Learning image representations for anomaly detection: Application to discovery of histological alterations in drug development

We present a system for anomaly detection in histopathological images. In histology, normal samples are usually abundant, whereas anomalous (pathological) cases are scarce or not available. Under such settings, one-class classifiers trained on healthy data can detect out-of-distribution anomalous samples. Such approaches combined with pre-trained Convolutional Neural Network (CNN) representations of images were previously employed for anomaly detection (AD). However, pre-trained off-the-shelf CNN representations may not be sensitive to abnormal conditions in tissues, while natural variations of healthy tissue may result in distant representations. To adapt representations to relevant details in healthy tissue we propose training a CNN on an auxiliary task that discriminates healthy tissue of different species, organs, and staining reagents. Almost no additional labeling workload is required, since healthy samples come automatically with aforementioned labels. During training we enforce compact image representations with a center-loss term, which further improves representations for AD. The proposed system outperforms established AD methods on a published dataset of liver anomalies. Moreover, it provided comparable results to conventional methods specifically tailored for quantification of liver anomalies. We show that our approach can be used for toxicity assessment of candidate drugs at early development stages and thereby may reduce expensive late-stage drug attrition.

Monocyte-derived alveolar macrophages are key drivers of smoke-induced lung inflammation and tissue remodeling

Smoking is a leading risk factor of chronic obstructive pulmonary disease (COPD), that is characterized by chronic lung inflammation, tissue remodeling and emphysema. Although inflammation is critical to COPD pathogenesis, the cellular and molecular basis underlying smoking-induced lung inflammation and pathology remains unclear. Using murine smoke models and single-cell RNA-sequencing, we show that smoking establishes a self-amplifying inflammatory loop characterized by an influx of molecularly heterogeneous neutrophil subsets and excessive recruitment of monocyte-derived alveolar macrophages (MoAM). In contrast to tissue-resident AM, MoAM are absent in homeostasis and characterized by a pro-inflammatory gene signature. Moreover, MoAM represent 46% of AM in emphysematous mice and express markers causally linked to emphysema. We also demonstrate the presence of pro-inflammatory and tissue remodeling associated MoAM orthologs in humans that are significantly increased in emphysematous COPD patients. Inhibition of the IRAK4 kinase depletes a rare inflammatory neutrophil subset, diminishes MoAM recruitment, and alleviates inflammation in the lung of cigarette smoke-exposed mice. This study extends our understanding of the molecular signaling circuits and cellular dynamics in smoking-induced lung inflammation and pathology, highlights the functional consequence of monocyte and neutrophil recruitment, identifies MoAM as key drivers of the inflammatory process, and supports their contribution to pathological tissue remodeling.

Molecular basis of GDF15 induction and suppression by drugs in cardiomyocytes and cancer cells toward precision medicine

GDF15 has recently emerged as a key driver of the development of various disease conditions including cancer cachexia. Not only the tumor itself but also adverse effects of chemotherapy have been reported to contribute to increased GDF15. Although regulation of GDF15 transcription by BET domain has recently been reported, the molecular mechanisms of GDF15 gene regulation by drugs are still unknown, leaving uncertainty about the safe and effective therapeutic strategies targeting GDF15. We screened various cardiotoxic drugs and BET inhibitors for their effects on GDF15 regulation in human cardiomyocytes and cancer cell lines and analyzed in-house and public gene signature databases. We found that DNA damaging drugs induce GDF15 in cardiomyocytes more strongly than drugs with other modes of action. In cancer cells, GDF15 induction varied depending on drug- and cell type-specific gene signatures including mutations in PI3KCA, TP53, BRAF and MUC16. GDF15 suppression by BET inhibition is particularly effective in cancer cells with low activity of the PI3K/Akt axis and high extracellular concentrations of pantothenate. Our findings provide insights that the risk for GDF15 overexpression and concomitant cachexia can be reduced by a personalized selection of anticancer drugs and patients for precision medicine.

AAV-mediated expression of a new conformational anti-aggregated α-synuclein antibody prolongs survival in a genetic model of α-synucleinopathies

Prion-like transmission of pathology in α-synucleinopathies like Parkinson's disease or multiple system atrophy is increasingly recognized as one potential mechanism to address disease progression. Active and passive immunotherapies targeting insoluble, aggregated α-synuclein are already being actively explored in the clinic with mixed outcomes so far. Here, we report the identification of 306C7B3, a highly selective, aggregate-specific α-synuclein antibody with picomolar affinity devoid of binding to the monomeric, physiologic protein. 306C7B3 binding is Ser129-phosphorylation independent and shows high affinity to several different aggregated α-synuclein polymorphs, increasing the likelihood that it can also bind to the pathological seeds assumed to drive disease progression in patients. In support of this, highly selective binding to pathological aggregates in postmortem brains of MSA patients was demonstrated, with no staining in samples from other human neurodegenerative diseases. To achieve CNS exposure of 306C7B3, an adeno-associated virus (AAV) based approach driving expression of the secreted antibody within the brain of (Thy-1)-[A30P]-hα-synuclein mice was used. Widespread central transduction after intrastriatal inoculation was ensured by using the AAV2HBKO serotype, with transduction being spread to areas far away from the inoculation site. Treatment of (Thy-1)-[A30P]-hα-synuclein mice at the age of 12 months demonstrated significantly increased survival, with 306C7B3 concentration reaching 3.9 nM in the cerebrospinal fluid. These results suggest that AAV-mediated expression of 306C7B3, targeting extracellular, presumably disease-propagating aggregates of α-synuclein, has great potential as a disease-modifying therapy for α-synucleinopathies as it ensures CNS exposure of the antibody, thereby mitigating the selective permeability of the blood-brain barrier.

FAM3D: A gut secreted protein and its potential in the regulation of glucose metabolism

The number of diabetic patients is rising globally and concomitantly so do the diabetes associated complications. The gut secretes a variety of proteins to control blood glucose levels and/or food intake. As the drug class of GLP-1 agonists is based on a gut secreted peptide and the positive metabolic effects of bariatric surgery are at least partially mediated by gut peptides, we were interested in other gut secreted proteins which have yet to be explored. In this respect we identified the gut secreted protein FAM3D by analyzing sequencing data from L- and epithelial cells of VSG and sham operated as well as chow and HFD fed mice. FAM3D was overexpressed in diet induced obese mice via an adeno-associated virus (AAV), which resulted in a significant improvement of fasting blood glucose levels, glucose tolerance and insulin sensitivity. The liver lipid deposition was reduced, and the steatosis morphology was improved. Hyperinsulinemic clamps indicated that FAM3D is a global insulin sensitizer and increases glucose uptake into various tissues. In conclusion, the current study demonstrated that FAM3D controls blood glucose levels by acting as an insulin sensitizing protein and improves hepatic lipid deposition.

