Repetitive intratracheal bleomycin models several features of idiopathic pulmonary fibrosis

Mapping spatially resolved transcriptomes in human and mouse pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive lung disease with poor prognosis and limited treatment options. Efforts to identify effective treatments are thwarted by limited understanding of IPF pathogenesis and poor translatability of available preclinical models. Here we generated spatially resolved transcriptome maps of human IPF (n = 4) and bleomycin-induced mouse pulmonary fibrosis (n = 6) to address these limitations. We uncovered distinct fibrotic niches in the IPF lung, characterized by aberrant alveolar epithelial cells in a microenvironment dominated by transforming growth factor beta signaling alongside predicted regulators, such as TP53 and APOE. We also identified a clear divergence between the arrested alveolar regeneration in the IPF fibrotic niches and the active tissue repair in the acutely fibrotic mouse lung. Our study offers in-depth insights into the IPF transcriptional landscape and proposes alveolar regeneration as a promising therapeutic strategy for IPF.

Changes in PI3K/AKT and NRF2/HO-1 signaling expression and intestinal microbiota in bleomycin-induced pulmonary fibrosis

Pulmonary fibrosis is the outcome of the prolonged interstitial pneumonia, characterized by excessive accumulation of fibroblasts and collagen deposition, leading to its development. This study aimed to study the changes in PI3K/AKT and NRF2/HO-1 signaling expression and intestinal microbiota in a rat model of a novel bleomycin-induced pulmonary fibrosis. The findings of our study showed the model was successfully established. The results showed that the alveolar septum in the model was significantly widened and infiltrated by severe inflammatory cells. Alveolar atrophy occurred due to the formation of multiple inflammatory foci. During this period, fibrous tissue was distributed in strips and patches, primarily around the pulmonary interstitium and bronchus. Moreover, lung damage and fibrosis progressively worsened over time. The mRNA expression of HO-1 and NRF2 in the model decreased while the mRNA expression of HIF-1α, VEGF, PI3K and AKT increased. Furthermore, it was observed to decrease the protein expression of E-cad, HO-1 and NRF2, and increase the protein expression of α-SMA and p-AKT. Additionally, this model leaded to an imbalance in the intestinal microbiota. This study demonstrate that the novel pulmonary fibrosis model activates the NRF2/HO-1 pathway and the PI3K/AKT pathway in rat lung tissues, and leading to intestinal barrier disorder.

Procyanidin C1 inhibits bleomycin-induced pulmonary fibrosis in mice by selective clearance of senescent myofibroblasts

Pulmonary fibrosis is a formidable challenge in chronic and age-related lung diseases. Myofibroblasts secrete large amounts of extracellular matrix and induce pro-repair responses during normal wound healing. Successful tissue repair results in termination of myofibroblast activity via apoptosis; however, some myofibroblasts exhibit a senescent phenotype and escape apoptosis, causing over-repair that is characterized by pathological fibrotic scarring. Therefore, the removal of senescent myofibroblasts using senolytics is an important method for the treatment of pulmonary fibrosis. Procyanidin C1 (PCC1) has recently been discovered as a senolytic compound with very low toxicity and few side effects. This study aimed to determine whether PCC1 could improve lung fibrosis by promoting apoptosis in senescent myofibroblasts and to investigate the mechanisms involved. The results showed that PCC1 attenuates bleomycin (BLM)-induced pulmonary fibrosis in mice. In addition, we found that PCC1 inhibited extracellular matrix deposition and promoted the apoptosis of senescent myofibroblasts by increasing PUMA expression and activating the BAX signaling pathway. Our findings represent a new method of pulmonary fibrosis management and emphasize the potential of PCC1 as a senotherapeutic agent for the treatment of pulmonary fibrosis, providing hope for patients with pulmonary fibrosis worldwide. Our results advance our understanding of age-related diseases and highlight the importance of addressing cellular senescence in treatment.

Immune mechanisms in fibrotic interstitial lung disease

Fibrotic interstitial lung diseases (fILDs) have poor survival rates and lack effective therapies. Despite evidence for immune mechanisms in lung fibrosis, immunotherapies have been unsuccessful for major types of fILD. Here, we review immunological mechanisms in lung fibrosis that have the potential to impact clinical practice. We first examine innate immunity, which is broadly involved across fILD subtypes. We illustrate how innate immunity in fILD involves a complex interplay of multiple cell subpopulations and molecular pathways. We then review the growing evidence for adaptive immunity in lung fibrosis to provoke a re-examination of its role in clinical fILD. We close with future directions to address key knowledge gaps in fILD pathobiology: (1) longitudinal studies emphasizing early-stage clinical disease, (2) immune mechanisms of acute exacerbations, and (3) next-generation immunophenotyping integrating spatial, genetic, and single-cell approaches. Advances in these areas are essential for the future of precision medicine and immunotherapy in fILD.

Fuzheng Huayu recipe inhibits bleomycin-induced pulmonary fibrosis in rats by inhibiting M2 polarization of macrophages via the oxidative phosphorylation pathway

Fuzheng Huayu recipe (FZHYR) is a Chinese patent medicine for the treatment of fibrosis. The effects of FZHYR on pulmonary fibrosis and macrophage polarization were investigated in vitro. FZHYR inhibited pulmonary inflammation and fibrosis and M2 polarization of macrophages in bleomycin-induced pulmonary fibrosis (BPF) of rat model. Differentially expressed genes were screened by high-throughput mRNA sequencing and GSEA showed that oxidative phosphorylation (OXPHOS) was correlated with BPF. FZHYR inhibited expressions of Ndufa2 and Ndufa6 in lung tissues of BPF rats. These findings suggest that OXPHOS pathway serves as a possible target for pulmonary fibrosis therapy by FZHYR.

Noninvasive assessment of the lung inflammation-fibrosis axis by targeted imaging of CMKLR1

Precision management of fibrotic lung diseases is challenging due to their diverse clinical trajectories and lack of reliable biomarkers for risk stratification and therapeutic monitoring. Here, we validated the accuracy of CMKLR1 as an imaging biomarker of the lung inflammation-fibrosis axis. By analyzing single-cell RNA sequencing datasets, we demonstrated CMKLR1 expression as a transient signature of monocyte-derived macrophages (MDMφ) enriched in patients with idiopathic pulmonary fibrosis (IPF). Consistently, we identified MDMφ as the major driver of the uptake of CMKLR1-targeting peptides in a murine model of bleomycin-induced lung fibrosis. Furthermore, CMKLR1-targeted positron emission tomography in the murine model enabled quantification and spatial mapping of inflamed lung regions infiltrated by CMKLR1-expressing macrophages and emerged as a robust predictor of subsequent lung fibrosis. Last, high CMKLR1 expression by bronchoalveolar lavage cells identified an inflammatory endotype of IPF with poor survival. Our investigation supports the potential of CMKLR1 as an imaging biomarker for endotyping and risk stratification of fibrotic lung diseases.

A novel senolytic drug for pulmonary fibrosis: BTSA1 targets apoptosis of senescent myofibroblasts by activating BAX

Idiopathic pulmonary fibrosis is a progressive and age-related disease that results from impaired lung repair following injury. Targeting senescent myofibroblasts with senolytic drugs attenuates pulmonary fibrosis, revealing a detrimental role of these cells in pulmonary fibrosis. The mechanisms underlying the occurrence and persistence of senescent myofibroblasts in fibrotic lung tissue require further clarification. In this study, we demonstrated that senescent myofibroblasts are resistant to apoptosis by upregulating the proapoptotic protein BAX and antiapoptotic protein BCL-2 and BCL-XL, leading to BAX inactivation. We further showed that high levels of inactive BAX-mediated minority mitochondrial outer membrane permeabilization (minority MOMP) promoted DNA damage and myofibroblasts senescence after insult by a sublethal stimulus. Intervention of minority MOMP via the inhibition of caspase activity by quinolyl-valyl-O-methylaspartyl-[2,6-difluorophenoxy]-methyl ketone (QVD-OPH) or BAX knockdown significantly reduced DNA damage and ultimately delayed the progression of senescence. Moreover, the BAX activator BTSA1 selectively promoted the apoptosis of senescent myofibroblasts, as BTSA1-activated BAX converted minority MOMP to complete MOMP while not injuring other cells with low levels of BAX. Furthermore, therapeutic activation of BAX with BTSA1 effectively reduced the number of senescent myofibroblasts in the lung tissue and alleviated both reversible and irreversible pulmonary fibrosis. These findings advance the understanding of apoptosis resistance and cellular senescence mechanisms in senescent myofibroblasts in pulmonary fibrosis and demonstrate a novel senolytic drug for pulmonary fibrosis treatment.

CircRNA: a rising therapeutic strategy for lung injury induced by pulmonary toxicants

Lung injury has been a serious medical problem that requires new therapeutic approaches and biomarkers. Circular RNAs (circRNAs) are non-coding RNAs (ncRNAs) that exist widely in eukaryotes. CircRNAs are single-stranded RNAs that form covalently closed loops. CircRNAs are significant gene regulators that have a role in the development, progression, and therapy of lung injury by controlling transcription, translating into protein, and sponging microRNAs (miRNAs) and proteins. Although the study of circRNAs in lung injury caused by pulmonary toxicants is just beginning, several studies have revealed their expression patterns. The function that circRNAs perform in relation to pulmonary toxicants (severe acute respiratory distress syndrome coronavirus-2 (SARS-CoV-2), drug abuse, PM2.5, and cigarette smoke) is the main topic of this review. A variety of circRNAs can serve as potential biomarkers of lung injury. In this review, the biogenesis, properties, and biological functions of circRNAs were concluded, and the relationship between circRNAs and pulmonary toxicants was discussed. It is expected that the new ideas and potential treatment targets that circRNAs provide would be beneficial to research into the molecular mechanisms behind lung injury.

