Low volume ventilation of pre-injured lungs degrades lung function via stress concentration and progressive alveolar collapse

Mechanical ventilation can cause ventilation-induced lung injury (VILI). The concept of stress concentrations suggests that surfactant dysfunction-induced microatelectases might impose injurious stresses on adjacent, open alveoli and function as germinal centers for injury propagation. The aim of the present study was to quantify the histopathological pattern of VILI progression and to test the hypothesis that injury progresses at the interface between microatelectases and ventilated lung parenchyma during low positive end-expiratory pressure (PEEP) ventilation. Bleomycin was used to induce lung injury with microatelectases in rats. Lungs were then mechanically ventilated for up to 6 hours at PEEP=1cmH2O and compared to bleomycin treated group ventilated protectively with PEEP=5cmH2O to minimize microatelectases. Lung mechanics were measured during ventilation. Afterwards lungs were fixed at end-inspiration or end-expiration for design-based stereology. Prior to VILI, bleomycin challenge reduced the number of open alveoli (N(alvair,par)) by 29%. No differences between end-inspiration and end-expiration were observed. Collapsed alveoli clustered in areas with a radius up to 56 µm. After PEEP=5cmH2O ventilation for 6 hours, N(alvair,par) remained stable while PEEP=1cmH2O ventilation led to an additional loss of aerated alveoli by 26%, mainly due to collapse, with a small fraction partly edema filled. Alveolar loss strongly correlated to worsening of tissue elastance, quasi-static compliance and inspiratory capacity. The radius of areas of collapsed alveoli increased to 94 µm, suggesting growth of the microatelectases. These data provide evidence that alveoli become unstable in neighborhood of microatelectases which most likely occurs due to by stress concentration-induced local vascular leak and surfactant dysfunction.

The fix is not yet in: recommendation for fixation of lungs within physiologic/pathophysiologic volume range in preclinical pulmonary structure-function studies

Quantitative characterization of lung structures by morphometric or stereologic analysis of histologic sections is a powerful means of elucidating pulmonary structure-function relations. The overwhelming majority of studies, however, fix lungs for histology at pressures outside the physiologic/pathophysiologic respiratory volume range. Thus valuable information is being lost. In this perspective article, we argue that investigators performing pulmonary histologic studies should consider whether the aims of their studies would benefit from fixation at functional transpulmonary pressures, particular those of end-inspiration and end-expiration. We survey the pressures at which lungs are typically fixed in preclinical structure-function studies; provide examples of conditions that would benefit from histologic evaluation at functional lung volumes; summarize available fixation methods; discuss alternative imaging modalities; and discuss challenges to implementing the suggested approach and means of addressing those challenges. We aim to persuade investigators that modifying or complementing the traditional histologic approach by fixing lungs at minimal and maximal functional volumes could enable new understanding of pulmonary structure-function relations.

Exploring alveolar recruitability using positive end-expiratory pressure in mice overexpressing TGF-β1: a structure-function analysis

Pre-injured lungs are prone to injury progression in response to mechanical ventilation. Heterogeneous ventilation due to (micro)atelectases imparts injurious strains on open alveoli (known as volutrauma). Hence, recruitment of (micro)atelectases by positive end-expiratory pressure (PEEP) is necessary to interrupt this vicious circle of injury but needs to be balanced against acinar overdistension. In this study, the lung-protective potential of alveolar recruitment was investigated and balanced against overdistension in pre-injured lungs. Mice, treated with empty vector (AdCl) or adenoviral active TGF-β1 (AdTGF-β1) were subjected to lung mechanical measurements during descending PEEP ventilation from 12 to 0 cmH2O. At each PEEP level, recruitability tests consisting of two recruitment maneuvers followed by repetitive forced oscillation perturbations to determine tissue elastance (H) and damping (G) were performed. Finally, lungs were fixed by vascular perfusion at end-expiratory airway opening pressures (Pao) of 20, 10, 5 and 2 cmH2O after a recruitment maneuver, and processed for design-based stereology to quantify derecruitment and distension. H and G were significantly elevated in AdTGF-β1 compared to AdCl across PEEP levels. H was minimized at PEEP = 5-8 cmH2O and increased at lower and higher PEEP in both groups. These findings correlated with increasing septal wall folding (= derecruitment) and reduced density of alveolar number and surface area (= distension), respectively. In AdTGF-β1 exposed mice, 27% of alveoli remained derecruited at Pao = 20 cmH2O. A further decrease in Pao down to 2 cmH2O showed derecruitment of an additional 1.1 million alveoli (48%), which was linked with an increase in alveolar size heterogeneity at Pao = 2-5 cmH2O. In AdCl, decreased Pao resulted in septal folding with virtually no alveolar collapse. In essence, in healthy mice alveoli do not derecruit at low PEEP ventilation. The potential of alveolar recruitability in AdTGF-β1 exposed mice is high. H is optimized at PEEP 5-8 cmH2O. Lower PEEP folds and larger PEEP stretches septa which results in higher H and is more pronounced in AdTGF-β1 than in AdCl. The increased alveolar size heterogeneity at Pao = 5 cmH2O argues for the use of PEEP = 8 cmH2O for lung protective mechanical ventilation in this animal model.

The expression of the surfactant proteins SP-A and SP-B during postnatal alveolarization of the rat lung

OBJECTIVE

Surfactant-specific proteins (SP) are responsible for the functional and structural integrity as well as for the stabilization of the intra-alveolar surfactant. Morphological lung maturation starts in rat lungs after birth. The aim of this study was to investigate whether the expression of the hydrophilic SP-A and the hydrophobic SP-B is associated with characteristic postnatal changes characterizing morphological lung maturation.

METHODS

Stereological methods were performed on the light microscope. Using immunohistochemical and molecular biological methods (Western Blot, RT-qPCR), the SP-A and SP-B of adult rat lungs and of those with different postnatal developmental stages (3, 7, 14 and 21 days after birth) were characterized.

RESULTS

As signs of alveolarization the total septal surface and volume increased and the septal thickness decreased. The significantly highest relative surface fraction of SP-A labeled alveolar epithelial cells type II (AEII) was found together with the highest relative SP-A gene expression before the alveolarization (3th postnatal day). With the downregulation of SP-A gene expression during and after alveolarization (between postnatal days 7 and 14), the surface fraction of the SP-A labeled AEII also decreased, so they are lowest in adult animals. The surface fraction of SP-B labeled AEII and the SP-B gene expression showed the significantly highest levels in adults, the protein expression increased also significantly at the end of morphological lung maturation. There were no alterations in the SP-B expression before and during alveolarization until postnatal day 14. The protein expression as well as the gene expression of SP-A and SP-B correlated very well with the total surface of alveolar septa independent of the postnatal age.

CONCLUSION

The expression of SP-A and SP-B is differentially associated with morphological lung maturation and correlates with increased septation of alveoli as indirect clue for alveolarization.

Multilamellated Basement Membranes in the Capillary Network of Alveolar Capillary Dysplasia

A minimal diffusion barrier is key to the pulmonary gas exchange. In alveolar capillary dysplasia (ACD), a rare genetically driven disease of early infancy, this crucial fibrovascular interface is compromised while the underlying pathophysiology is insufficiently understood. Recent in-depth analyses of vascular alterations in adult lung disease encouraged researchers to extend these studies to ACD and compare the changes of the microvasculature. Lung tissue samples of children with ACD (n = 12), adults with non-specific interstitial pneumonia (n = 12), and controls (n = 20) were studied using transmission electron microscopy, single-gene sequencing, immunostaining, exome sequencing, and broad transcriptome profiling. In ACD, pulmonary capillary basement membranes were hypertrophied, thickened, and multilamellated. Transcriptome profiling revealed increased CDH5, COL4A1, COL15A1, PTK2B, and FN1 and decreased VIT expression, confirmed by immunohistochemistry. In contrast, non-specific interstitial pneumonia samples showed a regular basement membrane architecture with preserved VIT expression but also increased COL15A1+ vessels. This study provides insight into the ultrastructure and pathophysiology of ACD. The lack of normally developed lung capillaries appeared to cause a replacement by COL15A1+ vessels, a mechanism recently described in interstitial lung disease. The VIT loss and FN1 overexpression might contribute to the unique appearance of basement membranes in ACD. Future studies are needed to explore the therapeutic potential of down-regulating the expression of FN1 and balancing VIT deficiency.

The use of cultured human alveolar basal cells to mimic honeycomb formation in idiopathic pulmonary fibrosis

BACKGROUND

Honeycomb cysts (HC) within the alveolar region are distinct histopathological features in the lungs of idiopathic pulmonary fibrosis (IPF) patients. HC are lined with a single-or stratified layer of basal cells (BC), or with a bronchiolar-like epithelium composed of basal-, ciliated- and secretory epithelial cells. By using cultured IPF patient-derived alveolar BC, we aimed to establish an in vitro- and in vivo model to mimic HC formation in IPF. We (1) optimized conditions to culture and propagate IPF patient-derived alveolar BC, (2) cultured the cells on an air liquid interface (ALI) or in a three dimensional (3D) organoid model, and (3) investigated the cells` behavior after instillation into bleomycin-challenged mice.

METHODS

Alveolar BC were cultured from peripheral IPF lung tissue and grown on tissue-culture treated plastic, an ALI, or in a 3D organoid model. Furthermore, cells were instilled into bleomycin-challenged NRG mice. Samples were analyzed by TaqMan RT-PCR, immunoblotting, immunocytochemistry/immunofluorescence (ICC/IF), or immunohistochemistry (IHC)/IF. Mann-Whitney tests were performed using GraphPad Prism software.

