The Daily Sign-Out

DNA Methylation and Gene Expression in Idiopathic Pulmonary Fibrosis

In case you may have missed this one, Ivana Yang and colleagues from the University of Colorado have published a fascinating article in the December 1, 2014 issue of American Journal of Respiratory and Critical Care Medicine, "Relationship of DNA Methylation and Gene Expression in Idiopathic Pulmonary Fibrosis," that explores possible epigenetic mechanisms through DNA methylation that may be involved in the pathogenesis of idiopathic pulmonary fibrosis (IPF).

Many of these studies are being done in various cancers, but this one suggests one or more programs that unfold with IPF.

 

Role of Bone Marrow-Derived HPCs in Pulmonary Fibrosis

Interesting article from AJRCCM just published online that adds to accumulating data implicating circulating bone marrow-derived hematopoietic progenitor cells in the development of lung fibrosis.  Abstract below.

Rationale: Bone marrow (BM)-derived cells have been implicated in pulmonary fibrosis, however, their precise role in pathogenesis is incompletely understood.

Objectives: To elucidate roles of BM-derived cells in bleomycin induced pulmonary fibrosis, and clarify their potential relationship to lung hematopoietic progenitor cells (LHPCs).

Methods: GFP BM-chimera mice treated with or without bleomycin were used to assess the BM derived-cells.

Measurements and Main Results: GFP⁺ cells in the chimera lung were found to be comprised of two distinct phenotypes, namely GFP^hi and GFP^low cells. The GFP⁺, but not GFP^low, population was significantly increased after bleomycin treatment. Flow-cytometric analysis and quantitative RT-PCR revealed that GFP^hi cells exhibited phenotypic characteristics of CD11c⁺ dendritic cells/macrophages. GFP^hi cell conditioned media were chemotactic for fibroblasts obtained from fibrotic but not normal lung in vitro. Moreover, adoptive transfer of GFP^hi cells exacerbated fibrosis in recipient mice, similar to that seen upon adoptive transfer of BM-derived CD11c⁺ cells from donor bleomycin-treated mice. Next, we evaluated the potential of LHPCs as the source of GFP^hi cells. Isolation of LHPCs by flow sorting revealed enrichment in cKit⁺/Sca1^-/Lin^- cells, most of which were GFP⁺ indicating their BM origin. The number of LHPCs increased rapidly after bleomycin treatment. Furthermore, SCF induced LHPC proliferation, while GM-CSF induced differentiation to GFP^hi cells.

Conclusions: BM-derived LHPCs with a novel phenotype could differentiate into GFP^hi cells, which enhanced pulmonary fibrosis. Targeting this mobilized LHPCs might represent a novel therapeutic approach in chronic fibrotic lung diseases.


Read More: http://www.atsjournals.org/doi/abs/10.1164/rccm.201303-0479OC

Atomic force microscopy! EMT and idiopathic pulmonary fibrosis

Here is a very intesting article I recently found with some very cool technology:

Abstract:

Epithelial-mesenchymal transition (EMT) is closely implicated in the pathogenesis of idiopathic pulmonary fibrosis. Associated with this phenotypic transition is the acquisition of an elongated cell morphology and establishment of stress fibers. The extent to which these EMT-associated changes influence cellular mechanics is unclear. We assessed the biomechanical properties of alveolar epithelial cells (A549) following exposure to TGF-β1. Using atomic force microscopy, changes in cell stiffness and surface membrane features were determined. Stimulation with TGF-β1 gave rise to a significant increase in stiffness, which was augmented by a collagen I matrix. Additionally, TGF-β1-treated cells exhibited a rougher surface profile with notable protrusions. Simultaneous quantitative examination of the morphological attributes of stimulated cells using an image-based high-content analysis system revealed dramatic alterations in cell shape, F-actin content and distribution. Together, these investigations point to a strong correlation between the cytoskeletal-associated cellular architecture and the mechanical dynamics of alveolar epithelial cells undergoing EMT.

http://dx.doi.org/10.1016/j.nano.2011.06.021

I know this is a little out there for the pedestrian pathologist (ahem, like me) but I thought this was so cool--definitely worth at least scanning for the images of atomic force microscopy alone! But this article also provides data at the cellular level to explain some of the mechanical forces behind the changes that occur in IPF.

Updates on respiratory bronchiolitis/interstitial lung disease

Churg, Muller and Wright published a superb update on RB/ILD in the January 2010 Arch Pathol Lab Med which is essential background to Katzenstein's article in Human Pathology on "occult interstitial fibrosis in smokers."  Do yourself a favor and just read my summary of the Katzenstein paper (skip the original) in light of the excellent update by Dr. Churg.

RB/ILD can be described as a clinicopathologic entity characterized by clinically evident interstitial lung disease (originally described by Myers et al. as restrictive pattern of changes by PFTs and/or bilateral, poorly defined centrilobular nodules and ground-glass opacities mainly involving lower lung fields by HRCT) and histologic changes listed below with specific exclusion other forms of ILD.  Morphologic changes include:

• clusters of pigmented alveolar macrophages in respiratory bronchiolar lumens--the fundamental requirement for diagnosis
• mild chronic interstitial inflammation, mild interstitial fibrosis and type 2 pneumocyte hyperplasia in bronchioles and adjacent alveolar walls

But since RB/ILD is a disease of cigarette smokers (and heavy smokers at that--reported mean pack-years between 29 to 54), these patients also are at risk for COPD--"a process that potentially confounds the diagnois of RBILD pathologically, radiologically, and on pulmonary function testing."

Can we separate RBILD from RB?  Based on their review, the authors find that there are no histologic features that separate RBILD from RB.  Moreover, although some authors have contended that clinical RBILD is associated with a greater degree of fibrosis histologically, this point is in doubt since many lungs from smokers also show some (usually mild) alveolar wall fibrosis (thus see comments about the Katzenstein article below).

What is the relationship between RB/RBILD and centrilobular emphysema?  The authors note that emphysematous foci are (as one would expect) a common finding in patients with RB/RBILD and that foci of centrilobular emphysema can be associated with fibrosis.  Which begs the question "whether some of the descriptions of alveolar wall fibrosis associated with RB/RBILD may really be misclassifications of fibrotic emphysematous foci."  In addition, previous studies including careful evaluation and grading of fibrosis and grading respiratory and membranous bronchioles and correlation with PFTs showed a correlation with obstructive PFT abnormalities related to COPD.

Since many of these patients have clinical, functional and histologic features of COPD, the authors argue that "only restrictive or mixed restrictive/obstructive patterns, or (less certainly) a markedly reduced diffusing capacity in the absence of significant airflow obstruction, allow the diagnosis of RBILD."  (with the presence of RB histologic features described above on biopsy).

Churg A, Muller NL, Wright JL.  Respiratory bronchiolitis/interstitial lung disease.  Arch Pathol Lab Med 2010;134:27-32.