Fc RECEPTOR-MEDIATED INFECTION OF MYELOID CELLS BY SARS-CoV-2

Background: The role of myeloid cells in the pathogenesis of SARS-CoV-2 is well established, in particular as drivers of cytokine production and systemic inflammation characteristic of severe COVID-19. However, the potential for myeloid cells to act as bona fide targets of productive SARS-CoV-2 infection remains unclear. Method(s): Using anti-SARS-CoV-2 mAbs with a range of neutralisation potencies and binding specificities, we performed a detailed assessment of mAb-mediated infection of monocytes/macrophages. THP-1 cells were used as a model system, with results confirmed in primary macrophages. Result(s): Infection of THP-1 cells was seen via mAbs targeting the spike RBD, but not with those targeting the NTD or S2 subunit. mAbs with the most consistent potential to mediate infection targeted a conserved region of the RBD (group 1/class IV). No infection was seen with the same quantity of virus but in the absence of antibody, and pre-treating the cells with FcgammaRI and -II blocking antibodies inhibited infection. Thus, antibody-FcR interactions are able to expand the tropism of SARS-CoV-2. Time-course studies demonstrated high-level and productive infection. Studies performed in human iPSC-derived macrophages and primary monocyte-derived macrophages paralleled results seen in THP-1 cells but with lower infection levels. Up to 2% of macrophages were infected, with infected cells appearing multinucleated and syncytial. Addition of ruxolitinib, an inhibitor of JAK1/2 signalling, increased infection up to 10-fold, indicating limitation of infection through innate immune mechanisms. Sera from primary infections (n=80) mediated rare infection events, with a minority of samples (n=3) promoting significant infection. Competition assays confirmed results seen in sera, with the addition of neutralising mAbs diminishing the infection seen with infection-mediating mAbs. Thus, the presence of antibodies with potential to mediate infection is not sufficient to predict myeloid cell infection, rather, the context in which the antibodies are produced is key. Conclusion(s): We hypothesise that a nascent antibody response during peak viral replication in primary infection presents a window of opportunity for myeloid cells to become infected, while establishment of a robust polyclonal response via vaccination or prior infection reduces the likelihood of this occurring. Infection via antibody-FcR interactions could contribute to pathogenesis in primary infection, systemic virus spread or persistent infection.

Surfactant Protein B Reduces Respiratory Viral Infectivity in Human Lungs

Purpose of Study: COVID pneumonia caused by SARS-CoV-2 can result in a depletion of surfactant & lung injury, which resembles neonatal respiratory distress syndrome. Exogenous surfactant has shown promise as a therapeutic option in intubated hospitalized patients. Our preliminary data in human lung organoids (LOs) with a deficiency of surfactant protein B (SP-B) showed an increased viral load compared to normal LOs. Single cell RNA sequencing (scRNAseq) revealed that SP-B-deficient cells showed increased viral entry genes (ACE2 receptor) & dysregulated inflammatory markers emanating from the lung cells themselves. Our objective was to determine: (1) cell-specific transcriptional differences between normal & SP-B deficient human lung cells after infection with SARS-CoV-2 and (2) a therapeutic role of SP-B protein & surfactant in COVID-19 pneumonia. Methods Used: We used normal and SP-B mutant (homozygous, frameshift, loss of function mutation p.Pro133GlnfsTer95, previously known as 121ins2) human induced pluripotent stem cells (hiPSC) and differentiated them into 3D proximal lung organoids. The organoids were infected with the delta variant of SARS-CoV-2 for 24 hours at an MOI of 1. Infected and uninfected organoids were fixed in trizol in triplicate and underwent processing for bulk RNA sequencing. We tested for differentially expressed genes using the program DEseq. We also plated normal iPSC derived lung organoids as a monolayer and pre-treated them with 1mg/ml of Poractant alfa or 5 uM of recombinant SP-B protein. The delta strain of SARS-CoV-2 was added to the 96 wells at an MOI of 0.1 for one hour with shaking, then an overlay with DMEM/CMC/FBS was added and left on for 23 hours. The plate was fixed and stained for nucleocapsid (NC) protein. Summary of Results: Bioinformatic analysis of the bulk RNA sequencing data showed an increase in the multiple cytokines and chemokines in the SP-B mutant LOs compared to control. We also saw differential gene expression patterns in the SP-B mutant LOs including a reduction in SFTPC, FOXA2, and NKX2-1 and an increase in IL1A, VEGFA, PPARG and SMAD3. In the exogenous surfactant experiments, there was a decrease in total expression of viral NC in the Poractant alfa & rSP-B-treated cells compared to SARS-CoV-2 infection alone (p<0.001). Conclusion(s): Surfactant modulates the viral load of SARS-CoV-2 infection in the human lung. Deficiency in SP-B results in the dysregulation of the lung epithelial inflammatory signaling pathways resulting in worsening infections.

