Stem Cell-derived Organoids Research Articles

Probiotic Properties of Escherichia coli Nissle in Human Intestinal Organoids.

Escherichia coli strain Nissle has been used as a probiotic and therapeutic agent for over a century. Reports suggest that Nissle protects mice from enterohemorrhagic E. coli (EHEC) O157:H7 strains; however, mice are not very susceptible to O157:H7 and are not accurate models for O157:H7 infection in humans. Also, Nissle is closely related to uropathogenic E. coli (UPEC) strain CFT073, suggesting that Nissle could have pathogenic potential. To assess the safety of and protection conferred by Nissle, we modeled infection in stem cell-derived human intestinal organoids (HIOs). HIOs replicate the structure and function of human intestinal tissue. HIOs have a lumen enclosed by a single cell layer of differentiated epithelium, which is surrounded by a diffuse mesenchymal layer. An epithelial barrier which excludes the luminal contents from the surrounding cell layers and medium develops. Nissle appeared to be nonpathogenic; 103 CFU were microinjected into the lumen, and after 3 days, 107 CFU were recovered and the epithelial barrier remained intact. In contrast, microinjected EHEC and UPEC bacteria destroyed the epithelial barrier. To assess the protection conferred by Nissle, HIOs microinjected with Nissle were challenged after 18 to 24 h with EHEC or UPEC. Preincubation with Nissle prevented the loss of the epithelial barrier function, the loss of E-cadherin expression, the increased production of reactive oxygen species, and apoptosis. Nissle did not replicate in the HIO coculture, while the pathogenic strains did replicate, suggesting that Nissle conferred protection via activation of host defenses and not by eliminating competing strains. Nissle was shown to be susceptible to some Shiga toxin phage, and Nissle lysogens could produce Shiga toxin.IMPORTANCE Probiotic, or beneficial, bacteria, such as E. coli Nissle, hold promise for the treatment of human disease. More study is needed to fully realize the potential of probiotics. Safety and efficacy studies are critically important; however, mice are poor models for many human intestinal diseases. We used stem cell-derived human intestinal organoid tissues to evaluate the safety of Nissle and its ability to protect from pathogenic E. coli bacteria. Nissle was found to be safe. Human intestinal tissues were not harmed by the Nissle bacteria introduced into the digestive tract. In contrast, pathogenic E. coli bacteria destroyed the intestinal tissues, and importantly, Nissle conferred protection from the pathogenic E. coli bacteria. Nissle did not kill the pathogenic E. coli bacteria, and protection likely occurred via the activation of human defenses. Human intestinal tissues provide a powerful way to study complex host-microbe interactions.

Convolutional Neural Networks Can Predict Retinal Differentiation in Retinal Organoids.

We have developed a deep learning-based computer algorithm to recognize and predict retinal differentiation in stem cell-derived organoids based on bright-field imaging. The three-dimensional “organoid” approach for the differentiation of pluripotent stem cells (PSC) into retinal and other neural tissues has become a major in vitro strategy to recapitulate development. We decided to develop a universal, robust, and non-invasive method to assess retinal differentiation that would not require chemical probes or reporter gene expression. We hypothesized that basic-contrast bright-field (BF) images contain sufficient information on tissue specification, and it is possible to extract this data using convolutional neural networks (CNNs). Retina-specific Rx-green fluorescent protein mouse embryonic reporter stem cells have been used for all of the differentiation experiments in this work. The BF images of organoids have been taken on day 5 and fluorescent on day 9. To train the CNN, we utilized a transfer learning approach: ImageNet pre-trained ResNet50v2, VGG19, Xception, and DenseNet121 CNNs had been trained on labeled BF images of the organoids, divided into two categories (retina and non-retina), based on the fluorescent reporter gene expression. The best-performing classifier with ResNet50v2 architecture showed a receiver operating characteristic-area under the curve score of 0.91 on a test dataset. A comparison of the best-performing CNN with the human-based classifier showed that the CNN algorithm performs better than the expert in predicting organoid fate (84% vs. 67 ± 6% of correct predictions, respectively), confirming our original hypothesis. Overall, we have demonstrated that the computer algorithm can successfully recognize and predict retinal differentiation in organoids before the onset of reporter gene expression. This is the first demonstration of CNN’s ability to classify stem cell-derived tissue in vitro.

Congruence of Transcription Programs in Adult Stem Cell-Derived Jejunum Organoids and Original Tissue During Long-Term Culture.

