Microfluidic Techniques for Next‐Generation Organoid Systems

Abstract

PSCs (iPSCs) and embryonic stem cells (ESCs), or adult stem cells (ASCs). Pioneered in the Yoshiki Sasai lab, where cortical tissues and optic-cuplike structures were firstly induced from ESCs in vitro, [1,2] organoid technology is regarded as a milestone in the stem cell field because it cast light upon the path to stably growing self-aggregating and selfrenewing stem cells into native tissues by mimicking developmental processes. [3] Subsequently, the rapidly developing field of organoid technology is advancing the maturity of technology for developing 3D macrostructures of organs such as the retina, [4] heart, [5] liver, [6] kidney, [7] and intestines. [8] In marked contrast to traditional 2D monocultures of cell lines losing cell-cell and cell-matrix interactions, organoids maintain and define in situ phenotypes fairly well. Despite organoids having shown great progress in tissue morphogenesis and organogenesis, the lack of organ-specific biochemical and physical microenvironments and nonphysiological shape and size have limited the function and real-life applications of organoids. Therefore, innovative strategies are urgently needed to precisely control perfusion conditions, nutrient supply, and mechanical cues in order to establish an optimal microenvironment for organoid cultures.The recently developed organs-on-a-chip (OOC) technology provides an in vivo-like microenvironment, showing great potential to enhance our understanding of organ development, physiology, and pathology. [9] Besides, the application of dynamic flow conditions or mechanical stimuli provided by OOCs can improve the terminal maturation of cells. [10,11] OOCs usually are comprised of specialized cell types and tissue elements (biochemical and biophysical cues of in vivo microenvironment), aiming to capture key functions of a specific organ. [12] Organoids rely on the self-organization of growing stem cell aggregates, whereas OOC is based on a reductionist engineering approach. In addition, organoids are multicellular 3D tissue with an architecture resembling some aspects of original tissues, which are not classified as OOC because of their production through stochastic self-organization from PSCs or ASCs and lack of microenvironment elements. [13] However, organoid and OOC techniques each have their own advantages, and they can be appropriately combined to enable highfidelity human modeling from stem cells. [14] Such synergistic Organoids are 3D multicellular structures derived from pluripotent stem cells (PSCs) or adult stem cells (ASCs), which have attracted increasing interest in the fields of drug screening, cell therapy, and regenerative medicine. Despite considerable success in culturing organoids with native microanatomy, challenges to achieving a physiologically relevant microenvironment remain. Complex dynamic feedback between cells and the extracellular matrix and uncontrollable mechano-physiological cues hamper the further study of organoid systems. Innovative engineering approaches are needed to produce, control, and analy...

Human organoids-on-chips for biomedical research and applications

“…Although the advanced OrgOCs systems are still far from faithfully recreating the functionality of native human organs, it has already demonstrated the unique advantages of simulating key aspects of human physiology and pathophysiology. Their unique features make them a reliable platform to reduce or even replace animal experiments for the preclinical assessment of drugs [140][141][142][143][144]. Even so, there is still a lot of room for improvement in OrgOCs models, and we can expect that these models offer increasing possibilities to reproduce near-physiological complex tissues and organs.…”

Two‐Photon Direct Laser Writing of pNIPAM Actuators in Microchannels for Dynamic Microfluidics

“…The field of microfluidics aims to integrate multiple laboratory steps into a single device while harnessing the unique behavior of fluids and flows at small scales to unravel chemical and biological processes. [1][2][3] Hereby, microfluidics emerges as a rapidly evolving technology and has proven itself valuable in numerous applications ranging from studying biochemical reactions on-chip [4,5] and culturing of single cells [6] and multicellular organoids, [7][8][9] to the production of polymeric microcapsules, [10] extracellular matrix protein microcapsules, [11] or giant unilamellar lipid vesicles. [12] Generally speaking, microfluidic devices can be categorized into either continuous phase (manipulation of a single phase) or discrete phase (utilization of immiscible phases to partition a liquid of interest) microfluidics.…”

A controllable perfusion microfluidic chip for facilitating the development of retinal ganglion cells in human retinal organoids

“…Its culture system depends on understanding human organs to develop engineered human-made constructs in which the organoids and their physiochemical microenvironment, tissue–tissue interfaces, and vascular perfusion are precisely recapitulated. 12 Thus, researchers are beginning to apply the power of microchip manufacturing techniques to develop retina-on-a-chip devices to promote the generation of anato–physiologically accurate tissues, which may revolutionize ocular science. Abdolvand's group developed a low FSS microfluidic chip to promote hPSC differentiation into critical retinal neurons.…”