Hyperpolarized 129Xe MR Spectroscopy in the Lung Shows 1-year Reduced Function in Idiopathic Pulmonary Fibrosis.

Background Idiopathic pulmonary fibrosis (IPF) is a temporally and spatially heterogeneous lung disease. Identifying whether IPF in a patient is progressive or stable is crucial for treatment regimens. Purpose To assess the role of hyperpolarized (HP) xenon 129 (129Xe) MRI measures of ventilation and gas transfer in IPF generally and as an early signature of future IPF progression. Materials and Methods In a prospective study, healthy volunteers and participants with IPF were consecutively recruited between December 2015 and August 2019 and underwent baseline HP 129Xe MRI and chest CT. Participants with IPF were followed up with forced vital capacity percent predicted (FVC%p), diffusing capacity of the lungs for carbon monoxide percent predicted (DLco%p), and clinical outcome at 1 year. IPF progression was defined as reduction in FVC%p by at least 10%, reduction in DLco%p by at least 15%, or admission to hospice care. CT and MRI were spatially coregistered and a measure of pulmonary gas transfer (red blood cell [RBC]-to-barrier ratio) and high-ventilation percentage of lung volume were compared across groups and across fibrotic versus normal-appearing regions at CT by using Wilcoxon signed rank tests. Results Sixteen healthy volunteers (mean age, 57 years ± 14 [SD]; 10 women) and 22 participants with IPF (mean age, 71 years ± 9; 15 men) were evaluated, as follows: nine IPF progressors (mean age, 72 years ± 7; five women) and 13 nonprogressors (mean age, 70 years ± 10; 11 men). Reduction of high-ventilation percent (13% ± 6.1 vs 8.2% ± 5.9; P = .03) and RBC-to-barrier ratio (0.26 ± 0.06 vs 0.20 ± 0.06; P = .03) at baseline were associated with progression of IPF. Participants with progressive disease had reduced RBC-to-barrier ratio in structurally normal-appearing lung at CT (0.21 ± 0.07 vs 0.28 ± 0.05; P = .01) but not in fibrotic regions of the lung (0.15 ± 0.09 vs 0.14 ± 0.04; P = .62) relative to the nonprogressive group. Conclusion In this preliminary study, functional measures of gas transfer and ventilation measured with xenon 129 MRI and the extent of fibrotic structure at CT were associated with idiopathic pulmonary fibrosis disease progression. Differences in gas transfer were found in regions of nonfibrotic lung. © RSNA, 2022 Online supplemental material is available for this article. See also the editorial by Gleeson and Fraser in this issue.

Dynamic contrast enhanced MRI for the evaluation of lung perfusion in idiopathic pulmonary fibrosis.

BACKGROUND: The objective of this work was to apply quantitative and semiquantitative dynamic contrast enhanced magnetic resonance imaging (DCE-MRI) methods to evaluate lung perfusion in idiopathic pulmonary fibrosis (IPF). METHODS: In this prospective trial 41 subjects, including healthy control and IPF subjects, were studied using DCE-MRI at baseline. IPF subjects were then followed for 1 year; progressive IPF (IPFprog) subjects were distinguished from stable IPF (IPFstable) subjects based on a decline in percent predicted forced vital capacity (FVC % pred) or diffusing capacity of the lung for carbon monoxide (D LCO % pred) measured during follow-up visits. 35 out of 41 subjects were retained for final baseline analysis (control: n=15; IPFstable: n=14; IPFprog: n=6). Seven measures and their coefficients of variation (CV) were derived using temporally resolved DCE-MRI. Two sets of global and regional comparisons were made: control versus IPF groups and control versus IPFstable versus IPFprog groups, using linear regression analysis. Each measure was compared with FVC % pred, D LCO % pred and the lung clearance index (LCI % pred) using a Spearman rank correlation. RESULTS: DCE-MRI identified regional perfusion differences between control and IPF subjects using first moment transit time (FMTT), contrast uptake slope and pulmonary blood flow (PBF) (p≤0.05), while global averages did not. FMTT was shorter for IPFprog compared with both IPFstable (p=0.004) and control groups (p=0.023). Correlations were observed between PBF CV and D LCO % pred (rs= -0.48, p=0.022) and LCI % pred (rs= +0.47, p=0.015). Significant group differences were detected in age (p<0.001), D LCO % pred (p<0.001), FVC % pred (p=0.001) and LCI % pred (p=0.007). CONCLUSIONS: Global analysis obscures regional changes in pulmonary haemodynamics in IPF using DCE-MRI in IPF. Decreased FMTT may be a candidate marker for IPF progression.

