Functionalized synchrotron in-line phase-contrast computed tomography: a novel approach for simultaneous quantification of structural alterations and localization of barium-labelled alveolar macrophages within mouse lung samples

Protocol for high-resolution 3D visualization of insect regenerating legs through micro-computed tomography

Appendage regeneration occurs within the opaque exoskeleton in arthropods, making it challenging to visualize the regenerative processes dynamically. In this protocol, we present a strategy to scan and capture the high-resolution details of microstructural tissues at certain regeneration points through micro-computed tomography (micro-CT). We describe steps for tissue preparation, fixation, critical point drying, micro-CT scanning, and 3D visualization. This approach promises significant utility in the field of regeneration, particularly in studies involving arthropods such as insects and crustaceans. For complete details on the use and execution of this protocol, please refer to Ren et al.1.

Comparison of microstructural imaging of the root canal isthmus using propagation-based X-ray phase-contrast and absorption micro-computed tomography

Clear and complete microstructural imaging of the root canal isthmus is an important part of pathological investigations in research and clinical practice. X-ray micro-computed tomography (μCT) is a widely used non-destructive imaging technique, which allows for distortion-free three-dimensional (3D) visualisation. While absorption μCT typically has poor contrast resolution for observing the root canal isthmus, especially for weak-absorbing tissues, propagation-based X-ray phase-contrast imaging (PBI) is a powerful imaging method, which in its combination with μCT (PB-PCμCT) enables high-resolution and high-contrast microstructural imaging of the weak-absorbing tissues in samples. To investigate the feasibility and ability of PB-PCμCT in microstructural imaging of the root canal isthmus, conventional absorption μCT and PB-PCμCT experiments were performed. The two-dimensional (2D) and 3D comparison results demonstrated that, compared to absorption μCT, PB-PCμCT has the ability to image the root canal isthmus more clearly and completely, and thus, it has great potential to serve as a valuable tool for biomedical and preclinical studies on the root canal isthmus.

Three-dimensional assessment of bronchiectasis in a mouse model of mucociliary clearance disorder

Bronchiectasis is a chronic pathological condition characterised by abnormal enlargement of the lung's conductive airways. It is associated with a lack of ciliary motility and restricted mucociliary clearance in diseases such as primary ciliary dyskinesia (PCD) or “immotile cilia syndrome”. Recent studies have shown an increase in the prevalence of bronchiectasis, causing a significant burden on public healthcare systems [1, 2]. The mechanisms that trigger and drive the development of bronchiectasis have yet to be fully elucidated. Murine models of immotile cilia or reduced mucociliary clearance failed to display signs of bronchiectasis in multiple studies, raising questions about the suitability of murine models for non-cystic fibrosis (CF) bronchiectasis and hindering the development of targeted therapies [3].

Synchrotron-based imaging allows for detection of bronchiectasis-like phenotypes in mice with mucociliary clearance disordershttps://bit.ly/3gXGdP3

X-ray-Based Techniques to Study the Nano-Bio Interface

X-ray-based analytics are routinely applied in many fields, including physics, chemistry, materials science, and engineering. The full potential of such techniques in the life sciences and medicine, however, has not yet been fully exploited. We highlight current and upcoming advances in this direction. We describe different X-ray-based methodologies (including those performed at synchrotron light sources and X-ray free-electron lasers) and their potentials for application to investigate the nano-bio interface. The discussion is predominantly guided by asking how such methods could better help to understand and to improve nanoparticle-based drug delivery, though the concepts also apply to nano-bio interactions in general. We discuss current limitations and how they might be overcome, particularly for future use in vivo.

