Surfactant Protein C Research Articles

Lung and liver editing by lipid nanoparticle delivery of a stable CRISPR-Cas9 ribonucleoprotein.

Lipid nanoparticle (LNP) delivery of clustered regularly interspaced short palindromic repeat (CRISPR) ribonucleoproteins (RNPs) could enable high-efficiency, low-toxicity and scalable in vivo genome editing if efficacious RNP-LNP complexes can be reliably produced. Here we engineer a thermostable Cas9 from Geobacillus stearothermophilus (GeoCas9) to generate iGeoCas9 variants capable of >100× more genome editing of cells and organs compared with the native GeoCas9 enzyme. Furthermore, iGeoCas9 RNP-LNP complexes edit a variety of cell types and induce homology-directed repair in cells receiving codelivered single-stranded DNA templates. Using tissue-selective LNP formulations, we observe genome-editing levels of 16‒37% in the liver and lungs of reporter mice that receive single intravenous injections of iGeoCas9 RNP-LNPs. In addition, iGeoCas9 RNPs complexed to biodegradable LNPs edit the disease-causing SFTPC gene in lung tissue with 19% average efficiency, representing a major improvement over genome-editing levels observed previously using viral or nonviral delivery strategies. These results show that thermostable Cas9 RNP-LNP complexes can expand the therapeutic potential of genome editing.

Generation of SFTPC-MCHERRY knock-in reporter human embryonic stem cell line, WAe001-A-2H, using CRISPR/Cas9-based gene targeting

The SFTPC gene is responsible for the production of the pulmonary surfactant protein C (SPC), a highly hydrophobic molecule that plays a crucial role in maintaining lung integrity through its influence on the synthesis of alveolar surfactant proteins. In this study, we harnessed the CRISPR/Cas9 system for precise genome editing to create a modified H1 human embryonic stem cell (hESC) line, incorporating the SFTPC-mCherry reporter construct. Therefore, the engineered SFTPC-mCherry knock-in (KI) hESC line can serve as an effective tool for tracking the expression patterns of the SFTPC gene as alveolar type 2 cells differentiate from hESCs

Airway derived emphysema-specific alveolar type II cells exhibit impaired regenerative potential in COPD.

Emphysema, the progressive destruction of gas exchange surfaces in the lungs, is a hallmark of chronic obstructive pulmonary disease (COPD) that is presently incurable. This therapeutic gap is largely due to a poor understanding of potential drivers of impaired tissue regeneration, such as abnormal lung epithelial progenitor cells, including alveolar type II (ATII) and airway club cells. We discovered an emphysema-specific sub-population of ATII cells located in enlarged distal alveolar sacs, termed asATII cells. Single cell RNA-seq and in situ localisation revealed that asATII cells co-express the alveolar marker surfactant protein C (SPC) and the club cell marker secretaglobin-3A2 (SCGB3A2). A similar ATII sub-population derived from club cells was also identified in mouse COPD models using lineage labeling. Human and mouse ATII sub-populations formed 80-90% fewer alveolar organoids than healthy controls, indicating reduced progenitor function. Targeting asATII cells or their progenitor club cells could reveal novel COPD treatment strategies.

Humanized L184Q Mutated Surfactant Protein C Gene Alters Alveolar Type 2 Epithelial Cell Fate.

Alveolar type 2 epithelial (AT2) cells synthesize surfactant protein C (SPC) and repair an injured alveolar epithelium. A mutated surfactant protein C gene (SftpcL184Q, Gene ID: 6440) in newborns has been associated with respiratory distress syndrome and pulmonary fibrosis. However, the underlying mechanisms causing Sftpc gene mutations to regulate AT2 lineage remain unclear. We utilized three-dimensional (3D) feeder-free AT2 organoids in vitro to simulate the alveolar epithelium and compared AT2 lineage characteristics between WT (C57BL/6) and SftpcL184Q mutant mice using colony formation assays, immunofluorescence, flow cytometry, qRT-PCR, and Western blot assays. The AT2 numbers were reduced significantly in SftpcL184Q mice. Organoid numbers and colony-forming efficiency were significantly attenuated in the 3D cultures of primary SftpcL184Q AT2 cells compared to those of WT mice. Podoplanin (PDPN, Alveolar type 1 cell (AT1) marker) expression and transient cell count was significantly increased in SftpcL184Q organoids compared to in the WT mice. The expression levels of CD74, heat shock protein 90 (HSP90), and ribosomal protein S3A1 (RPS3A1) were not significantly different between WT and SftpcL184Q AT2 cells. This study demonstrated that humanized SftpcL184Q mutation regulates AT2 lineage intrinsically. This regulation is independent of CD74, HSP90, and RPS3A1 pathways.