European Society of Toxicologic Pathology (Pathology 2.0 Molecular Pathology Special Interest Group): Review of In Situ Hybridization Techniques for Drug Research and Development

In situ hybridization (ISH) is used for the localization of specific nucleic acid sequences in cells or tissues by complementary binding of a nucleotide probe to a specific target nucleic acid sequence. In the last years, the specificity and sensitivity of ISH assays were improved by innovative techniques like synthetic nucleic acids and tandem oligonucleotide probes combined with signal amplification methods like branched DNA, hybridization chain reaction and tyramide signal amplification. These improvements increased the application spectrum for ISH on formalin-fixed paraffin-embedded tissues. ISH is a powerful tool to investigate DNA, mRNA transcripts, regulatory noncoding RNA, and therapeutic oligonucleotides. ISH can be used to obtain spatial information of a cell type, subcellular localization, or expression levels of targets. Since immunohistochemistry and ISH share similar workflows, their combination can address simultaneous transcriptomics and proteomics questions. The goal of this review paper is to revisit the current state of the scientific approaches in ISH and its application in drug research and development.

Cross-reactivity of human monoclonal antibodies with canine peripheral blood mononuclear cells

In drug development, the dog is often used as a model for non-rodent preclinical safety studies. In particular, immunophenotyping in dogs can be important to characterize the toxicological profile of a test item. A wide range of antibodies specific to surface antigens is needed, however, commercially available antibodies to dog are scarce. To date, numerous studies have reported the cross-reactivity of human monoclonal antibodies with canine peripheral blood mononuclear cells (PBMC). In this study, we aimed to increase the number of canine-specific antibodies and took a rather novel approach to further determine cross-reactivity of 378 human recombinant antibodies lacking Fc regions to surface antigens on canine PBMC. The screening resulted in 30 human monoclonal antibodies well reactive to canine PBMC. Sequence homology of the targeted human and canine antigens was analyzed with Basic Local Alignment Search Tool. Thirteen human cross-reactive antibodies of interest were analyzed with cells from canine whole blood in combination with lineage markers. Finally, ten antibodies were identified as useful markers for the application in dog. Except for CD27, the remaining nine antibodies are already commercially available human cross-reactive antibodies. This study provides a new source for all ten antibodies described here.

Rosa26-LSL-dCas9-VPR: a versatile mouse model for tissue specific and simultaneous activation of multiple genes for drug discovery

Transgenic animals with increased or abrogated target gene expression are powerful tools for drug discovery research. Here, we developed a CRISPR-based Rosa26-LSL-dCas9-VPR mouse model for targeted induction of endogenous gene expression using different Adeno-associated virus (AAV) capsid variants for tissue-specific gRNAs delivery. To show applicability of the model, we targeted low-density lipoprotein receptor (LDLR) and proprotein convertase subtilisin/kexin type 9 (PCSK9), either individually or together. We induced up to ninefold higher expression of hepatocellular proteins. In consequence of LDLR upregulation, plasma LDL levels almost abolished, whereas upregulation of PCSK9 led to increased plasma LDL and cholesterol levels. Strikingly, simultaneous upregulation of both LDLR and PCSK9 resulted in almost unaltered LDL levels. Additionally, we used our model to achieve expression of all α₁-Antitrypsin (AAT) gene paralogues simultaneously. These results show the potential of our model as a versatile tool for optimized targeted gene expression, alone or in combination.

Characterization of a flexible AAV-DTR/DT mouse model of acute epithelial lung injury

Animal models are important to mimic certain pathways or biological aspects of human pathologies including acute and chronic pulmonary diseases. We developed a novel and flexible mouse model of acute epithelial lung injury based on adeno-associated virus (AAV) variant 6.2 mediated expression of the human diphtheria toxin receptor (DTR). Following intratracheal administration of diphtheria toxin (DT), a cell-specific death of bronchial and alveolar epithelial cells can be observed. In contrast to other lung injury models, the here described mouse model provides the possibility of targeted injury using specific tropisms of AAV vectors or cell type specific promotors to drive the human DTR expression. Also, generation of cell specific mouse lines is not required. Detailed characterization of the AAV-DTR/DT mouse model including titration of viral genome (vg) load and administered DT amount revealed increasing cell numbers in bronchoalveolar lavage (BAL; macrophages, neutrophils, and unspecified cells) and elevation of degenerated cells and infiltrated leukocytes in lung tissue, dependent of vg load and DT dose. Cytokine levels in BAL fluid showed different patterns with higher vg load, e.g. IFNγ, TNFα, and IP10 increasing and IL-5 and IL-6 decreasing, while lung function was not affected. Additionally, laser-capture microdissection (LCM)-based proteomics of bronchial epithelium and alveolar tissue revealed upregulated immune and inflammatory response in all regions and extracellular matrix deposition in infiltrated alveoli. Overall, our novel AAV-DTR/DT model allows investigation of repair mechanisms following epithelial injury and resembles specific mechanistic aspects of acute and chronic pulmonary diseases.

Abstract 4193: Lymphotoxin-alpha-armed oncolytic VSV-GP synergizes with SMAC mimetics to induce enhanced tumor cell death and regression

Introduction: Oncolytic viruses (OVs), which selectively replicate in and destroy tumor cells, form a highly promising class of cancer therapeutics with a strong immune stimulatory potential. VSV-GP, a chimeric Vesicular Stomatitis Virus (VSV) pseudotyped with the glycoprotein of the lymphocytic choriomeningitis virus (LCMV) can selectively replicate and express therapeutic cargos in the tumor microenvironment. Lymphotoxin alpha (LTα) - a member of the TNF superfamily - may present as a potent therapeutic cargo based on its immune stimulatory and cell death modulatory characteristics.In this study, we explore the immune promoting and tumor cell death inducing properties of VSV-GP-LTα, a next generation variant with an NF-κB facilitated mode of action. We further investigate clinically relevant combination therapies with “second mitochondria-derived activator of caspases” mimetic compounds (SMCs).

Experimental Procedures: Viral fitness, cargo expression and test substance quality were assessed using growth kinetic, ELISA, RT-qPCR and titration assays. Therapeutic efficacy and safety of VSV-GP-LTα, with or without SMC co-treatment, were assessed in vivo in syngeneic C57BL/6 mice bearing subcutaneous LLC1-IFNAR-/- or B16F10-OVA tumors. To shed further light into the VSV-GP-LTα treatment effects, we applied immunohistochemistry, flow cytometry, multiplex ELISA and Nanostring® assays.

Data Summary: VSV-GP-LTα induced stronger anti-tumor effects and increased overall survival compared to VSV-GP. It was also better tolerated than VSV-GP armed with TNF-α, a therapeutic cargo from the same class. Histological and gene expression analysis confirmed widespread cell killing within the tumor and activation of innate and adaptive immune response markers. However, further characterization of the adaptive immune compartment did not show significant changes induced by the expressed LTα. Building on the observed therapeutic strengths of VSV-GP-LTα, we further explored a treatment combination with SMC. This resulted in a therapeutic synergy with improved treatment-induced tumor cell death, especially in a less permissive tumor setting.

