Fibroblastic Foci Research Articles

Pathogenesis and New Diagnosis Guideline of Idiopathic Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive and fatal fibrotic lung disease in many patients. In spite of extensive research for many decades, the exact pathogenesis of IPF is unknown. At recent, the role of alveolar epithelial cells has been focused in the initiation of IPF in terms of epithelial-mesenchymal transition, dysregulated Wnt signaling, and activation of transforming growth factor-β (TGF-β). The resulting excess collagen deposition and destruction of lung architecture by myofibroblasts and fibroblastic foci leads to the development of IPF. IPF can be diagnosed by typical high resolution chest tomogram (HRCT) or by multidisciplinary discussion based on the new guideline published on 2010. (Korean J Med 2013;84:481-488)

Increased Lymphatic Vessel Length Is Associated With the Fibroblast Reticulum and Disease Severity in Usual Interstitial Pneumonia and Nonspecific Interstitial Pneumonia

Lymphangiogenesis responds to tissue injury as a key component of normal wound healing. The development of fibrosis in the idiopathic interstitial pneumonias may result from abnormal wound healing in response to injury. We hypothesize that increased lymphatic vessel (LV) length, a marker of lymphangiogenesis, is associated with parenchymal components of the fibroblast reticulum (organizing collagen, fibrotic collagen, and fibroblast foci), and its extent correlates with disease severity. We assessed stereologically the parenchymal structure of fibrotic lungs and its associated lymphatic network, which was highlighted immunohistochemically in age-matched samples of usual interstitial pneumonia (UIP), nonspecific interstitial pneumonia (NSIP) with FVC < 80%, COPD with a Global Initiative for Obstructive Lung Disease stage 0, and normal control lungs. LV length density, as opposed to vessel volume density, was found to be associated with organizing and fibrotic collagen density (P < .0001). Length density of LVs and the volume density of organizing and fibrotic collagen were significantly associated with severity of both % FVC (P < .001) and diffusing capacity of the lung for carbon monoxide (P < .001). Severity of disease in UIP and NSIP is associated with increased LV length and is strongly associated with components of the fibroblast reticulum, namely organizing and fibrotic collagen, which supports a pathogenic role of LVs in these two diseases. Furthermore, the absence of definable differences between UIP and NSIP suggests that LVs are a unifying mechanism for the development of fibrosis in these fibrotic lung diseases.

A Unique, Histopathologic Lesion in a Subset of Patients With Spontaneous Pneumothorax

Spontaneous pneumothorax can be idiopathic (primary), or it can occur in association with an underlying predisposing condition (secondary). Spontaneous pneumothorax may be a harbinger of an undiagnosed clinical condition, which may be associated with serious systemic abnormalities, making early recognition and diagnosis important. The pulmonary pathology of some of these disorders has not been fully elucidated. To review cases of pneumothorax in the hope of identifying pathologic features that might correlate to specific clinical syndromes. The pathology computer files at 3 hospitals were searched for all cases of spontaneous pneumothorax, primary and secondary, regardless of etiology during a 11-year period. Ninety-two cases were retrieved. Each of the cases was evaluated for reactive eosinophilic pleuritis, elastosis, pleural fibrosis, emphysema, intra-alveolar macrophages, cholesterol clefts, vasculopathy, and intraparenchymal or intrapleural cysts. Clinical information regarding asthma and smoking history, site of the pneumothorax, family history, radiographic findings, predisposing conditions, recurrence, age, and sex were extracted from the medical records. In 11 patients (12% of all the patients with spontaneous pneumothorax), a distinctive pattern of pleural fibrosis with islands of fibroblastic foci within a myxoid stroma was noted at the pleural-parenchymal interface or leading edge. These lesions correlated with a select subset of patients, consisting predominantly of young men. Our review identified a distinct pattern of pneumothorax-associated fibroblastic lesions in a subset of cases of spontaneous pneumothorax. Whether this is related to the pathogenesis of the pneumothorax remains to be elucidated.

P113 Secreted Lysyl Oxidase is Elevated in the Bronchoalveolar Lavage Fluid of Patients with Idiopathic Pulmonary Fibrosis

BackgroundIdiopathic pulmonary fibrosis (IPF) is a chronic progressive fibrotic lung disease for which there are no effective treatments. As a result the prognosis is poor, with a median survival of...