Role and mechanism of epithelial-mesenchymal transition in a rat model of bronchopulmonary dysplasia induced by hyperoxia exposure

To investigate the role and mechanism of epithelial-mesenchymal transition (EMT) in a rat model of bronchopulmonary dysplasia (BPD). The experiment consisted of two parts. (1) Forty-eight preterm rats were randomly divided into a normoxia group and a hyperoxia group, with 24 rats in each group. The hyperoxia group was exposed to 85% oxygen to establish a BPD model, while the normoxia group was kept in room air at normal pressure. Lung tissue samples were collected on days 1, 4, 7, and 14 of the experiment. (2) Rat type II alveolar epithelial cells (RLE-6TN) were randomly divided into a normoxia group (cultured in air) and a hyperoxia group (cultured in 95% oxygen), and cell samples were collected 12, 24, and 48 hours after hyperoxia exposure. Hematoxylin-eosin staining was used to observe alveolarization in preterm rat lungs, and immunofluorescence was used to detect the co-localization of surfactant protein C (SPC) and α-smooth muscle actin (α-SMA) in preterm rat lung tissue and RLE-6TN cells. Quantitative real-time polymerase chain reaction and protein immunoblotting were used to detect the expression levels of EMT-related mRNA and proteins in preterm rat lung tissue and RLE-6TN cells. (1) Compared with the normoxia group, the hyperoxia group showed blocked alveolarization and simplified alveolar structure after 7 days of hyperoxia exposure. Co-localization of SPC and α-SMA was observed in lung tissue, with decreased SPC expression and increased α-SMA expression in the hyperoxia group at 7 and 14 days of hyperoxia exposure compared to the normoxia group. In the hyperoxia group, the mRNA and protein levels of TGF-β1, α-SMA, and N-cadherin were increased, while the mRNA and protein levels of SPC and E-cadherin were decreased at 7 and 14 days of hyperoxia exposure compared to the normoxia group (P<0.05). (2) SPC and α-SMA was observed in RLE-6TN cells, with decreased SPC expression and increased α-SMA expression in the hyperoxia group at 24 and 48 hours of hyperoxia exposure compared to the normoxia group. Compared to the normoxia group, the mRNA and protein levels of SPC and E-cadherin in the hyperoxia group were decreased, while the mRNA and protein levels of TGF-β1, α-SMA, and E-cadherin in the hyperoxia group increased at 48 hours of hyperoxia exposure (P<0.05). EMT disrupts the tight connections between alveolar epithelial cells in a preterm rat model of BPD, leading to simplified alveolar structure and abnormal development, and is involved in the development of BPD. Citation:Chinese Journal of Contemporary Pediatrics, 2024, 26(7): 765-773.

PC (16:0/14:0) ameliorates hyperoxia-induced bronchopulmonary dysplasia by upregulating claudin-1 and promoting alveolar type II cell repair

Bronchopulmonary dysplasia (BPD) remains a significant challenge in neonatal care, the pathogenesis of which potentially involves altered lipid metabolism. Given the critical role of lipids in lung development and the injury response, we hypothesized that specific lipid species could serve as therapeutic agents in BPD. This study aimed to investigate the role of the lipid Phosphatidylcholine (PC) (16:0/14:0) in modulating BPD pathology and to elucidate its underlying mechanisms of action. Our approach integrated in vitro and in vivo methodologies to assess the effects of PC (16:0/14:0) on the histopathology, cellular proliferation, apoptosis, and molecular markers in lung tissue. In a hyperoxia-induced BPD rat model, we observed a reduction in alveolar number and an enlargement in alveolar size, which were ameliorated by PC (16:0/14:0) treatment. Correspondingly, in BPD cell models, PC (16:0/14:0) intervention led to increased cell viability, enhanced proliferation, reduced apoptosis, and elevated surfactant protein C (SPC) expression. RNA sequencing revealed significant gene expression differences between BPD and PC (16:0/14:0) treated groups, with a particular focus on Cldn1 (encoding claudin 1), which was significantly enriched in our analysis. Our findings suggest that PC (16:0/14:0) might protect against hyperoxia-induced alveolar type II cell damage by upregulating CLDN1 expression, potentially serving as a novel therapeutic target for BPD. This study not only advances our understanding of the role of lipids in BPD pathogenesis, but also highlights the significance of PC (16:0/14:0) in the prevention and treatment of BPD, offering new avenues for future research and therapeutic development.