Glioblastoma Susceptibility to SARS-CoV-2: Analysis of Cancer Stem Cells and Immune Tumor Microenvironment on Human Brain, Patient-Derived Tumors, and Organoid Models

INTRODUCTION: Glioblastoma (GBM) is the most common and deadliest primary brain tumor, characterized by chemoradiation resistance and an immunosuppressive tumor microenvironment (TME). SARS-CoV-2, the COVID-19 virus, produces a significant proinflammatory response and a spectrum of clinical presentations after central nervous system infection. METHOD(S): Patient-derived GBM tissue, primary cell lines, and organoids were analyzed with immunohistochemistry and pixel-line intensity quantification. Data from tumor-bulk and single-cell transcriptomics served to describe the cell-specific expression of SARS-CoV-2 receptors in GBM and its association with the immune TME phenotype. Normal brain and iPSC-derived organoids served as controls. RESULT(S): We demonstrate that patient-derivedGBMtissue and cell cultures express SARS-CoV2 entry factors such as ACE2, TMPRSS2, and NRP1. NRP1 expression was higher in GBM than in normal brains (p<0.05), where it plays a crucial role in SARS-CoV-2 infection. NRP1 was expressed in a cell-type and phenotype-specific manner and correlated with TME infiltration of immunosuppressive cells: M2 macrophages (r = 0.229), regulatory T cells (r = 0.459), NK cells (r = -0.346), and endothelial cells (r = 0.288) (p < 0.05). Furthermore, gene ontology enrichment analysis showed that leukocyte migration and chemotaxis are among the top 5 biological functions mediated by NRP1 (p < 0.05). We found our GBM organoids recapitulate tumoral expression of SARSCoV- 2 entry factors, which varies based on distance from surface as surrogate of TME oxygenation (p < 0.05). CONCLUSION(S): GBM cancer cells and immune TME cells express SARS-CoV-2 entry factors. Glioblastoma organoids recapitulate this expression and allow for currently undergoing studies analyzing the effect of SARS-CoV-2 infection in GBM. Our findings suggest that SARSCoV- 2 could potentially target GBM, opening the door to future studies evaluating SARS-CoV-2-driven immune modulation.

Microfluidic Organ-Chips and Stem Cell Models in the Fight Against COVID-19.

SARS-CoV-2, the virus underlying COVID-19, has now been recognized to cause multiorgan disease with a systemic effect on the host. To effectively combat SARS-CoV-2 and the subsequent development of COVID-19, it is critical to detect, monitor, and model viral pathogenesis. In this review, we discuss recent advancements in microfluidics, organ-on-a-chip, and human stem cell-derived models to study SARS-CoV-2 infection in the physiological organ microenvironment, together with their limitations. Microfluidic-based detection methods have greatly enhanced the rapidity, accessibility, and sensitivity of viral detection from patient samples. Engineered organ-on-a-chip models that recapitulate in vivo physiology have been developed for many organ systems to study viral pathology. Human stem cell-derived models have been utilized not only to model viral tropism and pathogenesis in a physiologically relevant context but also to screen for effective therapeutic compounds. The combination of all these platforms, along with future advancements, may aid to identify potential targets and develop novel strategies to counteract COVID-19 pathogenesis.

