Fibroblasts and their responses to chronic injury in pulmonary fibrosis

The field of pulmonary fibrosis is rapidly expanding as new insights highlight novel mechanisms that influence fibroblast biology and likely promote aberrant and chronic activation of the tissue repair response. Current paradigms suggest repeated epithelial microinjury as a driver for pathology; however, the rapid expansion of pulmonary fibrosis research calls for an overview on how fibroblasts respond to both neighbouring cells and the injury microenvironment. This review seeks to highlight recent discoveries and identify areas that require further research regarding fibroblasts, and their role in pulmonary fibrosis.

[New developments in systemic sclerosis-associated interstitial lung disease]

Interstitial lung disease is a frequent complication of systemic sclerosis and has now become the leading cause of death in this disorder. It mainly occurs during the first five years after the diagnosis of systemic sclerosis. Various risk factors are associated with the occurrence of interstitial lung disease, including the presence of anti-topoisomerase I antibodies (Scl-70) and the diffuse cutaneous form of systemic sclerosis. The most common radio-pathological presentation is nonspecific interstitial pneumonia, followed by usual interstitial pneumonia. The classical immunosuppressive treatment of systemic sclerosis-associated interstitial lung disease is evolving, as recent studies suggest a beneficial effect of biological agents such as rituximab and tocilizumab, and antifibrotic drugs such as nintedanib.

GPRC5A reduction contributes to pollutant benzo[a]pyrene injury via aggravating murine fibrosis, leading to poor prognosis of IIP patients

Air pollution exposure is recently reported to be one of the drivers of exacerbation in idiopathic pulmonary fibrosis (IPF). But there was a lack of direct evidence between pollution and lung fibrosis. Here, our data show effects of pollutant benzo[a]pyrene (BaP) and protein G-protein-coupled receptor family C group 5 type A (GPRC5A) on pulmonary fibrosis, which might help limit potential pollutant injury and disease progression. We cross-referenced epithelial differentially-expressed-genes (DEGs) from pollutant injury and published experimental fibrosis and IPF patients' data, top common-DEG (CO-DEG) GPRC5A was identified as a potential link between exposure-damage and fibrogenesis. The role of GPRC5A was evaluated under BaP exposure, in idiopathic interstitial pneumonia (IIP) tissue-array and via CRISPR/Cas9 knockout mice (Gprc5a^-/-). BaP exposure enhanced bleomycin (BLM)-induced murine pulmonary fibrosis with increased Fibronectin and α-SMA expression in primary fibroblasts, thickened respiratory membrane and damaged alveolar type II cell, combined with Gprc5a decline in fibrotic mass. GPRC5A mRNA reduced after 10-14 days' BaP exposure in human epithelial cell A549. GPRC5A protein was further found to decrease in IIP epithelium, especially hyperplastic regions. A high epithelial GPRC5A expression score was positively associated with long survival time (R = 0.34) while negatively with high age (R = -0.4) and IIP type IPF (R = -0.5). Low GPRC5A expression predicts poor prognosis (HR = 4.5). Gprc5a depletion aggravated mortality rate (50%) with increased collagen deposition and myofibroblast activation under BLM treatment and exacerbated BaP injury in lung remodeling. Vitamin metabolic imbalance and Mitofusion2 (Mfn2) or Opa1-regulated mitochondrial dynamics were deduced to contribute to Gprc5a depletion and fibrogenesis. Pollutant BaP exposure worsens murine fibrosis and myofibroblast activation via GPRC5A reduction in the damaged epithelium. GPRC5A deficiency was first confirmed to contribute to both poor prognosis of IIP patients and fibrogenesis in murine model; thus, GPRC5A could serve as a novel therapeutic target in pollutant injury and pulmonary fibrosis.

Perioperative risk factors in patients with idiopathic pulmonary fibrosis: a historical cohort study

PURPOSE

Perioperative complications of patients with idiopathic pulmonary fibrosis (IPF) are not well described. The aim of this study was to identify risk factors associated with adverse postoperative outcomes in IPF patients.