Activating Transcription Factor 6 (ATF6) Acts as a Rheostat To Balance UPR Signaling and The Proteostatic Response To Mutant SFTPC Substrates By The Alveolar Epithelium

The alveolar type II (AT2) epithelial cell is a metabolically active, biosynthetically robust component of the distal lung responsible for the synthesis of pulmonary surfactant. Disruption of AT2 cell quality control provides a molecular signature found in Idiopathic Pulmonary Fibrosis (IPF), a progressive interstitial lung disease. Mutations in the surfactant protein C (SP-C) gene ( SFTPC) are a high effect size etiological cause of PF in a subset of these patients. Prior in vitro studies from our lab showed that mutations located within the SFTPC BRICHOS domain of the SP-C proprotein result in production of ER retained and aggregation prone conformers. Two critical aspects of the proteostasis network are ER Associated Degradation (ERAD) and the unfolded protein response (UPR). Misfolded conformers activate the UPR via one or more of 3 ER transmembrane sensing proteins (Protein kinase R-like ER kinase (PERK), the Inositol-Requiring kinase 1 alpha (IRE1α) and Activating Transcription Factor 6 (ATF6). We have shown in vitro and in mouse models that clinical IPF associated BRICHOS SFTPC conformers produce unbalanced, exuberant UPR signaling and AT2 dysfunction. The goal of this study was to probe AT2 proteostatic repertoires using BRICHOS SFTPC mutants as substrates. For this, we generated stable doxycycline-inducible Mouse Lung Epithelial (MLE-12) cell lines expressing either Wild Type (SP-CWT) or an aggregating mutant (SP-CC121G) which were interrogated using cycloheximide chase and / or treatments with activators or inhibitors of ATF6, IRE1, and PERK as well as ERAD (VCP/p97), the proteasome, or macroautophagy. Readouts included fluorescence microscopy, qPCR, luciferase reporters, and immunoblotting to assess SFPTC aggregate formation, UPR signaling, and downstream ER stress related events. Using this model system, we found that SP-CC121G was ER retained and activated the UPR within 8 hours of Dox induction (as BIP expression). Commensurate with this, IRE1α (as p-IREα and spliced XBP1 (sXBP1)), ATF6 (by luciferase assay), and PERK (as p-Eif2α, ATF4, CHOP) signals were activated by SP-CC121G. The clearance of mutant SP-CC121G as well as a portion of proSP-CWT was dependent on ERAD and the Ubiquitin-Proteasome System (UPS) as their disruption using either inhibitors of p97 (EEY) or the proteasome (MG132) induced formation of higher molecular weight aggregates. Bafilomycin failed to induce SP-CC121G aggregates or block their clearance. The ATF6 agonist AA147 administered during ERAD inhibition accelerated aggregate protein degradation. When SP-CC121G MLE12 cells were treated with an ATF6 inhibitor (CEAPIN7), we observed marked increases in IRE1α kinase activity with downstream activation of JNK accompanied by commensurate activation of PERK signals and initiation of caspase-3 cleavage. Collectively, these data demonstrate a primary role for ERAD in the AT2 proteostatic response to mutant SFTPC substrates and identify ATF6 as a critical UPR rheostat to provide protection from SFTPC mutant expression both by limiting SP-C aggregate formation and balancing exuberant UPR signals from IRE1α and PERK. NIH R01 HL145408 (MFB), VA Merit Review 2I01BX001176-09 (MFB), Pulmonary Fibrosis Foundation (LRR), NIH 2T32 HL007586-36 (SB), NIH K08 HL150226 (JBK). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Abstract 4294: The emerging role of deubiquitinase enzymes in lung cancer plasticity