DNA-PKcs/AKT1 inhibits epithelial-mesenchymal transition during radiation-induced pulmonary fibrosis by inducing ubiquitination and degradation of Twist1

INTRODUCTION

Radiation-induced pulmonary fibrosis (RIPF) is a chronic, progressive, irreversible lung interstitial disease that develops after radiotherapy. Although several previous studies have focused on the mechanism of epithelial-mesenchymal transition (EMT) in lung epithelial cells, the essential factors involved in this process remain poorly understood. The DNA-dependent protein kinase catalytic subunit (DNA-PKcs) exhibits strong repair capacity when cells undergo radiation-induced damage; whether DNA-PKcs regulates EMT during RIPF remains unclear.

OBJECTIVES

To investigate the role and molecular mechanism of DNA-PKcs in RIPF and provide an important theoretical basis for utilising DNA-PKcs-targeted drugs for preventing RIPF.

METHODS

DNA-PKcs knockout (DPK-/-) mice were generated via the Cas9/sgRNA technique and subjected to whole chest ionizing radiation (IR) at a 20 Gy dose. Before whole chest IR, the mice were intragastrically administered the DNA-PKcs-targeted drug VND3207. Lung tissues were collected at 1 and 5 months after IR.

RESULTS

The expression of DNA-PKcs is low in pulmonary fibrosis (PF) patients. DNA-PKcs deficiency significantly exacerbated RIPF by promoting EMT in lung epithelial cells. Mechanistically, DNA-PKcs deletion by shRNA or inhibitor NU7441 maintained the protein stability of Twist1. Furthermore, AKT1 mediated the interaction between DNA-PKcs and Twist1. High Twist1 expression and EMT-associated changes caused by DNA-PKcs deletion were blocked by insulin-like growth factor-1 (IGF-1), an AKT1 agonist. The radioprotective drug VND3207 prevented IR-induced EMT and alleviated RIPF in mice by stimulating the kinase activity of DNA-PKcs.

CONCLUSION

Our study clarified the critical role and mechanism of DNA-PKcs in RIPF and showed that it could be a potential target for preventing RIPF.

Induction of lung lesions by bronchial administration using bronchoscope technique in mice

This study aimed to establish an exposure method that can induce homogeneous lesions with minimal inter-individual variability. The distribution of lesions induced by bleomycin (BLM) administration was also analyzed. C57BL mice were intrabronchially administered 20 µL of BLM (3 mg/mL) using a bronchoscope in the left or right bronchus. The mice were sacrificed 14 days after administration, and their lungs were evaluated histopathologically. BLM-induced inflammatory lesions were widely observed in the lungs. In the left bronchus-treated group, lesions were uniformly observed throughout the lobe, and no individual differences were noted. Meanwhile, in the right bronchus-treated group, individual differences in the distribution of the pulmonary lesions were observed. The distribution of lesions differed among the four lobes of the right lung owing to their anatomical features. Administration into the left bronchus is recommended for highly homogeneous lung exposure and for establishing models that contribute to highly accurate toxicity and efficacy evaluations.

Exosomal circRNAs in the plasma serve as novel biomarkers for IPF diagnosis and progression prediction

BACKGROUND

Idiopathic Pulmonary Fibrosis (IPF) is a type of chronic interstitial pneumonia, often fatal, with elusive causes and a bleak prognosis. Its treatment options are limited and largely ineffective. Early detection and precise diagnosis are pivotal in managing the disease effectively and enhancing patient survival rates. Recently, the quest for trustworthy biomarkers for IPF has gained momentum. Notably, emerging studies indicate that circular RNAs (circRNAs) found in exosomes may hold significant potential as valuable diagnostic markers.

METHODS

In this study, we initially explored the expression profile of circRNAs in exosomes sourced from the blood of IPF patients and healthy volunteers, employing a human circRNA microarray. We then utilized RT-qPCR to corroborate the dysregulated circRNAs identified by the microarray during the training phase. Next, the circRNAs that displayed a significant increase during the training phase were selected for further validation in a larger cohort encompassing 113 IPF patients and 76 healthy volunteers. Ultimately, the expression level and function of hsa_circ_0044226 were substantiated through a series of in vivo and in vitro experiments.

RESULTS

Utilizing a human circRNA microarray, we identified 11 dysregulated circRNAs in the exosomes derived from the blood of IPF patients and control volunteers. Subsequent RT-qPCR analysis revealed significant increases in three circRNAs (hsa_circ_0044226, hsa_circ_0004099, hsa_circ_0008898) within the IPF patients. Notably, hsa_circ_0044226 was markedly elevated in patients experiencing acute exacerbation of IPF (AE-IPF) compared to those with stable IPF (S-IPF). Additionally, an upregulation of hsa_circ_0044226 was observed in the blood exosomes derived from a bleomycin-induced IPF mouse model.

CONCLUSION

The expression levels of hsa_circ_0044226, hsa_circ_0004099, and hsa_circ_0008898 in plasma exosomes introduce a new paradigm of biomarkers for the diagnosis and progression of IPF.

First magnetic particle imaging to assess pulmonary vascular leakage in vivo in the acutely injured and fibrotic lung

Increased pulmonary vascular permeability is a characteristic feature of lung injury. However, there are no established methods that allow the three-dimensional visualization and quantification of pulmonary vascular permeability in vivo. Evans blue extravasation test and total protein test of bronchoalveolar lavage fluid (BALF) are permeability assays commonly used in research settings. However, they lack the ability to identify the spatial and temporal heterogeneity of endothelial barrier disruption, which is typical in lung injuries. Magnetic resonance (MR) and near-infrared (NIR) imaging have been proposed to image pulmonary permeability, but suffer from limited sensitivity and penetration depth, respectively. In this study, we report the first use of magnetic particle imaging (MPI) to assess pulmonary vascular leakage noninvasively in vivo in mice. A dextran-coated superparamagnetic iron oxide (SPIO), synomag®, was employed as the imaging tracer, and pulmonary SPIO extravasation was imaged and quantified to evaluate the vascular leakage. Animal models of acute lung injury and pulmonary fibrosis (PF) were used to validate the proposed method. MPI sensitively detected the SPIO extravasation in both acutely injured and fibrotic lungs in vivo, which was confirmed by ex vivo imaging and Prussian blue staining. Moreover, 3D MPI illustrated the spatial heterogeneity of vascular leakage, which correlated well with CT findings. Based on the in vivo 3D MPI images, we defined the SPIO extravasation index (SEI) to quantify the vascular leakage. A significant increase in SEI was observed in the injured lungs, in consistent with the results obtained via ex vivo permeability assays. Overall, our results demonstrate that 3D quantitative MPI serves as a useful tool to examine pulmonary vascular integrity in vivo, which shows promise for future clinical translation.

An injury-induced tissue niche shaped by mesenchymal plasticity coordinates the regenerative and disease response in the lung

Severe lung injury causes basal stem cells to migrate and outcompete alveolar stem cells resulting in dysplastic repair and a loss of gas exchange function. This "stem cell collision" is part of a multistep process that is now revealed to generate an injury-induced tissue niche (iTCH) containing Keratin 5+ epithelial cells and plastic Pdgfra+ mesenchymal cells. Temporal and spatial single cell analysis reveals that iTCHs are governed by mesenchymal proliferation and Notch signaling, which suppresses Wnt and Fgf signaling in iTCHs. Conversely, loss of Notch in iTCHs rewires alveolar signaling patterns to promote euplastic regeneration and gas exchange. The signaling patterns of iTCHs can differentially phenotype fibrotic from degenerative human lung diseases, through apposing flows of FGF and WNT signaling. These data reveal the emergence of an injury and disease associated iTCH in the lung and the ability of using iTCH specific signaling patterns to discriminate human lung disease phenotypes.

Time course of histopathology of bleomycin-induced pulmonary fibrosis using an intratracheal sprayer in mice

Idiopathic pulmonary fibrosis (IPF) is a poor prognosis disease that affects approximately 5 million people worldwide, and the detailed mechanisms underlying the pathogenesis of IPF remain unclear. Bleomycin-induced pulmonary fibrosis has been widely used as a representative animal model of IPF that induces fibrosis in lung tissue. The lungs of rodent consist of five lobes and each bronchus enters each lobe of the lung at a different bifurcation angle, path length, and diameter. The method of administration of bleomycin is considered as important thing to establish appropriate animal models. We conducted a time-dependent histopathological study to examine how pulmonary fibrosis develops in each lung lobe when bleomycin was intratracheally sprayed in ICR mice. And we then explored the suitable points for evaluation of anti-fibrotic agents in this model. As a result, we found that homogeneous fibrosis was induced in the 5 lobes of the lungs following initial inflammation. The expression of transforming growth factor (TGF)-β1 and phospho-Smad2 (pSmad2) was observed from Day 1, and their positivity increased until Day 21. In conclusion, we have observed a detailed time course of histological changes in bleomycin-induced pulmonary fibrosis in ICR mice using the aerosolization technique. We found that our protocol can induce a highly homogeneous lesion in the lung and that the most suitable time point to assess anti-fibrotic agents is 14 days after treatment in this model.

