Formation Of Fibrotic Lesions Research Articles

Transforming growth factor-β and matrix metalloproteinases as potential biomarkers of fibrotic lesions induced by tuberculosis: a systematic review and meta-analysis

ObjectivesVery few studies and limited information are available regarding the mechanism of fibrosis in tuberculosis (TB). This study aimed to identify, describe and synthesise potential biomarkers of the development of...

149 Chronic Immunotoxicity of Multi-Walled Carbon Nanotubes on Macrophages via MMP-12

Abstract Background The toxicological effects of nanomaterials, such as multi-walled carbon nanotubes (MWCNTs), on the immune system are considerably understood. However, the precise relationship between long-term exposure to MWCNTs and chronic inflammation remains unclear. Methods and Finding In this study, exposure to Taquann-treated MWCNTs (T-CNTs) was performed using aerosols generated in an inhalation chamber. At 12 months after T-CNT exposure, alveolar inflammation with macrophage accumulation and hypertrophy of the alveolar walls were observed. The fibrotic lesions were enhanced by T-CNT exposure. The cell surface phenotype of macrophages in the bronchoalveolar lavage fluid was shifted to the M1 macrophage phenotype. In addition, the alveolar macrophages of T-CNT-exposed mice produced matrix metalloprotinase-12 (MMP-12). By contrast, a mouse model of chronic peritonitis was also established using intraperitoneal injection of T-CNTs with high dispersion efficiency. Chronic peritonitis with fibrosis was observed in T-CNT-injected mice, but not in Taquann-treated TiO2-injected mice. In vivo and in vitro experiments showed that MMP-12 of macrophages was upregulated by T-CNT to enhance fibroblast activation and profibrotic molecule expression in fibroblasts. In addition, T-CNT-induced peritonitis reduced MMP-12 expression in Nfκb1−/− mice, suggesting that MMP-12-producing macrophages play a key role in chronic inflammation due to T-CNT exposure though NF-κB activation. Conclusion These results using the two models suggest that T-MWCNT exposure promoted chronic inflammation and fibrotic lesion formation in profibrotic macrophages via MMP12 for prolonged periods. The results of this study could be helpful in understanding the molecular toxicity of nanomaterial and chronic inflammation.

The Study of Fibrotic Scar at the Long Term Spinal Cord Lesion Rats

The fibrotic lesion formation is the main deterrent at regeneration of neurons in CNS injuries. In this paper we studied fibrotic scar formation in rat corticospinal tract lesion after one year survival time. The glial scar formation and Extracellular Matrix (ECM) fibronection derived scaffolds were investigated and the fore paw reaching task was performed during this period to see whether there is any regeneration of neurons along the lesion or not

Human centenarian-associated SIRT6 mutants modulate hepatocyte metabolism and collagen deposition in multilineage hepatic 3D spheroids.

Non-alcoholic fatty liver disease (NAFLD), encompassing fatty liver and its progression into nonalcoholic steatohepatitis (NASH), fibrosis, cirrhosis, and hepatocellular carcinoma (HCC), is one of the rapidly rising health concerns worldwide. SIRT6 is an essential nuclear sirtuin that regulates numerous pathological processes including insulin resistance and inflammation, and recently it has been implicated in the amelioration of NAFLD progression. SIRT6 overexpression protects from formation of fibrotic lesions. However, the underlying molecular mechanisms are not fully delineated. Moreover, new allelic variants of SIRT6 (N308K/A313S) were recently associated with the longevity in Ashkenazi Jews by improving genome maintenance and DNA repair, suppressing transposons and killing cancer cells. Whether these new SIRT6 variants play different or enhanced roles in liver diseases is currently unknown. In this study, we aimed to clarify how these new centenarian-associated SIRT6 genetic variants affect liver metabolism and associated diseases. We present evidence that overexpression of centenarian-associated SIRT6 variants dramatically altered the metabolomic and secretomic profiles of unchallenged immortalized human hepatocytes (IHH). Most amino acids were increased in the SIRT6 N308K/A313S overexpressing IHH when compared to IHH transfected with the SIRT6 wild-type sequence. Several unsaturated fatty acids and glycerophospholipids were increased, and ceramide tended to be decreased upon SIRT6 N308K/A313S overexpression. Furthermore, we found that overexpression of SIRT6 N308K/A313S in a 3D hepatic spheroid model formed by the co-culture of human immortalized hepatocytes (IHH) and hepatic stellate cells (LX2) inhibited collagen deposition and fibrotic gene expression in absence of metabolic or dietary challenges. Hence, our findings suggest that novel longevity associated SIRT6 N308K/A313S variants could favor the prevention of NASH by altering hepatocyte proteome and lipidome.