Abstract Lung cancer is characterized by a high degree of genetic and molecular heterogeneity. Lineage plasticity has emerged as a source of intratumoral heterogeneity and drug resistance, resulting in poor prognosis and treatment failure. The molecular mechanisms driving lung cancer plasticity remain unclear. Ubiquitin-Specific Peptidase 13 (USP13), a deubiquitinating enzyme, is one of the most amplified genes in lung squamous cell carcinoma (LUSC). We developed a USP13 knock-in overexpressing mouse model in KrasLSL-G12D/+; Trp53fl/fl (KP) background (KPU mice). USP13 overexpression resulted in aggressive tumorigenesis and a shortened survival in Kras/Trp53-driven lung cancer. Notably, while KP mice developed lung adenocarcinoma (LUAD), KPU mice developed LUSC and LUAD. LUSC in KPU mice faithfully recapitulated the key pathohistological, molecular features, and cellular pathways of human LUSC. Bulk RNA-sequencing analysis showed that KPU tumors were heterogeneous and enriched in lineage reprogramming pathways including basal cell signaling, stem cell pluripotency, and epithelial-mesenchymal transition (EMT). Using cell-type-restricted adenoviral Cre to target cells expressing surfactant protein C (SPC) or club cell antigen 10 (CC10), we identified bronchiolar secretory club cells as the predominant cell origin of LUSC. USP13 altered the levels of lineage transcription factors such as TTF-1 and SOX2 in club cells during early tumorigenesis. Altered expression of these factors reinforced the fate of CC10+ club cells to squamous carcinoma development rather than adenocarcinoma. In addition, USP13 directly acted on the K48-linked ubiquitination of c-Myc and increased its protein stability, contributing to the elevation of squamous gene expression (SOX2, CK5, P40) in the primary mouse and advanced human lung cancer cells. These results suggest that USP13 promotes lineage plasticity in club cells during the early stage of cancer development and drives reprogramming into LUSC. We also found a potential functional association between USP13 and EMT pathway. Notably, irrespective of cell origin, USP13 overexpression enhanced EMT marker expression including N-cadherin, SNAI1, and ZEB1 in lung cancer cells, promoting cell migration and invasion. USP13 increased tumorigenic and metastatic abilities of lung cancer cells in 3D organoid culture and syngeneic mouse models. Collectively, our research highlights the pivotal significance of USP13 in unleashing lineage plasticity during lung cancer progression, suggesting the potential role of deubiquitinase enzymes in regulating lineage plasticity, which may lead to novel therapeutics for treating lung cancer. Citation Format: Juntae Kwon, Jinmin Zhang, Boram Mok, Samuel Allsup, Cecil Han. The emerging role of deubiquitinase enzymes in lung cancer plasticity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4294.

Role of regulatory T cells in mouse lung development.

Regulatory T cells (Tregs) constitute a specialized subset of T cells with dual immunoregulatory and modulatory functions. Recent studies have reported that Tregs mediate immune responses and regulate the development and repair processes in non-lymphoid tissues, including bone and cardiac muscle. Additionally, Tregs facilitate the repair and regeneration of damaged lung tissues. However, limited studies have examined the role of Tregs in pulmonary development. This study aimed to evaluate the role of Tregs in pulmonary development by investigating the dynamic alterations in Tregs and their hallmark cellular factor Forkhead box P3 (Foxp3) at various stages of murine lung development and establishing a murine model of anti-CD25 antibody-induced Treg depletion. During the early stages of murine lung development, especially the canalicular and saccular stages, the levels of Treg abundance and expression of Foxp3 and transforming growth factor-β (TGF-β) were upregulated. This coincided with the proliferation period of alveolar epithelial cells and vascular endothelial cells, indicating an adaptation to the dynamic lung developmental processes. Furthermore, the depletion of Tregs disrupted lung tissue morphology and downregulated lung development-related factors, such as surfactant protein C (SFTPC), vascular endothelial growth factor A (VEGFA) and platelet endothelial cell adhesion molecule-1 (PECAM1/CD31). These findings suggest that Tregs promote murine lung development.

IRF4-mediated Treg phenotype switching can aggravate hyperoxia-induced alveolar epithelial cell injury