Human induced pluripotent stem cell-derived alveolar type 2 cells mature at air-liquid interface and respond to airborne stimuli

Human alveolar type II cells (AT2s) are progenitors of the alveolar epithelium and are among the pulmonary cells that are directly exposed to inhaled stimuli. Primary human AT2s can be cultured in three-dimensional alveolospheres, but are difficult to culture in the physiologically relevant air-liquid interface (ALI) format. Human induced pluripotent stem cells (iPSCs) can be directed to differentiate to iPSC-derived AT2s (iAT2s) in alveolospheres, where they transcriptomically resemble fetal lung. Here we report the successful adaptation of iAT2s to ALI culture, which promotes their maturation and permits exposure to inhaled stimuli. We transcriptomically profile iAT2s cultured at ALI and find that they mature as they downregulate cell cycle-associated transcripts. We then evaluate the extent of iAT2 maturation at ALI within the developmental context by comparison to primary AT2s. We find that iAT2s at ALI are more similar to primary AT2s than iAT2s cultured as spheres, and that differences are driven by primary AT2s' response to immune stimuli. We then test the capacity of iAT2s to respond to immune stimuli by infecting with SARSCoV-2. We find that iAT2s mount an epithelial-intrinsic interferon and inflammatory response to SARS-CoV-2 infection, and can serve as a platform for testing antiviral therapeutics. Finally, we demonstrate that iAT2s at ALI respond to cigarette smoke and electronic cigarette vapor, enabling the direct comparison of these common inhaled stimuli. Overall, we describe a novel disease modeling platform that will enable exploration of gene-environment interactions unique to inhaled exposures of the alveolar epithelium.

Recent updates of stem cell-based erythropoiesis.

Blood transfusions are now an essential part of modern medicine. Transfusable red blood cells (RBCs) are employed in various therapeutic strategies; however, the processes of blood donation, collection, and administration still involve many limitations. Notably, a lack of donors, the risk of transfusion-transmitted disease, and recent pandemics such as COVID-19 have prompted us to search for alternative therapeutics to replace this resource. Originally, RBC production was attempted via the ex vivo differentiation of stem cells. However, a more approachable and effective cell source is now required for broader applications. As a viable alternative, pluripotent stem cells have been actively used in recent research. In this review, we discuss the basic concepts related to erythropoiesis, as well as early research using hematopoietic stem cells ex vivo, and discuss the current trend of in vitro erythropoiesis using human-induced pluripotent stem cells.

Cardiac Neurobiology of Arrhythmia in Human Cell Models: Novel Therapeutic Targets

Heightened sympathetic drive (dysautonomia) is a hallmark of several cardiovascular diseases including SARS-CoV-2. It is also a powerful prognostic predictor for arrhythmia and sudden cardiac death, especially in patients with channelopathies (long QT syndrome-LQTS, and catecholaminergic polymorphic ventricular tachycardia-CPVT). However, little is known about the molecular targets underlying this dysautonomia. We have identified a novel pathway using a combination of single cell and bulk RNAseq, neurochemistry, FRET imaging and single cell electrophysiology. This pathway involves impairment of cyclic nucleotide coupled phosphodiesterases (PDE) linked to enhanced intracellular calcium transients and exocytosis from rat sympathetic neurons. In particular, the adaptor protein Nos1-ap, Pde2A, and Ace2 are associated with sympathetic hyperexcitability. These proteins are also conserved in human stellates from patients with LQTS and CPVT, although their role in neuronal-myocyte cellular function is unknown. We have developed a unique human iPSC sympathetic-cardiac co-culture model for target discovery in LQTS and CPVT. The lecture will highlight the use of gene manipulation of these proteins to determine their role in driving abnormal transmission and arrhythmia.

