Fibroblast Extracellular Matrix Production Research Articles

SEMA3B inhibits TGFβ-induced extracellular matrix protein production and its reduced levels are associated with a decline in lung function in IPF.

Idiopathic pulmonary fibrosis (IPF) is marked by the activation of fibroblasts, leading to excessive production and deposition of extracellular matrix (ECM) within the lung parenchyma. Despite the pivotal role of ECM overexpression in IPF, potential negative regulators of ECM production in fibroblasts have yet to be identified. Semaphorin class 3B (SEMA3B), a secreted protein highly expressed in lung tissues, has established roles in axonal guidance and tumor suppression. However, the role of SEMA3B in ECM production by fibroblasts in the pathogenesis of IPF remains unexplored. Here, we show the downregulation of SEMA3B and its cognate binding receptor, neuropilin 1 (NRP1) in IPF lungs compared with healthy controls. Notably, the reduced expression of SEMA3B and NRP1 is associated with a decline in lung function in IPF. The downregulation of SEMA3B and NRP1 transcripts was validated in the lung tissues of patients with IPF, and two alternative mouse models of pulmonary fibrosis. In addition, we show that TGFβ functions as a negative regulator of SEMA3B and NRP1 expression in lung fibroblasts. Furthermore, we demonstrate the anti-fibrotic effects of SEMA3B against TGFβ-induced ECM production in IPF lung fibroblasts. Overall, our findings uncovered a novel role of SEMA3B in the pathogenesis of pulmonary fibrosis and provided novel insights into modulating the SEMA3B-NRP1 axis to attenuate pulmonary fibrosis.

FOXO4-D-Retro-Inverso targets extracellular matrix production in fibroblasts and ameliorates bleomycin-induced pulmonary fibrosis in mice.

Pulmonary fibrosis (PF) occurs in various end stages of lung disease, and it is characterized by persistent scarring of the lung parenchyma with excessive deposition of extracellular matrix (ECM), leading to degressive quality of life and earlier mortality. FOXO4-D-Retro-Inverso (FOXO4-DRI), a synthesis peptide as a specific FOXO4 blocker, selectively induced dissociation of the FOXO4-p53 complex and nuclear exclusion of p53. Simultaneously, the p53 signaling pathway has been reported to activate in fibroblasts isolated from IPF fibrotic lung tissues and the p53 mutants cooperate with other factors that have the ability to disturb the synthesis of ECM. Yet, whether FOXO4-DRI influences the nuclear exclusion of p53 and then obstructs PF progress is still unknown. In this research, we explored the effect of FOXO4-DRI on bleomycin (BLM)-induced PF mouse model and activated fibroblasts model. The animal group of FOXO4-DRI therapeutic administration shows a milder pathologic change and less collagen deposition compared with the BLM-induced group. We also found the FOXO4-DRI resets the distribution of intranuclear p53 and concurrently decreased the total ECM proteins content. After further validation, FOXO4-DRI may well be a promising therapeutic approach to treating pulmonary fibrosis.

Photothermal lipolysis accelerates ECM production via macrophage-derived ALOX15-mediated p38 MAPK activation in fibroblasts.

Skin and subcutaneous tissue tightening is usually treated by noninvasive photothermal treatment for medical esthetics purpose, while the underlying mechanism remains to be elucidated. Here, we hypothesized that adipocyte injury, as a stimulator, may regulate extracellular matrix (ECM) production by increasing ALOX15 in macrophages, which could lead to fibroblast activation. In this study, we show that lipolysis was induced by laser heating (45°C for 15 min) in patients and rats, and adipocyte thermal injury stimulates the ECM production in fibroblasts by ALOX15 that was increased in cocultured macrophages. These phenomena were evidenced by the ALOX15 knockdown. In addition, ALOX15 metabolite 12(S)-HETE activated p38 MAPK signaling pathway that mediated the production of ECM in fibroblast. In summary, the results of this study demonstrate that the mechanisms of adipose photothermal injury-induced skin and/or subcutaneous tissue tightening may have clinical relevance for noninvasive or minimally invasive photothermal therapeutics.