Bronchopulmonary dysplasia (BPD) is characterized by alveolar dysplasia, and evidence indicates that interferon regulatory factor 4 (IRF4) is involved in the pathogenesis of various inflammatory lung diseases. Nonetheless, the significance and mechanism of IRF4 in BPD remain unelucidated. Consequently, we established a mouse model of BPD through hyperoxia exposure, and ELISA was employed to measure interleukin-17 A (IL-17 A) and interleukin-6 (IL-6) expression levels in lung tissues. Western blotting was adopted to determine the expression of IRF4, surfactant protein C (SP-C), and podoplanin (T1α) in lung tissues. Flow cytometry was utilized for analyzing the percentages of FOXP3+ regulatory T cells (Tregs) and FOXP3+RORγt+ Tregs in CD4+ T cells in lung tissues to clarify the underlying mechanism. Our findings revealed that BPD mice exhibited disordered lung tissue structure, elevated IRF4 expression, decreased SP-C and T1α expression, increased IL-17 A and IL-6 levels, reduced proportion of FOXP3+ Tregs, and increased proportion of FOXP3+RORγt+ Tregs. For the purpose of further elucidating the effect of IRF4 on Treg phenotype switching induced by hyperoxia in lung tissues, we exposed neonatal mice with IRF4 knockout to hyperoxia. These mice exhibited regular lung tissue structure, increased proportion of FOXP3+ Tregs, reduced proportion of FOXP3+RORγt+ Tregs, elevated SP-C and T1α expression, and decreased IL-17 A and IL-6 levels. In conclusion, our findings demonstrate that IRF4-mediated Treg phenotype switching in lung tissues exacerbates alveolar epithelial cell injury under hyperoxia exposure.

Novel air-liquid interface culture model to investigate stiffness-dependent behaviors of alveolar epithelial cells

Pulmonary alveoli are functional units in gas exchange in the lung, and their dysfunctions in lung diseases such as interstitial pneumonia are accompanied by fibrotic changes in structure, elevating the stiffness of extracellular matrix components. The present study aimed to test the hypothesis that such changes in alveoli stiffness induce functional alteration of epithelial cell functions, exacerbating lung diseases. For this, we have developed a novel method of culturing alveolar epithelial cells on polyacrylamide gel with different elastic modulus at an air-liquid interface. It was demonstrated that A549 cells on soft gels, mimicking the modulus of a healthy lung, upregulated mRNA expression and protein synthesis of surfactant protein C (SFTPC). By contrast, the cells on stiff gels, mimicking the modulus of the fibrotic lung, exhibited upregulation of SFTPC gene expression but not at the protein level. Cell morphology, as well as cell nucleus volume, were also different between the two types of gels.

Spatial and phenotypic heterogeneity of resident and monocyte-derived macrophages during inflammatory exacerbations leading to pulmonary fibrosis.

Genetic mutations in critical nodes of pulmonary epithelial function are linked to the pathogenesis of pulmonary fibrosis (PF) and other interstitial lung diseases. The slow progression of these pathologies is often intermitted and accelerated by acute exacerbations, complex non-resolving cycles of inflammation and parenchymal damage, resulting in lung function decline and death. Excess monocyte mobilization during the initial phase of an acute exacerbation, and their long-term persistence in the lung, is linked to poor disease outcome. The present work leverages a clinical idiopathic PF dataset and a murine model of acute inflammatory exacerbations triggered by mutation in the alveolar type-2 cell-restricted Surfactant Protein-C [SP-C] gene to spatially and phenotypically define monocyte/macrophage changes in the fibrosing lung. SP-C mutation triggered heterogeneous CD68+ macrophage activation, with highly active peri-injured cells relative to those sampled from fully remodeled and healthy regions. Ingenuity pathway analysis of sorted CD11b-SigF+CD11c+ alveolar macrophages defined asynchronous activation of extracellular matrix re-organization, cellular mobilization, and Apolipoprotein E (Apoe) signaling in the fibrosing lung. Cell-cell communication analysis of single cell sequencing datasets predicted pro-fibrogenic signaling (fibronectin/Fn1, osteopontin/Spp1, and Tgfb1) emanating from Trem2/TREM2 + interstitial macrophages. These cells also produced a distinct lipid signature from alveolar macrophages and monocytes, characterized by Apoe expression. Mono- and di-allelic genetic deletion of ApoE in SP-C mutant mice had limited impact on inflammation and mortality up to 42 day after injury. Together, these results provide a detailed spatio-temporal picture of resident, interstitial, and monocyte-derived macrophages during SP-C induced inflammatory exacerbations and end-stage clinical PF, and propose ApoE as a biomarker to identify activated macrophages involved in tissue remodeling.

PGF2α signaling drives fibrotic remodeling and fibroblast population dynamics in mice.