Use of cerebral organoids to model environmental and gene x environment interactions in the developing fetus and neurodegenerative disorders

The developing fetus, while generally safe from the outside world, is often exposed to any one of a number of toxins, drugs, infectious microbes, and maternal antibodies and cytokines that adversely affect the developing brain. This can have life-long consequences on cognitive function and behavior. Cerebral organoids derived from induced pluripotent stem cells (iPSCs) are used as a model system to study the first trimester brain, providing researchers with an opportunity to identify underlying molecular pathways that are disrupted by potentially dangerous environmental exposures. In addition, using patient-specific iPSCs allows researchers to study gene x environment interactions. Such studies could lead to the development of novel therapies for at-risk fetuses. © 2023 Elsevier Inc. All rights reserved.

Stimulation of the ssRNA virus immune receptor, Toll-like receptor 7, on megakaryocytes increases thrombopoesis

Background: TLR7/8 are immune receptors expressed in megakaryocytes which detects single-stranded RNA viruses such as SARS-CoV- 2. There is increasing evidence that in addition to raised platelet counts, severe infection with SARS-CoV- 2 increases the risk of venous, arterial and microvascular coagulation. Aim(s): To determine if ssRNA viruses are capable of increasing thrombopoeisis through direct interaction with megakaryocytes. Method(s): Cells were incubated with and without Gardiquimod (GDQ), a specific agonist of TLR7/8 in cord blood derived (CBMKs) and mouse bone marrow derived megakaryocytes (mMKs). TLR7/8-/- iPSC derived megakaryocytes (iPSC-MKs) were produced using CRISPR Cas9 editing of iPSCs and forward programming using an doxycyclin inducible cassette. GFP labelled SARS-CoV- 2 virus was incubated with the TLR7/8-/- iPSC- MKs and wild-type iPSC-MKs. Result(s): Incubation with GDQ increased platelet production in CBMKs and mMKs, and increased platelet function. Increased platelet counts were seen in mice treated with GDQ, and mice infected with influenza. Incubation with GDQ induced increased expression of IL1beta in the parental iPSC-MKs, however in the TLR7-/- and TLR7/8-/- MKs, no increased expression was observed. There was a significant increase in platelet production from the parental iPSC-MKs in response to incubation with GDQ, which was not seen in the TLR7-/- and TLR7/8-/- MKs. Incubation of the GFP-labelled SARS-CoV- 2 virus with wild-type MKs did not lead to a significant increase in fluorescence. Only very low level viral sequences were found in the cells post-incubation demonstrating that penetration within the MKs is unlikely to be of significance. Studies are ongoing to ascertain whether SARS-CoV- 2 induces outside in signalling leading to changes in transcription within the MKs (such as elevation of IL1beta). Conclusion(s): TLR7/8 agonists, including ssRNA genome viruses, increase platelet production and functionality from megakaryocytes. SARS-CoV- 2 does not appear to penetrate and significantly replicate within MKs, however incubation with megakaryocytes did show elevated expression of IL1beta. (Figure Presented).

Risk-Variant APOL1 Expression in iPSC-Derived Macrophages Increases Cellular Stress and Inflammation

Background: DNA variants for the APOL1 gene have been linked to a higher risk of developing kidney and cardiovascular disease in individuals with recent African ancestry. APOL1 is expressed endogenously in not only kidney cells but also immune cells such as macrophages. Recent studies show that severe acute inflammatory illness such as COVID-19 increases the likelihood of individuals with the high-risk APOL1 genotype developing glomerulopathy, raising the question of the role of immune cells in APOL1-mediated disease. Therefore, we aim to understand the cellular stress and proinflammatory pathways increased by risk variant APOL1 expression in iPSC-derived macrophages (iPSDM). Method(s): Induced pluripotent stem cell (iPSC) expressing G0 and G1 variants of APOL1 were generated through CRISPR/Cas9. Macrophages (iPSDM) were differentiated from these iPSC lines. Expression of APOL1 in the cultured iPSDMs, was induced with IFNgamma (20 ng/mL). Cytokine expression in the cell culture supernatant was measured by ELISA. Metabolic respiration was measured by Seahorse Mito Stress Test (Agilent). Result(s): Upon stimulation with IFNgamma, we observed a 4.6-fold decrease in TGF-beta secretion (n=3, p<0.001) in G1 iPSDM compared to G0. When polarized to an M1-like phenotype with IFNgamma and LPS, IL-1beta secretion was 1.4-fold increased (n=3, p<0.005) in G1 iPSDM compared to G0. G1 macrophages also had decreased levels of basal respiration compared to G0 (n=3, p=0.04). However, there was no observed difference in mitochondrial reactive oxygen species as measured by MitoSOX Red staining. Additionally, we observe a decrease in protein levels of LC3-II, an indicator of active autophagy, and a 4.4-fold increase of autophagy substrate P62 levels in G1 macrophages compared to G0. Conclusion(s): The findings in our experiments show a significant increase in inflammatory cytokine expression in G1 macrophages and decreased levels of basal respiration and autophagy markers. These results suggest that APOL1 risk variant expression modulates macrophage functions which are relevant to kidney homeostasis and disease.