Familial Idiopathic Interstitial Pneumonia: Histopathology and Survival in 30 Patients

Familial idiopathic interstitial pneumonia (F-IIP) describes the unexplained occurrence of diffuse parenchymal lung disease in related individuals. Prevailing wisdom suggests that the histopathology of F-IIP is indistinguishable from that of idiopathic pulmonary fibrosis, namely, usual interstitial pneumonia (UIP). To define the histopathology of F-IIP in lung tissue samples. Tissue sections from 30 patients with F-IIP, enrolled in a national research program, were evaluated by 3 pulmonary pathologists using 15 predefined histopathologic features. Each feature was recorded independently before a final diagnosis was chosen from a limited list dichotomized between UIP or "not UIP." These 2 groups were then compared to survival. The consensus diagnosis for the F-IIP cohort was an unclassifiable parenchymal fibrosis (60%), with a high incidence of histopathologic honeycombing, fibroblast foci, and smooth muscle in fibrosis. Usual interstitial pneumonia, strictly defined, was identified in less than half of the F-IIP cases (range, 23%-50%). Interobserver agreement was fair (κ = 0.37) for 2 observers for the overall diagnosis of UIP. Findings unexpected in UIP were prevalent. The survival for the entire F-IIP cohort was poor, with an estimated mortality of 93% and a median age at death of 60.9 years. Subjects with UIP had a shorter survival and younger age at death. Pulmonary fibrosis was the dominant histopathology identified in our patients, but diagnostic features of UIP were seen in less than 50% of the samples. Overall survival was poor, with mortality accelerated apparently by the presence of a UIP pattern of disease.

Transbronchial biopsy is useful in predicting UIP pattern

BackgroundUsual interstitial pneumonia (UIP), is a necessary feature pathologically or radiologically for the diagnosis of idiopathic pulmonary fibrosis (IPF). The predictive value of transbronchial biopsy (TBB) in identifying UIP is currently unknown. The objective of this study is to assess the accuracy with which histopathologic criteria of usual interstitial pneumonia (UIP) can be identified in transbronchial biopsy (TBB) and to assess the usefulness of TBBx in predicting a the diagnosis of UIP pattern. We conducted a retrospective blinded and controlled analysis of TBB specimens from 40 established cases of UIP and 24 non-UIP interstitial lung diseases.ResultsAdequate TBB specimens were available in 34 UIP cases (85% of all UIP cases). TBB contained histopathologic criteria to suggest a UIP pattern (ie. at least one of three pathologic features of UIP present; patchy interstitial fibrosis, fibroblast foci, honeycomb changes) in 12 cases (30% of all UIP cases). Sensitivity, specificity, positive and negative predictive values for the two pathologists were 30% (12/40), 100% (24/24), 100% (12/12), 46% (24/52) and 30% (12/40), 92% (22/24), 86% (12/14), 55% (22/40) respectively. Kappa coefficient of agreement between pathologists was good (0.61, 95% CI 0.31-0.91). The likelihood of identifying UIP on TBB increased with the number and size of the TBB specimens.ConclusionAlthough sensitivity is low our data suggest that even modest amount of patchy interstitial fibrosis, fibroblast foci, honeycomb changes detected on TBB can be highly predictive of a UIP pattern. Conversely, the absence of UIP histopathologic criteria on TBB does not rule out UIP.

Insufficient autophagy in idiopathic pulmonary fibrosis

Autophagy, a process that helps maintain homeostatic balance between the synthesis, degradation, and recycling of organelles and proteins to meet metabolic demands, plays an important regulatory role in cellular senescence and differentiation. Here we examine the regulatory role of autophagy in idiopathic pulmonary fibrosis (IPF) pathogenesis. We test the hypothesis that epithelial cell senescence and myofibroblast differentiation are consequences of insufficient autophagy. Using biochemical evaluation of in vitro models, we find that autophagy inhibition is sufficient to induce acceleration of epithelial cell senescence and myofibroblast differentiation in lung fibroblasts. Immunohistochemical evaluation of human IPF biospecimens reveals that epithelial cells show increased cellular senescence, and both overlaying epithelial cells and fibroblasts in fibroblastic foci (FF) express both ubiquitinated proteins and p62. These findings suggest that insufficient autophagy is an underlying mechanism of both accelerated cellular senescence and myofibroblast differentiation in a cell-type-specific manner and is a promising clue for understanding the pathogenesis of IPF.