The emergence of intestinal organoids, as a stem cell-based self-renewable model system, has led to many studies on intestinal development and cell-cell signaling. However, potential issues regarding the phenotypic stability and reproducibility of the methodology during culture still needs to be addressed for different organoids. Here we investigated the transcriptomes of jejunum organoids derived from the same pig as well as batch-to-batch variation of organoids derived from different pigs over long-term passage. The set of genes expressed in organoids closely resembled that of the tissue of origin, including small intestine specific genes, for at least 17 passages. Minor differences in gene expression were observed between individual organoid cultures. In contrast, most small intestine-specific genes were not expressed in the jejunum cell line IPEC-J2, which also showed gene expression consistent with cancer phenotypes. We conclude that intestinal organoids provide a robust and stable model for translational research with clear advantages over transformed cells.

Application of Human Induced Pluripotent Stem Cell-Derived Intestinal Organoids as a Model of Epithelial Damage and Fibrosis in Inflammatory Bowel Disease.

Inflammatory bowel disease, which typically manifests as Crohn's disease and ulcerative colitis, is caused by the abnormal production of cytokines such as tumor necrosis factor (TNF)-α and transforming growth factor (TGF)-β. These cytokines damage intestinal epithelial cells and trigger fibrosis, respectively, for which the current in vitro models have many limitations. Therefore, we tested whether human induced pluripotent stem cell-derived intestinal organoids (HiOs) can mimic inflammatory bowel disease (IBD), and whether such a model is suitable for drug screening. HiOs were treated with TNF-α and TGF-β to construct mucosal damage and fibrosis models. TNF-α diminished the mRNA expression of intestinal epithelial cell and goblet cell markers in HiOs. TNF-α also induced epithelial cell damage and degradation of tight junctions but not in the presence of infliximab, an antibody used in the clinic to deplete TNF-α. Furthermore, permeation of the non-absorbable marker FD-4 was observed in HiOs treated with TNF-α or ethylene glycol tetraacetic acid (EGTA), but not in the presence of infliximab. In contrast, TNF-α and TGF-β induced mRNA expression of mesenchymal and fibrosis markers, as well as epithelial-mesenchymal transition. SB431542, a TGF-β inhibitor, significantly reversed these events. The data indicate that HiOs mimic mucosal damage and fibrosis due to IBD and are thus suitable models for drug screening.

Human Pluripotent Stem Cell-Derived Organoids as Models of Liver Disease

There are few invitro models for studying the 3-dimensional interactions among different liver cell types during organogenesis or disease development. We aimed to generate hepatic organoids that comprise different parenchymal liver cell types and have structural features of the liver, using human pluripotent stem cells. We cultured H1 human embryonic stem cells (WA-01, passage 27-40) and induced pluripotent stem cells (GM23338) with a series of chemically defined and serum-free media to induce formation of posterior foregut cells, which were differentiated in 3 dimensions into hepatic endoderm spheroids and stepwise into hepatoblast spheroids. Hepatoblast spheroids were reseeded in a high-throughput format and induced to form hepatic organoids; development of functional bile canaliculi was imaged live. Levels of albumin and apolipoprotein B were measured in cell culture supernatants using an enzyme-linked immunosorbent assay. Levels of gamma glutamyl transferase and alkaline phosphatase were measured in cholangiocytes. Organoids were incubated with troglitazone for varying periods and bile transport and accumulation were visualized by live-imaging microscopy. Organoids were incubated with oleic and palmitic acid, and formation of lipid droplets was visualized by staining. We compared gene expression profiles of organoids incubated with free fatty acids or without. We also compared gene expression profiles between liver tissue samples from patients with nonalcoholic steatohepatitis (NASH) versus without. We quantified hepatocyte and cholangiocyte populations in organoids using immunostaining and flow cytometry; cholangiocyte proliferation of cholangiocytes was measured. We compared the bile canaliculi network in the organoids incubated with versus without free fatty acids by live imaging. Cells in organoids differentiated into hepatocytes and cholangiocytes, based on the expression of albumin and cytokeratin 7. Hepatocytes were functional, based on secretion of albumin and apolipoprotein B and cytochrome P450 activity; cholangiocytes were functional, based on gamma glutamyl transferase and alkaline phosphatase activity and proliferative responses to secretin. The organoids organized a functional bile canaliculi system, which was disrupted by cholestasis-inducing drugs such as troglitazone. Organoids incubated with free fatty acids had gene expression signatures similar to those of liver tissues from patients with NASH. Incubation of organoids with free fatty acid-enriched media resulted in structural changes associated with nonalcoholic fatty liver disease, such as decay of bile canaliculi network and ductular reactions. We developed a hepatic organoid platform with human cells that can be used to model complex liver diseases, including NASH.