Non-radioactive imaging strategies for in vivo immune cell tracking

In vivo tracking of administered cells chosen for specific disease treatment may be conducted by diagnostic imaging techniques preceded by cell labeling with special contrast agents. The most commonly used agents are those with radioactive properties, however their use in research is often impossible. This review paper focuses on the essential aspect of cell tracking with the exclusion of radioisotope tracers, therefore we compare application of different types of non-radioactive contrast agents (cell tracers), methods of cell labeling and application of various techniques for cell tracking, which are commonly used in preclinical or clinical studies. We discuss diagnostic imaging methods belonging to three groups: (1) Contrast-enhanced X-ray imaging, (2) Magnetic resonance imaging, and (3) Optical imaging. In addition, we present some interesting data from our own research on tracking immune cell with the use of discussed methods. Finally, we introduce an algorithm which may be useful for researchers planning leukocyte targeting studies, which may help to choose the appropriate cell type, contrast agent and diagnostic technique for particular disease study.

Diagnostic and Therapeutic Nanomedicine

Nanotechnology has been widely applied to medical interventions for prevention, diagnostics, and therapeutics of diseases, and the application of nanotechnology for medical purposes, which is called as a term "nanomedicine" has received tremendous attention. In particular, the design and development of nanoparticle for biosensors have received a great deal of attention, since those are most impactful area of clinical translation showing potential breakthrough in early diagnosis of diseases such as cancers and infections. For example, the nanoparticles that have intrinsic unique features such as magnetic responsive characteristics or photoluminescence can be utilized for noninvasive visualization of inner body. Drug delivery that makes use of drug-containing nanoparticles as a carrier is another field of study, in which the particulate form nanomedicine is given by parenteral administration for further systemic targeting to pathological tissues. In addition, encapsulation into nanoparticles gives the opportunity to secure the sensitive therapeutic payloads that are readily degraded or deactivated until reached to the target in biological environments, or to provide sufficient solubilization (e.g., to deliver compounds which have physicochemical properties that strongly limit their aqueous solubility and therefore systemic bioavailability). The nanomedicine is further intended to enhance the targeting index such as increased specificity and reduced false binding, thus improve the diagnostic and therapeutic performances. In this chapter, principles of nanomaterials for medicine will be thoroughly covered with applications for imaging-based diagnostics and therapeutics.

Comparison of high-resolution synchrotron-radiation-based phase-contrast imaging and absorption-contrast imaging for evaluating microstructure of vascular networks in rat brain: from 2D to 3D views

Conventional imaging methods such as magnetic resonance imaging, computed tomography and digital subtraction angiography have limited temporospatial resolutions and shortcomings like invasive angiography, potential allergy to contrast agents, and image deformation, that restrict their application in high-resolution visualization of the structure of microvessels. In this study, through comparing synchrotron radiation (SR) absorption-contrast imaging to absorption phase-contrast imaging, it was found that SR-based phase-contrast imaging could provide more detailed ultra-high-pixel images of microvascular networks than absorption phase-contrast imaging. Simultaneously, SR-based phase-contrast imaging was used to perform high-quality, multi-dimensional and multi-scale imaging of rat brain angioarchitecture. With the aid of image post-processing, high-pixel-size two-dimensional virtual slices can be obtained without sectioning. The distribution of blood supply is in accordance with the results of traditional tissue staining. Three-dimensional anatomical maps of cerebral angioarchitecture can also be acquired. Functional partitions of regions of interest are reproduced in the reconstructed rat cerebral vascular networks. Imaging analysis of the same sample can also be displayed simultaneously in two- and three-dimensional views, which provides abundant anatomical information together with parenchyma and vessels. In conclusion, SR-based phase-contrast imaging holds great promise for visualizing microstructure of microvascular networks in two- and three-dimensional perspectives during the development of neurovascular diseases.