Antifibrotic Mechanism of Piceatannol in Bleomycin-Induced Pulmonary Fibrosis in Mice.

Background: Idiopathic pulmonary fibrosis (IPF) is a progressive and fatal interstitial lung disease characterized by myofibroblast accumulation and extracellular matrix deposition, which lead to irreversible damage of the lung’s architecture and the formation of fibrotic lesions. IPF is also a sequela in serious patients with the coronavirus disease 2019 (COVID-19). The molecular mechanisms under pulmonary fibrosis remain unclear, and there is no satisfactory treatment currently available. Piceatannol (PIC) is a naturally occurring resveratrol analog found in a variety of dietary sources such as grapes, passion fruit, and white tea. It has been reported to inhibit liver fibroblast growth and exhibited various antitumor activities, although its role in pulmonary fibrosis has not been established yet. In the present study, we evaluated the anti-fibrotic role of PIC in bleomycin (BLM)-induced pulmonary fibrosis in mice. Methods: Mice with BLM-induced pulmonary fibrosis were treated with PIC, and fibrotic changes were measured by hematoxylin-eosin (H&E) staining and hydroxyproline assay. Luciferase assay, Western blot assay, histological analysis, and immunofluorescence staining were used to evaluate the effect of PIC on fibroblast activation and autophagy in mouse embryonic fibroblast cells (NIH-3T3) and human lung fibroblast cells (HFL1). The anti-fibrotic mechanisms of PIC were either confirmed in vivo. Results: Our results showed that PIC significantly alleviated the bleomycin-induced collagen deposition and myofibroblast accumulation. In vitro and in vivo studies indicated that PIC plays a role in activating autophagy in the process of anti-fibroblast activation. Further mechanism studies demonstrated that PIC can promote autophagy via inhibiting the TGF-β1-Smad3/ERK/P38 signaling pathway, which leads to a decreased number of activated myofibroblasts. Conclusion: Our study demonstrated for the first time that PIC possesses the protective effects against bleomycin-induced pulmonary fibrosis due to the direct pulmonary protective effects which enhance the effect of autophagy in vitro and in vivo and finally leads to the decreased number of activated myofibroblasts. PIC may serve as a candidate compound for pulmonary fibrosis therapy and attenuates the sequelae of SARS-COV-2 pulmonary fibrosis.

Depletion of Numb and Numblike in Murine Lung Epithelial Cells Ameliorates Bleomycin-Induced Lung Fibrosis by Inhibiting the β-Catenin Signaling Pathway.

Idiopathic pulmonary fibrosis (IPF) represents the most aggressive form of pulmonary fibrosis (PF) and is a highly debilitating disorder with a poorly understood etiology. The lung epithelium seems to play a critical role in the initiation and progression of the disease. A repeated injury of lung epithelial cells prompts type II alveolar cells to secrete pro-fibrotic cytokines, which induces differentiation of resident mesenchymal stem cells into myofibroblasts, thus promoting aberrant deposition of extracellular matrix (ECM) and formation of fibrotic lesions. Reactivation of developmental pathways such as the Wnt-β-catenin signaling cascade in lung epithelial cells plays a critical role in this process, but the underlying mechanisms are still enigmatic. Here, we demonstrate that the membrane-associated protein NUMB is required for pathological activation of β-catenin signaling in lung epithelial cells following bleomycin-induced injury. Importantly, depletion of Numb and Numblike reduces accumulation of fibrotic lesions, preserves lung functions, and increases survival rates after bleomycin treatment of mice. Mechanistically, we demonstrate that NUMB interacts with casein kinase 2 (CK2) and relies on CK2 to activate β-catenin signaling. We propose that pharmacological inhibition of NUMB signaling may represent an effective strategy for the development of novel therapeutic approaches against PF.

Mesenchymal stromal cells can repair radiation-induced pulmonary fibrosis via a DKK-1-mediated Wnt/β-catenin pathway.

