While the factors that regulate the onset and progression of idiopathic pulmonary fibrosis (IPF) are incompletely understood, recent investigations have revealed that endoplasmic reticulum (ER) ...stress and activation of the unfolded protein response (UPR) are prominent in alveolar epithelial cells in this disease. Initial observations linking ER stress and IPF were made in cases of familial interstitial pneumonia (FIP), the familial form of IPF, in a family with a mutation in surfactant protein C (SFTPC). Subsequent studies involving lung biopsy specimens revealed that ER stress markers are highly expressed in the alveolar epithelium in IPF and FIP. Recent mouse modeling has revealed that induction of ER stress in the alveolar epithelium predisposed to enhanced lung fibrosis after treatment with bleomycin, which is mediated at least in part by increased alveolar epithelial cell (AEC) apoptosis. Emerging data also indicate that ER stress in AECs could impact fibrotic remodeling by altering inflammatory responses and inducing epithelial-mesenchymal transition. Although the cause of ER stress in IPF remains unknown, common environmental exposures such as herpesviruses, inhaled particulates, and cigarette smoke induce ER stress and are candidates for contributing to AEC dysfunction by this mechanism. Together, investigations to date suggest that ER stress predisposes to AEC dysfunction and subsequent lung fibrosis. However, many questions remain regarding the role of ER stress in initiation and progression of lung fibrosis, including whether ER stress or the UPR could be targeted for therapeutic benefit.
Although in some cases clinical and radiographic features may be sufficient to establish a diagnosis of diffuse parenchymal lung disease (DPLD), surgical lung biopsy is frequently required. Recently ...a new technique for bronchoscopic lung biopsy has been developed using flexible cryo-probes. In this study we describe our clinical experience using bronchoscopic cryobiopsy for diagnosis of diffuse lung disease.
A retrospective study of subjects who had undergone bronchoscopic cryobiopsy for evaluation of DPLD at an academic tertiary care center from January 1, 2012 through January 15, 2013 was performed. The procedure was performed using a flexible bronchoscope to acquire biopsies of lung parenchyma. H&E stained biopsies were reviewed by an expert lung pathologist.
Twenty-five eligible subjects were identified. With a mean area of 64.2 mm(2), cryobiopsies were larger than that typically encountered with traditional transbronchial forceps biopsy. In 19 of the 25 subjects, a specific diagnosis was obtained. In one additional subject, biopsies demonstrating normal parenchyma were felt sufficient to exclude diffuse lung disease as a cause of dyspnea. The overall diagnostic yield of bronchoscopic cryobiopsy was 80% (20/25). The most frequent diagnosis was usual interstitial pneumonia (UIP) (n = 7). Three of the 25 subjects ultimately required surgical lung biopsy. There were no significant complications.
In patients with suspected diffuse parenchymal lung disease, bronchoscopic cryobiopsy is a promising and minimally invasive approach to obtain lung tissue with high diagnostic yield.
Evidence of endoplasmic reticulum (ER) stress has been found in lungs of patients with familial and sporadic idiopathic pulmonary fibrosis. We tested whether ER stress causes or exacerbates lung ...fibrosis by (i) conditional expression of a mutant form of surfactant protein C (L188Q SFTPC) found in familial interstitial pneumonia and (ii) intratracheal treatment with the protein misfolding agent tunicamycin. We developed transgenic mice expressing L188Q SFTPC exclusively in type II alveolar epithelium by using the Tet-On system. Expression of L188Q SFTPC induced ER stress, as determined by increased expression of heavy-chain Ig binding protein (BiP) and splicing of X-box binding protein 1 (XBP1) mRNA, but no lung fibrosis was identified in the absence of a second profibrotic stimulus. After intratracheal bleomycin, L188Q SFTPC-expressing mice developed exaggerated lung fibrosis and reduced static lung compliance compared with controls. Bleomycin-treated L188Q SFTPC mice also demonstrated increased apoptosis of alveolar epithelial cells and greater numbers of fibroblasts in the lungs. With a complementary model, intratracheal tunicamycin treatment failed to induce lung remodeling yet resulted in augmentation of bleomycin-induced fibrosis. These data support the concept that ER stress produces a dysfunctional epithelial cell phenotype that facilitates fibrotic remodeling. ER stress pathways may serve as important therapeutic targets in idiopathic pulmonary fibrosis.