Bismuth Ferrite Second Harmonic Nanoparticles for Pulmonary Macrophage Tracking

Recently, second harmonic generation (SHG) nanomaterials have been generated that are efficiently employed in the classical (NIR) and extended (NIR-II) near infrared windows using a multiphoton microscope. The aim was to test bismuth ferrite harmonic nanoparticles (BFO-HNPs) for their ability to monitor pulmonary macrophages in mice. BFO-loaded MH-S macrophages are given intratracheally to healthy mice or BFO-HNPs are intranasally instilled in mice with allergic airway inflammation and lung sections of up to 100 μM are prepared. Using a two-photon-laser scanning microscope, it is shown that bright BFO-HNPs signals are detected from superficially localized cells as well as from deep within the lung tissue. BFO-HNPs are identified with an excellent signal-to-noise ratio and virtually no background signal. The SHG from the nanocrystals can be distinguished from the endogenous collagen-derived SHG around the blood vessels and bronchial structures. BFO-HNPs are primarily taken up by M2 alveolar macrophages in vivo. This SHG imaging approach provides novel information about the interaction of macrophages with cells and the extracellular matrix in lung disease as it is capable of visualizing and tracking NP-loaded cells at high resolution in thick tissues with minimal background fluorescence.

Therapeutic Fluorescent Hybrid Nanoparticles for Traceable Delivery of Glucocorticoids to Inflammatory Sites

Treatment of inflammatory disorders with glucocorticoids (GCs) is often accompanied by severe adverse effects. Application of GCs via nanoparticles (NPs), especially those using simple formulations, could possibly improve their delivery to sites of inflammation and therefore their efficacy, minimising the required dose and thus reducing side effects. Here, we present the evaluation of NPs composed of GC betamethasone phosphate (BMP) and the fluorescent dye DY-647 (BMP-IOH-NPs) for improved treatment of inflammation with simultaneous in vivo monitoring of NP delivery.

Methods: BMP-IOH-NP uptake by MH-S macrophages was analysed by fluorescence and electron microscopy. Lipopolysaccharide (LPS)-stimulated cells were treated for 48 h with BMP-IOH-NPs (1×10^-5-1×10^-9 M), BMP or dexamethasone (Dexa). Drug efficacy was assessed by measurement of interleukin 6. Mice with Zymosan-A-induced paw inflammation were intraperitoneally treated with BMP-IOH-NPs (10 mg/kg) and mice with ovalbumin (OVA)-induced allergic airway inflammation (AAI) were treated intranasally with BMP-IOH-NPs, BMP or Dexa (each 2.5 mg/kg). Efficacy was assessed in vivo by paw volume measurements with µCT and ex vivo by measurement of paw weight for Zymosan-A-treated mice, or in the AAI model by in vivo x-ray-based lung function assessment and by cell counts in the bronchoalveolar lavage (BAL) fluid and histology. Delivery of BMP-IOH-NPs to the lungs of AAI mice was monitored by in vivo optical imaging and by fluorescence microscopy.

Results: Uptake of BMP-IOH-NPs by MH-S cells was observed during the first 10 min of incubation, with the NP load increasing over time. The anti-inflammatory effect of BMP-IOH-NPs in vitro was dose dependent and higher than that of Dexa or free BMP, confirming efficient release of the drug. In vivo, Zymosan-A-induced paw inflammation was significantly reduced in mice treated with BMP-IOH-NPs. AAI mice that received BMP-IOH-NPs or Dexa but not BMP revealed significantly decreased eosinophil numbers in BALs and reduced immune cell infiltration in lungs. Correspondingly, lung function parameters, which were strongly affected in non-treated AAI mice, were unaffected in AAI mice treated with BMP-IOH-NPs and resembled those of healthy animals. Accumulation of BMP-IOH-NPs within the lungs of AAI mice was detectable by optical imaging for at least 4 h in vivo, where they were preferentially taken up by peribronchial and alveolar M2 macrophages.

Conclusion: Our results show that BMP-IOH-NPs can effectively be applied in therapy of inflammatory diseases with at least equal efficacy as the gold standard Dexa, while their delivery can be simultaneously tracked in vivo by fluorescence imaging. BMP-IOH-NPs thus have the potential to reach clinical applications.

