Intratracheal gene transfer of decorin reduces subpleural fibroproliferation induced by bleomycin

Gene therapy strategies for idiopathic pulmonary fibrosis: recent advances, current challenges, and future directions

Idiopathic pulmonary fibrosis (IPF) is a chronic disease in which the lungs become irreversibly scarred, leading to declining lung function. As currently available drugs do not cure IPF, there remains a great medical need for more effective treatments. Perhaps this need could be addressed by gene therapies, which offer powerful and versatile ways to attenuate a wide range of processes involved in fibrosis. Despite the potential benefits of gene therapy, no one has reviewed the current state of knowledge regarding its application for treating IPF. We therefore analyzed publications that reported the use of gene therapies to treat pulmonary fibrosis in animals, as clinical studies have not been published yet. In this review, we first provide an introduction on the pathophysiology of IPF and the most well-established gene therapy approaches. We then present a comprehensive evaluation of published animal studies, after which we provide recommendations for future research to address challenges with respect to the selection and use of animal models as well as the development of delivery vectors and dosage forms. Addressing these considerations will bring gene therapies one step closer to clinical testing and thus closer to patients.

Serum decorin is a potential prognostic biomarker in patients with acute exacerbation of idiopathic pulmonary fibrosis

Background

Decorin is a small leucine-rich repeat proteoglycan that plays a critical role in collagen fibrillogenesis, and regulates inflammation, wound healing and angiogenesis. In idiopathic pulmonary fibrosis (IPF), decorin is expressed in fibrotic lesions; furthermore, intratracheal gene transfer of decorin has been demonstrated to inhibit bleomycin-induced pulmonary fibrosis. Although these results suggest the critical role of decorin in pulmonary fibrosis, the role of decorin in the acute exacerbation of idiopathic interstitial pneumonia (AE-IIP) has not been clarified in detail. Thus, the goal of this study was to determine the role of decorin in AE-IIP.

Methods

We retrospectively analyzed AE-IIP patients who had been admitted to our hospital. First, serum decorin levels were compared among patients with AE-IIP, patients with stable idiopathic interstitial pneumonia (SD-IIP), and healthy subjects. Next, the relationship between serum decorin levels and clinical parameters was analyzed in AE-IIP patients. Finally, the association between serum decorin levels and prognosis was evaluated in AE-IIP patients. IIP was divided into IPF and non-IPF, according to the published guidelines.

Results

The serum decorin levels of AE-IIP patients were significantly lower than those of both healthy subjects and SD-IIP patients. Serum decorin levels were not related with the clinical parameters and prognosis, when all IIP patients were analyzed. In IPF patients, serum decorin levels had a significant correlation with oxygenation, and IPF patients with low serum decorin levels had a significantly higher survival rate than those with high serum decorin levels.

Conclusions

Serum decorin levels are a potential prognostic biomarker in AE-IPF.

Matrix Remodeling in Pulmonary Fibrosis and Emphysema

Pulmonary fibrosis and emphysema are chronic lung diseases characterized by a progressive decline in lung function, resulting in significant morbidity and mortality. A hallmark of these diseases is recurrent or persistent alveolar epithelial injury, typically caused by common environmental exposures such as cigarette smoke. We propose that critical determinants of the outcome of the injury-repair processes that result in fibrosis versus emphysema are mesenchymal cell fate and associated extracellular matrix dynamics. In this review, we explore the concept that regulation of mesenchymal cells under the influence of soluble factors, in particular transforming growth factor-β1, and the extracellular matrix determine the divergent tissue remodeling responses seen in pulmonary fibrosis and emphysema.

Glaucocalyxin A improves survival in bleomycin-induced pulmonary fibrosis in mice

Idiopathic pulmonary fibrosis (IPF) is a progressive interstitial lung disease with unclear etiology and poor prognosis. Despite numerous studies on the pathogenesis of IPF, only scant treatment options are available for the management of IPF. Glaucocalyxin A (GLA), an ent-Kaurane diterpenoid, has been demonstrated to exert anti-inflammatory, anti-neoplastic and anti-platelet activities. In this study, we evaluated the role of GLA as an anti-fibrotic agent in bleomycin-induced pulmonary fibrosis in mice and investigated the underlying mechanisms by which GLA attenuates lung fibrosis. Intraperitoneal administration of GLA (10 mg/kg) significantly reduced collagen deposition and hydroxyproline content in mouse lungs treated with bleomycin. Importantly, GLA significantly improved survival in bleomycin treated mice. In addition, GLA reduced weight loss in mice that reflects cachexia due to pulmonary fibrosis. Mechanistically, GLA alleviated the infiltration of macrophages and neutrophils in lungs, attenuated the increases of proinflammatory cytokines in lung tissue and bronchoalveolar lavage fluid, and inhibited the activation of NF-κB in fibrotic lungs induced by bleomycin. These results provide evidence that GLA can effectively ameliorate pulmonary fibrosis through the antagonism of leukocyte infiltration and proinflammatory cytokine production, suggesting that it may become a potential anti-fibrotic agent in IPF management.

