Organoids-on-a-chip

Abstract

Recent studies have demonstrated an array of stem cell-derived, self-organizing miniature organs, termed organoids, that replicate the key structural and functional characteristics of their in vivo counterparts. As organoid technology opens up new frontiers of research in biomedicine, there is an emerging need for innovative engineering approaches for the production, control, and analysis of organoids and their microenvironment. In this Review, we explore organ-on-a-chip technology as a platform to fulfill this need and examine how this technology may be leveraged to address major technical challenges in organoid research. We also discuss emerging opportunities and future obstacles for the development and application of organoid-on-a-chip technology.

Fig. 1.. Organ-on-a-chip design principles.

(A) Reductionist analysis of a target organ (lung) identifies alveoli as the functional unit composed of epithelial and endothelial cells separated by a thin interstitium. (B) An analogous model is constructed from three layers to bring these two cell types into physiological proximity. (C) To mimic breathing-induced mechanical activity, the cells are cyclically stretched by applying vacuum (vac) to the side chambers. [Illustration: BIOLines Lab]

Fig. 2.. Controlling the microenvironment of organoids-on-a-chip.

(A) Physiological morphogen gradients are generated by diffusion between the source and sink microchannels. Purmorphamine (PM; an Shh agonist) gradients promote self-organization and differentiation of HB9::GFP transgenic reporter ESCs in the culture chamber into motor neurons (MN; green). Opposing gradients of PM and BMP induce spatial localization of motor neurons and pluripotent ESCs (Oct4; red). Scale bar, 200 μm. [Adapted from (24) with permission] (B) An intestine-on-a-chip can generate opposing gradients of Wnt and a γ-secretase inhibitor (DAPT) along the crypt-villus axis, which induces compartmentalization of proliferative (Olfm4) and nonproliferative (KRT20) cells. Scale bar, 100 μm. [Adapted from (26) with permission from Elsevier] (C) In a tumor organoid-on-a-chip, blood vessels are formed in the central chamber by coculturing endothelial cells (ECs) with fibroblasts in a hydrogel. Vascular perfusability is demonstrated by the flow of fluorescent dextran. The vessels in the central chamber grow into the tumor chambers to vascularize tumoroids. Scale bars, 100 μm. [Adapted from (35) with permission of Royal Society of Chemistry] (D) Luminal flow in the stomach is simulated in a stomach organoid-on-a-chip by cannulating human gastric organoids (hGO) in Matrigel to deliver fluid. The flow also induces cyclic deformation of the organoids, mimicking gastric motility. Scale bars, 2 mm. [Adapted from (41) with permission of Royal Society of Chemistry] (E) Kidney organoids are cultured under flow in a 3D printed device. Fluid shear stress enhances vascularization and maturation of kidney organoids, as demonstrated by increased vascular density and robust expression of vascular markers (PECAM1 and MCAM) and PODXL⁺ cells. Scale bars, 100 μm. [Adapted from (42) with permission from Springer Nature]

Fig. 3.. Modeling tissue-tissue and organ-organ interactions in organoids-on-a-chip.

(A) A vascularized liver organoid model is established in a rocker-actuated device containing serially connected media and culture chambers. Liver organoids grown with human umbilical vein endothelial cells (HUVECs) show increased albumin expression (ALB; red). Scale bars, 500 μm (white), 50 μm (yellow). [Adapted from (45) with permission from John Wiley and Sons] (B) A microfluidic array is used to demonstrate a multiorganoid model. Scale bars, 200 μm. [Adapted from (45) with permission from John Wiley and Sons] (C) A microengineered heart-lung-liver model is created by fluidically linking three culture modules for drug testing. Bleomycin treatment results in a loss of beating in heart organoids in the three-organ model (middle graph), but this response is absent in the heart-only model (right graph). Scale bar, 100 μm. BPM, beats per minute. [Adapted from (46) (CC BY 4.0)]

Fig. 4.. Advanced organoid culture systems toward reduced variability.

(A) In an electrowetting device, externally applied electric field renders the surface over the energized electrode (yellow) hydrophilic, inducing the motion of a liquid droplet toward the energized electrode. This principle is used to automate culture of liver organoids. Organoids grown in droplets are retained by microfabricated structures and undergo contraction over time. Scale bar, 100 μm. [Adapted from (47) with permission of Royal Society of Chemistry] (B) A microfluidic high-density pillar array allows for size-based filtering (upstream) and capturing of organoids (downstream) for analysis of swelling due to cholera toxin. Scale bar, 100 μm. [Adapted from (48) with permission of AIP Publishing] (C) A sensor-integrated multiorgan platform enables in situ monitoring of organoids. Gold micro-electrodes act as immunobiosensors to detect specific antigens that use changes in interfacial electron-transfer kinetics of the probe, owing to their binding to surface-bound antibodies (Ab). SAM, self-assembled monolayer. [Adapted from (51)]