Quantification of lung fibrosis and emphysema in mice using automated micro-computed tomography

Ziziphus spina-christi L. extract attenuates bleomycin-induced lung fibrosis in mice via regulating TGF-β1/SMAD pathway: LC-MS/MS Metabolic profiling, chemical composition, and histology studies

Ancient Egyptians (including Bedouins and Nubians) have long utilized Ziziphus spina-christi (L.), a traditional Arabian medicinal herb, to alleviate swellings and inflammatory disorders. It is also mentioned in Christian and Muslim traditions. Ziziphus spina-christi L. (Family: Rhamnaceae) is a plentiful source of polyphenols, revealing free radical scavenging, antioxidant, metal chelating, cytotoxic, and anti-inflammatory activities. Herein, different classes of the existing bioactive metabolites in Z. spina-christi L. were detected using liquid chromatography-tandem mass spectrometry (LC-MS/MS) for the first time. The study also aimed to assess the anti-inflammatory and antifibrotic properties of Z. spina-christi L. extract against bleomycin-induced lung fibrosis in an experimental mouse model. 32 male Swiss Albino mice were assigned into 4 groups; the first and second were the normal control group and the bleomycin positive control (single 2.5 U/kg bleomycin intratracheal dose). The third and fourth groups received 100 and 200 mg/kg/day Z. spina-christi L. extract orally for 3 weeks, 2 weeks before bleomycin, and 1 week after. The bioactive metabolites in Z. spina-christi L. extract were identified as phenolic acids, catechins, flavonoids, chalcones, stilbenes, triterpenoid acids, saponins, and sterols. The contents of total phenolic compounds and flavonoids were found to be 196.62 mg GAE/gm and 33.29 mg QE/gm, respectively. In the experimental study, histopathological examination revealed that lung fibrosis was attenuated in both Z. spina-christi L.- treated groups. Z. spina-christi L. extract downregulated the expression of nuclear factor kappa B (NF-κB) p65 and decreased levels of the inflammatory markers tumor necrosis factor-alpha (TNF-α), monocyte chemoattractant protein-1 (MCP-1), and c-Jun N-terminal kinase (JNK) in lung tissue. Z. spina-christi L. also downregulated the expression of the fibrotic parameters collagen-1, alpha-smooth muscle actin (α-SMA), transforming growth factor-beta 1 (TGF-β1), matrix metalloproteinase-9 (MMP-9) and SMAD3, with upregulation of the antifibrotic SMAD7 in lung tissue. Overall, the present study suggests a potential protective effect of Z. spina-christi L. extract against bleomycin-induced lung fibrosis through regulation of the TGF-β1/SMAD pathway.

Microscopic computed tomography with AI-CNN-powered image analysis: the path to phenotype bleomycin-induced lung injury

Bleomycin (BLM)-induced lung injury in mice is a valuable model for investigating the molecular mechanisms that drive inflammation and fibrosis and for evaluating potential therapeutic approaches to treat the disease. Given high variability in the BLM model, it is critical to accurately phenotype the animals in the course of an experiment. In the present study, we aimed to demonstrate the utility of microscopic computed tomography (µCT) imaging combined with an artificial intelligence (AI)-convolutional neural network (CNN)-powered lung segmentation for rapid phenotyping of BLM mice. µCT was performed in freely breathing C57BL/6J mice under isoflurane anesthesia on days 7 and 21 after BLM administration. Terminal invasive lung function measurement and histological assessment of the left lung collagen content were conducted as well. µCT image analysis demonstrated gradual and time-dependent development of lung injury as evident by alterations in the lung density, air-to-tissue volume ratio, and lung aeration in mice treated with BLM. The right and left lung were unequally affected. µCT-derived parameters such as lung density, air-to-tissue volume ratio, and nonaerated lung volume correlated well with the invasive lung function measurement and left lung collagen content. Our study demonstrates the utility of AI-CNN-powered µCT image analysis for rapid and accurate phenotyping of BLM mice in the course of disease development and progression.NEW & NOTEWORTHY Microscopic computed tomography (µCT) imaging combined with an artificial intelligence (AI)-convolutional neural network (CNN)-powered lung segmentation is a rapid and powerful tool for noninvasive phenotyping of bleomycin mice over the course of the disease. This, in turn, allows earlier and more reliable identification of therapeutic effects of new drug candidates, ultimately leading to the reduction of unnecessary procedures in animals in pharmacological research.

The nature of chronic rejection after lung transplantation: a murine orthotopic lung transplant study

Introduction

Chronic rejection is a major complication post-transplantation. Within lung transplantation, chronic rejection was considered as airway centred. Chronic Lung Allograft Dysfunction (CLAD), defined to cover all late chronic complications, makes it more difficult to understand chronic rejection from an immunological perspective. This study investigated the true nature, timing and location of chronic rejection as a whole, within mouse lung transplantation.

Methods

40 mice underwent an orthotopic left lung transplantation, were sacrificed at day 70 and evaluated by histology and in vivo µCT. For timing and location of rejection, extra grafts were sacrificed at day 7, 35, 56 and investigated by ex vivo µCT or single cell RNA (scRNA) profiling.

Results

Chronic rejection originated as innate inflammation around small arteries evolving toward adaptive organization with subsequent end-arterial fibrosis and obliterans. Subsequently, venous and pleural infiltration appeared, followed by airway related bronchiolar folding and rarely bronchiolitis obliterans was observed. Ex vivo µCT and scRNA profiling validated the time, location and sequence of events with endothelial destruction and activation as primary onset.

Conclusion

Against the current belief, chronic rejection in lung transplantation may start as an arterial response, followed by responses in venules, pleura, and, only in the late stage, bronchioles, as may be seen in some but not all patients with CLAD.

Multiphase micro-computed tomography reconstructions provide dynamic respiratory function in a mouse lung fibrosis model

Micro-computed tomography derived functional biomarkers used in lung disease research can significantly complement end-stage histomorphometric measures while also allowing for longitudinal studies. However, no approach for visualizing lung dynamics across a full respiratory cycle has yet been described. Using bleomycin-induced lung fibrosis and the antifibrotic drug nintedanib as a test model, we implemented a four-dimensional (4D) micro-CT imaging approach consisting of 30 reconstructed volumes per respiratory cycle, coupled with deep-learning-assisted segmentation of lung volumes. 4D micro-CT provided an accurate description of inhalatory and exhalatory lung dynamics under resting conditions and revealed an inflammation-related obstructive pattern at day 7, followed by a restrictive pattern associated with fibrosis development at day 21. A milder restriction and fibrotic pathology resulted from nintedanib treatment. The similarity of 4D micro-CT data with those produced by diagnostic measurements, also points to its great potential as an exploratory tool for the discovery of clinically relevant therapeutic compounds.

Myeloid Heterogeneity Mediates Acute Exacerbations of Pulmonary Fibrosis

Epidemiological evidence indicates that exposure to particulate matter is linked to the development of idiopathic pulmonary fibrosis (IPF) and increases the incidence of acute exacerbations of IPF. In addition to accelerating the rate of lung function decline, exposure to fine particulate matter (particulate matter smaller than 2.5 μm [PM2.5]) is a risk factor for increased mortality in subjects with IPF. In this article, we show that exposure to PM2.5 mediates monocyte recruitment and fibrotic progression in mice with established fibrosis. In mice with established fibrosis, bronchoalveolar lavage cells showed monocyte/macrophage heterogeneity after exposure to PM2.5. These cells had a significant inflammatory and anti-inflammatory signature. The mixed heterogeneity of cells contributed to the proinflammatory and anti-inflammatory response. Although monocyte-derived macrophages were recruited to the lung in bleomycin-injured mice treated with PM2.5, recruitment of monocytes expressing Ly6Chi to the lung promoted progression of fibrosis, reduced lung aeration on computed tomography, and impacted lung compliance. Ly6Chi monocytes isolated from PM2.5-exposed fibrotic mice showed enhanced expression of proinflammatory markers compared with fibrotic mice exposed to vehicle. Moreover, IPF bronchoalveolar lavage cells treated ex vivo with PM2.5 showed an exaggerated inflammatory response. Targeting Ly6Chi monocyte recruitment inhibited fibrotic progression in mice. Moreover, the adoptive transfer of Ly6Chi monocytes exacerbated established fibrosis. These observations suggest that enhanced recruitment of Ly6Chi monocytes with a proinflammatory phenotype mediates acute exacerbations of pulmonary fibrosis, and targeting these cells may provide a potential novel therapeutic target to protect against acute exacerbations of IPF.

