ARL5b inhibits human rhinovirus 16 propagation and impairs macrophage-mediated bacterial clearance

Human rhinovirus is the most frequently isolated virus during severe exacerbations of chronic respiratory diseases, like chronic obstructive pulmonary disease. In this disease, alveolar macrophages display significantly diminished phagocytic functions that could be associated with bacterial superinfections. However, how human rhinovirus affects the functions of macrophages is largely unknown. Macrophages treated with HRV16 demonstrate deficient bacteria-killing activity, impaired phagolysosome biogenesis, and altered intracellular compartments. Using RNA sequencing, we identify the small GTPase ARL5b to be upregulated by the virus in primary human macrophages. Importantly, depletion of ARL5b rescues bacterial clearance and localization of endosomal markers in macrophages upon HRV16 exposure. In permissive cells, depletion of ARL5b increases the secretion of HRV16 virions. Thus, we identify ARL5b as a novel regulator of intracellular trafficking dynamics and phagolysosomal biogenesis in macrophages and as a restriction factor of HRV16 in permissive cells.

Successful 3D imaging of cleared biological samples with light sheet fluorescence microscopy

In parallel with the development of tissue-clearing methods, over the last decade, light sheet fluorescence microscopy has contributed to major advances in various fields, such as cell and developmental biology and neuroscience. While biologists are increasingly integrating three-dimensional imaging into their research projects, their experience with the technique is not always up to their expectations. In response to a survey of specific challenges associated with sample clearing and labeling, image acquisition, and data analysis, we have critically assessed the recent literature to characterize the difficulties inherent to light sheet fluorescence microscopy applied to cleared biological samples and to propose solutions to overcome them. This review aims to provide biologists interested in light sheet fluorescence microscopy with a primer for the development of their imaging pipeline, from sample preparation to image analysis. Importantly, we believe that issues could be avoided with better anticipation of image analysis requirements, which should be kept in mind while optimizing sample preparation and acquisition parameters.

Acute stress induces long-term metabolic, functional, and structural remodeling of the heart

Takotsubo cardiomyopathy is a stress-induced cardiovascular disease with symptoms comparable to those of an acute coronary syndrome but without coronary obstruction. Takotsubo was initially considered spontaneously reversible, but epidemiological studies revealed significant long-term morbidity and mortality, the reason for which is unknown. Here, we show in a female rodent model that a single pharmacological challenge creates a stress-induced cardiomyopathy similar to Takotsubo. The acute response involves changes in blood and tissue biomarkers and in cardiac in vivo imaging acquired with ultrasound, magnetic resonance and positron emission tomography. Longitudinal follow up using in vivo imaging, histochemistry, protein and proteomics analyses evidences a continued metabolic reprogramming of the heart towards metabolic malfunction, eventually leading to irreversible damage in cardiac function and structure. The results combat the supposed reversibility of Takotsubo, point to dysregulation of glucose metabolic pathways as a main cause of long-term cardiac disease and support early therapeutic management of Takotsubo.

Implantation of engineered human microvasculature to study human infectious diseases in mouse models

Animal models for studying human pathogens are crucially lacking. We describe the implantation in mice of engineered human mature microvasculature consisting of endothelial and perivascular cells embedded in collagen hydrogel that allows investigation of pathogen interactions with the endothelium, including in vivo functional studies. Using Neisseria meningitidis as a paradigm of human-restricted infection, we demonstrated the strength and opportunities associated with the use of this approach.

Quality assessment in light microscopy for routine use through simple tools and robust metrics

Although there is a need to demonstrate reproducibility in light microscopy acquisitions, the lack of standardized guidelines monitoring microscope health status over time has so far impaired the widespread use of quality control (QC) measurements. As scientists from 10 imaging core facilities who encounter various types of projects, we provide affordable hardware and open source software tools, rigorous protocols, and define reference values to assess QC metrics for the most common fluorescence light microscopy modalities. Seven protocols specify metrics on the microscope resolution, field illumination flatness, chromatic aberrations, illumination power stability, stage drift, positioning repeatability, and spatial-temporal noise of camera sensors. We designed the MetroloJ_QC ImageJ/Fiji Java plugin to incorporate the metrics and automate analysis. Measurements allow us to propose an extensive characterization of the QC procedures that can be used by any seasoned microscope user, from research biologists with a specialized interest in fluorescence light microscopy through to core facility staff, to ensure reproducible and quantifiable microscopy results.

Cyclic fertilin-derived peptide stimulates in vitro human embryo development

OBJECTIVE

To study the cyclic fertilin peptide effects on preimplantation human embryogenesis. Cyclic fertilin peptide reproduces the structure of the binding site of the sperm Fertilin β (also named A Disintegrin and Metalloprotease 2: ADAM2) disintegrin domain. It binds to the oocyte membrane and increases sperm-oocyte fusion index in human and fertilization rate in mouse, providing healthy pups. It also improves human oocyte maturation and chromosome segregation in meiosis I and binds to human embryo blastomeres, suggesting that it has a membrane receptor.

DESIGN

Thawed human embryos at the 3 to 4 cells stage were randomly included in a dose-response study with cyclic fertilin peptide. Inner cell mass (ICM), trophectoderm (TE), and total cell numbers were evaluated in top- and good-quality blastocysts.

SETTING

The study was performed in an academic hospital and research laboratory.

PATIENT(S)

Human embryos donated for research. This project was approved by the French "Agence de la Biomédecine."

INTERVENTION(S)

Immunofluorescence and tissue-specific gene expression analysis, using Clariom D microarrays, were performed to study its mechanism of action.

MAIN OUTCOME MEASURE(S)

Cyclic fertilin peptide improves blastocyst formation by almost 20%, the concentration of 1 μM being the lowest most efficient concentration. It significantly increases twice the TE cell number, without modifying the ICM. It increases the in vitro hatching rate from 14% to 45%.

