Vascular-Parenchymal Cross-Talk Promotes Lung Fibrosis through BMPR2 Signaling.

Rationale: Idiopathic pulmonary fibrosis (IPF) is a fatal lung disease characterized by progressive lung scarring. IPF-related pulmonary vascular remodeling and pulmonary hypertension (PH) result in a particularly poor prognosis. Objectives: To study the pathogenesis of vascular remodeling in fibrotic lungs and its contribution to progression of fibrosis. Methods: We used an experimental model of lung fibrosis associated with PH by transient overexpression of active TGF-ß1 (transforming growth factor-ß1). Samples from patients with fibrotic lung diseases were analyzed in depth using immunostaining, gene expression, and gene mutations. Measurements and Main Results: We found a reduction in endothelial cells (ECs) and activation of vascular smooth muscle cells (VSMCs) in fibrotic lungs. Coculturing fibroblasts with VSMCs or ECs from fibrotic lungs induced fibrotic phenotypes in fibroblasts. IPF fibroblasts induced EC death and activation of VSMCs in coculture systems. Decreased concentrations of BMPR2 (bone morphogenic protein receptor 2) and its signaling were observed in ECs and VSMCs from fibrotic lungs in both rats and humans. On fibroblasts treated with media from VSMCs, BMPR2 suppression in VSMCs led to fibrogenic effects. Tacrolimus activated BMPR2 signaling and attenuated fibrosis and PH in rodent lungs. Whole-exome sequencing revealed rare mutations in PH-related genes, including BMPR2, in patients with IPF undergoing transplantation. A unique missense BMPR2 mutation (p.Q721R) was discovered to have dysfunctional effects on BMPR2 signaling. Conclusions: Endothelial dysfunction and vascular remodeling in PH secondary to pulmonary fibrosis enhance fibrogenesis through impaired BMPR2 signaling. Tacrolimus may have value as a treatment of advanced IPF and concomitant PH. Genetic abnormalities may determine the development of PH in advanced IPF.

Intrinsic BMP inhibitor Gremlin regulates alveolar epithelial type II cell proliferation and differentiation.

Type 1 alveolar epithelial cells (AT1s) and type 2 alveolar epithelial cells (AT2s) regulate the structural integrity and function of alveoli. AT1s mediate gas exchange, whereas AT2s serve multiple functions, including surfactant secretion and alveolar repair through proliferation and differentiation into AT1s as progenitors. However, mechanisms regulating AT2 proliferation and differentiation remain unclear. Here we demonstrate that Gremlin, an intrinsic inhibitor of bone morphogenetic protein (BMP), induces AT2 proliferation and differentiation. Transient overexpression of Gremlin in rat lungs by adenovirus vector delivery suppressed BMP signaling, induced proliferation of AT2s and the production of Bmp2, which in turn led to the recovery of BMP signaling and induced AT2 differentiation into AT1s. Bleomycin-induced lung injury upregulated Gremlin and showed a similar time course of biomarker expression comparable to the adenovirus model. TGF-ß and IL-1ß induced Gremlin expression in fibroblasts. Taken together, our findings implicate that Gremlin expression during lung injury leads to precisely timed inhibition of BMP signaling and activates AT2s, leading to alveolar repair.

Connective-Tissue Growth Factor Contributes to TGF-ß1-induced Lung Fibrosis.

Idiopathic pulmonary fibrosis is a fatal lung disease characterized by progressive and excessive accumulation of myofibroblasts and in the lung. Connective-tissue growth factor (CTGF) exacerbates pulmonary fibrosis in radiation-induced lung fibrosis, and in this study, we demonstrate upregulation of CTGF in a rat lung fibrosis model induced by an adenovirus vector encoding active TGF-ß1 (AdTGF-ß1). We show that CTGF is also upregulated in patients with idiopathic pulmonary fibrosis. Expression of CTGF was upregulated in vascular smooth muscle cells cultured from fibrotic lungs on Days 7 and 14 as well as endothelial cells sorted from fibrotic lungs on Days 14 and 28. These findings suggest contributions of different cells in maintaining the fibrotic phenotype during fibrogenesis. Treatment of fibroblasts with recombinant CTGF along with TGF-ß increases profibrotic markers in fibroblasts, confirming the synergistic effect of recombinant CTGF with TGF-ß in inducing pulmonary fibrosis. Also, the fibrotic extracellular matrix upregulated CTGF expression, compared with the normal extracellular matrix, suggesting that not only profibrotic mediators but also a profibrotic environment contributes to fibrogenesis. We also showed that pamrevlumab, a CTGF inhibitory antibody, partially attenuates fibrosis in the model. These results suggest that pamrevlumab could be an option for treatment of pulmonary fibrosis.