[68 Ga]Ga-FAPI-46 PET for non-invasive detection of pulmonary fibrosis disease activity.

PURPOSE: The lack of effective molecular biomarkers to monitor idiopathic pulmonary fibrosis (IPF) activity or treatment response remains an unmet clinical need. Herein, we determined the utility of fibroblast activation protein inhibitor for positron emission tomography (FAPI PET) imaging in a mouse model of pulmonary fibrosis. METHODS: Pulmonary fibrosis was induced by intratracheal administration of bleomycin (1 U/kg) while intratracheal saline was administered to control mice. Subgroups from each cohort (n = 3-5) underwent dynamic 1 h PET/CT after intravenously injecting FAPI-46 radiolabeled with gallium-68 ([68 Ga]Ga-FAPI-46) at 7 days and 14 days following disease induction. Animals were sacrificed following imaging for ex vivo gamma counting and histologic correlation. [68 Ga]Ga-FAPI-46 uptake was quantified and reported as percent injected activity per cc (%IA/cc) or percent injected activity (%IA). Lung CT density in Hounsfield units (HU) was also correlated with histologic examinations of lung fibrosis. RESULTS: CT only detected differences in the fibrotic response at 14 days post-bleomycin administration. [68 Ga]Ga-FAPI-46 lung uptake was significantly higher in the bleomycin group than in control subjects at 7 days and 14 days. Significantly (P = 0.0012) increased [68 Ga]Ga-FAPI-46 lung uptake in the bleomycin groups at 14 days (1.01 ± 0.12%IA/cc) vs. 7 days (0.33 ± 0.09%IA/cc) at 60 min post-injection of the tracer was observed. These findings were consistent with an increase in both fibrinogenesis and FAP expression as seen in histology. CONCLUSION: CT was unable to assess disease activity in a murine model of IPF. Conversely, FAPI PET detected both the presence and activity of lung fibrogenesis, making it a promising tool for assessing early disease activity and evaluating the efficacy of therapeutic interventions in lung fibrosis patients.

Expression of serum response factor in the lung mesenchyme is essential for development of pulmonary fibrosis.

Extracellular matrix deposition characterizes idiopathic pulmonary fibrosis (IPF) and is orchestrated by myofibroblasts. The lung mesenchyme is an essential source of myofibroblasts in pulmonary fibrosis. Although the transcription factor serum response factor (SRF) has shown to be critical in the process of myofibroblast differentiation, its role in development of pulmonary fibrosis has not been determined in vivo. In this study, we observed that SRF expression localized to mesenchymal compartments, areas of dense fibrosis, and fibroblastic foci in human (IPF and normal) and bleomycin-treated mouse lungs. To determine the role of mesenchymal SRF in pulmonary fibrosis, we utilized a doxycycline-inducible, Tbx4 lung enhancer (Tbx4LE)-driven Cre-recombinase to disrupt SRF expression in the lung mesenchyme in vivo. Doxycycline-treated Tbx4LE-rtTA/TetO-Cre/tdTom/SRFf,f (and controls) were treated with a single intratracheal dose of bleomycin to induce pulmonary fibrosis and examined for lung mesenchymal expansion, pulmonary fibrosis, and inflammatory response. Bleomycin-treated Tbx4LE-rtTA/TetO-Cre/tdTom/SRFf,f mice showed decreased numbers of Tbx4LE-positive lung mesenchymal cells (LMCs) and collagen accumulation (via hydroxyproline assay) compared with controls. This effect was associated with SRF-null LMCs losing their proliferative and myofibroblast differentiation potential compared with SRF-positive controls. Together, these data demonstrate that SRF plays a critical role in LMC myofibroblast expansion during bleomycin-induced pulmonary fibrosis. This sets the stage for pharmacological strategies that specifically target SRF in the lung mesenchyme as a potential means of treating pulmonary fibrosis.

Analysis of fibroblast migration dynamics in idiopathic pulmonary fibrosis using image-based scaffolds of the lung extracellular matrix.