METHODS

We performed a single-centre historical cohort study of adult patients with IPF who underwent surgery between 2008 and 2018. We analyzed the prognostic utility of select perioperative factors for postoperative acute exacerbation of IPF (AE-IPF), acute respiratory worsening (ARW), pneumonia, and 30-day and one-year mortality using univariable and multivariable regression analyses. To adjust for multiple interactions, the false discovery rate (Q value) was utilized to appropriately adjust P values and a Q value < 0.05 was considered to be significant.

RESULTS

Two hundred and eighty-two patients were identified. After excluding emergency cases and bronchoscopies performed for active pneumonia, 14.2% of the cohort developed ARW that persisted > 24 hr after surgery, 5.0% had AE-IPF, and 9.2% were diagnosed with postoperative pneumonia within 30 days of surgery. The 30-day mortality was 6.0% and the one-year mortality was 14.9%. Preoperative home oxygen use (relative risk [RR], 2.70; 95% confidence interval [CI], 1.50 to 4.86; P < 0.001) and increasing surgical time (per 60 min) (RR, 1.03; 95% CI, 1.02 to 1.05; P < 0.001) were identified as independent risk factors for postoperative ARW.

CONCLUSIONS

In IPF patients, preoperative home oxygen requirement and increasing surgical time showed a strong relationship with postoperative ARW and may be useful markers for perioperative risk stratification. Facteurs de risque périopératoires des patients atteints de fibrose pulmonaire idiopathique : une étude de cohorte historique.

Mapping cardiopulmonary dynamics within the microvasculature of the lungs using dissolved 129Xe MRI

Magnetic resonance (MR) imaging and spectroscopy using dissolved hyperpolarized (HP) 129Xe have expanded the ability to probe lung function regionally and noninvasively. In particular, HP 129Xe imaging has been used to quantify impaired gas uptake by the pulmonary tissues. Whole-lung spectroscopy has also been used to assess global cardiogenic oscillations in the MR signal intensity originating from 129Xe dissolved in the red blood cells of pulmonary capillaries. Herein, we show that the magnitude of these cardiogenic dynamics can be mapped three dimensionally using radial MRI, because dissolved 129Xe dynamics are encoded directly in the raw imaging data. Specifically, 1-point Dixon imaging is combined with postacquisition keyhole image reconstruction to assess regional blood volume fluctuations within the pulmonary microvasculature throughout the cardiac cycle. This "oscillation mapping" was applied in healthy subjects (mean amplitude 9% of total RBC signal) and patients with pulmonary arterial hypertension (PAH; mean 4%) and idiopathic pulmonary fibrosis (IPF; mean 14%). Whole-lung mean values from these oscillation maps correlated strongly with spectroscopy and clinical pulmonary function testing, but exhibited significant regional heterogeneity, including gravitationally dependent gradients in healthy subjects. Moreover, regional oscillations were found to be sensitive to disease state. Greater percentages of the lungs exhibit low-amplitude oscillations in PAH patients, and longitudinal imaging shows high-amplitude oscillations increase significantly over time (4-14 mo, P = 0.02) in IPF patients. This technique enables regional dynamics within the pulmonary capillary bed to be measured, and in doing so, provides insight into the origin and progression of pathophysiology within the lung microvasculature.NEW & NOTEWORTHY Spatially heterogeneous abnormalities within the lung microvasculature contribute to pathology in various cardiopulmonary diseases but are difficult to assess noninvasively. Hyperpolarized 129Xe MRI is a noninvasive method to probe lung function, including regional gas exchange between pulmonary air spaces and capillaries. We show that cardiogenic oscillations in the raw dissolved 129Xe MRI signal from pulmonary capillary red blood cells can be imaged using a postacquisition reconstruction technique, providing a new means of assessing regional lung microvasculature function and disease state.

