Organoid and microfluidics-based platforms for drug screening in COVID-19

Abstract

Proposing efficient prophylactic and therapeutic strategies for coronavirus 2019 (COVID-19) requires precise knowledge of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pathogenesis. An array of platforms, including organoids and microfluidic devices, have provided a basis for studies of SARS-CoV-2. Here, we summarize available models as well as novel drug screening approaches, from simple to more advanced platforms. Notably, organoids and microfluidic devices offer promising perspectives for the clinical translation of basic science, such as screening therapeutics candidates. Overall, modifying these advanced micro and macro 3D platforms for disease modeling and combining them with recent advances in drug screening has significant potential for the discovery of novel potent drugs against COVID-19.

Keywords: COVID-19 modeling; Drug screening; Microfluidic technology; Organoid technology; SARS-CoV-2.

Figure 1

Organoids as potential platforms for investigating the role of genetic background in coronavirus 2019 (COVID-19) pathogenesis. Genetic polymorphisms in three classes of gene, including receptors (a), HLAs (b) and other immune-related genes (c), might affect the susceptibility of individuals exposed to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). For instance, a. human leukocyte antigen (HLA)-A*11:01 causes more severe symptoms in patients with COVID-19. Manipulating the organoid genome through cluster regularly interspaced palindromic repeat (CRISPR) technology could help to reveal the direct cytopathic effects of virus together with other involved mechanisms. Abbreviations: ACE, angiotensin-converting enzyme; IFITM, interferon-induced transmembrane proteins; MHC, major histocompatibility complex.

Figure 2

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) disease modeling. (a) Platforms for disease modeling. In vitro (2D adherent cultures and 3D organoids), and in vivo modeling have thus far been widely used to assess pathogenesis and test candidate drugs. In summary, Vero E6 cells and human airway epithelial cells (HAECs) are two most common cell lines used in SARS-CoV-2 studies. Genetically modified mice, hamsters, ferrets, and various nonhuman primates are among the animals used for assessing the pathogenesis and testing candidate drugs. For instance, mRNA vaccine candidates for COVID-19 have been evaluated in mice. In addition, clinical benefits of remdesivir have been shown in the Rhesus macaque model of coronavirus 2019 (COVID-19). Considering the limitations of these models, including failure to represent the multiple aspects of the infection and the inability to mimic the complex nature of human immunity, organoids are attracting attention because of their ability to show host–microbe interactions and their potential for drug screening. Organoids also have limitations such as in mimicking native tissue microenvironment, long-term culture and expansion, reliance on Matrigel, and lack of full maturity. These need to be addressed in future. (b) Organoids for mechanism elucidation in COVID-19. Given the notable manifestation ov COVID-19 in lungs, kidneys, gastrointestinal system, liver, and brain, among others, scientists have focused on creating the corresponding organoids. Thus far, human bronchial, kidney, intestinal, liver ductal, and brain organoids contain various types of cell, have been developed to mimic virus entry and recapitulate the viral life cycle, along with the possible mechanism involved in pathogenesis, including the direct cytopathic effects. Abbreviation: ACE, angiotensin-converting enzyme.

Figure 2

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) disease modeling. (a) Platforms for disease modeling. In vitro (2D adherent cultures and 3D organoids), and in vivo modeling have thus far been widely used to assess pathogenesis and test candidate drugs. In summary, Vero E6 cells and human airway epithelial cells (HAECs) are two most common cell lines used in SARS-CoV-2 studies. Genetically modified mice, hamsters, ferrets, and various nonhuman primates are among the animals used for assessing the pathogenesis and testing candidate drugs. For instance, mRNA vaccine candidates for COVID-19 have been evaluated in mice. In addition, clinical benefits of remdesivir have been shown in the Rhesus macaque model of coronavirus 2019 (COVID-19). Considering the limitations of these models, including failure to represent the multiple aspects of the infection and the inability to mimic the complex nature of human immunity, organoids are attracting attention because of their ability to show host–microbe interactions and their potential for drug screening. Organoids also have limitations such as in mimicking native tissue microenvironment, long-term culture and expansion, reliance on Matrigel, and lack of full maturity. These need to be addressed in future. (b) Organoids for mechanism elucidation in COVID-19. Given the notable manifestation ov COVID-19 in lungs, kidneys, gastrointestinal system, liver, and brain, among others, scientists have focused on creating the corresponding organoids. Thus far, human bronchial, kidney, intestinal, liver ductal, and brain organoids contain various types of cell, have been developed to mimic virus entry and recapitulate the viral life cycle, along with the possible mechanism involved in pathogenesis, including the direct cytopathic effects. Abbreviation: ACE, angiotensin-converting enzyme.

Figure 3

Drug-screening platforms. Genome-based strategies and computational approach are two main measures for drug-screening against coronavirus 2019 (COVID-19). Using programmed ribosomal frameshifting (PRF), a strategy for the translation of nonstructural viral proteins, the efficacy of many US Food and Drug Administration (FDA)-approved drugs have been evaluated in the context of COVID-19. Another genome-based strategy, Nluc, is taking advantage of nanoluciferase gene insertion in viral genome and provides both diagnostic and therapeutic applications for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). In AlphaLISA technology, excitation of the donor bead at a certain wavelength leads to generation of radical oxygen species, which activates the acceptor bead to produce light. Computational approaches comprise MT-DTI, homology modeling, high-content morphological profiling, and immunoinformatics. The first three strategies have been used so far to evaluate a range of FDA-approved drugs against SARS-CoV-2, whereas immunoinformatics is applied for the detection of the most reliable antigens able to confer the ability to produce strong immune responses and can be used in vaccine development. Abbreviation: AlphaLISA, amplified luminescent proximity homogenous assay.

Figure 4

Future perspectives for coronavirus 2019 (COVID-19) modeling. Variability, multigerm-layer composition, and high-throughput analysis are three main subjects that need further investigation in organoid platforms. Reliable recreation of an organoid is an important requirement for achieving comparable results. Thus far, different strategies have been used to address this challenge. These contain optimization of the culture media and using certain matrices, among others. Using different components of germ layers is another promising area to create fully functional organoids with the most similarity to the human body environment. High-throughput screening of candidate drugs is another promised field for the future applications of organoids.

Figure 5

Development of advanced technology in drug screening. Given limitations of animal research, using novel and more practical strategies appears imperative. To this end, chip platforms [from organ-on-chip (OoC) to human-on-chip (HoC)] have been progressed extensively to emulate the complicated characteristics of human body and provide a more reliable platform in the translational clinical setting. Human lung-on-chip and gut-on-chip are two examples of such advanced technology that have been used in COVID-19 studies. OoC/HoC technology offers great opportunities for high-throughput screening of candidate drugs.