Towards synchrotron phase-contrast lung imaging in patients - a proof-of-concept study on porcine lungs in a human-scale chest phantom

In-line free propagation phase-contrast synchrotron tomography of the lungs has been shown to provide superior image quality compared with attenuation-based computed tomography (CT) in small-animal studies. The present study was performed to prove the applicability on a human-patient scale using a chest phantom with ventilated fresh porcine lungs. Local areas of interest were imaged with a pixel size of 100 µm, yielding a high-resolution depiction of anatomical hallmarks of healthy lungs and artificial lung nodules. Details like fine spiculations into surrounding alveolar spaces were shown on a micrometre scale. Minor differences in artificial lung nodule density were detected by phase retrieval. Since we only applied a fraction of the X-ray dose used for clinical high-resolution CT scans, it is believed that this approach may become applicable to the detailed assessment of focal lung lesions in patients in the future.

Optimising complementary soft tissue synchrotron X-ray microtomography for reversibly-stained central nervous system samples

Synchrotron radiation microtomography (SRμCT) is a nominally non-destructive 3D imaging technique which can visualise the internal structures of whole soft tissues. As a multi-stage technique, the cumulative benefits of optimising sample preparation, scanning parameters and signal processing can improve SRμCT imaging efficiency, image quality, accuracy and ultimately, data utility. By evaluating different sample preparations (embedding media, tissue stains), imaging (projection number, propagation distance) and reconstruction (artefact correction, phase retrieval) parameters, a novel methodology (combining reversible iodine stain, wax embedding and inline phase contrast) was optimised for fast (~12 minutes), high-resolution (3.2-4.8 μm diameter capillaries resolved) imaging of the full diameter of a 3.5 mm length of rat spinal cord. White-grey matter macro-features and micro-features such as motoneurons and capillary-level vasculature could then be completely segmented from the imaged volume for analysis through the shallow machine learning SuRVoS Workbench. Imaged spinal cord tissue was preserved for subsequent histology, establishing a complementary SRμCT methodology that can be applied to study spinal cord pathologies or other nervous system tissues such as ganglia, nerves and brain. Further, our 'single-scan iterative downsampling' approach and side-by-side comparisons of mounting options, sample stains and phase contrast parameters should inform efficient, effective future soft tissue SRμCT experiment design.

3D imaging of cells in scaffolds: direct labelling for micro CT

The development of in-vitro techniques to characterise the behaviour of cells in biomedical scaffolds is a rapidly developing field. However, until now it has not been possible to visualise, directly in 3D, the extent of cell migration using a desktop X-ray microCT. This paper describes a new technique based on cell labelling with a radio opacifier (barium sulphate), which permits cell tracking without the need for destructive sample preparation. The ability to track cells is highlighted via a comparison of cell migration through demonstrator lyophilised collagen scaffolds with contrasting pore size and interconnectivity. The results demonstrate the ease with which the technique can be used to characterise the effects of scaffold architecture on cell infiltration.

Nanotechnology for Cancer Therapy Based on Chemotherapy

Chemotherapy has been widely applied in clinics. However, the therapeutic potential of chemotherapy against cancer is seriously dissatisfactory due to the nonspecific drug distribution, multidrug resistance (MDR) and the heterogeneity of cancer. Therefore, combinational therapy based on chemotherapy mediated by nanotechnology, has been the trend in clinical research at present, which can result in a remarkably increased therapeutic efficiency with few side effects to normal tissues. Moreover, to achieve the accurate pre-diagnosis and real-time monitoring for tumor, the research of nano-theranostics, which integrates diagnosis with treatment process, is a promising field in cancer treatment. In this review, the recent studies on combinational therapy based on chemotherapy will be systematically discussed. Furthermore, as a current trend in cancer treatment, advance in theranostic nanoparticles based on chemotherapy will be exemplified briefly. Finally, the present challenges and improvement tips will be presented in combination therapy and nano-theranostics.