Pulmonary injury occurring after thoracic radiotherapy is a main factor limiting the curative effect of radiotherapy. Robust activation of the Wnt signalling pathway induced by ionizing radiation stress plays a critical role in epithelial-mesenchymal transition (EMT) in irradiated type II alveolar epithelial cells and in the proliferation of pulmonary fibroblasts, which contributes to the formation of fibrotic lesions in irradiated lungs. The pathogenesis of radiation-induced pulmonary fibrosis could be restricted by systemic delivery of human adipose-derived mesenchymal stromal cells (Ad-MSCs), as evidenced by the inhibitory effects of Ad-MSCs on EMT in irradiated type II alveolar epithelial cells. The purpose of this study is to observe the effects of mesenchymal stromal cells (MSCs) on repairing fibrosis caused by radiation. We used western blotting and real-time PCR to observe the expression of DKK-1 in MSCs of different origins and passages. After the successful establishment of a radiation-induced lung injury model, we investigated the potency of the supernatant from stromal cells to reduce pro-fibrotic events, including EMT and fibroblast activation. To study the mechanism, we evaluated the levels of active β-catenin, TCF4 and the target genes Snail, Twistand c-Myc. After the injection of Ad-MSCs into mice via the tail vein, proteins related to EMT, fibroblasts and Wnt/β-catenin signalling were investigated. The TGF-β and IL-10 protein concentrations in peripheral blood were measured by ELISA. Ad-MSC-derived supernatant effectively reversed the decrease in E-cadherin expression and inhibited the increase in vimentin expression induced by ionizing radiation in epithelial cells and suppressed the expression of α-SMA, a mediator of fibroblast proliferation. The canonical Wnt pathway may be activated by irradiation but the nuclear localization of active β-catenin was reduced in the presence of the supernatant from Ad-MSCs. In addition, the expression of target genes involved in EMT was downregulated. Additionally, when DKK-1 in the supernatant was neutralized, all these effects were reversed. Changes in the levels of proteins related to EMT and fibroblast activation, as well as those of active β-catenin and TCF4, were similar in vivo and in vitro. The serum level of the immunosuppressive factor IL-10 was increased after radiation and was further enhanced after Ad-MSC interference for one month. In conclusion, Ad-MSCs medium can contain DKK-1 and inhibit the induction of EMT via Wnt/β-catenin signalling in vitro and in vivo.