Disruption of extracellular redox balance drives persistent lung fibrosis and impairs fibrosis resolution

Lung fibrosis is a devastating outcome of various diffuse parenchymal lung diseases. Despite rigorous research efforts, the mechanisms that propagate its progressive and nonresolving nature remain enigmatic. Oxidative stress has been implicated in the pathogenesis of lung fibrosis. However, the role of extracellular redox state in disease progression and resolution remains largely unexplored. Here, we show that compartmentalized control over extracellular reactive oxygen species (ROS) by aerosolized delivery of recombinant extracellular superoxide dismutase (ECSOD) suppresses an established bleomycin-induced fibrotic process in mice. Further analysis of publicly available microarray, RNA-seq and single-cell RNAseq datasets reveals a significant decrease in ECSOD expression in fibrotic lung tissues that can be spontaneously restored during fibrosis resolution. Therefore, we investigate the effect of siRNA-mediated ECSOD depletion during the established fibrotic phase on the self-limiting nature of the bleomycin mouse model. Our results demonstrate that in vivo knockdown of ECSOD in mouse fibrotic lungs impairs fibrosis resolution. Mechanistically, we demonstrate that transforming growth factor (TGF)-β1 downregulates endogenous ECSOD expression, leading to the accumulation of extracellular superoxide via Smad-mediated signaling and the activation of additional stores of latent TGF-β1. In addition, depletion of endogenous ECSOD during the fibrotic phase in the bleomycin model induces an apoptosis-resistant phenotype in lung fibroblasts through unrestricted Akt signaling. Taken together, our data strongly support the critical role of extracellular redox state in fibrosis persistence and resolution. Based on these findings, we propose that compartment-specific control over extracellular ROS may be a potential therapeutic strategy for managing fibrotic lung disorders.

Nanoceria as Safe Contrast Agents for X-ray CT Imaging

Cerium oxide nanoparticles (CeO2NPs) have exceptional catalytic properties, rendering them highly effective in removing excessive reactive oxygen species (ROS) from biological environments, which is crucial in safeguarding these environments against radiation-induced damage. Additionally, the Ce atom's high Z number makes it an ideal candidate for utilisation as an X-ray imaging contrast agent. We herein show how the injection of albumin-stabilised 5 nm CeO2NPs into mice revealed substantial enhancement in X-ray contrast, reaching up to a tenfold increase at significantly lower concentrations than commercial or other proposed contrast agents. Remarkably, these NPs exhibited prolonged residence time within the target organs. Thus, upon injection into the tail vein, they exhibited efficient uptake by the liver and spleen, with 85% of the injected dose (%ID) recovered after 7 days. In the case of intratumoral administration, 99% ID of CeO2NPs remained within the tumour throughout the 7-day observation period, allowing for observation of disease dynamics. Mass spectrometry (ICP-MS) elemental analysis confirmed X-ray CT imaging observations.

Magnetic resonance imaging and ultrasound elastography in the context of preclinical pharmacological research: significance for the 3R principles

The 3Rs principles-reduction, refinement, replacement-are at the core of preclinical research within drug discovery, which still relies to a great extent on the availability of models of disease in animals. Minimizing their distress, reducing their number as well as searching for means to replace them in experimental studies are constant objectives in this area. Due to its non-invasive character in vivo imaging supports these efforts by enabling repeated longitudinal assessments in each animal which serves as its own control, thereby enabling to reduce considerably the animal utilization in the experiments. The repetitive monitoring of pathology progression and the effects of therapy becomes feasible by assessment of quantitative biomarkers. Moreover, imaging has translational prospects by facilitating the comparison of studies performed in small rodents and humans. Also, learnings from the clinic may be potentially back-translated to preclinical settings and therefore contribute to refining animal investigations. By concentrating on activities around the application of magnetic resonance imaging (MRI) and ultrasound elastography to small rodent models of disease, we aim to illustrate how in vivo imaging contributes primarily to reduction and refinement in the context of pharmacological research.

Targeting pathogenic macrophages by the application of SHP-1 agonists reduces inflammation and alleviates pulmonary fibrosis

Idiopathic pulmonary fibrosis is a progressive fibrotic disorder with no cure that is characterized by deterioration of lung function. Current FDA-approved drugs for IPF delay the decline in lung function, but neither reverse fibrosis nor significantly improve overall survival. SHP-1 deficiency results in hyperactive alveolar macrophages accumulating in the lung, which contribute to the induction of pulmonary fibrosis. Herein, we investigated whether employing a SHP-1 agonist ameliorates pulmonary fibrosis in a bleomycin-induced pulmonary fibrosis murine model. Histological examination and micro-computed tomography images showed that SHP-1 agonist treatment alleviates bleomycin-induced pulmonary fibrosis. Reduced alveolar hemorrhage, lung inflammation, and collagen deposition, as well as enhanced alveolar space, lung capacity, and improved overall survival were observed in mice administered the SHP-1 agonist. The percentage of macrophages collected from bronchoalveolar lavage fluid and circulating monocytes in bleomycin-instilled mice were also significantly reduced by SHP-1 agonist treatment, suggesting that the SHP-1 agonist may alleviate pulmonary fibrosis by targeting macrophages and reshaping the immunofibrotic niche. In human monocyte-derived macrophages, SHP-1 agonist treatment downregulated CSF1R expression and inactivated STAT3/NFκB signaling, culminating in inhibited macrophage survival and perturbed macrophage polarization. The expression of pro-fibrotic markers (e.g., MRC1, CD200R1, and FN1) by IL4/IL13-induced M2 macrophages that rely on CSF1R signaling for their fate-determination was restricted by SHP-1 agonist treatment. While M2-derived medium promoted the expression of fibroblast-to-myofibroblast transition markers (e.g., ACTA2 and COL3A1), the application of SHP-1 agonist reversed the transition in a dose-dependent manner. Our report indicates that pharmacological activation of SHP-1 ameliorates pulmonary fibrosis via suppression of CSF1R signaling in macrophages, reduction of pathogenic macrophages, and the inhibition of fibroblast-to-myofibroblast transition. Our study thus identifies SHP-1 as a druggable target for the treatment of IPF, and suggests that the SHP-1 agonist may be developed as an anti-pulmonary fibrosis medication that both suppresses inflammation and restrains fibroblast-to-myofibroblast transition.

The longitudinal and regional analysis of bleomycin-induced pulmonary fibrosis in mice by microcomputed tomography

Introduction

Microcomputed tomography (micro-CT) is powerful for assessment of the progression of lung fibrosis in animal model, but current whole lung analysis (WLA) methods are time-consuming. Here, a longitudinal and regional analysis (LRA) method was developed to assess fibrosis easily and quickly by micro-CT.

Method

Firstly, we investigated the distribution pattern of lesions in BLM-induced pulmonary fibrosis mice. Then, the VOIs for LRA were selected based on the anatomical locations and we compared the robustness, accuracy, repeatability, analysis time of LRA to WLA. Additionally, LRA was applied to assess different stages of pulmonary fibrosis, and was validated with conventional endpoint measurements (such as lung hydroxyproline and histopathology).

Results

The lesions of fibrosis in 66 bleomycin (BLM)-induced pulmonary fibrosis mice were mostly in the middle and upper parts of lungs. By applying LRA, the percentages of high-density voxels in selected volumes of interest (VOIs) were well correlated with that in WLA both at Day 7 and Day 21 after bleomycin induction (R² = 0.8784 and 0.8464, respectively). The relative standard deviation (RSD) of the percentage of high-density voxels in the VOIs was lower than that of WLA (P < 0.05). The cost time of LRA was shorter than that of WLA (P < 0.05) and the accuracy of LRA was further confirmed by the histological analysis and biochemical quantification of hydroxyproline.

Conclusion

LRA is probably an easier and more time-saving method to assess fibrosis formation and evaluate treatment efficacy.

Micro-CT-derived ventilation biomarkers for the longitudinal assessment of pathology and response to therapy in a mouse model of lung fibrosis

Experimental in-vivo animal models are key tools to investigate the pathogenesis of lung disease and to discover new therapeutics. Histopathological and biochemical investigations of explanted lung tissue are currently considered the gold standard, but they provide space-localized information and are not amenable to longitudinal studies in individual animals. Here, we present an imaging procedure that uses micro-CT to extract morpho-functional indicators of lung pathology in a murine model of lung fibrosis. We quantified the decrease of lung ventilation and measured the antifibrotic effect of Nintedanib. A robust structure-function relationship was revealed by cumulative data correlating micro-CT with histomorphometric endpoints. The results highlight the potential of in-vivo micro-CT biomarkers as novel tools to monitor the progression of inflammatory and fibrotic lung disease and to shed light on the mechanism of action of candidate drugs. Our platform is also expected to streamline translation from preclinical studies to human patients.

