Age-specific nasal epithelial responses to SARS-CoV-2 infection

Children infected with SARS-CoV-2 rarely progress to respiratory failure. However, the risk of mortality in infected people over 85 years of age remains high. Here we investigate differences in the cellular landscape and function of paediatric (<12 years), adult (30-50 years) and older adult (>70 years) ex vivo cultured nasal epithelial cells in response to infection with SARS-CoV-2. We show that cell tropism of SARS-CoV-2, and expression of ACE2 and TMPRSS2 in nasal epithelial cell subtypes, differ between age groups. While ciliated cells are viral replication centres across all age groups, a distinct goblet inflammatory subtype emerges in infected paediatric cultures and shows high expression of interferon-stimulated genes and incomplete viral replication. In contrast, older adult cultures infected with SARS-CoV-2 show a proportional increase in basaloid-like cells, which facilitate viral spread and are associated with altered epithelial repair pathways. We confirm age-specific induction of these cell types by integrating data from in vivo COVID-19 studies and validate that our in vitro model recapitulates early epithelial responses to SARS-CoV-2 infection.

Microglial phagocytosis mediates long-term restructuring of spinal GABAergic circuits following early life injury

Peripheral injury during the early postnatal period alters the somatosensory system, leading to behavioural hyperalgesia upon re-injury in adulthood. Spinal microglia have been implicated as the cellular mediators of this phenomenon, but the mechanism is unclear. We hypothesised that neonatal injury (1) alters microglial phagocytosis of synapses in the dorsal horn leading to long-term structural changes in neurons, and/or (2) trains microglia, leading to a stronger microglial response after re-injury in adulthood. Using hindpaw surgical incision as a model we showed that microglial density and phagocytosis increased in the dorsal horn region innervated by the hindpaw. Dorsal horn microglia increased engulfment of synapses following injury, with a preference for those expressing the vesicular GABA transporter VGAT and primary afferent A-fibre terminals in neonates. This led to a long-term reduction of VGAT density in the dorsal horn and reduced microglial phagocytosis of VGLUT2 terminals. We also saw an increase in apoptosis following neonatal injury, which was not limited to the dorsal horn suggesting that larger circuit wide changes are happening. In adults, hindpaw incision increased microglial engulfment of predominantly VGAT synapses but did not alter the engulfment of A-fibres. This engulfment was not affected by prior neonatal injury, suggesting that microglial phagocytosis was not trained. These results highlight microglial phagocytosis in the dorsal horn as an important physiological response towards peripheral injury with potential long-term consequences and reveals differences in microglial responses between neonates and adults.

Role of CD14+ monocyte-derived oxidised mitochondrial DNA in the inflammatory interferon type 1 signature in juvenile dermatomyositis

OBJECTIVES

To define the host mechanisms contributing to the pathological interferon (IFN) type 1 signature in Juvenile dermatomyositis (JDM).

METHODS

RNA-sequencing was performed on CD4+, CD8+, CD14+ and CD19+ cells sorted from pretreatment and on-treatment JDM (pretreatment n=10, on-treatment n=11) and age/sex-matched child healthy-control (CHC n=4) peripheral blood mononuclear cell (PBMC). Mitochondrial morphology and superoxide were assessed by fluorescence microscopy, cellular metabolism by 13C glucose uptake assays, and oxidised mitochondrial DNA (oxmtDNA) content by dot-blot. Healthy-control PBMC and JDM pretreatment PBMC were cultured with IFN-α, oxmtDNA, cGAS-inhibitor, TLR-9 antagonist and/or n-acetyl cysteine (NAC). IFN-stimulated gene (ISGs) expression was measured by qPCR. Total numbers of patient and controls for functional experiments, JDM n=82, total CHC n=35.

RESULTS

Dysregulated mitochondrial-associated gene expression correlated with increased ISG expression in JDM CD14+ monocytes. Altered mitochondrial-associated gene expression was paralleled by altered mitochondrial biology, including 'megamitochondria', cellular metabolism and a decrease in gene expression of superoxide dismutase (SOD)1. This was associated with enhanced production of oxidised mitochondrial (oxmt)DNA. OxmtDNA induced ISG expression in healthy PBMC, which was blocked by targeting oxidative stress and intracellular nucleic acid sensing pathways. Complementary experiments showed that, under in vitro experimental conditions, targeting these pathways via the antioxidant drug NAC, TLR9 antagonist and to a lesser extent cGAS-inhibitor, suppressed ISG expression in pretreatment JDM PBMC.

CONCLUSIONS

These results describe a novel pathway where altered mitochondrial biology in JDM CD14+ monocytes lead to oxmtDNA production and stimulates ISG expression. Targeting this pathway has therapeutical potential in JDM and other IFN type 1-driven autoimmune diseases.