Qingfei Tongluo Mixture Attenuates Bleomycin-Induced Pulmonary Inflammation and Fibrosis through mTOR-Dependent Autophagy in Rats

As an interstitial fibrosis disease characterized by diffuse alveolitis and structural alveolar disorders, idiopathic pulmonary fibrosis (IPF) has high lethality but lacks limited therapeutic drugs. A hospital preparation used for the treatment of viral pneumonia, Qingfei Tongluo mixture (QFTL), is rumored to have protective effects against inflammatory and respiratory disease. This study aims to confirm whether it has a therapeutic effect on bleomycin-induced IPF in rats and to elucidate its mechanism of action. Male SD rats were randomly divided into the following groups: control, model, CQ + QFTL (84 mg/kg chloroquine (CQ) + 3.64 g/kg QFTL), QFTL-L, M, H (3.64, 7.28, and 14.56 g/kg, respectively) and pirfenidone (PFD 420 mg/kg). After induction modeling and drug intervention, blood samples and lung tissue were collected for further detection. Body weight and lung coefficient were examined, combined with hematoxylin and eosin (H&E) and Masson staining to observe lung tissue lesions. The enzyme-linked immunosorbent assay (ELISA) and the hydroxyproline (HYP) assay kit were used to detect changes in proinflammatory factors (transforming growth factor-β (TGF-β), tumor necrosis factor-α (TNF-α), and interleukin-1β (IL-1β)) and HYP. Immunohistochemistry and Western blotting were performed to observe changes in proteins related to pulmonary fibrosis (α-smooth muscle actin (α-SMA) and matrix metalloproteinase 12 (MMP12)) and autophagy (P62 and mechanistic target of rapamycin (mTOR)). Treatment with QFTL significantly improved the adverse effects of bleomycin on body weight, lung coefficient, and pathological changes. Then, QFTL reduced bleomycin-induced increases in proinflammatory mediators and HYP. The expression changes of pulmonary fibrosis and autophagy marker proteins are attenuated by QFTL. Furthermore, the autophagy inhibitor CQ significantly reversed the downward trend in HYP levels and α-SMA protein expression, which QFTL improved in BLM-induced pulmonary fibrosis rats. In conclusion, QFTL could effectively attenuate bleomycin-induced inflammation and pulmonary fibrosis through mTOR-dependent autophagy in rats. Therefore, QFTL has the potential to be an alternative treatment for IPF in clinical practice.

Lung regeneration: diverse cell types and the therapeutic potential

Lung tissue has a certain regenerative ability and triggers repair procedures after injury. Under controllable conditions, lung tissue can restore normal structure and function. Disruptions in this process can lead to respiratory system failure and even death, causing substantial medical burden. The main types of respiratory diseases are chronic obstructive pulmonary disease (COPD), idiopathic pulmonary fibrosis (IPF), and acute respiratory distress syndrome (ARDS). Multiple cells, such as lung epithelial cells, endothelial cells, fibroblasts, and immune cells, are involved in regulating the repair process after lung injury. Although the mechanism that regulates the process of lung repair has not been fully elucidated, clinical trials targeting different cells and signaling pathways have achieved some therapeutic effects in different respiratory diseases. In this review, we provide an overview of the cell type involved in the process of lung regeneration and repair, research models, and summarize molecular mechanisms involved in the regulation of lung regeneration and fibrosis. Moreover, we discuss the current clinical trials of stem cell therapy and pharmacological strategies for COPD, IPF, and ARDS treatment. This review provides a reference for further research on the molecular and cellular mechanisms of lung regeneration, drug development, and clinical trials.

Catch your breath: The protective role of the angiotensin AT2 receptor for the treatment of idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive interstitial lung disease whereby excessive deposition of extracellular matrix proteins (ECM) ultimately leads to respiratory failure. While there have been advances in pharmacotherapies for pulmonary fibrosis, IPF remains an incurable and irreversible disease. There remains an unmet clinical need for treatments that reverse fibrosis, or at the very least have a more tolerable side effect profile than currently available treatments. Transforming growth factor β1(TGFβ1) is considered the main driver of fibrosis in IPF. However, as our understanding of the role of the pulmonary renin-angiotensin system (PRAS) in the pathogenesis of IPF increases, it is becoming clear that targeting angiotensin receptors represents a potential novel treatment strategy for IPF - in particular, via activation of the anti-fibrotic angiotensin type 2 receptor (AT2R). This review describes the current understanding of the pathophysiology of IPF and the mediators implicated in its pathogenesis; focusing on TGFβ1, angiotensin II and related peptides in the PRAS and their contribution to fibrotic processes in the lung. Preclinical and clinical assessment of currently available AT2R agonists and the development of novel, highly selective ligands for this receptor will also be described, with a focus on compound 21, currently in clinical trials for IPF. Collectively, this review provides evidence of the potential of AT2R as a novel therapeutic target for IPF.

Macrophages and fibrosis: how resident and infiltrating mononuclear phagocytes account for organ injury, regeneration or atrophy

Mononuclear phagocytes (MP), i.e., monocytes, macrophages, and dendritic cells (DCs), are essential for immune homeostasis via their capacities to clear pathogens, pathogen components, and non-infectious particles. However, tissue injury-related changes in local microenvironments activate resident and infiltrating MP towards pro-inflammatory phenotypes that contribute to inflammation by secreting additional inflammatory mediators. Efficient control of injurious factors leads to a switch of MP phenotype, which changes the microenvironment towards the resolution of inflammation. In the same way, MP endorses adaptive structural responses leading to either compensatory hypertrophy of surviving cells, tissue regeneration from local tissue progenitor cells, or tissue fibrosis and atrophy. Under certain circumstances, MP contribute to the reversal of tissue fibrosis by clearance of the extracellular matrix. Here we give an update on the tissue microenvironment-related factors that, upon tissue injury, instruct resident and infiltrating MP how to support host defense and recover tissue function and integrity. We propose that MP are not intrinsically active drivers of organ injury and dysfunction but dynamic amplifiers (and biomarkers) of specific tissue microenvironments that vary across spatial and temporal contexts. Therefore, MP receptors are frequently redundant and suboptimal targets for specific therapeutic interventions compared to molecular targets upstream in adaptive humoral or cellular stress response pathways that influence tissue milieus at a contextual level.

Omentin-1 induces mechanically activated fibroblasts lipogenic differentiation through pkm2/yap/pparγ pathway to promote lung fibrosis resolution

Idiopathic pulmonary fibrosis (IPF) is a progressive and fatal lung disease characterized by extensive extracellular matrix (ECM) deposition by activated myofibroblasts, which are specialized hyper-contractile cells that promote ECM remodeling and matrix stiffening. New insights on therapeutic strategies aimed at reversing fibrosis by targeting myofibroblast fate are showing promise in promoting fibrosis resolution. Previously, we showed that a novel adipocytokine, omentin-1, attenuated bleomycin (BLM)-induced lung fibrosis by reducing the number of myofibroblasts. Apoptosis, deactivation, and reprogramming of myofibroblasts are important processes in the resolution of fibrosis. Here we report that omentin-1 reverses established lung fibrosis by promoting mechanically activated myofibroblasts dedifferentiation into lipofibroblasts. Omentin-1 promotes myofibroblasts lipogenic differentiation by inhibiting dimerization and nuclear translocation of glycolytic enzymes pyruvate kinase isoform M2 (PKM2) and activation of the downstream Yes-associated protein (YAP) by increasing the cofactor fructose-1,6-bisphosphate (F1, 6BP, FBP). Moreover, omentin-1 activates proliferator-activated receptor gamma (PPARγ) signaling, the master regulator of lipogenesis, and promotes the upregulation of the lipogenic differentiation-related protein perilipin 2 (PLIN2) by suppressing the PKM2-YAP pathway. Ultimately, omentin-1 facilitates myofibroblasts transformation into the lipofibroblast phenotype, with reduced collagen synthesis and enhanced degradation properties, which are crucial mechanisms to clear the ECM deposition in fibrotic tissue, leading to fibrosis resolution. Our results indicate that omentin-1 targets mechanical signal accelerates fibrosis resolution and reverses established lung fibrosis by promoting myofibroblasts lipogenic differentiation, which is closely associated with ECM clearance in fibrotic tissue. These findings suggest that targeting mechanical force to promote myofibroblast lipogenic differentiation is a promising therapeutic strategy against persistent lung fibrosis.

