Concept: Pulmonary fibrosis
Matrix stiffening and myofibroblast resistance to apoptosis are cardinal features of chronic fibrotic diseases involving diverse organ systems. The interactions between altered tissue biomechanics and cellular signaling that sustain progressive fibrosis are not well defined. In this study, we used ex vivo and in vivo approaches to define a mechanotransduction pathway involving Rho/Rho kinase (Rho/ROCK), actin cytoskeletal remodeling, and a mechanosensitive transcription factor, megakaryoblastic leukemia 1 (MKL1), that coordinately regulate myofibroblast differentiation and survival. Both in an experimental mouse model of lung fibrosis and in human subjects with idiopathic pulmonary fibrosis (IPF), we observed activation of the Rho/ROCK pathway, enhanced actin cytoskeletal polymerization, and MKL1 cytoplasmic-nuclear shuttling. Pharmacologic disruption of this mechanotransduction pathway with the ROCK inhibitor fasudil induced myofibroblast apoptosis through a mechanism involving downregulation of BCL-2 and activation of the intrinsic mitochondrial apoptotic pathway. Treatment with fasudil during the postinflammatory fibrotic phase of lung injury or genetic ablation of Mkl1 protected mice from experimental lung fibrosis. These studies indicate that targeting mechanosensitive signaling in myofibroblasts to trigger the intrinsic apoptosis pathway may be an effective approach for treatment of fibrotic disorders.
Extracellular matrix deposition and tissue scarring characterize the process of fibrosis. Transforming growth factor beta (TGFβ) and Insulin-like growth factor binding protein-3 (IGFBP-3) have been implicated in the pathogenesis of fibrosis in various tissues by inducing mesenchymal cell proliferation and extracellular matrix deposition. We identified Syndecan-2 (SDC2) as a gene induced by TGFβ in an IGFBP-3-dependent manner. TGFβ induction of SDC2 mRNA and protein required IGFBP-3. IGFBP-3 independently induced production of SDC2 in primary fibroblasts. Using an ex-vivo model of human skin in organ culture expressing IGFBP-3, we demonstrate that IGFBP-3 induces SDC2 ex vivo in human tissue. We also identified Mitogen-activated protein kinase-interacting kinase (Mknk2) as a gene induced by IGFBP-3. IGFBP-3 triggered Mknk2 phosphorylation resulting in its activation. Mknk2 independently induced SDC2 in human skin. Since IGFBP-3 is over-expressed in fibrotic tissues, we examined SDC2 levels in skin and lung tissues of patients with systemic sclerosis (SSc) and lung tissues of patients with idiopathic pulmonary fibrosis (IPF). SDC2 levels were increased in fibrotic dermal and lung tissues of patients with SSc and in lung tissues of patients with IPF. This is the first report describing elevated levels of SDC2 in fibrosis. Increased SDC2 expression is due, at least in part, to the activity of two pro-fibrotic factors, TGFβ and IGFBP-3.
Pirfenidone (PFD) is a novel antifibrotic agent approved for patients with pulmonary fibrosis. However, there are concerns regarding toxicity of the drug. In this meta-analysis, we analyzed the adverse events (AEs) of PFD for the treatment of pulmonary fibrosis.
BACKGROUND: Stress of the endoplasmic reticulum (ER) leading to activation of the unfolded protein response (UPR) and alveolar epithelial cell (AEC) apoptosis may play a role in the pathogenesis of idiopathic pulmonary fibrosis (IPF). Our objectives were to determine whether circulating caspase-cleaved cytokeratin-18 (cCK-18) is a marker of AEC apoptosis in IPF, define the relationship of cCK-18 with activation of the UPR, and assess its utility as a diagnostic biomarker. METHODS: IPF and normal lung tissues were stained with the antibody (M30) that specifically binds cCK-18. The relationship between markers of the UPR and cCK-18 was determined in AECs exposed in vitro to thapsigargin to induce ER stress. cCK-18 was measured in serum from subjects with IPF, hypersensitivity pneumonitis (HP), nonspecific interstitial pneumonia (NSIP), and control subjects. RESULTS: cCK-18 immunoreactivity was present in AECs of IPF lung, but not in control subjects. Markers of the UPR (phosphorylated IRE-1alpha and spliced XBP-1) were more highly expressed in IPF type II AECs than in normal type II AECs. Phosphorylated IRE-1alpha and cCK-18 increased following thapsigargin-induced ER stress. Serum cCK-18 level distinguished IPF from diseased and control subjects. Serum cCK-18 was not associated with disease severity or outcome. CONCLUSIONS: cCK-18 may be a marker of AEC apoptosis and UPR activation in patients with IPF. Circulating levels of cCK-18 are increased in patients with IPF and cCK-18 may be a useful diagnostic biomarker.
Computed tomography (CT) and spirometry are the mainstays of clinical pulmonary assessment. Spirometry is effort dependent and only provides a single global measure that is insensitive for regional disease, and as such, poor for capturing the early onset of lung disease, especially patchy disease such as cystic fibrosis lung disease. CT sensitively measures change in structure associated with advanced lung disease. However, obstructions in the peripheral airways and early onset of lung stiffening are often difficult to detect. Furthermore, CT imaging poses a radiation risk, particularly for young children, and dose reduction tends to result in reduced resolution. Here, we apply a series of lung tissue motion analyses, to achieve regional pulmonary function assessment in β-ENaC-overexpressing mice, a well-established model of lung disease. The expiratory time constants of regional airflows in the segmented airway tree were quantified as a measure of regional lung function. Our results showed marked heterogeneous lung function in β-ENaC-Tg mice compared to wild-type littermate controls; identified locations of airway obstruction, and quantified regions of bimodal airway resistance demonstrating lung compensation. These results demonstrate the applicability of regional lung function derived from lung motion as an effective alternative respiratory diagnostic tool.