Trans-epithelial migration is essential for neutrophil activation during RSV infection

The recruitment of neutrophils to the infected airway occurs early following respiratory syncytial virus (RSV) infection, and high numbers of activated neutrophils in the airway and blood are associated with the development of severe disease. The aim of this study was to investigate whether trans-epithelial migration is sufficient and necessary for neutrophil activation during RSV infection. Here, we used flow cytometry and novel live-cell fluorescent microscopy to track neutrophil movement during trans-epithelial migration and measure the expression of key activation markers in a human model of RSV infection. We found that when migration occurred, neutrophil expression of CD11b, CD62L, CD64, NE, and MPO increased. However, the same increase did not occur on basolateral neutrophils when neutrophils were prevented from migrating, suggesting that activated neutrophils reverse migrate from the airway to the bloodstream side, as has been suggested by clinical observations. We then combined our findings with the temporal and spatial profiling and suggest 3 initial phases of neutrophil recruitment and behavior in the airways during RSV infection; (1) initial chemotaxis; (2) neutrophil activation and reverse migration; and (3) amplified chemotaxis and clustering, all of which occur within 20 min. This work and the novel outputs could be used to develop therapeutics and provide new insight into how neutrophil activation and a dysregulated neutrophil response to RSV mediates disease severity.

Short-Term Treatment with Rho-Associated Kinase Inhibitor Preserves Keratinocyte Stem Cell Characteristics In Vitro

Primary keratinocytes including keratinocyte stem cells (KSCs) can be cultured as epidermal sheets in vitro and are attractive for cell and gene therapies for genetic skin disorders. However, the initial slow growth of freshly isolated keratinocytes hinders clinical applications. Rho-associated kinase inhibitor (ROCKi) has been used to overcome this obstacle, but its influence on the characteristics of KSC and its safety for clinical application remains unknown. In this study, primary keratinocytes were treated with ROCKi Y-27632 for six days (short-term). Significant increases in colony formation and cell proliferation during the six-day ROCKi treatment were observed and confirmed by related protein markers and single-cell transcriptomic analysis. In addition, short-term ROCKi-treated cells maintained their differentiation ability as examined by 3D-organotypic culture. However, these changes could be reversed and became indistinguishable between treated and untreated cells once ROCKi treatment was withdrawn. Further, the short-term ROCKi treatment did not reduce the number of KSCs. In addition, AKT and ERK pathways were rapidly activated upon ROCKi treatment. In conclusion, short-term ROCKi treatment can transiently and reversibly accelerate initial primary keratinocyte expansion while preserving the holoclone-forming cell population (KSCs), providing a safe avenue for clinical applications.

Endosomal structure and APP biology are not altered in a preclinical mouse cellular model of Down syndrome

Individuals who have Down syndrome (trisomy 21) are at greatly increased risk of developing Alzheimer’s disease, characterised by the accumulation in the brain of amyloid-β plaques. Amyloid-β is a product of the processing of the amyloid precursor protein, encoded by the APP gene on chromosome 21. In Down syndrome the first site of amyloid-β accumulation is within endosomes, and changes to endosome biology occur early in Alzheimer’s disease. Here, we determine if primary mouse embryonic fibroblasts isolated from a mouse model of Down syndrome can be used to study endosome and APP cell biology. We report that in this cellular model, endosome number, size and APP processing are not altered, likely because APP is not dosage sensitive in the model, despite three copies of App.

Generation of 3D retinal tissue from human pluripotent stem cells using a directed small molecule-based serum-free microwell platform

Retinal degenerative diseases are a leading cause of blindness worldwide with debilitating life-long consequences for the affected individuals. Cell therapy is considered a potential future clinical intervention to restore and preserve sight by replacing lost photoreceptors and/or retinal pigment epithelium. Development of protocols to generate retinal tissue from human pluripotent stem cells (hPSC), reliably and at scale, can provide a platform to generate photoreceptors for cell therapy and to model retinal disease in vitro. Here, we describe an improved differentiation platform to generate retinal organoids from hPSC at scale and free from time-consuming manual microdissection steps. The scale up was achieved using an agarose mould platform enabling generation of uniform self-assembled 3D spheres from dissociated hPSC in microwells. Subsequent retinal differentiation was efficiently achieved via a stepwise differentiation protocol using a number of small molecules. To facilitate clinical translation, xeno-free approaches were developed by substituting Matrigel™ and foetal bovine serum with recombinant laminin and human platelet lysate, respectively. Generated retinal organoids exhibited important features reminiscent of retinal tissue including correct site-specific localisation of proteins involved in phototransduction.

Partial human Janus kinase 1 deficiency predominantly impairs responses to interferon gamma and intracellular control of mycobacteria

Purpose

Janus kinase-1 (JAK1) tyrosine kinase mediates signaling from multiple cytokine receptors, including interferon alpha/beta and gamma (IFN-α/β and IFN-γ), which are important for viral and mycobacterial protection respectively. We previously reported autosomal recessive (AR) hypomorphic JAK1 mutations in a patient with recurrent atypical mycobacterial infections and relatively minor viral infections. This study tests the impact of partial JAK1 deficiency on cellular responses to IFNs and pathogen control.

Methods

We investigated the role of partial JAK1 deficiency using patient cells and cell models generated with lentiviral vectors expressing shRNA.