A novel molecular mechanism of vascular fibrosis in Takayasu arteritis: macrophage-derived GPNMB promoting adventitial fibroblast extracellular matrix production in the aorta

Takayasu arteritis (TAK) is a chronic large vessel disease characterized by aortic fibrotic thickening, which was mainly mediated by activation of aorta adventitial fibroblasts (AAFs). Our previous genetic study demonstrated that TAK-associated locus IL6 rs2069837 regulated glycoprotein non-metastatic melanoma protein B (GPNMB) expression. Thus, this study aimed to investigate the pathogenic role of GPNMB in TAK. Through pathological staining, we find that GPNMB was mainly expressed in vascular adventitia and positively correlated with adventitial extracellular matrix (ECM) expression in TAK vascular lesion. Specifically, GPNMB was increased in adventitial CD68+ macrophages, which were closely located with CD90+ adventitial fibroblasts. In in-vitro cell culture, THP-1-derived macrophages with GPNMB overexpression promoted ECM expression in AAFs. This effect was also confirmed in aortic tissue or AAFs culture with GPNMB overexpression or active GPNMB protein stimulation. Mechanistically, Co-IP assay and siRNA or inhibitor intervention demonstrated that integrin αVβ1 receptor mediated GPNMB effect on AAFs, which also activated downstream Akt and Erk pathway in AAFs. Furthermore, we showed that leflunomide treatment inhibited GPNMB-mediated fibrosis in AAFs, as well as GPNMB expression in macrophages, which were also partially validated in leflunomide-treated patients. Taken together, these data indicated that macrophage-derived GPNMB promotes AAFs ECM expression via the integrin αVβ1 receptor and Akt/Erk signaling pathway and leflunomide might play an anti-fibrotic role in TAK by interfering with the macrophage-derived GPNMB/AAFs axis. This study provides evidence that targeting GPNMB is a potential therapeutic strategy for treating vascular fibrosis in TAK.

36. Spironolactone Mitigates Fibrosis and Improves Healing of Burn Wounds

Purpose: Adhesion, contracture, and the formation of disfiguring, hypertrophic scars remain some of the most recalcitrant problems in care of the burned patient. The central pathology driving fibrosis is an imbalance of extracellular matrix (ECM). The mineralocorticoid receptor (MR) is a nuclear receptor with shared ligand-activity from both its primary activator, aldosterone, and glucocorticoids and has cell specific effects on proliferation, migration, and ECM production in fibroblasts and keratinocytes. Here we demonstrate that MR-inhibition with FDA approved spironolactone enhances epithelialization healing and mitigates hypertrophic collagen deposition after burns in mice. Methods: Female athymic mice sustained bilateral 1 cm full-thickness thermal injury and were stratified into either a) vehicle, b) spironolactone, c) aldosterone, or d) aldosterone + spironolactone. Aldosterone applied via subcutaneous pump (Alzet) spironolactone delivered intraperitoneally. Mice followed photographically for 4-to-6-weeks. At sacrifice wound biopsies were collected for H&E, Trichrome, and protein. An additional subset of samples were assessed via Pentachrome staining to assess relative ratio of collagen, fibrin, and elastic fibers. Pentachrome samples were analyzed using ImageJ (RGB Hue threshold) to isolate elastin, GAG and collagen for quantification. Results: Histologic evaluation of healing wounds from burned mice demonstrated persistence of inflammation, wound edema, and immature ECM. In mice treated with spironolactone this effect if alleviated by 4-weeks post-injury concurrent with gross findings of rapid wound epithelialization. Spironolactone treatment additionally enhanced gross and histologic evidence of scar resolution and resulted in a decreased in collagen staining vs. controls. Conclusion: We found a significant early improvement in wound epithelialization with spironolactone therapy. This suggests a potentially distinct effect from the proposed ECM-modifying strategy hypothesized. More analysis is needed but this data supports that MR-inhibition may be a valuable new therapeutic in treatment of burn scars.