Application-specific approaches to MicroCT for evaluation of mouse models of pulmonary disease

The advent of micro-computed tomography (microCT) has provided significant advancement in our ability to generate clinically relevant assessments of lung health and disease in small animal models. As microCT use to generate outcomes analysis in pulmonary preclinical models has increased there have been substantial improvements in image quality and resolution, and data analysis software. However, there are limited published methods for standardized imaging and automated analysis available for investigators. Manual quantitative analysis of microCT images is complicated by the presence of inflammation and parenchymal disease. To improve the efficiency and limit user-associated bias, we have developed an automated pulmonary air and tissue segmentation (PATS) task list to segment lung air volume and lung tissue volume for quantitative analysis. We demonstrate the effective use of the PATS task list using four distinct methods for imaging, 1) in vivo respiration controlled scanning using a flexiVent, 2) longitudinal breath-gated in vivo scanning in resolving and non-resolving pulmonary disease initiated by lipopolysaccharide-, bleomycin-, and silica-exposure, 3) post-mortem imaging, and 4) ex vivo high-resolution scanning. The accuracy of the PATS task list was compared to manual segmentation. The use of these imaging techniques and automated quantification methodology across multiple models of lung injury and fibrosis demonstrates the broad applicability and adaptability of microCT to various lung diseases and small animal models and presents a significant advance in efficiency and standardization of preclinical microCT imaging and analysis for the field of pulmonary research.

Lung function measurements in preclinical research: What has been done and where is it headed?

Due to the close interaction of lung morphology and functions, repeatable measurements of pulmonary function during longitudinal studies on lung pathophysiology and treatment efficacy have been a great area of interest for lung researchers. Spirometry, as a simple and quick procedure that depends on the maximal inspiration of the patient, is the most common lung function test in clinics that measures lung volumes against time. Similarly, in the preclinical area, plethysmography techniques offer lung functional parameters related to lung volumes. In the past few decades, many innovative techniques have been introduced for in vivo lung function measurements, while each one of these techniques has their own advantages and disadvantages. Before each experiment, depending on the sensitivity of the required pulmonary functional parameters, it should be decided whether an invasive or non-invasive approach is desired. On one hand, invasive techniques offer sensitive and specific readouts related to lung mechanics in anesthetized and tracheotomized animals at endpoints. On the other hand, non-invasive techniques allow repeatable lung function measurements in conscious, free-breathing animals with readouts related to the lung volumes. The biggest disadvantage of these standard techniques for lung function measurements is considering the lung as a single unit and providing only global readouts. However, recent advances in lung imaging modalities such as x-ray computed tomography and magnetic resonance imaging opened new doors toward obtaining both anatomical and functional information from the same scan session, without the requirement for any extra pulmonary functional measurements, in more regional and non-invasive manners. Consequently, a new field of study called pulmonary functional imaging was born which focuses on introducing new techniques for regional quantification of lung function non-invasively using imaging-based techniques. This narrative review provides first an overview of both invasive and non-invasive conventional methods for lung function measurements, mostly focused on small animals for preclinical research, including discussions about their advantages and disadvantages. Then, we focus on those newly developed, non-invasive, imaging-based techniques that can provide either global or regional lung functional readouts at multiple time-points.

Blockade of the pentraxin 3/CD44 interaction attenuates lung injury-induced fibrosis

BACKGROUND

Fibrosing interstitial lung diseases (fILD) are potentially fatal with limited therapeutic options and no effective strategies to reverse fibrogenesis. Myofibroblasts are chief effector cells in fibrosis that excessively deposit collagen in the pulmonary interstitium and lead to progressive impairment of gaseous exchange.

METHODS

Plasma and lung specimens from patients with fILD were applied for detecting pentraxin 3 (PTX3) abundance by ELISA and Immunohistochemistry. Masson's trichrome and Sirius red stains and hydroxyproline assay were performed for assessing collagen accumulation in the lungs of bleomycin-exposed conditional Ptx3-deficient and PTX3-neutralizing antibody (αPTX3i)-treated mice. Downstream effectors including signaling pathways and fibrotic genes were examined for assessing CD44-involved PTX3-induced fibrosis in HFL1 and primary mouse fibroblasts.

RESULTS

PTX3 was upregulated in the lungs and plasma of bleomycin-exposed mice and correlated with disease severity and adverse outcomes in fILD patients. Decreased collagen accumulation, attenuation of alveolar fibrosis and fibrotic markers, and improved lung function were observed in bleomycin-exposed conditional Ptx3-deficient mice. PTX3 activates lung fibroblasts to differentiate towards migrative and highly collagen-expressing myofibroblasts. Lung fibroblasts with CD44 inactivation attenuated the PI3K-AKT1, NF-κB, and JNK signaling pathways and fibrotic markers. αPTX3i mimic-based therapeutic studies demonstrated abrogation of the migrative fibroblast phenotype and myofibroblast activation in vitro. Notably, αPTX3i inhibited lung fibrosis, reduced collagen deposition, increased mouse survival, and improved lung function in bleomycin-induced pulmonary fibrosis.

CONCLUSIONS

The present study reveals new insights into the involvement of the PTX3/CD44 axis in fibrosis and suggests PTX3 as a promising therapeutic target in fILD patients.

Lung Volume Calculation in Preclinical MicroCT: A Fast Geometrical Approach

In this study, we present a time-efficient protocol for thoracic volume calculation as a proxy for total lung volume. We hypothesize that lung volume can be calculated indirectly from this thoracic volume. We compared the measured thoracic volume with manually segmented and automatically thresholded lung volumes, with manual segmentation as the gold standard. A linear regression formula was obtained and used for calculating the theoretical lung volume. This volume was compared with the gold standard volumes. In healthy animals, thoracic volume was 887.45 mm³, manually delineated lung volume 554.33 mm³ and thresholded aerated lung volume 495.38 mm³ on average. Theoretical lung volume was 554.30 mm³. Finally, the protocol was applied to three animal models of lung pathology (lung metastasis and transgenic primary lung tumor and fungal infection). In confirmed pathologic animals, thoracic volumes were: 893.20 mm³, 860.12 and 1027.28 mm³. Manually delineated volumes were 640.58, 503.91 and 882.42 mm³, respectively. Thresholded lung volumes were 315.92 mm³, 408.72 and 236 mm³, respectively. Theoretical lung volume resulted in 635.28, 524.30 and 863.10.42 mm³. No significant differences were observed between volumes. This confirmed the potential use of this protocol for lung volume calculation in pathologic models.

The importance of routine quality control for reproducible pulmonary measurements by in vivo micro-CT

Micro-computed tomography (CT) imaging provides densitometric and functional assessment of lung diseases in animal models, playing a key role either in understanding disease progression or in drug discovery studies. The generation of reliable and reproducible experimental data is strictly dependent on a system's stability. Quality controls (QC) are essential to monitor micro-CT performance but, although QC procedures are standardized and routinely employed in clinical practice, detailed guidelines for preclinical imaging are lacking. In this work, we propose a routine QC protocol for in vivo micro-CT, based on three commercial phantoms. To investigate the impact of a detected scanner drift on image post-processing, a retrospective analysis using twenty-two healthy mice was performed and lung density histograms used to compare the area under curve (AUC), the skewness and the kurtosis before and after the drift. As expected, statistically significant differences were found for all the selected parameters [AUC 532 ± 31 vs. 420 ± 38 (p < 0.001); skewness 2.3 ± 0.1 vs. 2.5 ± 0.1 (p < 0.001) and kurtosis 4.2 ± 0.3 vs. 5.1 ± 0.5 (p < 0.001)], confirming the importance of the designed QC procedure to obtain a reliable longitudinal quantification of disease progression and drug efficacy evaluation.

Meleagrin Isolated from the Red Sea Fungus Penicillium chrysogenum Protects against Bleomycin-Induced Pulmonary Fibrosis in Mice

The Red Sea marine fungus Penicillium chrysogenum (Family: Ascomycota) comprises a panel of chemically diverse natural metabolites. A meleagrin alkaloid was isolated from deep-sediment-derived P. chrysogenum Strain S003 and has been reported to exert antibacterial and cytotoxic activities. The present study aimed to explore the therapeutic potential of meleagrin on pulmonary fibrosis. Lung fibrosis was induced in mice by a single intratracheal instillation of 2.5 mg/kg bleomycin. Mice were given 5 mg/kg meleagrin daily either for 3 weeks after bleomycin administration in the treatment group or 2 weeks before and 3 weeks after bleomycin administration in the protection group. Bleomycin triggered excessive ROS production, inflammatory infiltration, collagen overproduction and fibrosis. Bleomycin-induced pulmonary fibrosis was attenuated by meleagrin. Meleagrin was noted to restore the oxidant–antioxidant balance, as evidenced by lower MDA contents and higher levels of SOD and catalase activities and GSH content compared to the bleomycin group. Meleagrin also activated the Nrf2/HO-1 antioxidant signaling pathway and inhibited TLR4 and NF-κB gene expression, with a subsequent decreased release of pro-inflammatory cytokines (TNF-α, IL-6 and IFN-γ). Additionally, meleagrin inhibited bleomycin-induced apoptosis by abating the activities of pro-apoptotic proteins Bax and caspase-3 while elevating Bcl2. Furthermore, it suppressed the gene expression of α-SMA, TGF-β1, Smad-2, type I collagen and MMP-9, with a concomitant decrease in the protein levels of TGF-β1, α-SMA, phosphorylated Smad-2, MMP-9, elastin and fibronectin. This study revealed that meleagrin’s protective effects against bleomycin-induced pulmonary fibrosis are attributed to its antioxidant, anti-inflammatory, anti-apoptotic and antifibrotic properties. Notably, the use of meleagrin as a protective agent against bleomycin-induced lung fibrosis was more efficient than its use as a treatment agent.

