Showing papers on "Fibrosis published in 1998"

Idiopathic pulmonary fibrosis: clinical relevance of pathologic classification.

Abstract: Background Pathologic Classification of Idiopathic Pulmonary Fibrosis UIP DIP/Respiratory Bronchiolitis Interstitial Lung Disease (RBILD) AIP NSIP Clinical Features of the Idiopathic Interstitial Pneumonias UIP DIP/RBILD AIP N SIP Grading of “Cellularity” and Fibrosis Relationship of UIP and DIP Relationship of AIP and UIP Significance of NSIP—A Specific Disease or a Histologic Manifestation of Many Diseases? Summary and Conclusions

Mechanisms of spontaneous resolution of rat liver fibrosis. Hepatic stellate cell apoptosis and reduced hepatic expression of metalloproteinase inhibitors.

Abstract: Liver fibrosis results from the excessive secretion of matrix proteins by hepatic stellate cells (HSC), which proliferate during fibrotic liver injury. We have studied a model of spontaneous recovery from liver fibrosis to determine the biological mechanisms mediating resolution. Livers were harvested from rats at 0, 3, 7, and 28 d of spontaneous recovery from liver fibrosis induced by 4 wk of twice weekly intraperitoneal injections with CCl4. Hydroxyproline analysis and histology of liver sections indicated that the advanced septal fibrosis observed at time 0 (peak fibrosis) was remodeled over 28 d of recovery to levels close to control (untreated liver). alpha-Smooth muscle actin staining of liver sections demonstrated a 12-fold reduction in the number of activated HSC over the same time period with evidence of HSC apoptosis. Ribonuclease protection analysis of liver RNA extracted at each recovery time point demonstrated a rapid decrease in expression of the collagenase inhibitors TIMP-1 and TIMP-2, whereas collagenase mRNA expression remained at levels comparable to peak fibrosis. Collagenase activity in liver homogenates increased through recovery. We suggest that apoptosis of activated HSC may vitally contribute to resolution of fibrosis by acting as a mechanism for removing the cell population responsible for both producing fibrotic neomatrix and protecting this matrix from degradation via their production of TIMPs.

Genotypic variation in the transforming growth factor-beta1 gene: association with transforming growth factor-beta1 production, fibrotic lung disease, and graft fibrosis after lung transplantation

Abstract: Background Transforming growth factor (TGF)-β1 is a profibrogenetic cytokine that has been implicated in the development of fibrosis in transplanted tissues. In this study, we have analyzed the genetic regulation of TGF-β1 production in lung transplant recipients. Method. A polymerase chain reaction-single-stranded conformational polymorphism technique was used to detect polymorphisms in the TGF-β1 gene from genomic DNA. Polymorphisms were shown to correlate with in vitro TGF-β1 production by stimulated lymphocytes. A single-specific oligonucleotide probe hybridization method was devised to screen for these polymorphisms in lung transplant groups and controls. Results. We have identified five polymorphisms in the TGF-β1 gene: two in the promoter region at positions -800 and -509, one at position +72 in a nontranslated region, and two in the signal sequence at positions +869 and +915. The polymorphism at position +915 in the signal sequence, which changes codon 25 (arginine→proline), is associated with interindividual variation in levels of TGF-β1 production. Stimulated lymphocytes of homozygous genotype (arginine/arginine) from control individuals produced significantly more TGF-β1 in vitro (10037±745 pg/ml) compared with heterozygous (arginine/proline) individuals (6729±883 pg/ml; P<0.02). In patients requiring lung transplantation for a fibrotic lung condition, there was an increase in the frequency of the high-producer TGF-β1 allele (arginine). This allele was significantly associated with pretransplant fibrotic pathology (P<0.02) (n=45) when compared with controls (n=107) and with pretransplant nonfibrotic pathology (P<0.004) (n=50). This allele was also associated with allograft fibrosis in transbronchial biopsies when compared with controls (P<0.03) and with nonallograft fibrosis (P<0.01). Conclusion. The production of TGF-β1 is under genetic control, and this in turn influences the development of lung fibrosis. Hence, the TGF-β1 genotype has prognostic significance in transplant recipients.