Abstract 3642: The aged lung promotes reactivation from metastatic melanoma dormancy

Abstract Our previous data have indicated that while tumors grow more slowly in aged mouse skin, they form more lung metastases. We queried whether the lung microenvironment undergoes age-related changes that provide a permissive niche for metastatic outgrowth. Our data showed that secreted factors by lung fibroblasts changed during aging that promoted proliferation of melanoma cells via expression of the tyrosine kinase receptor MER. Further investigation of this MER-high phenotype revealed that these melanoma cells induce dramatic changes to the lung microenvironment via secretion of its primary ligand PROS1, which creates a more permissive niche for metastasis. It first acts in a paracrine manner to induce proliferation of previously dormant melanoma cells in the lung. MER induced secretion of PROS1 by melanoma cells also regulates the production of extracellular matrix (ECM) from lung fibroblasts. Specifically, healthy human lung fibroblasts produce thick, unified cellular derived matrices (CDMs) in vitro that are growth-restrictive to melanoma cells. Treatment of lung fibroblasts with conditioned media from MER-High melanoma cells or with recombinant-PROS1 alters CDM density and orientation, which resulted in a CDM that dramatically increased melanoma proliferation. Finally, we found that MER induced metastatic outgrowth of melanoma cells within the lungs of mice decreased CD4 and CD8 T-cells whilst increasing infiltration of and immunosuppressive T-regulatory cells (Tregs) and Myeloid Derived Suppressor Cells (MDSCs). Overall, we find that age-induced activation of melanoma cells towards a MER-high state within the lung can induce a cancer phenotype which dramatically alters fibroblast ECM production and immune cell infiltration to promote aggressive and efficient metastatic outgrowth and a growth permissive microenvironment for dormant melanoma cells. Citation Format: Mitchell Fane, Ashani Weeraratna. The aged lung promotes reactivation from metastatic melanoma dormancy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3642.

P31. CONTROL OF THE MINERALOCORTICOID RECEPTOR ENHANCES WOUND HEALING AND MITIGATE FIBROSIS AFTER THERMAL INJURY

PURPOSE: Adhesion, contracture, and the formation of disfiguring, hypertrophic scars remain some of the most recalcitrant problems in care of the burned patient. The central pathology driving fibrosis is an imbalance of extracellular matrix (ECM). The mineralocorticoid receptor (MR) is a nuclear receptor with shared ligand-activity from both its primary activator, aldosterone, and glucocorticoids and has cell specific effects on proliferation, migration, and ECM production in fibroblasts and keratinocytes. Here we demonstrate that MR-inhibition with FDA approved spironolactone enhances epithelialization healing and mitigates hypertrophic collagen deposition after burns in mice. METHODS: Female athymic mice sustained bilateral 1 cm full-thickness thermal injury and were stratified into either a) vehicle, b) spironolactone, c) aldosterone, or d) aldosterone + spironolactone. Aldosterone applied via subcutaneous pump (Alzet) spironolactone delivered intraperitoneally. Mice followed photographically for 4-to-6-weeks. At sacrifice wound biopsies were collected for H&E, Trichrome, and protein. RESULTS: Histologic evaluation of healing wounds from burned mice demonstrated persistence of inflammation, wound edema, and immature ECM. In mice treated with spironolactone this effect if alleviated by 4-weeks post-injury concurrent with gross findings of rapid wound epithelialization. Spironolactone treatment additionally enhanced gross and histologic evidence of scar resolution and resulted in a decreased in collagen staining vs. controls. CONCLUSION: We found a significant early improvement in wound epithelialization with spironolactone therapy. This suggests a potentially distinct effect from the proposed ECM-modifying strategy hypothesized. More analysis is needed but this data supports that MR-inhibition may be a valuable new therapeutic in treatment of burn scars.

Pentoxifylline Regulates Plasminogen Activator Inhibitor-1 Expression and Protein Kinase A Phosphorylation in Radiation-Induced Lung Fibrosis.

