SARS-CoV-2 infects an in vitro model of the human developing pancreas through endocytosis

Stable expression of SARS-CoV-2 envelope viroporin promotes intracellular calcium depletion in human cells: relevance for endoplasmic reticulum stress, cell proliferation, pluripotency and lineage differentiation

SARS-CoV-2 infection affects the respiratory system but also many tissues and organs that may be adversely compromised. Accordingly, recent evidence has assessed virus ability to infect different cell phenotypes, translate viral proteins and promote virus replication. Among them, Envelope (E) proteins sustain virus replication, promote inflammatory processes and remodelling of host cells. However, despite advances on structure and sequence, E-protein specific location and effects in human host cells are still controversial and poorly investigated. Using lentiviral vectors, we established HEK293 and hiPS cell lines stably expressing E-protein. Immunocytochemistry showed E-protein mainly locates within the endoplasmic reticulum, the ERGIC and the Golgi compartments, while only HEK293 cells display some protein staining in cell periphery suggesting a possible insertion into the plasmalemma. Electrophysiological recordings in HEK293 cells revealed E-protein self-assembles in the plasma membrane to mediate a cation efflux pore that is sensitive to amantadine blockade. Calcium fluorescence imaging in HEK293 and hiPS cells demonstrated E-protein expression induces a marked depletion of thapsigargin-sensitive intracellular calcium stores. The altered calcium homeostasis associates to reduced cell metabolic activity, mitochondrial potential, proliferation rate and promotes ER stress. Finally, trilineage differentiation of hiPS cells indicated E-protein expression preserves cell pluripotency while selectively impairs mesodermal differentiation. These results unveil a critical role of stable E-viroporin expression that through alteration of ER Ca²⁺ homeostasis, metabolic activity and induction of ER stress affects important cellular functions, including the differentiative process from pluripotent to mesodermal progenitors, a critical cell population in self-repair and homeostasis of most human tissue and organs.

Cost-effective 3D lung tissue spheroid as a model for SARS-CoV-2 infection and drug screening

BACKGROUND

The SARS-CoV-2 pandemic has spurred an unparalleled scientific endeavor to elucidate the virus' structure, infection mechanisms, and pathogenesis. Two-dimensional culture systems have been instrumental in shedding light on numerous aspects of COVID-19. However, these in vitro systems lack the physiological complexity to comprehend the infection process and explore treatment options. Three-dimensional (3D) models have been proposed to fill the gap between 2D cultures and in vivo studies. Specifically, spheroids, composed of lung cell types, have been suggested for studying SARS-CoV-2 infection and serving as a drug screening platform.

METHODS

3D lung spheroids were prepared by coculturing human alveolar or bronchial epithelial cells with human lung stromal cells. The morphology, size, and ultrastructure of spheroids before and after SARS-CoV-2 infection were analyzed using optical and electron microscopy. Immunohistochemistry was used to detect spike protein and, thus, the virus presence in the spheroids. Multiplex analysis elucidated the cytokine release after virus infection.

RESULTS

The spheroids were stable and kept their size and morphology after SARS-CoV-2 infection despite the presence of multivesicular bodies, endoplasmic reticulum rearrangement, tubular compartment-enclosed vesicles, and the accumulation of viral particles. The spheroid responded to the infection releasing IL-6 and IL-8 cytokines.

CONCLUSION

This study demonstrates that coculture spheroids of epithelial and stromal cells can serve as a cost-effective infection model for the SARS-CoV-2 virus. We suggest using this 3D spheroid as a drug screening platform to explore new treatments related to the cytokines released during virus infection, especially for long COVID treatment.

Host factors of SARS-CoV-2 in infection, pathogenesis, and long-term effects

SARS-CoV-2 is the causative virus of the devastating COVID-19 pandemic that results in an unparalleled global health and economic crisis. Despite unprecedented scientific efforts and therapeutic interventions, the fight against COVID-19 continues as the rapid emergence of different SARS-CoV-2 variants of concern and the increasing challenge of long COVID-19, raising a vast demand to understand the pathomechanisms of COVID-19 and its long-term sequelae and develop therapeutic strategies beyond the virus per se. Notably, in addition to the virus itself, the replication cycle of SARS-CoV-2 and clinical severity of COVID-19 is also governed by host factors. In this review, we therefore comprehensively overview the replication cycle and pathogenesis of SARS-CoV-2 from the perspective of host factors and host-virus interactions. We sequentially outline the pathological implications of molecular interactions between host factors and SARS-CoV-2 in multi-organ and multi-system long COVID-19, and summarize current therapeutic strategies and agents targeting host factors for treating these diseases. This knowledge would be key for the identification of new pathophysiological aspects and mechanisms, and the development of actionable therapeutic targets and strategies for tackling COVID-19 and its sequelae.