In This Issue

HomeCirculation ResearchVol. 126, No. 2In This Issue Free AccessIn BriefPDF/EPUBAboutView PDFView EPUBSections ToolsAdd to favoritesDownload citationsTrack citationsPermissions ShareShare onFacebookTwitterLinked InMendeleyReddit Jump toFree AccessIn BriefPDF/EPUBIn This Issue Ruth Williams Ruth WilliamsRuth Williams Search for more papers by this author Originally published16 Jan 2020https://doi.org/10.1161/RES.0000000000000321Circulation Research. 2020;126:159is related toMonogenic and Polygenic Contributions to Atrial Fibrillation RiskMetabolic Remodeling Promotes Cardiac Hypertrophy by Directing Glucose to Aspartate Biosynthesisis related toActivated Endothelial TGFβ1 Signaling Promotes Venous Thrombus Nonresolution in Mice Via Endothelin-1TGFβ Signaling and Defective Thrombus Resolution (p 162)Aberrant TGFβ1 signaling is a likely driver of chronic thromboembolic pulmonary hypertension, say Bochenek et al.Download figureDownload PowerPointChronic thromboembolic pulmonary hypertension (CTEPH) is a rare, life-threatening form of pulmonary hypertension characterized by persistent blood clots in the lung arteries that ultimately result in the formation of fibrotic lesions containing irregular vasculature. The mechanisms underlying CTEPH are largely unknown, but because the cytokine TGFβ1 regulates fibrosis and angiogenesis, and because mutations affecting TGFβ1 signaling have been implicated in another form of pulmonary hypertension, Bochenek and colleagues hypothesized this factor’s involvement. Sure enough, they found that, in CTEPH patient tissue, components of the TGFβ1 pathway were upregulated, including TGFβ1 itself and endothelin-1—a vasoconstrictor and promoter of fibrosis. The team also showed that mice engineered to lack TGFβ1 in platelet cells had faster resolution of experimental thrombosis than did control animals. Furthermore, inhibition of endothelin-1 activity prevented human and mouse endothelial cells converting to a fibrotic phenotype. The results suggest the TGFβ1-to-endothelin-1 pathway plays a pathological role in CTEPH and lends supporting evidence that the clinical use of endothelin-1 receptor blockers—prescribed to some patients with CTEPH—is a worthwhile therapy.ACC2 Deletion Prevents Aspartate Synthesis(p 182)Boosting fatty acid oxidation prevents aspartate synthesis and cardiac hypertrophy, report Ritterhoff et al.Download figureDownload PowerPointCardiac hypertrophy, in which the heart and its component cells become enlarged, can be a normal physiological process to cope with increased demand—for example, in pregnancy or elite athletes—but can also be pathological—caused by high blood pressure and other cardiovascular conditions. Pathological hypertrophy is associated with a metabolic switch in the heart from primarily fatty acid-based to glucose-based. And, boosting fatty acid oxidation (FAO) can protect against hypertrophy in cultured cardiomyocytes and animals. The mechanism underlying this protection is unknown, however. Now, Ritterhoff and colleagues show that in addition to increased glucose consumption, hypertrophic rat cardiomyocytes ramp up their levels of aspartate—a molecule involved in cell growth via synthesis of nucleic acids, RNAs, and proteins. And, boosting FAO (by genetic manipulation) prevents both the aspartate rise and hypertrophy in the cells as well as in live mice. Adding aspartate to such FAO-boosted cells could reinstate the hypertrophic phenotype. The discovery of this relationship between glucose metabolism, aspartate, and FAO may inform the design of new therapies aimed at manipulating heart cell metabolism to manage hypertrophy, say the authors.Genetic Basis of Atrial Fibrillation (p 200)Choi et al examine poly-and mono-genetic predisposition to atrial fibrillation.Download figureDownload PowerPointAffecting ≈30 million individuals worldwide, atrial fibrillation (AF) is a common cardiac arrhythmia associated with an increased risk of heart failure, stroke, dementia, and death. While the condition can be idiopathic, there is also evidence of inheritance. Indeed, a quarter of patients have a parent, sibling, or child with the condition. Genome-wide association studies have identified numerous common genetic variants linked to AF, and the more of these variants a person carries, the greater the risk—referred to as their polygenic risk score (PRS). Studies of families with AF have also revealed rarer monogenic variants, such as loss-of-function (LOF) mutations in the sarcomeric gene titin (TTN). Now, Choi and colleagues look at these common polygenic and rare monogenic variants together to examine their relative contributions. Studying the genomes of 1546 AF patients and more than 41 000 controls, the team discovered a significant association between AF and rare LOF variants at TTN. Indeed, 14% of individuals with such variants had AF. However, the team also showed that while TTN variants were highly penetrant, PRS scores accounted for considerably more of the variance in AF susceptibility. Thus, the study indicates that, generally speaking, a person’s PRS is a better indicator of overall AF risk. Previous Back to top Next FiguresReferencesRelatedDetailsRelated articlesMonogenic and Polygenic Contributions to Atrial Fibrillation RiskSeung Hoan Choi, et al. Circulation Research. 2020;126:200-209Metabolic Remodeling Promotes Cardiac Hypertrophy by Directing Glucose to Aspartate BiosynthesisJulia Ritterhoff, et al. Circulation Research. 2020;126:182-196Activated Endothelial TGFβ1 Signaling Promotes Venous Thrombus Nonresolution in Mice Via Endothelin-1Magdalena L. Bochenek, et al. Circulation Research. 2020;126:162-181 January 17, 2020Vol 126, Issue 2 Advertisement Article InformationMetrics © 2020 American Heart Association, Inc.https://doi.org/10.1161/RES.0000000000000321 Originally publishedJanuary 16, 2020 PDF download Advertisement

Cigarette smoke exposure combined with lipopolysaccharides induced pulmonary fibrosis in mice

Cigarette smoke (CS) is a risk factor for pulmonary fibrosis and lipopolysaccharides (LPS) are associated with human occupational lung diseases; however, their combined role in pulmonary fibrosis remains unknown. Therefore, we investigated whether CS combined with LPS induces pulmonary fibrosis in mice. C57BL/6 mice were exposed to CS or normal air for 21 or 35 days, followed by LPS or saline instillation on day 14, 21, and 28. Lung function was tested, and lung tissues were harvested for histological and molecular analyses. Compared to the control, CS and LPS groups, the CS + LPS group showed reduced body weight and survival rate, increased respiratory resistance, decreased lung compliance, marked alveolar structure destruction, and fibrotic lesion formation. Lung tissues showed a considerable increase in IL-6, TNF-α, IL-1β, α-SMA, and TGF-β levels and collagen content. Our results indicate that cigarette smoke exposure followed by LPS in mice induces pulmonary fibrosis with pathophysiology consistent with that of human pulmonary fibrosis.