RESULT(S)

Cyclic fertilin peptide stimulates TE growth. In the ICM, it induces transcriptional activation of intracellular protein and vesicle-mediated transport.

CONCLUSION(S)

Cyclic fertilin peptide dramatically improves human embryo development potential. It could be used to supplement culture medium and improve the in vitro human embryo development. Starting supplementation immediately after fertilization, instead of day 2, could significantly upgrade assisted reproductive technology outcome.

Cyclic FEE Peptide Improves Human Sperm Movement Parameters without Modification of Their Energy Metabolism

Cyclic fertilin peptide (cFEE: phenylalanine, glutamic acid; glutamic acid) improves gamete interaction in humans. We investigate whether it could be via improvement of sperm movement parameters and their mitochondrial ATP production. Sperm movement parameters were studied using computer-assisted sperm analysis (CASA) in sperm samples from 38 patients with normal sperm in medium supplemented with cyclic fertilin against a control group. Sperm mitochondrial functions were studied using donor’s sperm, incubated or not with cFEE. It was evaluated by the measurement of their ATP production using bioluminescence, their respiration by high resolution oxygraphy, and of mitochondrial membrane potential (MMP) using potentiometric dyes and flow cytometry. cFEE significantly improved sperm movement parameters and percentage of hyperactivated sperm. Impact of inhibitors showed OXPHOS as the predominant energy source for sperm movement. However, cFEE had no significant impact on any of the analyzed mitochondrial bioenergetic parameters, suggesting that it could act via a more efficient use of its energy resources.

QUAREP-LiMi: A community-driven initiative to establish guidelines for quality assessment and reproducibility for instruments and images in light microscopy

A modern day light microscope has evolved from a tool devoted to making primarily empirical observations to what is now a sophisticated , quantitative device that is an integral part of both physical and life science research. Nowadays, microscopes are found in nearly every experimental laboratory. However, despite their prevalent use in capturing and quantifying scientific phenomena, neither a thorough understanding of the principles underlying quantitative imaging techniques nor appropriate knowledge of how to calibrate, operate and maintain microscopes can be taken for granted. This is clearly demonstrated by the well-documented and widespread difficulties that are routinely encountered in evaluating acquired data and reproducing scientific experiments. Indeed, studies have shown that more than 70% of researchers have tried and failed to repeat another scientist's experiments, while more than half have even failed to reproduce their own experiments. One factor behind the reproducibility crisis of experiments published in scientific journals is the frequent underreporting of imaging methods caused by a lack of awareness and/or a lack of knowledge of the applied technique. Whereas quality control procedures for some methods used in biomedical research, such as genomics (e.g. DNA sequencing, RNA-seq) or cytometry, have been introduced (e.g. ENCODE), this issue has not been tackled for optical microscopy instrumentation and images. Although many calibration standards and protocols have been published, there is a lack of awareness and agreement on common standards and guidelines for quality assessment and reproducibility. In April 2020, the QUality Assessment and REProducibility for instruments and images in Light Microscopy (QUAREP-LiMi) initiative was formed. This initiative comprises imaging scientists from academia and industry who share a common interest in achieving a better understanding of the performance and limitations of microscopes and improved quality control (QC) in light microscopy. The ultimate goal of the QUAREP-LiMi initiative is to establish a set of common QC standards, guidelines, metadata models and tools, including detailed protocols, with the ultimate aim of improving reproducible advances in scientific research. This White Paper (1) summarizes the major obstacles identified in the field that motivated the launch of the QUAREP-LiMi initiative; (2) identifies the urgent need to address these obstacles in a grassroots manner, through a community of stakeholders including, researchers, imaging scientists, bioimage analysts, bioimage informatics developers, corporate partners, funding agencies, standards organizations, scientific publishers and observers of such; (3) outlines the current actions of the QUAREP-LiMi initiative and (4) proposes future steps that can be taken to improve the dissemination and acceptance of the proposed guidelines to manage QC. To summarize, the principal goal of the QUAREP-LiMi initiative is to improve the overall quality and reproducibility of light microscope image data by introducing broadly accepted standard practices and accurately captured image data metrics.

A neural crest cell isotropic-to-nematic phase transition in the developing mammalian gut

While the colonization of the embryonic gut by neural crest cells has been the subject of intense scrutiny over the past decades, we are only starting to grasp the morphogenetic transformations of the enteric nervous system happening in the fetal stage. Here, we show that enteric neural crest cell transit during fetal development from an isotropic cell network to a square grid comprised of circumferentially-oriented cell bodies and longitudinally-extending interganglionic fibers. We present ex-vivo dynamic time-lapse imaging of this isotropic-to-nematic phase transition and show that it occurs concomitantly with circular smooth muscle differentiation in all regions of the gastrointestinal tract. Using conditional mutant embryos with enteric neural crest cells depleted of β1-integrins, we show that cell-extracellular matrix anchorage is necessary for ganglia to properly reorient. We demonstrate by whole mount second harmonic generation imaging that fibrous, circularly-spun collagen I fibers are in direct contact with neural crest cells during the orientation transition, providing an ideal orientation template. We conclude that smooth-muscle associated extracellular matrix drives a critical reorientation transition of the enteric nervous system in the mammalian fetus.

Tumor stiffening reversion through collagen crosslinking inhibition improves T cell migration and anti-PD-1 treatment

Only a fraction of cancer patients benefits from immune checkpoint inhibitors. This may be partly due to the dense extracellular matrix (ECM) that forms a barrier for T cells. Comparing five preclinical mouse tumor models with heterogeneous tumor microenvironments, we aimed to relate the rate of tumor stiffening with the remodeling of ECM architecture and to determine how these features affect intratumoral T cell migration. An ECM-targeted strategy, based on the inhibition of lysyl oxidase, was used. In vivo stiffness measurements were found to be strongly correlated with tumor growth and ECM crosslinking but negatively correlated with T cell migration. Interfering with collagen stabilization reduces ECM content and tumor stiffness leading to improved T cell migration and increased efficacy of anti-PD-1 blockade. This study highlights the rationale of mechanical characterizations in solid tumors to understand resistance to immunotherapy and of combining treatment strategies targeting the ECM with anti-PD-1 therapy.