Electrophysiological approaches to study cystic fibrosis transmembrane conductance regulator function from human induced pluripotent stem cell-derived airway basal cells

Background: Induced pluripotent stem cells (iPSCs), self-renewable and reprogrammed from somatic cells using different transcription factors, are considered an ideal resource for regenerative medicine to replace diseased or damaged tissues. Airway basal cells not only serve as precursors for secretory and multiciliated cells, but also contribute to maintenance and regeneration of the airway epithelial barrier. Recently, it was reported that induced basal cells (iBCs) from human iPSCs recapitulate molecular and functional features from human iPSCs of airway basal cells, including selfrenewal and multilineage differentiation [1]. iBCs as in vitro model can be used in research on diseases affecting the airway, including COVID-19, influenza, asthma, and cystic fibrosis, although despite these advantages in generating iBCs, this is insufficient to support electrophysiological evidence. Our goal in this study is to define CFTR function in iPSCderived iBCs using electrophysiological methods. Method(s): An iPSC line containing dual reporter NKX2.1GFP and TP63tdTOMATO were used to generate iBCs according to a previously published protocol [1]). iBCs were differentiated into ciliated cells using air-liquid interface (ALI) culture. Short-circuit current measurements were taken on the cells cultured in ALI culture using an Ussing chamber using a previously described protocol [2]). To measure CFTR current using electrophysiological studies, fully differentiated monolayers on filters were dissociated into single cells, which were fixed onto a collagencoated cover glass using cytospin. Whole-cell patch-clamp recordingswere performed according to a previous published protocol [3]. Result(s): We generated proximal airway iBCs from iPSCs with the dualfluorescent reporter system of green fluorescent protein (marks lung progenitors) and tdTomato (marks subsequent airway progenitor) (Figure 1a). These cells on ALI culture demonstrated CFTR function using short-circuit current measurements (Figure 1b). We also measured CFTRdependent currents in iPSC-airway basal cells using whole-cell patchclamp recording (Figure 2). Conclusion(s): We identified CFTR function in electrophysiological experiments using airway iBCs in vitro from iPSCs. Therefore, our study helps advance the field of regenerative medicine, benefiting airway and lung diseases. This may ultimately allowfor development of individual, diseasespecific airway basal stem cells, leading to drug development and a platform on which targeted drug approaches can be tested. Copyright © 2022, European Cystic Fibrosis Society. All rights reserved