Anti-Inflammatory and Antifibrotic Potential of Longidaze in Bleomycin-Induced Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is one of the most common forms of interstitial lung disease, characterized by progressive parenchymal fibrosis and respiratory failure. In a model of bleomycin-induced pulmonary fibrosis, the antifibrotic and anti-inflammatory activity of Longidaze (Bovhyaluronidase Azoxymer), which contains a conjugate of the hyaluronidase enzyme with a high molecular weight synthetic carrier azoxymer bromide, was investigated. Experiments were conducted in male C57BL/6 mice. Longidaze was administered at different doses by intranasal and intramuscular routes. Histology, hematology, and enzyme-linked immunosorbent assay were used in the study. The use of Longidaze reduced pulmonary fibrosis, as evidenced by an improvement in histopathologic damage to the lungs, a decrease in the area of connective tissue, and the levels of profibrotic factors (TGF-β1, hydroxyproline, collagen I) in lung tissue. In addition, Longidaze inhibited the inflammatory response in pulmonary fibrosis, and decreased the levels of IL-6, TNF-α, and hyaluronic acid in lung tissue and the recruitment of inflammatory cells into lung tissue. The highest therapeutic efficacy was observed with the use of Longidaze at doses of 120 and 1200 U/kg intramuscularly, which was superior to that of the reference drug pirfenidone axunio. The data presented in this study suggest that Longidaze is a new and promising drug for the treatment of IPF that warrants further investigation in patients with fibrotic interstitial lung disease.

The Regenerative Power of Stem Cells: Treating Bleomycin-Induced Lung Fibrosis

Idiopathic pulmonary fibrosis (IPF) is a chronic and progressive lung disease with no known cure, characterized by the formation of scar tissue in the lungs, leading to respiratory failure. Although the exact cause of IPF remains unclear, the condition is thought to result from a combination of genetic and environmental factors. One of the most widely used animal models to study IPF is the bleomycin-induced lung injury model in mice. In this model, the administration of the chemotherapeutic agent bleomycin causes pulmonary inflammation and fibrosis, which closely mimics the pathological features of human IPF. Numerous recent investigations have explored the functions of various categories of stem cells in the healing process of lung injury induced by bleomycin in mice, documenting the beneficial effects and challenges of this approach. Differentiation of stem cells into various cell types and their ability to modulate tissue microenvironment is an emerging aspect of the regenerative therapies. This review article aims to provide a comprehensive overview of the role of stem cells in repairing bleomycin-induced lung injury. It delves into the mechanisms through which various types of stem cells, including mesenchymal stem cells, embryonic stem cells, induced pluripotent stem cells, and lung resident stem cells, exert their therapeutic effects in this specific model. We have also discussed the unique set of intermediate markers and signaling factors that can influence the proliferation and differentiation of alveolar epithelial cells both during lung repair and homeostasis. Finally, we highlight the challenges and opportunities associated with translating stem cell therapy to the clinic for IPF patients. The novelty and implications of this review extend beyond the understanding of the potential of stem cells in treating IPF to the broader field of regenerative medicine. We believe that the review paves the way for further advancements in stem cell therapies, offering hope for patients suffering from this debilitating and currently incurable disease.

Ficolin B secreted by alveolar macrophage exosomes exacerbates bleomycin-induced lung injury via ferroptosis through the cGAS-STING signaling pathway

Pathogenesis exploration and timely intervention of lung injury is quite necessary as it has harmed human health worldwide for years. Ficolin B (Fcn B) is a recognition molecule that can recognize a variety of ligands and play an important role in mediating the cell cycle, immune response, and tissue homeostasis in the lung. However, the role of Fcn B in bleomycin (BLM)-induced lung injury is obscure. This study aims to investigate the sources of Fcn B and its mechanism in BLM-induced lung injury. WT, Fcna-/-, and Fcnb-/- mice were selected to construct the BLM-induced lung injury model. Lung epithelial cells were utilized to construct the BLM-induced cell model. Exosomes that were secreted from alveolar macrophages (AMs) were applied for intervention by transporting Fcn B. Clinical data suggested M-ficolin (homologous of Fcn B) was raised in plasma of interstitial lung disease (ILD) patients. In the mouse model, macrophage-derived Fcn B aggravated BLM-induced lung injury and fibrosis. Fcn B further promoted the development of autophagy and ferroptosis. Remarkably, cell experiment results revealed that Fcn B transported by BLM-induced AMs exosomes accelerated autophagy and ferroptosis in lung epithelial cells through the activation of the cGAS-STING pathway. In contrast, the application of 3-Methyladenine (3-MA) reversed the promotion effect of Fcn B from BLM-induced AMs exosomes on lung epithelial cell damage by inhibiting autophagy-dependent ferroptosis. Meanwhile, in the BLM-induced mice model, the intervention of Fcn B secreted from BLM-induced AMs exosomes facilitated lung injury and fibrosis via ferroptosis. In summary, this study demonstrated that Fcn B transported by exosomes from AMs exacerbated BLM-induced lung injury by promoting lung epithelial cells ferroptosis through the cGAS-STING signaling pathway.

The vascular perspective on acute and chronic lung disease

The pulmonary vasculature has been frequently overlooked in acute and chronic lung diseases, such as acute respiratory distress syndrome (ARDS), pulmonary fibrosis (PF), and chronic obstructive pulmonary disease (COPD). The primary emphasis in the management of these parenchymal disorders has largely revolved around the injury and aberrant repair of epithelial cells. However, there is increasing evidence that the vascular endothelium plays an active role in the development of acute and chronic lung diseases. The endothelial cell network in the capillary bed and the arterial and venous vessels provides a metabolically highly active barrier that controls the migration of immune cells, regulates vascular tone and permeability, and participates in the remodeling processes. Phenotypically and functionally altered endothelial cells, and remodeled vessels, can be found in acute and chronic lung diseases, although to different degrees, likely because of disease-specific mechanisms. Since vascular remodeling is associated with pulmonary hypertension, which worsens patient outcomes and survival, it is crucial to understand the underlying vascular alterations. In this Review, we describe the current knowledge regarding the role of the pulmonary vasculature in the development and progression of ARDS, PF, and COPD; we also outline future research directions with the hope of facilitating the development of mechanism-based therapies.

Human senescent fibroblasts trigger progressive lung fibrosis in mice

Cell senescence has recently emerged as a potentially relevant pathogenic mechanism in fibrosing interstitial lung diseases (f-ILDs), particularly in idiopathic pulmonary fibrosis. We hypothesized that senescent human fibroblasts may suffice to trigger a progressive fibrogenic reaction in the lung. To address this, senescent human lung fibroblasts, or their secretome (SASP), were instilled into the lungs of immunodeficient mice. We found that: (1) human senescent fibroblasts engraft in the lungs of immunodeficient mice and trigger progressive lung fibrosis associated to increasing levels of mouse senescent cells, whereas non-senescent fibroblasts do not trigger fibrosis; (2) the SASP of human senescent fibroblasts is pro-senescence and pro-fibrotic both in vitro when added to mouse recipient cells and in vivo when delivered into the lungs of mice, whereas the conditioned medium (CM) from non-senescent fibroblasts lacks these activities; and, (3) navitoclax, nintedanib and pirfenidone ameliorate lung fibrosis induced by senescent human fibroblasts in mice, albeit only navitoclax displayed senolytic activity. We conclude that human senescent fibroblasts, through their bioactive secretome, trigger a progressive fibrogenic reaction in the lungs of immunodeficient mice that includes the induction of paracrine senescence in the cells of the host, supporting the concept that senescent cells actively contribute to disease progression in patients with f-ILDs.

Microcomputed tomography visualization and quantitation of the pulmonary arterial microvascular tree in mouse models of chronic lung disease

Pulmonary vascular dysfunction is characterized by remodeling and loss of microvessels in the lung and is a major manifestation of chronic lung diseases (CLD). In murine models of CLD, the small arterioles and capillaries are the first and most prevalent vessels that are affected by pruning and remodeling. Thus, visualization of the pulmonary arterial vasculature in three dimensions is essential to define pruning and remodeling both temporally and spatially and its role in the pathogenesis of CLD, aging, and tissue repair. To this end, we have developed a novel method to visualize and quantitate the murine pulmonary arterial circulation using microcomputed tomography (µCT) imaging. Using this perfusion technique, we can quantitate microvessels to approximately 6 µM in diameter. We hypothesize that bleomycin-induced injury would have a significant impact on the arterial vascular structure. As proof of principle, we demonstrated that as a result of bleomycin-induced injury at peak fibrosis, significant alterations in arterial vessel structure were visible in the three-dimensional models as well as quantification. Thus, we have successfully developed a perfusion methodology and complementary analysis techniques, which allows for the reconstruction, visualization, and quantitation of the mouse pulmonary arterial microvasculature in three-dimensions. This tool will further support the examination and understanding of angiogenesis during the development of CLD as well as repair following injury.

AAV9-Tspyl2 gene therapy retards bleomycin-induced pulmonary fibrosis by modulating downstream TGF-β signaling in mice

Idiopathic pulmonary fibrosis (IPF) is a devastating fibrotic lung disease characterized by scarring and destruction of the lung architecture, with limited treatment options. Targeted gene therapy to restore cell division autoantigen-1 (CDA1) expression may be a potential treatment approach to delay the progression of pulmonary fibrosis (PF). Here, we focused on CDA1, which was significantly decreased in human IPF, in a mouse model of bleomycin (BLM)-induced PF, and in transforming growth factor (TGF-β)-challenged lung fibroblasts. In vitro, CDA1 overexpression by lentivirus infection in human embryonic lung fibroblasts (HFL1 cells) inhibited the production of pro-fibrotic and pro-inflammatory cytokines, lung fibroblast-to-myofibroblast transition, and extracellular matrix protein expression induced by exogenous TGF-β1 treatment, whereas CDA1 knockdown with small interfering RNA promoted this effect. CDA1 overexpression also inhibited cell proliferation and migration. In a mouse model of BLM-induced PF, we provided novel evidence that the intratracheal delivery of adeno-associated virus serotype 9 carrying the mouse Tspyl2 gene reduced lung tissue inflammation and fibrosis. Mechanistically, CDA1, as a transcription regulator, could repress the TGF-β signal transduction in vivo and in vitro. In conclusion, our results show that Tspyl2 gene therapy plays an antifibrotic role by inhibiting the lung fibroblast-to-myofibroblast transition and downstream TGF-β/Smad3 signaling transduction in BLM-induced PF in mice, suggesting that CDA1 is an appropriate and promising therapeutic target for PF.