Contribution of the anaphylatoxin receptors, C3aR and C5aR, to the pathogenesis of pulmonary fibrosis

Complement activation, an integral arm of innate immunity, may be the critical link to the pathogenesis of idiopathic pulmonary fibrosis (IPF). Whereas we have previously reported elevated anaphylatoxins-complement component 3a (C3a) and complement component 5a (C5a)-in IPF, which interact with TGF-β and augment epithelial injury in vitro, their role in IPF pathogenesis remains unclear. The objective of the current study is to determine the mechanistic role of the binding of C3a/C5a to their respective receptors (C3aR and C5aR) in the progression of lung fibrosis. In normal primary human fetal lung fibroblasts, C3a and C5a induces mesenchymal activation, matrix synthesis, and the expression of their respective receptors. We investigated the role of C3aR and C5aR in lung fibrosis by using bleomycin-injured mice with fibrotic lungs, elevated local C3a and C5a, and overexpression of their receptors via pharmacologic and RNA interference interventions. Histopathologic examination revealed an arrest in disease progression and attenuated lung collagen deposition (Masson's trichrome, hydroxyproline, collagen type I α 1 chain, and collagen type I α 2 chain). Pharmacologic or RNA interference-specific interventions suppressed complement activation (C3a and C5a) and soluble terminal complement complex formation (C5b-9) locally and active TGF-β1 systemically. C3aR/C5aR antagonists suppressed local mRNA expressions of tgfb2, tgfbr1/2, ltbp1/2, serpine1, tsp1, bmp1/4, pdgfbb, igf1, but restored the proteoglycan, dcn Clinically, compared with pathologically normal human subjects, patients with IPF presented local induction of C5aR, local and systemic induction of soluble C5b-9, and amplified expression of C3aR/C5aR in lesions. The blockade of C3aR and C5aR arrested the progression of fibrosis by attenuating local complement activation and TGF-β/bone morphologic protein signaling as well as restoring decorin, which suggests a promising therapeutic strategy for patients with IPF.-Gu, H., Fisher, A. J., Mickler, E. A., Duerson, F., III, Cummings, O. W., Peters-Golden, M., Twigg, H. L., III, Woodruff, T. M., Wilkes, D. S., Vittal, R. Contribution of the anaphylatoxin receptors, C3aR and C5aR, to the pathogenesis of pulmonary fibrosis.

Co-transfection of decorin and interleukin-10 modulates pro-fibrotic extracellular matrix gene expression in human tenocyte culture

Extracellular matrix synthesis and remodelling are driven by increased activity of transforming growth factor beta 1 (TGF-β1). In tendon tissue repair, increased activity of TGF-β1 leads to progressive fibrosis. Decorin (DCN) and interleukin 10 (IL-10) antagonise pathological collagen synthesis by exerting a neutralising effect via downregulation of TGF-β1. Herein, we report that the delivery of DCN and IL-10 transgenes from a collagen hydrogel system supresses the constitutive expression of TGF-β1 and a range of pro-fibrotic extracellular matrix genes.

Transforming growth factor-β1 small interfering RNA inhibits growth of human embryonic lung fibroblast HFL-I cells in vitro and defends against radiation-induced lung injury in vivo