Idiopathic pulmonary fibrosis (IPF) is a chronic parenchymal lung disease characterized by repetitive alveolar cell injury, myofibroblast proliferation, and excessive extracellular matrix deposition for which unmet need persists for effective therapeutics. The bioactive eicosanoid, prostaglandin F2α, and its cognate receptor FPr (Ptgfr) are implicated as a TGF-β1-independent signaling hub for IPF. To assess this, we leveraged our published murine PF model (IER-SftpcI73T) expressing a disease-associated missense mutation in the surfactant protein C (Sftpc) gene. Tamoxifen-treated IER-SftpcI73T mice developed an early multiphasic alveolitis and transition to spontaneous fibrotic remodeling by 28 days. IER-SftpcI73T mice crossed to a Ptgfr-null (FPr-/-) line showed attenuated weight loss and gene dosage-dependent rescue of mortality compared with FPr+/+ cohorts. IER-SftpcI73T/FPr-/- mice also showed reductions in multiple fibrotic endpoints for which administration of nintedanib was not additive. Single-cell RNA-Seq, pseudotime analysis, and in vitro assays demonstrated Ptgfr expression predominantly within adventitial fibroblasts, which were reprogrammed to an "inflammatory/transitional" cell state in a PGF2α /FPr-dependent manner. Collectively, the findings provide evidence for a role for PGF2α signaling in IPF, mechanistically identify a susceptible fibroblast subpopulation, and establish a benchmark effect size for disruption of this pathway in mitigating fibrotic lung remodeling.

Exploring protein-protein interactions and oligomerization state of pulmonary surfactant protein C (SP-C) through FRET and fluorescence self-quenching.

Pulmonary surfactant (PS) is a lipid-protein complex that forms films reducing surface tension at the alveolar air-liquid interface. Surfactant protein C (SP-C) plays a key role in rearranging the lipids at the PS surface layers during breathing. The N-terminal segment of SP-C, a lipopeptide of 35 amino acids, contains two palmitoylated cysteines, which affect the stability and structure of the molecule. The C-terminal region comprises a transmembrane α-helix that contains a ALLMG motif, supposedly analogous to a well-studied dimerization motif in glycophorin A. Previous studies have demonstrated the potential interaction between SP-C molecules using approaches such as Bimolecular Complementation assays or computational simulations. In this work, the oligomerization state of SP-C in membrane systems has been studied using fluorescence spectroscopy techniques. We have performed self-quenching and FRET assays to analyze dimerization of native palmitoylated SP-C and a non-palmitoylated recombinant version of SP-C (rSP-C) using fluorescently labeled versions of either protein reconstituted in different lipid systems mimicking pulmonary surfactant environments. Our results reveal that doubly palmitoylated native SP-C remains primarily monomeric. In contrast, non-palmitoylated recombinant SP-C exhibits dimerization, potentiated at high concentrations, especially in membranes with lipid phase separation. Therefore, palmitoylation could play a crucial role in stabilizing the monomeric α-helical conformation of SP-C. Depalmitoylation, high protein densities as a consequence of membrane compartmentalization, and other factors may all lead to the formation of protein dimers and higher-order oligomers, which could have functional implications under certain pathological conditions and contribute to membrane transformations associated with surfactant metabolism and alveolar homeostasis.

Role of DCLK1/Hippo pathway in type II alveolar epithelial cells differentiation in acute respiratory distress syndrome

BackgroundDelay in type II alveolar epithelial cell (AECII) regeneration has been linked to higher mortality in patients with acute respiratory distress syndrome (ARDS). However, the interaction between Doublecortin-like kinase 1 (DCLK1) and the Hippo signaling pathway in ARDS-associated AECII differentiation remains unclear. Therefore, the objective of this study was to understand the role of the DCLK1/Hippo pathway in mediating AECII differentiation in ARDS.Materials and methodsAECII MLE-12 cells were exposed to 0, 0.1, or 1 μg/mL of lipopolysaccharide (LPS) for 6 and 12 h. In the mouse model, C57BL/6JNarl mice were intratracheally (i.t.) injected with 0 (control) or 5 mg/kg LPS and were euthanized for lung collection on days 3 and 7.ResultsWe found that LPS induced AECII markers of differentiation by reducing surfactant protein C (SPC) and p53 while increasing T1α (podoplanin) and E-cadherin at 12 h. Concurrently, nuclear YAP dynamic regulation and increased TAZ levels were observed in LPS-exposed AECII within 12 h. Inhibition of YAP consistently decreased cell levels of SPC, claudin 4 (CLDN-4), galectin 3 (LGALS-3), and p53 while increasing transepithelial electrical resistance (TEER) at 6 h. Furthermore, DCLK1 expression was reduced in isolated human AECII of ARDS, consistent with the results in LPS-exposed AECII at 6 h and mouse SPC-positive (SPC+) cells after 3-day LPS exposure. We observed that downregulated DCLK1 increased p-YAP/YAP, while DCLK1 overexpression slightly reduced p-YAP/YAP, indicating an association between DCLK1 and Hippo-YAP pathway.ConclusionsWe conclude that DCLK1-mediated Hippo signaling components of YAP/TAZ regulated markers of AECII-to-AECI differentiation in an LPS-induced ARDS model.Graphical