FGF7 enhances the expression of ACE2 in human islet organoids aggravating SARS-CoV-2 infection

The angiotensin-converting enzyme 2 (ACE2) is a primary cell surface viral binding receptor for SARS-CoV-2, so finding new regulatory molecules to modulate ACE2 expression levels is a promising strategy against COVID-19. In the current study, we utilized islet organoids derived from human embryonic stem cells (hESCs), animal models and COVID-19 patients to discover that fibroblast growth factor 7 (FGF7) enhances ACE2 expression within the islets, facilitating SARS-CoV-2 infection and resulting in impaired insulin secretion. Using hESC-derived islet organoids, we demonstrated that FGF7 interacts with FGF receptor 2 (FGFR2) and FGFR1 to upregulate ACE2 expression predominantly in β cells. This upregulation increases both insulin secretion and susceptibility of β cells to SARS-CoV-2 infection. Inhibiting FGFR counteracts the FGF7-induced ACE2 upregulation, subsequently reducing viral infection and replication in the islets. Furthermore, retrospective clinical data revealed that diabetic patients with severe COVID-19 symptoms exhibited elevated serum FGF7 levels compared to those with mild symptoms. Finally, animal experiments indicated that SARS-CoV-2 infection increased pancreatic FGF7 levels, resulting in a reduction of insulin concentrations in situ. Taken together, our research offers a potential regulatory strategy for ACE2 by controlling FGF7, thereby protecting islets from SARS-CoV-2 infection and preventing the progression of diabetes in the context of COVID-19.

The COVID-19 Pandemic Increased the Incidence of New-Onset Type One Diabetes in Children

Background: The impact of the COVID-19 pandemic on the incidence rate of childhood type 1 diabetes (T1D) is controversial. Our aim was to analyze the incidence of new-onset T1D among children aged 0-17 before and during the COVID-19 pandemic in Israel. Methods: Data obtained from the national T1D registry for children aged 0-17 were analyzed for the pre-pandemic (1997-2019) and pandemic (2020-2022) periods. In the pre-pandemic period, 7246 children with newly diagnosed T1D were compared with 1490 children diagnosed during the pandemic period. Results: T1D incidence significantly increased in the 0-17 age group from a mean of 12.9/105 (pre-pandemic) to 17.7/105 and 16.7/105 during the first two years of the pandemic (2020 and 2021, respectively) (p = 0.0001). Stratifying by age group (0-4, 5-9, 10-14, and 15-17) revealed a significant increase in the 5-9, 10-14, and 15-17 groups, both in 2020 (p = 0.0001) and in 2021 (p = 0.0001). The incidence rate in the 0-4 age group showed no change in the first year of the pandemic (2020) (p = 0.4). However, in the second year of the pandemic (2021), there was a significant increase from 6.3/105 in the pre-pandemic period to 9.1/105 (p = 0.001). Anti-COVID-19 vaccination in 2022 led to a significant decrease in the incidence rates in the 10-14 and 15-17 age groups (p = 0.03 and p = 0.02, respectively). Conclusion: The COVID-19 pandemic was associated with a significant increase in the incidence of new-onset T1D in prepubertal and pubertal children. Anti-COVID-19 vaccination decreased the incidence rate significantly only in pubertal children.

COVID-19 and diabetes mellitus: a review of the incidence, pathophysiology and management of diabetes during the pandemic

INTRODUCTION

The COVID-19 pandemic has changed the landscape of modern medicine on a global scale. An emerging concern is the recognition of a bidirectional relationship between COVID-19 and diabetes. Diabetes is a risk factor for severe COVID-19 illness. Intriguingly, recent epidemiological and in vitro studies suggest that infection with SARS-CoV-2, the causative viral agent of COVID-19, is associated with new-onset diabetes and worsening diabetes control. These factors have affected the management of diabetes.