Pathologic Quantification of Connective Tissue Disease–Associated Versus Idiopathic Usual Interstitial Pneumonia

Usual interstitial pneumonia (UIP) is a common chronic interstitial pneumonitis. It can occur idiopathically (I-UIP) or in the setting of systemic connective tissue disease (CTD-UIP). Some studies suggest that CTD-UIP has a better prognosis than I-UIP. The histologic differences between CTD-UIP and I-UIP are not clearly defined. The purpose of this study was to evaluate histologic criteria that may differentiate CTD-UIP from I-UIP, including fibroblastic foci (FFs), lymphoid aggregates (LAs), and the presence of nonspecific interstitial pneumonia pattern. Thirty-five patients with histologic diagnoses of UIP were identified (27 biopsies [77%]; 8 explants [23%]). Biopsy slides were scanned and analyzed quantitatively for FF size, FF area, LA size, and LA area. Biopsy and explant slides were examined qualitatively for the presence of a nonspecific interstitial pneumonia pattern in areas away from UIP fibrosis. Results.-Of 27 biopsies, the number and size of FFs in CTD-UIP were smaller than they were in I-UIP. The number and size of LAs were larger in patients with rheumatoid arthritis than they were in patients with I-UIP. There was no interobserver variability among 3 pathologists using this quantitative system. Of 35 biopsies and explants, there was a higher prevalence of the nonspecific interstitial pneumonia pattern among patients with CTD-UIP than there was among patients with I-UIP (P = .005). Patients with CTD-UIP had fewer, smaller FFs than did patients with I-UIP, and patients with rheumatoid arthritis-UIP had more, larger LAs than did patients with I-UIP. Of importance, the coexistence of UIP and the nonspecific interstitial pneumonia patterns was one of the most salient features in distinguishing CTD-UIP from I-UIP because CTD-UIP demonstrated an increased prevalence of multilobar, cellular, nonspecific interstitial pneumonia patterns in areas away from the UIP fibrosis.

Cryptogenic Organizing Pneumonia

Organizing pneumonia (OP) is a pathological pattern defined by the characteristic presence of buds of granulation tissue within the lumen of distal pulmonary airspaces consisting of fibroblasts and myofibroblasts intermixed with loose connective matrix. This pattern is the hallmark of a clinical pathological entity, namely cryptogenic organizing pneumonia (COP) when no cause or etiologic context is found. The process of intraalveolar organization results from a sequence of alveolar injury, alveolar deposition of fibrin, and colonization of fibrin with proliferating fibroblasts. A tremendous challenge for research is represented by the analysis of features that differentiate the reversible process of OP from that of fibroblastic foci driving irreversible fibrosis in usual interstitial pneumonia because they may determine the different outcomes of COP and idiopathic pulmonary fibrosis (IPF), respectively. Three main imaging patterns of COP have been described: (1) multiple patchy alveolar opacities (typical pattern), (2) solitary focal nodule or mass (focal pattern), and (3) diffuse infiltrative opacities, although several other uncommon patterns have been reported, especially the reversed halo sign (atoll sign). Definitive diagnosis is based on (1) a suggestive clinical radiological presentation, (2) the demonstration of the characteristic pathological pattern at lung histopathology, and (3) exclusion of possible causes. Transbronchial biopsies or a transthoracic biopsy may also contribute to the pathological diagnosis. Rapid clinical and imaging improvement is obtained with corticosteroid therapy. Because of the risk of misdiagnosing alternative conditions that may mimic OP, only typical cases may be managed without histopathological confirmation, and patients should be followed with particular attention paid to any clue of alternate diagnosis, especially in case of incomplete response to treatment. Patients and clinicians must be aware of frequent relapses after stopping corticosteroid treatment.

