Lipid A in outer membrane vesicles shields bacteria from polymyxins.

The continuous emergence of multidrug-resistant bacterial pathogens poses a major global healthcare challenge, with Klebsiella pneumoniae being a prominent threat. We conducted a comprehensive study on K. pneumoniae's antibiotic resistance mechanisms, focusing on outer membrane vesicles (OMVs) and polymyxin, a last-resort antibiotic. Our research demonstrates that OMVs protect bacteria from polymyxins. OMVs derived from Polymyxin B (PB)-stressed K. pneumoniae exhibited heightened protective efficacy due to increased vesiculation, compared to OMVs from unstressed Klebsiella. OMVs also shield bacteria from different bacterial families. This was validated ex vivo and in vivo using precision cut lung slices (PCLS) and Galleria mellonella. In all models, OMVs protected K. pneumoniae from PB and reduced the associated stress response on protein level. We observed significant changes in the lipid composition of OMVs upon PB treatment, affecting their binding capacity to PB. The altered binding capacity of single OMVs from PB stressed K. pneumoniae could be linked to a reduction in the lipid A amount of their released vesicles. Although the amount of lipid A per vesicle is reduced, the overall increase in the number of vesicles results in an increased protection because the sum of lipid A and therefore PB binding sites have increased. This unravels the mechanism of the altered PB protective efficacy of OMVs from PB stressed K. pneumoniae compared to control OMVs. The lipid A-dependent protective effect against PB was confirmed in vitro using artificial vesicles. Moreover, artificial vesicles successfully protected Klebsiella from PB ex vivo and in vivo. The findings indicate that OMVs act as protective shields for bacteria by binding to polymyxins, effectively serving as decoys and preventing antibiotic interaction with the cell surface. Our findings provide valuable insights into the mechanisms underlying antibiotic cross-protection and offer potential avenues for the development of novel therapeutic interventions to address the escalating threat of multidrug-resistant bacterial infections.

Comparison of adhesion prevention capabilities of the modified starch powder-based medical devices 4DryField® PH, HaemoCer™ PLUS and StarSil® in the Optimized Peritoneal Adhesion Model.

Background and Objectives: The rat Optimized Peritoneal Adhesion Model (OPAM) was developed to provoke adhesion formation with high reproducibility in incidence and extent. In a recent study, the starch-based hemostats 4DryField PH and Arista AH were tested for their capabilities to prevent adhesion formation, the former one certified for adhesion prevention and hemostasis, the latter one only certified for hemostasis. As two further starch-based hemostats, i.e., HaemoCer PLUS and StarSil, have officially been certified for adhesion prevention in the meantime, the present study was conducted to examine their efficacy. Materials and Methods: For this purpose, all three products were applied as a powder that was mixed in situ with saline solution to form a barrier gel. Adhesions were scored using the established macroscopically scoring systems by Lauder and Hoffmann, as well as histopathologically using the score by Zühlke. Animals receiving saline solution solely served as controls. Results: As previously published, 4DryField PH reduced peritoneal adhesions significantly. In contrast, HaemoCer PLUS and StarSil did not lead to a statistically significant reduction of adhesion formation. When comparing 4DryField PH, HaemoCer PLUS and StarSil, 4DryField PH was significantly more effective in preventing peritoneal adhesions. The results of the macroscopic investigation were confirmed by histopathological evaluations. Conclusions: Only 4DryField PH but neither HaemoCer PLUS nor StarSil were capable to effectively prevent adhesion formation, corroborating the assumption that starch-based hemostats do not generally have the capability to act as effective adhesion prevention devices.

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.

Ectopic expression of C-type lectin Mincle renders mice susceptible to staphylococcal pneumonia.