Purpose. Radiation-induced lung fibrosis (RILF) is a serious late complication of radiotherapy. In vitro studies have demonstrated that pentoxifylline (PTX) has suppressing effects in extracellular matrix production in fibroblasts, while the antifibrotic action of PTX alone using clinical dose is yet unexplored. Materials and Methods. We used micro-computed tomography (micro-CT) and histopathological analysis to evaluate the antifibrotic effects of PTX in a rat model of RILF. Results. Micro-CT findings showed that lung density, volume loss, and mediastinal shift are significantly increased at 16 weeks after irradiation. Simultaneously, histological analysis demonstrated thickening of alveolar walls, destruction of alveolar structures, and excessive collagen deposition in the irradiated lung. PTX treatment effectively attenuated the fibrotic changes based on both micro-CT and histopathological analyses. Western analysis also revealed increased levels of plasminogen activator inhibitor- (PAI-) 1 and fibronectin (FN) and PTX treatment reduced expression of PAI-1 and FN by restoring protein kinase A (PKA) phosphorylation but not TGF-β/Smad in both irradiated lung tissues and epithelial cells. Conclusions. Our results demonstrate the antifibrotic effect of PTX on radiation-induced lung fibrosis and its effect on modulation of PKA and PAI-1 expression as possible antifibrotic mechanisms.

The effects of negative pressure treatment on the extracellular matrix gene expression and protein production of fibroblasts

Although negative pressure wound therapy (NPWT) has been suggested for the management of acute and chronic wounds, the underlying mechanism of NPWT on the cellular level is not fully understood. Using a primary fibroblast culture model with controlled negative pressure, the cellular responses to the negative pressure was investigated. The present results showed that cell proliferation of fibroblasts was not affected under negative pressure. The mRNA expressions of collagen type I, collagen type III, and fibronectin were down-regulated when cells treated with negative pressure for once only. However, those mRNA expressions were up-regulated when cells subjected to periodical negative pressure consecutively for 5 days. The protein production of TGF-β1 was enhanced, while the TIMP-1, decorin, and IL-6 were not influenced. The pro-MMP-9 was not stimulated when fibroblasts subjected to negative pressure. The regulations of extracellular matrix production in fibroblasts provides an insight into the cellular mechanisms of NPWT.

Keloid‐derived keratinocytes exhibit an abnormal gene expression profile consistent with a distinct causal role in keloid pathology

Keloids are disfiguring scars that extend beyond the original wound borders and resist treatment. Keloids exhibit excessive extracellular matrix deposition, although the underlying mechanisms remain unclear. To better understand the molecular basis of keloid scarring, here we define the genomic profiles of keloid fibroblasts and keratinocytes. In both cell types, keloid-derived cells exhibit differential expression of genes encompassing a diverse set of functional categories. Strikingly, keloid keratinocytes exhibited decreased expression of a set of transcription factor, cell adhesion, and intermediate filament genes essential for normal epidermal morphology. Conversely, they exhibit elevated expression of genes associated with wound healing, cellular motility, and vascular development. A substantial number of genes involved in epithelial-mesenchymal transition were also up-regulated in keloid keratinocytes, implicating this process in keloid pathology. Furthermore, keloid keratinocytes displayed significantly higher migration rates than normal keratinocytes in vitro and reduced expression of desmosomal proteins in vivo. Previous studies suggested that keratinocytes contribute to keloid scarring by regulating extracellular matrix production in fibroblasts. Our current results show fundamental abnormalities in keloid keratinocytes, suggesting they have a profoundly more direct role in keloid scarring than previously appreciated. Therefore, development of novel therapies should target both fibroblast and keratinocyte populations for increased efficacy.