Interstitial pneumonia associated with MPO-ANCA: Clinicopathological features of nine patients

Myeloperoxidase anti-neutrophil cytoplasmic autoantibody (MPO-ANCA) is a well known marker for small vessel vasculitis. Recent reports have demonstrated that interstitial pneumonia (IP) may rarely be associated with serum MPO-ANCA. Yet, little is known about the histological features. We reviewed surgical lung biopsy from nine patients with IP of uncertain etiology with serum MPO-ANCA. There was a male predominance (6:3) with a median age of 62.1. Histologically, eight patients presented with a usual interstitial pneumonia (UIP) pattern of pulmonary fibrosis, frequently accompanied by areas of nonspecific interstitial pneumonia (NSIP) pattern. One patient showed diffuse alveolar damage (DAD), and two patients showed mixture of UIP and DAD reflecting acute exacerbation of UIP. Microscopic honeycomb cysts were common, but fibroblastic foci were inconspicuous. The most frequent additional findings were small airway disease (9/9), and lymphoid follicles (7/9). Neither capillaritis nor vasculitis was seen in any of our cases. Three patients had microscopic hematuria, but none progressed to microscopic polyangiitis during the follow up. Mortality rate was 44% (median follow up 39.1 months). IP associated with MPO-ANCA showed characteristic histology dominated by UIP pattern. Vasculitis was not identified in our cohort, but small airways disease and lymphoid follicles were present in most cases. IP associated with MPO-ANCA may be a histologically distinctive disease from idiopathic pulmonary fibrosis. Mortality was relatively high and life threatening acute exacerbation may occur.

Lung Fibrosis, Premature Graying, and Macrocytosis

A 42-year-old woman with an 8-year history of unexplained macrocytosis (MCV 114) and mild thrombocytopaenia (105) presented with dry cough and dyspnea. She was noted to have fine inspiratory crepitations on auscultation of the chest and gray eyebrows and hair roots (Figure 1). The patient admitted to coloring her hair since she went completely gray at the age of 17. A thin section computed tomography scan of the chest demonstrated subpleural and basal predominant reticular changes and early honeycombing (Figure 2, arrowheads), and open lung biopsy confirmed usual interstitial pneumonia (Figure 3, hematoxylin and eosin, ×20) with fibroblastic foci (arrow, inset ×100) and early honeycomb change. Her peripheral blood mononuclear cell telomere length was well below the 1st percentile for her age, and Sanger sequencing confirmed a novel mutation resulting in a change from alanine to aspartic acid at position 678 in the TERT gene (Figure 4). There was no family history of lung disease; however, details were limited because the patient was adopted. Telomerase deficiency leads to progressive shortening of telomere length and premature cellular senescence, and is a recently identified cause of familial and sporadic pulmonary fibrosis, with which premature graying and hematologic abnormalities are often associated (1–4). Figure 1. Figure 2. Figure 3. Figure 4.

Pathological differentiation of chronic hypersensitivity pneumonitis from idiopathic pulmonary fibrosis/usual interstitial pneumonia

To evaluate the histological characteristics differentiating chronic hypersensitivity pneumonitis (chronic HP) with a usual interstitial pneumonia (UIP)-like pattern from idiopathic pulmonary fibrosis (IPF)/UIP. Surgical lung biopsy specimens from 22 patients with chronic HP diagnosed as having a UIP-like pattern upon histological examination and 13 patients with IPF/UIP were examined and the incidences of bronchiolitis, perilobular fibrosis, centrilobular fibrosis, bridging fibrosis, organizing pneumonia, fibroblastic foci, honeycombing, granulomas, giant cells, lymphocytic alveolitis and lymphoid follicles were compared. Bronchiolitis, centrilobular fibrosis, bridging fibrosis, organizing pneumonia, granulomas, giant cells and lymphocytic alveolitis were significantly more frequent among patients with chronic HP than among patients with IPF (all P<0.01). Centrilobular fibrosis, bridging fibrosis and organizing pneumonia, in addition to bronchiolitis, granulomas and giant cells, are characteristic features of chronic HP with a UIP-like pattern. These features are therefore important in differentiating chronic HP from IPF/UIP, as management strategies differ for the two disorders.