3D-printed protected face shields for health care workers in Covid-19 pandemic

The coronavirus pandemic resulted in a shortage of protective equipment. To meet the request of eye-protecting devices, an interdisciplinary consortium involving practitioners, researchers, engineers and technicians developed and manufactured thousands of inexpensive 3D-printed face shields, inside hospital setting. This action leads to the concept of "concurrent, agile, and rapid engineering".

Streptococcus pyogenes infects human endometrium by limiting the innate immune response

Group A Streptococcus (GAS), a Gram-positive human-specific pathogen, yields 517,000 deaths annually worldwide, including 163,000 due to invasive infections and among them puerperal fever. Before efficient prophylactic measures were introduced, the mortality rate for mothers during childbirth was approximately 10%; puerperal fever still accounts for over 75,000 maternal deaths annually. Yet, little is known regarding the factors and mechanisms of GAS invasion and establishment in postpartum infection. We characterized the early steps of infection in an ex vivo infection model of the human decidua, the puerperal fever portal of entry. Coordinate analysis of GAS behavior and the immune response led us to demonstrate that (a) GAS growth was stimulated by tissue products; (b) GAS invaded tissue and killed approximately 50% of host cells within 2 hours, and these processes required SpeB protease and streptolysin O (SLO) activities, respectively; and (c) GAS impaired the tissue immune response. Immune impairment occurred both at the RNA level, with only partial induction of the innate immune response, and protein level, in an SLO- and SpeB-dependent manner. Our study indicates that efficient GAS invasion of the decidua and the restricted host immune response favored its propensity to develop rapid invasive infections in a gynecological-obstetrical context.

Selective Laser Melted Titanium Alloy for Transgingival Components: Influence of Surface Condition on Fibroblast Cell Behavior

PURPOSE

To mechanically characterize and assess the biological properties of Ti6Al4V surfaces obtained by Selective Laser Melting in order to determine whether this process is conceivable for production of implant-supported prostheses and particularly trans-gingival components. As-built and polished surfaces were studied in comparison with components obtained by computer numerical control machining technology in order to consider whether the properties are in the same range as the conventional method currently used.

MATERIALS AND METHODS

Cylindrical specimens of Ti6Al4V (n = 6) were built with Selective Laser Melting for the characterization of mechanical properties according to ISO 22674 and discs (n = 12) were fabricated in the same conditions for cytotoxicity evaluation. Discs (n = 12) of Ti6Al4V were also obtained by computer numerical control machining as control. Half of the number of discs (n = 6) from each process were polished, to simulate the laboratory protocol for polishing of transmucosal components and half of the discs remained unaltered (as-built). Surface roughness measurements of disc specimens (as-built and polished) were compared with computer numerical control milling specimens (as-built and polished). Proliferation of human gingival fibroblasts on Ti6Al4V surfaces was also assessed for each condition. Viability and cell morphology were then evaluated qualitatively. Ra and Sa data were compared using Student's t-test (α = 0.05) and metabolic activity data were compared using Kruskal-Wallis statistical test (α = 0.05).

RESULTS

Selective Laser Melting specimens showed elongation at break greater than 2% and 0.2% yield strength better than 500MPa which complied with ISO 22674 standards. Although Selective Laser Melting samples displayed significantly increased roughness on as-built surfaces compared to computer numerically controlled milling samples (p < 0.05), no statistically significant difference was observed after mechanical polishing (p = 0.279). Regarding metabolic activity, no statistical difference was observed between groups at day 3 (p > 0.05) and fibroblasts showed a viability higher than 97% on all discs. Cell shapes on polished samples suggested moderate adhesion compared to unpolished samples.

CONCLUSION

With the manufacturing parameters selected in this study, Selective Laser Melting of Ti6Al4V appeared to be compatible with a prosthetic application type 4 according to ISO 22674. Surfaces obtained, followed by recommended postprocessing provided components with equivalent biological properties compared to computer numerical control machining technology.

Micro-Meta App: an interactive tool for collecting microscopy metadata based on community specifications

For quality, interpretation, reproducibility and sharing value, microscopy images should be accompanied by detailed descriptions of the conditions that were used to produce them. Micro-Meta App is an intuitive, highly interoperable, open-source software tool that was developed in the context of the 4D Nucleome (4DN) consortium and is designed to facilitate the extraction and collection of relevant microscopy metadata as specified by the recent 4DN-BINA-OME tiered-system of Microscopy Metadata specifications. In addition to substantially lowering the burden of quality assurance, the visual nature of Micro-Meta App makes it particularly suited for training purposes.

Physical plasma therapy accelerates wound re-epithelialisation and enhances extracellular matrix formation in cutaneous skin grafts

Skin grafting is a surgical method of cutaneous reconstruction, which provides volumetric replacement in wounds unable to heal by primary intention. Clinically, full-thickness skin grafts (FTSGs) are placed in aesthetically sensitive and mechanically demanding areas such as the hands, face, and neck. Complete or partial graft failure is the primary complication associated with this surgical procedure. Strategies aimed at improving the rate of skin graft integration will reduce the incidence of graft failure. Cold atmospheric plasma (CAP) is an emerging technology offering innovative clinical applications. The aim of this study was to test the therapeutic potential of CAP to improve wound healing and skin graft integration into the recipient site. In vitro models that mimic wound healing were used to investigate the ability of CAP to enhance cellular migration, a key factor in cutaneous tissue repair. We demonstrated that CAP enhanced the migration of epidermal keratinocytes and dermal fibroblasts. This increased cellular migration was possibly induced by the low dose of reactive oxygen and nitrogen species produced by CAP. Using a mouse model of burn wound reconstructed with a full-thickness skin graft, we showed that wounds treated with CAP healed faster than did control wounds. Immunohistochemical wound analysis showed that CAP treatment enhanced the expression of the dermal-epidermal junction components, which are vital for successful skin graft integration. CAP treatment was characterised by increased levels of Tgfbr1 mRNA and collagen I protein in vivo, suggesting enhanced wound maturity and extracellular matrix deposition. Mechanistically, we show that CAP induced the activation of the canonical SMAD-dependent TGF-β1 pathway in primary human dermal fibroblasts, which may explain the increased collagen I synthesis in vitro. These studies revealed that CAP improved wound repair and skin graft integration via mechanisms involving extracellular matrix formation. CAP offers a novel approach for treating cutaneous wounds and skin grafts. © 2020 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Extracellular Release of Antigen by Dendritic Cell Regurgitation Promotes B Cell Activation through NF-κB/cRel