Conclusion: Together, here we show that arming VSV-GP with LTα resulted in a strong inflammation of the tumor microenvironment and enhanced levels of tumor cell death induction. This effect could be further enhanced by the co-treatment with SMC.

Citation Format: Bart Spiesschaert, Philipp Müller, Katharina Angerer, Krishna Das, Tobias Nolden, Carles Urbiola, Judy Ng, Fabian Heinemann, Birgit Stierstorfer, Patrik Erlmann, Guido Wollmann. Lymphotoxin-alpha-armed oncolytic VSV-GP synergizes with SMAC mimetics to induce enhanced tumor cell death and regression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 4193.

Characterization and Validation of In Vitro and In Vivo Models to Investigate TNF-α-Induced Inflammation in Retinal Diseases

Purpose

Inflammation is implicated in the etiology of diverse retinopathies including uveitis, age-related macular degeneration or diabetic retinopathy. Tumor necrosis factor alpha (TNF-α) is a well-known proinflammatory cytokine that is described as a biomarker for inflammation in diverse retinopathies and therefore emerged as an interesting target to treat inflammation in the eye by neutralizing anti-TNF-α antibodies.

Methods

Recently, we have demonstrated that Adeno-associated virus (AAV)–mediated expression of human TNF-α in the murine eye induces retinal inflammation including vasculitis and fibrosis, thereby mimicking human disease-relevant pathologies. In a proof-of-mechanism study, we now tested whether AAV-TNF-α induced pathologies can be reversed by neutralizing TNF-α antibody treatment.

Results

Strikingly, a single intravitreal injection of the TNF-α antibody golimumab reduced AAV-TNF-α–induced retinal inflammation and retinal thickening. Furthermore, AAV-TNF-α–mediated impaired retinal function was partially rescued by golimumab as revealed by electroretinography recordings. Finally, to study TNF-α-induced vasculitis in human in vitro cell culture assays, we established a monocyte-to-endothelium adhesion co-culture system. Indeed, also in vitro TNF-α induced monocyte adhesion to human retinal endothelial cells, which was prevented by golimumab.

Conclusions

Overall, our study describes valuable in vitro and in vivo approaches to study the function of TNF-α in retinal inflammation and demonstrated a preclinical proof-of-mechanism treatment with golimumab.

Translational Relevance

The AAV-based model expressing human TNF-α allows us to investigate TNF-α–driven pathologies supporting research in mechanisms of retinal inflammation.

Human stem cell-based retina on chip as new translational model for validation of AAV retinal gene therapy vectors

Gene therapies using adeno-associated viruses (AAVs) are among the most promising strategies to treat or even cure hereditary and acquired retinal diseases. However, the development of new efficient AAV vectors is slow and costly, largely because of the lack of suitable non-clinical models. By faithfully recreating structure and function of human tissues, human induced pluripotent stem cell (iPSC)-derived retinal organoids could become an essential part of the test cascade addressing translational aspects. Organ-on-chip (OoC) technology further provides the capability to recapitulate microphysiological tissue environments as well as a precise control over structural and temporal parameters. By employing our recently developed retina on chip that merges organoid and OoC technology, we analyzed the efficacy, kinetics, and cell tropism of seven first- and second-generation AAV vectors. The presented data demonstrate the potential of iPSC-based OoC models as the next generation of screening platforms for future gene therapeutic studies.

AAV-Mediated Expression of Human VEGF, TNF-α, and IL-6 Induces Retinal Pathology in Mice

Purpose

Retinopathies display complex pathologies, including vasculopathies, inflammation, and fibrosis, leading ultimately to visual impairment. However, animal models accurately reflecting these pathologies are lacking. In this study, we evaluate the suitability of using Adeno-associated virus (AAV)-mediated long-term expression of cytokines to establish retinal pathology in the murine retina.

Methods

We administered recombinant, Müller-glia targeted AAV-ShH10 into the mouse vitreous to induce retinal expression of either human vascular endothelial growth factor (VEGF)-A₁₆₅, tumor necrosis factor alpha (TNF-α), or interleukin-6 (IL-6) and evaluated consequent effects by optical coherence tomography, fluorescein angiography, and histology.

Results

Intravitreal injection of AAVs resulted in rapid and stable expression of the transgenes within 1 to 6 weeks. Akin to the role of VEGF-A in wet age-related macular degeneration, expression of VEGF-A led to several vasculopathies in mice, including neovascularization and vascular leakage. In contrast, the expression of the proinflammatory cytokines TNF-α or IL-6 induced retinal inflammation, as indicated by microglial activation. Furthermore, the expression of TNF-α, but not of IL-6, induced immune cell infiltration into the vitreous as well as vasculitis, and subsequently induced the development of fibrosis and epiretinal membranes.

Conclusions

In summary, the long-term expression of human VEGF-A₁₆₅, TNF-α, or IL-6 in the mouse eye induced specific pathologies within 6 weeks that mimic different aspects of human retinopathies.

Translational Relevance

AAV-mediated expression of human genes in mice is an attractive approach to provide valuable insights into the underlying molecular mechanisms causing retinopathies and is easily adaptable to other genes and preclinical species supporting drug discovery for retinal diseases.

Modulation of vascular contraction via soluble guanylate cyclase signaling in a novel ex vivo method using rat precision-cut liver slices

Fibrotic processes in the liver of non-alcoholic steatohepatitis (NASH) patients cause microcirculatory dysfunction in the organ which increases blood vessel resistance and causes portal hypertension. Assessing blood vessel function in the liver is challenging, necessitating the development of novel methods in normal and fibrotic tissue that allow for drug screening and translation toward pre-clinical settings. Cultures of precision cut liver slices (PCLS) from normal and fibrotic rat livers were used for blood vessel function analysis. Live recording of vessel diameter was used to assess the response to endothelin-1, serotonin and soluble guanylate cyclase (sGC) activation. A cascade of contraction and relaxation events in response to serotonin, endothelin-1, Ketanserin and sGC activity could be established using vessel diameter analysis of rat PCLS. Both the sGC activator BI 703704 and the sGC stimulator Riociguat prevented serotonin-induced contraction in PCLS from naive rats. By contrast, PCLS cultures from the rat CCl4 NASH model were only responsive to the sGC activator, thus establishing that the sGC enzyme is rendered non-responsive to nitric oxide under oxidative stress found in fibrotic livers. The role of the sGC pathway for vessel relaxation of fibrotic liver tissue was identified in our model. The obtained data shows that the inhibitory capacities on vessel contraction of sGC compounds can be translated to published preclinical data. Altogether, this novel ex vivo PCLS method allows for the differentiation of drug candidates and the translation of therapeutic approaches towards the clinical use.