The role of endostatin in fibroproliferative disorders.<br/>—as a candidate for anti-fibrosis therapy—

There are no effective treatments for fibrosis, an out-of-control wound-healing process in which excessive deposition of extracellular matrix (ECM) such as collagen, resulting in significant morbidity and mortality. Endostatin is a natural proteolytic fragment of collagen XVIII, which is known to possess potent antiangiogenic activity. Many clinical trials of endostatin have been conducted for anti-cancer therapy. In addition to antiangiogenic effects, recent studies have revealed that endostatin may suppress aberrant tissue remodeling and scarring. Neutralization of endogenous endostatin in rat myocardial infarction (MI) model worsened the outcomes of MI, indicating that endostatin may have protective role against left ventricular remodeling and heart failure after MI. Recently, we also reported inhibitory effects of peptides derived from endostatin on fibrosis. A peptide derived from the C-terminus of endostatin suppressed ECM production in fibroblasts in the presence of transforming growth factor-β (TGF-β), prevented TGF-β-induced dermal fibrosis ex vivo in human skin, and ameliorated skin and pulmonary fibrosis induced by bleomycin in vivo. The antifibrotic capacity was accompanied by reduced cell apoptosis and lower levels of lysyl oxidase and early growth response gene-1. Endostation may have the therapeutic potential for inhibiting fibrosis.

Role of TGF-β in chronic kidney disease: an integration of tubular, glomerular and vascular effects

Transforming growth factor beta (TGF-β) has been recognized as an important mediator in the genesis of chronic kidney diseases (CKD), which are characterized by the accumulation of extracellular matrix (ECM) components in the glomeruli (glomerular fibrosis, glomerulosclerosis) and the tubular interstitium (tubulointerstitial fibrosis). Glomerulosclerosis is a major cause of glomerular filtration rate reduction in CKD and all three major glomerular cell types (podocytes or visceral epithelial cells, mesangial cells and endothelial cells) participate in the fibrotic process. TGF-β induces (1) podocytopenia caused by podocyte apoptosis and detachment from the glomerular basement membrane; (2) mesangial expansion caused by mesangial cell hypertrophy, proliferation (and eventually apoptosis) and ECM synthesis; (3) endothelial to mesenchymal transition giving rise to glomerular myofibroblasts, a major source of ECM. TGF-β has been shown to mediate several key tubular pathological events during CKD progression, namely fibroblast proliferation, epithelial to mesenchymal transition, tubular and fibroblast ECM production and epithelial cell death leading to tubular cell deletion and interstitial fibrosis. In this review, we re-examine the mechanisms involved in glomerulosclerosis and tubulointerstitial fibrosis and the way that TGF-β participates in renal fibrosis, renal parenchyma degeneration and loss of function associated with CKD.

Influence of hydrogel mechanical properties and mesh size on vocal fold fibroblast extracellular matrix production and phenotype

Current clinical management of vocal fold (VF) scarring produces inconsistent and often suboptimal results. Researchers are investigating a number of alternative treatments for VF lamina propria (LP) scarring, including designer implant materials for functional LP regeneration. In the present study, we investigate the effects of the initial scaffold elastic modulus and mesh size on encapsulated VF fibroblast (VFF) extracellular matrix (ECM) production toward rational scaffold design. Poly(ethylene glycol) diacrylate (PEGDA) hydrogels were selected for this study since their material properties, including mechanical properties, mesh size, degradation rate and bioactivity, can be tightly controlled and systematically modified. Porcine VFF were encapsulated in four PEGDA hydrogels with degradation half lives of ∼25 days, but with initial elastic compressive moduli and mesh sizes ranging from ∼30 to 100 kPa and from ∼9 to 27 nm, respectively. After 30 days of static culture, VFF ECM production and phenotype in each formulation was assessed biochemically and histologically. Sulfated glycosaminoglycan synthesis increased in similar degree with both increasing initial modulus and decreasing initial mesh size. In contrast, elastin production decreased with increasing initial modulus but increased with decreasing initial mesh size. Both collagen deposition and the induction of a myofibroblastic phenotype depended strongly on initial mesh size but appeared largely unaffected by variations in initial modulus. The present results indicate that scaffold mesh size warrants further investigation as a critical regulator of VFF ECM synthesis. Furthermore, this study validates a systematic and controlled approach for analyzing VFF response to scaffold properties, which should aid in rational scaffold selection/design.