RESULTS

Cultured alveolar BC showed high expression of canonical basal cell markers (TP63, keratin (KRT)5, KRT14, KRT17), robust proliferation, and wound closure capacity. The cells could be cryopreserved and propagated for up to four passages without a significant loss of basal cell markers. When cultured on an ALI or in a 3D organoid model, alveolar BC differentiated to ciliated- and secretory epithelial cells. When instilled into bleomycin-challenged mice, human alveolar BC cells formed HC-like structures composed of human basal-, and secretory epithelial cells within the mouse parenchyma.

CONCLUSION

IPF patient-derived alveolar BC on an ALI, in 3D organoids or after instillation into bleomycin-challenged mice form HC-like structures that closely resemble HC within the IPF lung. These models therefore represent powerful tools to study honeycomb formation, and its potential therapeutic inhibition in IPF.

Diagnosis of medial meniscal lesions in the canine stifle using multidetector computed tomographic positive-contrast arthrography

OBJECTIVE

To assess diagnostic value and clinical utility of multidetector computed tomographic positive contrast arthrography (CTA) for meniscal lesions in dogs.

STUDY DESIGN

Prospective case series.

STUDY POPULATION

Client-owned dogs (n = 55) with cranial cruciate ligament injuries.

METHODS

Sedated dogs underwent CTA using a 16-slice scanner, and subsequently received mini-medial arthrotomy for meniscal assessment. Scans were anonymized, randomized, and reviewed twice for meniscal lesions by three independent observers with varying experience. Results were compared with surgical findings. Reproducibility and repeatability were assessed with kappa statistics, intraobserver changes in diagnosis by McNemar's test, and interobserver differences using Cochran's Q test. Test performance was calculated using sensitivity, specificity, proportion correctly identified, and positive and negative predictive values and likelihood ratios.

RESULTS

Analysis was based on 52 scans from 44 dogs. Sensitivity for identifying meniscal lesions was 0.62-1.00 and specificity was 0.70-0.96. Intraobserver agreement was 0.50-0.78, and interobserver agreement was 0.47-0.83. There was a significant change between readings one and two for the least experienced observers (p < .05). The sum of sensitivity and specificity exceeded 1.5 for both readings and all observers.

CONCLUSION

Diagnostic performance was suitable for identifying meniscal lesions. An effect of experience and learning was seen in this study.

Differential effects of two-hit models of acute and ventilator-induced lung injury on lung structure, function, and inflammation

Acute respiratory distress syndrome (ARDS) and acute lung injury have a diverse spectrum of causative factors including sepsis, aspiration of gastric contents, and near drowning. Clinical management of severe lung injury typically includes mechanical ventilation to maintain gas exchange which can lead to ventilator-induced lung injury (VILI). The cause of respiratory failure is acknowledged to affect the degree of lung inflammation, changes in lung structure, and the mechanical function of the injured lung. However, these differential effects of injury and the role of etiology in the structure-function relationship are not fully understood. To address this knowledge gap we caused lung injury with intratracheal hydrochloric acid (HCL) or endotoxin (LPS) 2 days prior to ventilation or with an injurious lavage (LAV) immediately prior to ventilation. These injury groups were then ventilated with high inspiratory pressures and positive end expiratory pressure (PEEP) = 0 cmH2O to cause VILI and model the clinical course of ARDS followed by supportive ventilation. The effects of injury were quantified using invasive lung function measurements recorded during PEEP ladders where the end-expiratory pressure was increased from 0 to 15 cm H2O and decreased back to 0 cmH2O in steps of 3 cmH2O. Design-based stereology was used to quantify the parenchymal structure of lungs air-inflated to 2, 5, and 10 cmH2O. Pro-inflammatory gene expression was measured with real-time quantitative polymerase chain reaction and alveolocapillary leak was estimated by measuring bronchoalveolar lavage protein content. The LAV group had small, stiff lungs that were recruitable at higher pressures, but did not demonstrate substantial inflammation. The LPS group showed septal swelling and high pro-inflammatory gene expression that was exacerbated by VILI. Despite widespread alveolar collapse, elastance in LPS was only modestly elevated above healthy mice (CTL) and there was no evidence of recruitability. The HCL group showed increased elastance and some recruitability, although to a lesser degree than LAV. Pro-inflammatory gene expression was elevated, but less than LPS, and the airspace dimensions were reduced. Taken together, those data highlight how different modes of injury, in combination with a 2nd hit of VILI, yield markedly different effects.

CNP-miR146a improves outcomes in a two-hit acute- and ventilator-induced lung injury model

Acute respiratory distress syndrome (ARDS) has high mortality (~40 %) and requires the lifesaving intervention of mechanical ventilation. A variety of systemic inflammatory insults can progress to ARDS, and the inflamed and injured lung is susceptible to ventilator-induced lung injury (VILI). Strategies to mitigate the inflammatory response while restoring pulmonary function are limited, thus we sought to determine if treatment with CNP-miR146a, a conjugate of novel free radical scavenging cerium oxide nanoparticles (CNP) to the anti-inflammatory microRNA (miR)-146a, would protect murine lungs from acute lung injury (ALI) induced with intratracheal endotoxin and subsequent VILI. Lung injury severity and treatment efficacy were evaluated via lung mechanical function, relative gene expression of inflammatory biomarkers, and lung morphometry (stereology). CNP-miR146a reduced the severity of ALI and slowed the progression of VILI, evidenced by improvements in inflammatory biomarkers, atelectasis, gas volumes in the parenchymal airspaces, and the stiffness of the pulmonary system.

Acinar micromechanics in health and lung injury: what we have learned from quantitative morphology

Within the pulmonary acini ventilation and blood perfusion are brought together on a huge surface area separated by a very thin blood-gas barrier of tissue components to allow efficient gas exchange. During ventilation pulmonary acini are cyclically subjected to deformations which become manifest in changes of the dimensions of both alveolar and ductal airspaces as well as the interalveolar septa, composed of a dense capillary network and the delicate tissue layer forming the blood-gas barrier. These ventilation-related changes are referred to as micromechanics. In lung diseases, abnormalities in acinar micromechanics can be linked with injurious stresses and strains acting on the blood-gas barrier. The mechanisms by which interalveolar septa and the blood-gas barrier adapt to an increase in alveolar volume have been suggested to include unfolding, stretching, or changes in shape other than stretching and unfolding. Folding results in the formation of pleats in which alveolar epithelium is not exposed to air and parts of the blood-gas barrier are folded on each other. The opening of a collapsed alveolus (recruitment) can be considered as an extreme variant of septal wall unfolding. Alveolar recruitment can be detected with imaging techniques which achieve light microscopic resolution. Unfolding of pleats and stretching of the blood-gas barrier, however, require electron microscopic resolution to identify the basement membrane. While stretching results in an increase of the area of the basement membrane, unfolding of pleats and shape changes do not. Real time visualization of these processes, however, is currently not possible. In this review we provide an overview of septal wall micromechanics with focus on unfolding/folding as well as stretching. At the same time we provide a state-of-the-art design-based stereology methodology to quantify microarchitecture of alveoli and interalveolar septa based on different imaging techniques and design-based stereology.

Analysis of the alveolar shape in 3-D

Mechanical forces affect the alveolar shape, depending on location and tissue composition, and vary during the respiratory cycle. This study performs alveolar morphomics in different lobes of human lungs using models generated from three-dimensional (3-D) micro-computed tomography (microCT) images. Cylindrical tissue samples (1.6 cm × 2 cm) were extracted from two nontransplantable donor lungs (one ex-smoker and one smoker, 3 samples per subject) that were air-inflated and frozen solid in liquid nitrogen vapor. Samples were scanned with microCT (11 µm/voxel). Within representative cubic regions of interest (5.5 mm edge length), alveoli were segmented to produce corresponding 3-D models from which quantitative data were obtained. The surface of segmented alveoli (n_alv_total = 23,587) was divided into individual planar surfaces (facets) and angles between facet normals were calculated. Moreover, the number of neighboring alveoli was estimated for every alveolus. In this study, we examined intraindividual differences in alveolar morphology, which were reproducible in the lungs of two subjects. The main aspects are higher mean alveolar volumes (v_alv: 6.64 × 10⁶ and 6.63 × 10⁶ µm³ vs. 5.78 × 10⁶ and 6.29 × 10⁶ µm³) and surface sizes (s_alv: 0.19 and 0.18 mm² vs. 0.17 mm² in both lower lobes) in both upper lung lobes compared with the lower lobes. An increasing number of facets (f_alv) from top to bottom (12 and 14 in the upper lobes; 14 and 15 in the lower lobes), as well as a decreasing number of alveolar neighbors (nei_alv: 9 and 8 in the upper lobes; 8 and 7 in the lower lobes) from the upper lobes to the lower lobes were observed. We could observe an increasing ratio of alveolar entrance size to the surface size of the alveoli from top to bottom (S_ratio_alv: 0.71 and 0.64 in the upper lobes, 0.73 and 0.70 in the lower lobes). The angles between facet normals (ang_alv) were larger in the upper lobes (67.72° and 62.44°) of both lungs than in the lower lobes (66.19° and 61.30°). By using this new approach of analyzing alveolar 3-D data, which enables the estimation of facet, neighbor, and shape characteristics, we aimed to establish the baseline measures for in-depth studies of mechanical conditions and morphology.

EFSUMB Clinical Practice Guidelines for Point-of-Care Ultrasound: Part One (Common Heart and Pulmonary Applications) SHORT VERSION

OBJECTIVE

 To evaluate the evidence and produce a summary and recommendations for the most common heart and lung point-of-care ultrasound (PoCUS).