Staphylococcus aureus is a prevalent pathogen in pneumonia and harbors glycolipids which may serve as molecular patterns in Mincle (Macrophage inducible C-type lectin) dependent pathogen recognition. We examined the role of Mincle in lung defense against S. aureus in WT, Mincle KO and Mincle transgenic (tg) mice. Two glycolipids, glucosyl-diacylglycerol (Glc-DAG) and diglucosyl-diacylglycerol (Glc2-DAG) were purified, of which only Glc-DAG triggered Mincle reporter cell activation and professional phagocyte responses. Proteomic profiling revealed that Glc2-DAG blocked Glc-DAG-induced cytokine responses, thereby acting as inhibitor of Glc-DAG/Mincle-signaling. WT mice responded to S. aureus with a similar lung pathology as Mincle KO mice, most likely due to Glc2-DAG-dependent inhibition of Glc-DAG/Mincle-signaling. In contrast, ectopic Mincle expression caused severe lung pathology in S. aureus-infected mice characterized by bacterial outgrowth and fatal pneumonia. Collectively, Glc2-DAG inhibits Glc-DAG/Mincle-dependent responses in WT mice, whereas sustained Mincle expression overrides Glc2-DAG-mediated inhibitory effects, conferring increased host susceptibility to S. aureus.

Pulmonary hypertension associated with lung disease: new insights into pathomechanisms, diagnosis, and management.

Patients with chronic lung diseases, particularly interstitial lung disease and chronic obstructive pulmonary disease, frequently develop pulmonary hypertension, which results in clinical deterioration, worsening of oxygen uptake, and an increased mortality risk. Pulmonary hypertension can develop and progress independently from the underlying lung disease. The pulmonary vasculopathy is distinct from that of other forms of pulmonary hypertension, with vascular ablation due to loss of small pulmonary vessels being a key feature. Long-term tobacco exposure might contribute to this type of pulmonary vascular remodelling. The distinct pathomechanisms together with the underlying lung disease might explain why treatment options for this condition remain scarce. Most drugs approved for pulmonary arterial hypertension have shown no or sometimes harmful effects in pulmonary hypertension associated with lung disease. An exception is inhaled treprostinil, which improves exercise capacity in patients with interstitial lung disease and pulmonary hypertension. There is a pressing need for safe, effective treatment options and for reliable, non-invasive diagnostic tools to detect and characterise pulmonary hypertension in patients with chronic lung disease.

CAR-NK Cells Targeting HER1 (EGFR) Show Efficient Anti-Tumor Activity against Head and Neck Squamous Cell Carcinoma (HNSCC).

(1) Background: HNSCC is a highly heterogeneous and relapse-prone form of cancer. We aimed to expand the immunological tool kit against HNSCC by conducting a functional screen to generate chimeric antigen receptor (CAR)-NK-92 cells that target HER1/epidermal growth factor receptor (EGFR). (2) Methods: Selected CAR-NK-92 cell candidates were tested for enhanced reduction of target cells, CD107a expression and IFNγ secretion in different co-culture models. For representative HNSCC models, patient-derived primary HNSCC (pHNSCC) cell lines were generated by employing an EpCAM-sorting approach to eliminate the high percentage of non-malignant cells found. (3) Results: 2D and 3D spheroid co-culture experiments showed that anti-HER1 CAR-NK-92 cells effectively eliminated SCC cell lines and primary HNSCC (pHNSCC) cells. Co-culture of tumor models with anti-HER1 CAR-NK-92 cells led to enhanced degranulation and IFNγ secretion of NK-92 cells and apoptosis of target cells. Furthermore, remaining pHNSCC cells showed upregulated expression of putative cancer stem cell marker CD44v6. (4) Conclusions: These results highlight the promising potential of CAR-NK cell therapy in HNSCC and the likely necessity to target multiple tumor-associated antigens to reduce currently high relapse rates.

Human lung virtual histology by multi-scale x-ray phase-contrast computed tomography.