Prevalence and characteristics of progressive fibrosing interstitial lung disease in a prospective registry.

BACKGROUND: Progressive fibrosing interstitial lung disease (PF-ILD) is characterised by progressive physiological, symptomatic and/or radiographic worsening. The real-world prevalence and characteristics of PF-ILD remain uncertain. METHODS: Patients were enrolled from the Canadian Registry for Pulmonary Fibrosis between 2015 and 2020. PF-ILD was defined as a relative forced vital capacity (FVC) decline ≥10%, death, lung transplantation or any two of: relative FVC decline ≥5% and <10%, worsening respiratory symptoms or worsening fibrosis on computed tomography of the chest, all within 24 months of diagnosis. Time-to-event analysis compared progression between key diagnostic subgroups. Characteristics associated with progression were determined by multivariable regression. RESULTS: Of 2746 patients with fibrotic ILD (mean±sd age 65±12 years; 51% female), 1376 (50%) met PF-ILD criteria in the first 24 months of follow-up. PF-ILD occurred in 427 (59%) patients with idiopathic pulmonary fibrosis (IPF), 125 (58%) with fibrotic hypersensitivity pneumonitis (HP), 281 (51%) with unclassifiable ILD (U-ILD) and 402 (45%) with connective tissue disease-associated ILD (CTD-ILD). Compared with IPF, time to progression was similar in patients with HP (hazard ratio (HR) 0.96, 95% CI 0.79-1.17), but was delayed in patients with U-ILD (HR 0.82, 95% CI 0.71-0.96) and CTD-ILD (HR 0.65, 95% CI 0.56-0.74). Background treatment varied across diagnostic subtypes, with 66% of IPF patients receiving antifibrotic therapy, while immunomodulatory therapy was utilised in 49%, 61% and 37% of patients with CHP, CTD-ILD and U-ILD, respectively. Increasing age, male sex, gastro-oesophageal reflux disease and lower baseline pulmonary function were independently associated with progression. CONCLUSIONS: Progression is common in patients with fibrotic ILD, and is similarly prevalent in HP and IPF. Routinely collected variables help identify patients at risk for progression and may guide therapeutic strategies.

Fibrotic extracellular matrix induces release of extracellular vesicles with pro-fibrotic miRNA from fibrocytes.

RATIONALE: Extracellular vesicles (EVs) are small lipid vesicles, and EV-coupled microRNAs (miRNAs) are important modulators of biological processes. Fibrocytes are circulating bone marrow-derived cells that migrate into the injured lungs and contribute to fibrogenesis. The question of whether EV-coupled miRNAs derived from fibrocytes are able to regulate pulmonary fibrosis has not been addressed yet. METHODS: Pulmonary fibrosis was induced in rats by intratracheal administration of an adenoviral gene vector encoding active transforming growth factor-ß1 (TGF-ß1) or control vector. Primary fibrocytes and fibroblasts were cultured from rat lungs and were sorted by anti-CD45 magnetic beads. Human circulating fibrocytes and fibrocytes in bronchoalveolar lavage fluid (BALF) were isolated by fibronectin-coated dishes. Fibrocytes were cultured on different stiffness plates or decellularised lung scaffolds. We also determined the effects of extracellular matrix (ECM) and recombinant TGF-ß1 on the cellular and EV-coupled miRNA expression of fibrocytes. RESULTS: The EVs of fibrocytes derived from fibrotic lungs significantly upregulated the expression of col1a1 of fibroblasts. Culturing on rigid plates or fibrotic decellularised lung scaffolds increased miR-21-5 p expression compared with soft plates or normal lung scaffolds. Dissolved ECM collected from fibrotic lungs and recombinant TGF-ß1 increased miR-21-5 p expression on fibrocytes, and these effects were attenuated on soft plates. Fibrocytes from BALF collected from fibrotic interstitial pneumonia patients showed higher miR-21-5 p expression than those from other patients. CONCLUSIONS: Our results indicate that ECM contributes to fibrogenesis through biomechanical and biochemical effects on miRNA expression in fibrocytes.

Real-world experience of nintedanib for progressive fibrosing interstitial lung disease in the UK.