The Role of Nestin+ Mesenchymal Stem Cells (MSCs) in Bone Marrow Chronic Graft-Versus-Host Disease

Chronic graft-versus-host disease (cGVHD) is a major cause of morbidity and mortality after allogeneic hematopoietic stem cell transplantation (allo-HSCT). cGVHD is a syndrome of variable clinical features resembling autoimmune, involving not only the epithelial target tissues (skin, lung, gastrointestinal tract and liver) but also any other organ system (musculoskeletal, joint, ocular and genital tissues). Bone marrow (BM) suppression without infection is often observed in patients undergoing allo-HSCT as GVHD symptoms appear, suggesting that BM could be a target of GVHD (Yusuke S. et. al. Blood 2010). However, the BM cGVHD is rarely reported and the mechanism for BM cGVHD is still unclear. Nestin+ mesenchymal stem cells (MSCs) are capable of differentiating into cells of multiple cell lineages and involved in the formation of fibrotic lesions (Miaohua M. et. al. Cell Mol Life Sci 2016). To determine whether Nestin+ MSCs play an important role in the development of BM cGVHD. We used two murine models of cGVHD, including MHC-matched BALB/c (H-2d) recipients given B10D2 (H-2d) grafts, and MHC-mismatched BALB/c (H-2d) recipients given C57BL/6 (H-2b) grafts. We observed that BM displayed a significant increase in collagen and reticulin fibers deposition around blood vessels in cGVHD group compared to non-cGVHD group. The decreased absolute numbers of monocytes and neutrophils in the BM indicated the broad BM suppression in the cGVHD group. We further demonstrated that Nestin+MSCs located in perivascular BM niche underwent tremendous expansion in cGVHD group (p<0.001). Nestin+ MSCs in cGVHD group acquired expression of alpha smooth muscle actin (a-SMA), indicating myofibroblast differentiation. Moreover, transforming growth factor- beta1 (TGF-β1) concentrations also increased in cGVHD BM microenvironment (p<0.0001). High concentrations of TGF-β1 induced formation of Nestin+ MSC clusters and more transition from Nestin+ MSCs to a-SMA+ cells (p<0.05). Besides, expanded Nestin+ MSCs were surrounded by many macrophages and expressed high level of TGF-β1 receptor (p<0.001 and p<0.005). Taken together, these results indicate that Nestin+ MSCs participate BM cGVHD development through transition to a-SMA+ cells induced by high TGF-β1 in cGVHD microenvironment. DisclosuresZhang:National Natural Science Foundation of China (No. 81600141, No. 81770190) and Natural Science Foundation of Guangdong Province (No. 2016A030310390): Research Funding. Yang:National Natural Science Foundation of China (No. 81600141, No. 81770190) and Natural Science Foundation of Guangdong Province (No. 2016A030310390): Research Funding. Chen:National Natural Science Foundation of China (No. 81600141, No. 81770190) and Natural Science Foundation of Guangdong Province (No. 2016A030310390): Research Funding.