In the present study, a human transforming growth factor‑β1 (TGF‑β1) small interfering RNA (siRNA) plasmid vector (TGF‑β1‑siRNA) was constructed to investigate its effects on the proliferation and differentiation of human lung fibroblasts in vitro and its interference effects on radiation‑induced lung injury in vivo. Reverse transcription quantitative polymerase chain reaction and enzyme linked immunosorbent assay revealed that the mRNA and protein expression of TGF‑β1 in the HFL‑I cells were inhibited by TGF‑β1‑siRNA and flow cytometry demonstrated a significant increase in apoptosis of the HFL‑I cells. Adult, female, specific‑pathogen‑free C57BL/6 mice were used in the in vivo animal investigations and were randomly divided into the four following groups: control without any treatment, radiation alone, radiation followed by empty vector transfection and radiation followed by TGF‑β1‑siRNA vector transfection. Hematoxylin and eosin and Van‑Gieson staining revealed that certain radiation‑induced histopathological changes of the lung, including inflammation, edema, the density of surface pulmonary interstitial collagen fibers in the alveolar septum, TGF‑β1‑positive reactions in alveolar epithelial cells and pulmonary interstitial macrophages were less marked in the mice transfected with TGF‑β1‑siRNA compared with the mice without transfection or those transfected with empty vectors. The serum levels of TGF‑β1 levels in the irradiated mice increased significantly at four weeks and peaked at eight weeks after radiation, compared with the control. Serum levels of TGF‑β1 in the irradiated mice transfected with TGF‑β1‑siRNA also increased gradually and a significant difference was observed compared with those irradiated without transfection. The mRNA expression levels of TGF‑β1 in the mice transfected with TGF‑β1‑siRNA were markedly lower compared with those of the other radiation groups. The present study suggested that the TGF‑β1‑siRNA vector reduced the activity of TGF‑β1 by downregulating the mRNA expression of TGF‑β1 and thereby effectively suppressing inflammatory reactions and defending against radiation‑induced lung injury.

Key roles for the small leucine-rich proteoglycans in renal and pulmonary pathophysiology

BACKGROUND

Small leucine-rich proteoglycans (SLRPs) are molecules that have signaling roles in a multitude of biological processes. In this respect, SLRPs play key roles in the evolution of a variety of diseases throughout the human body.

SCOPE OF REVIEW

We will critically review current developments in the roles of SLRPs in several types of disease of the kidney and lungs. Particular emphasis will be given to the roles of decorin and biglycan, the best characterized members of the SLRP gene family.

MAJOR CONCLUSIONS

In both renal and pulmonary disorders, SLRPs are essential elements that regulate several pathophysiological processes including fibrosis, inflammation and tumor progression. Decorin has remarkable antifibrotic and antitumorigenic properties and is considered a valuable potential treatment of these diseases. Biglycan can modulate inflammatory processes in lung and renal inflammation and is a potential target in the treatment of inflammatory conditions.

GENERAL SIGNIFICANCE

SLRPs can serve as either treatment targets or as potential treatment in renal or lung disease. This article is part of a Special Issue entitled Matrix-mediated cell behaviour and properties.

Myofibroblasts: Biochemical and proteomic approaches to fibrosis

Fibrosis is a state, in which excess amounts of extracellular matrix are deposited in the tissue. Fibrosis can occur in various organs, including the liver, lung, kidney and heart. The progression of fibrosis involves interstitial hypercellularity, accumulation of extracellular matrix, and atrophy of epithelial structures, resulting in a loss of normal function. Myofibroblasts play a crucial role in the development and progress of fibrosis. When stimulated, myofibroblasts actively synthesize connective tissue components and cause organ fibrosis. As a result, the process and the mechanism of myofibroblast activation represent a target for antifibrotic treatment. As yet, however, an effective treatment has not been developed, and new treatment modalities are expected. Because activation of myofibroblasts is a key event during fibrosis development, there is great interest in identifying and characterizing proteins whose expression is changed after this activation. In this review, fibrosis is outlined and the role of myofibroblasts in this disorder is described. Furthermore, the search for candidate proteins to target for treatment and the prospects of antifibrotic therapy are discussed.

Decorin-PEI nanoconstruct attenuates equine corneal fibroblast differentiation

OBJECTIVE

To explore (i) the potential of polyethylenimine (PEI) nanoparticles as a vector for delivering genes into equine corneal fibroblasts (ECFs) using green fluorescent protein (GFP) marker gene, (ii) whether PEI nanoparticle-mediated decorin (DCN) gene therapy could be used to inhibit fibrosis in the equine cornea using an in vitro model.

PROCEDURE

Polyethylenimine-DNA nanoparticles were prepared at nitrogen-to-phosphate (N-P) ratio of 15 by mixing 22 kDa linear PEI and a plasmid encoding either GFP or DCN. ECFs were generated from donor corneas as previously described. Initially, GFP was introduced into ECFs using PEI nanoparticles to confirm gene delivery, then DCN was introduced to evaluate for antifibrotic effects. GFP gene delivery was confirmed with real-time qPCR and ELISA. Changes in fibrosis after DCN therapy were quantified by measuring α-smooth muscle actin (αSMA) mRNA and protein levels with qPCR, immunostaining, and immunoblotting. Cytotoxicity was determined by evaluating cell morphology, cellular viability, and TUNEL assay.