Exosomal miRNAs as Potential Biomarkers to Monitor Phosphodiesterase 5 Inhibitor Induced Anti-Fibrotic Effects on CCl4 Treated Rats

MicroRNAs (miRNAs) are short, non-coding RNA species that are important post-transcriptional regulators of gene expression and play an important role in the pathogenesis of non-alcoholic fatty liver disease. Here, we investigated the phosphodiesterase 5 (PDE5) inhibitor induced effects on hepatic and plasma exosomal miRNA expression in CCl₄-treated rats. In the present study, hepatic miRNA profiling was conducted using the Nanostring nCounter technology and mRNA profiling using RNA sequencing from PDE5 treated rats in the model of CCl₄-induced liver fibrosis. To evaluate if the PDE5 inhibitor affected differentially expressed miRNAs in the liver can be detected in plasma exosomes, qRT-PCR specific assays were used. In livers from CCl₄-treated rats, the expression of 22 miRNAs was significantly increased (>1.5-fold, adj. p < 0.05), whereas the expression of 16 miRNAs was significantly decreased (>1.5-fold, adj. p < 0.05). The majority of the deregulated miRNA species are implicated in fibrotic and inflammatory processes. The PDE5 inhibitor suppressed the induction of pro-fibrotic miRNAs, such as miR-99b miR-100 and miR-199a-5p, and restored levels of anti-fibrotic miR-122 and miR-192 in the liver. In plasma exosomes, we observed elevated levels of miR-99b, miR-100 and miR-142-3p after treatment with the PDE5-inhibitor compared to CCl₄/Vehicle-treated. Our study demonstrated for the first time that during the development of hepatic fibrosis in the preclinical model of CCl₄-induced liver fibrosis, defined aspects of miRNA regulated liver pathogenesis are influenced by PDE5 treatment. In conclusion, miRNA profiling of plasma exosomes might be used as a biomarker for NASH progression and monitoring of treatment effects.

Deep Learning-Based Detection of Endothelial Tip Cells in the Oxygen-Induced Retinopathy Model

Proliferative retinopathies, such as diabetic retinopathy and retinopathy of prematurity, are leading causes of vision impairment. A common feature is a loss of retinal capillary vessels resulting in hypoxia and neuronal damage. The oxygen-induced retinopathy model is widely used to study revascularization of an ischemic area in the mouse retina. The presence of endothelial tip cells indicates vascular recovery; however, their quantification relies on manual counting in microscopy images of retinal flat mount preparations. Recent advances in deep neural networks (DNNs) allow the automation of such tasks. We demonstrate a workflow for detection of tip cells in retinal images using the DNN-based Single Shot Detector (SSD). The SSD was designed for detection of objects in natural images. We adapt the SSD architecture and training procedure to the tip cell detection task and retrain the DNN using labeled tip cells in images of fluorescently stained retina flat mounts. Transferring knowledge from the pretrained DNN and extensive data augmentation reduced the amount of required labeled data. Our system shows a performance comparable to the human level, while providing highly consistent results. Therefore, such a system can automate counting of tip cells, a readout frequently used in retinopathy research, thereby reducing routine work for biomedical experts.

SGLT2 is not expressed in pancreatic α- and β-cells, and its inhibition does not directly affect glucagon and insulin secretion in rodents and humans

Objective

Sodium-glucose cotransporter 2 (SGLT2) inhibitors (SGLT2i), or gliflozins, are anti-diabetic drugs that lower glycemia by promoting glucosuria, but they also stimulate endogenous glucose and ketone body production. The likely causes of these metabolic responses are increased blood glucagon levels, and decreased blood insulin levels, but the mechanisms involved are hotly debated. This study verified whether or not SGLT2i affect glucagon and insulin secretion by a direct action on islet cells in three species, using multiple approaches.

Methods

We tested the in vivo effects of two selective SGLT2i (dapagliflozin, empagliflozin) and a SGLT1/2i (sotagliflozin) on various biological parameters (glucosuria, glycemia, glucagonemia, insulinemia) in mice. mRNA expression of SGLT2 and other glucose transporters was assessed in rat, mouse, and human FACS-purified α- and β-cells, and by analysis of two human islet cell transcriptomic datasets. Immunodetection of SGLT2 in pancreatic tissues was performed with a validated antibody. The effects of dapagliflozin, empagliflozin, and sotagliflozin on glucagon and insulin secretion were assessed using isolated rat, mouse and human islets and the in situ perfused mouse pancreas. Finally, we tested the long-term effect of SGLT2i on glucagon gene expression.

Results

SGLT2 inhibition in mice increased the plasma glucagon/insulin ratio in the fasted state, an effect correlated with a decline in glycemia. Gene expression analyses and immunodetections showed no SGLT2 mRNA or protein expression in rodent and human islet cells, but moderate SGLT1 mRNA expression in human α-cells. However, functional experiments on rat, mouse, and human (29 donors) islets and the in situ perfused mouse pancreas did not identify any direct effect of dapagliflozin, empagliflozin or sotagliflozin on glucagon and insulin secretion. SGLT2i did not affect glucagon gene expression in rat and human islets.

Conclusions

The data indicate that the SGLT2i-induced increase of the plasma glucagon/insulin ratio in vivo does not result from a direct action of the gliflozins on islet cells.

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Gliflozins (SGLT2 and SGLT1/2 inhibitors) increase plasma glucagon/insulin ratio.

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SGLT2 is not expressed in rodent and human pancreatic α- and β-cells.

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SGLT1 is however expressed in human α-cells.

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SGLT2 and SGLT1/2 inhibitors do not directly affect glucagon and insulin secretion.

Automatization and improvement of μCT analysis for murine lung disease models using a deep learning approach

Background

One of the main diagnostic tools for lung diseases in humans is computed tomography (CT). A miniaturized version, micro-CT (μCT) is utilized to examine small rodents including mice. However, fully automated threshold-based segmentation and subsequent quantification of severely damaged lungs requires visual inspection and manual correction.

Methods

Here we demonstrate the use of densitometry on regions of interest (ROI) in automatically detected portions of the lung, thus avoiding the need for lung segmentation. Utilizing deep learning approaches, the middle part of the lung is found in a μCT-stack and a ROI is placed in the left and the right lobe.

Results

The intensity values within the ROIs of the μCT images were collected and subsequently used for the calculation of different lung-related parameters, such as mean lung attenuation (MLA), mode, full width at half maximum (FWHM), and skewness. For validation, the densitometric approach was correlated with histological readouts (Ashcroft Score, Mean Linear Intercept).

Conclusion

We here show an automated tool that allows rapid and in-depth analysis of μCT scans of different murine models of lung disease.