Results

Partial JAK1 deficiency impairs IFN-γ-dependent responses in multiple cell types including THP-1 macrophages, Epstein-Barr Virus (EBV)-transformed B cells and primary dermal fibroblasts. In THP-1 myeloid cells, partial JAK1 deficiency reduced phagosome acidification and apoptosis and resulted in defective control of mycobacterial infection with enhanced intracellular survival. Although both EBV-B cells and primary dermal fibroblasts with partial JAK1 deficiency demonstrate reduced IFN-α responses, control of viral infection was impaired only in patient EBV-B cells and surprisingly intact in patient primary dermal fibroblasts.

Conclusion

Our data suggests that partial JAK1 deficiency predominantly affects susceptibility to mycobacterial infection through impact on the IFN-γ responsive pathway in myeloid cells. Susceptibility to viral infections as a result of reduced IFN-α responses is variable depending on cell type. Description of additional patients with inherited JAK1 deficiency will further clarify the spectrum of bacterial and viral susceptibility in this condition. Our results have broader relevance for anticipating infectious complications from the increasing use of selective JAK1 inhibitors.

Two-Photon Cell and Tissue Level Laser Ablation Methods to Study Morphogenetic Biomechanics

Laser ablation is routinely performed to infer mechanical tension in cells and tissues. Here we describe our method of two-photon laser ablation at the cellular and tissue level in mouse embryos. The primary outcome of these experiments is initial retraction following ablation, which correlates with, and so can be taken as a measure of, the tensile stress that structure was under before ablation. Several experimental variables can affect interpretation of ablation tests. Pre-test factors include differences in physical properties such as viscoelasticity between experimental conditions. Factors relevant during the test include viability of the cells at the point of ablation, image acquisition rate and the potential for overzealous ablations to cause air bubbles through heat dissipation. Post-test factors include intensity-biased image registration that can artificially produce apparent directionality. Applied to the closing portion of the mouse spinal neural tube, these methods have demonstrated long-range biomechanical coupling of the embryonic structure and have identified highly contractile cell populations involved in its closure process.

Higher throughput drug screening for rare respiratory diseases: readthrough therapy in primary ciliary dyskinesia

BACKGROUND

Development of therapeutic approaches for rare respiratory diseases is hampered by the lack of systems that allow medium-to-high-throughput screening of fully differentiated respiratory epithelium from affected patients. This is a particular problem for primary ciliary dyskinesia (PCD), a rare genetic disease caused by mutations in genes that adversely affect ciliary movement and consequently mucociliary transport. Primary cell culture of basal epithelial cells from nasal brush biopsies followed by ciliated differentiation at the air-liquid interface (ALI) has proven to be a useful tool in PCD diagnostics but the technique's broader utility, including in pre-clinical PCD research, has been restricted by the limited number of basal cells that can be expanded from such biopsies.

METHODS

We describe an immunofluorescence screening method, enabled by extensive expansion of basal cells from PCD patients and the directed differentiation of these cells into ciliated epithelium in miniaturised 96-well transwell format ALI cultures. As proof-of-principle, we performed a personalised investigation in a patient with a rare and severe form of PCD (reduced generation of motile cilia), in this case caused by a homozygous nonsense mutation in the MCIDAS gene.

RESULTS

Initial analyses of ciliary ultrastructure, beat pattern and beat frequency in the 96-well transwell format ALI cultures indicate that a range of different PCD defects can be retained in these cultures. The screening system in our proof-of-principal investigation allowed drugs that induce translational readthrough to be evaluated alone or in combination with nonsense-mediated decay inhibitors. We observed restoration of basal body formation but not the generation of cilia in the patient's nasal epithelial cells in vitro. CONCLUSION: Our study provides a platform for higher throughput analyses of airway epithelia that is applicable in a range of settings and suggests novel avenues for drug evaluation and development in PCD caused by nonsense mutations.

Inherited duplications of PPP2R3B predispose to nevi and melanoma via a C21orf91-driven proliferative phenotype

PURPOSE

Much of the heredity of melanoma remains unexplained. We sought predisposing germline copy-number variants using a rare disease approach.

METHODS

Whole-genome copy-number findings in patients with melanoma predisposition syndrome congenital melanocytic nevus were extrapolated to a sporadic melanoma cohort. Functional effects of duplications in PPP2R3B were investigated using immunohistochemistry, transcriptomics, and stable inducible cellular models, themselves characterized using RNAseq, quantitative real-time polymerase chain reaction (qRT-PCR), reverse phase protein arrays, immunoblotting, RNA interference, immunocytochemistry, proliferation, and migration assays.

RESULTS

We identify here a previously unreported genetic susceptibility to melanoma and melanocytic nevi, familial duplications of gene PPP2R3B. This encodes PR70, a regulatory unit of critical phosphatase PP2A. Duplications increase expression of PR70 in human nevus, and increased expression in melanoma tissue correlates with survival via a nonimmunological mechanism. PPP2R3B overexpression induces pigment cell switching toward proliferation and away from migration. Importantly, this is independent of the known microphthalmia-associated transcription factor (MITF)-controlled switch, instead driven by C21orf91. Finally, C21orf91 is demonstrated to be downstream of MITF as well as PR70.