RESULTS

Polyethylenimine-green fluorescent protein-treated cultures showed 2.2 × 10(4) GFP plasmid copies/μg of cellular DNA and 2.1 pg of GFP/100 μL of lysate. PEI-DCN delivery significantly attenuated TGFβ-induced transdifferentiation of fibroblasts to myofibroblasts (2-fold decrease of αSMA mRNA; P = 0.05) and significant inhibition of αSMA (49 ± 14.2%; P < 0.001) in immunocytochemical staining and immunoblotting were found. Furthermore, PEI-DNA nanoparticle delivery did not alter cellular phenotype at 24 h and cellular viability was maintained.

CONCLUSIONS

Twenty-two kilo dalton Polyethylenimine nanoparticles are safe and effective for equine corneal gene therapy in vitro. PEI-mediated DCN gene delivery is effective at inhibiting TGFβ-mediated fibrosis in this model.

Altered expression of tight junction molecules in alveolar septa in lung injury and fibrosis

The dysfunction of alveolar barriers is a critical factor in the development of lung injury and subsequent fibrosis, but the underlying molecular mechanisms remain poorly understood. To clarify the pathogenic roles of tight junctions in lung injury and fibrosis, we examined the altered expression of claudins, the major components of tight junctions, in the lungs of disease models with pulmonary fibrosis. Among the 24 known claudins, claudin-1, claudin-3, claudin-4, claudin-7, and claudin-10 were identified as components of airway tight junctions. Claudin-5 and claudin-18 were identified as components of alveolar tight junctions and were expressed in endothelial and alveolar epithelial cells, respectively. In experimental bleomycin-induced lung injury, the levels of mRNA encoding tight junction proteins were reduced, particularly those of claudin-18. The integrity of the epithelial tight junctions was disturbed in the fibrotic lesions 14 days after the intraperitoneal instillation of bleomycin. These results suggest that bleomycin mainly injured alveolar epithelial cells and impaired alveolar barrier function. In addition, we analyzed the influence of transforming growth factor-β (TGF-β), a critical mediator of pulmonary fibrosis that is upregulated after bleomycin-induced lung injury, on tight junctions in vitro. The addition of TGF-β decreased the expression of claudin-5 in human umbilical vein endothelial cells and disrupted the tight junctions of epithelial cells (A549). These results suggest that bleomycin-induced lung injury causes pathogenic alterations in tight junctions and that such alterations seem to be induced by TGF-β.

Significant inhibition of corneal scarring in vivo with tissue-selective, targeted AAV5 decorin gene therapy

PURPOSE

This study tested a hypothesis that tissue-selective targeted decorin gene therapy delivered to the stroma with adeno-associated virus serotype 5 (AAV5) inhibits corneal fibrosis in vivo without significant side effects.

METHODS

An in vivo rabbit model of corneal fibrosis was used. Targeted decorin gene therapy was delivered to the rabbit cornea by a single topical application of AAV5 (100 μL; 6.5 × 10(12) μg/mL) onto the bare stroma for 2 minutes. The levels of corneal fibrosis were determined with stereomicroscopy, slit lamp biomicroscopy, α-smooth muscle actin (αSMA), fibronectin, and F-actin immunocytochemistry, and/or immunoblotting. CD11b, F4/80 immunocytochemistry, and TUNEL assay were used to examine immunogenicity and cytotoxicity of AAV5 to the cornea. Transmission electron microscopy (TEM) was used to investigate ultrastructural features. Slot-blot-quantified the copy number of AAV5-delivered decorin genes.

RESULTS

Selective decorin delivery into the stroma showed a significant (P < 0.01) decrease in corneal haze (1.3 ± 0.3) compared with the no-decorin-delivered control rabbit corneas (3 ± 0.4) quantified using slit lamp biomicroscopy. Immunostaining and immunoblot analyses detected significantly reduced levels of αSMA, F-actin, and fibronectin proteins (59%-73%; P < 0.001 or <0.01) in decorin-delivered rabbit corneas compared with the no-decorin-delivered controls. The visual clinical eye examination, slit lamp clinical studies, TUNEL, CD11b, and F4/80 assays revealed that AAV5-mediated decorin gene therapy is nonimmunogenic and nontoxic for the cornea. TEM studies suggested that decorin gene delivery does not jeopardize collagen fibrillogenesis as no significant differences in collagen fibril diameter and arrangement were observed in decorin-delivered and no-decorin-delivered control corneas.

CONCLUSIONS

Tissue-targeted AAV5-mediated decorin gene therapy is effective and safe for treating corneal fibrosis in vivo.