Pluripotent stem cell-derived retinal organoids for disease modeling and development of therapies.

Retinal diseases constitute a genetically and phenotypically diverse group of clinical conditions leading to vision impairment or blindness with limited treatment options. Advances in reprogramming of somatic cells to induced pluripotent stem cells and generation of three‐dimensional organoids resembling the native retina offer promising tools to interrogate disease mechanisms and evaluate potential therapies for currently incurable retinal neurodegeneration. Next‐generation sequencing, single‐cell analysis, advanced electrophysiology, and high‐throughput screening approaches are expected to greatly expand the utility of stem cell‐derived retinal cells and organoids for developing personalized treatments. In this review, we discuss the current status and future potential of combining retinal organoids as human models with recent technologies to advance the development of gene, cell, and drug therapies for retinopathies.

Room temperature shipment does not affect the biological activity of pluripotent stem cell-derived retinal organoids.

The generation of laminated and light responsive retinal organoids from induced pluripotent stem cells (iPSCs) provides a powerful tool for the study of retinal diseases and drug discovery and a robust platform for cell-based therapies. The aim of this study is to investigate whether retinal organoids can retain their morphological and functional characteristics upon storage at room temperature (RT) conditions and shipment by air using a commercially available container that maintains the environment at ambient temperature. Morphological analysis and measurements of neuroepithelial thickness revealed no differences between control, RT incubated and shipped organoids. Similarly immunohistochemical analysis showed no differences in cell type composition and position within the laminated retinal structure. All groups showed a similar response to light, suggesting that the biological function of retinal organoids was not affected by RT storage or shipment. These findings provide an advance in transport of ready-made retinal organoids, increasing their availability to many research and pharma labs worldwide and facilitating cross-collaborative research.

Decellularized Tissue Matrix Enhances Self-Assembly of Islet Organoids from Pluripotent Stem Cell Differentiation.

Regenerating human islet organoids from stem cells remains a significant challenge because of our limited knowledge on cues essential for developing the endocrine organoids in vitro. In this study, we discovered that a natural material prepared from a decellularized rat pancreatic extracellular matrix (dpECM) induces the self-assembly of human islet organoids during induced pluripotent stem cell (iPSC) pancreatic differentiation. For the first time, we demonstrated that the iPSC-derived islet organoids formed in the presence of the dpECM are capable of glucose-responsive secretion of both insulin and glucagon, two major hormones that maintain blood glucose homeostasis. The characterization of the organoids revealed that the organoids consisted of all major endocrine cell types, including α, β, δ, and pancreatic polypeptide cells, that were assembled into a tissue architecture similar to that of human islets. The exposure of iPSCs to the dpECM during differentiation resulted in considerably elevated expression of key pancreatic transcription factors such as PDX-1, MAFA, and NKX6.1 and the production of all major hormones, including insulin, glucagon, somatostatin, and pancreatic polypeptide from stem cell-derived organoids. This study highlights the importance of natural, bioactive biomaterials for building microenvironments crucial to regenerating islet organoids from stem cells.

Long-Term Expansion of Functional Human Pluripotent Stem Cell-Derived Hepatic Organoids.

A human cell-based liver model capable of long-term expansion and mature hepatic function is a fundamental requirement for pre-clinical drug development. We previously established self-renewing and functionally mature human pluripotent stem cell-derived liver organoids as an alternate to primary human hepatocytes. In this study, we tested long-term prolonged culture of organoids to increase their maturity. Organoid growing at the edge of Matrigel started to deteriorate two weeks after culturing, and the expression levels of the functional mature hepatocyte marker ALB were decreased at four weeks of culture. Replating the organoids weekly at a 1：2 ratio in fresh Matrigel, resulted in healthier morphology with a thicker layer compared to organoids maintained on the same Matrigel and significantly increased ALB expression until three weeks, although, it decreased sharply at four weeks. The levels of the fetal hepatocyte marker AFP were considerably increased in long-term cultures of organoids. Therefore, we performed serial passaging of organoids, whereby they were mechanically split weekly at a 1：3∼1：5 ratio in fresh Matrigel. The organoids expanded so far over passage 55, or 1 year, without growth retardation and maintained a normal karyotype after long-term cryopreservation. Differentiation potentials were maintained or increased after long-term passaging, while AFP expression considerably decreased after passaging. Therefore, these data demonstrate that organoids can be exponentially expanded by serial passaging, while maintaining long-term functional maturation potential. Thus, hepatic organoids can be a practical and renewable cell source for human cell-based and personalized 3D liver models.