CONCLUSION

This work confirms the power of a rare disease approach, identifying a previously unreported copy-number change predisposing to melanocytic neoplasia, and discovers C21orf91 as a potentially targetable hub in the control of phenotype switching.

Automated computational analysis reveals structural changes in the enteric nervous system of nNOS deficient mice

Neuronal nitric oxide synthase (nNOS) neurons play a fundamental role in inhibitory neurotransmission, within the enteric nervous system (ENS), and in the establishment of gut motility patterns. Clinically, loss or disruption of nNOS neurons has been shown in a range of enteric neuropathies. However, the effects of nNOS loss on the composition and structure of the ENS remain poorly understood. The aim of this study was to assess the structural and transcriptional consequences of loss of nNOS neurons within the murine ENS. Expression analysis demonstrated compensatory transcriptional upregulation of pan neuronal and inhibitory neuronal subtype targets within the Nos1-/- colon, compared to control C57BL/6J mice. Conventional confocal imaging; combined with novel machine learning approaches, and automated computational analysis, revealed increased interconnectivity within the Nos1-/- ENS, compared to age-matched control mice, with increases in network density, neural projections and neuronal branching. These findings provide the first direct evidence of structural and molecular remodelling of the ENS, upon loss of nNOS signalling. Further, we demonstrate the utility of machine learning approaches, and automated computational image analysis, in revealing previously undetected; yet potentially clinically relevant, changes in ENS structure which could provide improved understanding of pathological mechanisms across a host of enteric neuropathies.

β2-integrin LFA1 mediates airway damage following neutrophil transepithelial migration during respiratory syncytial virus infection

Respiratory syncytial virus (RSV) bronchiolitis is the most common cause of infant hospital admissions, but there is limited understanding of the mechanisms of disease, and no specific antiviral treatment. Using a novel in vitro primary transepithelial neutrophil migration model and innovative imaging methods, we show that RSV infection of nasal airway epithelium increased neutrophil transepithelial migration and adhesion to infected epithelial cells, which is associated with epithelial cell damage and reduced ciliary beat frequency, but also with a reduction in infectious viral load.Following migration, RSV infection results in greater neutrophil activation, degranulation and release of neutrophil elastase into the airway surface media compared to neutrophils that migrated across mock-infected nasal epithelial cells. Blocking of the interaction between the ligand on neutrophils (the β₂-integrin LFA-1) for intracellular adhesion molecule (ICAM)-1 on epithelial cells reduced neutrophil adherence to RSV-infected cells and epithelial cell damage to pre-infection levels, but did not reduce the numbers of neutrophils that migrated or prevent the reduction in infectious viral load.These findings have provided important insights into the contribution of neutrophils to airway damage and viral clearance, which are relevant to the pathophysiology of RSV bronchiolitis. This model is a convenient, quantitative preclinical model that will further elucidate mechanisms that drive disease severity and has utility in antiviral drug discovery.

MYCN Silencing by RNAi Induces Neurogenesis and Suppresses Proliferation in Models of Neuroblastoma with Resistance to Retinoic Acid

Neuroblastoma (NB) is the most common solid tumor in childhood. Twenty percent of patients display MYCN amplification, which indicates a very poor prognosis. MYCN is a highly specific target for an NB tumor therapy as MYCN expression is absent or very low in most normal cells, while, as a transcription factor, it regulates many essential cell activities in tumor cells. We aim to develop a therapy for NB based on MYCN silencing by short interfering RNA (siRNA) molecules, which can silence target genes by RNA interference (RNAi), a naturally occurring method of gene silencing. It has been shown previously that MYCN silencing can induce apoptosis and differentiation in MYCN amplified NB. In this article, we have demonstrated that siRNA-mediated silencing of MYCN in MYCN-amplified NB cells induced neurogenesis in NB cells, whereas retinoic acid (RA) treatment did not. RA can differentiate NB cells and is used for treatment of residual disease after surgery or chemotherapy, but resistance can develop. In addition, MYCN siRNA treatment suppressed growth in a MYCN-amplified NB cell line more than that by RA. Our result suggests that gene therapy using RNAi targeting MYCN can be a novel therapy toward MYCN-amplified NB that have complete or partial resistance toward RA.

Tissue Clearing and Deep Imaging of the Kidney Using Confocal and Two-Photon Microscopy

Microscopic and macroscopic evaluation of biological tissues in three dimensions is becoming increasingly popular. This trend is coincident with the emergence of numerous tissue clearing strategies, and advancements in confocal and two-photon microscopy, enabling the study of intact organs and systems down to cellular and sub-cellular resolution. In this chapter, we describe a wholemount immunofluorescence technique for labeling structures in renal tissue. This technique combined with solvent-based tissue clearing and confocal imaging, with or without two-photon excitation, provides greater structural information than traditional sectioning and staining alone. Given the addition of paraffin embedding to our method, this hybrid protocol offers a powerful approach to combine confocal or two-photon findings with histological and further immunofluorescent analysis within the same tissue.