AREAS COVERED

This review provides an overview of our current understanding of the incidence and prevalence of diabetes in relation to the COVID-19 pandemic, highlights studies evaluating SARS-CoV-2's beta cell tropism and its effects on insulin secretion and sensitivity and evaluates the impact of the pandemic on diabetes management and metabolic control.

EXPERT OPINION

Epidemiological studies have noted an increase in the incidence of new-onset diabetes associated with COVID-19 in patients with phenotypes of type 1 diabetes, type 2 diabetes and Ketosis-Prone Diabetes. Prospective studies are needed to fully elucidate the association between COVID-19 and diabetes and to characterize persons at risk of developing diabetes after SARS-CoV-2 infection, identify those who should be screened for diabetes, and determine the natural histories of different forms of diabetes associated with COVID-19.

COVID-19 Biogenesis and Intracellular Transport

SARS-CoV-2 is responsible for the COVID-19 pandemic. The structure of SARS-CoV-2 and most of its proteins of have been deciphered. SARS-CoV-2 enters cells through the endocytic pathway and perforates the endosomes' membranes, and its (+) RNA appears in the cytosol. Then, SARS-CoV-2 starts to use the protein machines of host cells and their membranes for its biogenesis. SARS-CoV-2 generates a replication organelle in the reticulo-vesicular network of the zippered endoplasmic reticulum and double membrane vesicles. Then, viral proteins start to oligomerize and are subjected to budding within the ER exit sites, and its virions are passed through the Golgi complex, where the proteins are subjected to glycosylation and appear in post-Golgi carriers. After their fusion with the plasma membrane, glycosylated virions are secreted into the lumen of airways or (seemingly rarely) into the space between epithelial cells. This review focuses on the biology of SARS-CoV-2's interactions with cells and its transport within cells. Our analysis revealed a significant number of unclear points related to intracellular transport in SARS-CoV-2-infected cells.

Pathogenesis and Mechanisms of SARS-CoV-2 Infection in the Intestine, Liver, and Pancreas

The novel coronavirus, SARS-CoV-2, rapidly spread worldwide, causing an ongoing global pandemic. While the respiratory system is the most common site of infection, a significant number of reported cases indicate gastrointestinal (GI) involvement. GI symptoms include anorexia, abdominal pain, nausea, vomiting, and diarrhea. Although the mechanisms of GI pathogenesis are still being examined, viral components isolated from stool samples of infected patients suggest a potential fecal-oral transmission route. In addition, viral RNA has been detected in blood samples of infected patients, making hematologic dissemination of the virus a proposed route for GI involvement. Angiotensin-converting enzyme 2 (ACE2) receptors serve as the cellular entry mechanism for the virus, and these receptors are particularly abundant throughout the GI tract, making the intestine, liver, and pancreas potential extrapulmonary sites for infection and reservoirs sites for developing mutations and new variants that contribute to the uncontrolled spread of the disease and resistance to treatments. This transmission mechanism and the dysregulation of the immune system play a significant role in the profound inflammatory and coagulative cascades that contribute to the increased severity and risk of death in several COVID-19 patients. This article reviews various potential mechanisms of gastrointestinal, liver, and pancreatic injury.

Choosing a cellular model to study SARS-CoV-2

As new pathogens emerge, new challenges must be faced. This is no different in infectious disease research, where identifying the best tools available in laboratories to conduct an investigation can, at least initially, be particularly complicated. However, in the context of an emerging virus, such as SARS-CoV-2, which was recently detected in China and has become a global threat to healthcare systems, developing models of infection and pathogenesis is urgently required. Cell-based approaches are crucial to understanding coronavirus infection biology, growth kinetics, and tropism. Usually, laboratory cell lines are the first line in experimental models to study viral pathogenicity and perform assays aimed at screening antiviral compounds which are efficient at blocking the replication of emerging viruses, saving time and resources, reducing the use of experimental animals. However, determining the ideal cell type can be challenging, especially when several researchers have to adapt their studies to specific requirements. This review strives to guide scientists who are venturing into studying SARS-CoV-2 and help them choose the right cellular models. It revisits basic concepts of virology and presents the currently available in vitro models, their advantages and disadvantages, and the known consequences of each choice.