Therapeutic delivery: industry update covering January 2022

This industry update covers the period from January 1 through January 31, 2022, and is based on information sourced from company press releases, scientific literature, patents and news websites. January 2022 saw Janssen and Midatech expand their collaboration on bioresorbable polymer microsphere technology for drug delivery. Takeda announced its plans to acquire UK-based Adaptate Biotherapeutics and Gandeeva raised further investment funds to support its drug discovery and development platform focused on the evaluation of protein-drug interactions. Biogen announced that it will sell its stake in a biosimilars joint venture and ABL Bio and Sanofi announced a collaboration around a novel treatment for Parkinson's disease. New regulatory announcements this month included US FDA approvals of a new insomnia treatment for Idorsia and a treatment for atopic dermatitis developed by Pfizer. Insulet gained FDA clearance for a closed-loop insulin pump and Ascendis Pharma followed up its United States approval last year for a once-weekly treatment for growth hormone deficiency with European approval. Pfizer and Ionis announced the discontinuation of the clinical development of a novel cardiovascular drug. In terms of collaborations, Novartis and Alnylam announced they will work together to explore targeted therapies to restore liver function;Scorpion Therapeutics partnered with AstraZeneca to develop novel cancer treatments and Nutriband Inc. and Kindeva Drug Delivery will work together to develop a transdermal fentanyl patch. Collaborations were also announced between Century Therapeutics and Bristol Myers Squibb and Lilly and Entos Pharmaceuticals in the areas of stem cell therapies for cancer treatment and neurology, respectively. A team from the Massachusetts Institute of Technology reported progress in developing oral mRNA treatments and West Pharmaceutical Services published a blog describing the development of a proof-of-principle system for a closed-loop feedback system targeting opioid overdose. A report on the BBC website highlighted the benefits of more sustainable inhalers.

Brain Organoids as a Model to Study Zika Virus and SARS-CoV-2 Infections

In recent years, we are living through different viral pandemics that result in neurological impairments. Given the human-specific nature of brain development, physiology, and pathology, it is imperative to use human models to investigate the neurological impact of viral infections, such as Zika virus and SARS-CoV-2. Brain organoids are powerful in vitro platforms for the analysis of the effects of viral infections on brain development and function, with prospective application to new emerging viral threats. Using brain organoids, it was possible to show that Zika virus infects neural stem cells, disrupting the cell cycle and neurogenesis, leading to microcephaly, a severe reduction of the brain. On the other hand, while it is still under investigation how SARS-CoV-2 might enter and alter the brain, organoid studies are helping to characterize its neurotropism and potential mechanisms of neurovirulence. Here, we describe a method for the infection of human brain organoid cultures with Zika and Sars-CoV-2 viruses that can be used to study neurodevelopmental phenotypes, alteration in neuronal functionality, host-pathogen interactions, as well as for drug testing. Copyright © 2023, Springer Science+Business Media, LLC, part of Springer Nature.

iPSC: SELECTION OF O-VE IPSC CLONES FOR HIGH-DENSITY RED BLOOD CELL PRODUCTION IN A SCALABLE PERFUSION BIOREACTOR SYSTEM

Background & Aim: Blood is one of the most vital resources in modern medicine. Blood transfusions have become an essential and often lifesaving procedure for accidents, during surgery, for patients with chronic disorders such as anemia, sickle cell disease, cancer, and myriad other circumstances. However, despite the rapidly growing world population, the availability of healthy blood donors is declining with aging populations. Furthermore, natural and man- made calamities often produce sudden and concentrated shocks in demand, which strains global supply chains. The COVID-19 pandemic has demonstrated this issue on a global scale by reducing the number of blood drives and donations, resulting in 39% of blood centers in the United States being left with only one- to two-day supplies, and a 50% drop of blood units collected in countries such as Zambia. Additionally, storage limitations of 42 days for donor blood limits stock availability during peak demand. Large-scale generation of universal red blood cells (RBCs) from O-ve human induced pluripotent stem cells (hiPSCs) offers the potential to alleviate blood shortages and provide a secure year-round supply. Mature iPSC-derived RBCs and reticulocytes could also find important applications in research in malaria and COVID-19 studies. (Figure Presented) Fig. 1 ( 700). Methods, Results & Conclusion: In this study, we have reprogrammed hiPSC from CD34+ O-ve cells and demonstrated the smallscale generation of high-density cultures of erythroblasts in a stirred perfusion bioreactor system. Twenty O-ve iPSC lines were derived, screened, and characterized for their ability to differentiate towards the erythroid lineage, showing high expression of mesoderm (KDR+, 64.9%), hematopoietic (CD34+/CD45+, 68.4%;CD34+/CD43+, 84.9%), and erythroid markers (CD235a+, 83,5%), and were able to undergo enucleation in vitro. Using the best clones, we were able to achieve erythroblast peak cell density of 34.7 million cells/mL with 92.2% viability in an Applikon perfusion bioreactor using an ultrasound system (Sonosep) to concentrate cells while removing waste media. This resulted in a cumulative-fold expansion of over 1,500 after 29 days of culture. Cells carried O2 effectively as demonstrated by hemoglobin dissociation curves. The perfusion culture platform paves the way for controlled high-density bioreactor culture for the generation of RBCs.