Current evidence suggests a prominent role for endoplasmic reticulum (ER) stress and activation of the unfolded protein response (UPR) in fibrotic conditions affecting a number of internal organs, ...including the lungs, liver, GI tract, kidney, and heart. ER stress enhances the susceptibility of structural cells, in most cases the epithelium, to pro-fibrotic stimuli. Studies suggest that ER stress facilitates fibrotic remodeling through activation of pro-apoptotic pathways, induction of epithelial–mesenchymal transition, and promotion of inflammatory responses. While genetic mutations that lead to ER stress underlie some cases of fibrosis, including lung fibrosis secondary to mutations in surfactant protein C (SFTPC), a variety of other factors can cause ER stress. These ER stress inducing factors include metabolic abnormalities, oxidative stress, viruses, and environmental exposures. Interestingly, the ability of the ER to maintain homeostasis under stress diminishes with age, potentially contributing to the fact that fibrotic disorders increase in incidence with aging. Taken together, underlying ER stress and UPR pathways are emerging as important determinants of fibrotic remodeling in different forms of tissue fibrosis. Further work is needed to better define the mechanisms by which ER stress facilitates progressive tissue fibrosis. In addition, it remains to be seen whether targeting ER stress and the UPR could have therapeutic benefit. This article is part of a Special Issue entitled: Fibrosis: Translation of basic research to human disease.
► ER stress and the unfolded protein response contribute tofibrotic remodeling. ► ER stress enhances the susceptibility of epithelial cells to pro-fibrotic stimuli. ► ER stress facilitates fibrosis by promoting apoptosis, inflammation, and/or EMT. ► Genetic mutations, viruses, and environmental exposures may cause ER stress in vivo.
Traditional vascular grafts constructed from synthetic polymers or cadaveric human or animal tissues support the clinical need for readily available blood vessels, but often come with associated ...risks. Histopathological evaluation of these materials has shown adverse host cellular reactions and/or mechanical degradation due to insufficient or inappropriate matrix remodeling. We developed an investigational bioengineered human acellular vessel (HAV), which is currently being studied as a hemodialysis conduit in patients with end-stage renal disease. In rare cases, small samples of HAV were recovered during routine surgical interventions and used to examine the temporal and spatial pattern of the host cell response to the HAV after implantation, from 16 to 200 weeks. We observed a substantial influx of alpha smooth muscle actin (αSMA)-expressing cells into the HAV that progressively matured and circumferentially aligned in the HAV wall. These cells were supported by microvasculature initially formed by CD34
/CD31
cells in the neoadventitia and later maintained by CD34
/CD31
endothelial cells in the media and lumen of the HAV. Nestin
progenitor cells differentiated into either αSMA
or CD31
cells and may contribute to early recellularization and self-repair of the HAV. A mesenchymal stem cell-like CD90
progenitor cell population increased in number with duration of implantation. Our results suggest that host myogenic, endothelial, and progenitor cell repopulation of HAVs transforms these previously acellular vessels into functional multilayered living tissues that maintain blood transport and exhibit self-healing after cannulation injury, effectively rendering these vessels like the patient's own blood vessel.
Expression of mutant surfactant protein C (SFTPC) results in endoplasmic reticulum (ER) stress in type II alveolar epithelial cells (AECs). AECs have been implicated as a source of lung fibroblasts ...via epithelial-to-mesenchymal transition (EMT); therefore, we investigated whether ER stress contributes to EMT as a possible mechanism for fibrotic remodeling. ER stress was induced by tunicamyin administration or stable expression of mutant (L188Q) SFTPC in type II AEC lines. Both tunicamycin treatment and mutant SFTPC expression induced ER stress and the unfolded protein response. With tunicamycin or mutant SFTPC expression, phase contrast imaging revealed a change to a fibroblast-like appearance. During ER stress, expression of epithelial markers E-cadherin and Zonula occludens-1 decreased while expression of mesenchymal markers S100A4 and α-smooth muscle actin increased. Following induction of ER stress, we found activation of a number of pathways, including MAPK, Smad, β-catenin, and Src kinase. Using specific inhibitors, the combination of a Smad2/3 inhibitor (SB431542) and a Src kinase inhibitor (PP2) blocked EMT with maintenance of epithelial appearance and epithelial marker expression. Similar results were noted with siRNA targeting Smad2 and Src kinase. Together, these studies reveal that induction of ER stress leads to EMT in lung epithelial cells, suggesting possible cross-talk between Smad and Src kinase pathways. Dissecting pathways involved in ER stress-induced EMT may lead to new treatment strategies to limit fibrosis.
Autologous or synthetic vascular grafts are used routinely for providing access in hemodialysis or for arterial bypass in patients with cardiovascular disease. However, some patients either lack ...suitable autologous tissue or cannot receive synthetic grafts. Such patients could benefit from a vascular graft produced by tissue engineering. Here, we engineer vascular grafts using human allogeneic or canine smooth muscle cells grown on a tubular polyglycolic acid scaffold. Cellular material was removed with detergents to render the grafts nonimmunogenic. Mechanical properties of the human vascular grafts were similar to native human blood vessels, and the grafts could withstand long-term storage at 4 °C. Human engineered grafts were tested in a baboon model of arteriovenous access for hemodialysis. Canine grafts were tested in a dog model of peripheral and coronary artery bypass. Grafts demonstrated excellent patency and resisted dilatation, calcification, and intimal hyperplasia. Such tissue-engineered vascular grafts may provide a readily available option for patients without suitable autologous tissue or for those who are not candidates for synthetic grafts.