Transforming growth factor-beta upregulates the expression of integrin and related proteins in MRC-5 human myofibroblasts

Myofibroblasts are defined as fibroblasts that express certain features of smooth muscle differentiation. Activation of myofibroblasts plays a central role in fibrosis. Transforming growth factor-beta (TGF-beta) is a potent activator of myofibroblasts; namely, TGF-beta causes changes in myofibroblast phenotypes including morphological alterations and the expression of alpha-smooth muscle actin (alpha-SMA), a marker of myofibroblasts. Because it has been well known that humoral factors, especially, TGF-beta, and extracellular matrix components cause myofibroblast activation, we examined the expression of integrin and related proteins during activation of MRC-5 human myofibroblasts with TGF-beta. Western blot analysis revealed that TGF-beta treatment for 3 days increased the expression of alpha-SMA, which was also immunocytochemically observed as actin stress fibers. In the early phase of TGF-beta treatment, fibronectin expression was greatly increased, followed by the increased expression of integrin alphav and alpha11 and integrin beta1 and beta3. Co-immunoprecipitation assays revealed that the integrin alphav subunit was co-precipitated with integrin beta1 and beta3, and that integrin beta1 was co-precipitated with alpha11, alphav, alpha2, and alpha5. The expression of focal adhesion kinase and integrin-linked kinase proteins was also upregulated by treatment with TGF-beta. In addition, the expression of type I collagen mRNA was increased by TGF-beta, but not type III collagen mRNA, as judged by real-time PCR analysis. These results suggest the possibility that TGF-beta induces fibronectin expression in MRC-5 cells, which subsequently induces the expression of integrin receptors, alphavbeta3, alphavbeta1, and alpha11beta1. This report also shows that expression of integrin alpha11 is upregulated during the TGF-beta-mediated activation of myofibroblasts.

TGF-β: Titan of Lung Fibrogenesis

Pulmonary fibrosis is characterized by epithelial cell injury, accumulation of myofibroblasts, and excessive deposition of collagen and other extracellular matrix elements, leading to loss of pulmonary function. Studies in both humans and animal models strongly suggest that TGF-β1 plays a pivotal role in the pathogenesis of pulmonary fibrosis. This review will first give an overview of TGF-β signaling and the effects of its inhibition on lung fibrogenesis. This overview includes information on TGF-β signal transduction pathways, the importance of TGF-β in the accumulation of myofibroblasts, the role of TGF-β in epithelial injury and apoptosis, the role of TGF-β in extracellular matrix remodeling, and the effects of inhibiting TGF-β signaling in animal models of lung fibrosis. Subsequently this review will highlight recent advances in two areas of particular interest to our research group: (1) TGF-β and proteoglycans; (2) TGF-β and histone deacetylases. Although our understanding of the role of TGF-β and its mechanisms of action in lung fibrogenesis has increased dramatically in recent years, there is still much to be learned about this important molecule, especially how TGF-β function is modulated in vivo, and its complex interactions with other factors expressed during lung injury and repair. Research in these areas will help identify novel therapeutic targets for the treatment of pulmonary fibrosis that will hopefully improve the prognosis of this devastating illness.

Decorin transfection suppresses profibrogenic genes and myofibroblast formation in human corneal fibroblasts

Decorin, a small leucine-rich proteoglycan, is a natural inhibitor of transforming growth factor beta (TGFbeta). Myofibroblast and haze formation in the cornea have been attributed to TGFbeta hyperactivity released from corneal epithelium following injury to eye. This study tested the hypothesis that decorin-gene transfer inhibits TGFbeta-driven myofibroblast and haze formation in the cornea. Human corneal fibroblast (HSF) cultures generated from donor human corneas were used. Decorin cDNA was cloned into mammalian expression vector. Restriction enzyme analysis and DNA sequencing confirmed the nucleotide sequence of generated vector construct. The decorin gene cloned into mammalian expression vector was introduced into HSF with lipofectamine transfection kit. Expression of decorin in selected clones was characterized with RT-PCR, immunocytochemistry and western blotting. Phage contrast microscopy and trypan blue exclusion assay evaluated the effects of decorin-gene transfer on HSF phenotype and viability, respectively. Real-time PCR, western blot and immunocytochemistry were used to analyze inhibitory effects of decorin-gene transfer on TGFbeta-induced myofibroblast formation by measuring differential expression of alpha smooth muscle actin (SMA), a myofibroblast marker, mRNA and protein expression. Analysis of variance (ANOVA) and the Bonferroni-Dunn adjustment for repeated measures were used for statistical analysis. Our data indicate that decorin-gene transfer into HSF do not alter cellular phenotype or viability. Decorin over-expressing HSF clones grown in the presence of TGFbeta1 under serum-free conditions showed a statistically significant 80-83% decrease in SMA expression (p value < 0.01) compared to naked-vector transfected clones or un-transfected HSF controls. Decorin-transfected, naked-vector transfected and un-transfected HSF grown in the absence of TGFbeta1 showed no or extremely low expression of SMA. Furthermore, decorin over-expression did not affect HSF phenotype and decreased TGFbeta-induced RNA levels of profibrogenic genes such as fibronectin, collagen type I, III, and IV that play important role in stromal matrix modulation and corneal wound healing. The results of study suggest that decorin-gene transfer effectively prevents TGFbeta-driven transformation of keratocyte and corneal fibroblast to myofibroblasts. We postulate that decorin-gene therapy can be used to treat corneal haze in vivo.