Idiopathic pulmonary fibrosis (IPF) is characterized by a profound remodeling of the collagen in the extracellular matrix (ECM), where the fibers become both denser and more highly aligned. However, it is unknown how this reconfiguration of the collagen matrix affects disease progression. Here, we investigate the role of specific alterations in collagen fiber organization on cell migration dynamics by using biomimetic image-based collagen scaffolds representing normal and fibrotic lung, where the designs are derived directly from high-resolution second harmonic generation microscopy images. The scaffolds are fabricated by multiphoton-excited (MPE) polymerization, where the process is akin to three-dimensional printing, except that it is performed at much greater resolution (∼0.5 microns) and with collagen and collagen analogs. These scaffolds were seeded with early passaged primary human normal and IPF fibroblasts to enable the decoupling of the effect of cell-intrinsic characteristics (normal vs. IPF) versus ECM structure (normal vs. IPF) on migration dynamics. We found that the highly aligned IPF collagen structure promoted enhanced cell elongation and F-actin alignment along with increased cell migration speed and straightness relative to the normal tissues. Collectively, the data are consistent with an enhanced contact guidance mechanism on the aligned IPF matrix. Although cell intrinsic effects were observed, the aligned collagen matrix morphology had a larger effect on these metrics. Importantly, these biomimetic models of the lung cannot be synthesized by conventional fabrication methods. We suggest that the MPE image-based fabrication method will enable additional hypothesis-based testing studies of cell-matrix interactions in the context of tissue fibrosis.

Eosinophil cytolysis on Immunoglobulin G is associated with microtubule formation and suppression of rho-associated protein kinase signalling.

BACKGROUND: The presence of eosinophils in the airway is associated with asthma severity and risk of exacerbations. Cell-free eosinophil granules are found in tissues in eosinophilic diseases, including asthma. This suggests that eosinophils have lysed and released cellular content, likely harming tissues. OBJECTIVE: The present study explores the mechanism of CD32- and αMß2 integrin-dependent eosinophil cytolysis of IL3-primed blood eosinophils seeded on heat-aggregated immunoglobulin G (HA-IgG). METHODS: Cytoskeletal events and signalling pathways potentially involved in cytolysis were assessed using inhibitors. The level of activation of the identified events and pathways involved in cytolysis was measured. In addition, the links between these identified pathways and changes in degranulation (exocytosis) and adhesion were analysed. RESULTS: Cytolysis of IL3-primed eosinophils was dependent on the production of reactive oxygen species (ROS) and downstream phosphorylation of p-38 MAPK. In addition, formation of microtubule (MT) arrays was necessary for cytolysis and was accompanied by changes in MT dynamics as measured by phosphorylation status of stathmin and microtubule-associated protein 4 (MAP4), the latter of which was regulated by ROS production. Reduced ROCK signalling preceded cytolysis, which was associated with eosinophil adhesion and reduced migration. CONCLUSION AND CLINICAL RELEVANCE: In this CD32- and αMß2 integrin-dependent adhesion model, lysing eosinophils exhibit reduced migration and ROCK signalling, as well as both MT dynamic changes and p-38 phosphorylation downstream of ROS production. We propose that interfering with these pathways would modulate eosinophil cytolysis and subsequent eosinophil-driven tissue damage.

Repeatability of regional pulmonary functional metrics of Hyperpolarized 129 Xe dissolved-phase MRI.

BACKGROUND: MRI of hyperpolarized 129 Xenon (HP 129 Xe) is increasingly utilized for investigating pulmonary function. The solubility of HP 129 Xe in lung tissue, blood plasma (Barrier), and red blood cells (RBC), with unique chemical shifts, enables spectroscopic imaging of potential imaging biomarkers of gas exchange and microstructural pulmonary physiology. PURPOSE: To quantify global average and regional repeatability of Barrier:gas, RBC:gas, and RBC:Barrier ratios derived from dissolved-phase 129 Xe imaging and their dependence on intervisit changes in lung inflation volume. STUDY TYPE: Prospective. POPULATION: Fourteen healthy volunteers. One subject was unable to complete the study resulting in 13 subjects for analysis (eight female, five male, ages 24-69, 53.8 ± 13.9). FIELD STRENGTH: 1.5T. ASSESSMENT: Subjects were imaged using a 3D radial 1-point Dixon method to separate Barrier and RBC component signals, at two different timepoints, with ~1 month between visits. RBC:Gas, Barrier:Gas, and RBC:Barrier measures were compared across time and with pulmonary function tests (PFTs). STATISTICAL TESTS: Repeatablilty was quantified using Bland-Altman plots, coefficient of repeatability, coefficient of variation (CV), and intraclass correlation coefficients (ICCs). Dependence of imaging measures on PFTs and lung volume was evaluated using Spearman and Pearson correlation coefficients, respectively. Statistical significance was determined by F-test for intraclass correlations, and t-test for Spearman correlations and regression. RESULTS: Mean RBC:Gas, Barrier:Gas, and RBC:Barrier had CVs of 19.2%, 20.0%, and 11.5%, respectively, and had significant ICCs, equal to 0.78, 0.79, and 0.92, respectively. Intervisit differences in RBC:Barrier were significantly correlated with intervisit differences in DLCO (r = 0.93, P = 0.007). Significant correlations with intervisit lung volume differences and intervisit differences in mean RBC:Gas (r = -0.73, P = 0.005) and Barrier:Gas (r = -0.69, P = 0.009) were found. DATA CONCLUSION: Three commonly used 129 Xe MRI-based measures of gas-exchange show good repeatability, particularly the Barrier:RBC ratio, which did not depend on lung inflation volume and was strongly associated with intervisit changes in DLCO . LEVEL OF EVIDENCE: 1 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2019;50:1182-1190.