Role of SOD3 in silica-related lung fibrosis and pulmonary vascular remodeling

BackgroundWork-place exposure to silica dust may lead to progressive lung inflammation culminating in the development of silicosis, an irreversible condition that can be complicated by onset of pulmonary hypertension (PH). The molecular mechanisms leading to the development of PH and lung fibrosis in response to silica are not well understood. Oxidant/antioxidant imbalance in the lung may promote fibroproliferation and vascular smooth muscle proliferation, ultimately leading to the development of PH. Herein, we analyze the development of PH and lung fibrosis in mice deficient in extracellular superoxide dismutase (SOD3), an enzyme with anti-oxidant activity.MethodsPH and silicosis were induced in wild-type and Sod3−/− mice through intratracheal injection of crystalline silica at dose 0.4 g/kg. Pulmonary hypertension and lung fibrosis were characterized by changes in right ventricular systolic pressure (RVSP) and collagen deposition 28 days following silica injections. Vascular remodeling was analyzed using immunohistochemistry and morphometric analysis. The expression of genes were analyzed using qRT-PCR and Western blot.ResultsC57BL6 mice exposed to silica showed attenuated expression of Sod3 in the lung suggesting a protective role for Sod3. Consistent with this, Sod3−/− mice developed more severe fibrotic inflammatory nodules with increased collagen deposition. Furthermore, the expression of genes involved in tissue remodeling (Timp1), fibrotic lesion formation (Fsp1) and inflammatory response (Mcp1) were significantly elevated in Sod3−/− mice compared to Sod3+/+ mice treated with silica. Infiltration of neutrophils and activated macrophages into affected lung was significantly higher in Sod3 deficient mice. In addition, silica produced more profound effects on elevation of RVSP in Sod3−/− compared to wild-type littermate. Increase in RVSP was concomitant with hypertrophy of pulmonary arteries located in silicotic nodules of both mouse strains, however, vascular remodeling in unaffected areas of lung was detected only in Sod3−/− mice.ConclusionsOur data suggest that Sod3 and extracellular oxidative stress may play an important role in the development of pneumoconiosis and pulmonary vascular remodeling following exposure to environmental and occupational silica.

Long-term polarization of alveolar macrophages to a profibrotic phenotype after inhalation exposure to multi-wall carbon nanotubes.

BackgroundNanomaterials are widely used in various fields. Although the toxicity of carbon nanotubes (CNTs) in pulmonary tissues has been demonstrated, the toxicological effect of CNTs on the immune system in the lung remains unclear.Methods and findingIn this study, exposure to Taquann-treated multi-walled CNTs (T-CNTs) was performed using aerosols generated in an inhalation chamber. At 12 months after T-CNT exposure, alveolar inflammation with macrophage accumulation and hypertrophy of the alveolar walls were observed. In addition, fibrotic lesions were enhanced by T-CNT exposure. The macrophages in the bronchoalveolar lavage fluid of T-CNT-exposed mice were not largely shifted to any particular population, and were a mixed phenotype with M1 and M2 polarization. Moreover, the alveolar macrophages of T-CNT-exposed mice produced matrix metalloprotinase-12.ConclusionsThese results suggest that T-CNT exposure promoted chronic inflammation and fibrotic lesion formation in profibrotic macrophages for prolonged periods.

Contribution of reactive oxygen species to the pathogenesis of pulmonary arterial hypertension.

Pulmonary arterial hypertension is associated with a decreased antioxidant capacity. However, neither the contribution of reactive oxygen species to pulmonary vasoconstrictor sensitivity, nor the therapeutic efficacy of antioxidant strategies in this setting are known. We hypothesized that reactive oxygen species play a central role in mediating both vasoconstrictor and arterial remodeling components of severe pulmonary arterial hypertension. We examined the effect of the chemical antioxidant, TEMPOL, on right ventricular systolic pressure, vascular remodeling, and enhanced vasoconstrictor reactivity in both chronic hypoxia and hypoxia/SU5416 rat models of pulmonary hypertension. SU5416 is a vascular endothelial growth factor receptor antagonist and the combination of chronic hypoxia/SU5416 produces a model of severe pulmonary arterial hypertension with vascular plexiform lesions/fibrosis that is not present with chronic hypoxia alone. The major findings from this study are: 1) compared to hypoxia alone, hypoxia/SU5416 exposure caused more severe pulmonary hypertension, right ventricular hypertrophy, adventitial lesion formation, and greater vasoconstrictor sensitivity through a superoxide and Rho kinase-dependent Ca2+ sensitization mechanism. 2) Chronic hypoxia increased medial muscularization and superoxide levels, however there was no effect of SU5416 to augment these responses. 3) Treatment with TEMPOL decreased right ventricular systolic pressure in both hypoxia and hypoxia/SU5416 groups. 4) This effect of TEMPOL was associated with normalization of vasoconstrictor responses, but not arterial remodeling. Rather, medial hypertrophy and adventitial fibrotic lesion formation were more pronounced following chronic TEMPOL treatment in hypoxia/SU5416 rats. Our findings support a major role for reactive oxygen species in mediating enhanced vasoconstrictor reactivity and pulmonary hypertension in both chronic hypoxia and hypoxia/SU5416 rat models, despite a paradoxical effect of antioxidant therapy to exacerbate arterial remodeling in animals with severe pulmonary arterial hypertension in the hypoxia/SU5416 model.