Autologous synovial fluid enhances migration of mesenchymal stem cells from synovium of osteoarthritis patients in tissue culture system

Synovial fluid from osteoarthritic knee contains mesenchymal stem cells (MSCs). One of the possible reservoirs of MSCs in synovial fluid is synovial tissue, and synovial fluid may induce mobilization of MSCs into synovial fluid in osteoarthritis patients. Here, we investigated whether synovial fluid expanded synovial MSCs in a tissue culture system. Human synovium and synovial fluid were obtained from osteoarthritis patients during total knee arthroplasties. In the tissue culture system, autologous synovial fluid expanded synovial cells statistically higher than alpha MEM + FBS, and the addition of TGF beta 3 to alpha MEM + FBS increased expansion to a similar level in all 11 donors. The addition of decorin or anti-TGFbeta neutralizing antibody to synovial fluid partially inhibited synovial cell expansion. In cell culture assay, synovial fluid proliferated synovial cells fewer than alpha MEM + FBS. The expanded synovial cells in synovial fluid retained multipotentiality and showed surface markers similar to those of MSCs. We demonstrated that autologous synovial fluid enhanced expansion of MSCs in tissue culture of synovium from osteoarthritis patients by promoting cell migration. This effect was partially affected by TGFbeta.

The role of the receptor for advanced glycation end-products in lung fibrosis

The pathogenesis of pulmonary fibrosis remains unclear. The receptor for advanced glycation end-products (RAGE) is a multi-ligand receptor known to be involved in the process of fibrotic change in several organs, such as peritoneal fibrosis and kidney fibrosis. The aim of this study was to examine the contribution of RAGE during the acute inflammation and chronic fibrotic phases of lung injury induced by intratracheal instillation of bleomycin in mice. Bleomycin-induced lung fibrosis was evaluated in wild-type and RAGE-deficient (RAGE-/-) mice. Bleomycin administration to wild-type mice caused an initial pneumonitis that evolved into fibrosis. While RAGE-/- mice developed a similar early inflammatory response, the mice were largely protected from the late fibrotic effects of bleomycin. The protection afforded by RAGE deficiency was accompanied by reduced pulmonary levels of the potent RAGE-inducible profibrotic cytokines transforming growth factor (TGF)-beta and PDGF. In addition, bleomycin administration induced high mobility group box 1 (HMGB-1) production, one of the ligands of RAGE, from inflammatory cells that accumulated within the air space. Coculture with HMGB-1 induced epithelial-mesenchymal transition (EMT) in alveolar type II epithelial cells from wild-type mice. However, alveolar type II epithelial cells derived from RAGE-/- mice did not respond to HMGB-1 treatment, such that the RAGE/HMGB-1 axis may play an important role in EMT. Also, bleomycin administration induced profibrotic cytokines TGF-beta and PDGF only in wild-type mouse lungs. Our results suggested that RAGE contributes to bleomycin-induced lung fibrosis through EMT and profibrotic cytokine production. Thus, RAGE may be a new therapeutic target for pulmonary fibrosis.

The bleomycin animal model: a useful tool to investigate treatment options for idiopathic pulmonary fibrosis?

Different animal models of pulmonary fibrosis have been developed to investigate potential therapies for idiopathic pulmonary fibrosis (IPF). The most common is the bleomycin model in rodents (mouse, rat and hamster). Over the years, numerous agents have been shown to inhibit fibrosis in this model. However, to date none of these compounds are used in the clinical management of IPF and none has shown a comparable antifibrotic effect in humans. We performed a systematic review of publications on drug efficacy studies in the bleomycin model to evaluate the value of this model regarding transferability to clinical use. Between 1980 and 2006 we identified 240 experimental studies describing beneficial antifibrotic compounds in the bleomycin model. 222 of those used a preventive regimen (drug given < or =7 days after last bleomycin application), only 13 were therapeutic trials (>7 days after last bleomycin application). In 5 studies we did not find enough details about the timing of drug application to allow inter-study comparison. It is critical to distinguish between drugs interfering with the inflammatory and early fibrogenic response from those preventing progression of fibrosis, the latter likely much more meaningful for clinical application. All potential antifibrotic compounds should be evaluated in the phase of established fibrosis rather than in the early period of bleomycin-induced inflammation for assessment of its antifibrotic properties. Further care should be taken in extrapolation of drugs successfully tested in the bleomycin model due to partial reversibility of bleomycin-induced fibrosis over time. The use of alternative and more robust animal models, which better reflect human IPF, is warranted.

