Developing a Multidisciplinary Approach for Engineering Stem Cell Organoids

Abstract

Recent advances in stem cell biology, synthetic biology, bioengineering, and biotechnology have included significant work leading to the development of stem cell-derived organoids. The growing popularity of organoid research and use of organoids is widely due to the fact that these three-dimensional cellular structures better model human physiology compared to traditional in vitro and in vivo methods by recapitulating many biologically relevant parameters. Organoids show great promise for a wide range of applications, such as for use in disease modeling, drug discovery, and regenerative medicine. However, many challenges associated with reproducibility and scale up still remain. Identification of the conditions which generate a robust environment that predictably promotes cellular self-assembly and organization leading to organoid formation is critical and requires a multidisciplinary approach. To accomplish this we need to identify a cellular source, engineer a matrix to stimulate cell-cell and cell-matrix interactions, and provide the biochemical and biophysical cues which mimic that of the in vivo environment. Discussion of the components needed for organoid development and formation is reviewed herein, as well as specific organoid examples and the promise of this research for the future.

Keywords: Biomaterials; Brain; Cardiac; Intestine; Self-assembly; Stem cells.

FIGURE 1.

Process of organoid formation. Organoid formation can be initiated from pluripotent stem cells or multipotent adult stem cells. When provided with the appropriate biophysical and biochemical cues to that of the specific in vivo environment, cell aggregates form and then are embedded in a hydrogel matrix. When cultured in the presence of niche factors, the cells begin to self-assemble and differentiate generating organoids with several cell types. The derived organoids can be used to recapitulate organogenesis and serve as systems for disease modeling and high throughput drug testing.

FIGURE 2.

Aggregation of stem cells in/on 3D engineered matrices. (a) Synthetic materials must be modified with cell adhesion sites, such as the RGD peptide, to promote cell–ECM interactions via integrin binding. In addition, mechanical stiffness of the scaffold affects cell migration, proliferation, and differentiation due to different degrees of cell–cell and cell–ECM interactions. Soft matrices limit cell–ECM interactions whereas stiff matrices limit cell–cell interactions. A matrix of intermediate stiffness, optimizes cell–cell and cell–ECM interactions, promoting cell proliferation, organization, and differentiation. (b) Proteolytic degradation sites are another important component for organoid culture as they allow for dynamic mechanical properties. A stiffer matrix can be used to promote cell proliferation and can then degrade to yield a softer matrix, which promotes cell organization and organoid formation. (c) Alternatively, stem cells can form aggregates in microwells where the cells take the shape of the well. This allows for formation of homogenous aggregates where the size and shape of the aggregates can be controlled. The aggregates are then seeded in 3D culture for organoid formation.