Ferret models of alpha-1 antitrypsin deficiency develop lung and liver disease

Alpha-1 antitrypsin deficiency (AATD) is the most common genetic cause and risk factor for chronic obstructive pulmonary disease, but the field lacks a large-animal model that allows for longitudinal assessment of pulmonary function. We hypothesized that ferrets would model human AATD-related lung and hepatic disease. AAT-knockout (AAT-KO) and PiZZ (E342K, the most common mutation in humans) ferrets were generated and compared with matched controls using custom-designed flexiVent modules to perform pulmonary function tests, quantitative computed tomography (QCT), bronchoalveolar lavage (BAL) proteomics, and alveolar morphometry. Complete loss of AAT (AAT-KO) led to increased pulmonary compliance and expiratory airflow limitation, consistent with obstructive lung disease. QCT and morphometry confirmed emphysema and airspace enlargement, respectively. Pathway analysis of BAL proteomics data revealed inflammatory lung disease and impaired cellular migration. The PiZ mutation resulted in altered AAT protein folding in the liver, hepatic injury, and reduced plasma concentrations of AAT, and PiZZ ferrets developed obstructive lung disease. In summary, AAT-KO and PiZZ ferrets model the progressive obstructive pulmonary disease seen in AAT-deficient patients and may serve as a platform for preclinical testing of therapeutics including gene therapy.

[In-vivo Evaluation of Bleomycin-induced Lung Fibrosis Model Mouse Using Ultra High-field 7 T-MRI and Micro-CT]

PURPOSE

This study aimed to perform longitudinal observation using 4D-computed tomography (CT) and compare images acquired by 3D-CT and 3D-ultrashort echo time (UTE) for evaluation of bleomycin-induced lung fibrosis model.

METHOD

The pulmonary fibrosis model was induced by instilling intratracheally with 50 μl of bleomycin. 4D-CT images were classified into four phases after acquisition and analyzed. To study the effects of respiratory gating, we aquired 3D-CT and 3D-UTE images with and without respiratory gating. For comparison between CT and UTE images, we performed no-triggerd 3D-CT and 3D-UTE under free-breathing. MR signal intensity ratio and CT values were measured in three regions of the upper, middle, and lower lung.

RESULTS

At 4DCT, total lung volume at maximum inspiration (4th phase) decreased significantly compared with control mouse and the ratio of lung volume at inspiration to expiration also showed a significant decrease. In comparison of the images between with and without respiratory gating, clearer images were obtained by respiratory gating. However, there was no significant difference between both. In comparison between CT and UTE images, magnetic resonance (MR) signal intensity ratio and CT value were significantly correlated, but 3D-UTE images showed poor delineation of the lower lung and that near the diaphragm compared with 3D-CT images.

CONCLUSION

4D micro-CT and nontriggered 3D UTE-magnetic resonance imaging (MRI) under free breathing can be useful to evaluate bleomycininduced lung fibrosis model mouse.

Animal models of drug-induced pulmonary fibrosis: an overview of molecular mechanisms and characteristics

Idiopathic pulmonary fibrosis (IPF) is a progressive interstitial lung disease characterized by progressive loss of pulmonary function. Drug-induced interstitial lung disease has been reported as a severe adverse effect of some drugs, such as bleomycin, amiodarone, and methotrexate. Based on good characteristics, drug-induced pulmonary fibrosis (PF) animal model has played a key role in our understanding of the molecular mechanisms of PF pathogenesis and recapitulates the specific pathology in patients and helps develop therapeutic strategies. Here, we summarize the mechanisms and characteristics of given fibrotic drug-induced animal models for PFs. Together with the key publications describing these models, this brief but detailed overview would be helpful for the pharmacological research with animal models of PFs. Potential mechanisms underlying drug induced lung toxicity.

Feasibility of quantification of murine radiation-induced pulmonary fibrosis with microCT imaging

Mouse models of radiation-induced pulmonary fibrosis (RIPF) are commonly produced to find novel treatments for the condition. However, current models are not always assesed in a clinically-relevant manner. Clinics diagnose and track RIPF through CT scanning rather than observing time-to-death. An established timeline of RIPF lesion development in a murine model is therefore needed. Male C57Bl/6 mice (n=43) were irradiated with a single dose of 20 Gy to the whole thoracic area delivered by an 320 kV X-Rad cabinet irradiator. CT was performed with respitory gating at two week time points and developed images to identify RIPF pathology in vivo. Confirmation of CT findings was performed via histology on the lungs using Mason's trichrome staining. CT images were segmented to quantify fibrosis and lung which are then summed to give total volume. The fibrotic fraction was calculated upto 26 weeks. Significant increases in fibrotic fraction compared to the baseline microCT scans for each individual mouse acquired prior to the 20 Gy exposure are seen beginning at 10-12 weeks. Tidal lung volume was also calculated by subtracting expiration scan volumes from inspiration scan volumes. However the decrease in tidal lung volume over time was not statisitically significant. Computed tomography (CT) imaging was used to quantify the increase in fibrosis over time in our mouse model. However, the results were highly variable among individual mice after irradiation. CT imaging should be used in future studies looking at treatments for RIPF as it allows for measuring the extent of pathology non-invasively in a clinically-relevant manner.

In-vivo X-ray dark-field computed tomography for the detection of radiation-induced lung damage in mice

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Radiation-induced lung damage was observed using X-ray dark-field tomography.

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In this pre-clinical study, mouse lungs were irradiated and subsequently imaged.

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We report increased sensitivity of X-ray dark-field tomography over absorption-based tomography.

Background and Purpose

Radiotherapy of thoracic tumours can lead to side effects in the lung, which may benefit from early diagnosis. We investigated the potential of X-ray dark-field computed tomography by a proof-of-principle murine study in a clinically relevant radiotherapeutic setting aiming at the detection of radiation-induced lung damage.

Material and Methods

Six mice were irradiated with 20 Gy to the entire right lung. Together with five unirradiated control mice, they were imaged using computed tomography with absorption and dark-field contrast before and 16 weeks post irradiation. Mean pixel values for the right and left lung were calculated for both contrasts, and the right-to-left-ratio R of these means was compared. Radiologists also assessed the tomograms acquired 16 weeks post irradiation. Sensitivity, specificity, inter- and intra-reader accuracy were evaluated.

Results

In absorption contrast the group-average of R showed no increase in the control group and increased by 7% (p = 0.005) in the irradiated group. In dark-field contrast, it increased by 2% in the control group and by 14% (p = 0.005) in the irradiated group. Specificity was 100% for both contrasts but sensitivity was almost four times higher using dark-field tomography. Two cases were missed by absorption tomography but were detected by dark-field tomography.

Conclusions

The applicability of X-ray dark-field computed tomography for the detection of radiation-induced lung damage was demonstrated in a pre-clinical mouse model. The presented results illustrate the differences between dark-field and absorption contrast and show that dark-field tomography could be advantageous in future clinical settings.

Altered responses of end-expiratory lung volume and upper airway patency to body posture in diet-induced obese mice

OBJECTIVE

Although both obesity and body posture are important factors affecting end-expiratory lung volume (EELV) and upper airway patency, the influence of those factors on EELV and the association between EELV and upper airway calibers are still unknown in mice. This study examined such interaction effects in obese mice to test the hypothesis that obese mice have decreased EELV accompanied by structural alterations of the upper airway.

METHODS

A high-resolution in vivo micro-computed tomography was utilized to scan anesthetized lean and diet-induced obese mice in the prone and supine positions, followed by quantifying lung volume and analyzing upper airway morphology.

RESULTS

There was a statistically significant interaction between the effects of body weight and posture on both EELV (p = 0.0049, η 2  = 0.1041) and upper airway calibers (p = 0.0215, η 2  = 0.6304). In lean mice, EELV in the prone position was significantly larger than in the supine position (prone EELV = 193.22 ± 9.10 µl vs. supine EELV = 176.01 ± 10.91 µl; p = 0.0072), whereas obese mice did not have such an improvement in EELV in the prone position (prone EELV = 174.37 ± 20.23 µl vs. supine EELV = 183.39 ± 17.49 µl; p = 0.0981) and tended to have a smaller upper airway when EELV was low based on Spearman's correlation analysis.

CONCLUSIONS

These data indicate that obesity is an important factor compromising both EELV and upper airway calibers in a posture-dependent manner even in mice, which should be taken into consideration in future studies regarding upper airway collapse and lung mechanical properties using mice.