Objectives.As the central organ of the respiratory system, the human lung is responsible for supplying oxygen to the blood, which reaches the erythrocytes by diffusion through the alveolar walls and is then distributed throughout the body. By exploiting the difference in electron density detected by a phase shift in soft tissue, high-resolution x-ray phase-contrast computed tomography (XPCT) can resolve biological structures in a sub-µm range, shedding new light on the three-dimensional structure of the lungs, physiological functions and pathological mechanisms.Approach.This work presents both synchrotron and laboratory XPCT results of postmortem tissue from autopsies and biopsies embedded with various preparation protocols such as precision-cut lung slices, cryogenically fixed lung tissue, as well as paraffin and alcohol fixed tissue. The selection of pathological abnormalities includes channel of Lambert, bronchus-associated lymphoid tissue and alveolar capillary dysplasia with misalignment of pulmonary veins. Subsequently, quantification and visualization approaches are presented.Main results.The overall high image quality even of in-house XPCT scans for the case of FFPE biopsies can be exploited for a wide range of pulmonary pathologies and translated to dedicated and optimized instrumentation which could be operated in clinical setting. By using synchrotron radiation, contrast can be further increased to resolve sub-µm sized features down to the sub-cellular level. The results demonstrate that a wide range of preparation protocols including sample mounting in liquids can be used.Significance.With XPCT, poorly understood 3D structures can be identified in larger volume overview and subsequently studied in more detail at higher resolution. With the full 3D structure, the respective physiological functions of airways or vascular networks, and the different pathophysiologic mechanisms can be elucidated or at least underpinned with structural data. Moreover, synchrotron data can be used to validate laboratory protocols and provide ground truth for standardizing the method.

Inflammation and vascular remodeling in COVID-19 hearts.

A wide range of cardiac symptoms have been observed in COVID-19 patients, often significantly influencing the clinical outcome. While the pathophysiology of pulmonary COVID-19 manifestation has been substantially unraveled, the underlying pathomechanisms of cardiac involvement in COVID-19 are largely unknown. In this multicentre study, we performed a comprehensive analysis of heart samples from 24 autopsies with confirmed SARS-CoV-2 infection and compared them to samples of age-matched Influenza H1N1 A (n = 16), lymphocytic non-influenza myocarditis cases (n = 8), and non-inflamed heart tissue (n = 9). We employed conventional histopathology, multiplexed immunohistochemistry (MPX), microvascular corrosion casting, scanning electron microscopy, X-ray phase-contrast tomography using synchrotron radiation, and direct multiplexed measurements of gene expression, to assess morphological and molecular changes holistically. Based on histopathology, none of the COVID-19 samples fulfilled the established diagnostic criteria of viral myocarditis. However, quantification via MPX showed a significant increase in perivascular CD11b/TIE2 + -macrophages in COVID-19 over time, which was not observed in influenza or non-SARS-CoV-2 viral myocarditis patients. Ultrastructurally, a significant increase in intussusceptive angiogenesis as well as multifocal thrombi, inapparent in conventional morphological analysis, could be demonstrated. In line with this, on a molecular level, COVID-19 hearts displayed a distinct expression pattern of genes primarily coding for factors involved in angiogenesis and epithelial-mesenchymal transition (EMT), changes not seen in any of the other patient groups. We conclude that cardiac involvement in COVID-19 is an angiocentric macrophage-driven inflammatory process, distinct from classical anti-viral inflammatory responses, and substantially underappreciated by conventional histopathologic analysis. For the first time, we have observed intussusceptive angiogenesis in cardiac tissue, which we previously identified as the linchpin of vascular remodeling in COVID-19 pneumonia, as a pathognomic sign in affected hearts. Moreover, we identified CD11b + /TIE2 + macrophages as the drivers of intussusceptive angiogenesis and set forward a putative model for the molecular regulation of vascular alterations.

Idiopathic Aneurysm of the Aortic Arch in an Infant.

Congenital aortic aneurysms are rare disorders, usually associated with genetic aortic syndromes. Here, we describe the case of an idiopathic aortic arch aneurysm which had been diagnosed prenatally by fetal echocardiography. The diagnosis was confirmed after birth in the neonatal period and successful surgical resection of the aneurysm was performed at the age of 3 months. The idiopathic etiology of the aneurysm, its localization, and the early surgical resection render this case very unusual.

