Biomaterial-guided stem cell organoid engineering for modeling development and diseases

Abstract

Organoids are miniature models of organs to recapitulate spatiotemporal cellular organization and tissue functionality. The production of organoids has revolutionized the field of developmental biology, providing the possibility to study and guide human development and diseases in a dish. More recently, novel biomaterial-based culture systems demonstrated the feasibility and versatility to engineer and produce the organoids in a consistent and reproducible manner. By engineering proper tissue microenvironment, functional organoids have been able to exhibit spatial-distinct tissue patterning and morphogenesis. This review focuses on enabling technologies in the field of organoid engineering, including the control of biochemical and biophysical cues via hydrogels, as well as size and geometry control via microwell and microfabrication techniques. In addition, this review discusses the enhancement of organoid systems for therapeutic applications using biofabrication and organoid-on-chip platforms, which facilitate the assembly of complex organoid systems for in vitro modeling of development and diseases. STATEMENT OF SIGNIFICANCE: Stem cell organoids have revolutionized the fields of developmental biology and tissue engineering, providing the opportunity to study human organ development and disease progression in vitro. Various works have demonstrated that organoids can be generated using a wide variety of engineering tools, materials, and systems. Specific culture microenvironment is tailored to support the formation, function, and physiology of the organ of interest. This review highlights the importance of cellular microenvironment in organoid culture, the versatility of organoid engineering techniques, and future perspectives to build better organoid systems.

Keywords: Biomaterials; Organoids; Self-organization; Spatial patterning; Stem cell engineering.

Figure 1.. Hydrogel-based organoid engineering.

A) Hydrogels for organoid engineering require the appropriate chemical compositions to generate the organoid of interest. These components include the appropriate type of biopolymer, morphogens, growth factors and cells. B) Matrigel-based hydrogel has been used as the gold standard culture system for intestinal organoids, allowing for modeling of intestinal buds and crypts hallmark to intestinal tissue and further modeling of inflammatory bowel disease (Reproduced from J.R. Bayrer et al. 2018). C) Hydrogels with defined compositions can be engineered to generate intestinal organoids with comparable phenotypes as organoids cultured in Matrigel, thus overcoming limitations of harvested basement membrane matrices (Reproduced from Broguiere et al. Copyright 2018 © John Wiley and Sons).

Figure 2.. Microwells for organoid aggregate size control.

A) Microwells are a high-throughput method to consistently produce aggregates with controlled size for array-based scale-up processes. B) Controlling the aggregate size of mouse embryoid body using microwells was shown to significantly influence cardiogenesis and neurogenesis. (Reproduced from Choi et al. Copyright 2010 © Elsevier). C) A Milliwell system composed of a biomimetic hydrogel was able to differentiate retinal organoids with >90% efficiency. (Reproduced from Decembrini et al. 2020).

Figure 3.. Cell micropatterning to control organoid spatiotemporal organization.

A) Micropatterning can be used to supply surface constraint by culturing stem cells in specific geometries, therefore creating biophysical differentiation gradients. B) Micropatterns induced fate specification into differential cell gradients across the entire patterns to model events similar to gastrulation (Reproduced from Etoc et al. Copyright 2016 © Elsevier). C) The biophysical gradients induced spatial organization of hiPSCs at early stages, which further differentiated into cardiac lineages with spatial tissue patterning of cardiomyocytes and smooth muscle-like cells (Reproduced from Ma et al. 2015).

Figure 4.. Organoids as building blocks for tissue fabrication.

A) Organoids can also be used as building blocks to construct bulk tissues with specific features with biofabrication techniques. B) By molding organoids into a tissue construct, vasculature was bioprinted within the construct using sacrificial inks (Reproduced from Skylar-Scott et al. 2019). C) By taking advantage of high-throughput organoid production techniques, organoids can be harnessed as single units to manufacture and assemble large-scale tissues. Using “bioassembly” technique, organoids can be deposited and constructed into desired architectures (Reproduced from Ay an et al. 2020).

Figure 5.. Organoid-on-chip platforms for biomimetic applications.

A) Chip platforms can serve to enhance current organoid systems by careful design of microfluidic networks. These networks can support intricate complex biomimetic processes, such as nutrient perfusion, biochemical gradients, and multi-organoid interactions. B) Microfluidic devices can be designed to supply morphogen gradients to induce essential tissue patterning, such as the polarization seen in neural tube patterning (Reproduced from Demers et al. 2016). C) Retina-on-chip organoids with active perfusions promotes the spatiotemporal organization of retinal epithelium and photoreceptors (Reproduced from Achberger et al. 2018).