The effects of despeckling filters on pore size measurements in collagen scaffold micro-CT data

Micro-CT is often used to assess the characteristics of porous structures such as tissue engineering scaffolds and trabecular bone. Prior to analysis, micro-CT images can be thresholded and filtered to remove noise. Scaffold pore size affects mechanical properties and biological cell behaviour and is a frequently assessed parameter. This paper identifies and characterizes an artefact affecting a commonly used filter which erroneously increases mean pore size. The 3D sweep despeckling filter removes all but the largest object within a volume of interest, and therefore deletes any disconnected objects located at the periphery, increasing measured mean pore size. This artefact is characterized, and effective methods to mitigate its effects are devised, involving despeckling a sufficiently large volume of interest, then reducing the volume of interest in size to remove the error prior to analysis. Techniques to effectively apply this method to other data sets are described. This method eliminates the artefact but is time-consuming and computationally expensive. Alternative, more economical filters which remove objects below a specified size are also assessed but are shown to be affected by the same artefact. These results will help to guide the implementation of future studies investigating the effects of pore size.

Automatic algorithm for quantifying lung involvement in patients with chronic obstructive pulmonary disease, infection with SARS-CoV-2, paracoccidioidomycosis and no lung disease patients

In this work, we aimed to develop an automatic algorithm for the quantification of total volume and lung impairments in four different diseases. The quantification was completely automatic based upon high resolution computed tomography exams. The algorithm was capable of measuring volume and differentiating pulmonary involvement including inflammatory process and fibrosis, emphysema, and ground-glass opacities. The algorithm classifies the percentage of each pulmonary involvement when compared to the entire lung volume. Our algorithm was applied to four different patients groups: no lung disease patients, patients diagnosed with SARS-CoV-2, patients with chronic obstructive pulmonary disease, and patients with paracoccidioidomycosis. The quantification results were compared with a semi-automatic algorithm previously validated. Results confirmed that the automatic approach has a good agreement with the semi-automatic. Bland-Altman (B&A) demonstrated a low dispersion when comparing total lung volume, and also when comparing each lung impairment individually. Linear regression adjustment achieved an R value of 0.81 when comparing total lung volume between both methods. Our approach provides a reliable quantification process for physicians, thus impairments measurements contributes to support prognostic decisions in important lung diseases including the infection of SARS-CoV-2.

Single-cell RNA sequencing reveals the induction of novel myeloid and myeloid-associated cell populations in visceral fat with long-term obesity

Macrophages and other immune cells are important contributors to obesity-associated inflammation; however, the cellular identities of these specific populations remain unknown. In this study, we identified individual populations of myeloid cells found in mouse epididymal/visceral adipose tissue by single-cell RNA sequencing, immunofluorescence, and flow cytometry. Multiple canonical correlation analysis identified 11 unique myeloid and myeloid-associate cell populations. In obese mice, we detected an increased percentage of monocyte-derived pro-inflammatory cells expressing Cd9 and Trem2, as well as significantly decreased percentages of multiple cell populations, including tissue-resident cells expressing Lyve1, Mafb, and Mrc1. We have identified and validated a novel myeloid/macrophage population defined by Ly6a expression, exhibiting both myeloid and mesenchymal characteristics, which increased with obesity and showed high pro-fibrotic characteristics in vitro. Our mouse adipose tissue myeloid cell atlas provides an important resource to investigate obesity-associated inflammation and fibrosis.

Imaging Biomarkers in Animal Models of Drug-Induced Lung Injury: A Systematic Review

For drug-induced interstitial lung disease (DIILD) translational imaging biomarkers are needed to improve detection and management of lung injury and drug-toxicity. Literature was reviewed on animal models in which in vivo imaging was used to detect and assess lung lesions that resembled pathological changes found in DIILD, such as inflammation and fibrosis. A systematic search was carried out using three databases with key words “Animal models”, “Imaging”, “Lung disease”, and “Drugs”. A total of 5749 articles were found, and, based on inclusion criteria, 284 papers were selected for final data extraction, resulting in 182 out of the 284 papers, based on eligibility. Twelve different animal species occurred and nine various imaging modalities were used, with two-thirds of the studies being longitudinal. The inducing agents and exposure (dose and duration) differed from non-physiological to clinically relevant doses. The majority of studies reported other biomarkers and/or histological confirmation of the imaging results. Summary of radiotracers and examples of imaging biomarkers were summarized, and the types of animal models and the most used imaging modalities and applications are discussed in this review. Pathologies resembling DIILD, such as inflammation and fibrosis, were described in many papers, but only a few explicitly addressed drug-induced toxicity experiments.

Overcoming interferon (IFN)-γ resistance ameliorates transforming growth factor (TGF)-β-mediated lung fibroblast-to-myofibroblast transition and bleomycin-induced pulmonary fibrosis

Abnormal activation of transforming growth factor (TGF)-β is a common cause of fibroblast activation and fibrosis. In bleomycin (BLM)-induced lung fibrosis, the marked expression of phospho-Src homology-2 domain-containing phosphatase (SHP) 2, phospho-signal transducer and activator of transcription (STAT) 3, and suppressor of cytokine signaling (SOCS) 3 was highly associated with pulmonary parenchymal lesions and collagen deposition. Human pulmonary fibroblasts differentiated into myofibroblasts exhibited activation of SHP2, SOCS3, protein inhibitor of activated STAT1, STAT3, interleukin (IL)-6, and IL-10. The significant retardation of interferon (IFN)-γ signaling in myofibroblasts was revealed by the decreased expression of phospho-STAT1, IFN-γ-associated genes, and IFN-γ-inducible protein (IP) 10. Microarray analysis showed an induction of fibrotic genes in TGF-β1-differentiated myofibroblasts, whereas IFN-γ-regulated anti-fibrotic genes were suppressed. Interestingly, BIBF 1120 treatment effectively inhibited both STAT3 and SHP2 phosphorylation in TGF-β1-differentiated myofibroblasts and BLM fibrotic lung tissues, which was accompanied by suppression of fibroblast-myofibroblast transition. Moreover, the combined treatment of BIBF 1120 plus IFN-γ or SHP2 inhibitor PHPS1 plus IFN-γ markedly reduced TGF-β1-induced α-smooth muscle actin and further ameliorated BLM lung fibrosis. Accordingly, myofibroblasts were hyporesponsiveness to IFN-γ, while blockade of SHP2 contributed to the anti-fibrotic efficacy of IFN-γ.

Early detection of radiation-induced lung damage with X-ray dark-field radiography in mice

OBJECTIVE

Assessing the advantage of x-ray dark-field contrast over x-ray transmission contrast in radiography for the detection of developing radiation-induced lung damage in mice.

METHODS

Two groups of female C57BL/6 mice (irradiated and control) were imaged obtaining both contrasts monthly for 28 weeks post irradiation. Six mice received 20 Gy of irradiation to the entire right lung sparing the left lung. The control group of six mice was not irradiated. A total of 88 radiographs of both contrasts were evaluated for both groups based on average values for two regions of interest, covering (irradiated) right lung and healthy left lung. The ratio of these average values, R, was distinguished between healthy and damaged lungs for both contrasts. The time-point when deviations of R from healthy lung exceeded 3σ was determined and compared among contrasts. The Wilcoxon-Mann-Whitney test was used to test against the null hypothesis that there is no difference between both groups. A selection of 32 radiographs was assessed by radiologists. Sensitivity and specificity were determined in order to compare the diagnostic potential of both contrasts. Inter-reader and intra-reader accuracy were rated with Cohen's kappa.

RESULTS

Radiation-induced morphological changes of lung tissue caused deviations from the control group that were measured on average 10 weeks earlier with x-ray dark-field contrast than with x-ray transmission contrast. Sensitivity, specificity, and accuracy doubled using dark-field radiography.

CONCLUSION

X-ray dark-field radiography detects morphological changes of lung tissue associated with radiation-induced damage earlier than transmission radiography in a pre-clinical mouse model.

KEY POINTS

• Significant deviations from healthy lung due to irradiation were measured after 16 weeks with x-ray dark-field radiography (p = 0.004). • Significant deviations occur on average 10 weeks earlier for x-ray dark-field radiography in comparison to x-ray transmission radiography. • Sensitivity and specificity doubled when using x-ray dark-field radiography instead of x-ray transmission radiography.