A Morphomolecular Approach to Alveolar Capillary Dysplasia.

Alveolar capillary dysplasia (ACD) is a rare lung developmental disorder leading to persistent pulmonary arterial hypertension and fatal outcomes in newborns. The current study analyzed the microvascular morphology and the underlying molecular background of ACD. One ACD group (n = 7), one pulmonary arterial hypertension group (n = 20), and one healthy con1trol group (n = 16) were generated. Samples of histologically confirmed ACD were examined by exome sequencing and array-based comparative genomic hybridization. Vascular morphology was analyzed using scanning electron microscopy of microvascular corrosion casts. Gene expression and biological pathways were analyzed using two panels on inflammation/kinase-specific genes and a comparison analysis tool. Compartment-specific protein expression was analyzed using immunostaining. In ACD, there was an altered capillary network, a high prevalence of intussusceptive angiogenesis, and increased activity of C-X-C motif chemokine receptor 4 (CXCR4), hypoxia-inducible factor 1α (HIF1A), and angiopoietin signaling pathways compared with pulmonary arterial hypertension/healthy controls. Histologically, there was a markedly increased prevalence of endothelial tyrosine kinase receptor (TEK/TIE2)+ macrophages in ACD, compared with the other groups, whereas the CXCR4 ligand CXCL12 and HIF1A showed high expression in all groups. ACD is characterized by dysfunctional capillaries and a high prevalence of intussusceptive angiogenesis. The results indicate that endothelial CXCR4, HIF1A, and angiopoietin signaling as well as TIE2+ macrophages are crucial for the induction of intussusceptive angiogenesis and vascular remodeling. Future studies should address the use of anti-angiogenic agents in ACD, where TIE2 appears as a promising target.

Safety and efficacy of prophylactic and therapeutic vaccine based on live-attenuated Listeria monocytogenes in hepatobiliary cancers.

Primary liver cancer (PLC) comprising hepatocellular carcinoma (HCC) and cholangiocarcinoma (CCA) represents the third deadliest cancer worldwide with still insufficient treatment options. We have previously found that CD4 T helper 1 (Th1) response is indispensable for the protection against PLC. In the present research, we aimed to test the potent inducers of Th1 responses, live-attenuated Listeria monocytogenes ∆actA/∆inlB strain as preventive/therapeutic vaccine candidate in liver fibrosis, HCC, and CCA. Studies were performed using autochthonous models of HCC and CCA, highly reflecting human disease. L. monocytogenes ∆actA/∆inlB demonstrated strong safety/efficacy in premalignant and malignant liver diseases. The protective mechanism relied on the induction of strong tumor-specific immune responses that keep the development of hepatobiliary cancers under control. Combination therapy, comprising Listeria vaccination and a checkpoint inhibitor blockade significantly extended the survival of HCC-bearing mice even at the advanced stages of the disease. This is the first report on the safety and efficacy of Listeria-based vaccine in liver fibrosis, as well as the first proof of principle study on Listeria-based vaccines in CCA. Our study paves the way for the use of live-attenuated Listeria as safe and efficient vaccine and a potent inducer of protective immune responses in liver fibrosis and hepatobiliary malignancies.

B Cells Are Not Involved in the Regulation of Adenoviral TGF-ß1- 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-ß1 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-ß1 or BLM as for WT mice. Comparative transcriptomic profiling of sorted B cells collected from lungs of AdTGF-ß1- 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.

Comparative Analysis of Gene Expression in Fibroblastic Foci in Patients with Idiopathic Pulmonary Fibrosis and Pulmonary Sarcoidosis.