Insights on the mechanism of bleomycin to induce lung injury and associated in vivo models: A review

Acute lung injury leads to the development of chronic conditions such as idiopathic pulmonary fibrosis (IPF), chronic obstructive pulmonary disease (COPD), asthma as well as alveolar sarcoma. Various investigations are being performed worldwide to understand the pathophysiology of these diseases, develop novel bioactive compounds and inhibitors to target the ailment. Generally, in vivo models are used to understand the disease outcome and therapeutic suppressing effects for which the animals are chemically or physically induced to mimic the onset of definite disease conditions. Amongst the chemical inducing agents, Bleomycin (BLM) is the most successful inducer. It is reported to target various receptors and activate inflammatory pathways, cellular apoptosis, epithelial mesenchymal transition leading to the release of inflammatory cytokines, and proteases. Mice is one of the most widely used animal model for BLM induced pulmonary associated studies apart from rat, rabbit, sheep, pig, and monkey. Although, there is considerable variation amongst in vivo studies for BLM induction which suggests a detailed study on the same to understand the mechanism of action of BLM at molecular level. Hence, herein we have reviewed various chemical inducers, mechanism of action of BLM in inducing lung injury in vivo, its advantages and disadvantages. Further, we have also discussed the rationale behind various in vivo models and recent development in BLM induction for various animals.

Chronic pulmonary fibrosis alters the functioning of the respiratory neural network

Some patients with idiopathic pulmonary fibrosis present impaired ventilatory variables characterised by low forced vital capacity values associated with an increase in respiratory rate and a decrease in tidal volume which could be related to the increased pulmonary stiffness. The lung stiffness observed in pulmonary fibrosis may also have an effect on the functioning of the brainstem respiratory neural network, which could ultimately reinforce or accentuate ventilatory alterations. To this end, we sought to uncover the consequences of pulmonary fibrosis on ventilatory variables and how the modification of pulmonary rigidity could influence the functioning of the respiratory neuronal network. In a mouse model of pulmonary fibrosis obtained by 6 repeated intratracheal instillations of bleomycin (BLM), we first observed an increase in minute ventilation characterised by an increase in respiratory rate and tidal volume, a desaturation and a decrease in lung compliance. The changes in these ventilatory variables were correlated with the severity of the lung injury. The impact of lung fibrosis was also evaluated on the functioning of the medullary areas involved in the elaboration of the central respiratory drive. Thus, BLM-induced pulmonary fibrosis led to a change in the long-term activity of the medullary neuronal respiratory network, especially at the level of the nucleus of the solitary tract, the first central relay of the peripheral afferents, and the Pre-Bötzinger complex, the inspiratory rhythm generator. Our results showed that pulmonary fibrosis induced modifications not only of pulmonary architecture but also of central control of the respiratory neural network.

Group 2 innate lymphoid cells constrain type 3/17 lymphocytes in shared stromal niches to restrict liver fibrosis

Group 2 innate lymphoid cells (ILC2s) cooperate with adaptive Th2 cells as key organizers of tissue type 2 immune responses, while a spectrum of innate and adaptive lymphocytes coordinate early type 3/17 immunity. Both type 2 and type 3/17 lymphocyte associated cytokines are linked to tissue fibrosis, but how their dynamic and spatial topographies may direct beneficial or pathologic organ remodelling is unclear. Here we used volumetric imaging in models of liver fibrosis, finding accumulation of periportal and fibrotic tract IL-5 + lymphocytes, predominantly ILC2s, in close proximity to expanded type 3/17 lymphocytes and IL-33 high niche fibroblasts. Ablation of IL-5 + lymphocytes worsened carbon tetrachloride-and bile duct ligation-induced liver fibrosis with increased niche IL-17A + type 3/17 lymphocytes, predominantly γδ T cells. In contrast, concurrent ablation of IL-5 + and IL-17A + lymphocytes reduced this progressive liver fibrosis, suggesting a cross-regulation of type 2 and type 3 lymphocytes at specialized fibroblast niches that tunes hepatic fibrosis.

Tanreqing injection protects against bleomycin-induced pulmonary fibrosis via inhibiting STING-mediated endoplasmic reticulum stress signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Idiopathic pulmonary fibrosis (IPF), characterized by excessive collagen deposition, is a progressive and typically fatal lung disease without effective therapeutic methods. Tanreqing injection (TRQ), a Traditional Chinese Patent Medicine, has been widely used to treat inflammatory respiratory diseases clinically.

AIM OF THE STUDY

The present work aims to elucidate the therapeutic effects and the possible mechanism of TRQ against pulmonary fibrosis.

METHODS

The pulmonary fibrosis murine model were constructed by the intratracheal injection of bleomycin (BLM). 7 days later, TRQ-L (2.6 ml/kg) and TRQ-H (5.2 ml/kg) were administered via intraperitoneal injection respectively for 21 days. The efficacy and underlying molecular mechanism of TRQ were investigated.

RESULTS

Here, we showed that TRQ significantly inhibited BLM-induced lung edema and pulmonary function. TRQ markedly reduced BLM-promoted inflammatory cell infiltration in BALF and inflammatory cytokines release (TNF-α, IL-6, and IL-1β) in serum and lung tissues. Meanwhile, TRQ also alleviated BLM-induced collagen synthesis and deposition. Simultaneously, TRQ attenuated BLM-induced pulmonary fibrosis through regulating the expression of fibrotic hallmarks, manifested by down-regulated α-SMA and up-regulated E-cadherin. Moreover, we found that TRQ significantly prevented STING, p-P65, BIP, p-PERK, p-eIF2α, and ATF4 expression in lung fibrosis mice.

CONCLUSIONS

Taken together, our results indicated that TRQ positively affects inflammatory responses and lung fibrosis by regulating STING-mediated endoplasmic reticulum stress (ERS) signal pathway.

Magnetic Resonance Elastography (MRE) of Bleomycin-Induced Pulmonary Fibrosis in an Animal Model

BACKGROUND

Idiopathic pulmonary fibrosis is responsible for 40,000 deaths annually in the United States. A hallmark of idiopathic pulmonary fibrosis is elevated collagen deposition, which alters lung stiffness. Clinically relevant ways to measure changes in lung stiffness during pulmonary fibrosis are not available, and new noninvasive imaging methods are needed to measure changes in lung mechanical properties.

OBJECTIVES

Magnetic resonance elastography (MRE) is an in vivo magnetic resonance imaging technique proven to detect changes in shear stiffness in different organs. This study used MRE, histology, and bronchoalveolar lavage (BAL) to study changes in the mechanical and structural properties of the lungs after bleomycin-induced pulmonary fibrosis in pigs.

MATERIALS AND METHODS

Pulmonary fibrosis was induced in 9 Yorkshire pigs by intratracheal instillation of 2 doses of bleomycin into the right lung only. Magnetic resonance elastography scans were performed at baseline and week 4 and week 8 postsurgery in a 1.5 T magnetic resonance imaging scanner using a spin-echo echo planar imaging sequence to measure changes in lung shear stiffness. At the time of each scan, a BAL was performed. After the final scan, whole lung tissue was removed and analyzed for histological changes.

RESULTS

Mean MRE-derived stiffness measurements at baseline, week 4, and week 8 for the control (left) lungs were 1.02 ± 0.27 kPa, 0.86 ± 0.29 kPa, and 0.68 ± 0.20 kPa, respectively. The ratio of the shear stiffness in the injured (right) lung to the uninjured control (left) lung at baseline, week 4, and week 8 was 0.98 ± 0.23, 1.52 ± 0.41, and 1.64 ± 0.40, respectively. High-dose animals showed increased protein in BAL fluid, elevated inflammation observed by the presence of patchy filtrates, and enhanced collagen and α-smooth muscle actin staining on histological sections. Low-dose animals and the control (left) lungs of high-dose animals did not show significant histopathological changes.

CONCLUSION

This study demonstrated that MRE can be used to detect changes in lung stiffness in pigs after bleomycin challenge.