[Pulmonary medicine: asthma, chronic obstructive pulmonary disease and idiopathic pulmonary fibrosis]

Important changes have been proposed by expert groups for the management of mild asthma and chronic obstructive pulmonary disease (COPD): for safety reasons, short-acting beta-2 agonists (SABA) are no longer recommended as « reliever therapy » in mild asthma, and should be replaced by symptom-driven inhaled corticosteroids, alone or combined with a beta-2 agonist ; for COPD patients recommendations as to use of inhaled corticosteroids have been redefined. New therapeutic options for idiopathic pulmonary fibrosis are being evaluated: recombinant human pentraxin 2 may become a new therapeutic option among the existing specific treatments (pirfenidone, nintedanib). These novelties are discussed in this review of the recent medical literature.

The circadian clock protein REVERBα inhibits pulmonary fibrosis development

Pulmonary inflammatory responses lie under circadian control; however, the importance of circadian mechanisms in the underlying fibrotic phenotype is not understood. Here, we identify a striking change to these mechanisms resulting in a gain of amplitude and lack of synchrony within pulmonary fibrotic tissue. These changes result from an infiltration of mesenchymal cells, an important cell type in the pathogenesis of pulmonary fibrosis. Mutation of the core clock protein REVERBα in these cells exacerbated the development of bleomycin-induced fibrosis, whereas mutation of REVERBα in club or myeloid cells had no effect on the bleomycin phenotype. Knockdown of REVERBα revealed regulation of the little-understood transcription factor TBPL1. Both REVERBα and TBPL1 altered integrinβ1 focal-adhesion formation, resulting in increased myofibroblast activation. The translational importance of our findings was established through analysis of 2 human cohorts. In the UK Biobank, circadian strain markers (sleep length, chronotype, and shift work) are associated with pulmonary fibrosis, making them risk factors. In a separate cohort, REVERBα expression was increased in human idiopathic pulmonary fibrosis (IPF) lung tissue. Pharmacological targeting of REVERBα inhibited myofibroblast activation in IPF fibroblasts and collagen secretion in organotypic cultures from IPF patients, thus suggesting that targeting of REVERBα could be a viable therapeutic approach.

Idiopathic pulmonary fibrosis and occupational risk factors

Idiopathic pulmonary fibrosis (IPF) is a rare lung disease of unknown origin that rapidly leads to death. However, the rate of disease progression varies from one individual to another and is still difficult to predict. The prognosis of IPF is poor, with a median survival of three to five years after diagnosis, without curative therapies other than lung transplantation. The factors leading to disease onset and progression are not yet completely known. The current disease paradigm is that sustained alveolar epithelial micro-injury caused by environmental triggers (e.g., cigarette smoke, microaspiration of gastric content, particulate dust, viral infections or lung microbial composition) leads to alveolar damage resulting in fibrosis in genetically susceptible individuals. Numerous epidemiological studies and case reports have shown that occupational factors contribute to the risk of developing IPF. In this perspective, we briefly review the current understanding of the pathophysiology of IPF and the importance of occupational factors in the pathogenesis and prognosis of the disease. Prompt identification and elimination of occult exposure may represent a novel treatment approach in patients with IPF.

Signals and signposts: Biomarkers in IPF and PAH at the crossroads of clinical relevance

See related Article and Article

Patient Registries in Idiopathic Pulmonary Fibrosis

Over the past decade, several large registries of patients with idiopathic pulmonary fibrosis (IPF) have been established. These registries are collecting a wealth of longitudinal data on thousands of patients with this rare disease. The data collected in these registries will be complementary to data collected in clinical trials because the patient populations studied in registries have a broader spectrum of disease severity and comorbidities and can be followed for a longer period of time. Maintaining the quality and completeness of registry databases presents administrative and resourcing challenges, but it is important to ensuring the robustness of the analyses. Data from patient registries have already helped improve understanding of the clinical characteristics of patients with IPF, the impact that the disease has on their quality of life and survival, and current practices in diagnosis and management. In the future, analyses of biospecimens linked to detailed patient profiles will provide the opportunity to identify biomarkers linked to disease progression, facilitating the development of precision medicine approaches for prognosis and therapy in patients with IPF.