Blebbistatin-Loaded Poly(d,l-lactide-co-glycolide) Particles For Treating Arthrofibrosis.

Joint immobility is a debilitating complication of articular trauma that is characterized by thickening and stiffening of the joint capsule and the formation of fibrotic lesions inside joints. Capsule release surgery can temporarily restore mobility, but contraction often recurs due to the contractile activities of fibroblasts, which exert tension on the capsule ECM via nonmuscle myosin II. Based on these findings we hypothesized that blebbistatin, a drug that reversibly inhibits the activity of this protein, would relax ECM tension imposed by fibroblasts and reduce fibrosis. In this study, we characterized the effectiveness of blebbistatin as an anticontractile treatment. Given that sustained suppression of contractile activity may be required to achieve capsule release and reduce fibrosis, we compared the effects on fibroblast-mediated collagen ECM displacement of blebbistatin-loaded poly(lactide-co-gylcolide) (PLGA) particles versus bolus blebbistatin dosing. Time-lapse imaging of fluorescent microspheres embedded in collagen gels confirmed that PLGA/blebbistatin inhibited force generation and reduced both gel displacement and rate of displacement. In addition, collagen production at 10 days was significantly reduced. Taken together, these data indicate that blebbistatin-loaded PLGA particles can be used to inhibit fibroblast force-generation and reduce collagen production and lay the foundation for optimization of drug delivery technology for treating arthrofibrosis.

Inhibition of murine fibrocyte differentiation by cross-linked IgG is dependent on FcγRI.

Monocyte-derived, fibroblast-like cells, called fibrocytes, participate in wound-healing and the formation of fibrotic lesions. Aggregated or cross-linked IgG are key effectors in infections, autoimmune diseases, anaphylaxis, and immunotherapy. Cells, including monocytes and fibrocytes, bind IgG using FcγRs, and aggregated or cross-linked IgG inhibits fibrocyte differentiation. Mice have four different FcγRs, and which of these, if any, mediate the cross-linked IgG effect on fibrocyte differentiation is unknown. We find that in mice, deletion of FcγRI or the common signaling protein FcRγ significantly reduces the ability of cross-linked IgG or IgG2a to inhibit fibrocyte differentiation. Cells from FcγRIIb/III/IV KO mice are still sensitive to cross-linked IgG, whereas cells from FcγRI/IIb/III/IV KO mice are insensitive to cross-linked IgG. These observations suggest that IgG-mediated inhibition of fibrocyte differentiation is mediated by FcγRs, with FcγRI mediating most of the signaling.

Dual Targeting of MEK and PI3K Pathways Attenuates Established and Progressive Pulmonary Fibrosis

Pulmonary fibrosis is often triggered by an epithelial injury resulting in the formation of fibrotic lesions in the lung, which progress to impair gas exchange and ultimately cause death. Recent clinical trials using drugs that target either inflammation or a specific molecule have failed, suggesting that multiple pathways and cellular processes need to be attenuated for effective reversal of established and progressive fibrosis. Although activation of MAPK and PI3K pathways have been detected in human fibrotic lung samples, the therapeutic benefits of in vivo modulation of the MAPK and PI3K pathways in combination are unknown. Overexpression of TGFα in the lung epithelium of transgenic mice results in the formation of fibrotic lesions similar to those found in human pulmonary fibrosis, and previous work from our group shows that inhibitors of either the MAPK or PI3K pathway can alter the progression of fibrosis. In this study, we sought to determine whether simultaneous inhibition of the MAPK and PI3K signaling pathways is a more effective therapeutic strategy for established and progressive pulmonary fibrosis. Our results showed that inhibiting both pathways had additive effects compared to inhibiting either pathway alone in reducing fibrotic burden, including reducing lung weight, pleural thickness, and total collagen in the lungs of TGFα mice. This study demonstrates that inhibiting MEK and PI3K in combination abolishes proliferative changes associated with fibrosis and myfibroblast accumulation and thus may serve as a therapeutic option in the treatment of human fibrotic lung disease where these pathways play a role.