Quantitative Profiling of the Human Substantia Nigra Proteome from Laser-capture Microdissected FFPE Tissue

Laser-capture microdissection (LCM) allows the visualization and isolation of morphologically distinct subpopulations of cells from heterogeneous tissue specimens. In combination with formalin-fixed and paraffin-embedded (FFPE) tissue it provides a powerful tool for retrospective and clinically relevant studies of tissue proteins in a healthy and diseased context. We first optimized the protocol for efficient LCM analysis of FFPE tissue specimens. The use of SDS containing extraction buffer in combination with the single-pot solid-phase-enhanced sample preparation (SP3) digest method gave the best results regarding protein yield and protein/peptide identifications. Microdissected FFPE human substantia nigra tissue samples (∼3,000 cells) were then analyzed, using tandem mass tag (TMT) labeling and LC-MS/MS, resulting in the quantification of >5,600 protein groups. Nigral proteins were classified and analyzed by abundance, showing an enrichment of extracellular exosome and neuron-specific gene ontology (GO) terms among the higher abundance proteins. Comparison of microdissected samples with intact tissue sections, using a label-free shotgun approach, revealed an enrichment of neuronal cell type markers, such as tyrosine hydroxylase and alpha-synuclein, as well as proteins annotated with neuron-specific GO terms. Overall, this study provides a detailed protocol for laser-capture proteomics using FFPE tissue and demonstrates the efficiency of LCM analysis of distinct cell subpopulations for proteomic analysis using low sample amounts.

Recapitulating idiopathic pulmonary fibrosis related alveolar epithelial dysfunction in a human iPSC-derived air-liquid interface model

Idiopathic pulmonary fibrosis (IPF) is a fatal disease of unknown cause that is characterized by progressive fibrotic lung remodeling. An abnormal emergence of airway epithelial-like cells within the alveolar compartments of the lung, herein termed bronchiolization, is often observed in IPF. However, the origin of this dysfunctional distal lung epithelium remains unknown due to a lack of suitable human model systems. In this study, we established a human induced pluripotent stem cell (iPSC)-derived air-liquid interface (ALI) model of alveolar epithelial type II (ATII)-like cell differentiation that allows us to investigate alveolar epithelial progenitor cell differentiation in vitro. We treated this system with an IPF-relevant cocktail (IPF-RC) to mimic the pro-fibrotic cytokine milieu present in IPF lungs. Stimulation with IPF-RC during differentiation increases secretion of IPF biomarkers and RNA sequencing (RNA-seq) of these cultures reveals significant overlap with human IPF patient data. IPF-RC treatment further impairs ATII differentiation by driving a shift toward an airway epithelial-like expression signature, providing evidence that a pro-fibrotic cytokine environment can influence the proximo-distal differentiation pattern of human lung epithelial cells. In conclusion, we show for the first time, the establishment of a human model system that recapitulates aspects of IPF-associated bronchiolization of the lung epithelium in vitro.

Deep learning enables pathologist-like scoring of NASH models

Non-alcoholic fatty liver disease (NAFLD) and the progressive form of non-alcoholic steatohepatitis (NASH) are diseases of major importance with a high unmet medical need. Efficacy studies on novel compounds to treat NAFLD/NASH using disease models are frequently evaluated using established histological feature scores on ballooning, inflammation, steatosis and fibrosis. These features are assessed by a trained pathologist using microscopy and assigned discrete scores. We demonstrate how to automate these scores with convolutional neural networks (CNNs). Whole slide images of stained liver sections are analyzed using two different scales with four CNNs, each specialized for one of four histopathological features. A continuous value is obtained to quantify the extent of each feature, which can be used directly to provide a high resolution readout. In addition, the continuous values can be mapped to obtain the established discrete pathologist-like scores. The automated deep learning-based scores show good agreement with the trainer - a human pathologist.

Abstract 2267: Therapeutic synergy of the chimeric, oncolytic virus VSV-GP with immune modulators

Introduction: Oncolytic viruses (OVs), which selectively replicate in and destroy tumor cells, represent a highly promising class of cancer therapeutics. In recent years, the focus in the OV field has significantly shifted from a pure oncolytic mode of action to their strong immune stimulatory potential. Tumor cells lysed by the viruses release pro-inflammatory signals, tumor associated antigens as well as display hallmarks of immunogenic cell death. VSV-GP, a chimeric VSV pseudotyped with the glycoprotein of the lymphocytic choriomeningitis virus (LCMV) is a potent tumor cell-lysing agent and capable of jump-starting α-tumor immunity. The current study explores the immune promoting properties of VSV-GP and investigates clinically relevant combination therapies with checkpoint inhibition (α-PD-1) as well as a “second mitochondria-derived activator of caspases“ mimetic (SMACm).

Experimental Procedures: Immune competent mice bearing established LLC1-IFNARKO, B16-F1-OVA or CT26.CL25-IFNARKO tumors were subject to treatments comprising VSV-GP, α-PD-1, a SMACm or combinations of VSV-GP with either of the latter therapies. α-tumor effects were determined by tumor growth inhibition and/or changes in overall survival. VSV-GP's tumor cell selective replication, resulting in immune activation, was assessed using FFPE based IHC staining for the viral N-protein, PD-L1 and different immune cell subsets as well as the NanoString platform (nCounter Pan Cancer Immune Profiling Panel).

Data Summary: Here we present data on VSV-GP, which displays potent α-tumor efficacy and upon systemic delivery increases the local T-cell infiltration, expression of chemokines, T-cell and myeloid cell specific activation markers as well as expression of immune checkpoints, such as PD-1 and PD-L1 within the tumor microenvironment. Building on the observed therapeutic potential of VSV-GP as monotherapy, its immune promoting properties and the delineated compensatory mechanisms, such as PD-1/-L1 upregulation, we explored therapeutic combinations with a PD-1 blocking antibody, which resulted in a strong improvement of VSV-GP-mediated α-tumor efficacy as well as overall survival. Cured, tumor free animals were protected from tumor rechallange indicating immunological memory formation. We further explored the therapeutic combination of VSV-GP with a SMACm, which also resulted in a strongly improved therapeutic benefit and increased overall survival.

Conclusion: In summary VSV-GP induces a pro-inflammatory microenvironment within infected tumors, increases immune cell infiltration and synergizes with α-PD-1 as well as a SMACm. VSV-GP is a potent OV with a strong α-tumor immunity promoting potential. Preclinical data justify further testing of VSV-GP and the combinations with PD-1 blockade or a SMACm in clinical trials.

Citation Format: Philipp Mueller, Patrik Erlmann, Monika Petersson, Tobias Nolden, Carles Urbiola, Liesa-Marie Schreiber, Bart Spiesschaert, Klaus Erb, Birgit Stierstorfer, Maria Antonietta Impagnatiello, Eric Borges, Knut Elbers, Guido Wollmann, John Park. Therapeutic synergy of the chimeric, oncolytic virus VSV-GP with immune modulators [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2267.