Benchmarking pluripotent stem cell-derived organoid models

Cerebral organoids are stem cell-derived, self-organizing three-dimensional cultures. Owing to the remarkable degree to which they recreate the cellular diversity observed in the human brain, they have attracted significant interest as a novel model system for research and drug development, as well as capturing the public imagination. However, many questions remain about the extent to which these cultures recapitulate neurodevelopment and the defining features of the human brain. To clarify the fidelity of human organoid models, Bhaduri and colleagues compared the molecular profile of brain organoid cells with that of primary cells from fetal brain. They observed that, whilst brain organoids broadly recapitulate the cellular profile of human brain, they lack the subtypes of cell classes seen in human brain. In addition, they showed marked expression of cellular stress markers, which could be reversed by transplanting organoid cells into neonatal mouse brain. The authors hypothesise that in vitro culture induces a cellular stress response and that it is this that impairs maturation. Thus, whilst their findings strike a note of caution in the use of organoids as a model for early human brain development, they lay a foundation for improving the accuracy of organoid models in the future.

Modeling and Targeting Alzheimer's Disease With Organoids.

Human neurodegenerative diseases, such as Alzheimer’s disease (AD), are not easily modeled in vitro due to the inaccessibility of brain tissue and the level of complexity required by existing cell culture systems. Three-dimensional (3D) brain organoid systems generated from human pluripotent stem cells (hPSCs) have demonstrated considerable potential in recapitulating key features of AD pathophysiology, such as amyloid plaque- and neurofibrillary tangle-like structures. A number of AD brain organoid models have also been used as platforms to assess the efficacy of pharmacological agents in disease progression. However, despite the fact that stem cell-derived brain organoids mimic early aspects of brain development, they fail to model complex cell-cell interactions pertaining to different regions of the human brain and aspects of natural processes such as cell differentiation and aging. Here, we review current advances and limitations accompanying several hPSC-derived organoid methodologies, as well as recent attempts to utilize them as therapeutic platforms. We additionally discuss comparative benefits and disadvantages of the various hPSC-derived organoid generation protocols and differentiation strategies. Lastly, we provide a comparison of hPSC-derived organoids to primary tissue-derived organoids, examining the future potential and advantages of both systems in modeling neurodegenerative disorders, especially AD.

Optimization of Renal Organoid and Organotypic Culture for Vascularization, Extended Development, and Improved Microscopy Imaging.

Embryonic kidney organotypic cultures, and especially pluripotent stem cell-derived kidney organoids, are excellent tools for following developmental processes and modelling kidney disease. However, the models are limited by a lack of vascularization and functionality. To address this, an improved protocol for the method of xenografting cells and tissues to the chorioallantoic membrane (CAM) of an avian embryo to gain vascularization and restoration of blood flow was developed. The grafts are overlaid with custom-made minireservoirs that fix the samples to the CAM and supply them with culture medium that protects the grafts from drying. The improved culture method allows xenografts to grow for up to 9 days. The manuscript also describes how to provide optimal conditions for long-term confocal imaging of renal organoids and organotypic cultures using the previously published Fixed Z-Direction (FiZD) method. This method gently compresses an embryonic organ or organoid between a glass coverslip and membrane in a large amount of medium and provides excellent conditions for imaging for up to 12 days. Together, these methods allow vascularization and blood flow to renal organoids and organotypic kidney cultures with improved confocal imaging. The methods described here are highly beneficial for studying fundamental and applied functions of kidneys ex vivo. Both methods are applicable to various types of tissues and organoids.