Background: Nintedanib slows progression of lung function decline in patients with progressive fibrosing (PF) interstitial lung disease (ILD) and was recommended for this indication within the United Kingdom (UK) National Health Service in Scotland in June 2021 and in England, Wales and Northern Ireland in November 2021. To date, there has been no national evaluation of the use of nintedanib for PF-ILD in a real-world setting. Methods: 26 UK centres were invited to take part in a national service evaluation between 17 November 2021 and 30 September 2022. Summary data regarding underlying diagnosis, pulmonary function tests, diagnostic criteria, radiological appearance, concurrent immunosuppressive therapy and drug tolerability were collected via electronic survey. Results: 24 UK prescribing centres responded to the service evaluation invitation. Between 17 November 2021 and 30 September 2022, 1120 patients received a multidisciplinary team recommendation to commence nintedanib for PF-ILD. The most common underlying diagnoses were hypersensitivity pneumonitis (298 out of 1120, 26.6%), connective tissue disease associated ILD (197 out of 1120, 17.6%), rheumatoid arthritis associated ILD (180 out of 1120, 16.0%), idiopathic nonspecific interstitial pneumonia (125 out of 1120, 11.1%) and unclassifiable ILD (100 out of 1120, 8.9%). Of these, 54.4% (609 out of 1120) were receiving concomitant corticosteroids, 355 (31.7%) out of 1120 were receiving concomitant mycophenolate mofetil and 340 (30.3%) out of 1120 were receiving another immunosuppressive/modulatory therapy. Radiological progression of ILD combined with worsening respiratory symptoms was the most common reason for the diagnosis of PF-ILD. Conclusion: We have demonstrated the use of nintedanib for the treatment of PF-ILD across a broad range of underlying conditions. Nintedanib is frequently co-prescribed alongside immunosuppressive and immunomodulatory therapy. The use of nintedanib for the treatment of PF-ILD has demonstrated acceptable tolerability in a real-world setting.

Current models of pulmonary fibrosis for future drug discovery efforts.

INTRODUCTION: Pulmonary fibrosis includes several lung disorders characterized by progressive fibrosis, of which idiopathic pulmonary fibrosis (IPF) is a particularly severe form with a median survival time of 3-5 years after diagnosis. Although numerous compounds have shown efficacy in attenuating pulmonary fibrosis using animal models, only a few compounds have shown their beneficial effects for IPF in clinical trials. Thus, there is an emergent need to improve the preclinical development process to better identify, characterize and select clinically useful targets. AREAS COVERED: In this review, the authors extensively describe current models of pulmonary fibrosis, including rodent models, ex vivo models, and in vitro models. EXPERT OPINION: Based upon our current understanding, improving the identification and characterization of clinically relevant molecules or pathways responsible for progressive fibrotic diseases and use of the appropriate preclinical model system to test these will likely be required to improve the drug development pipeline for pulmonary fibrosis. Combination with appropriate preclinical models with ex vivo (precision-cut lung slices) or in vitro models would be beneficial for high-throughput drug discovery or validation of drug effects.

Nintedanib and intensive immunosuppressive therapy to treat rapidly progressive interstitial lung disease presenting anti-ARS antibodies.

We describe a case of fulminant onset, rapidly progressive-interstitial lung disease (RP-ILD) with anti-ARS antibodies (anti-PL-7). The patient was successfully treated with nintedanib in addition to intensive immunosuppressive therapies, including intravenous cyclophosphamide. Nintedanib has just been approved for treatment of progressive fibrosing ILD, but to date, no reports of RP-ILD treated with nintedanib have been published. This case report may advance discussions regarding the use and timing of nintedanib in treating RP-ILD.

Fibrocytes and fibroblasts-Where are we now.

Fibroblasts are considered major contributors to the process of fibrogenesis and the progression of matrix deposition and tissue distortion in fibrotic diseases such as Pulmonary Fibrosis. Recent discovery of the fibrocyte, a circulating possible precursor cell to the tissue fibroblast in fibrosis, has raised issues regarding the characterization of fibrocytes with respect to their morphology, growth characteristics in vitro, their biological role in vivo and their potential utility as a biomarker and/ or treatment target in various human diseases. Characterization studies of the fibrocyte continue as does emerging conflicting data concerning the relationship to or with the lung fibroblast. The source of signals that direct the traffic of these cells, as well as their response to therapeutic intervention with newly available drugs, bring new insights to the understanding of this cell type. The identification of exosomes from fibrocytes that can affect resident fibroblast activities suggest mechanisms of their influence on pathogenesis. Moreover, interesting comparisons with other pathologies are emerging involving the influence of circulating mesenchymal precursor cells on tissue responses.

Rapid resolution of pulmonary Langerhans cell histiocytosis.

A 38-year-old woman with a long-term history of smoking presented to the lung cancer clinic with weight loss and recurrent lower respiratory tract infections. A diagnosis of Langerhans cell histiocytosis was made by specimen samples taken from video-assisted thoracoscopic surgery. She was advised to stop smoking, which she adhered to. She was followed up in the respiratory clinic with pulmonary function tests every 6 months, which were all normal. Follow-up chest x-ray showed complete resolution of the multifocal interstitial infiltrates, and with smoking cessation, the patient has sustained an excellent quality of life.