Molecular Profiling in Lung Biopsies of Human Pulmonary Allografts to Predict Chronic Lung Allograft Dysfunction

Abstract

Chronic lung allograft dysfunction (CLAD) is the main reason for poor long-term outcome of lung transplantation, with bronchiolitis obliterans (BO) representing the predominant pathological feature. BO is defined as a progressive fibrous obliteration of the small airways, thought to be triggered by a combination of nonimmune bronchial injury and alloimmune and autoimmune mechanisms. Because biopsy samples are too insensitive to reliably detect BO and a decline in lung function test results, which is clinically used to define CLAD, does not detect early stages, there is need for alternative biomarkers for early diagnosis. Herein, we analyzed the cellular composition and differential expression of 45 tissue remodeling-associated genes in transbronchial lung biopsy specimens from two cohorts with 18 patients each: patients who did not develop CLAD within 3 years after transplantation (48 biopsy specimens) and patients rapidly developing CLAD within the first 3 postoperative years (57 biopsy specimens). Integrating the mRNA expression levels of the five most significantly dysregulated genes from the transforming growth factor-β axis (BMP4, IL6, MMP1, SMAD1, and THBS1) into a score, patient groups could be confidently separated and the outcome predicted (P < 0.001). We conclude that overexpression of fibrosis-associated genes may be valuable as a tissue-based molecular biomarker to more accurately diagnose or predict the development of CLAD.

Early extracellular matrix changes are associated with later development of bronchiolitis obliterans syndrome after lung transplantation

“…There is a strong need to investigate molecular changes leading to BOS with the aim to improve diagnostic tools and to understand pathological mechanisms, for example, by gene expression profiling and evaluation of subsets of immune-modulating cells in bronchoalveolar lavage. [9][10][11][12] We hypothesise that until now unknown triggers of BOS lead to changes in the extracellular matrix (ECM), possibly in different parts of the transplanted lung. These changes might be signs of ongoing remodelling processes that, at a later stage, lead to increased susceptibility to BOS.…”

Comparative analysis of morphological and molecular motifs in bronchiolitis obliterans and alveolar fibroelastosis after lung and stem cell transplantation

“…MMP1 is implicated in cell division, migration, differentiation and apoptosis via intracellular activity. In our own tissue-based molecular expression analyses, we recently demonstrated, in contrast to BAL analyses, an upregulation of MMP1 in TBBs of BOS patients [7,44,45]. Here, via compartmentspecific molecular expression analysis MMP1 was even more specifically localised to AFE areas.…”

“…In this context, we and others previously described a complex deregulation of a large number of mediators in transplanted and non-transplanted lungs, governing such functional areas as digestion of fibrin, macrophage recruitment and activation, vascular remodelling, epithelial-mesenchymal transition (EMT) and haemostasis, in addition to pivotal (myo)fibroblast activation and proliferation [3,8,23]. In our previous studies of BO following LuTx, we could specifically show that (i) circulating fibrocytes of the graft recipient contribute to the evolution of BO [24], (ii) lipopolysaccharides are necessary co-stimulators for the development of BO [25] (iii) a dysregulation of fibrosis-associated genes involving the transforming growth factor b (TGF-b) cascade is the hallmark of BO in explanted lung transplants and after HSCT [7,8], (iv) morphologically inconspicuous lung parenchyma adjacent to BO changes already shows pro-fibrotic gene dysregulation [8,23], (v) an overexpression of a subset of fibrosisassociated genes in transbronchial biopsies (TBB) predicts the subsequent manifestation of BOS [7].…”

Morphological and molecular motifs of fibrosing pulmonary injury patterns

“…Complementary DNA of each sample was generated from 1 μg of RNA using the High Capacity cDNA Reverse Transcription Kit (Applied Biosystems, Foster City, CA, USA) and following the manufacturer's protocol .…”