Cardio- and Neurotoxicity of Selected Anti-COVID-19 Drugs.

Since December 2019, the novel coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has infected ~435 million people and caused ~6 million related deaths as of March 2022. To combat COVID-19, there have been many attempts to repurpose FDA-approved drugs or revive old drugs. However, many of the current treatment options have been known to cause adverse drug reactions. We employed a population-based drug screening platform using 13 human leukocyte antigen (HLA) homozygous human induced pluripotent cell (iPSC) lines to assess the cardiotoxicity and neurotoxicity of the first line of anti-COVID-19 drugs. We also infected iPSC-derived cells to understand the viral infection of cardiomyocytes and neurons. We found that iPSC-derived cardiomyocytes express the ACE2 receptor which correlated with a higher infection of the SARS-CoV-2 virus (r = 0.86). However, we were unable to detect ACE2 expression in neurons which correlated with a low infection rate. We then assessed the toxicity of anti-COVID-19 drugs and identified two cardiotoxic compounds (remdesivir and arbidol) and four neurotoxic compounds (arbidol, remdesivir, hydroxychloroquine, and chloroquine). These data show that this platform can quickly and easily be employed to further our understanding of cell-specific infection and identify drug toxicity of potential treatment options helping clinicians better decide on treatment options.

USING HUMAN IPSC DERIVED INTESTINAL ORGANOIDS TO MODEL INFECTIOUS DISEASES

Human induced pluripotent stem cell (iPSC) derived intestinal organoids (HIOs) represent an inexhaustible cellular resource that could serve as a valuable tool to study viral infections such as SARS-CoV-2 as well as other enteric viruses that infect the intestinal epithelium. Intestinal symptoms of COVID-19 are present in a significant number of patients, and include nausea, diarrhea, and viral RNA shedding in feces. Using this platform we found that SARS-CoV-2 productively infects both proximally and distally patterned HIOs, leading to the release of infectious viral particles while stimulating a robust transcriptomic response, including a significant upregulation of interferon-related genes that appeared to be conserved across multiple epithelial cell types. These findings illuminate a potential inflammatory epithelial-specific signature that may contribute to both the multisystemic nature of COVID- 19 as well as its highly variable clinical presentation. We are now expanding our studies to investigate the role of Ebola virus infection in intestinal epithelial injury.

Modified mRNA delivery to the heart using Lipid Nanoparticles

Myocardial infarction is a global health burden for which there is no treatment available that aims to recover the damaged tissue after the ischemic event. Lipid nanoparticles (LNPs) represent a well characterized class of mRNA delivery systems, which were recently approved for clinical usage in their application for mRNA-based covid-19 vaccines. After myocardial infarction, endogenous mechanisms that enable repair of the functional damaged tissue can be triggered by modified mRNA (modRNA) delivery, locally in the infarcted area. As a first step, in order to optimize the LNP formulation for effective myocardial delivery and study cellular tropism of the LNPs in the heart, different LNPs formulations will be evaluated as delivery systems in a murine healthy heart model. Different LNP formulations varying in type and amount of helper lipid were used as delivery systems for modRNA encoding the reporter genes luciferase or eGFP. In vitro, LNPs were evaluated for modRNA delivery in a human endothelial cell line (HMEC-1), induced pluripotent stem cell-derived cardiomyocytes (iPS-CMs) and induced pluripotent stem cell -derived fibroblasts (iPS-FBs). In vivo, modRNA delivery was evaluated in C57BL-6 mice, undergoing open chest heart surgery under general anaesthesia in order to infuse LNPs into the left ventricular wall. For determination of luciferase expression levels, animals were infused with luciferin substrate intraperitoneally 24 hrs after injection. Heart, liver, lungs, spleen and kidneys were extracted for imaging in a bioluminescence imaging system. The organs were then stored in liquid nitrogen for further ex-vivo modRNA delivery analysis. For determining cellular tropism, histology was performed on mice treated with eGFP modRNA. Both bioluminescence imaging and luminescence analysis in tissue lysates showed that mRNA transfection is achieved in the myocardium 24 hours after LNP intramyocardial administration. However, all LNP formulations also resulted in high expression levels in other organs, including liver and spleen. Changes in type or amount of helper lipid in LNPs strongly affected transfection levels. Histology of the treated hearts revealed a distinct transfection pattern. The targeted, interstitial cells were negative for CD31 (marker for endothelial cells and monocytes) and Troponin I3 (marker for cardiomyocytes) (Figure 1). We show that, using an optimized LNP formulation, a significant degree of modRNA local transfection of the heart can be achieved. However, despite the local route of administration (into the left ventricular wall), the highest LNP transfection is shown in remote organs such as liver and spleen. More improvements of the LNP formulations must be done to increase their tropism towards the heart tissue for their optimization as cardiac delivery systems. Determining which cell types are being targeted is also important in order to establish a therapeutic target when applying the LNPs for cardiac therapy. (Figure Presented).