BACKGROUND: Fibroblastic foci (FF) are characteristic features of usual interstitial pneumonia (UIP)/idiopathic pulmonary fibrosis (IPF) and one cardinal feature thought to represent a key mechanism of pathogenesis. Hence, FF have a high impact on UIP/IPF diagnosis in current guidelines. However, although less frequent, these histomorphological hallmarks also occur in other fibrotic pulmonary diseases. Currently, there is therefore a gap in knowledge regarding the underlying molecular similarities and differences of FF in different disease entities. METHODS: In this work, we analyzed the compartment-specific gene expression profiles of FF in IPF and sarcoidosis in order to elucidate similarities and differences as well as shared pathomechanisms. For this purpose, we used laser capture microdissection, mRNA and protein expression analysis. Biological pathway analysis was performed using two different gene expression databases. As control samples, we used healthy lung tissue that was donated but not used for lung transplantation. RESULTS: Based on Holm Bonferroni corrected expression data, mRNA expression analysis revealed a significantly altered expression signature for 136 out of 760 genes compared to healthy controls while half of these showed a similar regulation in both groups. Immunostaining of selected markers from each group corroborated these results. However, when comparing all differentially expressed genes with the fdr-based expression data, only 2 of these genes were differentially expressed between sarcoidosis and IPF compared to controls, i.e., calcium transport protein 1 (CAT1) and SMAD specific E3 ubiquitin protein ligase 1 (SMURF1), both in the sarcoidosis group. Direct comparison of sarcoidosis and IPF did not show any differentially regulated genes independent from the statistical methodology. Biological pathway analysis revealed a number of fibrosis-related pathways pronounced in IPF without differences in the regulatory direction. CONCLUSIONS: These results demonstrate that FF of end-stage IPF and sarcoidosis lungs, although different in initiation, are similar in gene and protein expression, encouraging further studies on the use of antifibrotic agents in sarcoidosis.

Time-Dependent Molecular Motifs of Pulmonary Fibrogenesis in COVID-19.

(1) Background: In COVID-19 survivors there is an increased prevalence of pulmonary fibrosis of which the underlying molecular mechanisms are poorly understood; (2) Methods: In this multicentric study, n = 12 patients who succumbed to COVID-19 due to progressive respiratory failure were assigned to an early and late group (death within ≤7 and >7 days of hospitalization, respectively) and compared to n = 11 healthy controls; mRNA and protein expression as well as biological pathway analysis were performed to gain insights into the evolution of pulmonary fibrogenesis in COVID-19; (3) Results: Median duration of hospitalization until death was 3 (IQR25-75, 3-3.75) and 14 (12.5-14) days in the early and late group, respectively. Fifty-eight out of 770 analyzed genes showed a significantly altered expression signature in COVID-19 compared to controls in a time-dependent manner. The entire study group showed an increased expression of BST2 and IL1R1, independent of hospitalization time. In the early group there was increased activity of inflammation-related genes and pathways, while fibrosis-related genes (particularly PDGFRB) and pathways dominated in the late group; (4) Conclusions: After the first week of hospitalization, there is a shift from pro-inflammatory to fibrogenic activity in severe COVID-19. IL1R1 and PDGFRB may serve as potential therapeutic targets in future studies.

Complications and Disasters After Minimally Invasive Tissue Augmentation with Different Types of Fillers: A Retrospective Analysis.