Spatiotemporal dynamics and heterogeneity of renal lymphatics in mammalian development and cystic kidney disease

Heterogeneity of lymphatic vessels during embryogenesis is critical for organ-specific lymphatic function. Little is known about lymphatics in the developing kidney, despite their established roles in pathology of the mature organ. We performed three-dimensional imaging to characterize lymphatic vessel formation in the mammalian embryonic kidney at single-cell resolution. In mouse, we visually and quantitatively assessed the development of kidney lymphatic vessels, remodeling from a ring-like anastomosis under the nascent renal pelvis; a site of VEGF-C expression, to form a patent vascular plexus. We identified a heterogenous population of lymphatic endothelial cell clusters in mouse and human embryonic kidneys. Exogenous VEGF-C expanded the lymphatic population in explanted mouse embryonic kidneys. Finally, we characterized complex kidney lymphatic abnormalities in a genetic mouse model of polycystic kidney disease. Our study provides novel insights into the development of kidney lymphatic vasculature; a system which likely has fundamental roles in renal development, physiology and disease.

In most organs in the body, fluid tends to build up in the spaces between cells, especially if the organs become inflamed. Each organ has a ‘waste disposal system’; a set of specialized tubes called lymphatic vessels, to clear away this excess fluid and keep a check on inflammation. Defects in these tubes have been linked to a wide range of diseases including heart attacks, obesity, dementia and cancer.

The kidneys are responsible for filtering blood and balancing many of the body’s chemical processes. Polycystic kidney disease (PKD) is the most common genetic kidney disorder and it results in cysts filled with fluid building up in the kidney. The growth of cysts in PKD may be due to a problem with the lymphatic vessels. However, compared to other organs, how lymphatic vessels first form within the kidney and what they do is not well understood.

Now, Jafree et al. have used three-dimensional imaging to study how lymphatic vessels form in the kidneys of mice and humans. The experiments showed that lymphatic vessels first appear when mouse kidneys are about half developed, and start to grow rapidly when the kidneys are thought to begin filtering blood. Clusters of cells that may help lymphatic vessels to grow were also found hidden deep within the kidneys of mouse embryos. Treating the kidneys with a factor that stimulates the growth of lymphatic vessels increased the numbers of these clusters. Jafree et al. found similar clusters of cells in human kidneys, suggesting that lymphatic vessels in the kidneys of different mammals may develop in the same way.

Further experiments showed that the lymphatic vessels of kidneys in mice with PKD become distorted early on in the disease, when cysts are still small and before the mice develop symptoms. In the future, identifying drugs that target kidney lymphatic vessels may lead to more effective treatments for patients with PKD and other kidney diseases.

Generation and Clinical Application of Gene-Modified Autologous Epidermal Sheets in Netherton Syndrome: Lessons Learned from a Phase 1 Trial

Netherton syndrome (NS) is a rare autosomal recessive skin disorder caused by mutations in SPINK5. It is a debilitating condition with notable mortality in the early years of life. There is no curative treatment. We undertook a nonrandomized, open-label, feasibility, and safety study using autologous keratinocytes transduced with a lentiviral vector encoding SPINK5 under the control of the human involucrin promoter. Six NS subjects were recruited, and gene-modified epithelial sheets were successfully generated in three of five subjects. The sheets exhibited expression of correctly sized lympho-epithelial Kazal-type-related inhibitor (LEKTI) protein after modification. One subject was grafted with a 20 cm² gene-modified graft on the left anterior thigh without any adverse complications and was monitored by serial sampling for 12 months. Recovery within the graft area was compared against an area outside by morphology, proviral copy number and expression of the SPINK5 encoded protein, LEKTI, and its downstream target kallikrein 5, which exhibited transient functional correction. The study confirmed the feasibility of generating lentiviral gene-modified epidermal sheets for inherited skin diseases such as NS, but sustained LEKTI expression is likely to require the identification, targeting, and engraftment of long-lived keratinocyte stem cell populations for durable therapeutic effects. Important learning points for the application of gene-modified epidermal sheets are discussed.

Effective silencing of ENaC by siRNA delivered with epithelial-targeted nanocomplexes in human cystic fibrosis cells and in mouse lung

INTRODUCTION

Loss of the cystic fibrosis transmembrane conductance regulator in cystic fibrosis (CF) leads to hyperabsorption of sodium and fluid from the airway due to upregulation of the epithelial sodium channel (ENaC). Thickened mucus and depleted airway surface liquid (ASL) then lead to impaired mucociliary clearance. ENaC regulation is thus a promising target for CF therapy. Our aim was to develop siRNA nanocomplexes that mediate effective silencing of airway epithelial ENaC in vitro and in vivo with functional correction of epithelial ion and fluid transport.