Matrix Metalloproteinase-9-Dependent Release of IL-1ß by Human Eosinophils.

Asthma is often associated with airway eosinophilia, and therapies targeting eosinophils are now available to treat severe eosinophilic asthma. Eosinophilic asthma is often due to a type-2 immune response and production of IL-5, which leads to eosinophilopiesis and recruitment of mature eosinophils in the airways. A concomitant type-2 and type-17 response has been reported in some individuals. IL-17 may be enhanced by IL-1ß production and can lead to neutrophilic inflammation. In fact, both eosinophilic and neutrophilic (mixed granulocytic) inflammation are simultaneously present in a large population of patients with asthma. In monocyte/macrophage cell populations, release of mature IL-1ß occurs via toll-like receptor ligand-induced activation of the inflammasome. Within the inflammasome, a cascade of events leads to the activation of caspase-1, which cleaves pro-IL-1ß protein into a mature, releasable, and active form. We have demonstrated that eosinophils can release IL-1ß in a Toll-like receptor ligand-independent fashion. The objective of this study was to determine the mechanisms underlying the production and maturation of IL-1ß in cytokine-activated eosinophils. Using eosinophils from circulating blood and from bronchoalveolar lavage fluid after an airway allergen challenge, the present study demonstrates that cytokine-activated eosinophils express and release a bioactive form of IL-1ß with an apparent size less than the typical 17 kDa mature form produced by macrophages. Using a zymography approach and pharmacological inhibitors, we identified matrix metalloproteinase-9 (MMP-9) as a protease that cleaves pro-IL-1ß into a ~15 kDa form and allows the release of IL-1ß from cytokine-activated eosinophils. Therefore, we conclude that activated eosinophils produce MMP-9, which causes the release of IL-1ß in an inflammasome/caspase-1-independent manner. The production of IL-1ß by eosinophils may be a link between the eosinophilic/type-2 immune response and the neutrophilic/type-17 immune response that is often associated with a more severe and treatment-refractory type of asthma.

Tensin 1 Is Essential for Myofibroblast Differentiation and Extracellular Matrix Formation.

Myofibroblasts, the primary effector cells that mediate matrix remodeling during pulmonary fibrosis, rapidly assemble an extracellular fibronectin matrix. Tensin (TNS) 1 is a key component of specialized cellular adhesions (fibrillar adhesions) that bind to extracellular fibronectin fibrils. We hypothesized that TNS1 may play a role in modulating myofibroblast-mediated matrix formation. We found that TNS1 expression is increased in fibroblastic foci from lungs with idiopathic pulmonary fibrosis. Transforming growth factor (TGF)-ß profoundly up-regulates TNS1 expression with kinetics that parallel the expression of the myofibroblast marker, smooth muscle α-actin. TGF-ß-induced TNS1 expression is dependent on signaling through the TGF-ß receptor 1 and is Rho coiled-coiled kinase/actin/megakaryoblastic leukemia-1/serum response factor dependent. Small interfering RNA-mediated knockdown of TNS1 disrupted TGF-ß-induced myofibroblast differentiation, without affecting TGF-ß/Smad signaling. In contrast, loss of TNS1 resulted in disruption of focal adhesion kinase phosphorylation, focal adhesion formation, and actin stress fiber development. Finally, TNS1 was essential for the formation of fibrillar adhesions and the assembly of nascent fibronectin and collagen matrix in myofibroblasts. In summary, our data show that TNS1 is a novel megakaryoblastic leukemia-1-dependent gene that is induced during pulmonary fibrosis. TNS1 plays an essential role in TGF-ß-induced myofibroblast differentiation and myofibroblast-mediated formation of extracellular fibronectin and collagen matrix. Targeted disruption of TNS1 and associated signaling may provide an avenue to inhibit tissue fibrosis.