Animal models of fibrotic lung disease B Moore, Bethany; Lawson, William E; Oury, Tim D ...
American journal of respiratory cell and molecular biology
49, Številka:
2
Journal Article
Recenzirano
Odprti dostop
Interstitial lung fibrosis can develop as a consequence of occupational or medical exposure, as a result of genetic defects, and after trauma or acute lung injury leading to fibroproliferative acute ...respiratory distress syndrome, or it can develop in an idiopathic manner. The pathogenesis of each form of lung fibrosis remains poorly understood. They each result in a progressive loss of lung function with increasing dyspnea, and most forms ultimately result in mortality. To better understand the pathogenesis of lung fibrotic disorders, multiple animal models have been developed. This review summarizes the common and emerging models of lung fibrosis to highlight their usefulness in understanding the cell-cell and soluble mediator interactions that drive fibrotic responses. Recent advances have allowed for the development of models to study targeted injuries of Type II alveolar epithelial cells, fibroblastic autonomous effects, and targeted genetic defects. Repetitive dosing in some models has more closely mimicked the pathology of human fibrotic lung disease. We also have a much better understanding of the fact that the aged lung has increased susceptibility to fibrosis. Each of the models reviewed in this report offers a powerful tool for studying some aspect of fibrotic lung disease.
Lung fibroblasts are key mediators of fibrosis resulting in accumulation of excessive interstitial collagen and extracellular matrix, but their origins are not well defined.
We aimed to elucidate the ...contribution of lung epithelium-derived fibroblasts via epithelial-mesenchymal transition (EMT) in the intratracheal bleomycin model.
Primary type II alveolar epithelial cells were cultured from Immortomice and exposed to transforming growth factor-beta(1) and epidermal growth factor. Cell fate reporter mice that permanently mark cells of lung epithelial lineage with beta-galactosidase were developed to study EMT, and bone marrow chimeras expressing green fluorescent protein under the control of the fibroblast-associated S100A4 promoter were generated to examine bone marrow-derived fibroblasts. Mice were given intratracheal bleomycin (0.08 unit). Immunostaining was performed for S100A4, beta-galactosidase, green fluorescent protein, and alpha-smooth muscle actin.
In vitro, primary type II alveolar epithelial cells undergo phenotypic changes of EMT when exposed to transforming growth factor-beta(1) and epidermal growth factor with loss of prosurfactant protein C and E-cadherin and gain of S100A4 and type I procollagen. In vivo, using cell fate reporter mice, approximately one-third of S100A4-positive fibroblasts were derived from lung epithelium 2 weeks after bleomycin administration. From bone marrow chimera studies, one-fifth of S100A4-positive fibroblasts were derived from bone marrow at this same time point. Myofibroblasts rarely derived from EMT or bone marrow progenitors.
Both EMT and bone marrow progenitors contribute to S100A4-positive fibroblasts in bleomycin-induced lung fibrosis. However, neither origin is a principal contributor to lung myofibroblasts.
The aged population suffers increased morbidity and higher mortality in response to episodes of acute kidney injury (AKI). Aging is associated with telomere shortening, and both telomerase reverse ...transcriptase (TerT) and RNA (TerC) are essential to maintain telomere length. To define a role of telomerase deficiency in susceptibility to AKI, we used ischemia/reperfusion injury in wild-type mice or mice with either TerC or TerT deletion. Injury induced similar renal impairment at day 1 in each genotype, as assessed by azotemia, proteinuria, acute tubular injury score, and apoptotic tubular epithelial cell index. However, either TerC or TerT knockout significantly delayed recovery compared with wild-type mice. Electron microscopy showed increased autophagosome formation in renal tubular epithelial cells in wild-type mice but a significant delay of their development in TerC and TerT knockout mice. There were also impeded increases in the expression of the autophagosome marker LC3 II, prolonged accumulation of the autophagosome protein P62, an increase of the cell cycle regulator p16, and greater activation of the mammalian target of rapamycin (mTOR) pathway. The mTORC1 inhibitor, rapamycin, partially restored the ischemia/reperfusion-induced autophagy response, without a significant effect on either p16 induction or tubule epithelial cell proliferation. Thus, muting the maintenance of normal telomere length in mice impaired recovery from AKI, owing to an increase in tubule cell senescence and impairment of mTOR-mediated autophagy.
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