METHODS

We investigated translocation of nanocomplexes through mucus and their transfection efficiency in primary CF epithelial cells grown at air-liquid interface (ALI).Short interfering RNA (SiRNA)-mediated silencing was examined by quantitative RT-PCR and western analysis of ENaC. Transepithelial potential (V_t), short circuit current (I_sc), ASL depth and ciliary beat frequency (CBF) were measured for functional analysis. Inflammation was analysed by histological analysis of normal mouse lung tissue sections.

RESULTS

Nanocomplexes translocated more rapidly than siRNA alone through mucus. Transfections of primary CF epithelial cells with nanocomplexes targeting αENaC siRNA, reduced αENaC and βENaC mRNA by 30%. Transfections reduced V_t, the amiloride-sensitive I_sc and mucus protein concentration while increasing ASL depth and CBF to normal levels. A single dose of siRNA in mouse lung silenced ENaC by approximately 30%, which persisted for at least 7 days. Three doses of siRNA increased silencing to approximately 50%.

CONCLUSION

Nanoparticle-mediated delivery of ENaCsiRNA to ALI cultures corrected aspects of the mucociliary defect in human CF cells and offers effective delivery and silencing in vivo.

Crystal structure of intraflagellar transport protein 80 reveals a homo-dimer required for ciliogenesis

Oligomeric assemblies of intraflagellar transport (IFT) particles build cilia through sequential recruitment and transport of ciliary cargo proteins within cilia. Here we present the 1.8 Å resolution crystal structure of the Chlamydomonas IFT-B protein IFT80, which reveals the architecture of two N-terminal β-propellers followed by an α-helical extension. The N-terminal β-propeller tethers IFT80 to the IFT-B complex via IFT38 whereas the second β-propeller and the C-terminal α-helical extension result in IFT80 homo-dimerization. Using CRISPR/Cas to create biallelic Ift80 frameshift mutations in IMCD3 mouse cells, we demonstrate that IFT80 is absolutely required for ciliogenesis. Structural mapping and rescue experiments reveal that human disease-causing missense mutations do not cluster within IFT80 and form functional IFT particles. Unlike missense mutant forms of IFT80, deletion of the C-terminal dimerization domain prevented rescue of ciliogenesis. Taken together our results may provide a first insight into higher order IFT complex formation likely required for IFT train formation.

Activation of podocyte Notch mediates early Wt1 glomerulopathy

The Wilms' tumor suppressor gene, WT1, encodes a zinc finger protein that regulates podocyte development and is highly expressed in mature podocytes. Mutations in the WT1 gene are associated with the development of renal failure due to the formation of scar tissue within glomeruli, the mechanisms of which are poorly understood. Here, we used a tamoxifen-based CRE-LoxP system to induce deletion of Wt1 in adult mice to investigate the mechanisms underlying evolution of glomerulosclerosis. Podocyte apoptosis was evident as early as the fourth day post-induction and increased during disease progression, supporting a role for Wt1 in mature podocyte survival. Podocyte Notch activation was evident at disease onset with upregulation of Notch1 and its transcriptional targets, including Nrarp. There was repression of podocyte FoxC2 and upregulation of Hey2 supporting a role for a Wt1/FoxC2/Notch transcriptional network in mature podocyte injury. The expression of cleaved Notch1 and HES1 proteins in podocytes of mutant mice was confirmed in early disease. Furthermore, induction of podocyte HES1 expression was associated with upregulation of genes implicated in epithelial mesenchymal transition, thereby suggesting that HES1 mediates podocyte EMT. Lastly, early pharmacological inhibition of Notch signaling ameliorated glomerular scarring and albuminuria. Thus, loss of Wt1 in mature podocytes modulates podocyte Notch activation, which could mediate early events in WT1-related glomerulosclerosis.

Vangl2 disruption alters the biomechanics of late spinal neurulation leading to spina bifida in mouse embryos

Human mutations in the planar cell polarity component VANGL2 are associated with the neural tube defect spina bifida. Homozygous Vangl2 mutation in mice prevents initiation of neural tube closure, precluding analysis of its subsequent roles in neurulation. Spinal neurulation involves rostral-to-caudal ‘zippering’ until completion of closure is imminent, when a caudal-to-rostral closure point, ‘Closure 5’, arises at the caudal-most extremity of the posterior neuropore (PNP). Here, we used Grhl3^Cre to delete Vangl2 in the surface ectoderm (SE) throughout neurulation and in an increasing proportion of PNP neuroepithelial cells at late neurulation stages. This deletion impaired PNP closure after the ∼25-somite stage and resulted in caudal spina bifida in 67% of Grhl3^Cre/+Vangl2^Fl/Fl embryos. In the dorsal SE, Vangl2 deletion diminished rostrocaudal cell body orientation, but not directional polarisation of cell divisions. In the PNP, Vangl2 disruption diminished mediolateral polarisation of apical neuroepithelial F-actin profiles and resulted in eversion of the caudal PNP. This eversion prevented elevation of the caudal PNP neural folds, which in control embryos is associated with formation of Closure 5 around the 25-somite stage. Closure 5 formation in control embryos is associated with a reduction in mechanical stress withstood at the main zippering point, as inferred from the magnitude of neural fold separation following zippering point laser ablation. This stress accommodation did not happen in Vangl2-disrupted embryos. Thus, disruption of Vangl2-dependent planar-polarised processes in the PNP neuroepithelium and SE preclude zippering point biomechanical accommodation associated with Closure 5 formation at the completion of PNP closure.

