Macrophage activation in acute exacerbation of idiopathic pulmonary fibrosis

Mechanisms of Lung Fibrosis Resolution

Fibrogenesis involves a dynamic interplay between factors that promote the biosynthesis and deposition of extracellular matrix along with pathways that degrade the extracellular matrix and eliminate the primary effector cells. Opposing the often held perception that fibrotic tissue is permanent, animal studies and clinical data now demonstrate the highly plastic nature of organ fibrosis that can, under certain circumstances, regress. This review describes the current understanding of the mechanisms whereby the lung is known to resolve fibrosis focusing on degradation of the extracellular matrix, removal of myofibroblasts, and the role of inflammatory cells. Although there are significant gaps in understanding lung fibrosis resolution, accelerated improvements in biotechnology and bioinformatics are expected to improve the understanding of these mechanisms and have high potential to lead to novel and effective restorative therapies in the treatment not only of pulmonary fibrosis, but also of a wide-ranging spectrum of chronic disorders.

Pulmonary Macrophages: A New Therapeutic Pathway in Fibrosing Lung Disease?

Pulmonary fibrosis (PF) is a growing clinical problem which can result in breathlessness or respiratory failure and has an average life expectancy of 3 years from diagnosis. Therapeutic options for PF are limited and there is therefore a significant unmet clinical need. The recent resurgent interest in macrophage biology has led to a new understanding of lung macrophage origins, biology, and phenotypes. In this review we discuss fibrotic mechanisms and focus on the role of macrophages during fibrotic lung disease. Data from both human and murine studies are reviewed, highlighting novel macrophage-orientated biomarkers for disease diagnosis and potential targets for future anti-fibrotic therapies.

Leukocytes: The Double-Edged Sword in Fibrosis

Skin tissue scar formation and fibrosis are often characterized by the increased production and deposition of extracellular matrix components, accompanied by the accumulation of a vast number of myofibroblasts. Scaring is strongly associated with inflammation and wound healing to regain tissue integrity in response to skin tissue injury. However, increased and uncontrolled inflammation, repetitive injury, and individual predisposition might lead to fibrosis, a severe disorder resulting in the formation of dense and stiff tissue that loses the physical properties and physiological functions of normal tissue. Fibrosis is an extremely complicated and multistage process in which bone marrow-derived leukocytes act as both pro- and antifibrotic agents, and therefore, few, if any, effective therapies are available for the most severe and lethal forms of fibrosis. Herein, we discuss the current knowledge on the multidimensional impact of leukocytes on the induction of fibrosis, focusing on skin fibrosis.

Role of bronchoalveolar lavage in the diagnosis of acute exacerbations of idiopathic pulmonary fibrosis: a retrospective study

Background

It has been recognized that despite previous stability some patients with idiopathic pulmonary fibrosis (IPF) experience acute clinical deteriorations called acute exacerbations of idiopathic pulmonary fibrosis (AEX-IPF). We hypothesized that pulmonary infection can be excluded based on clinical and laboratory data and that bronchoscopy with BAL is not mandatory in the diagnostic work-up of suspected AEX-IPF.

Methods

In this retrospective study we identified patients with acute respiratory failure who were evaluated for AEX-IPF at the Cleveland Clinic between January 2002 and December 2011. Univariate and multivariate analysis were performed with predefined risk factors and final diagnosis of AEX-IPF and pulmonary infection. All tests were performed at a significance level of 0.05.

Results

A total of 77 patients met the study inclusion criteria. Of these patients 47 (61 %) were diagnosed with AEX-IPF. Bronchoscopy was more likely to be performed in patients who were on cytotoxic medications (p < 0.05). In most cases the diagnosis of AEX-IPF versus pulmonary infection was based on combination of other microbiological, clinical, radiologic data and clinical judgment. A total of 10 patients out of 14 (71 %) with a final diagnosis of pulmonary infection were on steroids on admission versus 21 out of 63 patients (33 %) with other final diagnosis (p = 0.024, OR 7.817, 95 % CI 1.31–46.64).

Conclusions

Exclusion of infection in our IPF patient cohort was mostly based on factors other than diagnostic bronchoscopy with BAL. Based on our results we suggested an algorithm for management of IPF patients presenting with acute respiratory failure.

Novel insights into the function and dynamics of extracellular matrix in liver fibrosis

Emerging evidence suggests that altered components and posttranslational modifications of proteins in the extracellular matrix (ECM) may both initiate and drive disease progression. The ECM is a complex grid consisting of multiple proteins, most of which play a vital role in containing the essential information needed for maintenance of a sophisticated structure anchoring the cells and sustaining normal function of tissues. Therefore, the matrix itself may be considered as a paracrine/endocrine entity, with more complex functions than previously appreciated. The aims of this review are to 1) explore key structural and functional components of the ECM as exemplified by monogenetic disorders leading to severe pathologies, 2) discuss selected pathological posttranslational modifications of ECM proteins resulting in altered functional (signaling) properties from the original structural proteins, and 3) discuss how these findings support the novel concept that an increasing number of components of the ECM harbor signaling functions that can modulate fibrotic liver disease. The ECM entails functions in addition to anchoring cells and modulating their migratory behavior. Key ECM components and their posttranslational modifications often harbor multiple domains with different signaling potential, in particular when modified during inflammation or wound healing. This signaling by the ECM should be considered a paracrine/endocrine function, as it affects cell phenotype, function, fate, and finally tissue homeostasis. These properties should be exploited to establish novel biochemical markers and antifibrotic treatment strategies for liver fibrosis as well as other fibrotic diseases.