Update in diagnosis and management of interstitial lung disease

The field of interstitial lung disease (ILD) has undergone significant evolution in recent years, with an increasing incidence and more complex, ever expanding disease classification. In their most severe forms, these diseases lead to progressive loss of lung function, respiratory failure and eventually death. Despite notable advances, progress has been challenged by a poor understanding of pathological mechanisms and patient heterogeneity, including variable progression. The diagnostic pathway is thus being continually refined, with the introduction of tools such as transbronchial cryo lung biopsy and a move towards genetically aided, precision medicine. In this review, we focus on how to approach a patient with ILD and the diagnostic process.

[Effect of three-dimensional acellular fibrotic lung matrices on fibroblast-to-myofibroblast differentiation]

OBJECTIVE

To explore the effect of three-dimensional (3D) and two-dimensional (2D) acellular fibrotic lung matrices on fibroblast-to-myofibroblast differentiation.

METHODS

Twenty adult SD rats were randomly divided into control group and idiopathic pulmonary fibrosis (IPF) group. The pulmonary fibrosis was induced by Bleomycin. Normal and fibrotic decellularized lungs were made, then sections with 500 µm (3D) and 10 µm (2D) thick were cut by a standard Vibratome. The lung fibroblasts were isolated from the lungs of SD rats at postnatal day 1, which were seeded dropwise into different slices (2D/3D normal and fibrotic scaffolds), then cultured for 72 hours in vitro. The protein expression of alpha smooth muscle actin (α-SMA) was measured by immunofluorescence staining and western blot.

RESULTS

There was no spatial structure both in 2D normal scaffold and fibrotic scaffold. The spatial structure was different between 3D normal scaffold and fibrotic scaffold. The relative expression amount of α-SMA in 2D normal and fibrotic scaffold group and none scaffold group were (4.64 ± 0.36, 4.86 ± 0.37, 4.67 ± 0.35, respectively), there were no difference among them (P>0.05). In 3D fibrotic scaffold group, the relative expression amount of α-SMA was significantly increased compared with those in 3D normal scaffold group and 2D fibrotic scaffold group (6.29 ± 0.85 vs 4.85 ± 0.56, 4.86 ± 0.37, both P<0.05).

CONCLUSION

3D acellular fibrotic lung scaffold can promote fibroblast-to-myofibroblast differentiation.

[Clinical and genetic study on familial idiopathic pulmonary fibrosis in a Chinese family]

OBJECTIVE

To identify the manifestations and pathogenesis of idiopathic pulmonary fibrosis (IPF) after studying the clinical features of familial idiopathic pulmonary fibrosis (FIPF) and detecting relevant genes.

METHODS

Seven persons with FIPF from one family of Han nationality in northern China, which had FIPF patients in three consecutive generations, were included in this study. The incidence age of the 7 subjects (4 males and 3 females) ranged from 30 to 57 years. The propositus was II-4, while the first person attacked by FIPF was I-1. Five patients (2 males, 3 females) in the second generation and one case in the third generation were found at the time of this study. The genetic characteristics of FIPF in this study were complied with the pattern of autosomal dominant inheritance. Imaging examinations and pulmonary function tests were conducted to confirm the diagnosis of pulmonary fibrosis. Meanwhile, personal information and clinical data such as imaging examinations and pathological tests were acquired; clinical features and manifestations were analyzed and compared; and pathological tests and gene detection were performed.

RESULTS

The average survival time was 3 years, and poor response to glucocorticoid treatment was observed. Three patients had detailed clinical information, whose interstitial pneumonia related immunologic tests were negative. Concerning pulmonary function, three patients had significant decrease of diffusion function and obvious restrictive ventilatory disorder, with DLCO value as 50%, 23% and 46%, respectively. Among the 3 patients with complete imaging data, 1 was considered as UIP, while 2 as NSIP. The 3 subjects who had different imaging findings all responded poorly to glucocorticoid treatment, and two of them died. Genetic test for TERT, TERC and SFTPC in peripheral blood and autopsy were performed for II-4 but all were negative.

CONCLUSIONS

The average death age of family members with FIPF was 50.2 years. The patients presented various imaging features and pathological findings. Glucocorticoid treatment may be ineffective, even for persons diagnosed as NSIP by lung biopsy.