Dendritic cells (DCs) are professional APCs, which sample Ags in the periphery and migrate to the lymph node where they activate T cells. DCs can also present native Ag to B cells through interactions observed both in vitro and in vivo. However, the mechanisms of Ag transfer and B cell activation by DCs remain incompletely understood. In this study, we report that murine DCs are an important cell transporter of Ag from the periphery to the lymph node B cell zone and also potent inducers of B cell activation both in vivo and in vitro. Importantly, we highlight a novel extracellular mechanism of B cell activation by DCs. In this study, we demonstrate that Ag released upon DC regurgitation is sufficient to efficiently induce early B cell activation, which is BCR driven and mechanistically dependent on the nuclear accumulation of the transcription factor NF-κB/cRel. Thus, our study provides new mechanistic insights into Ag delivery and B cell activation modalities by DCs and a promising approach for targeting NF-κB/cRel pathway to modulate the DC-elicited B cell responses.

Polyploidy spectrum: a new marker in HCC classification

OBJECTIVES

Polyploidy is a fascinating characteristic of liver parenchyma. Hepatocyte polyploidy depends on the DNA content of each nucleus (nuclear ploidy) and the number of nuclei per cell (cellular ploidy). Which role can be assigned to polyploidy during human hepatocellular carcinoma (HCC) development is still an open question. Here, we investigated whether a specific ploidy spectrum is associated with clinical and molecular features of HCC.

DESIGN

Ploidy spectra were determined on surgically resected tissues from patients with HCC as well as healthy control tissues. To define ploidy profiles, a quantitative and qualitative in situ imaging approach was used on paraffin tissue liver sections.

RESULTS

We first demonstrated that polyploid hepatocytes are the major components of human liver parenchyma, polyploidy being mainly cellular (binuclear hepatocytes). Across liver lobules, polyploid hepatocytes do not exhibit a specific zonation pattern. During liver tumorigenesis, cellular ploidy is drastically reduced; binuclear polyploid hepatocytes are barely present in HCC tumours. Remarkably, nuclear ploidy is specifically amplified in HCC tumours. In fact, nuclear ploidy is amplified in HCCs harbouring a low degree of differentiation and TP53 mutations. Finally, our results demonstrated that highly polyploid tumours are associated with a poor prognosis.

CONCLUSIONS

Our results underline the importance of quantification of cellular and nuclear ploidy spectra during HCC tumorigenesis.

Macrophage Migration Inhibitory Factor (MIF) Inhibition in a Murine Model of Bleomycin-Induced Pulmonary Fibrosis

Background: Pulmonary hypertension (PH) is a common complication of idiopathic pulmonary fibrosis (IPF) that significantly contributes to morbidity and mortality. Macrophage migration inhibitory factor (MIF) is a critical factor in vascular remodeling of the pulmonary circulation. Objectives: We tested the effects of two small molecules targeting MIF on bleomycin (BLM)-induced collagen deposition, PH, and vascular remodeling in mouse lungs. Methods: We examined the distribution pattern of MIF, CD74, and CXCR4 in the lungs of patients with IPF-PH and the lungs of BLM-injected mice. Then, treatments were realized with (S,R)-3-(4-hydroxyphenyl)-4,5-dihydro-5-isoxazole acetic acid methyl ester (ISO-1) and N-(3-hydroxy-4-fluorobenzyl)-5 trifluoromethylbenzoxazol-2-thione 31 (20 mg/kg/day per os for 3 weeks) started 24 h after an intratracheal BLM administration. Results: More intense immunoreactivity was noted for MIF, CD74, and CXCR4 in lungs from IPF-PH patients and BLM-injected mice. Furthermore, we found that treatments of BLM-injected mice with ISO-1 or compound 31 attenuated lung collagen deposition and right ventricular systolic pressure increase. Additionally, reduced pulmonary inflammatory infiltration and pulmonary arterial muscularization were observed in the lungs of BLM-injected mice treated with ISO-1 or compound 31. Conclusions: Treatments with ISO-1 or compound 31 attenuates BLM-induced inflammation and fibrosis in lung, and prevents PH development in mice, suggesting that MIF is an important factor for IPF-PH development.

Calcium-mediated shaping of naive CD4 T-cell phenotype and function

Continuous contact with self-major histocompatibility complex ligands is essential for the survival of naive CD4 T cells. We have previously shown that the resulting tonic TCR signaling also influences their fate upon activation by increasing their ability to differentiate into induced/peripheral regulatory T cells. To decipher the molecular mechanisms governing this process, we here focus on the TCR signaling cascade and demonstrate that a rise in intracellular calcium levels is sufficient to modulate the phenotype of mouse naive CD4 T cells and to increase their sensitivity to regulatory T-cell polarization signals, both processes relying on calcineurin activation. Accordingly, in vivo calcineurin inhibition leads the most self-reactive naive CD4 T cells to adopt the phenotype of their less self-reactive cell-counterparts. Collectively, our findings demonstrate that calcium-mediated activation of the calcineurin pathway acts as a rheostat to shape both the phenotype and effector potential of naive CD4 T cells in the steady-state.