FcγRI mediates serum amyloid P inhibition of fibrocyte differentiation

Fibrotic diseases, such as cardiac and pulmonary fibrosis, have a poor prognosis with no FDA approved therapies. Monocyte-derived, fibroblast-like cells, called fibrocytes, participate in the formation of fibrotic lesions. The conserved pentraxin protein SAP inhibits fibrocyte differentiation in cell culture, and injections of SAP significantly reduce fibrosis in several animal models. SAP binds to the receptors for the Fc portion of IgG (FcγR) and has been crystallized bound to FcγRIIa (CD32a). The in vivo activity of SAP appears to be dependent on the FcRγ. We find that mutagenesis of the residues critical for SAP binding to FcγRIIa only moderately decreases the ability of SAP to inhibit fibrocyte differentiation. In murine cells, deletion of FcRγ or FcγRI (CD64) significantly reduced sensitivity to SAP. Deletion of the combination of FcγRIIb, FcγRIIIa, and FcγRIV did not significantly affect sensitivity to SAP, whereas deletion of just the inhibitory receptor FcγRIIb (CD32b) increased sensitivity to SAP. In human cells, siRNA-mediated reduction of FcRγ or FcγRI levels significantly decreased sensitivity to SAP, whereas reduction of FcγRIIb levels increased sensitivity to SAP. These observations suggest that SAP, at least in part, uses FcγRI and FcRγ to inhibit fibrocyte differentiation.

Methylglyoxal-modified collagen promotes myofibroblast differentiation

Fibrosis is a frequent complication of diabetes mellitus in many organs and tissues but the mechanism of how diabetes-induced glycation of extracellular matrix proteins impacts the formation of fibrotic lesions is not defined. As fibrosis is mediated by myofibroblasts, we investigated the effect of collagen glycation on the conversion of human cardiac fibroblasts to myofibroblasts. Collagen glycation was modeled by the glucose metabolite, methylglyoxal (MGO). Cells cultured on MGO-treated collagen exhibited increased activity of the α-smooth muscle actin promoter and enhanced expression of α-smooth muscle actin, ED-A fibronectin and cadherin, which are markers for myofibroblasts. In cells remodeling floating or stress-relaxed collagen gels, MGO treatment promoted more contraction (p<0.025) than vehicle controls, which was MGO dose-dependent. Transwell assays showed that cell migration was increased by MGO-treated collagen (p<0.025). In shear-force detachment assays, cells on MGO-treated collagen were less adherent than untreated collagen, and the formation of high affinity, β1 integrin-dependent adhesions was inhibited. MGO-collagen-induced expression of SMA was dependent on TGF-β but not on Rho kinase. We conclude that collagen glycation augments the formation and migration of myofibroblasts, critical processes in the development of fibrosis in diabetes.

Downregulation of FAK-related non-kinase mediates the migratory phenotype of human fibrotic lung fibroblasts

Fibroblast migration plays an important role in the normal wound healing process; however, dysregulated cell migration may contribute to the progressive formation of fibrotic lesions in the diseased condition. To examine the role of focal-adhesion-kinase (FAK)-related non-kinase (FRNK) in regulation of fibrotic lung fibroblast migration, we examined cell migration, FRNK expression, and activation of focal adhesion kinase (FAK) and Rho GTPase (Rho and Rac) in primary lung fibroblasts derived from both idiopathic pulmonary fibrosis (IPF) patients and normal human controls. Fibrotic (IPF) lung fibroblasts have increased cell migration when compared to control human lung fibroblasts. FRNK expression is significantly reduced in IPF lung fibroblasts, while activation of FAK, Rho and Rac is increased in IPF lung fibroblasts. Endogenous FRNK expression is inversely correlated with FAK activation and cell migration rate in IPF lung fibroblasts. Forced exogenous FRNK expression abrogates the increased cell migration, and blocked the activation of FAK and Rho GTPase (Rho and Rac), in IPF lung fibroblasts. These data for the first time provide evidence that downregulation of endogenous FRNK plays a role in promoting cell migration through FAK and Rho GTPase in fibrotic IPF lung fibroblasts.

Apoptosis in Pulmonary Fibrosis: Too Much or Not Enough?

Apoptosis plays an important role in both normal lung homeostasis and lung remodeling associated with fibrotic lung disease. Whether apoptosis promotes or inhibits the pathogenesis of pulmonary fibrosis depends upon the cell type involved and the microenvironment of the affected lung. Undue cell loss in the alveolar epithelium may be important early in idiopathic pulmonary fibrosis (IPF) progression, while reduced fibroblast and myofibroblast apoptosis has been associated with the formation of fibrotic lesions. As such, novel therapies based on the stimulation or inhibition of apoptosis may prove beneficial to the treatment of patients with IPF.