Longitudinal Imaging Using PET/CT with Collagen-I PET-Tracer and MRI for Assessment of Fibrotic and Inflammatory Lesions in a Rat Lung Injury Model

Non-invasive imaging biomarkers (IBs) are warranted to enable improved diagnostics and follow-up monitoring of interstitial lung disease (ILD) including drug-induced ILD (DIILD). Of special interest are IB, which can characterize and differentiate acute inflammation from fibrosis. The aim of the present study was to evaluate a PET-tracer specific for Collagen-I, combined with multi-echo MRI, in a rat model of DIILD. Rats were challenged intratracheally with bleomycin, and subsequently followed by MRI and PET/CT for four weeks. PET imaging demonstrated a significantly increased uptake of the collagen tracer in the lungs of challenged rats compared to controls. This was confirmed by MRI characterization of the lesions as edema or fibrotic tissue. The uptake of tracer did not show complete spatial overlap with the lesions identified by MRI. Instead, the tracer signal appeared at the borderline between lesion and healthy tissue. Histological tissue staining, fibrosis scoring, lysyl oxidase activity measurements, and gene expression markers all confirmed establishing fibrosis over time. In conclusion, the novel PET tracer for Collagen-I combined with multi-echo MRI, were successfully able to monitor fibrotic changes in bleomycin-induced lung injury. The translational approach of using non-invasive imaging techniques show potential also from a clinical perspective.

STAT2 signaling restricts viral dissemination but drives severe pneumonia in SARS-CoV-2 infected hamsters

Emergence of SARS-CoV-2 causing COVID-19 has resulted in hundreds of thousands of deaths. In search for key targets of effective therapeutics, robust animal models mimicking COVID-19 in humans are urgently needed. Here, we show that Syrian hamsters, in contrast to mice, are highly permissive to SARS-CoV-2 and develop bronchopneumonia and strong inflammatory responses in the lungs with neutrophil infiltration and edema, further confirmed as consolidations visualized by micro-CT alike in clinical practice. Moreover, we identify an exuberant innate immune response as key player in pathogenesis, in which STAT2 signaling plays a dual role, driving severe lung injury on the one hand, yet restricting systemic virus dissemination on the other. Our results reveal the importance of STAT2-dependent interferon responses in the pathogenesis and virus control during SARS-CoV-2 infection and may help rationalizing new strategies for the treatment of COVID-19 patients.

In-vivo lung fibrosis staging in a bleomycin-mouse model: a new micro-CT guided densitometric approach

Although increasing used in the preclinical testing of new anti-fibrotic drugs, a thorough validation of micro-computed tomography (CT) in pulmonary fibrosis models has not been performed. Moreover, no attempts have been made so far to define density thresholds to discriminate between aeration levels in lung parenchyma. In the present study, a histogram-based analysis was performed in a mouse model of bleomycin (BLM)-induced pulmonary fibrosis by micro-CT, evaluating longitudinal density changes from 7 to 21 days after BLM challenge, a period representing the progression of fibrosis. Two discriminative densitometric indices (i.e. 40th and 70th percentiles) were extracted from Hounsfield Unit density distributions and selected for lung fibrosis staging. The strong correlation with histological findings (r_Spearman = 0.76, p < 0.01) confirmed that variations in 70th percentile could reflect a pathological lung condition and estimate the effect of antifibrotic treatments. This index was therefore used to define lung aeration levels in mice distinguishing in hyper-inflated, normo-, hypo- and non-aerated pulmonary compartments. A retrospective analysis performed on a large cohort of mice confirmed the correlation between the proposed preclinical density thresholds and the histological outcomes (r_Spearman = 0.6, p < 0.01), strengthening their suitability for tracking disease progression and evaluating antifibrotic drug candidates.

Longitudinal micro-computed tomography-derived biomarkers quantify non-resolving lung fibrosis in a silicosis mouse model

In spite of many compounds identified as antifibrotic in preclinical studies, pulmonary fibrosis remains a life-threatening condition for which highly effective treatment is still lacking. Towards improving the success-rate of bench-to-bedside translation, we investigated in vivo µCT-derived biomarkers to repeatedly quantify experimental silica-induced pulmonary fibrosis and assessed clinically relevant readouts up to several months after silicosis induction. Mice were oropharyngeally instilled with crystalline silica or saline and longitudinally monitored with respiratory-gated-high-resolution µCT to evaluate disease onset and progress using scan-derived biomarkers. At weeks 1, 5, 9 and 15, we assessed lung function, inflammation and fibrosis in subsets of mice in a cross-sectional manner. Silica-instillation increased the non-aerated lung volume, corresponding to onset and progression of inflammatory and fibrotic processes not resolving with time. Moreover, total lung volume progressively increased with silicosis. The volume of healthy, aerated lung first dropped then increased, corresponding to an acute inflammatory response followed by recovery into lower elevated aerated lung volume. Imaging results were confirmed by a significantly decreased Tiffeneau index, increased neutrophilic inflammation, increased IL-13, MCP-1, MIP-2 and TNF-α concentration in bronchoalveolar lavage fluid, increased collagen content and fibrotic nodules. µCT-derived biomarkers enable longitudinal evaluation of early onset inflammation and non-resolving pulmonary fibrosis as well as lung volumes in a sensitive and non-invasive manner. This approach and model of non-resolving lung fibrosis provides quantitative assessment of disease progression and stabilization over weeks and months, essential towards evaluation of fibrotic disease burden and antifibrotic therapy evaluation in preclinical studies.

From Mouse to Man and Back: Closing the Correlation Gap between Imaging and Histopathology for Lung Diseases

Lung diseases such as fibrosis, asthma, cystic fibrosis, infection and cancer are life-threatening conditions that slowly deteriorate quality of life and for which our diagnostic power is high, but our knowledge on etiology and/or effective treatment options still contains important gaps. In the context of day-to-day practice, clinical and preclinical studies, clinicians and basic researchers team up and continuously strive to increase insights into lung disease progression, diagnostic and treatment options. To unravel disease processes and to test novel therapeutic approaches, investigators typically rely on end-stage procedures such as serum analysis, cyto-/chemokine profiles and selective tissue histology from animal models. These techniques are useful but provide only a snapshot of disease processes that are essentially dynamic in time and space. Technology allowing evaluation of live animals repeatedly is indispensable to gain a better insight into the dynamics of lung disease progression and treatment effects. Computed tomography (CT) is a clinical diagnostic imaging technique that can have enormous benefits in a research context too. Yet, the implementation of imaging techniques in laboratories lags behind. In this review we want to showcase the integrated approaches and novel developments in imaging, lung functional testing and pathological techniques that are used to assess, diagnose, quantify and treat lung disease and that may be employed in research on patients and animals. Imaging approaches result in often novel anatomical and functional biomarkers, resulting in many advantages, such as better insight in disease progression and a reduction in the numbers of animals necessary. We here showcase integrated assessment of lung disease with imaging and histopathological technologies, applied to the example of lung fibrosis. Better integration of clinical and preclinical imaging technologies with pathology will ultimately result in improved clinical translation of (therapy) study results.

Cobalt exposure via skin alters lung immune cells and enhances pulmonary responses to cobalt in mice

Cobalt has been associated with allergic contact dermatitis and occupational asthma. However, the link between skin exposure and lung responses to cobalt is currently unknown. We investigated the effect of prior dermal sensitization to cobalt on pulmonary physiological and immunological responses after subsequent challenge with cobalt via the airways. BALB/c mice received epicutaneous applications (25 μL/ear) with 5% CoCl_2*6H₂O (Co) or the vehicle (Veh) dimethyl sulfoxide (DMSO) twice; they then received oropharyngeal challenges with 0.05% CoCl_2*6H₂O or saline five times, thereby obtaining four groups: Veh/Veh, Co/Veh, Veh/Co, and Co/Co. To detect early respiratory responses noninvasively, we performed sequential in vivo microcomputed tomography (µCT). One day after the last challenge, we assessed airway hyperreactivity (AHR) to methacholine, inflammation in bronchoalveolar lavage (BAL), innate lymphoid cells (ILCs) and dendritic cells (DCs) in the lungs, and serum IgE. Compared with the Veh/Veh group, the Co/Co group showed increased µCT-derived lung response, increased AHR to methacholine, mixed neutrophilic and eosinophilic inflammation, elevated monocyte chemoattractant protein-1 (MCP-1), and elevated keratinocyte chemoattractant (KC) in BAL. Flow cytometry in the Co/Co group demonstrated increased DC, type 1 and type 2 conventional DC (cDC1/cDC2), monocyte-derived DC, increased ILC group 2, and natural cytotoxicity receptor^-ILC group 3. The Veh/Co group showed only increased AHR to methacholine and elevated MCP-1 in BAL, whereas the Co/Veh group showed increased cDC1 and ILC2 in lung. We conclude that dermal sensitization to cobalt may increase the susceptibility of the lungs to inhaling cobalt. Mechanistically, this enhanced susceptibility involves changes in pulmonary DCs and ILCs.