Idiopathic pulmonary fibrosis is a devastating, age-related lung disease of unknown cause that has few treatment options. This disease was once thought to be a chronic inflammatory process, but current evidence indicates that the fibrotic response is driven by abnormally activated alveolar epithelial cells (AECs). These cells produce mediators that induce the formation of fibroblast and myofibroblast foci through the proliferation of resident mesenchymal cells, attraction of circulating fibrocytes, and stimulation of the epithelial to mesenchymal transition. The fibroblast and myofibroblast foci secrete excessive amounts of extracellular matrix, mainly collagens, resulting in scarring and destruction of the lung architecture. The mechanisms that link idiopathic pulmonary fibrosis with ageing and aberrant epithelial activation are unknown; evidence suggests that the abnormal recapitulation of developmental pathways and epigenetic changes have a role. In this Seminar, we review recent data on the clinical course, therapeutic options, and underlying mechanisms thought to be involved in the pathogenesis of idiopathic pulmonary fibrosis.
ABSTRACT BACKGROUND: Idiopathic pulmonary fibrosis is a progressive lung disease with pulmonary vasculopathy. OBJECTIVE: To determine whether sildenafil improves six minute walk distance (6MWD) in subjects with right ventricular dysfunction. MEASUREMENTS: The IPFnet conducted a randomized trial examining the effect of sildenafil on 6MWD in patients with advanced IPF, defined by DLCO <35% predicted. A substudy examined 119/180 randomized subjects where echocardiograms were available for independent review by two cardiologists. Right ventricular (RV) hypertrophy (RVH), right ventricular systolic dysfunction (RVSD) and right ventricular systolic pressure (RVSP) were assessed. Multivariable linear regression models estimated the relationship between RV abnormality, sildenafil treatment and changes in 6MWD, St. George’s Respiratory Score (SGRQ), EuroQol and SF36 from enrollment to 12 weeks. RESULTS: The prevalence of RVH and RVSD were 12.8% and 18.6%, respectively. RVSP was measurable in 71/119 subjects, 60%; mean RVSP was 42.5 mmHg. In the subgroup of subjects with RVSD, sildenafil-treated subjects experienced less decrement in 6MWD (99.3 meters, p=0.01) and greater improvement in SGRQ (13.4 points, p=0.005) and EuroQol visual analog scores (17.9 points, p=0.04) than placebo-treated subjects. In the subgroup with RVH, sildenafil was not associated with change in 6MWD (p=0.13), but was associated with greater relative improvement in SGRQ (14.8 points, p=0.02) versus placebo-treated subjects. Sildenafil treatment in those with RVSD and RVH was not associated with change in SF36. CONCLUSIONS: Sildenafil treatment in IPF with RVSD results in better preservation of exercise capacity as compared to placebo; sildenafil also improves quality of life in subjects with RVH and RVSD.
Idiopathic pulmonary fibrosis (IPF), a manifestation of chronic progressive fibrosing interstitial pneumonia, is with a prevalence of 2-29 cases per 100,000 individuals a rare disease. Current treatment options are limited, and the mean survival time of the newly diagnosed (mostly elderly) patients is only about 2-3 years. As in Europe data are limited on the characteristics and management of such patients, INSIGHTS-IPF was initiated as a new registry that documents incident and prevalent patients with confirmed IPF diagnosis prospectively. Detailed data on patient characteristics, diagnostics, management, clinical outcomes, quality of life and resource utilization are recorded. It is planned to document 500 patients in 30 centers. The registry will contribute to the optimization of the management of IPF patients in the long term.
BACKGROUND: Lung function is an important indicator of cystic fibrosis disease status and those with better forced expiratory volume in 1 s (FEV(1))% predicted have tended to report a better health-related quality of life (HRQoL) in cross-sectional studies. The relationship between lung function and HRQoL over time is unknown. This work assesses the natural progression of HRQoL reporting over many years and compares assessments across a whole decade and evaluates the relationship between lung function and HRQoL longitudinally. METHODS: Demographic (age, gender), clinical (FEV(1)% predicted, body mass index, diabetes, Burkholderia cepacia complex, intravenous access device and nutritional status) and HRQoL (Cystic Fibrosis Quality of Life Questionnaire) variables were obtained every 2 years over a 12-year period (seven time points from 1998 to 2010). RESULTS: HRQoL and lung function declined slowly over time and significant decade changes were observed for FEV(1)% predicted and the nine domains of the Cystic Fibrosis Quality of Life Questionnaire. The results of random coefficient modelling indicated that, at the population level, decreasing FEV(1)% predicted was associated with decreasing HRQoL after adjusting for confounding variables. However, the percentage of patients for whom a decrease in lung function was associated with a decrease in HRQoL differed according to the quality of life domain. CONCLUSIONS: HRQoL and FEV(1)% predicted decline slowly; nevertheless, a decrease in lung function predicted a decrease in HRQoL over time.
Some of the most pressing challenges associated with interstitial lung disease (ILD) are how best to define, diagnose, and treat connective tissue disease-associated ILD (CTD-ILD)–disorders with potentially substantial morbidity and mortality. In this focused review, we address aspects of prognosis for CTD-ILD and what indices might predict outcome, together with lessons that can be learnt from clinical trials of systemic sclerosis-associated ILD and idiopathic pulmonary fibrosis and how these lessons might be applied to future studies of CTD-ILD.