Functional expression of mouse relaxin and mouse relaxin-3 in the lung from an Ebola virus glycoprotein-pseudotyped lentivirus via tracheal delivery

The peptide hormone relaxin is a known modulator of connective tissue and the extracellular matrix by virtue of its ability to regulate matrix metalloproteinases (MMPs). Relaxin knockout mice exhibit age-related pulmonary fibrosis, and delivery of recombinant human H2 relaxin ameliorates fibrotic-like conditions in the mouse lung. We investigated whether lentiviral vectors (LVs) engineering the expression of murine relaxins could induce MMP activity in the mouse lung. Mouse relaxin and mouse relaxin-3 peptides engineered by recombinant LVs were biologically active as shown by stimulation of cAMP from both THP-1 and 293T cells stably expressing relaxin receptor LGR7 and by up-regulation of MMP-2 activity from primary C57BL/6 lung cell cultures. To provide the virions with enhanced tropism for the lung, LVs were pseudotyped with the Zaire strain of the Ebola virus glycoprotein (EboZ GP) and delivered by endotracheal intubation. LVs engineering luciferase pseudotyped with EboZ GP, but not with vesicular stomatitis virus glycoprotein resulted in successful LV transduction and transgene expression in C57BL/6 mouse lung by as early as d 4. Mice treated via tracheal delivery with EboZ GP pseudotyped LVs that engineered expression of mouse relaxins exhibited increased MMP-2 and MMP-9 activity in lung tissue up until the end of our study at d 21. Taken together, this study provides proof-of- principle that relaxin gene expression targeted to the mouse lungs can result in enhanced MMP activity offering potential for alleviating disease conditions characterized by dysregulation of extracellular matrix protein accumulation.

Emerging drugs for idiopathic pulmonary fibrosis

Pulmonary fibrosis is often the end stage of chronic, persistent, low-level lung injury, either of known or unknown cause. The most severe form of pulmonary fibrosis is idiopathic pulmonary fibrosis (IPF), a disease process of unknown aetiology and one that often leads to respiratory failure and death. At present there are no proven or effective drug therapies for IPF. Recent advances in understanding of disease pathogenesis have focused attention on drug targeting of fibrogenic pathways, as opposed to traditional anti-inflammatory approaches. In this report, the present status of drug development of a number of emerging antifibrotic strategies and agents that may prove more effective in the therapy of this progressive, debilitating and fatal disease are reviewed.

Attenuation of bleomycin-induced pulmonary fibrosis by follistatin

RATIONALE

Activins are members of the transforming growth factor-beta superfamily thought to be involved in repair processes after tissue injury.

OBJECTIVES

The aim of this study was to clarify whether activin and its antagonist, follistatin, played a significant role in lung injury and fibrosis.

METHODS AND RESULTS

In bleomycin (BLM)-treated rat lung, mRNA for the beta(A) subunit of activin was upregulated on Days 3 and 7 and decreased gradually thereafter. Immunoreactive activin A was abundantly expressed in macrophages infiltrated in the lung, and was detected in fibroblasts accumulated in the fibrotic area on Day 28. We then administered follistatin, an activin antagonist, to BLM-treated rats. Follistatin significantly reduced the number of macrophages and neutrophils in bronchoalveolar lavage and reduced the protein content. Histologically, follistatin markedly reduced the number of infiltrating cells, ameliorated the destruction of lung architecture on Day 7, and attenuated lung fibrosis on Day 28. The hydroxyproline content was significantly lower in follistatin-treated rats. In cultured lung fibroblasts, production of activin A was augmented by transforming growth factor-beta, and activin antagonist follistatin significantly inhibited transforming growth factor-beta-induced fibroblast activation. These results suggest that activin A was produced in the lung after BLM treatment and promoted acute inflammation and subsequent fibrosis.

CONCLUSIONS

Follistatin is effective in treating acute lung injury and BLM-induced fibrosis by blocking the actions of activin and transforming growth factor-beta.