Brd4-p300 inhibition downregulates Nox4 and accelerates lung fibrosis resolution in aged mice

Tissue regeneration capacity declines with aging in association with heightened oxidative stress. Expression of the oxidant-generating enzyme, NADPH oxidase 4 (Nox4), is elevated in aged mice with diminished capacity for fibrosis resolution. Bromodomain-containing protein 4 (Brd4) is a member of the bromodomain and extraterminal (BET) family of proteins that function as epigenetic "readers" of acetylated lysine groups on histones. In this study, we explored the role of Brd4 and its interaction with the p300 acetyltransferase in the regulation of Nox4 and the in vivo efficacy of a BET inhibitor to reverse established age-associated lung fibrosis. BET inhibition interferes with the association of Brd4, p300, and acetylated histone H4K16 with the Nox4 promoter in lung fibroblasts stimulated with the profibrotic cytokine, TGF-β1. A number of BET inhibitors, including I-BET-762, JQ1, and OTX015, downregulate Nox4 gene expression and activity. Aged mice with established and persistent lung fibrosis recover capacity for fibrosis resolution with OTX015 treatment. This study implicates epigenetic regulation of Nox4 by Brd4 and p300 and supports BET/Brd4 inhibition as an effective strategy for the treatment of age-related fibrotic lung disease.

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.

Intergenerational Transmission of Diet-Induced Obesity, Metabolic Imbalance, and Osteoarthritis in Mice

OBJECTIVE

Obesity and osteoarthritis (OA) are 2 major public health issues affecting millions of people worldwide. Whereas parental obesity affects the predisposition to diseases such as cancer or diabetes in children, transgenerational influences on musculoskeletal conditions such as OA are poorly understood. This study was undertaken to assess the intergenerational effects of a parental/grandparental high-fat diet on the metabolic and skeletal phenotype, systemic inflammation, and predisposition to OA in 2 generations of offspring in mice.

METHODS

Metabolic phenotype and predisposition to OA were investigated in the first and second (F1 and F2) generations of offspring (n = 10-16 mice per sex per diet) bred from mice fed a high-fat diet (HFD) or a low-fat control diet. OA was induced by destabilizing the medial meniscus. OA, synovitis, and adipose tissue inflammation were determined histologically, while bone changes were measured using micro-computed tomography. Serum and synovial cytokines were measured by multiplex assay.

RESULTS

Parental high-fat feeding showed an intergenerational effect, with inheritance of increased weight gain (up to 19% in the F1 generation and 9% in F2), metabolic imbalance, and injury-induced OA in at least 2 generations of mice, despite the fact that the offspring were fed the low-fat diet. Strikingly, both F1 and F2 female mice showed an increased predisposition to injury-induced OA (48% higher predisposition in F1 and 19% in F2 female mice fed the HFD) and developed bone microarchitectural changes that were attributable to parental and grandparental high-fat feeding.

CONCLUSION

The results of this study reveal a detrimental effect of parental HFD and obesity on the musculoskeletal integrity of 2 generations of offspring, indicating the importance of further investigation of these effects. An improved understanding of the mechanisms involved in the transmissibility of diet-induced changes through multiple generations may help in the development of future therapies that would target the effects of obesity on OA and related conditions.

Preterm birth impairs postnatal lung development in the neonatal rabbit model

Background

Bronchopulmonary dysplasia continues to cause important respiratory morbidity throughout life, and new therapies are needed. The common denominator of all BPD cases is preterm birth, however most preclinical research in this area focusses on the effect of hyperoxia or mechanical ventilation. In this study we investigated if and how prematurity affects lung structure and function in neonatal rabbits.

Methods

Pups were delivered on either day 28 or day 31. For each gestational age a group of pups was harvested immediately after birth for lung morphometry and surfactant protein B and C quantification. All other pups were hand raised and harvested on day 4 for the term pups and day 7 for the preterm pups (same corrected age) for lung morphometry, lung function testing and qPCR. A subset of pups underwent microCT and dark field imaging on day 0, 2 and 4 for terms and on day 0, 3, 5 and 7 for preterms.

Results

Preterm pups assessed at birth depicted a more rudimentary lung structure (larger alveoli and thicker septations) and a lower expression of surfactant proteins in comparison to term pups. MicroCT and dark field imaging revealed delayed lung aeration in preterm pups, in comparison to term pups. Preterm birth led to smaller pups, with smaller lungs with a lower alveolar surface area on day 7/day 4. Furthermore, preterm birth affected lung function with increased tissue damping, tissue elastance and resistance and decreased dynamic compliance. Expression of vascular endothelial growth factor (VEGFA) was significantly decreased in preterm pups, however in the absence of structural vascular differences.

Conclusions

Preterm birth affects lung structure and function at birth, but also has persistent effects on the developing lung. This supports the use of a preterm animal model, such as the preterm rabbit, for preclinical research on BPD. Future research that focuses on the identification of pathways that are involved in in-utero lung development and disrupted by pre-term birth, could lead to novel therapeutic strategies for BPD.

Radiosafe micro-computed tomography for longitudinal evaluation of murine disease models

Implementation of in vivo high-resolution micro-computed tomography (µCT), a powerful tool for longitudinal analysis of murine lung disease models, is hampered by the lack of data on cumulative low-dose radiation effects on the investigated disease models. We aimed to measure radiation doses and effects of repeated µCT scans, to establish cumulative radiation levels and scan protocols without relevant toxicity. Lung metastasis, inflammation and fibrosis models and healthy mice were weekly scanned over one-month with µCT using high-resolution respiratory-gated 4D and expiration-weighted 3D protocols, comparing 5-times weekly scanned animals with controls. Radiation dose was measured by ionization chamber, optical fiberradioluminescence probe and thermoluminescent detectors in a mouse phantom. Dose effects were evaluated by in vivo µCT and bioluminescence imaging read-outs, gold standard endpoint evaluation and blood cell counts. Weekly exposure to 4D µCT, dose of 540-699 mGy/scan, did not alter lung metastatic load nor affected healthy mice. We found a disease-independent decrease in circulating blood platelets and lymphocytes after repeated 4D µCT. This effect was eliminated by optimizing a 3D protocol, reducing dose to 180-233 mGy/scan while maintaining equally high-quality images. We established µCT safety limits and protocols for weekly repeated whole-body acquisitions with proven safety for the overall health status, lung, disease process and host responses under investigation, including the radiosensitive blood cell compartment.

Restrictive lung disease in TNF-transgenic mice: correlation of pulmonary function testing and micro-CT imaging

Purpose: Micro-computed tomography (µCT) is increasingly being used on animal models as a minimally-invasive longitudinal outcome measure of pulmonary disease progression. However, while imaging can elucidate macroscopic structural changes over the whole lung, µCT is unable to describe the mechanical changes and functional impairments imposed by progressive disease, which can only be measured via pulmonary function tests (PFTs). The tumor necrosis factor-transgenic (TNF-Tg) mouse model of rheumatoid arthritis (RA) develops pulmonary pathology that mimics many aspects of the inflammatory interstitial lung disease (ILD) seen in a subset of patients with RA. Prior studies using µCT imaging of these mice found increased pulmonary density, characteristic of restrictive disease; however, there have been conflicting reports in the literature regarding the obstructive versus restrictive phenotype of this model. Our study looks to 1) define the functional impairments and 2) characterize the restrictive/obstructive nature of the disease found in this model. Materials and Methods: In this study, we performed PFTs at end-stage ILD, and paired these findings with µCT results, correlating radiology to functional parameters. TNF-Tg and WT littermates of both sexes underwent µCT imaging and PFT testing at 5.5 months-old. Spearman's correlation analyses were performed comparing lung tissue volume (LTV) to PFT parameters of gas exchange and tissue stiffness. Results: Compared to WT, TNF-Tg mice had impaired gas exchange capacity, increased respiratory resistance, and reduced lung compliance, elastance, and inspiratory capacity, indicating increased tissue stiffness and compromised pulmonary function. LTV was also consistently higher in TNF-Tg lungs. Conclusions: These findings demonstrate that: 1) TNF-Tg mice display a restrictive pathology, and 2) in vivo µCT is a valid outcome measure to infer changes in pulmonary mechanical and functional parameters.

Sensitive bioluminescence imaging of fungal dissemination to the brain in mouse models of cryptococcosis

Cryptococcus neoformans is a leading cause of fungal brain infection, but the mechanism of dissemination and dynamics of cerebral infection following pulmonary disease are poorly understood. To address these questions, non-invasive techniques that can study the dynamic processes of disease development and progression in living animal models or patients are required. As such, bioluminescence imaging (BLI) has emerged as a powerful tool to evaluate the spatial and temporal distribution of infection in living animals. We aimed to study the time profile of the dissemination of cryptococcosis from the lung to the brain in murine models by engineering the first bioluminescent C. neoformans KN99α strain, expressing a sequence-optimized red-shifted luciferase. The high pathogen specificity and sensitivity of BLI was complemented by the three-dimensional anatomical information from micro-computed tomography (μCT) of the lung and magnetic resonance imaging (MRI) of the brain. These non-invasive imaging techniques provided longitudinal readouts on the spatial and temporal distribution of infection following intravenous, intranasal or endotracheal routes of inoculation. Furthermore, the imaging results correlated strongly with the fungal load in the respective organs. By obtaining dynamic and quantitative information about the extent and timing of brain infections for individual animals, we found that dissemination to the brain after primary infection of the lung is likely a late-stage event with a timeframe that is variable between animals. This novel tool in Cryptococcus research can aid the identification of host and pathogen factors involved in this process, and supports development of novel preventive or therapeutic approaches.