Role of RB1 in human embryonic stem cell-derived retinal organoids

Three-dimensional (3D) organoid models derived from human pluripotent stem cells provide a platform for studying human development and understanding disease mechanisms. Most studies that examine biallelic inactivation of the cell cycle regulator Retinoblastoma 1 (RB1) and the link to retinoblastoma is in mice, however, less is known regarding the pathophysiological role of RB1 during human retinal development. To study the role of RB1 in early human retinal development and tumor formation, we generated retinal organoids from CRISPR/Cas9-derived RB1-null human embryonic stem cells (hESCs). We showed that RB is abundantly expressed in retinal progenitor cells in retinal organoids and loss of RB1 promotes S-phase entry. Furthermore, loss of RB1 resulted in widespread apoptosis and reduced the number of photoreceptor, ganglion, and bipolar cells. Interestingly, RB1 mutation in retinal organoids did not result in retinoblastoma formation in vitro or in the vitreous body of NOD/SCID immunodeficient mice. Together, our work identifies a crucial function for RB1 in human retinal development and suggests that RB1 deletion alone is not sufficient for tumor development, at least in human retinal organoids.

Organoids as a Powerful Model for Respiratory Diseases.

Insults to the alveoli usually lead to inefficient gas exchange or even respiratory failure, which is difficult to model in animal studies. Over the past decade, stem cell-derived self-organizing three-dimensional organoids have emerged as a new avenue to recapitulate respiratory diseases in a dish. Alveolar organoids have improved our understanding of the mechanisms underlying tissue homeostasis and pathological alterations in alveoli. From this perspective, we review the state-of-the-art technology on establishing alveolar organoids from endogenous lung epithelial stem/progenitor cells or pluripotent stem cells, as well as the use of alveolar organoids for the study of respiratory diseases, including idiopathic pulmonary fibrosis, tuberculosis infection, and respiratory virus infection. We also discuss challenges that need to be overcome for future application of alveolar organoids in individualized medicine.

Evaluation of cisplatin-induced injury in human kidney organoids.

Acute kidney injury (AKI) remains a major global healthcare problem, and there is a need to develop human-based models to study AKI in vitro. Toward this goal, we have characterized induced pluripotent stem cell-derived human kidney organoids and their response to cisplatin, a chemotherapeutic drug that induces AKI and preferentially damages the proximal tubule. We found that a single treatment with 50 µM cisplatin induces hepatitis A virus cellular receptor 1 (HAVCR1) and C-X-C motif chemokine ligand 8 (CXCL8) expression, DNA damage (γH2AX), and cell death in the organoids but greatly impairs organoid viability. DNA damage was not specific to the proximal tubule but also affected the distal tubule and interstitial cell populations. This lack of specificity correlated with low expression of proximal tubule-specific SLC22A2/organic cation transporter 2 (OCT2) for cisplatin. To improve viability, we developed a repeated low-dose regimen of 4 × 5 µM cisplatin over 7 days and found this caused less toxicity while still inducing a robust injury response that included secretion of known AKI biomarkers and inflammatory cytokines. This work validates the use of human kidney organoids to model aspects of cisplatin-induced injury, with the potential to identify new AKI biomarkers and develop better therapies.

Uncovering cell biology in the third dimension.

Developmental biology has long benefited from studies of classic model organisms. These model systems have provided the fundamental understanding of general principles of development, as well as insight into genes and signaling pathways that control unique aspects of cell fate specification and tissue morphogenesis. Because human brain development cannot be studied in vivo, scientists have relied on these model systems to study basic principles underlying the development of this complex organ as many of these genes and signaling pathways play conserved roles in human development. However, recent studies have shown species-specific signatures in neurodevelopment such as the transcriptome of outer-radial glia, suggesting use of a human-derived model remains imperative. Over the past decade, human stem cell-derived brain organoids have emerged as a biologically relevant model system to study normal human brain development and neurological diseases. Here, we provide a historical perspective of this emerging model system, discuss current systems and limitations, and propose that new mechanistic insight into cell biology can be revealed using these three-dimensional brain structures.

Drug compound screening in single and integrated multi-organoid body-on-a-chip systems

Current practices in drug development have led to therapeutic compounds being approved for widespread use in humans, only to be later withdrawn due to unanticipated toxicity. These occurrences are largely the result of erroneous data generated by in vivo and in vitro preclinical models that do not accurately recapitulate human physiology. Herein, a human primary cell- and stem cell-derived 3D organoid technology is employed to screen a panel of drugs that were recalled from market by the FDA. The platform is comprised of multiple tissue organoid types that remain viable for at least 28 days, in vitro. For many of these compounds, the 3D organoid system was able to demonstrate toxicity. Furthermore, organoids exposed to non-toxic compounds remained viable at clinically relevant doses. Additional experiments were performed on integrated multi-organoid systems containing liver, cardiac, lung, vascular, testis, colon, and brain. These integrated systems proved to maintain viability and expressed functional biomarkers, long-term. Examples are provided that demonstrate how multi-organoid ‘body-on-a-chip’ systems may be used to model the interdependent metabolism and downstream effects of drugs across multiple tissues in a single platform. Such 3D in vitro systems represent a more physiologically relevant model for drug screening and will likely reduce the cost and failure rate associated with the approval of new drugs.