To help protect the body from disease, small immune cells called T lymphocytes move rapidly, searching for signs of infection. These signs are antigens – processed pieces of proteins from invading microbes – that are displayed on the surface of so-called antigen-presenting cells.Before it encounters its specific antigen, a T cell is called naive. After encountering its antigen, the naive T cell activates and then develops into a variety of immune cells, each with a specific activity. These immune cells include so-called peripherally induced regulatory T cells (or “pTreg cells” for short), which, as the name suggests, help to regulate the immune response.

In addition to foreign antigens from microbes, antigen-presenting cells display fragments of the body’s own proteins too. All naive T cells recognize some “Self-antigens”, but not as strongly as they recognize foreign antigens. As a naive T cell travels around the body, it repeatedly interacts with antigen-presenting cells that display Self-antigens, which triggers a low level of signaling in the T cell. While this background signaling was known to help the T cell survive, in 2013, researchers reported that: it also makes the T cell more responsive to foreign antigens; and it shapes how these cells will respond when activated. For example, the naive T cells that respond the most to Self-antigens were seen to be much more likely to become pTreg cells when activated than other T cells.

Guichard et al. – who include several of the researchers involved in the 2013 work – set out to understand why the most Self-reactive T cells show this bias toward becoming pTreg cells. The experiments used a range of approaches with T cells both in the laboratory and in mice. By looking at which genes were active in the most Self-reactive T cells, Guichard et al. narrowed in on a signaling pathway that involves calcium ions and an enzyme called Calcineurin. Blocking this pathway caused the most Self-reactive T cells to lose their bias, and instead develop in the same way as the least Self-reactive T cells.

Guichard et al. propose that the continuous interactions with Self-antigens trigger waves of calcium ions in a naive T cell that shapes its behavior and future development. In a related study, Dong, Othy et al. also conclude that contact with antigen-presenting cells causes calcium signals that shape how the T cells behave.

In addition to providing more detail about the inner workings of immune cells, these findings may also have implications in a clinical setting. Calcineurin inhibitors are often used to suppress the immune system in transplant patients to prevent rejection of the transplanted organ. However, it has proved difficult to safely interrupt these therapies even after many years. These new findings may provide a possible explanation for this, by suggesting that the inhibitors may also interfere with the generation of pTreg cells. Without these cells’ regulatory influence, the immune system is unlikely to ever become tolerant of the transplant.

Pan-PPAR agonist IVA337 is effective in experimental lung fibrosis and pulmonary hypertension

Objective

To evaluate the antifibrotic effects of the pan-peroxisome proliferator-activated receptor (PPAR) agonist IVA337 in preclinical mouse models of pulmonary fibrosis and related pulmonary hypertension (PH).

Methods

IVA337 has been evaluated in the mouse model of bleomycin-induced pulmonary fibrosis and in Fra-2 transgenic mice, this latter being characterised by non-specific interstitial pneumonia and severe vascular remodelling of pulmonary arteries leading to PH. Mice received two doses of IVA337 (30 mg/kg or 100 mg/kg) or vehicle administered by daily oral gavage up to 4 weeks.

Results

IVA337 demonstrated at a dose of 100 mg/kg a marked protection from the development of lung fibrosis in both mouse models compared with mice receiving 30 mg/kg of IVA337 or vehicle. Histological score was markedly reduced by 61% in the bleomycin model and by 50% in Fra-2 transgenic mice, and total lung hydroxyproline concentrations decreased by 28% and 48%, respectively, as compared with vehicle-treated mice. IVA337 at 100 mg/kg also significantly decreased levels of fibrogenic markers in lesional lungs of both mouse models. In addition, IVA337 substantially alleviated PH in Fra-2 transgenic mice by improving haemodynamic measurements and vascular remodelling. In primary human lung fibroblasts, IVA337 inhibited in a dose-dependent manner fibroblast to myofibroblasts transition induced by TGF-β and fibroblast proliferation mediated by PDGF.

Conclusion

We demonstrate that treatment with 100 mg/kg IVA337 prevents lung fibrosis in two complementary animal models and substantially attenuates PH in the Fra-2 mouse model. These findings confirm that the pan-PPAR agonist IVA337 is an appealing therapeutic candidate for these cardiopulmonary involvements.

Macrophages Induce Long-Term Trapping of γδ T Cells with Innate-like Properties within Secondary Lymphoid Organs in the Steady State

So far, peripheral T cells have mostly been described to circulate between blood, secondary lymphoid organs (SLOs), and lymph in the steady state. This nomadic existence would allow them to accomplish their surveying task for both foreign Ags and survival signals. Although it is now well established that γδ T cells can be rapidly recruited to inflammatory sites or in certain tumor microenvironments, the trafficking properties of peripheral γδ T cells have been poorly studied in the steady state. In the present study, we highlight the existence of resident γδ T cells in the SLOs of specific pathogen-free mice. Indeed, using several experimental approaches such as the injection of integrin-neutralizing Abs that inhibit the entry of circulating lymphocytes into lymph nodes and long-term parabiosis experiments, we have found that, contrary to Ly-6C^-/+CD44^lo and Ly-6C⁺CD44^hi γδ T cells, a significant proportion of Ly-6C^-CD44^hi γδ T cells are trapped for long periods of time within lymph nodes and the spleen in the steady state. Specific in vivo cell depletion strategies have allowed us to demonstrate that macrophages are the main actors involved in this long-term retention of Ly-6C^-CD44^hi γδ T cells in SLOs.