METHODS

 We reviewed 10 clinical domains/questions related to common heart and lung applications of PoCUS. Following review of the evidence, a summary and recommendations were produced, including assigning levels of evidence (LoE) and grading of recommendation, assessment, development, and evaluation (GRADE). 38 international experts, the expert review group (ERG), were invited to review the evidence presented for each question. A level of agreement of over 75 % was required to progress to the next section. The ERG then reviewed and indicated their level of agreement of the summary and recommendation for each question (using a 5-point Likert scale), which was approved in the case of a level of agreement of greater than 75 %. A level of agreement was defined as a summary of "strongly agree" and "agree" on the Likert scale responses.

FINDINGS AND RECOMMENDATIONS

 One question achieved a strong consensus for an assigned LoE of 3 and a weak GRADE recommendation (question 1), the remaining 9 questions achieved broad agreement with an assigned LoE of 4 and a weak GRADE recommendation (question 2), three achieved an LoE of 3 with a weak GRADE recommendation (questions 3-5), three achieved an LoE of 3 with a strong GRADE recommendation (questions 6-8) and the remaining two were assigned an LoE of 2 with a strong GRADE recommendation (questions 9 and 10).

CONCLUSION

 These consensus-derived recommendations should aid clinical practice and highlight areas of further research for PoCUS in acute settings.

EFSUMB Clinical Practice Guidelines for Point-of-Care Ultrasound: Part One (Common Heart and Pulmonary Applications) LONG VERSION

AIMS

 To evaluate the evidence and produce a summary and recommendations for the most common heart and lung applications of point-of-care ultrasound (PoCUS).

METHODS

 We reviewed 10 clinical domains/questions related to common heart and lung applications of PoCUS. Following review of the evidence, a summary and recommendation were produced, including assignment of levels of evidence (LoE) and grading of the recommendation, assessment, development, and evaluation (GRADE). 38 international experts, the expert review group (ERG), were invited to review the evidence presented for each question. A level of agreement of over 75 % was required to progress to the next section. The ERG then reviewed and indicated their level of agreement regarding the summary and recommendation for each question (using a 5-point Likert scale), which was approved if a level of agreement of greater than 75 % was reached. A level of agreement was defined as a summary of "strongly agree" and "agree" on the Likert scale responses.

FINDINGS AND RECOMMENDATIONS

 One question achieved a strong consensus for an assigned LoE of 3 and a weak GRADE recommendation (question 1). The remaining 9 questions achieved broad agreement with one assigned an LoE of 4 and weak GRADE recommendation (question 2), three achieving an LoE of 3 with a weak GRADE recommendation (questions 3-5), three achieved an LoE of 3 with a strong GRADE recommendation (questions 6-8), and the remaining two were assigned an LoE of 2 with a strong GRADE recommendation (questions 9 and 10).

CONCLUSION

 These consensus-derived recommendations should aid clinical practice and highlight areas of further research for PoCUS in acute settings.

Multi-apical polarity of alveolar stem cells and their dynamics during lung development and regeneration

Epithelial cells of diverse tissues are characterized by the presence of a single apical domain. In the lung, electron microscopy studies have suggested that alveolar type-2 epithelial cells (AT2s) en face multiple alveolar sacs. However, apical and basolateral organization of the AT2s and their establishment during development and remodeling after injury repair remain unknown. Thick tissue imaging and electron microscopy revealed that a single AT2 can have multiple apical domains that enface multiple alveoli. AT2s gradually establish multi-apical domains post-natally, and they are maintained throughout life. Lineage tracing, live imaging, and selective cell ablation revealed that AT2s dynamically reorganize multi-apical domains during injury repair. Single-cell transcriptome signatures of residual AT2s revealed changes in cytoskeleton and cell migration. Significantly, cigarette smoke and oncogene activation lead to dysregulation of multi-apical domains. We propose that the multi-apical domains of AT2s enable them to be poised to support the regeneration of a large array of alveolar sacs.

Anti-Fibrotic Effect of SDF-1β Overexpression in Bleomycin-Injured Rat Lung

Rational: Idiopathic pulmonary fibrosis (IPF) is a progressive interstitial lung disease and is associated with high mortality due to a lack of effective treatment. Excessive deposition of the extracellular matrix by activated myofibroblasts in the alveolar space leads to scar formation that hinders gas exchange. Therefore, selectively removing activated myofibroblasts with the aim to repair and remodel fibrotic lungs is a promising approach. Stromal-derived growth factor (SDF-1) is known to stimulate cellular signals which attract stem cells to the site of injury for tissue repair and remodeling. Here, we investigate the effect of overexpression of SDF-1β on lung structure using the bleomycin-injured rat lung model. Methods: Intratracheal administration of bleomycin was performed in adult male rats (F344). Seven days later, in vivo electroporation-mediated gene transfer of either SDF-1β or the empty vector was performed. Animals were sacrificed seven days after gene transfer and histology, design-based stereology, flow cytometry, and collagen measurement were performed on the tissue collected. For in vitro experiments, lung fibroblasts obtained from IPF patients were used. Results: Seven days after SDF-1β gene transfer to bleomycin-injured rat lungs, reduced total collagen, reduced collagen fibrils, improved histology and induced apoptosis of myofibroblasts were observed. Furthermore, it was revealed that TNF-α mediates SDF-1β-induced apoptosis of myofibroblasts; moreover, SDF-1β overexpression increased alveolar epithelial cell numbers and proliferation in vivo and also induced their migration in vitro. Conclusions: Our study demonstrates a new antifibrotic mechanism of SDF-1β overexpression and suggests SDF-1β as a potential new approach for the treatment of lung fibrosis.

Teaching gross anatomy during the Covid-19 pandemic: Effects on medical students' gain of knowledge, confidence levels and pandemic-related concerns

For medical students the dissection course is the preferred method to learn gross anatomy. However, the added value of active cadaver dissection on knowledge gain in multimodal curricula offering a diversity of e-learning resources is unknown. The Covid-19-related lockdown forced educators to replace the dissection course by e-learning resources. At the end of the summer term 2020 loosening of pandemic-related regulations allowed offering a compact, voluntary active dissection course of the head-neck region to first-year medical students at Hannover Medical School. A study was conducted comparing a dissection group (G1, n = 115) and a non-dissection group (G2, n = 23). Knowledge gain and confidence level were measured with a multiple-choice (MC-)test. The use of e-learning resources was recorded. A questionnaire measured motivation, interest and level of concern regarding Covid-19 and anatomy teaching. No differences between groups were found regarding motivation and interest in anatomy of the head-neck region. G2, however, had significantly higher concerns regarding the Covid-19 pandemic than G1. Neither before nor after the educational intervention, differences in the scores of the MC-test were found. However, after the course G1 answered more MC-questions with highest confidence level than G2 (6.7 ± 6.0 vs. 3.6 ± 4.6, p < 0.05) and demonstrated by trend an increased improvement in the scores of image-based questions (30.8 ± 18.2 % vs. 17.1 ± 14.8 %, p = 0.06). In general, frequent users of online quizzes, a part of the e-learning resources, scored significantly better in the knowledge test. Active dissection improves self-assurance to identify anatomical structures and should be re-implemented in multimodal, blended-learning-based anatomical curricula in the post-pandemic era.

Use of Helicopters to Reduce Health Care System Delay in Patients With ST-Elevation Myocardial Infarction Admitted to an Invasive Center

Timely reperfusion in ST-elevation myocardial infarction (STEMI) is essential. This study aimed to evaluate the reduction in system delay (time from emergency medical service [EMS] call to primary percutaneous coronary intervention [PPCI]) in patients with STEMI when using helicopter EMS (HEMS) rather than ground-based EMS (GEMS). This was a retrospective, nationwide cohort study of consecutive patients with STEMI treated with PPCI at 5 PPCI centers in Denmark. Polynomial spline curves were constructed to describe the association between system delay and distance to the PPCI center stratified by transportation mode. A total of 26,433 patients with STEMI were treated with PPCI between January 1, 1999, and December 31, 2016. In 16,436 patients field triaged directly to the PPCI center, the proportion treated within 120 minutes of the EMS call was 75% for those living 0 to 25 km from the PPCI center compared with 65% for all patients transported by GEMS (median transport distance 50 km [interquartile range 23 to 90]) and 64% for all patients transported by HEMS (median transport distance 119 km [interquartile range 99 to 142]). The estimated reduction in system delay owed to using HEMS rather than GEMS was 14, 16, 20, and 29 minutes for patients living 75, 100, 125, and 170 km from a PPCI center. In conclusion, this study confirmed that using HEMS ensures that most patients with STEMI, living up to 170 km from a PPCI center, can be treated within 120 minutes of their EMS call provided they are field triaged directly to the PPCI center.

Basal-Like Cell-Conditioned Medium Exerts Anti-Fibrotic Effects In Vitro and In Vivo

In idiopathic pulmonary fibrosis (IPF), basal-like cells are atypically present in the alveolar region, where they may affect adjacent stromal cells by paracrine mechanisms. We here aimed to confirm the presence of basal-like cells in peripheral IPF lung tissue in vivo, to culture and characterize the cells in vitro, and to investigate their paracrine effects on IPF fibroblasts in vitro and in bleomycin-injured rats in vivo. Basal-like cells are mainly localized in areas of pathological bronchiolization or honeycomb cysts in peripheral IPF lung tissue. Single-cell RNA sequencing (scRNA-seq) demonstrated an overall homogeneity, the expression of the basal cell markers cytokeratin KRT5 and KRT17, and close transcriptomic similarities to basal cells in the majority of cells cultured in vitro. Basal-like cells secreted significant levels of prostaglandin E2 (PGE2), and their conditioned medium (CM) inhibited alpha-smooth muscle actin (α-SMA) and collagen 1A1 (Col1A1) and upregulated matrix metalloproteinase-1 (MMP-1) and hepatocyte growth factor (HGF) by IPF fibroblasts in vitro. The instillation of CM in bleomycin-injured rat lungs resulted in reduced collagen content, improved lung architecture, and reduced α-SMA-positive cells. Our data suggested that basal-like cells may limit aberrant fibroblast activation and differentiation in IPF through paracrine mechanisms.