5-Fluorouracil Selectively Inhibits Collagen Synthesis

Fibroproliferative disorders, such as Dupuytren's contracture of the hand, are characterized by excessive production of collagen. 5-Fluorouracil has been used to treat fibroproliferative disorders of the eye and skin and is thought to inhibit thymidylate synthetase blocking DNA replication. 5-Fluorouracil has been shown to down-regulate fibroblast proliferation and differentiation in vitro. This study investigated the dose-dependent effect of 5-fluorouracil on fibroblast extracellular matrix production. Fibroblasts were derived from tendon and primary Dupuytren's disease of the hand, a fibroproliferative disorder of the palmar aponeurosis (n = 4 patients). Total collagen synthesis was determined by means of the incorporation of radiolabeled proline. Fibroblast secretion of the profibrotic factor transforming growth factor-beta1 (TGF-beta1) was measured by a sandwich enzyme-linked immunosorbent assay. Gene expression of collagen types I and III and TGF-beta1 were quantified by means of reverse-transcriptase polymerase chain reaction assays. The authors found that 5-fluorouracil caused a dose-dependent, selective, and specific decrease in collagen production by Dupuytren's fibroblasts compared with noncollagenous protein synthesis. By contrast, procollagen types I and III mRNA were unaffected by 5-fluorouracil treatment. These changes did not appear to be mediated by alterations in the endogenous secretion of TGF-beta1 or its autocrine effect on collagen metabolism. The clinical implication is that 5-fluorouracil could possibly reduce extracellular matrix production and therefore reduce recurrence of Dupuytren's disease of the hand.

Molecular cross-talk between the TRAIL and TGF-β pathways in human lung fibroblasts

Tumor-necrosis-factor-related apoptosis-inducing ligand (TRAIL) has been closely associated with regulation of the immune response and pathogenesis of autoimmune diseases. The expression of TRAIL was found in CD8 T cells that had undergone oligoclonal expansion in the lungs of patients with systemic sclerosis and were able to stimulate collagen production in lung fibroblasts. Soluble, multimerized TRAIL and normal human lung fibroblasts were used as a model of selective TRAIL influence on fibroblasts. TRAIL was found to increase both α2(I) collagen mRNA expression and total soluble collagen secretion, with peak response at 1 ng/ml TRAIL. DNA microarray analysis suggested that fibroblast response to TRAIL might be mediated by c-Jun N-terminal kinase (JNK). The increase in JNK1 expression and phosphorylation as well as phosphorylation of its specific substrate were confirmed by Western blotting. The treatment of fibroblasts with TRAIL also enhanced the expression of a number of genes involved in tissue remodeling, including those related to the transforming growth factor (TGF) beta pathway. The increase in TGF-β1 mRNA level was confirmed by Northern blotting and by measurements of active TGF-β1 in culture supernatants. In addition, antibody-mediated blocking of TGF-β was shown to abrogate TRAIL-induced collagen synthesis. These data suggest that TRAIL can enhance extracellular matrix production in fibroblasts by triggering expression of TGF-β, which acts in an autocrine manner. If this process continues uncontrolled, it may contribute to the development of fibrosis, particularly in the lungs of patients with systemic sclerosis.

Fli-1 Inhibits Collagen Type I Production in Dermal Fibroblasts via an Sp1-dependent Pathway

Fibrosis is characterized by the excessive deposition of extracellular matrix (ECM), especially collagen. Because Ets factors are implicated in physiological and pathological ECM remodeling, the aim of this study was to investigate the role of Ets factors in collagen production. We demonstrate that the expression of collagenous proteins and collagen alpha2(I) (COL1A2) mRNA was inhibited following stable transfection of Fli-1 in dermal fibroblasts. Subsequent analysis of the COL1A2 promoter identified a critical Ets binding site that mediates Fli-1 inhibition. In contrast, Ets-1 stimulates COL1A2 promoter activity. In vitro binding assays demonstrate that both Fli-1 and Ets-1 form DNA-protein complexes with sequences present in COL1A2 promoter. Furthermore, Fli-1 binding to the COL1A2 is enhanced via Sp1-dependent interaction. Studies using Fli-1 dominant interference and DNA binding mutants indicate that Fli-1 inhibition is mediated by both direct (DNA binding) and indirect (via protein-protein interaction) mechanisms and that Sp1 is an important mediator of the Fli-1 function. Furthermore, experiments using the Gal4 system in the context of different cell types as well as experiments with the COL1A2 promoter in different cell lines demonstrate that the direction and magnitude of the effect of Fli-1 is promoter- and cell context-specific. We propose that Fli-1 inhibits COL1A2 promoter activity by competition with Ets-1. In addition, we postulate that another factor (co-repressor) may be required for maximal inhibition after recruitment to the Fli-1-Sp1 complex. We conclude that the ratio of Fli-1 to Ets-1 and the presence of co-regulatory proteins ultimately control ECM production in fibroblasts.