Deep neural network based histological scoring of lung fibrosis and inflammation in the mouse model system

Preclinical studies of novel compounds rely on quantitative readouts from animal models. Frequently employed readouts from histopathological tissue scoring are time consuming, require highly specialized staff and are subject to inherent variability. Recent advances in deep convolutional neural networks (CNN) now allow automating such scoring tasks. Here, we demonstrate this for the case of the Ashcroft fibrosis score and a newly developed inflammation score to characterize fibrotic and inflammatory lung diseases. Sections of lung tissue from mice exhibiting a wide range of fibrotic and inflammatory states were stained with Masson trichrome. Whole slide scans using a 20x objective were acquired and cut into smaller tiles of 512x512 pixels. The tiles were subsequently classified by specialized CNNs, either an "Ashcroft fibrosis CNN" or an "inflammation CNN". For the Ashcroft fibrosis score the CNN was fine-tuned by using 14000 labelled tiles. For the inflammation score the CNN was trained with 3500 labelled tiles. After training, the Ashcroft fibrosis CNN achieved an accuracy of 79.5% and the inflammation CNN an accuracy of 80.0%. An error analysis revealed that misclassifications are almost exclusively with neighboring scores, which reflects the inherent ambiguity of parts of the data. The variability between two experts was found to be larger than the variability between the CNN classifications and the ground truth. The CNN generated Ashcroft score was in very good agreement with the score of a pathologist (r2 = 0.92). Our results demonstrate that costly and time consuming scoring tasks can be automated and standardized with deep learning. New scores such as the inflammation score can be easily developed with the approach presented here.

Targeting the dopamine D1 receptor or its downstream signalling by inhibiting phosphodiesterase-1 improves cognitive performance

Background and Purpose

Insufficient prefrontal dopamine 1 (D₁) receptor signalling has been linked to cognitive dysfunction in several psychiatric conditions. Because the PDE1 isoform B (PDE1B) is postulated to regulate D₁ receptor‐dependent signal transduction, in this study we aimed to elucidate the role of PDE1 in cognitive processes reliant on D₁ receptor function.

Experimental Approach

Cognitive performance of the D₁ receptor agonist, SKF38393, was studied in the T‐maze continuous alternation task and 5‐choice serial reaction time task. D₁ receptor/PDE1B double‐immunohistochemistry was performed using human and rat prefrontal brain sections. The pharmacological activity of the PDE1 inhibitor, ITI‐214, was assessed by measuring the increase in cAMP/cGMP in prefrontal brain tissue and its effect on working memory performance. Mechanistic studies on the modulation of prefrontal neuronal transmission by SKF38393 and ITI‐214 were performed using extracellular recordings in brain slices.

Key Results

SKF38393 improved working memory and attentional performance in rodents. D₁ receptor/PDE1B co‐expression was verified in both human and rat prefrontal brain sections. The pharmacological activity of ITI‐214 on its target, PDE1, was demonstrated by its ability to increase prefrontal cAMP/cGMP. In addition, ITI‐214 improved working memory performance. Both SKF38393 and ITI‐214 facilitated neuronal transmission in prefrontal brain slices.

Conclusion and Implications

We hypothesize that PDE1 inhibition improves working memory performance by increasing prefrontal synaptic transmission and/or postsynaptic D₁ receptor signalling, by modulating prefrontal downstream second messenger levels. These data, therefore, support the use of PDE1 inhibitors as a potential approach for the treatment of cognitive dysfunction.

Characterization of the properties of a selective, orally bioavailable autotaxin inhibitor in preclinical models of advanced stages of liver fibrosis

BACKGROUND AND PURPOSE

Autotaxin (ATX) is a secreted phospholipase which hydrolyses lysophosphatidylcholine to generate lysophosphatidic acid (LPA). The extracellular signalling molecule LPA exerts its biological actions through activation of six GPCRs expressed in various cell types including fibroblasts. Multiple preclinical studies using knockout animals, LPA receptor antagonists or ATX inhibitors have provided evidence for a potential role of the ATX/LPA axis in tissue fibrosis. Despite growing evidence for a correlation between ATX levels and the degree of fibrosis in chronic liver diseases, including viral hepatitis and hepatocellular carcinoma, the role of ATX in non-alcoholic steatohepatitis (NASH) remains unclear.

EXPERIMENTAL APPROACH

The relevance of ATX in the pathogenesis of liver fibrosis was investigated by oral administration of Ex_31, a selective ATX inhibitor, in a 10 week model of carbon tetrachloride-induced liver injury and in a 14 week model of choline-deficient amino acid-defined diet-induced liver injury in rats.

KEY RESULTS

Oral administration of Ex_31, a selective ATX inhibitor, at 15 mg·kg^-1 twice daily in therapeutic intervention mode resulted in efficient ATX inhibition and more than 95% reduction in plasma LPA levels in both studies. Treatment with Ex_31 had no effect on biomarkers of liver function, inflammation, or fibrosis and did not result in histological improvements in diseased animals.

CONCLUSIONS AND IMPLICATIONS

Our findings question the role of ATX in the pathogenesis of hepatic fibrosis and the potential of small molecule ATX inhibitors for the treatment of patients with NASH and advanced stages of liver fibrosis.

Quantification of Pulmonary Fibrosis in a Bleomycin Mouse Model Using Automated Histological Image Analysis

Current literature on pulmonary fibrosis induced in animal models highlights the need of an accurate, reliable and reproducible histological quantitative analysis. One of the major limits of histological scoring concerns the fact that it is observer-dependent and consequently subject to variability, which may preclude comparative studies between different laboratories. To achieve a reliable and observer-independent quantification of lung fibrosis we developed an automated software histological image analysis performed from digital image of entire lung sections. This automated analysis was compared to standard evaluation methods with regard to its validation as an end-point measure of fibrosis. Lung fibrosis was induced in mice by intratracheal administration of bleomycin (BLM) at 0.25, 0.5, 0.75 and 1 mg/kg. A detailed characterization of BLM-induced fibrosis was performed 14 days after BLM administration using lung function testing, micro-computed tomography and Ashcroft scoring analysis. Quantification of fibrosis by automated analysis was assessed based on pulmonary tissue density measured from thousands of micro-tiles processed from digital images of entire lung sections. Prior to analysis, large bronchi and vessels were manually excluded from the original images. Measurement of fibrosis has been expressed by two indexes: the mean pulmonary tissue density and the high pulmonary tissue density frequency. We showed that tissue density indexes gave access to a very accurate and reliable quantification of morphological changes induced by BLM even for the lowest concentration used (0.25 mg/kg). A reconstructed 2D-image of the entire lung section at high resolution (3.6 μm/pixel) has been performed from tissue density values allowing the visualization of their distribution throughout fibrotic and non-fibrotic regions. A significant correlation (p<0.0001) was found between automated analysis and the above standard evaluation methods. This correlation establishes automated analysis as a novel end-point measure of BLM-induced lung fibrosis in mice, which will be very valuable for future preclinical drug explorations.

