Progress and potential in organoid research

Tissue and organ biology are very challenging to study in mammals, and progress can be hindered, particularly in humans, by sample accessibility and ethical concerns. However, advances in stem cell culture have made it possible to derive in vitro 3D tissues called organoids, which capture some of the key multicellular, anatomical and even functional hallmarks of real organs at the micrometre to millimetre scale. Recent studies have demonstrated that organoids can be used to model organ development and disease and have a wide range of applications in basic research, drug discovery and regenerative medicine. Researchers are now beginning to take inspiration from other fields, such as bioengineering, to generate organoids that are more physiologically relevant and more amenable to real-life applications.

Engineering next generation organoids through guided stem cell self-organisation

Mikhail Nikolaev

One of the long-standing goals in the field of tissue engineering is the fabrication of de novo tissues or even organs to provide better tissue models for basic research and drug discovery, and to alleviate a shortage of donor organs in the future. Research in recent decades to understand tissue biology has led to the discovery of stem cell niches and the development of innovative protocols for the generation of three-dimensional in vivo-like tissues called organoids. Organoids represent multiple histological and functional aspects of real organs and offer unprecedented perspectives for modelling tissue development, regeneration, and disease in vitro. However, relying so far almost exclusively on spontaneous self-organisation of stem cells, organoids develop uncontrollably into small structures of highly variable size and architecture. Moreover, the closed, cystic architecture of most epithelial organoids limits their lifespan and makes experimental manipulation difficult. In this thesis, three innovative engineering technologies were developed that offer the possibility of steering in vitro stem cell patterning and organoid formation into more controllable and physiologically relevant miniature tissues.	The aim of the first project was to study how predefined geometric constraints, as they exist in vivo, affect organoid development. This required the development of a novel fabrication process of the topographically micro-patterned hydrogel surfaces. This approach allowed the generation of large arrays of the identical organoids, having pre-defined shape and size to study cellular mechanisms involved in the proper, stereotypical cell type pattering of intestinal organoids.		The second project focused on replicating tissue dynamics and aspects of organ physiology by developing a novel three-dimensional organ-on-chip approach. Using stem cells derived from patient biopsies, this technology enables to production of miniature versions of patientâs organs that can be used in personalized diagnostics and medical treatment assays.	Bioprinting has long been considered as one of the most promising technologies for fabricating organs in vitro. However, despite encouraging advances made in recent years, the degree of multicellular spatial complexity and function of organoids remains unmatched by any existing bioprinting technology. Therefore, the third project was aimed to develop a new bioprinting strategy that preserves local stem cell self-organization potential and extends organoids growth to the macroscopic scale.	Overall, this thesis introduces several cutting-edge technologies that offer the possibility to control in vitro organoid development and should therefore become efficient research tools to facilitate the translation of organoid technology towards pharmaceutical and clinical applications. Hydrogel micro-pattering is an efficient technology that can be widely used to explore the mechanisms by which tissue geometry can regulate morphogenesis of different organs and can be readily applied for high-throughput screening in pharmacological assays. The microscope-based bioprinter can be set-up in any laboratory to guide stem cell self-organization and tissue morphogenesis from millimetre to centimetre scales. The microfluidic organoid-on-chip concept should enable the creation of various miniature organs with complex three-dimensional spatial organisation and multicellular complexity for basic research and drug discovery.

EPFL2021

Recapitulating macro-scale tissue self-organization through organoid bioprinting

Jonathan Brassard, Moritz Hofer, Matthias Lütolf, Mikhail Nikolaev

A 3D bioprinting approach has been developed to facilitate tissue morphogenesis by directly depositing organoid-forming stem cells in an extracellular matrix, with the ability to generate intestinal epithelia and branched vascular tissue constructs. Bioprinting promises enormous control over the spatial deposition of cells in three dimensions(1-7), but current approaches have had limited success at reproducing the intricate micro-architecture, cell-type diversity and function of native tissues formed through cellular self-organization. We introduce a three-dimensional bioprinting concept that uses organoid-forming stem cells as building blocks that can be deposited directly into extracellular matrices conducive to spontaneous self-organization. By controlling the geometry and cellular density, we generated centimetre-scale tissues that comprise self-organized features such as lumens, branched vasculature and tubular intestinal epithelia with in vivo-like crypts and villus domains. Supporting cells were deposited to modulate morphogenesis in space and time, and different epithelial cells were printed sequentially to mimic the organ boundaries present in the gastrointestinal tract. We thus show how biofabrication and organoid technology can be merged to control tissue self-organization from millimetre to centimetre scales, opening new avenues for drug discovery, diagnostics and regenerative medicine.

NATURE RESEARCH2020

Engineering next generation organoids through guided stem cell self-organisation

Mikhail Nikolaev

One of the long-standing goals in the field of tissue engineering is the fabrication of de novo tissues or even organs to provide better tissue models for basic research and drug discovery, and to alleviate a shortage of donor organs in the future. Research in recent decades to understand tissue biology has led to the discovery of stem cell niches and the development of innovative protocols for the generation of three-dimensional in vivo-like tissues called organoids. Organoids represent multiple histological and functional aspects of real organs and offer unprecedented perspectives for modelling tissue development, regeneration, and disease in vitro. However, relying so far almost exclusively on spontaneous self-organisation of stem cells, organoids develop uncontrollably into small structures of highly variable size and architecture. Moreover, the closed, cystic architecture of most epithelial organoids limits their lifespan and makes experimental manipulation difficult. In this thesis, three innovative engineering technologies were developed that offer the possibility of steering in vitro stem cell patterning and organoid formation into more controllable and physiologically relevant miniature tissues.	The aim of the first project was to study how predefined geometric constraints, as they exist in vivo, affect organoid development. This required the development of a novel fabrication process of the topographically micro-patterned hydrogel surfaces. This approach allowed the generation of large arrays of the identical organoids, having pre-defined shape and size to study cellular mechanisms involved in the proper, stereotypical cell type pattering of intestinal organoids.		The second project focused on replicating tissue dynamics and aspects of organ physiology by developing a novel three-dimensional organ-on-chip approach. Using stem cells derived from patient biopsies, this technology enables to production of miniature versions of patientâs organs that can be used in personalized diagnostics and medical treatment assays.	Bioprinting has long been considered as one of the most promising technologies for fabricating organs in vitro. However, despite encouraging advances made in recent years, the degree of multicellular spatial complexity and function of organoids remains unmatched by any existing bioprinting technology. Therefore, the third project was aimed to develop a new bioprinting strategy that preserves local stem cell self-organization potential and extends organoids growth to the macroscopic scale.	Overall, this thesis introduces several cutting-edge technologies that offer the possibility to control in vitro organoid development and should therefore become efficient research tools to facilitate the translation of organoid technology towards pharmaceutical and clinical applications. Hydrogel micro-pattering is an efficient technology that can be widely used to explore the mechanisms by which tissue geometry can regulate morphogenesis of different organs and can be readily applied for high-throughput screening in pharmacological assays. The microscope-based bioprinter can be set-up in any laboratory to guide stem cell self-organization and tissue morphogenesis from millimetre to centimetre scales. The microfluidic organoid-on-chip concept should enable the creation of various miniature organs with complex three-dimensional spatial organisation and multicellular complexity for basic research and drug discovery.

EPFL2021