A combined molecular and electrophysiological approach to understand the effect of interleukin 6 in cardiac myocytes

Background and purpose: Increased inflammatory cytokines, including interleukin 6 (IL-6), are associated to enhanced arrhythmogenic risk, including atrial fibrillation [1]. Moreover, direct effects of cytokines on ion channels are emerging as important mediators of arrhythmogenic remodeling [2]. In line with this, enhanced arrhythmogenesis in COVID-19 patients is hypothesized to be driven by cytokine storms, a well demonstrated condition in this setting [3]. To dissect the underlying mechanisms explaining such an association, we evaluated the proarrhythmogenic alterations of IL-6, assessing the impact on the expression of Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels, of the regulatory subunits MiRP1, and on the action potential (AP) profile in HL-1 cardiomyocytes (CMs). In human left atrial samples we studied the relation occurring between the expression levels of IL-6 and of HCN channels. In human induced pluripotent stem cell (hiPSC)-derived CMs we evaluated the acute effects of IL-6 on pacemaker activity. Methods: HL-1 CMs exposed to 50 ng/ml IL-6 or vehicle were collected after 0, 0.5, 6, 12, 24 and 48 h to study intracellular signaling, ion channel expression and AP profile. The latter was assessed through a high-throughput system allowing optical detection of APs with optical stimulation. In human atrial samples obtained from patients undergoing surgery, IL-6 and HCN mRNA expression were analyzed by quantitative RT-PCR. The acute effects on pacemaker activity were evaluated in hiPSC-derived CMs exposed to increasing concentrations of IL-6. Results: In HL1 CMs IL-6 rapidly induces STAT3 phosphorylation, demonstrating the activation of IL-6 signaling cascade. IL-6 modifies HCN channel transcript and proteins at different time points, evidencing a significant downregulation of HCN4 isoform and significant upregulations of HCN1, HCN2 and MiRP1. In line with this, in human left atrial samples, expression levels of IL-6 were linearly and directly related to HCN1 channel, while they were linearly and inversely related to HCN4. Electrophysiological recordings on HL-1 CMs showed a decreasing trend of AP amplitude and of maximum diastolic potential, while AP durations tended to increase. In hiPSC-derived CMs IL-6 reduces the frequency of AP in a concentration-dependent manner. Conclusions: Our data demonstrate that in HL-1 CMs IL-6 activates a STAT3 dependent intracellular signaling that is associated to subsequent variation of HCN channel expression and a concurrent alteration of AP profile. The relation between IL-6 and HCN1,4 expression in human samples suggests a mechanistic link between IL-6 levels and ionic channel targets, including HCN channels. The reduction of AP frequency in hiPSC-derived CMs suggests a direct interaction with ion channels. We hypothesize that these modifications may lay the basis to enhance the propensity of atria to develop arrhythmias in condition of elevate IL-6 levels.