Abnormal low expression of SFTPC promotes the proliferation of lung adenocarcinoma by enhancing PI3K/AKT/mTOR signaling transduction.

The abnormality of surfactant protein C (SFTPC) has been linked to the development of a number of interstitial lung diseases, according to mounting evidence. Nonetheless, the function and mechanism of SFTPC in the biological progression of lung adenocarcinoma (LUAD) remain unclear. Analysis of public datasets and testing of clinical samples suggested that SFTPC expression was abnormally low in LUAD, which was associated with the onset and poor prognosis of LUAD. The SFTPC-related risk score was derived using least absolute shrinkage and selection operator Cox regression as well as multivariate Cox regression. The risk score was highly correlated with tumor purity and tumor mutation burden, and it could serve as an independent prognostic indicator for LUAD. Low-risk LUAD patients may benefit more from CTLA-4 or/and PD-1 inhibitors. Overall, the risk score is useful for LUAD patient prognostication and treatment guidance. Moreover, in vitro and in vivo experiments demonstrated that SFTPC inhibits the proliferation of LUAD by inhibiting PI3K/AKT/mTOR signaling transduction. These results reveal the molecular mechanism by which SFTPC inhibits the proliferation of LUAD and suggest that SFTPC could be a new therapeutic target for LUAD.

A promoterless AAV6.2FF-based lung gene editing platform for the correction of surfactant protein B deficiency

Surfactant protein B (SP-B) deficiency is a rare genetic disease that causes fatal respiratory failure within the first year of life. Currently, the only corrective treatment is lung transplantation. Here, we co-transduced the murine lung with adeno-associated virus 6.2FF (AAV6.2FF) vectors encoding a SaCas9-guide RNA nuclease or donor template to mediate insertion of promoterless reporter genes or the (murine) Sftpb gene in frame with the endogenous surfactant protein C (SP-C) gene, without disrupting SP-C expression. Intranasal administration of 3×1011 vg donor template and 1×1011 vg nuclease consistently edited approximately 6% of lung epithelial cells. Frequency of gene insertion increased in a dose-dependent manner, reaching 20%-25% editing efficiency with the highest donor template and nuclease doses tested. We next evaluated whether this promoterless gene editing platform could extend survival in the conditional SP-B knockout mouse model. Administration of 1×1012 vg SP-B-donor template and 5×1011 vg nuclease significantly extended median survival (p= 0.0034) from 5days in the untreated off doxycycline group to 16days in the donor AAV and nuclease group, with one gene-edited mouse living 243days off doxycycline. This AAV6.2FF-based gene editing platform has the potential to correct SP-B deficiency, as well as other disorders of alveolar type II cells.

Roles of Nrf2/HO-1 and ICAM-1 in the Protective Effect of Nano-Curcumin against Copper-Induced Lung Injury.

Copper (Cu) is an essential trace element for maintaining normal homeostasis in living organisms. Yet, an elevated level of Cu beyond homeostatic capacity may lead to oxidative damage of cellular components in several organs, including the lungs. This work investigated the effects of curcumin (Curc) and nano-curcumin (nCurc) against Cu-induced lung injury, accenting the roles of oxidative stress, inflammation, and the nuclear factor erythroid 2-related factor/heme oxygenase-1 Nrf2/HO-1 pathway. Rats were challenged with 100 mg/kg of copper sulfate (CuSO4) while being treated with Curc or nCurc for 7 days. Cu-triggered lung oxidative stress detected as dysregulation of oxidative/antioxidant markers, a downregulation of Nrf-2/HO-1 signaling, and an increase in the inflammatory markers interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-α), and intracellular adhesion molecule-1 (ICAM-1). Additionally, it decreased the expression of lung-specific proteins, surfactant protein-C (SP-C), and mucin-1 (MUC-1), induced apoptosis, and caused changes in lung histology. Curc and nCurc alleviated CuSO4-induced lung injury by suppressing oxidative damage and inflammation and activating Nrf-2/HO-1. They also prevented apoptosis and restored the normal expression of SP-C and MUC-1. We concluded that nCurc exhibited superior efficacy compared with Curc in mitigating CuSO4-induced lung injury. This was associated with reduced oxidative stress, inflammation, and apoptotic responses and increased Nrf2/HO-1 signaling and expression of SP-C and MUC-1.