Global gene annotation analysis and transcriptional profiling identify key biological modules in hypoxic pulmonary hypertension

Chronic hypoxic pulmonary hypertension is an important clinical disorder causing significant morbidity. Despite recent discoveries, many molecular mechanisms involved in its pathogenesis remain unexplored. We have undertaken a systematic and unbiased approach to gain global insights into this complex process. By combining transcriptional profiling with rigorous statistical methods and cluster analysis, we identified the dominant temporal patterns of gene expression during progression and regression of hypoxic pulmonary hypertension. We next integrated these results with global gene annotation analysis to identify key biological themes involved in the development and resolution of hypoxic pulmonary hypertension and vascular remodeling. This novel approach assigned biological roles to thousands of candidate genes based on their temporal expression profiles and membership in specific biological modules. Our procedure confirmed several molecular pathways and gene products known to be important in hypoxic pulmonary hypertension. Furthermore, we discovered several novel candidates and molecular mechanisms, including IQ motif containing GTPase-activating protein-1 (IQGAP1), decorin, insulin-like growth factor binding protein-3 (IGFBP3), and lactotransferrin, that may play crucial roles in hypoxic pulmonary hypertension and vascular remodeling. Our methodology of integrating transcriptional profiling, cluster analysis, and global gene annotation provides new insights into the pathophysiology of pulmonary hypertension and is applicable to other models of human disease.

Purification and characterization of decorin from the culture media of MRC-5 cells

Myofibroblasts play an important role in fibrogenesis. Myofibroblasts secrete several components of the extracellular matrix, including decorin. To clarify the properties of decorin synthesized by myofibroblasts, we have purified and characterized decorin secreted into culture medium by the myofibroblast cell line MRC-5. Decorin was purified by successive chromatography steps using Hitrap Q and Superdex 200. Purified decorin showed a broad band on SDS-polyacrylamide gel electrophoresis, which was resolved into two smaller molecular weight bands after digestion with chondroitinase ABC. Further digestion with N-glycanase resolved these two bands into a single band, indicating that the N-glycation pattern of decorin is heterogeneous. The N-terminal amino acid sequence analysis of the purified protein and its reactivity towards an antibody raised against a C-terminal peptide of decorin indicate that MRC-5 cells secrete full-length decorin into the culture medium. To characterize the glycosaminoglycan chains attached to decorin, glycosaminoglycans from the purified protein were treated with chondroitinase ACI, chondroitinase ACII, chondroitinase ABC and chondroitinase B. The resulting disaccharides were analyzed by chromatography, which indicated that decorin secreted by MRC-5 cells is a dermatan sulfate proteoglycan. In conclusion, the decorin secreted by MRC-5 cells has similar characteristics to the decorin expressed in several tissues. Thus, culturing MRC-5 cells may be highly useful for studying the role of decorin and myofibroblasts in fibrosis.

Gene delivery systems—gene therapy vectors for cystic fibrosis

Gene delivery systems (GDS) play a central role in the development of gene therapy strategies for Cystic Fibrosis (CF). Further, these systems are important tools in studies with cultured cells and in animal models. In this review, we describe the properties of several viral and synthetic gene delivery systems, and evaluate their possible application in gene therapy of CF. While many gene delivery systems give satisfactory results in cultured or animal studies, none of these systems has been shown to fulfil all the requirements of safety and efficacy for use in CF patients. The intact airway epithelium, the most important target in CF gene therapy, proves to be well protected against invading vector systems.

Dry eye as a major complication associated with chronic graft-versus-host disease after hematopoietic stem cell transplantation

PURPOSE

To review the condition of dry eye associated with chronic graft-versus-host disease (GVHD).

METHODS

The immunopathogenic processes and therapeutic options for lacrimal gland chronic GVHD are discussed.

RESULTS

Dry eye is the most frequent ocular complication after hematopoietic stem cell transplantation. The condition typically occurs around 6 months post-operation and is recognized as a complication of chronic GVHD. Lacrimal gland specimens from patients with dry eye show prominent fibrosis and an increase in CD34+ stromal fibroblasts in the glandular interstitium in addition to infiltration of T cells into the periductal areas. In periductal areas, CD4+ and CD8+ T cells colocalize with stromal fibroblasts that express the full component of surface molecules necessary for antigen presentation. These findings strongly suggest that periductal fibroblasts are involved in fibrogenic and immune processes by interacting with T cells in the lacrimal gland of patients with chronic GVHD, resulting in rapidly progressive dry eye. Current therapies for dry eye related to chronic GVHD include tear supplements and nonspecific immunosuppressants.

CONCLUSION

We report a significant role for stromal fibroblasts in the pathogenic processes of dry eye related to chronic GVHD. Although several supportive therapies can reduce the symptoms, specific therapies that suppress fibrotic and immune processes in the lacrimal glands are necessary to control dry eye associated with chronic GVHD.