Hypersensitivity Pneumonia: Role of Surgical Lung Biopsy

Lung biopsy often plays a key role in identifying patients with hypersensitivity pneumonia, especially in the absence of a typical history. A 69-year-old woman with a 2-year history of unexplained dyspnea on exertion underwent surgical lung biopsy for diagnosis of diffuse lung disease thought to represent idiopathic pulmonary fibrosis. Her biopsy showed honeycomb change and fibroblast foci suggestive of usual interstitial pneumonia, but also showed areas of cellular interstitial pneumonia with chronic bronchiolitis and a pattern of granulomatous inflammation typical of hypersensitivity pneumonia. The classic features of hypersensitivity pneumonia in surgical lung biopsy are emphasized, including a bronchiolocentric cellular interstitial pneumonia, chronic bronchiolitis, and poorly formed nonnecrotizing granulomas. As illustrated in our patient, sometimes subtle histologic clues are key in separating hypersensitivity pneumonia from usual interstitial pneumonia and other forms of idiopathic interstitial pneumonia. Making the distinction is important given differences in treatment strategies and natural history.

WNT7B in fibroblastic foci of idiopathic pulmonary fibrosis

BackgroundIdiopathic pulmonary fibrosis (IPF) is a devastating interstitial pneumonia causing a loss of respiratory surface area due to a proliferative fibrotic response involving hyperplastic, hypertrophic, and metaplastic epithelium, cystic honeycomb change, septal expansion, and variable inflammation. Wnt (wingless) signaling glycoproteins are known to be involved in lung development and tissue repair, and are up-regulated in patients with IPF. Based on previous qRT-PCR data showing increased Wnt7B in lungs of IPF patients, a systematic, quantitative examination of its tissue site distribution was undertaken.MethodsTissue samples from the Lung Tissue Research Consortium (LTRC) of 39 patients diagnosed with mild to severe IPF/usual interstitial pneumonia (UIP) and 19 normal patients were examined for the immunolocalization of Wnt7B.ResultsIn normal lung, moderate Wnt7B reactivity was confined to airway epithelium, smooth muscle of airways and vasculature, and macrophages. IPF lung showed strong Wnt7B reactivity in fibroblastic foci, dysplastic airway and alveolar epithelium, and in highly discrete subepithelial, basement membrane-associated regions. All reactive sites were sized and counted relative to specific microscopic regions. Those in the subepithelial sites were found in significantly greater numbers and larger relative area compared with the others. No reactive sites were present in normal patient controls.ConclusionsThe results demonstrate Wnt7B to be expressed at high concentrations in regions of active hyperplasia, metaplasia, and fibrotic change in IPF patients. In this context and its previously established biologic activities, Wnt7B would be expected to be of potential importance in the pathogenesis of IPF.

Regulation and localization of the Telomerase- and the Shelterin-telosom-complex in sporadic Idiopathic Pulmonary Fibrosis

Introduction: Idiopathic pulmonary fibrosis (IPF) is an adult-onset, lethal, scarring lung disease of unknown etiology. Reports linking telomerase mutations to familial IPF suggest that reduced telomerase activity and defective telomere length maintenance are key factors in disease pathogenesis. Accelerated telomere shortening is also observed in sporadic IPF in the absence of gene mutations. We therefore aimed to analyze the expression of the Telomerase- [TERT,TERC,DKC1,NOP10,NHP2] and the Shelterin-telosom-complex [TERF1/-2,POT1,TIN2,PTOP,RAP1] in lungs from patients with sporadic IPF (n=30) and organ donors (n=12). Methods: Peripheral lung tissue was analyzed by RT-PCR, immunoblotting and immunohistochemistry (IHC). Results: Gene expression analysis for TERT and the telomerase RNA-component TERC by RT-PCR indicated a significant downregulation in IPF lungs. Using immunoblotting, we observed no significant differences in expression of Telomerase-/Shelterin-components in IPF- and donor lungs. Surprisingly, we could not detect any protein expression of Telomerase- and Shelterin-components in type-II cells of IPF- and donor lungs by means of conventional IHC. Instead, we observed a strong TERT expression in a subset of Clara cells (CC10-positive) in IPF- and donor lungs, and expression of POT1 (protection of telomeres1) was exclusively localized in a subset of TERT-negative Clara cells in both categories. The other Shelterin-members revealed strong expression in myofibroblasts of fibroblast foci [RAP1] and/or in basal cells at sites of aberrant bronchiolar proliferation [PTOP,TIN2,TERF2,RAP1]. Conclusion: We carefully suggest that the robust expression of TERT/POT1 in CC10-positive cells of IPF- and donor lungs might indicate a cell population with stem cell characteristics. The upregulation of Shelterin-components in myofibroblasts and/or basal cells may explain the persistence of myofibroblasts and the exaggerated proliferation of bronchiolar basal cells in IPF.