MÖNCH detector enables fast and low-dose free-propagation phase-contrast computed tomography of in situ mouse lungs

Due to the complexity of the underlying pathomechanism, in vivo mouse lung-disease models continue to be of great importance in preclinical respiratory research. Longitudinal studies following the cause of a disease or evaluating treatment efficacy are of particular interest but challenging due to the small size of the mouse lung and the fast breathing rate. Synchrotron-based in-line phase-contrast computed tomography imaging has been successfully applied in lung research in various applications, but mostly at dose levels that forbid longitudinal in vivo studies. Here, the novel charge-integrating hybrid detector MÖNCH is presented, which enables imaging of mouse lungs at a pixel size of 25 µm, in less than 10 s and with an entrance dose of about 70 mGy, which therefore will allow longitudinal lung disease studies to be performed in mouse models.

X-ray-based lung function measurement reveals persistent loss of lung tissue elasticity in mice recovered from allergic airway inflammation

Chronic asthma patients experience difficulties even years after the inciting allergen. Although studies in small animal asthma models have enormously advanced progress in uncovering the mechanisms of inception and development of the disease, little is known about the processes involved in the persistence of asthma symptoms in the absence of allergen exposure. Long-term asthma mouse models have so far been scarce or not been able to reproduce the findings in patients. Here we used a common ovalbumin-induced acute allergic airway inflammation mouse model to study lung function and remodeling after a 4-mo recovery period. We show by X-ray-based lung function measurements that the recovered mice continue to show impaired lung function by displaying significant air trapping compared with controls. High-resolution synchrotron phase-contrast computed tomography of structural alterations and diaphragm motion analysis suggest that these changes in pulmonary function are the result of a pronounced loss in lung elasticity. Histology of lung sections confirmed that this is most likely caused by a decrease in elastic fibers, indicating that remodeling can develop or persist independent of acute inflammation and is closely related to a loss in lung function. Our findings demonstrate that this X-ray-based imaging platform has the potential to comprehensively and noninvasively unravel long-term effects in preclinical mouse models of allergic airway inflammation and thus benefits our understanding of chronic asthma.

Diverse Applications of Nanomedicine

The design and use of materials in the nanoscale size range for addressing medical and health-related issues continues to receive increasing interest. Research in nanomedicine spans a multitude of areas, including drug delivery, vaccine development, antibacterial, diagnosis and imaging tools, wearable devices, implants, high-throughput screening platforms, etc. using biological, nonbiological, biomimetic, or hybrid materials. Many of these developments are starting to be translated into viable clinical products. Here, we provide an overview of recent developments in nanomedicine and highlight the current challenges and upcoming opportunities for the field and translation to the clinic.

Nondestructive imaging of the internal microstructure of vessels and nerve fibers in rat spinal cord using phase-contrast synchrotron radiation microtomography

The spinal cord is the primary neurological link between the brain and other parts of the body, but unlike those of the brain, advances in spinal cord imaging have been challenged by the more complicated and inhomogeneous anatomy of the spine. Fortunately with the advancement of high technology, phase-contrast synchrotron radiation microtomography has become widespread in scientific research because of its ability to generate high-quality and high-resolution images. In this study, this method has been employed for nondestructive imaging of the internal microstructure of rat spinal cord. Furthermore, digital virtual slices based on phase-contrast synchrotron radiation were compared with conventional histological sections. The three-dimensional internal microstructure of the intramedullary arteries and nerve fibers was vividly detected within the same spinal cord specimen without the application of a stain or contrast agent or sectioning. With the aid of image post-processing, an optimization of vessel and nerve fiber images was obtained. The findings indicated that phase-contrast synchrotron radiation microtomography is unique in the field of three-dimensional imaging and sets novel standards for pathophysiological investigations in various neurovascular diseases.

X-Ray based Lung Function measurement-a sensitive technique to quantify lung function in allergic airway inflammation mouse models

In mice, along with the assessment of eosinophils, lung function measurements, most commonly carried out by plethysmography, are essential to monitor the course of allergic airway inflammation, to examine therapy efficacy and to correlate animal with patient data. To date, plethysmography techniques either use intubation and/or restraining of the mice and are thus invasive, or are limited in their sensitivity. We present a novel unrestrained lung function method based on low-dose planar cinematic x-ray imaging (X-Ray Lung Function, XLF) and demonstrate its performance in monitoring OVA induced experimental allergic airway inflammation in mice and an improved assessment of the efficacy of the common treatment dexamethasone. We further show that XLF is more sensitive than unrestrained whole body plethysmography (UWBP) and that conventional broncho-alveolar lavage and histology provide only limited information of the efficacy of a treatment when compared to XLF. Our results highlight the fact that a multi-parametric imaging approach as delivered by XLF is needed to address the combined cellular, anatomical and functional effects that occur during the course of asthma and in response to therapy.