B Cells Are Not Involved in the Regulation of Adenoviral TGF-β1- or Bleomycin-Induced Lung Fibrosis in Mice

Idiopathic pulmonary fibrosis (IPF) is an irreversible, age-related diffuse parenchymal lung disease of poorly defined etiology. Many patients with IPF demonstrate distinctive lymphocytic interstitial infiltrations within remodeled lung tissue with uncertain pathogenetic relevance. Histopathological examination of explant lung tissue of patients with IPF revealed accentuated lymphoplasmacellular accumulations in close vicinity to, or even infiltrating, remodeled lung tissue. Similarly, we found significant accumulations of B cells interfused with T cells within remodeled lung tissue in two murine models of adenoviral TGF-β1 or bleomycin (BLM)-induced lung fibrosis. Such B cell accumulations coincided with significantly increased lung collagen deposition, lung histopathology, and worsened lung function in wild-type (WT) mice. Surprisingly, B cell-deficient µMT knockout mice exhibited similar lung tissue remodeling and worsened lung function upon either AdTGF-β1 or BLM as for WT mice. Comparative transcriptomic profiling of sorted B cells collected from lungs of AdTGF-β1- and BLM-exposed WT mice identified a large set of commonly regulated genes, but with significant enrichment observed for Gene Ontology terms apparently not related to lung fibrogenesis. Collectively, although we observed B cell accumulations in lungs of IPF patients as well as two experimental models of lung fibrosis, comparative profiling of characteristic features of lung fibrosis between WT and B cell-deficient mice did not support a major involvement of B cells in lung fibrogenesis in mice.

PACS2-TRPV1 axis is required for ER-mitochondrial tethering during ER stress and lung fibrosis

Endoplasmic reticulum (ER) and mitochondria (mito) play a vital role in alveolar type II cell (AEC2) homeostasis and are both stressed in patients with idiopathic pulmonary fibrosis (IPF). Up to now, no data are available with regard to ER–mito cross talk and tethering under conditions of IPF. We here demonstrate that ER–mitochondrial tethering is reduced upon experimental ER stress in vitro and in the IPF AECII ex vivo, and this is—at least in part—due to decreased phosphofurin acidic cluster sorting protein 2 (PACS-2, also called PACS2) protein levels. PACS2 levels are influenced by its interaction with the transient receptor potential cation channel subfamily V member 1 (TRPV1) and can be experimentally modified by the TRPV1-modulating drug capsaicin (CPS). Employing alveolar epithelial cells with overexpression of the terminal ER stress signaling factor Chop or the IPF-associated surfactant protein C mutation (SPC^Δexon4) in vitro, we observed a restoration of PACS2 levels upon treatment with CPS. Similarly, treatment of precision cut lung slices from IPF patients with CPS ex vivo forwarded similar effects. Importantly, in all models such kind of intervention also greatly reduced the extent of alveolar epithelial apoptosis. We therefore conclude that therapeutic targeting of the PACS2–TRPV1 axis represents an interesting novel, epithelial-protective approach in IPF.

Increased regional ventilation as early imaging marker for future disease progression of interstitial lung disease: a feasibility study

OBJECTIVES

Idiopathic pulmonary fibrosis (IPF) is a disease with a poor prognosis and a highly variable course. Pathologically increased ventilation-accessible by functional CT-is discussed as a potential predecessor of lung fibrosis. The purpose of this feasibility study was to investigate whether increased regional ventilation at baseline CT and morphological changes in the follow-up CT suggestive for fibrosis indeed occur in spatial correspondence.

METHODS

In this retrospective study, CT scans were performed at two time points between September 2016 and November 2020. Baseline ventilation was divided into four categories ranging from low, normal to moderately, and severely increased (C1-C4). Correlation between baseline ventilation and volume and density change at follow-up was investigated in corresponding voxels. The significance of the difference of density and volume change per ventilation category was assessed using paired t-tests with a significance level of p ≤ 0.05. The analysis was performed separately for normal (NAA) and high attenuation areas (HAA).

RESULTS

The study group consisted of 41 patients (73 ± 10 years, 36 men). In both NAA and HAA, significant increases of density and loss of volume were seen in areas of severely increased ventilation (C4) at baseline compared to areas of normal ventilation (C2, p < 0.001). In HAA, morphological changes were more heterogeneous compared to NAA.

CONCLUSION

Functional CT assessing the extent and distribution of lung parenchyma with pathologically increased ventilation may serve as an imaging marker to prospectively identify lung parenchyma at risk for developing fibrosis.

KEY POINTS

• Voxelwise correlation of serial CT scans suggests spatial correspondence between increased ventilation at baseline and structural changes at follow-up. • Regional assessment of pathologically increased ventilation at baseline has the potential to prospectively identify tissue at risk for developing fibrosis. • Presence and extent of pathologically increased ventilation may serve as an early imaging marker of disease activity.

Denying the Truth Does Not Change the Facts: A Systematic Analysis of Pseudoscientific Denial of Complex Regional Pain Syndrome

Purpose

Several articles have claimed that complex regional pain syndrome (CRPS) does not exist. Although a minority view, it is important to understand the arguments presented in these articles. We conducted a systematic literature search to evaluate the methodological quality of articles that claim CRPS does not exist. We then examined and refuted the arguments supporting this claim using up-to-date scientific literature on CRPS.

Methods

A systematic search was conducted in MEDLINE, EMBASE and Cochrane CENTRAL databases. Inclusion criteria for articles were (a) a claim made that CRPS does not exist or that CRPS is not a distinct diagnostic entity and (b) support of these claims with subsequent argument(s). The methodological quality of articles was assessed if possible.

Results

Nine articles were included for analysis: 4 narrative reviews, 2 personal views, 1 letter, 1 editorial and 1 case report. Seven points of controversy were used in these articles to argue that CRPS does not exist: 1) disagreement with the label “CRPS”; 2) the “unclear” pathophysiology; 3) the validity of the diagnostic criteria; 4) CRPS as a normal consequence of immobilization; 5) the role of psychological factors; 6) other identifiable causes for CRPS symptoms; and 7) the methodological quality of CRPS research.

Conclusion

The level of evidence for the claim that CRPS does not exist is very weak. Published accounts concluding that CRPS does not exist, in the absence of primary evidence to underpin them, can harm patients by encouraging dismissal of patients’ signs and symptoms.

Helicopter emergency medical services missions to islands and the mainland during a 3-year period in Denmark: a population-based study on patient and sociodemographic characteristics, comorbidity, and use of healthcare services

Background

The Danish Helicopter Emergency Medical Services (HEMS) is part of the Danish Emergency Medical Services System serving 5.7 million citizens with 1% living on islands not connected to the mainland by road. HEMS is dispatched based on pre-defined criteria including severity and urgency, and moreover to islands for less urgent cases, when rapid transport to further care is needed. The study aim was to characterize patient and sociodemographic factors, comorbidity and use of healthcare services for patients with HEMS missions to islands versus mainland.

Methods

Descriptive study of data from the HEMS database in a three-year period from 1 October 2014 to 30 September 2017. All missions in which a patient was either treated on scene or transported by HEMS were included.

Results

Of 5776 included HEMS missions, 1023 (17.7%) were island missions. In total, 90.2% of island missions resulted in patient transport by HEMS compared with 62.1% of missions to the mainland. Disease severity was serious or life-threatening in 34.7% of missions to islands compared with 65.1% of missions to mainland and less interventions were performed by HEMS on island missions. The disease pattern differed with more “Other diseases” registered on islands compared with the mainland where cardiovascular diseases and trauma were the leading causes of contact. Patients from islands were older than patients from the mainland. Sociodemographic characteristics varied between inhabiting island patients and mainland patients: more island patients lived alone, less were employed, more were retired, and more had low income. In addition, residing island patients had to a higher extend severe comorbidity and more contacts to general practitioners and hospitals compared with the mainland patients.

Conclusions

HEMS missions to islands count for 17.7% of HEMS missions and 90.2% of island missions result in patient transport. The island patients encountered by HEMS are less severely diseased or injured and interventions are less frequently performed. Residing island patients are older than mainland patients and have lower socioeconomic position, more comorbidities and a higher use of health care services. Whether these socio-economic differences result in longer hospital stay or higher mortality is still to be investigated.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13049-021-00963-6.

The common ABCA3E292V variant disrupts AT2 cell quality control and increases susceptibility to lung injury and aberrant remodeling

ATP-binding cassette class A3 (ABCA3) is a lipid transporter that plays a critical role in pulmonary surfactant function. The substitution of valine for glutamic acid at codon 292 (E292V) produces a hypomorphic variant that accounts for a significant portion of ABCA3 mutations associated with lung disorders spanning from neonatal respiratory distress syndrome and childhood interstitial lung disease to diffuse parenchymal lung disease (DPLD) in adults including pulmonary fibrosis. The mechanisms by which this and similar ABCA3 mutations disrupt alveolar type 2 (AT2) cell homeostasis and cause DPLD are largely unclear. The present study, informed by a patient homozygous for the E292V variant, used an in vitro and a preclinical murine model to evaluate the mechanisms by which E292V expression promotes aberrant lung injury and parenchymal remodeling. Cell lines stably expressing enhanced green fluorescent protein (EGFP)-tagged ABCA3 isoforms show a functional deficiency of the ABCA3^E292V variant as a lipid transporter. AT2 cells isolated from mice constitutively homozygous for ABCA3^E292V demonstrate the presence of small electron-dense lamellar bodies, time-dependent alterations in macroautophagy, and induction of apoptosis. These changes in AT2 cell homeostasis are accompanied by a spontaneous lung phenotype consisting of both age-dependent inflammation and fibrillary collagen deposition in alveolar septa. Older ABCA3^E292V mice exhibit increased vulnerability to exogenous lung injury by bleomycin. Collectively, these findings support the hypothesis that the ABCA3^E292V variant is a susceptibility factor for lung injury through effects on surfactant deficiency and impaired AT2 cell autophagy.