Treatments in idiopathic pulmonary fibrosis: time for a more targeted approach?

Idiopathic pulmonary fibrosis (IPF) is a progressive age-related lung disease, the cause of which is not been fully understood. IPF is a devastating disease with mortality worse than many cancers, and treatment options are limited. IPF is thought to occur after recurrent injury to the alveolar epithelium followed by abnormal repair characterized by the formation of fibroblast and myofibroblast foci and excessive deposition of extracellular matrix. An updated classification of the idiopathic interstitial pneumonias has encouraged a large number of clinical trials. On the whole, these have disappointed. Improvements in molecular techniques have developed our understanding of IPF and with it identified new pathways and potential targets for therapeutic intervention. These insights are leading to interest in biomarkers of disease progression and prognosis and to novel anti-fibrotic agents and a more targeted approach to the treatment of IPF.

Vascular dysfunction by myofibroblast activation in patients with idiopathic pulmonary fibrosis and prognostic significance

In this study, we demonstrated the importance of telomerase protein expression and determined the relationships among telomerase, endothelin-1 (ET-1) and myofibroblasts during early and late remodeling of parenchymal and vascular areas in usual interstitial pneumonia (UIP) using 27 surgical lung biopsies from patients with idiopathic pulmonary fibrosis (IPF). Telomerase+, myofibroblasts α-SMA+, smooth muscle cells caldesmon+, endothelium ET-1+ cellularity, and fibrosis severity were evaluated in 30 fields covering normal lung parenchyma, minimal fibrosis (fibroblastic foci), severe (mural) fibrosis, and vascular areas of UIP by the point-counting technique and a semiquantitative score. The impact of these markers was determined in pulmonary functional tests and follow-up until death from IPF. Telomerase and ET-1 expression was significantly increased in normal and vascular areas compared to areas of fibroblast foci. Telomerase and ET-1 expression was inversely correlated with minimal fibrosis in areas of fibroblast foci and directly associated with severe fibrosis in vascular areas. Telomerase activity in minimal fibrosis areas was directly associated with diffusing capacity of the lung for oxygen/alveolar volume and ET-1 expression and indirectly associated with diffusing capacity of the lungs for carbon monoxide and severe fibrosis in vascular areas. Cox proportional hazards regression revealed a low risk of death for females with minimal fibrosis displaying high telomerase and ET-1 expression in normal areas. Vascular dysfunction by telomerase/ET-1 expression was found earlier than vascular remodeling by myofibroblast activation in UIP with impact on IPF evolution, suggesting that strategies aimed at preventing the effect of these mediators may have a greater impact on patient outcome.

Inhibition of focal adhesion kinase prevents experimental lung fibrosis and myofibroblast formation