Summary: Disruption of Vangl2-dependent planar-polarised processes in the posterior neuropore (PNP) neuroepithelium and surface ectoderm preclude zippering point biomechanical accommodation associated with Closure 5 formation at the completion of PNP closure.

Wiskott-Aldrich syndrome protein regulates autophagy and inflammasome activity in innate immune cells

Dysregulation of autophagy and inflammasome activity contributes to the development of auto-inflammatory diseases. Emerging evidence highlights the importance of the actin cytoskeleton in modulating inflammatory responses. Here we show that deficiency of Wiskott-Aldrich syndrome protein (WASp), which signals to the actin cytoskeleton, modulates autophagy and inflammasome function. In a model of sterile inflammation utilizing TLR4 ligation followed by ATP or nigericin treatment, inflammasome activation is enhanced in monocytes from WAS patients and in WAS-knockout mouse dendritic cells. In ex vivo models of enteropathogenic Escherichia coli and Shigella flexneri infection, WASp deficiency causes defective bacterial clearance, excessive inflammasome activation and host cell death that are associated with dysregulated septin cage-like formation, impaired autophagic p62/LC3 recruitment and defective formation of canonical autophagosomes. Taken together, we propose that dysregulation of autophagy and inflammasome activities contribute to the autoinflammatory manifestations of WAS, thereby identifying potential targets for therapeutic intervention.

Design of a Novel Two-Component Hybrid Dermal Scaffold for the Treatment of Pressure Sores

The aim of this study is to design a novel two-component hybrid scaffold using the fibrin/alginate porous hydrogel Smart Matrix combined to a backing layer of plasma polymerized polydimethylsiloxane (Sil) membrane to make the fibrin-based dermal scaffold more robust for the treatment of the clinically challenging pressure sores. A design criteria are established, according to which the Sil membranes are punched to avoid collection of fluid underneath. Manual peel test shows that native silicone does not attach to the fibrin/alginate component while the plasma polymerized silicone membranes are firmly bound to fibrin/alginate. Structural characterization shows that the fibrin/alginate matrix is intact after the addition of the Sil membrane. By adding a Sil membrane to the original fibrin/alginate scaffold, the resulting two-component scaffolds have a significantly higher shear or storage modulus G'. In vitro cell studies show that dermal fibroblasts remain viable, proliferate, and infiltrate the two-component hybrid scaffolds during the culture period. These results show that the design of a novel two-component hybrid dermal scaffold is successful according to the proposed design criteria. To the best of the authors' knowledge, this is the first study that reports the combination of a fibrin-based scaffold with a plasma-polymerized silicone membrane.

Enhancement of mouse hematopoietic stem/progenitor cell function via transient gene delivery using integration-deficient lentiviral vectors

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Integration-deficient vectors (IdLVs) express genes transiently in dividing stem cells.

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Hematopoietic stem/progenitor cells (HSPCs) can be programmed using IdLVs.

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HOXB4 or Angptl3 expression from IdLVs improves engraftment of transplanted HSPCs.

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Short-term gene delivery avoids the side effects associated with constitutive expression.

Integration-deficient lentiviruses (IdLVs) deliver genes effectively to tissues but are lost rapidly from dividing cells. This property can be harnessed to express transgenes transiently to manipulate cell biology. Here, we demonstrate the utility of short-term gene expression to improve functional potency of hematopoietic stem and progenitor cells (HSPCs) during transplantation by delivering HOXB4 and Angptl3 using IdLVs to enhance the engraftment of HSPCs. Constitutive overexpression of either of these genes is likely to be undesirable, but the transient nature of IdLVs reduces this risk and those associated with unsolicited gene expression in daughter cells. Transient expression led to increased multilineage hematopoietic engraftment in in vivo competitive repopulation assays without the side effects reported in constitutive overexpression models. Adult stem cell fate has not been programmed previously using IdLVs, but we demonstrate that these transient gene expression tools can produce clinically relevant alterations or be applied to investigate basic biology.