Quantification of dual-energy CT-derived functional parameters as potential imaging markers for progression of idiopathic pulmonary fibrosis

OBJECTIVES

The individual course of disease in idiopathic pulmonary fibrosis (IPF) is highly variable. Assessment of disease activity and prospective estimation of disease progression might have the potential to improve therapy management and indicate the onset of treatment at an earlier stage. The aim of this study was to evaluate whether regional ventilation, lung perfusion, and late enhancement can serve as early imaging markers for disease progression in patients with IPF.

METHODS

In this retrospective study, contrast-enhanced dual-energy CT scans of 32 patients in inspiration and delayed expiration were performed at two time points with a mean interval of 15.4 months. The pulmonary blood volume (PBV) images obtained in the arterial and delayed perfusion phase served as a surrogate for arterial lung perfusion and parenchymal late enhancement. The virtual non-contrast (VNC) images in inspiration and expiration were non-linearly registered to provide regional ventilation images. Image-derived parameters were correlated with longitudinal changes of lung function (FVC%, DLCO%), mean lung density in CT, and CT-derived lung volume.

RESULTS

Regional ventilation and late enhancement at baseline preceded future change in lung volume (R - 0.474, p 0.006/R - 0.422, p 0.016, respectively) and mean lung density (R - 0.469, p 0.007/R - 0.402, p 0.022, respectively). Regional ventilation also correlated with a future change in FVC% (R - 0.398, p 0.024).

CONCLUSION

CT-derived functional parameters of regional ventilation and parenchymal late enhancement are potential early imaging markers for idiopathic pulmonary fibrosis progression.

KEY POINTS

• Functional CT parameters at baseline (regional ventilation and late enhancement) correlate with future structural changes of the lung as measured with loss of lung volume and increase in lung density in serial CT scans of patients with idiopathic pulmonary fibrosis. • Functional CT parameter measurements in high-attenuation areas (- 600 to - 250 HU) are significantly different from normal-attenuation areas (- 950 to - 600 HU) of the lung. • Mean regional ventilation in functional CT correlates with a future change in forced vital capacity (FVC) in pulmonary function tests.

Improved Alveolar Dynamics and Structure After Alveolar Epithelial Type II Cell Transplantation in Bleomycin Induced Lung Fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressively and ultimately fatal lung disease. Previously it has been shown that intratracheal administration of alveolar epithelial type II cells (AE2C) in the animal model of bleomycin-induced pulmonary fibrosis is able to reverse fibrosis and restore surfactant protein levels. However, to date, it has not been evaluated whether these changes involve any improvement in alveolar dynamics. Consequently, the aim of the present work was to study lung physiology after AE2C transplantation at different time points during the development of injury and fibrosis. Lung fibrosis was induced by intratracheal instillation of bleomycin (4U/kg) in rat lungs. The animals were transplanted with AE2C (2.5 × 10⁶ cells/animal) 3 or 7 days after bleomycin instillation. Assessments were done at day 7 and 14 after the induction of fibrosis to plot time dependent changes in lung physiology and mechanics. To assess the pressures and rates at which closed alveoli reopens invasive pulmonary tests using a small-animal mechanical ventilator (Flexivent®, Scireq, Canada) including de-recruitability tests and forced oscillation technique as well as quasi-static pressure volume loops were performed. Afterwards lungs were fixed by vascular perfusion and subjected to design-based stereological evaluation at light and electron microscopy level. AE2C delivered during the lung injury phase (3 days) of the disease are only able to slightly recover the volume of AE2C and volume fraction of LB in AE2C. However, it did not show either positive effects regarding ventilated alveolar surface nor any increase of lung compliance. On the other hand, when AE2C are delivered at the beginning of the fibrotic phase (7 days after bleomycin instillation), an increased ventilated alveolar surface to control levels and reduced septal wall thickness can be observed. Moreover, transplanted animals showed better lung performance, with increased inspiratory capacity and compliance. In addition, a detailed analysis of surfactant active forms [mainly tubular myelin, lamellar body (LB)-like structures and multilamellar vesicles (MLV)], showed an effective recovery during the pro-fibrotic phase due to the healthy AE2C transplantation. In conclusion, AE2C transplantation during fibrogenic phases of the disease improves lung performance, structure and surfactant ultrastructure in bleomycin-induced lung fibrosis.

Stereology as the 3D tool to quantitate lung architecture

Stereology is the method of choice for the quantitative assessment of biological objects in microscopy. It takes into account the fact that, in traditional microscopy such as conventional light and transmission electron microscopy, although one has to rely on measurements on nearly two-dimensional sections from fixed and embedded tissue samples, the quantitative data obtained by these measurements should characterize the real three-dimensional properties of the biological objects and not just their “flatland” appearance on the sections. Thus, three-dimensionality is a built-in property of stereological sampling and measurement tools. Stereology is, therefore, perfectly suited to be combined with 3D imaging techniques which cover a wide range of complementary sample sizes and resolutions, e.g. micro-computed tomography, confocal microscopy and volume electron microscopy. Here, we review those stereological principles that are of particular relevance for 3D imaging and provide an overview of applications of 3D imaging-based stereology to the lung in health and disease. The symbiosis of stereology and 3D imaging thus provides the unique opportunity for unbiased and comprehensive quantitative characterization of the three-dimensional architecture of the lung from macro to nano scale.

Hidden Microatelectases Increase Vulnerability to Ventilation-Induced Lung Injury

Mechanical ventilation of lungs suffering from microatelectases may trigger the development of acute lung injury (ALI). Direct lung injury by bleomycin results in surfactant dysfunction and microatelectases at day 1 while tissue elastance and oxygenation remain normal. Computational simulations of alveolar micromechanics 1-day post-bleomycin predict persisting microatelectases throughout the respiratory cycle and increased alveolar strain during low positive end-expiratory pressure (PEEP) ventilation. As such, we hypothesize that mechanical ventilation in presence of microatelectases, which occur at low but not at higher PEEP, aggravates and unmasks ALI in the bleomycin injury model. Rats were randomized and challenged with bleomycin (B) or not (H = healthy). One day after bleomycin instillation the animals were ventilated for 3 h with PEEP 1 (PEEP1) or 5 cmH₂O (PEEP5) and a tidal volume of 10 ml/kg bodyweight. Tissue elastance was repetitively measured after a recruitment maneuver to investigate the degree of distal airspace instability. The right lung was subjected to bronchoalveolar lavage (BAL), the left lung was fixed for design-based stereology at light- and electron microscopic level. Prior to mechanical ventilation, lung tissue elastance did not differ. During mechanical ventilation tissue elastance increased in bleomycin-injured lungs ventilated with PEEP = 1 cmH₂O but remained stable in all other groups. Measurements at the conclusion of ventilation showed the largest time-dependent increase in tissue elastance after recruitment in B/PEEP1, indicating increased instability of distal airspaces. These lung mechanical findings correlated with BAL measurements including elevated BAL neutrophilic granulocytes as well as BAL protein and albumin in B/PEEP1. Moreover, the increased septal wall thickness and volume of peri-bronchiolar-vascular connective tissue in B/PEEP1 suggested aggravation of interstitial edema by ventilation in presence of microatelectases. At the electron microscopic level, the largest surface area of injured alveolar epithelial was observed in bleomycin-challenged lungs after PEEP = 1 cmH₂O ventilation. After bleomycin treatment cellular markers of endoplasmic reticulum stress (p-Perk and p-EIF-2α) were positive within the septal wall and ventilation with PEEP = 1 cmH₂O ventilation increased the surface area stained positively for p-EIF-2α. In conclusion, hidden microatelectases are linked with an increased pulmonary vulnerability for mechanical ventilation characterized by an aggravation of epithelial injury.

Air Space Distension Precedes Spontaneous Fibrotic Remodeling and Impaired Cholesterol Metabolism in the Absence of Surfactant Protein C

Surfactant protein (SP)-C deficiency is found in samples from patients with idiopathic pulmonary fibrosis, especially in familial forms of this disease. We hypothesized that SP-C may contribute to fibrotic remodeling in aging mice and alveolar lipid homeostasis. For this purpose, we analyzed lung function, alveolar dynamics, lung structure, collagen content, and expression of genes related to lipid and cholesterol metabolism of aging SP-C knockout mice. In addition, in vitro experiments with an alveolar macrophage cell line exposed to lipid vesicles with or without cholesterol and/or SP-C were performed. Alveolar dynamics showed progressive alveolar derecruitment with age and impaired oxygen saturation. Lung structure revealed that decreasing volume density of alveolar spaces was accompanied by increasing of the ductal counterparts. Simultaneously, septal wall thickness steadily increased, and fibrotic wounds appeared in lungs from the age of 50 weeks. This remarkable phenotype is unique to the 129Sv strain, which has an increased absorption of cholesterol, linking the accumulation of cholesterol and the absence of SP-C to a fibrotic remodeling process. The findings of this study suggest that overall loss of SP-C results in an age-dependent, complex, heterogeneous phenotype characterized by a combination of overdistended air spaces and fibrotic wounds that resembles combined emphysema and pulmonary fibrosis in patients with idiopathic pulmonary fibrosis. Addition of SP-C to cholesterol-laden lipid vesicles enhanced the expression of cholesterol metabolism and transport genes in an alveolar macrophage cell line, identifying a potential new lipid-protein axis involved in lung remodeling.