Three-dimensional accurate detection of lung emphysema in rats using ultra-short and zero echo time MRI

Emphysema is a life-threatening pathology that causes irreversible destruction of alveolar walls. In vivo imaging techniques play a fundamental role in the early non-invasive pre-clinical and clinical detection and longitudinal follow-up of this pathology. In the present study, we aimed to evaluate the feasibility of using high resolution radial three-dimensional (3D) zero echo time (ZTE) and 3D ultra-short echo time (UTE) MRI to accurately detect lung pathomorphological changes in a rodent model of emphysema.Porcine pancreas elastase (PPE) was intratracheally administered to the rats to produce the emphysematous changes. 3D ZTE MRI, low and high definition 3D UTE MRI and micro-computed tomography images were acquired 4 weeks after the PPE challenge. Signal-to-noise ratios (SNRs) were measured in PPE-treated and control rats. T2* values were computed from low definition 3D UTE MRI. Histomorphometric measurements were made after euthanizing the animals. Both ZTE and UTE MR images showed a significant decrease in the SNR measured in PPE-treated lungs compared with controls, due to the pathomorphological changes taking place in the challenged lungs. A significant decrease in T2* values in PPE-challenged animals compared with controls was measured using UTE MRI. Histomorphometric measurements showed a significant increase in the mean linear intercept in PPE-treated lungs. UTE yielded significantly higher SNR compared with ZTE (14% and 30% higher in PPE-treated and non-PPE-treated lungs, respectively).This study showed that optimized 3D radial UTE and ZTE MRI can provide lung images of excellent quality, with high isotropic spatial resolution (400 µm) and SNR in parenchymal tissue (>25) and negligible motion artifacts in freely breathing animals. These techniques were shown to be useful non-invasive instruments to accurately and reliably detect the pathomorphological alterations taking place in emphysematous lungs, without incurring the risks of cumulative radiation exposure typical of micro-computed tomography.

Bewegungsstörungen der Hinterhand bei Miniaturschweinen aus Hobbyhaltung

Gegenstand und Ziel: Beschrieben werden der Verlauf der klinischen Symptome und die histopathologischen Befunde von vier adulten Miniaturschweinen mit Bewegungsstörungen der Hinterhand. Anamnese: Die Tiere zeigten zum Zeitpunkt der Einlieferung in die Klinik eine unphysiologische Bewegung der Hintergliedmaßen durch extrem weites und hohes Unter-den-Bauch-Führen der Extremitäten, einen verzögerten Stellreflex der Vorder- und Hintergliedmaßen, einen verzögerten (konsensuellen) Pupillarreflex sowie eine borkig-krustig veränderte Haut im Rückenbereich. Die Hautsensibilität war generell reduziert. Ergebnisse: Die histopathologische Untersuchung ergab unter anderem eine großvakuoläre Degeneration bzw. spongiforme Auflockerung der Substantia (S.) alba im Gehirn und eine Ödematisierung der S. alba sowie eine Ballonierung der Myelinscheiden im Rückenmark. Außerdem waren eine meist hochgradige Hämosiderose der Milz und Leber sowie arteriosklerotische Gefäßveränderungen erkennbar. Schlussfolgerung: Diese histologischen Befunde weisen auf einen Vitamin- B-Mangel hin. Eine Beurteilung der Ätiologie und der Pathogenese ist jedoch nur eingeschränkt möglich. Der Nachweis eines Vitaminmangels am lebenden Tier kann sehr schwierig sein, da nur eine gezielte Bestimmung einzelner Vitamine im Blut erfolgen kann und es wenige Referenzwerte gibt. Eine Bestimmung des Vitamingehalts in Futtermitteln ist ebenfalls sehr aufwendig und zudem teuer. Häufig lässt sich nur eine Verdachtsdiagnose anhand der klinischen Symptome und über den Ausschluss infektiöser oder toxikologischer Ursachen stellen. Klinische Relevanz: Miniaturschweine werden immer häufiger als Haustiere gehalten. Die zum Teil mangelhaften Kenntnisse der Besitzer über Haltung und Fütterung von Schweinen führen zu verschiedenen Krankheitsbildern bei Miniaturschweinen, die in der konventionellen Schweinehaltung nur selten eine Rolle spielen. Dies sollte bei der Anamnese sowie bei der Diagnostik berücksichtigt werden und gegebenenfalls in die Therapie mit einbezogen werden.

[The incidence of bacterial CNS infections in roe deer (Capreolus capreolus), red deer (Cervus elaphus) and chamois (Rupicapra rupicapra) in Bavaria]

Brain samples of 849 wild ruminants (654 roe deer, 189 red deer and 6 chamois) from Bavaria were examined for the occurrence of encephalopathies caused by bacteria, using cultural, serological and genetic methods. In addition, 87 brain samples were investigated histologically for clarification of the pathogenetic relevance of specific microorganisms. Using conventional bacteriological methods, 464 different bacteria were isolated. 229 of them could be differentiated to the genus level and 235 to the species level. Totally, 35 different bacteria species were isolated, most frequently Micrococcus spp., Bacillus spp. and E. coli. Listeria spp. were detected in 43 brain samples (37 from roe deer, 5 from red deer and 1 from chamois). Sixteen strains were identified as L. innocua, 14 as L. monocytogenes, 9 as L. seeligeri and 4 as L. grayi. Serological investigations of L. monocytogenes showed that 9 strains belong to serotype 1/2a and five to 4b. Analysis of the geographical distribution of the Listeria findings indicate a statistically significant (p<0.011) regional aggregation in Unterfranken (prevalence for roe deer: 12.2%, versus 4.5% in Oberbayern-Schwaben, 6.1% in Niederbayern-Oberpfalz and 0% in Oberfranken-Mittelfranken). The histological investigation (HE staining) of 87 tissue samples contaminated with encephalitis relevant bacteria showed inflammation of different severity (mild meningitis and choroiditis (n = 26) to moderate (meningo)encephalitis (n = 13)) in 41 cases.

Neuropathological findings in brains of Bavarian cattle clinically suspected of bovine spongiform encephalopathy

The brains of 26 Bavarian bovines clinically suspected of bovine spongiform encephalopathy (BSE) were the subject of a neuropathological evaluation containing histopathology and immunohistochemistry. Six animals tested positive for BSE. In these six brains severe histological lesions that correlated with previous reports from the United Kingdom were observed. Immunohistochemistry with prion protein (PrP(Sc)), glial fibrillary acidic protein (GFAP) and synaptophysin were conducted on the mid-brain containing the red nucleus. All BSE-positive brains stained positively for PrP(Sc), and no plaques were observed. The BSE-affected brains showed a substantially more intense staining pattern for GFAP in comparison with the control groups, some of which were diagnosed with severe neuropathological disorders. Synaptophysin staining on BSE-positive brains was substantially reduced in the neuropil of the mid-brain, especially in the red nucleus. Twenty animals tested negative for BSE. The most common diagnoses were listeriosis, viral infections of unknown aetiology, brain oedema and hypomagnesaemia. These disorders may represent the most important clinical differential diagnoses for BSE in Bavaria.