Biomechanical coupling facilitates spinal neural tube closure in mouse embryos

Neural tube (NT) formation in the spinal region of the mammalian embryo involves a wave of "zippering" that passes down the elongating spinal axis, uniting the neural fold tips in the dorsal midline. Failure of this closure process leads to open spina bifida, a common cause of severe neurologic disability in humans. Here, we combined a tissue-level strain-mapping workflow with laser ablation of live-imaged mouse embryos to investigate the biomechanics of mammalian spinal closure. Ablation of the zippering point at the embryonic dorsal midline causes far-reaching, rapid separation of the elevating neural folds. Strain analysis revealed tissue expansion around the zippering point after ablation, but predominant tissue constriction in the caudal and ventral neural plate zone. This zone is biomechanically coupled to the zippering point by a supracellular F-actin network, which includes an actin cable running along the neural fold tips. Pharmacologic inhibition of F-actin or laser ablation of the cable causes neural fold separation. At the most advanced somite stages, when completion of spinal closure is imminent, the cable forms a continuous ring around the neuropore, and simultaneously, a new caudal-to-rostral zippering point arises. Laser ablation of this new closure initiation point causes neural fold separation, demonstrating its biomechanical activity. Failure of spinal closure in pre-spina bifida Zic2Ku mutant embryos is associated with altered tissue biomechanics, as indicated by greater neuropore widening after ablation. Thus, this study identifies biomechanical coupling of the entire region of active spinal neurulation in the mouse embryo as a prerequisite for successful NT closure.

Autoinflammatory periodic fever, immunodeficiency, and thrombocytopenia (PFIT) caused by mutation in actin-regulatory gene WDR1

The importance of actin dynamics in the activation of the inflammasome is becoming increasingly apparent. IL-1β, which is activated by the inflammasome, is known to be central to the pathogenesis of many monogenic autoinflammatory diseases. However, evidence from an autoinflammatory murine model indicates that IL-18, the other cytokine triggered by inflammasome activity, is important in its own right. In this model, autoinflammation was caused by mutation in the actin regulatory gene WDR1 We report a homozygous missense mutation in WDR1 in two siblings causing periodic fevers with immunodeficiency and thrombocytopenia. We found impaired actin dynamics in patient immune cells. Patients had high serum levels of IL-18, without a corresponding increase in IL-18-binding protein or IL-1β, and their cells also secreted more IL-18 but not IL-1β in culture. We found increased caspase-1 cleavage within patient monocytes indicative of increased inflammasome activity. We transfected HEK293T cells with pyrin and wild-type and mutated WDR1 Mutant protein formed aggregates that appeared to accumulate pyrin; this could potentially precipitate inflammasome assembly. We have extended the findings from the mouse model to highlight the importance of WDR1 and actin regulation in the activation of the inflammasome, and in human autoinflammation.

Autoinflammatory periodic fever, immunodeficiency, and thrombocytopenia (PFIT) caused by mutation in actin-regulatory gene WDR1

The importance of actin dynamics in the activation of the inflammasome is becoming increasingly apparent. IL-1β, which is activated by the inflammasome, is known to be central to the pathogenesis of many monogenic autoinflammatory diseases. However, evidence from an autoinflammatory murine model indicates that IL-18, the other cytokine triggered by inflammasome activity, is important in its own right. In this model, autoinflammation was caused by mutation in the actin regulatory gene WDR1 We report a homozygous missense mutation in WDR1 in two siblings causing periodic fevers with immunodeficiency and thrombocytopenia. We found impaired actin dynamics in patient immune cells. Patients had high serum levels of IL-18, without a corresponding increase in IL-18-binding protein or IL-1β, and their cells also secreted more IL-18 but not IL-1β in culture. We found increased caspase-1 cleavage within patient monocytes indicative of increased inflammasome activity. We transfected HEK293T cells with pyrin and wild-type and mutated WDR1 Mutant protein formed aggregates that appeared to accumulate pyrin; this could potentially precipitate inflammasome assembly. We have extended the findings from the mouse model to highlight the importance of WDR1 and actin regulation in the activation of the inflammasome, and in human autoinflammation.

Imaging Invasion: Micro-CT imaging of adamantinomatous craniopharyngioma highlights cell type specific spatial relationships of tissue invasion

Tissue invasion and infiltration by brain tumours poses a clinical challenge, with destruction of structures leading to morbidity. We assessed whether micro-CT could be used to map tumour invasion in adamantinomatous craniopharyngioma (ACP), and whether it could delineate ACPs and their intrinsic components from surrounding tissue.

Three anonymised archival frozen ACP samples were fixed, iodinated and imaged using a micro-CT scanner prior to the use of standard histological processing and immunohistochemical techniques.

We demonstrate that micro-CT imaging can non-destructively give detailed 3D structural information of tumours in volumes with isotropic voxel sizes of 4–6 microns, which can be correlated with traditional histology and immunohistochemistry.

Such information complements classical histology by facilitating virtual slicing of the tissue in any plane and providing unique detail of the three dimensional relationships of tissue compartments.

Regulation of neutrophil apoptosis by sodium butyrate

Neutrophils have a very short half life because they constitutively undergo apoptosis. Granulocyte-macrophage colony-stimulating factor (GM-CSF) can delay apoptosis, but this agent also primes functions such as the respiratory burst and receptor upregulation. Here, we show that sodium butyrate, which has been shown to increase gene expression and differentiation in a variety of cell types, is more effective than GM-CSF in delaying neutrophil apoptosis. Thus, sodium butyrate preserves cell morphology and function, and butyrate-treated cells express high levels of CD16 after overnight culture. However, neither GM-CSF nor sodium butyrate appear to affect mRNA levels for CD16.