Interactions of Transforming Growth Factor-β and Angiotensin II in Renal Fibrosis

Abstract: Overproduction of transforming growth factor-beta clearly underlies tissue fibrosis in numerous experimental and human diseases. Transforming growth factor-beta's powerful fibrogenic action results from simultaneous stimulation of matrix protein synthesis, inhibition of matrix degradation, and enhanced integrin expression that facilitates matrix assembly. In animals, overexpression of transforming growth factor-beta by intravenous injection, transient gene transfer, or transgene insertion has shown that the kidney is highly susceptible to rapid fibrosis. The same seems true in human disease, where excessive transforming growth factor-beta has been demonstrated in glomerulonephritis, diabetic nephropathy, and hypertensive glomerular injury. A possible explanation for the kidney's particular susceptibility to fibrosis may be the recent discovery of biologically complex interactions between the renin-angiotensin system and transforming growth factor-beta. Alterations in glomerular hemodynamics can activate both the renin-angiotensin system and transforming growth factor-beta. Components of the renin-angiotensin system act to further stimulate production of transforming growth factor-beta and plasminogen activator inhibitor leading to rapid matrix accumulation. In volume depletion, transforming growth factor-beta is released from juxtaglomerular cells and may act synergistically with angiotensin II to accentuate vasoconstriction and acute renal failure. Interaction of the renin-angiotensin system and transforming growth factor-beta has important clinical implications. The protective effect of inhibition of the renin-angiotensin system in experimental and human kidney diseases correlates closely with the suppression of transforming growth factor-beta production. This suggests that transforming growth factor-beta, in addition to blood pressure, should be a therapeutic target. Higher doses or different combinations of drugs that block the renin-angiotensin system or entirely new drug strategies may be needed to achieve a greater antifibrotic effect.

Salt Induces Myocardial and Renal Fibrosis in Normotensive and Hypertensive Rats

Abstract: Background—The detrimental effects of high dietary salt intake may not only involve effects on blood pressure and organ hypertrophy but also lead to tissue fibrosis independently of these factors. Methods and Results—The effect of a normal (1%) or high (8%) sodium chloride diet on myocardial and renal fibrosis was assessed by quantitative histomorphometry in spontaneously hypertensive rats (SHRs) and normotensive Wistar-Kyoto rats (WKYs). The effect of salt on transforming growth factor-β1 (TGF-β1) gene expression was assessed by Northern blot hybridization. A high-salt diet from 8 to 16 weeks of age resulted in increased blood pressure and left ventricular and renal hypertrophy in both WKYs and SHRs. Marked interstitial fibrosis was demonstrated in the left ventricle (LV), glomeruli, and renal tubules and in intramyocardial arteries and arterioles but not in the right ventricle. The collagen volume fraction increased significantly after high-salt diet in the LV, intramyocardial arteries and arterioles, g...

Pathologic fibrosis and connective tissue matrix in left ventricular hypertrophy due to chronic arterial hypertension in humans

Abstract: Objective To investigate pathologic fibrosis and connective tissue matrix in left ventricular hypertrophy due to chronic arterial hypertension in humans. Design and methods Seventeen human hearts were studied. Group 1 consisted of control hearts (four hearts, weighing 280 ± 40 g each), from subjects who had had no evidence of heart disease and for whom the diagnoses of death were noncardiac. Groups 2 (five hearts, weighing 440 ± 50 g each), 3 (five hearts, weighing 560 ± 50 g each), and 4 (three hearts, weighing 680 ± 60 g each) consisted of hearts from subjects who had had a history of systemic hypertension. All hearts had no valvular deformities and no evidence of ischemic disease at the postmortem examination. A cell-maceration method was employed to evaluate the myocardial connective matrix after removal of the nonfibrous elements of myocardial tissue, leaving behind a noncollapsed matrix, thus allowing a better three-dimensional view. Myocardial tissue was also processed for conventional light microscopic and morphometric studies. Results The minor transverse diameter of myocytes from hearts in groups 1-4 hearts were 13.7 ± 7.8, 23.7 ± 3.4, 26.6 ± 3.7, and 32.8 ± 5.8 μm, respectively. The volume fraction of fibrosis of the controls was 6.5%, whereas the volume fractions in hypertensive hearts increased progressively according to heart weight: 15.4, 22.9, and 31.1% for hearts in groups 2, 3, and 4, respectively. The most striking feature was the diffuse marked increase in amount of pericellular collagen weave fibers (endomysial matrix), parallel to the increase of heart weight The hypertrophied myocytes were encased in a dense weave of collagen fibrils continuous with those of adjacent myocytes. The muscle fibers in hypertrophied hearts were markedly larger than normal, although this was extremely variable from an area to another. Besides, a diffuse increase in the number of thick collagen fibers constituting broad bands and sheets of collagen surrounding disorganized muscle bundles (perimysial matrix) was observed. Scattered dense scar-like foci, apparently replacing areas of myocyte loss, could be seen, mainly on the periphery of muscle bundles. This latter finding was more commonly observed among hypertrophied hearts from group 3 and, mainly, among hypertrophied hearts of group 4. Importantly, a progressive disarray of the connective tissue skeleton of the myocardium could be seen in parallel to the progressive increase of cardiac hypertrophy. Conclusions The progressive accumulation of interstitial collagen fibers in left ventricular hypertrophy, in parallel to an increase in heart weight, can be expected to contribute to a spectrum of ventricular dysfunction involving either the diastolic or systolic phase of the cardiac cycle, or both, that is associated with the greater than normal arrhythmogenic risk for a hypertensive heart. Moreover, the methodology used is useful for studying the spatial organization of the collagen fibrils of the myocardium under normal and pathologic conditions.