Structural and transcriptomic response to antenatal corticosteroids in an Erk3-null mouse model of respiratory distress

BACKGROUND

Neonatal respiratory distress syndrome in preterm infants is a leading cause of neonatal death. Pulmonary insufficiency-related infant mortality rates have improved with antenatal glucocorticoid treatment and neonatal surfactant replacement. However, the mechanism of glucocorticoid-promoted fetal lung maturation is not understood fully, despite decades of clinical use. We previously have shown that genetic deletion of Erk3 in mice results in growth restriction, cyanosis, and early neonatal lethality because of pulmonary immaturity and respiratory distress. Recently, we demonstrated that the addition of postnatal surfactant administration to antenatal dexamethasone treatment resulted in enhanced survival of neonatal Erk3-null mice.

OBJECTIVE

To better understand the molecular underpinnings of corticosteroid-mediated lung maturation, we used high-throughput transcriptomic and high-resolution morphologic analysis of the murine fetal lung. We sought to examine the alterations in fetal lung structure and function that are associated with neonatal respiratory distress and antenatal glucocorticoid treatment.

STUDY DESIGN

Dexamethasone (0.4 mg/kg) or saline solution was administered to pregnant dams on embryonic days 16.5 and 17.5. Fetal lungs were collected and analyzed by microCT and RNA-seq for differential gene expression and pathway interactions with genotype and treatment. Results from transcriptomic analysis guided further investigation of candidate genes with the use of immunostaining in murine and human fetal lung tissue.

RESULTS

Erk3(-/-) mice exhibited atelectasis with decreased overall porosity and saccular space relative to wild type, which was ameliorated by glucocorticoid treatment. Of 596 differentially expressed genes (q < 0.05) that were detected by RNA-seq, pathway analysis revealed 36 genes (q < 0.05) interacting with dexamethasone, several with roles in lung development, which included corticotropin-releasing hormone and surfactant protein B. Corticotropin-releasing hormone protein was detected in wild-type and Erk3(-/-) lungs at E14.5, with significantly temporally altered expression through embryonic day 18.5. Antenatal dexamethasone attenuated corticotropin-releasing hormone at embryonic day 18.5 in both wild-type and Erk3(-/-) lungs (0.56-fold and 0.67-fold; P < .001). Wild type mice responded to glucocorticoid administration with increased pulmonary surfactant protein B (P = .003). In contrast, dexamethasone treatment in Erk3(-/-) mice resulted in decreased surfactant protein B (P = .012). In human validation studies, we confirmed that corticotropin-releasing hormone protein is present in the fetal lung at 18 weeks of gestation and increases in expression with progression towards viability (22 weeks of gestation; P < .01).

CONCLUSION

Characterization of whole transcriptome gene expression revealed glucocorticoid-mediated regulation of corticotropin-releasing hormone and surfactant protein B via Erk3-independent and -dependent mechanisms, respectively. We demonstrated for the first time the expression and temporal regulation of corticotropin-releasing hormone protein in midtrimester human fetal lung. This unique model allows the effects of corticosteroids on fetal pulmonary morphologic condition to be distinguished from functional gene pathway regulation. These findings implicate Erk3 as a potentially important molecular mediator of antenatal glucocorticoid action in promoting surfactant protein production in the preterm neonatal lung and expanding our understanding of key mechanisms of clinical therapy to improve neonatal survival.