Transcriptomic profiling reveals disease-specific characteristics of epithelial cells in idiopathic pulmonary fibrosis

Background

Idiopathic pulmonary fibrosis (IPF) is an incurable disease characterized by progressive lung fibrosis ultimately resulting in respiratory failure and death. Recurrent micro-injuries to the alveolar epithelium and aberrant alveolar wound healing with impaired re-epithelialization define the initial steps of the pathogenic trajectory. Failure of timely alveolar epithelial repair triggers hyper-proliferation of mesenchymal cells accompanied by increased deposition of extracellular matrix into the lung interstitium.

Methods

We previously isolated fibrosis-specific mesenchymal stem cell (MSC)-like cells from lung tissue of patients with interstitial lung diseases. These cells produced factors bearing anti-fibrotic potential and changed their morphology from mesenchymal to epithelial upon culture in an epithelial cell (EC)-specific growth medium. Here, we set out to molecularly characterize these MSC-like cell-derived ECs using global gene expression profiling by RNA-sequencing. Moreover, we aimed at characterizing disease-specific differences by comparing the transcriptomes of ECs from IPF and non-IPF sources.

Results

Our results suggest that differentially expressed genes are enriched for factors related to fibrosis, hypoxia, bacterial colonization and metabolism, thus reflecting many of the hallmark characteristics of pulmonary fibrosis. IPF-ECs showed enrichment of both pro- and anti-fibrotic genes, consistent with the notion of adaptive, compensatory regulation.

Conclusions

Our findings support the hypothesis of a functional impairment of IPF-ECs, which could possibly explain the poor clinical outcome of IPF that roughly compares to those of advanced-stage cancers. Our study provides a valuable resource for downstream mechanistic investigation and the quest for novel therapeutic IPF targets.

Three Alveolar Phenotypes Govern Lung Function in Murine Ventilator-Induced Lung Injury

Mechanical ventilation is an essential lifesaving therapy in acute respiratory distress syndrome (ARDS) that may cause ventilator-induced lung injury (VILI) through a positive feedback between altered alveolar mechanics, edema, surfactant inactivation, and injury. Although the biophysical forces that cause VILI are well documented, a knowledge gap remains in the quantitative link between altered parenchymal structure (namely alveolar derecruitment and flooding), pulmonary function, and VILI. This information is essential to developing diagnostic criteria and ventilation strategies to reduce VILI and improve ARDS survival. To address this unmet need, we mechanically ventilated mice to cause VILI. Lung structure was measured at three air inflation pressures using design-based stereology, and the mechanical function of the pulmonary system was measured with the forced oscillation technique. Assessment of the pulmonary surfactant included total surfactant, distribution of phospholipid aggregates, and surface tension lowering activity. VILI-induced changes in the surfactant included reduced surface tension lowering activity in the typically functional fraction of large phospholipid aggregates and a significant increase in the pool of surface-inactive small phospholipid aggregates. The dominant alterations in lung structure at low airway pressures were alveolar collapse and flooding. At higher airway pressures, alveolar collapse was mitigated and the flooded alveoli remained filled with proteinaceous edema. The loss of ventilated alveoli resulted in decreased alveolar gas volume and gas-exchange surface area. These data characterize three alveolar phenotypes in murine VILI: flooded and non-recruitable alveoli, unstable alveoli that derecruit at airway pressures below 5 cmH2O, and alveoli with relatively normal structure and function. The fraction of alveoli with each phenotype is reflected in the proportional changes in pulmonary system elastance at positive end expiratory pressures of 0, 3, and 6 cmH2O.

Azithromycin has enhanced effects on lung fibroblasts from idiopathic pulmonary fibrosis (IPF) patients compared to controls [corrected]

BACKGROUND

Idiopathic pulmonary fibrosis (IPF) is a chronic fatal lung disease without a cure and new drug strategies are urgently needed. Differences in behavior between diseased and healthy cells are well known and drug response can be different between cells isolated from IPF patients and controls. The macrolide Azithromycin (AZT) has anti-inflammatory and immunomodulatory properties. Recently anti-fibrotic effects have been described. However, the anti-fibrotic effects on primary IPF-fibroblasts (FB) directly compared to control-FB are unknown. We hypothesized that IPF-FB react differently to AZT in terms of anti-fibrotic effects.

METHODS

Primary normal human lung and IPF-FB were exposed to TGF-β (5 ng/ml), Azithromycin (50 μM) alone or in combination prior to gene expression analysis. Pro-collagen Iα1 secretion was assessed by ELISA and protein expression by western blot (αSMA, Fibronectin, ATP6V1B2, LC3 AB (II/I), p62, Bcl-xL). Microarray analysis was performed to screen involved genes and pathways after Azithromycin treatment in control-FB. Apoptosis and intraluminal lysosomal pH were analyzed by flow cytometry.

RESULTS

AZT significantly reduced collagen secretion in TGF-β treated IPF-FB compared to TGF-β treatment alone, but not in control-FB. Pro-fibrotic gene expression was similarly reduced after AZT treatment in IPF and control-FB. P62 and LC3II/I western blot revealed impaired autophagic flux after AZT in both control and IPF-FB with significant increase of LC3II/I after AZT in control and IPF-FB, indicating enhanced autophagy inhibition. Early apoptosis was significantly higher in TGF-β treated IPF-FB compared to controls after AZT. Microarray analysis of control-FB treated with AZT revealed impaired lysosomal pathways. The ATPase and lysosomal pH regulator ATP6V0D2 was significantly less increased after additional AZT in IPF-FB compared to controls. Lysosomal function was impaired in both IPF and control FB, but pH was significantly more increased in TGF-β treated IPF-FB.

CONCLUSION

We report different treatment responses after AZT with enhanced anti-fibrotic and pro-apoptotic effects in IPF compared to control-FB. Possibly impaired lysosomal function contributes towards these effects. In summary, different baseline cell phenotype and behavior of IPF and control cells contribute to enhanced anti-fibrotic and pro-apoptotic effects in IPF-FB after AZT treatment and strengthen its role as a new potential anti-fibrotic compound, that should further be evaluated in clinical studies.

Volume-CLEM: a method for correlative light and electron microscopy in three dimensions

Generation of three-dimensional (3D) data sets from serial sections of tissues imaged by light microscopy (LM) allows identification of rare structures by morphology or fluorescent labeling. Here, we demonstrate a workflow for correlative LM and electron microscopy (EM) from 3D LM to 3D EM, using the same sectioned material for both methods consecutively. The new approach is easy to reproduce in routine EM laboratories and applicable to a wide range of organs and research questions.

Characteristics of patients treated by the Danish Helicopter Emergency Medical Service from 2014-2018: a nationwide population-based study

Background

A national Helicopter Emergency Medical Service (HEMS) was introduced in Denmark in 2014 to ensure the availability of physician-led critical care for all patients regardless of location.

Appropriate dispatch of HEMS is known to be complex, and resource utilisation is a highly relevant topic. Population-based studies on patient characteristics are fundamental when evaluating and optimising a system. The aim of this study was to describe the patient population treated by the Danish HEMS in terms of demographics, pre-hospital diagnostics, severity of illness or injury, and the critical care interventions performed.

Method

The study is a retrospective nationwide population-based study based on data gathered from the Danish HEMS database. We included primary missions resulting in a patient encounter registered between October 1^st 2014 and April 30^th 2018.

Results

Of 13.391 dispatches registered in the study period we included 7133 (53%) primary missions with patient encounter: 4639 patients were air lifted to hospital, 174 patients were escorted to hospital by the HEMS physician in an ambulance, and in 2320 cases HEMS assisted the ground crew on scene but did not escort the patient to hospital. Patient age ranged from 0-99 years and 64% of the population were men. The median age was 60 years.

The main diagnostic groups were cardio-vascular emergencies (41%), trauma (23%) and neurological emergencies (16%). In 61% of the cases, the patient was critically ill/injured corresponding to a NACA (National Advisory Committee for Aeronautics) score between 4 and 7 (both included). In more than one third of the missions a critical care intervention was performed. Ultrasound examination and endo-tracheal intubation were the critical care interventions most frequently performed (21% and 20%, respectively).

Conclusion

The national Danish HEMS primarily attends severely ill or injured patients and often perform critical care interventions. In addition, the Danish HEMS provides rapid transport to highly specialised treatment for patients in the more rural parts of the country.

Patients with cardio-vascular emergencies, trauma and neurological emergencies are among those patient groups most commonly seen.

We conclude that the overall dispatch profile appears appropriate but emphasise that continuous development and refinement is essential.

Surfactant Protein B Deficiency Induced High Surface Tension: Relationship between Alveolar Micromechanics, Alveolar Fluid Properties and Alveolar Epithelial Cell Injury

High surface tension at the alveolar air-liquid interface is a typical feature of acute and chronic lung injury. However, the manner in which high surface tension contributes to lung injury is not well understood. This study investigated the relationship between abnormal alveolar micromechanics, alveolar epithelial injury, intra-alveolar fluid properties and remodeling in the conditional surfactant protein B (SP-B) knockout mouse model. Measurements of pulmonary mechanics, broncho-alveolar lavage fluid (BAL), and design-based stereology were performed as a function of time of SP-B deficiency. After one day of SP-B deficiency the volume of alveolar fluid V(alvfluid,par) as well as BAL protein and albumin levels were normal while the surface area of injured alveolar epithelium S(AEinjure,sep) was significantly increased. Alveoli and alveolar surface area could be recruited by increasing the air inflation pressure. Quasi-static pressure-volume loops were characterized by an increased hysteresis while the inspiratory capacity was reduced. After 3 days, an increase in V(alvfluid,par) as well as BAL protein and albumin levels were linked with a failure of both alveolar recruitment and airway pressure-dependent redistribution of alveolar fluid. Over time, V(alvfluid,par) increased exponentially with S(AEinjure,sep). In conclusion, high surface tension induces alveolar epithelial injury prior to edema formation. After passing a threshold, epithelial injury results in vascular leakage and exponential accumulation of alveolar fluid critically hampering alveolar recruitability.