The Novel mTOR Complex 1/2 Inhibitor P529 Inhibits Human Lung Myofibroblast Differentiation.

Idiopathic pulmonary fibrosis is a progressive and deadly disorder with very few therapeutic options. Palomid 529 (8-(1-hydroxyethyl)-2-methoxy-3-(4-methoxybenzyloxy)-benzo[c]chromen-6-one; P529) is a novel dual inhibitor of mechanistic target of rapamycin complex 1/2 (mTORC1/2). In these studies, we investigated the effect of P529 on TGF-ß-dependent signaling and myofibroblast differentiation. TGF-ß-induced phosphorylation of the mTORC1 targets, p70 S6 kinase 1 (S6K1), and eukaryotic translation initiation factor 4E binding protein 1 (4E-BP1), were both dose dependently inhibited by P529 in human lung fibroblasts with maximal inhibition occurring between 10 and 20 µM. mTORC2-mediated phosphorylation of Akt at the S473 site was partially inhibited with a similar dose dependency, as was TGF-ß-induced myofibroblast differentiation. Protein levels of TGF-ß-induced fibronectin and collagen were similarly decreased by P529. At this dose, there was also inhibition of mRNA transcript levels for Col1 and α-SMA, suggesting inhibition of transcriptional activation. However, there was no effect of P529 on canonical TGF-ß-induced Smad signaling, as assessed by receptor-associated Smad2/3 phosphorylation, Smad2/3/4 translocation, or Smad-driven gene expression, as assessed by Smad-binding element driven luciferase. Conversely, activation of mTORC1/2 signaling was dependent on TGF-ß type I receptor (ALK5) signaling and on Smad2/3 expression. P529 treatment disrupted TGF-ß-induced actin stress fiber formation during myofibroblast differentiation, the deposition of new extracellular fibronectin matrix, and linear wound closure by fibroblasts. Likewise, mTOR knockdown inhibited TGF-ß-induced myofibroblast differentiation. In conclusion, P529 inhibits TGF-ß-induced myofibroblast differentiation, actin stress fiber formation, and matrix protein expression and deposition. Inhibition of mTORC1/2 by P529 may be a promising approach to inhibit in vivo fibrosis. J. Cell. Biochem. 118: 2241-2249, 2017. © 2017 Wiley Periodicals, Inc.

RNA-sequencing analysis of lung primary fibroblast response to eosinophil-degranulation products predicts downstream effects on inflammation, tissue remodeling and lipid metabolism.

BACKGROUND: The association of eosinophils with inflammation and tissue remodeling is at least partially due to their release of toxic granule proteins and other mediators, including cytokines. Tissue remodeling and consequent functional defects are affected by activity of connective tissue fibroblasts. Exaggerated fibroblast activation, accumulation and change of phenotype may lead to fibrosis and loss of tissue function. So far, little information has been reported on how eosinophils affect inflammation and tissue remodeling via the activation of fibroblasts. We have recently shown that eosinophil activation with IL-3 led to a robust eosinophil degranulation on immunoglobin-G (IgG) coated plates. Thus, in the present study, we analyze the effects of IL-3-activated eosinophil degranulation products on primary human lung fibroblasts (HLF) using whole transcriptome sequencing. METHODS: Conditioned media was obtained from eosinophils that were pre-activated with IL-3 or IL-5 and subsequently cultured for 6 h on IgG to induce degranulation. This conditioned media was added on human lung fibroblasts (HLF) for 24 h and the cell lysates were then subjected to whole transcriptome sequencing to identify global changes in gene expression. Differentially expressed genes were analyzed using the Ingenuity Pathway Analysis (IPA), and validated by qPCR. RESULTS: In HLF, the expression level of 300 genes was changed by conditioned media from IL-3-activated eosinophils compared to control fibroblast cultures. Among these 300 genes, the expression level of 35 genes coding for known proteins was upregulated by IL-3- versus IL-5-pre-activated eosinophils. Of the 35 upregulated genes, IPA identified C3, CH25H, CXCL1, CXCL8, CYP1A1, ICAM1, IL6 and UCN2 as having downstream functions on inflammation, tissue remodeling and lipid synthesis. This analysis combined with previous RNA sequencing analyses of eosinophils suggest IL-1ß, OSM and TNFSF12 as potential upstream regulators of fibroblasts. CONCLUSIONS: This study has identified several novel pro-inflammatory and pro-remodeling mediators produced by fibroblasts in response to activated eosinophils. These findings may have significant implications on the role of eosinophil/fibroblast interactions in eosinophilic disorders.