Laser microdissection, proteomics, and multiplex immunohistochemistry: a bumpy ride into the study of paraffin-embedded fetal and pediatric lung tissues.

Knowledge about lung development or lung disease is mainly derived from data extrapolated from mouse models. This has obvious drawbacks in developmental diseases, particularly due to species differences. Our objective is to describe the development of complementary analysis methods that will allow a better understanding of the molecular mechanisms involved in the pathogenesis of rare congenital diseases. Paraffin-embedded human pediatric and fetal lung samples were laser microdissected to enrich different lung regions, namely, bronchioli or alveoli. These samples were analyzed by data-independent acquisition-based quantitative proteomics, and the lung structures were subsequently compared. To confirm the proteomic data, we employed an optimized Sequential ImmunoPeroxidase Labeling and Erasing (SIMPLE) staining for specific proteins of interest. By quantitative proteomics, we identified typical pulmonary proteins from being differentially expressed in different regions. While the receptor for advanced glycation end products (RAGE) and the surfactant protein C (SFTPC) were downregulated, tubulin beta 4B (TUBB4B) was upregulated in bronchioli, compared to alveoli. In fetal tissues, CD31 was downregulated in fetal bronchioli compared to canaliculi. Moreover, we confirmed their presence using SIMPLE staining. Some expected proteins did not show up in the proteomic data, such as SOX-9, which was only detected by means of immunohistochemistry in the SIMPLE analysis. Our data underline the robustness and applicability of this type of experimental approach, especially for rare paraffin-embedded tissue samples. It also strengthens the importance of these methods for future studies, particularly when considering developmental lung diseases, such as congenital lung anomalies.

Decellularized Lung Extracellular Matrix Scaffold Promotes Human Embryonic Stem Cell Differentiation towards Alveolar Progenitors.

Efficient production of functional and mature alveolar epithelial is a major challenge for developing any cell replacement therapy for lung degenerative diseases. The extracellular matrix (ECM) pro-vides a dynamic environment and mediates cellular responses during development and maintenance of tissue functions. The decellularized ECM (dECM) which retains its native-like structure and bio-chemical composition can provide the induction of embryonic stem cell (ESC) differentiation toward the tissue-specific lineages during in vitro culture. Therefore, the aim of this study was to evaluate the effect of sheep lung dECM-derived scaffold on differentiation and further maturation of ESC-derived lung progenitor cells. This study was an experimental study. In the first step, a sheep lung was decellularized to achieve dECM scaffolds and hydrogels. Afterwards, the obtained dECM scaffold was evaluated for collagen and glycosaminoglycan contents, DNA quantification, and its ultrastructure. Next, the three experimental groups: i. Sheep lung dECM-derived scaffold, ii. Sheep lung dECM-derived hydrogel, and iii. Fibronectin-coated plates were compared in their abilities to induce further differentiation of human embryonic stem cells (hESCs)-derived definitive endoderm (DE) into lung progenitor cells. The comparison was evaluated by immuno-staining and real-time polymerase chain reaction (PCR) assessments. We found that the dECM-derived scaffold preserved its composition and native porous structures while lacking nuclei and intact cells. All experimental groups displayed lung progenitor cell differen-tiation as revealed by the RNA and protein expression of NKX2.1, P63 and CK5. DE cells differenti-ated on dECM-derived scaffold and dECMderived hydrogel showed significant upregulation of SOX9 gene expression, a marker of the distal airway epithelium. DE cells differentiated on the dECM-derived scaffold compared to the two other groups, showed enhanced expression of SFTPC (type 2 alveolar epithelial [AT2] cell marker), FOXJ1 (ciliated cell marker), and MUC5A (secretory cell marker) genes. Overall, our results suggest that dECM-derived scaffold improves the differentiation of DE cells towards lung alveolar progenitor cells in comparison with dECM-derived hydrogel and fibronectin-coated plates.