Susceptibility of microtubuleassociated protein 1 light chain 3β (MAP1LC3B/LC3B) knockout mice to lung injury and fibrosis

Insufficient autophagy has been reported in idiopathic pulmonary fibrosis (IPF) lungs. Specific roles of autophagy-related proteins in lung fibrosis development remain largely unknown. Here, we investigated the role of autophagy marker protein microtubule-associated protein 1 light chain 3β (LC3B) in the development of lung fibrosis. LC3B^-/- mice upon aging show smaller lamellar body profiles, increased cellularity, alveolar epithelial cell type II (AECII) apoptosis, surfactant alterations, and lysosomal and endoplasmic reticulum stress. Autophagosomal soluble N-ethylmaleimide-sensitive factor attachment protein receptor syntaxin 17 is increased in the AECII of aged LC3B^-/- mice and patients with IPF. Proteasomal activity, however, remained unaltered in LC3B^-/- mice. In vitro knockdown of LC3B sensitized mouse lung epithelial cells to bleomycin-induced apoptosis, but its overexpression was protective. In vivo, LC3B^-/- mice displayed increased susceptibility to bleomycin-induced lung injury and fibrosis. We identified cathepsin A as a novel LC3B binding partner and its overexpression in vitro drives MLE12 cells to apoptosis. Additionally, cathepsin A is increased in the AECII of aged LC3B^-/- mice and in the lungs of patients with IPF. Our study reveals that LC3B mediated autophagy plays essential roles in AECII by modulating the functions of proteins like cathepsin A and protects alveolar epithelial cells from apoptosis and subsequent lung injury and fibrosis.-Kesireddy, V. S., Chillappagari, S., Ahuja, S., Knudsen, L., Henneke, I., Graumann, J., Meiners, S., Ochs, M., Ruppert, C., Korfei, M., Seeger, W., Mahavadi, P. Susceptibility of microtubule-associated protein 1 light chain 3β (MAP1LC3B/LC3B) knockout mice to lung injury and fibrosis.

Effective hematopoietic stem cell-based gene therapy in a murine model of hereditary pulmonary alveolar proteinosis

Hereditary pulmonary alveolar proteinosis due to GM-CSF receptor deficiency (herPAP) constitutes a life-threatening lung disease characterized by alveolar deposition of surfactant protein secondary to defective alveolar macrophage function. As current therapeutic options are primarily symptomatic, we have explored the potential of hematopoietic stem cell-based gene therapy. Using Csf2rb^-/- mice, a model closely reflecting the human herPAP disease phenotype, we here demonstrate robust pulmonary engraftment of an alveolar macrophage population following intravenous transplantation of lentivirally corrected hematopoietic stem and progenitor cells. Engraftment was associated with marked improvement of critical herPAP disease parameters, including bronchoalveolar fluid protein, cholesterol and cytokine levels, pulmonary density on computed tomography scans, pulmonary deposition of Periodic Acid-Schiff⁺ material as well as respiratory mechanics. These effects were stable for at least nine months. With respect to engraftment and alveolar macrophage differentiation kinetics, we demonstrate the rapid development of CD11c⁺/SiglecF⁺ cells in the lungs from a CD11c^-/SiglecF⁺ progenitor population within four weeks after transplantation. Based on these data, we suggest hematopoietic stem cell-based gene therapy as an effective and cause-directed treatment approach for herPAP.

The FMS-like tyrosine kinase-3 ligand/lung dendritic cell axis contributes to regulation of pulmonary fibrosis

RATIONALE

Dendritic cells (DC) accumulate in the lungs of patients with idiopathic lung fibrosis, but their pathogenetic relevance is poorly defined.

OBJECTIVES

To assess the role of the FMS-like tyrosine kinase-3 ligand (Flt3L)-lung dendritic cell axis in lung fibrosis.

MEASUREMENTS AND MAIN RESULTS

We demonstrate in a model of adenoviral gene transfer of active TGF-β1 that established lung fibrosis was accompanied by elevated serum Flt3L levels and subsequent accumulation of CD11b^pos DC in the lungs of mice. Patients with idiopathic pulmonary fibrosis also demonstrated increased levels of Flt3L protein in serum and lung tissue and accumulation of lung DC in explant subpleural lung tissue specimen. Mice lacking Flt3L showed significantly reduced lung DC along with worsened lung fibrosis and reduced lung function relative to wild-type (WT) mice, which could be inhibited by administration of recombinant Flt3L. Moreover, therapeutic Flt3L increased numbers of CD11b^pos DC and improved lung fibrosis in WT mice exposed to AdTGF-β1. In this line, RNA-sequencing analysis of CD11b^pos DC revealed significantly enriched differentially expressed genes within extracellular matrix degrading enzyme and matrix metalloprotease gene clusters. In contrast, the CD103^pos DC subset did not appear to be involved in pulmonary fibrogenesis.

CONCLUSIONS

We show that Flt3L protein and numbers of lung DC are upregulated in mice and humans during pulmonary fibrogenesis, and increased mobilisation of lung CD11b^pos DC limits the severity of lung fibrosis in mice. The current study helps to inform the development of DC-based immunotherapy as a novel intervention against lung fibrosis in humans.

Flow cytometric analysis of the leukocyte landscape during bleomycin-induced lung injury and fibrosis in the rat

Bleomycin-induced lung injury and fibrosis is a well-described model to investigate lung inflammatory and remodeling mechanisms. Rat models are clinically relevant and are also widely used, but rat bronchoalveolar lavage (BAL) cells are not fully characterized with flow cytometry due to the limited availability of antibodies for this species. We optimized a comprehensive time-dependent flow cytometric analysis of cells after bleomycin challenge, confirming previous studies in other species and correlating them to histological staining, cytokine profiling, and collagen accumulation analysis in rat lungs. For this purpose, we describe a novel panel of rat surface markers and a strategy to identify and follow BAL cells over time. By combining surface markers in rat alveolar cells (CD45⁺), granulocytes and other myeloid cells, monocytes and macrophages can be identified by the expression of CD11b/c. Moreover, different activation states of macrophages (CD163⁺) can be observed: steady state (CD86^-MHC-II^low), activation during inflammation (CD86⁺,MHC-II^high), activation during remodeling (CD86⁺MHC-II^low), and a population of newly recruited monocytes (CD163^-α-granulocyte^-). Hydroxyproline measured as marker of collagen content in lung tissue showed positive correlation with the reparative phase (CD163^- cells and tissue inhibitor of metalloproteinases (TIMP) and IL-10 increase). In conclusion, after a very early granulocytic recruitment, inflammation in rat lungs is observed by activated macrophages, and high release of IL-6 and fibrotic remodeling is characterized by recovery of the macrophage population together with TIMP, IL-10, and IL-18 production. Recruited monocytes and a second peak of granulocytes appear in the transitioning phase, correlating with immunostaining of arginase-1 in the tissue, revealing the importance of events leading the changes from injury to aberrant repair.

The Danish helicopter emergency medical service database: high quality data with great potential

Background

The Danish Helicopter Emergency Medical Service (HEMS) is part of the Danish pre-hospital response offering advanced patient care on scene and during rapid transport to definitive care.

Monitoring HEMS performance and the quality of critical care has high national as well as international priority underlining the need for research in this field.

The data quality of the Danish HEMS database is unknown. Furthermore, a set of quality indicators (QI) developed by an international collaboration group (EQUIPE) potentially for use in physician-staffed EMS, has recently been presented.

The aim of the current study was to present the design and data quality of the Danish helicopter database, and to evaluate the coverage of available variables in the database according to the QIs proposed.

Method

The study included all helicopter dispatches between October 1st 2014 and April 30th 2018.

The database layout and data entering procedure, as well as the key variables and data completeness were described. Furthermore, missing data and misclassifications were addressed.

Lastly, the 26 QIs proposed by the EQUIPE-collaboration were evaluated for coverage in the HEMS database.

Results

A total of 13,392 missions were included in the study. The database includes a broad spectrum of mission- and patient-specific data related to the pre-hospital pathway of acutely ill or injured patients in a national coverage. Missing data for the majority of variables is less than 6.5%. The percentage of completed report forms has increased over time and reached 99.9% in 2018.

Misclassification were observed for 294 patients in the study period corresponding to 3,7%.

Less than half of the QIs proposed by the EQUIPE-collaboration group were directly available from the database.

Conclusions

Helicopter Emergency Medical Services in Denmark are a new and sparsely investigated health care provider. The database contains nearly all missions dispatched by the five regional Emergency Medical Dispatch Centres. Generally, the data quality is considered high with great potential for future research.

Potential quality indicators as proposed by the EQUIPE-collaboration group could inspire the configuration and design of the next version of Hemsfile creating an even more solid basis for research and quality improvement.

Electronic supplementary material

The online version of this article (10.1186/s13049-019-0615-5) contains supplementary material, which is available to authorized users.