Myofibroblasts exhibit enhanced fibronectin assembly that is intrinsic to their contractile phenotype.

Myofibroblasts have increased expression of contractile proteins and display augmented contractility. It is not known if the augmented contractile gene expression characterizing the myofibroblast phenotype impacts its intrinsic ability to assemble fibronectin (FN) and extracellular matrix. In this study we investigated whether myofibroblasts displayed increased rates of FN fibril assembly when compared with their undifferentiated counterparts. Freshly plated myofibroblasts assemble exogenous FN (488-FN) into a fibrillar matrix more rapidly than fibroblasts that have not undergone myofibroblast differentiation. The augmented rate of FN matrix formation by myofibroblasts was dependent on intact Rho/Rho kinase (ROCK) and myosin signals inasmuch as treatment with Y27632 or blebbistatin attenuated 488-FN assembly. Inhibiting contractile gene expression by pharmacologic disruption of the transcription factors megakaryoblastic leukemia-1 (MKL1)/serum response factor (SRF) during myofibroblast differentiation resulted in decreased contractile force generation and attenuated 488-FN incorporation although not FN expression. Furthermore, disruption of the MKL1/SRF target gene, smooth muscle α-actin (α-SMA) via siRNA knockdown resulted in attenuation of 488-FN assembly. In conclusion, this study demonstrates a linkage between increased contractile gene expression, most importantly α-SMA, and the intrinsic capacity of myofibroblasts to assemble exogenous FN into fibrillar extracellular matrix.

Antifibrotic effects of noscapine through activation of prostaglandin E2 receptors and protein kinase A.

Myofibroblast differentiation is a key process in the pathogenesis of fibrotic disease. We have shown previously that differentiation of myofibroblasts is regulated by microtubule polymerization state. In this work, we examined the potential antifibrotic effects of the antitussive drug, noscapine, recently found to bind microtubules and affect microtubule dynamics. Noscapine inhibited TGF-ß-induced differentiation of cultured human lung fibroblasts (HLFs). Therapeutic noscapine treatment resulted in a significant attenuation of pulmonary fibrosis in the bleomycin model of the disease. Noscapine did not affect gross microtubule content in HLFs, but inhibited TGF-ß-induced stress fiber formation and activation of serum response factor without affecting Smad signaling. Furthermore, noscapine stimulated a rapid and profound activation of protein kinase A (PKA), which mediated the antifibrotic effect of noscapine in HLFs, as assessed with the PKA inhibitor, PKI. In contrast, noscapine did not activate PKA in human bronchial or alveolar epithelial cells. Finally, activation of PKA and the antifibrotic effect of noscapine in HLFs were blocked by the EP2 prostaglandin E2 receptor antagonist, PF-04418948, but not by the antagonists of EP4, prostaglandin D2, or prostacyclin receptors. Together, we demonstrate for the first time the antifibrotic effect of noscapine in vitro and in vivo, and we describe a novel mechanism of noscapine action through EP2 prostaglandin E2 receptor-mediated activation of PKA in pulmonary fibroblasts.

Megakaryoblastic leukemia-1 is required for the development of bleomycin-induced pulmonary fibrosis.

BACKGROUND: Fibrosing disorders of the lung, such as idiopathic pulmonary fibrosis, are characterized by progressive extracellular matrix accumulation that is driven by myofibroblasts. The transcription factor megakaryoblastic leukemia-1 (MKL1) mediates myofibroblast differentiation in response to several profibrotic stimuli, but the role it plays in mediating pulmonary fibrosis has not been fully elucidated. In this study, we utilized mice that had a germline deletion of MKL1 (MKL1 (-,-)) to determine the role that MKL1 plays in the development of bleomycin-induced pulmonary fibrosis. METHODS: Bleomycin or normal saline were intratracheally delivered to 9 to 12 week old female MKL1 (+,+) and MKL1 (-,-) mice. Mice were assessed for weight loss and survival to 28 days. Inflammatory responses were assessed through bronchoalveolar lavage at days 3 and 7 post-treatment. The development of pulmonary fibrosis was characterized using hydroxyproline assay and histological staining. MKL1 (+,+) and MKL1 (-,-) mouse lung fibroblasts were isolated to compare morphologic, gene expression and functional differences. RESULTS: MKL1 (-,-) mice demonstrated increased survival, attenuated weight loss, and decreased collagen accumulation compared to wild-type animals 28-days after intratracheal instillation of bleomycin. Histological analysis demonstrated decreased trichrome, smooth muscle α-actin, and fibronectin staining in MKL1(-,-) mice compared to MKL1 (+,+) controls. Differential cell counts from bronchoalveolar lavage demonstrated that there was attenuated neutrophilia 3 days after bleomycin administration, but no difference at day 7. Isolated mouse lung fibroblasts from MKL1 (-,-) mice had decreased contractility and deposited less fibronectin matrix compared to wild-type controls, suggesting a defect in key remodeling functions. CONCLUSIONS: Altogether, these data demonstrate that MKL1 plays a significant role in mediating the fibrotic response to bleomycin injury. Loss of MKL1 attenuated early neutrophil influx, as well as myofibroblast-mediated remodeling. Targeting MKL1 activity may therefore be a useful strategy in treating pulmonary fibrosis.