Enhanced adhesive signaling, including activation of focal adhesion kinase (FAK), is a hallmark of fibroblasts from lung fibrosis patients, and FAK has therefore been hypothesized to be a key mediator of this disease. This study was undertaken to characterize the contribution of FAK to the development of pulmonary fibrosis both in vivo and in vitro. FAK expression and activity were analyzed in lung tissue samples from lung fibrosis patients by immunohistochemistry. Mice orally treated with the FAK inhibitor PF-562,271, or with small interfering RNA (siRNA)-mediated silencing of FAK were exposed to intratracheally instilled bleomycin to induce lung fibrosis, and lungs were harvested for histologic and biochemical analysis. Using endothelin 1 (ET-1) as a stimulus, cell adhesion and contraction, as well as profibrotic gene expression, were studied in fibroblasts isolated from wild-type and FAK-deficient mouse embryos. ET-1-mediated FAK activation and gene expression were studied in primary mouse lung fibroblasts, as well as in wild-type and β1 integrin-deficient mouse fibroblasts. FAK expression and activity were up-regulated in fibroblast foci and remodeled vessels from lung fibrosis patients. Pharmacologic or siRNA-mediated targeting of FAK resulted in marked abrogation of bleomycin-induced lung fibrosis in mice. Loss of FAK impaired the acquisition of a profibrotic phenotype in response to ET-1. Profibrotic gene expression leading to myofibroblast differentiation required cell adhesion, and was driven by JNK activation through β1 integrin/FAK signaling. These results implicate FAK as a central mediator of fibrogenesis, and highlight this kinase as a potential therapeutic target in fibrotic diseases.

Hypermethylation‐Mediated Silencing of p14ARF in Fibroblasts from Idiopathic Pulmonary Fibrosis (IPF)

IPF is a lethal lung disease characterized by the formation and persistence of fibroblast foci and matrix accumulation. Evidence suggests that fibroblasts acquire an anti‐apoptotic phenotype and we hypothesized that epigenetic silencing of the pro‐apoptotic gene p14ARF may be involved. p14ARF expression was analyzed by RT‐PCR and Western blot in IPF and normal human lung fibroblasts. p14ARF gene promoter methylation was determined by methylation specific PCR (MS‐PCR) and by DNA digestion with endonuclease McrBc. Apoptosis was evaluated by annexin‐V and nuclear staining. p14ARF expression was significantly decreased in 4 of 8 IPF fibroblasts lines, which was restored after 5‐aza‐2′‐deoxycytidine treatment. MS‐PCR of bisulfite‐treated genomic DNA showed a correlation between the reduced expression of p14ARF and the presence of hypermethylated promoter. No amplification was observed in the DNA treated with McrBc confirming promoter hypermethylation. p14ARF hypermethylated IPF fibroblasts were more resistant to staurosporine‐induced apoptosis compared with normal and non‐methylated IPF fibroblasts (p&lt;0.01) and showed reduced levels of p53. Apoptosis resistance was induced in fibroblasts inhibiting p14ARF expression by siRNA (p&lt;0.05). These findings reveal that many IPF fibroblasts have reduced expression of p14ARF indicating that epigenetic mechanisms may cause their resistance to apoptosis.

Regulation of TGF-β storage and activation in the human idiopathic pulmonary fibrosis lung

Idiopathic pulmonary fibrosis (IPF) is a progressive disease of unknown cause. The pathogenesis of the disease is characterized by fibroblast accumulation and excessive transforming growth factor-β (TGF-β) activation. Although TGF-β activation is a complex process involving various protein interactions, little is known of the specific routes of TGF-β storage and activation in human lung. Here, we have systematically analyzed the expression of specific proteins involved in extracellular matrix targeting and activation of TGF-β. Latent TGF-β-binding protein (LTBP)-1 was found to be significantly upregulated in IPF patient lungs. LTBP-1 expression was especially high in the fibroblastic foci, in which P-Smad2 immunoreactivity, indicative of TGF-β signaling activity, was less prominent. In cultured primary lung fibroblasts and epithelial cells, short-interfering-RNA-mediated downregulation of LTBP-1 resulted in either increased or decreased TGF-β signaling activity, respectively, suggesting that LTBP-1-mediated TGF-β activation is dependent on the cellular context in the lung. Furthermore, LTBP-1 was shown to colocalize with fibronectin, fibrillin-1 and fibrillin-2 proteins in the IPF lung. Fibrillin-2, a developmental gene expressed only in blood vessels in normal adult lung, was found specifically upregulated in IPF fibroblastic foci. The TGF-β-activating integrin β8 subunit was expressed at low levels in both control and IPF lungs. Alterations in extracellular matrix composition, such as high levels of the TGF-β storage protein LTBP-1 and the re-appearance of fibrillin-2, probably modulate TGF-β availability and activation in different pulmonary compartments in the fibrotic lung.