Chronic Expression of a Clinical SFTPC Mutation Causes Murine Lung Fibrosis with Idiopathic Pulmonary Fibrosis Features

Idiopathic pulmonary fibrosis (IPF) is a chronic progressive fibrotic interstitial lung disease. A barrier to developing more effective therapies for IPF is the dearth of preclinical models that recapitulate the early pathobiology of this disease. Intratracheal bleomycin, the conventional preclinical murine model of IPF, fails to reproduce the intrinsic dysfunction to the alveolar epithelial type 2 cell (AEC2) that is believed to be a proximal event in the pathogenesis of IPF. Murine fibrosis models based on SFTPC (Surfactant Protein C gene) mutations identified in patients with interstitial lung disease cause activation of the AEC2 unfolded protein response and endoplasmic reticulum stress-an AEC2 dysfunction phenotype observed in IPF. Although these models achieve spontaneous fibrosis, they do so with precedent lung injury and thus are challenged to phenocopy the general clinical course of patients with IPF-gradual progressive fibrosis and loss of lung function. Here, we report a refinement of a murine Sftpc mutation model to recapitulate the clinical course, physiological impairment, parenchymal cellular composition, and biomarkers associated with IPF. This platform provides the field with an innovative model to understand IPF pathogenesis and index preclinical therapeutic candidates.

Pulmonary fibrosis model of mice induced by different administration methods of bleomycin

BACKGROUND

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive disease of the lung. How to build a typical human mimicking animal model has been a challenge. Thus, to reveal the mechanism and to make it useful for IPF clinical treatment, a different type of mice model and inspection methods are used to evaluate which one is applicable for the study of IPF.

METHOD

69 Twelve-weeks-old C57BL/6 mice were divided into 3 type groups (n = 7 for each control group, n = 8 for each BLM-induced pulmonary fibrosis groups), as intraperitoneal injection, intratracheal administration, and intravenous administration of bleomycin (BLM) to initiate lung fibrosis. Changes of the lung function measured through mice Pulmonary function test (PFT). Morphological changes in mice were observed by PET/CT, Masson and Picro-Sirius staining, Transmission electron microscopy (TEM). Biochemical changes were tested by Enzyme-linked immunosorbent assay (Elisa).

RESULTS

PET/CT of BLM-receiving mice showed an increase in fibrotic consolidations and an increase in non-aerated lung area in BLM-treated mice compared with that in controls. TGF-b1, TNF-a, IL-6, GM-CSF in BALF and serum. PAI-1, HYP in the lung tissue of mice were significantly different in each BLM groups than those in the controls. The results of Masson staining in mice indicate that the lung tissues of all BLM received groups, the intratracheal groups, the intravenous groups, and the intraperitoneal groups have a higher degree of pulmonary septal thickening and collagen fiber consolidation compare to saline control. Picro-Sirius staining results are consistent with the results of Masson staining. Compared with the saline control group, the ratio of Col 1/Col 3 was significantly increased in each BLM group. TEM results found that in BLM group, type I alveolar epithelial cells were degenerated. Exfoliated endothelial cells were swelling, and type II alveolar epithelial cells were proliferated, the shape of the nucleus was irregular, and some tooth-like protrusions were seen.

CONCLUSIONS

With three different methods of animal model construction, high dose of each show more compliable, and BLM can successfully induce animal models of pulmonary fibrosis, however, certain differences in the fibrosis formation sites of them three, and tail vein injection of BLM induced PF model is closer to the idiopathic pulmonary interstitial fibrosis.

Basal Cell-derived WNT7A Promotes Fibrogenesis at the Fibrotic Niche in Idiopathic Pulmonary Fibrosis

Loss of epithelial integrity, bronchiolarization, and fibroblast activation are key characteristics of idiopathic pulmonary fibrosis (IPF). Prolonged accumulation of basal-like cells in IPF may impact the fibrotic niche to promote fibrogenesis. To investigate their role in IPF, basal cells were isolated from IPF explant and healthy donor lung tissues. Single-cell RNA sequencing was used to assess differentially expressed genes in basal cells. Basal cell and niche interaction was demonstrated with the sLP-mCherry niche labeling system. Luminex assays were used to assess cytokines secreted by basal cells. The role of basal cells in fibroblast activation was studied. Three-dimensional organoid culture assays were used to interrogate basal cell effects on AEC2 (type 2 alveolar epithelial cell) renewal capacity. Perturbation was used to investigate WNT7A function in vitro and in a repetitive bleomycin model in vivo. We found that WNT7A is highly and specifically expressed in basal-like cells. Proteins secreted by basal cells can be captured by neighboring fibroblasts and AEC2s. Basal cells or basal cell-conditioned media activate fibroblasts through WNT7A. Basal cell-derived WNT7A inhibits AEC2 progenitor cell renewal in three-dimensional organoid cultures. Neutralizing antibodies against WNT7A or a small molecule inhibitor of Frizzled signaling abolished basal cell-induced fibroblast activation and attenuated lung fibrosis in mice. In summary, basal cells and basal cell-derived WNT7A are key components of the fibrotic niche, providing a unique non-stem cell function of basal cells in IPF progression and a novel targeting strategy for IPF.

Effects of short-term high-concentration exposure to PM2.5 on pulmonary tissue damage and repair ability as well as innate immune events

Short-term heavy air pollution still occurs frequently worldwide, especially during the winter heating period in some developing countries, which is usually accompanied by the temporary explosive growth of PM_2.5. The pulmonary damage caused by PM_2.5 exposure has been determined, but there have been few studies on the repair ability after the cessation of exposure and the important role of innate immune events. This study established a short-term (30 days) high-concentration (15 mg/kg body weight) PM_2.5 exposure and recovery (15 days of exposure cessation) model by intratracheal instillation. The results showed that short-term PM_2.5 exposure increased the content of collagen fiber in rat lung tissue, which was significantly repaired after recovery by 15 days of exposure cessation. Meanwhile, exposure to PM_2.5 also caused changes in lung epithelial function, macrophage polarization and cell autophagy function. Most of these changes could be restored or reversed to a certain extent after recovery. However, there were also some biomarkers, including CLDN18.1, SP-A, SP-D, iNOS, CD206, Beclin1, p62 and LC3B, that were still significantly different between the exposure and control groups after recovery, suggesting that some toxic effects, especially epithelial function damage, were not completely repaired. In addition, there was a significant correlation between pulmonary fibrosis and innate immunity. The present study demonstrated that short-term high-concentration exposure to PM_2.5 could cause temporary lung tissue damage and related innate immune events in rats, and the repair ability existed after the cessation of exposure, but part of the damage that required special attention still persisted.

Genomic Fingerprint Associated with Familial Idiopathic Pulmonary Fibrosis: A Review

Idiopathic pulmonary fibrosis (IPF) is a severe interstitial lung disease; although the recent introduction of two anti-fibrosis drugs, pirfenidone and Nidanib, have resulted in a significant reduction in lung function decline, IPF is still not curable. Approximately 2-20% of patients with IPF have a family history of the disease, which is considered the strongest risk factor for idiopathic interstitial pneumonia. However, the genetic predispositions of familial IPF (f-IPF), a particular type of IPF, remain largely unknown. Genetics affect the susceptibility and progression of f-IPF. Genomic markers are increasingly being recognized for their contribution to disease prognosis and drug therapy outcomes. Existing data suggest that genomics may help identify individuals at risk for f-IPF, accurately classify patients, elucidate key pathways involved in disease pathogenesis, and ultimately develop more effective targeted therapies. Since several genetic variants associated with the disease have been found in f-IPF, this review systematically summarizes the latest progress in the gene spectrum of the f-IPF population and the underlying mechanisms of f-IPF. The genetic susceptibility variation related to the disease phenotype is also illustrated. This review aims to improve the understanding of the IPF pathogenesis and facilitate his early detection.

L-carnosine Attenuates Bleomycin-Induced Oxidative Stress via NFκB Pathway in the Pathogenesis of Pulmonary Fibrosis

Idiopathic Pulmonary fibrosis (IPF), a chronic interstitial lung disease, has pulmonary manifestations clinically characterized by collagen deposition, epithelial cell injury, and a decline in lung function. L-carnosine, a dipeptide consisting of β-alanine and L-histidine, has demonstrated a therapeutic effect on various diseases because of its pivotal function. Despite the effect of L-carnosine in experimental IPF mice, its anti-oxidative effect and associated intercellular pathway, particularly alveolar epithelial cells, remain unknown. Therefore, we demonstrated the anti-fibrotic and anti-inflammatory effects of L-carnosine via Reactive oxygen species (ROS) regulation in bleomycin (BLM)-induced IPF mice. The mice were intratracheally injected with BLM (3 mg/kg) and L-carnosine (150 mg/kg) was orally administrated for 2 weeks. BLM exposure increased the protein level of Nox2, Nox4, p53, and Caspase-3, whereas L-carnosine treatment suppressed the protein level of Nox2, Nox4, p53, and Caspase-3 cleavage in mice. In addition, the total SOD activity and mRNA level of Sod2, catalase, and Nqo1 increased in mice treated with L-carnosine. At the cellular level, a human fibroblast (MRC-5) and mouse alveolar epithelial cell (MLE-12) were exposed to TGFβ1 following L-carnosine treatment to induce fibrogenesis. Moreover, MLE-12 cells were exposed to cigarette smoke extract (CSE). Consequently, L-carnosine treatment ameliorated fibrogenesis in fibroblasts and alveolar epithelial cells, and inflammation induced by ROS and CSE exposure was ameliorated. These results were associated with the inhibition of the NFκB pathway. Collectively, our data indicate that L-carnosine induces anti-inflammatory and anti-fibrotic effects on alveolar epithelial cells against the pathogenesis of IPF.