A functional genomic model for predicting prognosis in idiopathic pulmonary fibrosis.

BACKGROUND: The course of disease for patients with idiopathic pulmonary fibrosis (IPF) is highly heterogeneous. Prognostic models rely on demographic and clinical characteristics and are not reproducible. Integrating data from genomic analyses may identify novel prognostic models and provide mechanistic insights into IPF. METHODS: Total RNA of peripheral blood mononuclear cells was subjected to microarray profiling in a training (45 IPF individuals) and two independent validation cohorts (21 IPF/10 controls, and 75 IPF individuals, respectively). To identify a gene set predictive of IPF prognosis, we incorporated genomic, clinical, and outcome data from the training cohort. Predictor genes were selected if all the following criteria were met: 1) Present in a gene co-expression module from Weighted Gene Co-expression Network Analysis (WGCNA) that correlated with pulmonary function (p < 0.05); 2) Differentially expressed between observed "good" vs. "poor" prognosis with fold change (FC) >1.5 and false discovery rate (FDR) < 2%; and 3) Predictive of mortality (p < 0.05) in univariate Cox regression analysis. "Survival risk group prediction" was adopted to construct a functional genomic model that used the IPF prognostic predictor gene set to derive a prognostic index (PI) for each patient into either high or low risk for survival outcomes. Prediction accuracy was assessed with a repeated 10-fold cross-validation algorithm and independently assessed in two validation cohorts through multivariate Cox regression survival analysis. RESULTS: A set of 118 IPF prognostic predictor genes was used to derive the functional genomic model and PI. In the training cohort, high-risk IPF patients predicted by PI had significantly shorter survival compared to those labeled as low-risk patients (log rank p < 0.001). The prediction accuracy was further validated in two independent cohorts (log rank p < 0.001 and 0.002). Functional pathway analysis revealed that the canonical pathways enriched with the IPF prognostic predictor gene set were involved in T-cell biology, including iCOS, T-cell receptor, and CD28 signaling. CONCLUSIONS: Using supervised and unsupervised analyses, we identified a set of IPF prognostic predictor genes and derived a functional genomic model that predicted high and low-risk IPF patients with high accuracy. This genomic model may complement current prognostic tools to deliver more personalized care for IPF patients.

Control of myofibroblast differentiation by microtubule dynamics through a regulated localization of mDia2.

Myofibroblast differentiation plays a critical role in wound healing and in the pathogenesis of fibrosis. We have previously shown that myofibroblast differentiation is mediated by the activity of serum response factor (SRF), which is tightly controlled by the actin polymerization state. In this study, we investigated the role of the microtubule cytoskeleton in modulating myofibroblast phenotype. Treatment of human lung fibroblasts with the microtubule-destabilizing agent, colchicine, resulted in a formation of numerous stress fibers and expression of myofibroblast differentiation marker proteins. These effects of colchicine were independent of Smad signaling but were mediated by Rho signaling and SRF, as they were attenuated by the Rho kinase inhibitor, Y27632, or by the SRF inhibitor, CCG-1423. TGF-ß-induced myofibroblast differentiation was not accompanied by gross changes in the microtubule polymerization state. However, microtubule stabilization by paclitaxel attenuated TGF-ß-induced myofibroblast differentiation. Paclitaxel had no effect on TGF-ß-induced Smad activation and Smad-dependent gene transcription but inhibited actin polymerization, nuclear accumulation of megakaryoblastic leukemia-1 protein, and SRF activation. The microtubule-associated formin, mDIA2, localized to actin stress fibers upon treatment with TGF-ß, and paclitaxel prevented this localization. Treatment with the formin inhibitor, SMI formin homology 2 domain, inhibited stress fiber formation and myofibroblast differentiation induced by TGF-ß, without affecting Smad-phosphorylation or microtubule polymerization. Together, these data suggest that (a) TGF-ß promotes association of mDia2 with actin stress fibers, which further drives stress fiber formation and myofibroblast differentiation, and (b) microtubule polymerization state controls myofibroblast differentiation through the regulation of mDia2 localization.