Acute Simian Immunodeficiency Virus Infection Triggers Early and Transient Interleukin-7 Production in the Gut, Leading to Enhanced Local Chemokine Expression and Intestinal Immune Cell Homing

The intestinal barrier, one of the first targets of HIV/simian immunodeficiency virus (SIV) is subjected to major physiological changes during acute infection. Having previously shown that pharmaceutical injection of interleukin-7 (IL-7) triggers chemokine expression in many organs leading to massive T-cell homing, in particular to the intestine, we here explored mucosal IL-7 expression as part of the cytokine storm occurring during the acute phase of SIV infection in rhesus macaques. Quantifying both mRNA and protein in tissues, we demonstrated a transient increase of IL-7 expression in the small intestine of SIV-infected rhesus macaques, starting with local detection of the virus by day 3 of infection. We also observed increased transcription levels of several chemokines in the small intestine. In infected macaques, ileal IL-7 expression correlated with the transcription of four of these chemokines. Among these chemokines, the macrophage and/or T-cell attractant chemokines CCL4, CCL25, and CCL28 also demonstrated increased transcription in uninfected IL-7-treated monkeys. Through immunohistofluorescence staining and image analysis, we observed increased CD8⁺ T-cell numbers and stable CD4⁺ T-cell counts in the infected lamina propria (LP) during hyperacute infection. Concomitantly, circulating CCR9⁺beta7⁺ CD4⁺ and CD8⁺ T-cells dropped during acute infection, suggesting augmented intestinal homing of gut-imprinted T-cells. Finally, CD4⁺ macrophages transiently decreased in the submucosa and concentrated in the LP during the first days of infection. Overall, our study identifies IL-7 as a danger signal in the small intestine of Chinese rhesus macaques in response to acute SIV infection. Through stimulation of local chemokine expressions, this overexpression of IL-7 triggers immune cell recruitment to the gut. These findings suggest a role for IL-7 in the initiation of early mucosal immune responses to SIV and HIV infections. However, IL-7 triggered CD4⁺ T-cells and macrophages localization at viral replication sites could also participate to viral spread and establishment of viral reservoirs.

Abstract A05: Biphasic anti-tumoral effect of a vascular-disrupting agent triggering STING and tumor regression

Despite significant advances, cancer immunotherapies fail to systematically elicit tumor regression. It is therefore crucial to understand what conditions the efficacy of immune responses against solid tumors. In particular, while the involvement of T lymphocytes does not need to be further proven, their relative contribution and their cooperation with other cells in regressing tumors is still ill defined. We have investigated in a breast tumor model (PyMT-MMTV) the dynamics of the immune response which takes place during the tumor regression induced by a single i.p. injection of DMXAA, a ligand and activator of STING (a key detector of cytoplasmic DNA and of viral infection). We have shown that the DMXAA-induced tumor vascular disruption, visualized by contrast-enhanced ultrasound, and the associated IFNα/β release, conditioned a swift and massive recruitment of neutrophils, followed by a delayed rise in CD8 T cells and inflammatory monocytes in the tumor mass. All these immune cell subsets contributed to the efficacy of tumor regression, as evidenced by in vivo depletion experiments, which, together with dynamic imaging allowed to characterize cooperations between these immune cell subsets. We have analyzed the kinetics of the biphasic effect of DMXAA : vascular disruption followed by an anti-tumoral immune response. These data support the idea that the inflammation in the tumor microenvironment can be modulated to reset immune cell cooperation like in an acute phase of an immune response against foreign pathogens.

Note: This abstract was not presented at the conference.

Citation Format: Julia M. Weiss, Marion Guerin, Fabienne Regnier, Maxime Thoreau, Elisa Peranzoni, Vincent Feuillet, Gilles Renault, Thomas Guilbert, Alain Trautmann, Nadege Bercovici. Biphasic anti-tumoral effect of a vascular-disrupting agent triggering STING and tumor regression. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2016 Oct 20-23; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2017;5(3 Suppl):Abstract nr A05.

Tumor Stiffening, a Key Determinant of Tumor Progression, is Reversed by Nanomaterial-Induced Photothermal Therapy

Tumor stiffening, stemming from aberrant production and organization of extracellular matrix (ECM), has been considered a predictive marker of tumor malignancy, non-invasively assessed by ultrasound shear wave elastography (SWE). Being more than a passive marker, tumor stiffening restricts the delivery of diagnostic and therapeutic agents to the tumor and per se could modulate cellular mechano-signaling, tissue inflammation and tumor progression. Current strategies to modify the tumor extracellular matrix are based on ECM-targeting chemical agents but also showed deleterious systemic effects.

On-demand excitable nanomaterials have shown their ability to perturb the tumor microenvironment in a spatiotemporal-controlled manner and synergistically with chemotherapy. Here, we investigated the evolution of tumor stiffness as well as tumor integrity and progression, under the effect of mild hyperthermia and thermal ablation generated by light-exposed multi-walled carbon nanotubes (MWCNTs) in an epidermoid carcinoma mouse xenograft. SWE was used for real-time mapping of the tumor stiffness, both during the two near infrared irradiation sessions and over the days after the treatment. We observed a transient and reversible stiffening of the tumor tissue during laser irradiation, which was lowered at the second session of mild hyperthermia or photoablation. In contrast, over the days following photothermal treatment, the treated tumors exhibited a significant softening together with volume reduction, whereas non-treated growing tumors showed an increase of tumor rigidity. The organization of the collagen matrix and the distribution of CNTs revealed a spatio-temporal correlation between the presence of nanoheaters and the damages on collagen and cells. This study highlights nanohyperthermia as a promising adjuvant strategy to reverse tumor stiffening and normalize the mechanical tumor environment.

Pan PPAR agonist IVA337 is effective in prevention and treatment of experimental skin fibrosis

Background

The pathogenesis of systemic sclerosis (SSc) involves a distinctive triad of autoimmune, vascular and inflammatory alterations resulting in fibrosis. Evidence suggests that peroxisome proliferator-activated receptors (PPARs) play an important role in SSc-related fibrosis and their agonists may become effective therapeutic targets.

Objective

To determine the expression of PPARs in human fibrotic skin and investigate the effects of IVA337, a pan PPAR agonist, in in vitro and in vivo models of fibrosis.