[The occurrence of transmissible spongiform encephalopathies in roe deer (Capreolus capreolus), red deer (Cervus elaphus) and chamois (Rupicapra rupicapra) in Bavaria]

Brain samples of 849 free-ranging ruminants (654 roe deer, 189 red deer and 6 chamois) from Bavaria were examined for TSE. In this respect, detections of PrPres were carried out by ELISA technique (BioRad) and immunohistochemistry using the monoclonal antibody (mAb) L42. Validation experiments of the ELISA technique for the detection of prionprotein from free-ranging ruminants showed that the examination of brains of wild ruminants lead to lower extinctions than that of bovine brain samples. Due to the fact that brain samples of 2 known CWD positive wapitis showed definite positive results, all samples were analysed by this test. There were no indications on the occurrence of TSE in any of the sample. In addition, immunohistochemical investigations of 10% of all samples did not show PrPres. Due to the large number of samples, the prevalence of TSE in Bavaria can be quoted under 0.5% for roe deer and under 1.5% for red deer with a certainty of 95%.

Equine herpesvirus type 1 (EHV-1) myeloencephalopathy: a case report

An outbreak of neurological disease occurred in a well-managed riding school. Ataxia and paresis were observed in several horses, five of which became recumbent and were euthanized. Post-mortem analysis revealed scattered haemorrhages along the spinal cord, that were reflected by multiple haemorrhagic foci on formalin-fixed sections, with the thoracic and lumbar segments being the most affected. Pathohistologically, perivascular mononuclear cuffing and axonal swelling, especially in the white matter, were evident. Parallel to the course of disease, alterations in myelin sheets and activation of astrocytes and microglial cells were also observed. Virological findings confirmed an acute equine herpesvirus type 1 infection and virus was isolated from the spinal cord of a 26-year-old mare.

Animal lectins as cell adhesion molecules

Protein-carbohydrate interaction is exploited in cell adhesion mechanisms besides the recognition of peptide motifs. The sugar code thus significantly contributes to the intriguing specificity of cellular selection of binding partners. Focusing on two classes of lectins (selectins and galectins), it is evident that their functionality for mediation of adhesive contacts is becoming increasingly appreciated, as is the integration of this type of interaction with other recognition modes to yield the noted specificity. The initial contact formation between leukocytes and activated endothelium makes use of selectins to guide lymphocyte trafficking. In addition to the three selectins which bind a distinct array of ligands, galectin-1 and galectin-3 and possibly other members of this family are involved in cell-cell or cell-matrix interactions. This review summarizes structural and functional aspects of these two classes of endogenous lectins relevant for cell adhesion.

Temporal and spatial regulation of expression of two galectins during kidney development of the chicken

Organogenesis and the establishment of the mature phenotype require an interplay between diverse recognition systems. Concerning protein-carbohydrate interactions, galectins are known to be involved in several extra- and intracellular functions. Due to the occurrence of two avian galectins in liver (chicken galectin-16 CG-16) and intestine (chicken galectin-14; CG-14) with different developmental regulation. the questions addressed are to what extent and where these galectins are present during chicken kidney development. Using Western blot analysis, the presence of both activities in tissue extracts was ascertained. A solid-phase assay showed peak levels at day 12 followed by a decline. A histochemical analysis was carried out in combination with routine staining. Epithelial cells of the mesonephric proximal tubules were immunoreactive in the cytoplasm for CG-14 from day 5 of incubation onwards. Additionally, epithelial cells of the metanephric collecting ducts were stained. For CG-16 a rather similar pattern of staining was seen, additional positivity in early glomerular podocytes being notable. At the electron microscopical level, a diffuse staining for CG-14 was seen in the cytoplasm, whereas immunoreactivity for CG-16 was observed mainly in mitochondria. These results demonstrate quantitative differences in the developmental regulation of the two avian galectins with obvious similarities in the cell-type pattern but with a disparate intracellular localisation profile.

Correspondence of gradual developmental increases of expression of galectin-reactive glycoconjugates with alterations of the total contents of the two differentially regulated galectins in chicken intestine and liver as indication for overlapping functions

The duplication of genes for recognition molecules and the ensuing diversification of the members of such families generate complex groups of homologous proteins. One example are galactoside-specific lectins whose sequences display constant features related to sugar binding, the galectins. Based on the inverse abundance of the chicken galectins CG-14 and CG-16 in adult intestine and liver, these two lectins represent a model to comparatively study expression of the related proteins and the galectin-reactive sites (glycoproteins and glycolipids) biochemically and histochemically. Functional overlap and/or acquisition of distinct functions would be reflected in qualitative and/or quantitative aspects of ligand display. Using five different stages of embryogenesis, differential regulation of the two galectins was detected in liver and intestine. The clear preference for one galectin (CG-14) was observed in intestine already at rather early stages, whereas equivalence for both proteins was noted in liver from day 12 to day 18 prior to hatching, as seen by ELISA assays and Western blot analysis. Presentation of galectin-reactive glycoproteins showed a tendency for gradual increase in both organs. Galectin-blotting analysis revealed primarily very similar patterns of positive bands at the different stages of development and only few quantitative and qualitative changes. The reactivity of glycolipids in a solid-phase assay was more variable, even surpassing the response of extracts of the adult organ at several embryonic stages. While the localization patterns of the galectins and galectin-reactive sites were nearly indistinguishable in the liver, intestinal tissue differed with respect to the placement and accessibility of binding sites. Thus, the results suggest a differential regulation of galectin activities in the two organs. As a sum they resemble the course of development of availability of glycoprotein ligands in vitro. These findings support the notion for a partial functional redundancy in this family. The described approach to employ galectin-specific antibodies and the labeled galectins as tools to assess presentation of ligands is suggested to be of general relevance to address the question of distinct vs. overlapping functions of related recognition molecules.

Growth factors and their receptors in the olfactory system

The olfactory epithelium is unique in the mammalian nervous system as it is a site of continual neurogenesis. Constant turnover of primary sensory neurons in the periphery results in continuous remodeling of neuronal circuits and synapses in the olfactory bulb throughout life. Most of the specific mechanisms and factors that control and modulate this process are not known. Recent studies suggest that growth factors, and their receptors, may play a crucial role in the development and continuous regeneration of olfactory neurons, i.e. particularly in neuronal proliferation, neurite outgrowth, fasciculation and synapse formation of the olfactory system. The potential role of the following factors and their receptors in different species are reviewed: Nerve growth factor (NGF); insulin-like growth factors (IGFs); fibroblast growth factors (FGFs); epidermal growth factor (EGF); transforming growth factor alpha (TGF alpha); amphiregulin (AR) and transforming growth factors beta (TGFs beta).