Semaphorin 7A is expressed on airway eosinophils and upregulated by IL-5 family cytokines.

Semaphorin 7A (sema7a) plays a major role in TGF-ß1-induced lung fibrosis. Based on the accumulating evidence that eosinophils contribute to fibrosis/remodeling in the airway, we hypothesized that airway eosinophils may be a significant source of sema7a. In vivo, sema7a was expressed on the surface of circulating eosinophils and upregulated on bronchoalveolar lavage eosinophils obtained after segmental bronchoprovocation with allergen. Based on mRNA levels in unfractionated and isolated bronchoalveolar cells, eosinophils are the predominant source of sema7a. In vitro, among the members of the IL-5-family cytokines, sema7a protein on the surface of blood eosinophils was increased more by IL-3 than by GM-CSF or IL-5. Cytokine-induced expression of cell surface sema7a required translation of newly synthesized protein. Finally, a recombinant sema7a induced alpha-smooth muscle actin production in human bronchial fibroblasts. semaphorin 7A is a potentially important modulator of eosinophil profibrotic functions in the airway remodeling of patients with chronic asthma.

[64Cu]Cu-PEG-FUD peptide for noninvasive and sensitive detection of murine pulmonary fibrosis.

Idiopathic pulmonary fibrosis (IPF) is a chronic lung disease resulting in irreversible scarring within the lungs. However, the lack of biomarkers that enable real-time assessment of disease activity remains a challenge in providing efficient clinical decision-making and optimal patient care in IPF. Fibronectin (FN) is highly expressed in fibroblastic foci of the IPF lung where active extracellular matrix (ECM) deposition occurs. Functional upstream domain (FUD) tightly binds the N-terminal 70-kilodalton domain of FN that is crucial for FN assembly. In this study, we first demonstrate the capacity of PEGylated FUD (PEG-FUD) to target FN deposition in human IPF tissue ex vivo. We subsequently radiolabeled PEG-FUD with 64Cu and monitored its spatiotemporal biodistribution via µPET/CT imaging in mice using the bleomycin-induced model of pulmonary injury and fibrosis. We demonstrated [64Cu]Cu-PEG-FUD uptake 3 and 11 days following bleomycin treatment, suggesting that radiolabeled PEG-FUD holds promise as an imaging probe in aiding the assessment of fibrotic lung disease activity.

Regulation of myofibroblast differentiation and bleomycin-induced pulmonary fibrosis by adrenomedullin.

Myofibroblast differentiation induced by transforming growth factor-ß (TGF-ß) is characterized by the expression of smooth muscle α-actin (SMA) and extracellular matrix proteins. We and others have previously shown that these changes are regulated by protein kinase A (PKA). Adrenomedullin (ADM) is a vasodilator peptide that activates cAMP/PKA signaling through the calcitonin-receptor-like receptor (CRLR) and receptor-activity-modifying proteins (RAMP). In this study, we found that recombinant ADM had little effect on cAMP/PKA in quiescent human pulmonary fibroblasts, whereas it induced a profound activation of cAMP/PKA signaling in differentiated (by TGF-ß) myofibroblasts. In contrast, the prostacyclin agonist iloprost was equally effective at activating PKA in both quiescent fibroblasts and differentiated myofibroblasts. TGF-ß stimulated a profound expression of CRLR with a time course that mirrored the increased PKA responses to ADM. The TGF-ß receptor kinase inhibitor SB431542 abolished expression of CRLR and attenuated the PKA responses of cells to ADM but not to iloprost. CRLR expression was also dramatically increased in lungs from bleomycin-treated mice. Functionally, ADM did not affect initial differentiation of quiescent fibroblasts in response to TGF-ß but significantly attenuated the expression of SMA, collagen-1, and fibronectin in pre-differentiated myofibroblasts, which was accompanied by decreased contractility of myofibroblasts. Finally, sensitization of ADM signaling by transgenic overexpression of RAMP2 in myofibroblasts resulted in enhanced survival and reduced pulmonary fibrosis in the bleomycin model of the disease. In conclusion, differentiated pulmonary myofibroblasts gain responsiveness to ADM via increased CRLR expression, suggesting the possibility of using ADM for targeting pathological myofibroblasts without affecting normal fibroblasts.