Methods

The antifibrotic effects of IVA337 were studied using a bleomycin-induced mouse model of dermal fibrosis. The in vivo effect of IVA337 on wound closure and inflammation were studied using an excisional model of wound healing.

Results

Low levels of PPARα and PPARγ were detected in the skin of patients with SSc compared with controls. In mice, IVA337 was associated with decreased extracellular matrix (ECM) deposition and reduced expression of phosphorylated SMAD2/3—intracellular effector of transforming growth factor (TGF)-β1. Although the antifibrotic effect of pan PPAR was similar to that of PPARγ agonist alone, a significant downregulation of several markers of inflammation was associated with IVA337. Despite its anti-inflammatory and antifibrotic properties, IVA337 did not interfere with wound closure. In vitro effects of IVA337 included attenuation of transcription of ECM genes and alteration of canonical and non-canonical TGF-β signalling pathways.

Conclusions

These findings indicate that simultaneous activation of all three PPAR isoforms exerts a dampening effect on inflammation and fibrosis, making IVA337 a potentially effective therapeutic candidate in the treatment of fibrotic diseases including SSc.

Claudin-16 Deficiency Impairs Tight Junction Function in Ameloblasts, Leading to Abnormal Enamel Formation

Claudin-16 protein (CLDN16) is a component of tight junctions (TJ) with a restrictive distribution so far demonstrated mainly in the kidney. Here, we demonstrate the expression of CLDN16 also in the tooth germ and show that claudin-16 gene (CLDN16) mutations result in amelogenesis imperfecta (AI) in the 5 studied patients with familial hypomagnesemia with hypercalciuria and nephrocalcinosis (FHHNC). To investigate the role of CLDN16 in tooth formation, we studied a murine model of FHHNC and showed that CLDN16 deficiency led to altered secretory ameloblast TJ structure, lowering of extracellular pH in the forming enamel matrix, and abnormal enamel matrix protein processing, resulting in an enamel phenotype closely resembling human AI. This study unravels an association of FHHNC owing to CLDN16 mutations with AI, which is directly related to the loss of function of CLDN16 during amelogenesis. Overall, this study indicates for the first time the importance of a TJ protein in tooth formation and underlines the need to establish a specific dental follow-up for these patients.

How Tissue Mechanical Properties Affect Enteric Neural Crest Cell Migration

Neural crest cells (NCCs) are a population of multipotent cells that migrate extensively during vertebrate development. Alterations to neural crest ontogenesis cause several diseases, including cancers and congenital defects, such as Hirschprung disease, which results from incomplete colonization of the colon by enteric NCCs (ENCCs). We investigated the influence of the stiffness and structure of the environment on ENCC migration in vitro and during colonization of the gastrointestinal tract in chicken and mouse embryos. We showed using tensile stretching and atomic force microscopy (AFM) that the mesenchyme of the gut was initially soft but gradually stiffened during the period of ENCC colonization. Second-harmonic generation (SHG) microscopy revealed that this stiffening was associated with a gradual organization and enrichment of collagen fibers in the developing gut. Ex-vivo 2D cell migration assays showed that ENCCs migrated on substrates with very low levels of stiffness. In 3D collagen gels, the speed of the ENCC migratory front decreased with increasing gel stiffness, whereas no correlation was found between porosity and ENCC migration behavior. Metalloprotease inhibition experiments showed that ENCCs actively degraded collagen in order to progress. These results shed light on the role of the mechanical properties of tissues in ENCC migration during development.

The HIV-1 protein Vpr impairs phagosome maturation by controlling microtubule-dependent trafficking

The HIV protein Vpr interacts with EB1, p150^Glued, and dynein heavy chain and perturbs the centripetal movement of phagosomes and their maturation, resulting in impaired phagolysosome biogenesis, which is important for bacterial clearance and cytokine production.

Human immunodeficiency virus type 1 (HIV-1) impairs major functions of macrophages but the molecular basis for this defect remains poorly characterized. Here, we show that macrophages infected with HIV-1 were unable to respond efficiently to phagocytic triggers and to clear bacteria. The maturation of phagosomes, defined by the presence of late endocytic markers, hydrolases, and reactive oxygen species, was perturbed in HIV-1–infected macrophages. We showed that maturation arrest occurred at the level of the EHD3/MICAL-L1 endosomal sorting machinery. Unexpectedly, we found that the regulatory viral protein (Vpr) was crucial to perturb phagosome maturation. Our data reveal that Vpr interacted with EB1, p150^Glued, and dynein heavy chain and was sufficient to critically alter the microtubule plus end localization of EB1 and p150^Glued, hence altering the centripetal movement of phagosomes and their maturation. Thus, we identify Vpr as a modulator of the microtubule-dependent endocytic trafficking in HIV-1–infected macrophages, leading to strong alterations in phagolysosome biogenesis.

Vasculopathy-related clinical and pathological features are associated with severe juvenile dermatomyositis

OBJECTIVE

Outcome of JDM is highly heterogeneous. Our objective was to determine clinical and muscle biopsy features associated with poor outcome and response to treatment.

METHODS

Clinical data and muscle biopsy were obtained from a monocentric cohort of 29 patients. Clinical subgroups were defined by latent class model analysis of initial and follow-up parameters. Myopathological features were analysed using validated scores. Capillary loss was determined on reconstructions of transversal sections and assessed in the different age groups to take into account variations of muscle capillarization during post-natal development. Regression models were used to identify initial predictors of therapeutic response.

RESULTS

Two distinct homogeneous subgroups of patients were identified according to clinical severity and pathological findings. The smallest group of patients (7/29) presented with severe JDM. Compared with the other group (22/29), patients had more severe muscle weakness at disease onset, low remission rate at 12 months, frequent subcutaneous limb oedema or gastrointestinal (GI) involvement and higher myopathological scores (capillary dropout, perifascicular necrosis/regeneration, fibres with internal myonuclei and fibrosis subscores). Relevance of capillary dropout to JDM severity was substantiated by age-based analysis, confirming its major role in JDM pathophysiology. Most of these manifestations could be related to vasculopathy (limb oedema, GI involvement, capillary dropout). Furthermore, Childhood Myositis Assessment Scale <34 with either GI involvement or muscle endomysial fibrosis at disease onset were the best predictors of poor response to treatment.