High-throughput screening of human induced pluripotent stem cell-derived brain organoids

BackgroundThe need for scalable high-throughput screening (HTS) approaches for 3D human stem cell platforms remains a central challenge for disease modeling and drug discovery. We have developed a workflow to screen cortical organoids across platforms. New methodWe used serum-free embryoid bodies (SFEBs) derived from human induced pluripotent stem cells (hiPSCs) and employed high-content imaging (HCI) to assess neurite outgrowth and cellular composition within SFEBs. We multiplexed this screening assay with both multi-electrode arrays (MEAs) and single-cell calcium imaging. ResultsHCI was used to assess the number of excitatory neurons (VGlut+) in experimental replicates of hiPSC-derived SFEBs, demonstrating experiment-to-experiment consistency. Neurite detection using HCI was applied to assess neurite morphology. MEA analysis showed that firing and burst rates in SFEBs decreased with blockade of NMDARs and AMPARs and increased with GABAR blockade. We also demonstrate effective combination of both MEA and HCI to analyze VGlut+ populations surrounding electrodes within MEAs. HCI-based (Ca2+) transient analysis revealed firing in individual cells surrounding active MEA electrodes. Comparison with existing methodsCurrent methods to generate neural organoids show high degrees of variability, and often require sectioning or special handling for analysis. The protocol outlined in this manuscript generates SFEBs with high degree of consistency making them amenable to complex assays combining HTS and electrophysiology allowing for an in-depth, unbiased analysis. ConclusionsSFEBs can be used in combination with HTS to compensate for experimental variability common in 3D cultures, while significantly decreasing processing speed, making this an efficient starting point for phenotypic drug screening.

Isolation and Culture of Human-Induced Pluripotent Stem Cell-Derived Cerebral Organoid Cells.

The advent of human-induced pluripotent stem cell (iPSC)-derived three-dimensional (3D) cerebral organoids provides unprecedented opportunities of modeling human brains in states of health and disorder. Emerging data supports that cerebral organoids allow for more relevant in vitro systems for studying the human brain system and diseases than the current widely used 2D monolayer cell culture. Thus, the ability to isolate, culture, and maintain human brain cells from cerebral organoids is highly needed, particularly for studies on organoid-derived cell-type-specific signaling and their electrophysiological properties. Here we present a protocol to isolate and culture brain cells from 2-month human iPSC-derived cerebral organoids. The dissociation and plating of cells from organoids takes 3-4h. The dissociated cells can be maintained in culture for up to at least 3weeks. Some cells expressed the neuron-specific marker microtubule-associated protein 2 and exhibited spontaneous action potentials.

Induced Pluripotent Stem Cell Derived Human Lung Organoids to Map and Treat the SARS-CoV2 Infections In Vitro.

COVID-19 is the current day pandemic that has claimed around 1,054,604 lives globally till date. Moreover, the number of deaths is going to increase over the next few months until the pandemic comes to an end, and a second wave has also been reported in few countries. Most interestingly, the death rate among certain populations from the same COVID-19 infection is highly variable. For instance, the European populations show a very high death rate, in contrast to the populations from Chinese ethnicities. Amongst all the closed cases with an outcome (total recovered + total died), the death rate in Italy is 13%, Iran is 6%, China is 5%, Brazil is 3%, The United States of America is 2%, India 2%, Israel is 1% as of October 08, 2020. However, the percentage was higher during the early phase of the pandemic. Moreover, the global death rate amongst all the patients with an outcome is 4%. Here we have reviewed virus-transmitted various respiratory tract infections and postulated a better understanding of SARS-CoV2 using lung stem cell organoids in vitro. Hence, here we propose the strategies of understanding first the infectivity/severity ratio of COVID-19 infections using various ethnicity originated induced pluripotent stem cell-derived lung stem cell organoids in vitro. The greater the infectivity to severity ratio, the better the disease outcome with the value of 1 being the worst disease outcome. This strategy will be useful for understanding the infectivity/severity ratio of virus induced respiratory tract infections for a possible betterment of community-based disease management. Also, such a strategy will be useful for screening the effect of various antiviral drugs/repurposed drugs for their efficacy in vitro.