BACKGROUND: The interest in youthful appearance and rejuvenating procedures is unbroken in our society. Besides surgical procedures, permanent fillers are utilized. The incorrect and unprofessional use of these substances, auto-injections in particular, have devastating results for patients and are challenging for the plastic surgeon. The aim of this retrospective study was to delineate the differences between permanent and non-permanent filler complications and appropriate treatment options. METHODS: We conducted a retrospective study and researched the hospital information system in the time period from 2001 to 2020. Patients with unprofessional use of permanent fillers, auto-injections and injections of unformulated substances were determined. Age, gender, localization, complications, length of hospital stay, comorbidities, histopathological workups and surgical salvage procedures were noted. Descriptive statistics were calculated. RESULTS: Seventeen patients were identified from 2001 till 2020. In four cases, auto-injections by the patients were the cause, whereas in the other patients the injections were performed by medical staff. Ages range from 18 to 57 years. Fourteen patients were female and three were male. The injected substances could be recognized as synthol, silicone, vaseline, fat tissue, hyaluronic acid as well as non-medical substances. Surgical procedures were necessary in eleven cases. One patient died because of the underlying diseases. CONCLUSION: Our results indicate different sequels of filler materials injected in an unprofessional way, possible complications, conservative and surgical techniques to resolve these rare complications. We suggest a staged therapy adjusted to the clinical symptoms. Milder symptoms can be handled conservatively, whereas severe infections, skin breakdowns or persistent granuloma are justifying indications for surgical treatment. LEVEL OF EVIDENCE V: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Circulating microRNAs in Symptomatic and Asymptomatic Carotid Stenosis.

Background: Specific microRNAs (miRs) have been implicated in the pathophysiology of atherosclerosis and may represent interesting diagnostic and therapeutic targets in carotid stenosis. We hypothesized that the levels of specific circulating miRs are altered in patients with symptomatic carotid stenosis (sCS) in comparison to those in patients with asymptomatic carotid stenosis (aCS) planned to undergo carotid endarterectomy (CEA). We also studied whether miR levels are associated with plaque vulnerability and stability over time after CEA. Methods: Circulating levels of vascular-enriched miR-92a, miR-126, miR-143, miR-145, miR-155, miR-210, miR-221, miR-222, and miR-342-3p were determined in 21 patients with sCS and 23 patients with aCS before CEA and at a 90-day follow-up. Transcranial Doppler ultrasound for detection of microembolic signals (MES) in the ipsilateral middle cerebral artery was performed prior to CEA. Carotid plaques were histologically analyzed. Results: Mean levels of miRs were not considerably different between groups and were only marginally higher in sCS than aCS concerning miR-92a, miR-210, miR-145, and miR-143 with the best evidence concerning miR-92a. After adjustment for vascular risk factors and statin pre-treatment, the effect sizes remained essentially unchanged. At follow-up, however, these modest differences remained uncorroborated. There were no relevant associations between miR-levels and MES or histological plaque vulnerability features. Conclusions: This study does not provide evidence for strong associations between specific circulating miRs and symptomatic state in a collective of comprehensively characterized patients with carotid stenosis. Further work is needed to elucidate the role of circulating miRs as targets in advanced carotid atherosclerosis.

Genetic Deletion of Polo-Like Kinase 2 Induces a Pro-Fibrotic Pulmonary Phenotype.

Pulmonary fibrosis is the chronic-progressive replacement of healthy lung tissue by extracellular matrix, leading to the destruction of the alveolar architecture and ultimately death. Due to limited pathophysiological knowledge, causal therapies are still missing and consequently the prognosis is poor. Thus, there is an urgent clinical need for models to derive effective therapies. Polo-like kinase 2 (PLK2) is an emerging regulator of fibroblast function and fibrosis. We found a significant downregulation of PLK2 in four different entities of human pulmonary fibrosis. Therefore, we characterized the pulmonary phenotype of PLK2 knockout (KO) mice. Isolated pulmonary PLK2 KO fibroblasts displayed a pronounced myofibroblast phenotype reflected by increased expression of αSMA, reduced proliferation rates and enhanced ERK1/2 and SMAD2/3 phosphorylation. In PLK2 KO, the expression of the fibrotic cytokines osteopontin and IL18 was elevated compared to controls. Histological analysis of PLK2 KO lungs revealed early stage remodeling in terms of alveolar wall thickening, increased alveolar collagen deposition and myofibroblast foci. Our results prompt further investigation of PLK2 function in pulmonary fibrosis and suggest that the PLK2 KO model displays a genetic predisposition towards pulmonary fibrosis, which could be leveraged in future research on this topic.