Tracking of Inhaled Near-Infrared Fluorescent Nanoparticles in Lungs of SKH-1 Mice with Allergic Airway Inflammation

Molecular imaging of inflammatory lung diseases, such as asthma, has been limited to date. The recruitment of innate immune cells to the airways is central to the inflammation process. This study exploits these cells for imaging purposes within the lung, using inhaled polystyrene nanoparticles loaded with the near-infrared fluorescence dye Itrybe (Itrybe-NPs). By means of in vivo and ex vivo fluorescence reflectance imaging of an ovalbumin-based allergic airway inflammation (AAI) model in hairless SKH-1 mice, we show that subsequent to intranasal application of Itrybe-NPs, AAI lungs display fluorescence intensities significantly higher than those in lungs of control mice for at least 24 h. Ex vivo immunofluorescence analysis of lung tissue demonstrates the uptake of Itrybe-NPs predominantly by CD68(+)CD11c(+)ECF-L(+)MHCII(low) cells, identifying them as alveolar M2 macrophages in the peribronchial and alveolar areas. The in vivo results were validated by confocal microscopy, overlapping tile analysis, and flow cytometry, showing an amount of Itrybe-NP-containing macrophages in lungs of AAI mice significantly larger than that in controls. A small percentage of NP-containing cells were identified as dendritic cells. Flow cytometry of tracheobronchial lymph nodes showed that Itrybe-NPs were negligible in lung draining lymph nodes 24 h after inhalation. This imaging approach may advance preclinical monitoring of AAI in vivo over time and aid the investigation of the role that macrophages play during lung inflammation. Furthermore, it allows for tracking of inhaled nanoparticles and can hence be utilized for studies of the fate of potential new nanotherapeutics.

Phase-contrast computed tomography for quantification of structural changes in lungs of asthma mouse models of different severity

Lung imaging in mouse disease models is crucial for the assessment of the severity of airway disease but remains challenging due to the small size and the high porosity of the organ. Synchrotron inline free-propagation phase-contrast computed tomography (CT) with its intrinsic high soft-tissue contrast provides the necessary sensitivity and spatial resolution to analyse the mouse lung structure in great detail. Here, this technique has been applied in combination with single-distance phase retrieval to quantify alterations of the lung structure in experimental asthma mouse models of different severity. In order to mimic an in vivo situation as close as possible, the lungs were inflated with air at a constant physiological pressure. Entire mice were embedded in agarose gel and imaged using inline free-propagation phase-contrast CT at the SYRMEP beamline (Synchrotron Light Source, `Elettra', Trieste, Italy). The quantification of the obtained phase-contrast CT data sets revealed an increasing lung soft-tissue content in mice correlating with the degree of the severity of experimental allergic airways disease. In this way, it was possible to successfully discriminate between healthy controls and mice with either mild or severe allergic airway disease. It is believed that this approach may have the potential to evaluate the efficacy of novel therapeutic strategies that target airway remodelling processes in asthma.

Phase-contrast zoom tomography reveals precise locations of macrophages in mouse lungs

We have performed x-ray phase-contrast tomography on mouse lung tissue. Using a divergent x-ray beam generated by nanoscale focusing, we used zoom tomography to produce three-dimensional reconstructions with selectable magnification, resolution, and field of view. Thus, macroscopic tissue samples extending over several mm can be studied in sub-cellular-level structural detail. The zoom capability and, in particular, the high dose efficiency are enabled by the near-perfect exit wavefront of an optimized x-ray waveguide channel. In combination with suitable phase-retrieval algorithms, challenging radiation-sensitive and low-contrast samples can be reconstructed with minimal artefacts. The dose efficiency of the method is demonstrated by the reconstruction of living macrophages both with and without phagocytized contrast agents. We also used zoom tomography to visualize barium-labelled macrophages in the context of morphological structures in asthmatic and healthy mouse lung tissue one day after intratracheal application. The three-dimensional reconstructions showed that the macrophages predominantly localized to the alveoli, but they were also found in bronchial walls, indicating that these cells might be able to migrate from the lumen of the bronchi through the epithelium.