Summary: A novel combination of bioluminescence and anatomical imaging non-invasively identified the timeframe and extent of Cryptococcus neoformans dissemination to the brain in animal models of systemic and pulmonary fungal infection.

Efficacy of Novel Highly Specific Bromodomain-Containing Protein 4 Inhibitors in Innate Inflammation-Driven Airway Remodeling

NF-κB/RelA triggers innate inflammation by binding to bromodomain-containing protein 4 (BRD4), an atypical histone acetyltransferase (HAT). Although RelA·BRD4 HAT mediates acute neutrophilic inflammation, its role in chronic and functional airway remodeling is not known. We observed that BRD4 is required for Toll-like receptor 3 (TLR3)-mediated mesenchymal transition, a cell-state change that is characteristic of remodeling. We therefore tested two novel highly selective BRD4 inhibitors, ZL0420 and ZL0454, for their effects on chronic airway remodeling produced by repetitive TLR3 agonist challenges, and compared their efficacy with that of two nonselective bromodomain and extraterminal (BET) protein inhibitors, JQ1 and RVX208. We observed that ZL0420 and ZL0454 more potently reduced polyinosinic:polycytidylic acid-induced weight loss and fibrosis as assessed by microcomputed tomography and second harmonic generation microscopy. These measures correlated with the collagen deposition observed in histopathology. Importantly, the ZL inhibitors were more effective than the nonselective BET inhibitors at equivalent doses. The ZL inhibitors had significant effects on lung physiology, reversing TLR3-associated airway hyperresponsiveness and increasing lung compliance in vivo. At the molecular level, ZL inhibitors reduced elaboration of the transforming growth factor-β-induced growth program, thereby preventing mucosal mesenchymal transition and disrupting BRD4 HAT activity and complex formation with RelA. We also observed that ZL0454 treatment blocked polyinosinic:polycytidylic acid-associated expansion of the α-SMA1⁺/COL1A⁺ myofibroblast population and prevented myofibroblast transition in a coculture system. We conclude that 1) BRD4 is a central effector of the mesenchymal transition that results in paracrine activation of myofibroblasts, mechanistically linking innate inflammation to airway hyperresponsiveness and fibrosis, and 2) highly selective BRD4 inhibitors may be effective in reversing the effects of repetitive airway viral infections on innate inflammation-mediated remodeling.

Low-dose administration of bleomycin leads to early alterations in lung mechanics

NEW FINDINGS

What is the central question of this study? When do alterations in pulmonary mechanics occur following chronic low-dose administration of bleomycin? What is the main finding and its importance? Remarkably, we report changes in lung mechanics as early as day 7 that corresponded to parameters determined from single-frequency forced oscillation manoeuvres and pressure-volume loops. These changes preceded substantial histological changes or changes in gene expression levels. These findings are significant to refine drug discovery in idiopathic pulmonary fibrosis, where preclinical studies using lung function parameters would enhance the translational potential of drug candidates where lung function readouts are routinely performed in the clinic.

ABSTRACT

Idiopathic pulmonary fibrosis (IPF) is the most widespread form of interstitial lung disease and, currently, there are only limited treatment options available. In preclinical animal models of lung fibrosis, the effectiveness of experimental therapeutics is often deemed successful via reductions in collagen deposition and expression of profibrotic genes in the lung. However, in clinical studies, improvements in lung function are primarily used to gauge the success of therapeutics directed towards IPF. Therefore, we examined whether changes in respiratory system mechanics in the early stages of an experimental model of lung fibrosis can be used to refine drug discovery approaches for IPF. C57BL/6J mice were administered bleomycin (BLM) or a vehicle control i.p. twice a week for 4 weeks. At 7, 14, 21, 28 and 33 days into the BLM treatment regimen, indices of respiratory system mechanics and pressure-volume relationships were measured. Concomitant with these measurements, histological and gene analyses relevant to lung fibrosis were performed. Alterations in respiratory system mechanics and pressure-volume relationships were observed as early as 7 days after the start of BLM administration. Changes in respiratory system mechanics preceded the appearance of histological and molecular indices of lung fibrosis. Administration of BLM leads to early changes in respiratory system mechanics that coincide with the appearance of representative histological and molecular indices of lung fibrosis. Consequently, these data suggest that dampening the early changes in respiratory system mechanics might be used to assess the effectiveness of experimental therapeutics in preclinical animal models of lung fibrosis.

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.

A Multimodal Imaging Approach Based on Micro-CT and Fluorescence Molecular Tomography for Longitudinal Assessment of Bleomycin-Induced Lung Fibrosis in Mice

Idiopathic pulmonary fibrosis (IPF) is a fatal lung disease characterized by the progressive and irreversible destruction of lung architecture, which causes significant deterioration in lung function and subsequent death from respiratory failure. The pathogenesis of IPF in experimental animal models has been induced by bleomycin administration. In this study, we investigate an IPF-like mouse model induced by a double intratracheal bleomycin instillation. Standard histological assessments used for studying lung fibrosis are invasive terminal procedures. The goal of this work is to monitor lung fibrosis through noninvasive imaging techniques such as Fluorescent Molecular Tomography (FMT) and Micro-CT. These two technologies validated with histology findings could represent a revolutionary functional approach for real time non-invasive monitoring of IPF disease severity and progression. The fusion of different approaches represents a step further for understanding the IPF disease, where the molecular events occurring in a pathological condition can be observed with FMT and the subsequent anatomical changes can be monitored by Micro-CT.

A fully automated image analysis method to quantify lung fibrosis in the bleomycin-induced rat model

Intratracheal administration of bleomycin induces fibrosis in the lung, which is mainly assessed by histopathological grading that is subjective. Current literature highlights the need of reproducible and quantitative pulmonary fibrosis analysis. If some quantitative studies looked at fibrosis parameters separately, none of them quantitatively assessed both aspects: lung tissue remodeling and collagenization. To ensure reliable quantification, support vector machine learning was used on digitalized images to design a fully automated method that analyzes two important aspects of lung fibrosis: (i) areas having substantial tissue remodeling with appearance of dense fibrotic masses and (ii) collagen deposition. Fibrotic masses were identified on low magnification images and collagen detection was performed at high magnification. To insure a fully automated application the tissue classifier was trained on several independent studies that were performed over a period of four years. The detection method generates two different values that can be used to quantify lung fibrosis development: (i) percent area of fibrotic masses and (ii) percent of alveolar collagen. These two parameters were validated using independent studies from bleomycin- and saline-treated animals. A significant change of these lung fibrosis quantification parameters- increased amount of fibrotic masses and increased collagen deposition- were observed upon intratracheal administration of bleomycin and subsequent significant beneficial treatments effects were observed with BIBF-1120 and pirfenidone.

Longitudinal micro-CT as an outcome measure of interstitial lung disease in TNF-transgenic mice

INTRODUCTION

Rheumatoid arthritis associated interstitial lung disease (RA-ILD) is a debilitating condition with poor survival prognosis. High resolution computed tomography (CT) is a common clinical tool to diagnose RA-ILD, and is increasingly being adopted in pre-clinical studies. However, murine models recapitulating RA-ILD are lacking, and CT outcomes for inflammatory lung disease have yet to be formally validated. To address this, we validate μCT outcomes for ILD in the tumor necrosis factor transgenic (TNF-Tg) mouse model of RA.

METHODS

Cross sectional μCT was performed on cohorts of male TNF-Tg mice and their WT littermates at 3, 4, 5.5 and 12 months of age (n = 4-6). Lung μCT outcomes measures were determined by segmentation of the μCT datasets to generate Aerated and Tissue volumes. After each scan, lungs were obtained for histopathology and 3 sections stained with hematoxylin and eosin. Automated histomorphometry was performed to quantify the tissue area (nuclei, cytoplasm, and extracellular matrix) and aerated area (white space) within the tissue sections. Spearman's correlation coefficients were used to evaluate the extent of association between μCT imaging and histopathology endpoints.

RESULTS

TNF-Tg mice had significantly greater tissue volume, total lung volume and mean intensity at all timepoints compared to age matched WT littermates. Histomorphometry also demonstrated a significant increase in tissue area at 3, 4, and 5.5 months of age in TNF-Tg mice. Lung tissue volume was correlated with lung tissue area (ρ = 0.81, p<0.0001), and normalize lung aerated volume was correlated with normalized lung air area (ρ = 0.73, p<0.0001).

CONCLUSIONS

We have validated in vivo μCT as a quantitative biomarker of ILD in mice. Further, development of longitudinal measures is critical for dissecting pathologic progression of ILD, and μCT is a useful non-invasive method to study lung inflammation in the TNF-Tg mouse model.