesenchyme/stroma provides a reductionist approach for studying the tissue type of interest without confounding influences from the local microenvironment.
The progress in generating organoids that faithfully reproduce the human in-vivo tissue composition has extended organoid applications from being just a basic research tool to a translational platform with a wide range of uses. The capacity to indefinitely culture organoids, without introducing genetic variation, makes them a sound model for high-throughput preclinical screenings, designing targeted and personalized therapies, and providing a source of fully functional tissue for regenerative medicine applications (Fatehullah et al., 2016).