Alveolar Micromechanics in Bleomycin-induced Lung Injury

Lung injury results in intratidal alveolar recruitment and derecruitment and alveolar collapse, creating stress concentrators that increase strain and aggravate injury. In this work, we sought to describe alveolar micromechanics during mechanical ventilation in bleomycin-induced lung injury and surfactant replacement therapy. Structure and function were assessed in rats 1 day and 3 days after intratracheal bleomycin instillation and after surfactant replacement therapy. Pulmonary system mechanics were measured during ventilation with positive end-expiratory pressures (PEEPs) between 1 and 10 cm H2O, followed by perfusion fixation at end-expiratory pressure at airway opening (Pao) values of 1, 5, 10, and 20 cm H2O for quantitative analyses of lung structure. Lung structure and function were used to parameterize a physiologically based, multicompartment computational model of alveolar micromechanics. In healthy controls, the numbers of open alveoli remained stable in a range of Pao = 1-20 cm H2O, whereas bleomycin-challenged lungs demonstrated progressive alveolar derecruitment with Pao < 10 cm H2O. At Day 3, ∼40% of the alveoli remained closed at high Pao, and alveolar size heterogeneity increased. Simulations of injured lungs predicted that alveolar recruitment pressures were much greater than the derecruitment pressures, so that minimal intratidal recruitment and derecruitment occurred during mechanical ventilation with a tidal volume of 10 ml/kg body weight over a range of PEEPs. However, the simulations also predicted a dramatic increase in alveolar strain with injury that we attribute to alveolar interdependence. These findings suggest that in progressive lung injury, alveolar collapse with increased distension of patent (open) alveoli dominates alveolar micromechanics. PEEP and surfactant substitution reduce alveolar collapse and dynamic strain but increase static strain.

Generation of an alveolar epithelial type II cell line from induced pluripotent stem cells

Differentiation of primary alveolar type II epithelial cells (AEC II) to AEC type I in culture is a major barrier in the study of the alveolar epithelium in vitro. The establishment of an AEC II cell line derived from induced pluripotent stem cells (iPSC) represents a novel opportunity to study alveolar epithelial cell biology, for instance, in the context of lung injury, fibrosis, and repair. In the present study, we generated long-lasting AEC II from iPSC (LL-iPSC-AEC II). LL-iPSC-AEC II displayed morphological characteristics of AEC II, including growth in a cobblestone monolayer, the presence of lamellar bodies, and microvilli, as shown by electron microscopy. Also, LL-iPSC-AEC II expressed AEC type II proteins, such as cytokeratin, surfactant protein C, and LysoTracker DND 26 (a marker for lamellar bodies). Furthermore, the LL-iPSC-AEC II exhibited functional properties of AEC II by an increase of transepithelial electrical resistance over time, secretion of inflammatory mediators in biologically relevant quantities (IL-6 and IL-8), and efficient in vitro alveolar epithelial wound repair. Consistent with the AEC II phenotype, the cell line showed the ability to uptake and release surfactant protein B, to secrete phospholipids, and to differentiate into AEC type I. In summary, we established a long-lasting, but finite AEC type II cell line derived from iPSC as a novel cellular model to study alveolar epithelial cell biology in lung health and disease.

The micromechanics of lung alveoli: structure and function of surfactant and tissue components

The mammalian lung´s structural design is optimized to serve its main function: gas exchange. It takes place in the alveolar region (parenchyma) where air and blood are brought in close proximity over a large surface. Air reaches the alveolar lumen via a conducting airway tree. Blood flows in a capillary network embedded in inter-alveolar septa. The barrier between air and blood consists of a continuous alveolar epithelium (a mosaic of type I and type II alveolar epithelial cells), a continuous capillary endothelium and the connective tissue layer in-between. By virtue of its respiratory movements, the lung has to withstand mechanical challenges throughout life. Alveoli must be protected from over-distension as well as from collapse by inherent stabilizing factors. The mechanical stability of the parenchyma is ensured by two components: a connective tissue fiber network and the surfactant system. The connective tissue fibers form a continuous tensegrity (tension + integrity) backbone consisting of axial, peripheral and septal fibers. Surfactant (surface active agent) is the secretory product of type II alveolar epithelial cells and covers the alveolar epithelium as a biophysically active thin and continuous film. Here, we briefly review the structural components relevant for gas exchange. Then we describe our current understanding of how these components function under normal conditions and how lung injury results in dysfunction of alveolar micromechanics finally leading to lung fibrosis.

Hands-on or no hands-on training in ultrasound imaging: A randomized trial to evaluate learning outcomes and speed of recall of topographic anatomy

Medical students have difficulties in interpreting two-dimensional (2D) topographic anatomy on sectional images. Hands-on and no hands-on training in ultrasound imaging facilitate learning topographic anatomy. Hands-on training is linked with active search for patterns of anatomical structures and might train pattern recognition for image interpretation better although the added value on learning outcomes is unclear. This study explores first year medical students' knowledge in topographic anatomy of the upper abdomen after attending hands-on or no hands-on training in ultrasound in a randomized trial. While students in the hands-on ultrasound group (N = 21) generated and interpreted standardized planes of ultrasound imaging, students in the no hands-on seminar group (N = 22) interpreted provided ultrasound images by correlation to three-dimensional (3D) anatomical prosections. Afterwards knowledge in topographic anatomy was measured repetitively by text and ultrasound image-based multiple choice (MC) examinations. As surrogate for pattern recognition, students rated whether answers were known after reflection or instantly. While intrinsic motivation was higher in the ultrasound group, no differences in the MC-examination score were found between ultrasound and seminar group instantly (66.5 ±10.9% vs. 64.5% ±11.0%, P = 0.551) or six weeks (62.9% ±12.3% vs. 61.5% ±11.0%, P = 0.718) after training. In both groups scores in text-based questions declined (P < 0.001) while scores in image-based questions remained stable (P = 0.895) with time. After six weeks more image-based questions were instantly known in the hands-on ultrasound compared to seminar-group (28% ±17.3% vs. 16% ±13.5%, P = 0.047). Hands-on ultrasound-training is linked with faster interpreting of ultrasound images without loss in accuracy. The added value of hands-on training might be facilitation of pattern recognition.

Prehospital treatment of patients with acute intracranial pathology: adherence to guidelines and blood pressure recommendations by the Danish Air Ambulance

Background

Hypoxia and hypotension may be associated with secondary brain injury and negative outcomes in patients with traumatic and non-traumatic intracranial pathology. Guidelines exist only for the prehospital management of patients with severe traumatic brain injury (TBI). In patients with non-traumatic intracranial pathology, TBI guideline recommendations may be applied to assess whether hypoxia and hypotension should be avoided during prehospital treatment. The main study objective was to assess the extent to which Danish Helicopter Emergency Medical Service (HEMS) critical care teams adhere to the prehospital TBI guideline recommendations for the management of patients with a clinical diagnosis of non-traumatic intracranial pathology or isolated TBI. Furthermore, in the same two groups of patients, we evaluated the adherence of the Danish HEMS critical care teams to recommendations aiming to maintain systolic blood pressure (SBP) > 110 mmHg and > 120 mmHg.

Methods

In total, 211 prehospital patient records were studied. All patients were treated for non-traumatic intracranial pathology or isolated TBI by the Danish HEMS critical care teams from October 1, 2014, to January 1, 2017. Adherence to the prehospital TBI guideline recommendations and the SBP recommendations above was assessed in non-TBI and TBI populations.

Results

The adherence rates to TBI guideline recommendations among Danish HEMS critical care teams were 69% (n = 106 [95% CI: 61–77%]) in the non-TBI population and 74% (n = 43 [95% CI: 61–85%]) in the TBI population. SBP > 110 mmHg was observed in 74% (n = 113 [95% CI: 66–81%]) and 69% (n = 40 [95% CI: 56–81%]) of cases in the non-TBI and TBI population, respectively. SBP > 120 mmHg was observed in 55% (n = 84, [95% CI: 47–63%]) of patients in the non-TBI population and 55% (n = 32 [95% CI: 42–68%]) of the patients in the TBI population.

Conclusions

Due to a lack of comparative data, it is difficult to determine the performance quality of the Danish HEMS critical care teams. Our findings may suggest that adherence to TBI guidelines and SBP recommendations needs to be a continuous focal point for the Danish HEMS to avoid secondary brain damage.

iPSC-Derived Macrophages Effectively Treat Pulmonary Alveolar Proteinosis in Csf2rb-Deficient Mice

Induced pluripotent stem cell (iPSC)-derived hematopoietic cells represent a highly attractive source for cell and gene therapy. Given the longevity, plasticity, and self-renewal potential of distinct macrophage subpopulations, iPSC-derived macrophages (iPSC-Mφ) appear of particular interest in this context. We here evaluated the airway residence, plasticity, and therapeutic efficacy of iPSC-Mφ in a murine model of hereditary pulmonary alveolar proteinosis (herPAP). We demonstrate that single pulmonary macrophage transplantation (PMT) of 2.5–4 × 10⁶ iPSC-Mφ yields efficient airway residence with conversion of iPSC-Mφ to an alveolar macrophage (AMφ) phenotype characterized by a distinct surface marker and gene expression profile within 2 months. Moreover, PMT significantly improves alveolar protein deposition and other critical herPAP disease parameters. Thus, our data indicate iPSC-Mφ as a source of functional macrophages displaying substantial plasticity and therapeutic potential that upon pulmonary transplantation will integrate into the lung microenvironment, adopt an AMφ phenotype and gene expression pattern, and profoundly ameliorate pulmonary disease phenotypes.

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iPSCs as a source of functional macrophages with substantial plasticity

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iPSC-derived macrophages have therapeutic potential in hereditary PAP

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Pulmonary-transplanted iPSC-Mφ integrate into the lung microenvironment

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iPSC-Mφ can adopt an AMφ phenotype and gene expression pattern