Pulmonary Fibrosis as a Result of Acute Lung Inflammation: Molecular Mechanisms, Relevant In Vivo Models, Prognostic and Therapeutic Approaches

Pulmonary fibrosis is a chronic progressive lung disease that steadily leads to lung architecture disruption and respiratory failure. The development of pulmonary fibrosis is mostly the result of previous acute lung inflammation, caused by a wide variety of etiological factors, not resolved over time and causing the deposition of fibrotic tissue in the lungs. Despite a long history of study and good coverage of the problem in the scientific literature, the effective therapeutic approaches for pulmonary fibrosis treatment are currently lacking. Thus, the study of the molecular mechanisms underlying the transition from acute lung inflammation to pulmonary fibrosis, and the search for new molecular markers and promising therapeutic targets to prevent pulmonary fibrosis development, remain highly relevant tasks. This review focuses on the etiology, pathogenesis, morphological characteristics and outcomes of acute lung inflammation as a precursor of pulmonary fibrosis; the pathomorphological changes in the lungs during fibrosis development; the known molecular mechanisms and key players of the signaling pathways mediating acute lung inflammation and pulmonary fibrosis, as well as the characteristics of the most common in vivo models of these processes. Moreover, the prognostic markers of acute lung injury severity and pulmonary fibrosis development as well as approved and potential therapeutic approaches suppressing the transition from acute lung inflammation to fibrosis are discussed.

Therapeutic effect of adipose-derived mesenchymal stem cells (AD-MSCs) compared to pirfenidone on corticosteroid resistance in a mouse model of acute exacerbation of idiopathic pulmonary fibrosis

INTRODUCTION

Acute exacerbation-idiopathic pulmonary fibrosis (AE-IPF) is a life-threatening condition. In the treatment of AE-IPF, corticosteroid medication is commonly utilized. However, there is insufficient evidence to justify its usage. Pirfenidone (PFD) has recently been discovered to be effective in the treatment of AE-IPF patients. However, regenerative therapy, such as stem cell therapy or tissue engineering, is necessary due to ineffective and limited therapies. Combining MSC transplantation with pharmacological therapy may also give additional benefits; nevertheless, its use must be proven experimentally. As a result, the goal of this study was to assess the therapeutic effects of adipose-derived mesenchymal stem cells (AD-MSCs) on corticosteroid resistance in an animal model of AE-IPF caused by bleomycin compared to PFD.

MATERIALS AND METHODS

Seventy C57BL/6J male mice were randomly divided into seven groups, control, BLM, methylprednisolone (MP), PFD, AD-MSCs, PFD +MP, and AD-MSCs +MP.

RESULTS

In terms of survival, collagen deposition, the acute lung injury score (ALI), and the Ashcroft score, AD-MSCs exceeded PFD. AD-MSCs + MP provided protection and preserved the lung's architecture in BLM-induced AE. In addition, AD-MSCs successfully decreased chemokine (CC motif) ligand-2 (CCL2) positive cells and lower pro-fibrotic and pro-inflammatory cytokines.

CONCLUSIONS

AD-MSCs enhanced histological structure, Ashcroft and ALI scores, lung collagen deposition, survival, and cytokines in an animal model of AE-IPF. As a result, we believe that AD-MSCs may be more therapeutically helpful for AE-IPF than presently available therapies, either alone or in conjunction with MP.

A novel therapeutic approach for IPF: Based on the "Autophagy - Apoptosis" balance regulation of Zukamu Granules in alveolar macrophages

ETHNOPHARMACOLOGICAL RELEVANCE

Zukamu Granules (ZKMG) is one of the representative Uygur patent drugs widely used in China, which is included in the National Essential Drugs List (2018 edition). As the first choice for common cold treatment in Uygur medicine theory, it has unique anti-inflammatory and antitussive efficacy.

AIM OF THE STUDY

According to the recent inflammatory hypothesis, the abnormal proliferation, autophagy and apoptosis process of lung cells especially alveolar macrophages (AMs) may play an important role in the progress of idiopathic pulmonary fibrosis (IPF). Therefore, we came up with a novel treatment approach for IPF by regulating the balance of AMs "autophagy - apoptosis", and took ZKMG as the sample drug for our research.

MATERIALS AND METHODS

Network pharmacology approach was conducted to predict the active components and intersected targets between ZKMG and inflammation. PPI network, GO and KEGG enrichment analysis were screened and analyzed to predict the anti-inflammatory mechanism of ZKMG. Biological experiment adopted from 128 rats, and hematoxylin-eosin staining, flow cytometry and RT-PCR were performed to examine the pathological morphology, HYP contents in lung tissue, AMs counting, AMs apoptosis, AMs phagocytosis rate, mRNA relative quantity determination of 3 key factors associated with AMs "autophagy - apoptosis" and mRNA relative quantity determination of AMs surface receptor signaling pathway.

RESULTS

The predicted results showed that the mechanism of ZKMG in anti-inflammatory was related to the response and elimination of inflammatory stimuli, the intervention of apoptosis and surface receptor signaling pathways of cells. The verification experiments showed that excessive apoptosis and insufficient autophagy of AMs always existed in the progression of IPF. ZKMG could inhibit AMs proliferation, significantly reduce AMs apoptosis rate, intervene the binding of the Bcl-2 to Beclin 1, inhibit the Caspase 3 activation, stimulate the enhancement of AMs phagocytosis, and inhibit the high expression of TLR4/MyD88/NF-κB surface receptor signaling pathway, which may partly retard the fibrosis process.

CONCLUSION

By inhibiting proliferation, enhancing phagocytosis, inhibiting the formation of Bcl-2 complex, and inhibiting the high expression of MYD88-dependent TLR4 signaling pathway, ZKMG can regulate the balance of AMs "autophagy - apoptosis" in the alveolitis stage to retard the fibrosis process partly. With a comprehensive strategy of "target prediction - experimental verification", we have demonstrated that inhibiting the apoptosis and promoting autophagy activity of AMs may suggest a new perspective for IPF treatment, which would provide reference for the subsequent development.

A New Model of Acute Exacerbation of Experimental Pulmonary Fibrosis in Mice

RATIONALE

idiopathic pulmonary fibrosis (IPF) is the most severe form of fibrosing interstitial lung disease, characterized by progressive respiratory failure leading to death. IPF's natural history is heterogeneous, and its progression unpredictable. Most patients develop a progressive decline of respiratory function over years; some remain stable, but others present a fast-respiratory deterioration without identifiable cause, classified as acute exacerbation (AE).

OBJECTIVES

to develop and characterize an experimental mice model of lung fibrosis AE, mimicking IPF-AE at the functional, histopathological, cellular and molecular levels.

METHODS

we established in C57BL/6 male mice a chronic pulmonary fibrosis using a repetitive low-dose bleomycin (BLM) intratracheal (IT) instillation regimen (four instillations of BLM every 2 weeks), followed by two IT instillations of a simple or double-dose BLM challenge to induce AE. Clinical follow-up and histological and molecular analyses were done for fibrotic and inflammatory lung remodeling analysis.

MEASUREMENTS AND MAIN RESULTS

as compared with a low-dose BLM regimen, this AE model induced a late burst of animal mortality, worsened lung fibrosis and remodeling, and superadded histopathological features as observed in humans IPF-AE. This was associated with stronger inflammation, increased macrophage infiltration of lung tissue and increased levels of pro-inflammatory cytokines in lung homogenates. Finally, it induced in the remodeled lung a diffuse expression of hypoxia-inducible factor 1α, a hallmark of tissular hypoxia response and a major player in the progression of IPF.

CONCLUSION

this new model is a promising model of AE in chronic pulmonary fibrosis that could be relevant to mimic IPF-AE in preclinical trials.

Molecular Regulation of Heme Oxygenase-1 Expression by E2F Transcription Factor 2 in Lung Fibroblast Cells: Relevance to Idiopathic Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is a fatal chronic lung disease. Heme oxygenase-1 (HMOX1/HO-1) is an enzyme that catalyzes the degradation of heme. The role of HO-1 in the pathogenesis of IPF has been studied; however, the molecular regulation of HO-1 and its role in IPF are still unclear. In this study, we found that HO-1 protein levels significantly increased in lung myofibroblasts in IPF patients and in lungs in a murine model of bleomycin-induced lung fibrosis. In addition, we observed that administration of a E2F transcription factor inhibitor elevated HO-1 mRNA and protein levels in lung fibroblasts. Downregulation of E2F2 by siRNA transfection increased HO-1 mRNA and protein levels, while overexpression of E2F2 reduced HO-1 levels. However, overexpression of E2F2 did not alter hemin-induced HO-1 protein levels. Furthermore, modulation of HO-1 levels regulated TGF-β1-induced myofibroblast differentiation without altering the phosphorylation of Smad2/3 in lung fibroblast cells. Moreover, the phosphorylation of protein kinase B (Akt) was significantly upregulated in HO-1-depleted lung fibroblast cells. In summary, this study demonstrated that E2F2 regulates the baseline expression of HO-1, but has no effect on modulating HO-1 expression by hemin. Finally, elevated HO-1 expression contributes to the TGF-β1-induced lung myofibroblast differentiation through the activation of the serine/threonine kinase AKT pathway. Overall, our findings suggest that targeting E2F2/HO-1 might be a new therapeutic strategy to treat fibrotic diseases such as IPF.