Silica and Its Antagonistic Effects on Transforming Growth Factor-β in Lung Fibroblast Extracellular Matrix Production

BackgroundSilicosis, a pneumoconiosis marked by interstitial pulmonary fibrosis, is caused by inhalation of free crystalline silica particles. When silica particles are injected into the lower lung, they are translocated across...

Interleukin 4 in Systemic Sclerosis: Not Just an Increase

Interleukin 4 in Systemic Sclerosis: Not Just an Increase

Regulation of Cardiac Fibroblast Extracellular Matrix Production by Bradykinin and Nitric Oxide

The beneficial effects of angiotensin-converting enzyme inhibitors on ameliorating cardiac fibrosis have been partially attributed to their ability to prevent the degradation of kinins. The potential role of bradykinin and the related signaling molecule nitric oxide (NO) in modulating extracellular matrix (ECM) production was examined in primary cultures of adult rat cardiac fibroblasts. Treatment of fibroblasts with 5 nmbradykinin for 24 h led to a reduction in steady-state mRNA levels for fibronectin (34±7%) and collagens type I (19±8%) and type III (48±4%), as determined by Northern blot analysis. The NO synthase inhibitorl-NAME attenuated the reduction observed in fibronectin and collagen mRNA levels in response to bradykinin. The NO donor DETA NONOate (100 μm) mimicked the effects of bradykinin on ECM mRNA levels. Protein levels of soluble fibronectin, assessed in conditioned medium by ELISA, were decreased by 14±4% and 21±4% after 48 h treatment with 1 μmbradykinin and 100 μmDETA NONOate, respectively. Bradykinin stimulated intracellular cGMP accumulation 73.7±10.3% after 10 min of treatment. Cell proliferation rates at 48 h were unaffected by bradykinin, but were reduced by 26±12% by 100 μmDETA NONOate. These data indicate that bradykinin downregulates ECM protein production in cardiac fibroblasts and suggest that NO and the related signaling molecule cGMP may play an important role in mediating this reponse.

Keratinocytes contract human dermal extracellular matrix and reduce soluble fibronectin production by fibroblasts in a skin composite model

Composites of human de-epidermised acellular dermis and normal adult human keratinocytes and fibroblasts were examined for the ability of cells to contract these composites. Image analysis of the outline of the composites showed that, in this model, keratinocytes alone or in the presence of fibroblasts caused highly significant contraction (of the order of 25% by day. 12). There was no significant contraction of the dermis with fibroblasts alone or in the absence of cells. The presence or absence of basement membrane antigens did not influence the effect of keratinocytes on dermal contraction. Analysis of the conditioned media from these composites showed that the greatest fibronectin production was seen with fibroblasts alone in the presence of basement membrane. Keratinocytes alone produced little fibronectin irrespective of the presence of the basement membrane. If keratinocytes were present with fibroblasts, however, then fibronectin production was significantly reduced both in the presence and absence of the basement membrane, indicating that keratinocytes modify dermal fibroblast extracellular matrix production. This study shows that while keratinocytes and fibroblasts are clearly influencing each other's activity in this human skin composite model, under the circumstances we describe it is the keratinocyte and not the fibroblast which causes contraction of the human de-epidermised acellular dermis.