CONCLUSION

Vasculopathy is prominent in severe JDM. Simple criteria can be used at initial evaluation to identify patients requiring a more intensive therapy.

The toxoplasma-host cell junction is anchored to the cell cortex to sustain parasite invasive force

Background

The public health threats imposed by toxoplasmosis worldwide and by malaria in sub-Saharan countries are directly associated with the capacity of their related causative agents Toxoplasma and Plasmodium, respectively, to colonize and expand inside host cells. Therefore, deciphering how these two Apicomplexan protozoan parasites access their host cells has been highlighted as a priority research with the perspective of designing anti-invasive molecules to prevent diseases. Central to the mechanism of invasion for both genera is mechanical force, which is thought to be applied by the parasite at the interface between the two cells following assembly of a unique cell-cell junction but this model lacks direct evidence and has been challenged by recent genetic studies. In this work, using parasites expressing the fluorescent core component of this junction, we analyze characteristic features of the kinematics of penetration of more than 1,000 invasion events.

Results

The majority of invasion events occur with a typical forward rotational progression of the parasite through a static junction into an invaginating host cell plasma membrane. However, if parasites encounter resistance and if the junction is not strongly anchored to the host cell cortex, as when parasites do not secrete the toxofilin protein and, therefore, are unable to locally remodel the cortical actin cytoskeleton, the junction travels retrogradely with the host cell membrane along the parasite surface allowing the formation of a functional vacuole. Kinetic measurements of the invasive trajectories strongly support a similar parasite driven force in both static and capped junctions, both of which lead to successful invasion. However, about 20% of toxofilin mutants fail to enter and eventually disengage from the host cell membrane while the secreted RhOptry Neck (RON2) molecules are posteriorally capped before being cleaved and released in the medium. By contrast in cells characterized by low cortex tension and high cortical actin dynamics junction capping and entry failure are drastically reduced.

Conclusions

This kinematic analysis newly highlights that to invade cells parasites need to engage their motor with the junction molecular complex where force is efficiently applied only upon proper anchorage to the host cell membrane and cortex.

Electronic supplementary material

The online version of this article (doi:10.1186/s12915-014-0108-y) contains supplementary material, which is available to authorized users.

A robust collagen scoring method for human liver fibrosis by second harmonic microscopy

Second Harmonic Generation (SHG) microscopy offers the opportunity to image collagen of type I without staining. We recently showed that a simple scoring method, based on SHG images of histological human liver biopsies, correlates well with the Metavir assessment of fibrosis level (Gailhouste et al., J. Hepatol., 2010). In this article, we present a detailed study of this new scoring method with two different objective lenses. By using measurements of the objectives point spread functions and of the photomultiplier gain, and a simple model of the SHG intensity, we show that our scoring method, applied to human liver biopsies, is robust to the objective's numerical aperture (NA) for low NA, the choice of the reference sample and laser power, and the spatial sampling rate. The simplicity and robustness of our collagen scoring method may open new opportunities in the quantification of collagen content in different organs, which is of main importance in providing diagnostic information and evaluation of therapeutic efficiency.

Fibrillar collagen scoring by second harmonic microscopy: a new tool in the assessment of liver fibrosis

BACKGROUND & AIMS

Imaging of supramolecular structures by multiphoton microscopy offers significant advantages for studying specific fibrillar compounds in biological tissues. In this study, we aimed to demonstrate the relevance of Second Harmonic Generation (SHG) for assessing and quantifying, without staining, fibrillar collagen in liver fibrosis.

METHODS

We first showed the relationship between SHG signal and collagen forms over-produced and accumulated during fibrosis progression. Taking this property into consideration, we developed an innovative method to precisely quantify the fibrosis area in histological slices by scoring of fibrillar collagen deposits (Fibrosis-SHG index).

RESULTS

The scoring method was routinely applied to 119 biopsies from patients with chronic liver disease allowing a fast and accurate measurement of fibrosis correlated with the Fibrosis-Metavir score (rho=0.75, p<0.0001). The technique allowed discriminating patients with advanced (moderate to severe) fibrosis (AUROC=0.88, p<0.0001) and cirrhosis (AUROC=0.89, p<0.0001). Taking advantage of its continuous gradation, the Fibrosis-SHG index also allowed the discrimination of several levels of fibrosis within the same F-Metavir stage. The SHG process presented several advantages such as a high reliability and sensitivity that lead to a standardized evaluation of hepatic fibrosis in liver biopsies without staining and pathological examination.

CONCLUSIONS

Second harmonic microscopy emerges as an original and powerful tool in the assessment of liver fibrosis and offers new possibilities for the evaluation of experimental protocols. We expect that this technology could easily be applicable in the study of other fibro-proliferative pathologies.

Collagen and myosin characterization by orientation field second harmonic microscopy

Collagen and myosin fibrils are endogenous harmonophores that both give rise to Second Harmonic Generation (SHG). By combining four polarization SHG images provided by a scanning microscope, we show that the orientation of the principal axis of the nonlinear susceptibility tensor chi(2) can be determined for each pixel of the image. The ratio rho = chi33/chi15 of the principal components of chi(2) of collagen and myosin was obtained with the same method, and found within the range 1.6-1.8 and 0.5-0.6 respectively. The orientation of the principal axis of chi(2) is shown to be correlated to the orientation of the fibrils themselves. This provides a straightforward method, which we call Orientation Field-Second Harmonic Microscopy (OF-SHM), to reconstruct orientation fields of fibrils at various scales and resolutions in different biological systems (from muscle sarcomere to the whole embryo).