Sandwich therapy in the management of propranolol resistant infantile hemangioma of the lip

RATIONALE

Propranolol has evolved as a first line management of infantile haemangiomas. Nevertheless, the resistance to propranolol has warranted alternative treatment modalities. We hypothesize that combination of medical and surgical therapy (sandwich therapy) to be beneficial in the management.

METHODS

Patients were divided into three groups (total=31), Group A (bleomycin sclerotherapy), Group B (surgical group), Group C (sandwich therapy). A p value <0.05 was taken as significant.

RESULTS

In Group A 54.5% of patients had excellent response, 27.3% partial response and 18.2% had no response. Comparing cosmetic outcome, 25% of patients in Group B and 16.7% of patients in Group C had excellent upshot. On the contrary 18.2% of patients in bleomycin had unsatisfactory and 18.2% had poor cosmetic outcome. Sandwich therapy was cosmetically more acceptable than Bleomycin sclerotherapy (p- value = 0.049). In terms of recurrence, sandwich therapy differed significantly from surgical therapy with fewer recurrences (p-value= 0.049).

CONCLUSION

Sandwich therapy is superior to bleomycin sclerotherapy in terms of cosmetic outcome and has fewer recurrences compared to surgical group and requires single stage resection. However, further studies with the help of Doppler ultrasound are required in this regard.

IL-37 protects against airway remodeling by reversing bronchial epithelial-mesenchymal transition via IL-24 signaling pathway in chronic asthma

BACKGROUND

Epithelial-mesenchymal transition (EMT) is one of the mechanisms of airway remodeling in chronic asthma. Interleukin (IL)-24 has been implicated in the promotion of tissue fibrosis, and increased IL-24 levels have been observed in the nasal secretions and sputum of asthmatic patients. However, the role of IL-24 in asthmatic airway remodeling, especially in EMT, remains largely unknown. We aimed to explore the effect and mechanism of IL-24 on EMT and to verify whether IL-37 could alleviate IL-24-induced EMT in chronic asthma.

METHODS

BEAS-2B cells were exposed to IL-24, and cell migration was assessed by wound healing and Transwell assays. The expression of EMT-related biomarkers (E-cadherin, vimentin, and α-SMA) was evaluated after the cells were stimulated with IL-24 with or without IL-37. A murine asthma model was established by intranasal administration of house dust mite (HDM) extracts for 5 weeks, and the effects of IL-24 and IL-37 on EMT and airway remodeling were investigated by intranasal administration of si-IL-24 and rhIL-37.

RESULTS

We observed that IL-24 significantly enhanced the migration of BEAS-2B cells in vitro. IL-24 promoted the expression of the EMT biomarkers vimentin and α-SMA via the STAT3 and ERK1/2 pathways. In addition, we found that IL-37 partially reversed IL-24-induced EMT in BEAS-2B cells by blocking the ERK1/2 and STAT3 pathways. Similarly, the in vivo results showed that IL-24 was overexpressed in the airway epithelium of an HDM-induced chronic asthma model, and IL-24 silencing or IL-37 treatment could reverse EMT biomarker expression.

CONCLUSIONS

Overall, these findings indicated that IL-37 mitigated HDM-induced airway remodeling by inhibiting IL-24-mediated EMT via the ERK1/2 and STAT3 pathways, thereby providing experimental evidence for IL-24 as a novel therapeutic target and IL-37 as a promising agent for treating severe asthma.

Effectiveness and mechanism of metformin in animal models of pulmonary fibrosis: A preclinical systematic review and meta-analysis

Background: Pulmonary fibrosis (PF) is a lung disease with no curative drug, characterized by a progressive decrease in lung function. Metformin (MET) is a hypoglycemic agent with the advantages of high safety and low cost and has been used in several in vivo trials to treat fibrotic diseases.

Objective: This study aimed to explore the efficacy and safety of MET in treating PF and elaborate on its mechanism.

Methods: Eight databases were searched for in vivo animal trials of MET for PF from the time of database creation until 1 March 2022. The risk of bias quality assessment of the included studies was conducted using SYRCLE’s risk of bias assessment. Pulmonary inflammation and fibrosis scores were the primary outcomes of this study. Hydroxyproline (HYP), type I collagen (collagen I), α-smooth muscle actin (α-SMA), transforming growth factor-β (TGF-β), Smad, AMP-activated protein kinase (AMPK), and extracellular signal–regulated kinase (ERK) protein expression in lung tissues and animal mortality were secondary outcomes. Effect magnitudes were combined and calculated using Revman 5.3 and Stata 16.0 to assess the efficacy and safety of MET in animal models of PF. Inter-study heterogeneity was examined using the I² or Q test, and publication bias was assessed using funnel plots and Egger’s test.

Results: A total of 19 studies involving 368 animals were included, with a mean risk of bias of 5.9. The meta-analysis showed that MET significantly suppressed the level of inflammation and degree of PF in the lung tissue of the PF animal model. MET also reduced the content of HYP, collagen I, α-SMA, and TGF-β and phosphorylation levels of Smad2, Smad3, p-smad2/3/smad2/3, ERK1/2, and p-ERK1/2/ERK1/2 in lung tissues. MET also elevated AMPK/p-AMPK levels in lung tissues and significantly reduced animal mortality.

Conclusion: The results of this study suggest that MET has a protective effect on lung tissues in PF animal models and may be a potential therapeutic candidate for PF treatment.

Systematic Review Registration:https://www.crd.york.ac.uk/PROSPERO/display_record.php?RecordID=327285, identifier CRD42022327285.

Promises and Challenges of Cell-Based Therapies to Promote Lung Regeneration in Idiopathic Pulmonary Fibrosis

The lung epithelium is constantly exposed to harmful agents present in the air that we breathe making it highly susceptible to damage. However, in instances of injury to the lung, it exhibits a remarkable capacity to regenerate injured tissue thanks to the presence of distinct stem and progenitor cell populations along the airway and alveolar epithelium. Mechanisms of repair are affected in chronic lung diseases such as idiopathic pulmonary fibrosis (IPF), a progressive life-threatening disorder characterized by the loss of alveolar structures, wherein excessive deposition of extracellular matrix components cause the distortion of tissue architecture that limits lung function and impairs tissue repair. Here, we review the most recent findings of a study of epithelial cells with progenitor behavior that contribute to tissue repair as well as the mechanisms involved in mouse and human lung regeneration. In addition, we describe therapeutic strategies to promote or induce lung regeneration and the cell-based strategies tested in clinical trials for the treatment of IPF. Finally, we discuss the challenges, concerns and limitations of applying these therapies of cell transplantation in IPF patients. Further research is still required to develop successful strategies focused on cell-based therapies to promote lung regeneration to restore lung architecture and function.

Interleukin-6-dependent epithelial fluidization initiates fibrotic lung remodeling

Chronic disease results from the failure of tissues to maintain homeostasis. In the lung, coordinated repair of the epithelium is essential for preserving homeostasis. In animal models and human lung disease, airway epithelial cells mobilize in response to lung injury, resulting in the formation of airway-like cysts with persistent loss of functional cell types and parenchymal architecture. Using live-cell imaging of human lung epithelial cultures and mouse precision-cut lung slices, we demonstrated that distal airway epithelia are aberrantly fluidized both after injury and in fibrotic lung disease. Through transcriptomic profiling and pharmacologic stimulation of epithelial cultures, we identified interleukin-6 (IL-6) signaling as a driver of tissue fluidization. This signaling cascade occurred independently of canonical Janus kinase (JAK)-signal transducer and activator of transcription (STAT) signaling but instead was dependent on a downstream SRC family kinase (SFK)-yes-associated protein (YAP) axis. Airway epithelial-fibroblast cocultures revealed that the fibrotic mesenchyme acts as a source of IL-6 family cytokines, which drive airway fluidization. Inhibition of the IL-6-SFK-YAP cascade was sufficient to prevent fluidization in both in vitro and ex vivo models. Last, we demonstrated a reduction in fibrotic lung remodeling in mice through genetic or pharmacologic targeting of IL-6-related signaling. Together, our findings illustrate the critical role of airway epithelial fluidization in coordinating the balance between homeostatic lung repair and fibrotic airspace remodeling.

Animal Models of Systemic Sclerosis: Using Nailfold Capillaroscopy as a Potential Tool to Evaluate Microcirculation and Microangiopathy: A Narrative Review

Systemic sclerosis (SSc) is an autoimmune disease with three pathogenic hallmarks, i.e., inflammation, vasculopathy, and fibrosis. A wide plethora of animal models have been developed to address the complex pathophysiology and for the development of possible anti-fibrotic treatments. However, no current model comprises all three pathological mechanisms of the disease. To highlight the lack of a complete model, a review of some of the most widely used animal models for SSc was performed. In addition, to date, no model has accomplished the recreation of primary or secondary Raynaud’s phenomenon, a key feature in SSc. In humans, nailfold capillaroscopy (NFC) has been used to evaluate secondary Raynaud’s phenomenon and microvasculature changes in SSc. Being a non-invasive technique, it is widely used both in clinical studies and as a tool for clinical evaluation. Because of this, its potential use in animal models has been neglected. We evaluated NFC in guinea pigs to investigate the possibility of applying this technique to study microcirculation in the nailfold of animal models and in the future, development of an animal model for Raynaud’s phenomenon. The applications are not only to elucidate the pathophysiological mechanisms of vasculopathy but can also be used in the development of novel treatment options.