Hepatocyte growth factor prevents renal fibrosis and dysfunction in a mouse model of chronic renal disease.

Abstract: Chronic renal disease (CRD) is generally thought to be incurable, except through renal transplantation, and the number of patients with CRD is on the increase. Glomerulosclerosis and tubulointerstitial fibrosis represent the morphological equivalent of end-stage CRD. In this study, we demonstrated the preventive effect of hepatocyte growth factor (HGF) on the progression of renal dysfunction and fibrosis, using a spontaneous mouse model for CRD (ICGN strain). The mice progressively developed glomerular sclerotic injury, tubular atrophy, and renal dysfunction until they were 17 wk of age. When recombinant HGF was injected into these mice during a 4-wk-period (from weeks 14-17 after birth), DNA synthesis of tubular epithelial cells was found to be 4.4-fold higher than in mice without HGF injection, thereby suggesting tubular parenchymal expansion promoted by HGF. Notably, HGF suppressed the expression of transforming growth factor-beta and of platelet-derived growth factor as well as myofibroblast formation in the affected kidney. Consequently, the onset of tubulointerstitial fibrosis was almost completely inhibited by HGF, while HGF attenuated the progression of glomerulosclerosis, both leading to preventing manifestation of renal dysfunction. From our results, supplement therapy with HGF may be taken into consideration as a novel option for prevention and treatment of CRD.

Transfer of Tumor Necrosis Factor-α to Rat Lung Induces Severe Pulmonary Inflammation and Patchy Interstitial Fibrogenesis with Induction of Transforming Growth Factor-β1 and Myofibroblasts

Abstract: Tumor necrosis factor-α is up-regulated in a variety of different human immune-inflammatory and fibrotic pulmonary pathologies. However, its precise role in these pathologies and, in particular, the mechanism(s) by which it may induce fibrogenesis are not yet elucidated. Using a replication-deficient adenovirus to transfer the cDNA of tumor necrosis factor-α to rat lung, we have been able to study the effect of transient but prolonged (7 to 10 days) overexpression of tumor necrosis factor-α in normal adult pulmonary tissue. We have demonstrated that local overexpression resulted in severe pulmonary inflammation with significant increases in neutrophils, macrophages, and lymphocytes and, to a lesser extent, eosinophils, with a peak at day 7. By day 14, the inflammatory cell accumulation had declined, and fibrogenesis became evident, with fibroblast accumulation and deposition of extracellular matrix proteins. Fibrotic changes were patchy but persisted to beyond day 64. To elucidate the mechanism underlying this fibrogenesis, we examined bronchoalveolar fluids for the presence of the fibrogenic cytokine transforming growth factor-β1 and tissues for induction of α-smooth muscle actin-rich myofibroblasts. Transforming growth factor-β1 was transiently elevated from day 7 (peak at day 14) immediately preceding the onset of fibrogenesis. Furthermore, there was a striking accumulation of myofibroblasts from day 7, with the most extensive and intense immunostaining at day 14, ie, coincident with the up-regulation of transforming growth factor-β1 and onset of fibrogenesis. Thus, we have provided a model of tumor necrosis factor-α-mediated pulmonary inflammation and fibrosis in normal adult lung, and we suggest that the fibrogenesis may be mediated by the secondary up-regulation of transforming growth factor-β1 and induction of pulmonary myofibroblasts.

Collagen Deposition in Large Airways May Not Differentiate Severe Asthma from Milder Forms of the Disease

Abstract: Chronic airway inflammation and remodeling, including fibrosis, have been proposed as important contributors to asthma pathophysiology. Previous studies of airway fibrosis have been performed mainly in mild and moderate asthmatics at the subepithelial "basement membrane" (SBM) level. The current study was designed to evaluate the large airway SBM thickness and submucosal collagen deposition, as measured by three different collagen staining methods, in endobronchial biopsies from 17 severe, nine moderate, and seven mild asthmatics, as well as eight normal control subjects. Tissue eosinophils and transforming growth factor-beta (TGF-beta) immunoreactivity were also examined. There were no statistically significant differences in the SBM thickness, submucosal collagen deposition, eosinophil numbers, or TGF-beta positive cells among the three groups of asthmatics and the normal control subjects. It was only when examining all asthmatics (n = 33) together, that a modestly thickened SBM (p = 0.04), as evaluated by collagen type III immunostaining, was observed as compared with normal control subjects. Despite this difference, no significant differences were found in the amount of submucosal collagen deposition and the number of eosinophils or TGF-beta expressing cells when comparing total asthmatics and normal control subjects. Additionally, no significant correlations were found between collagen deposition and eosinophil count, TGF-beta expression level, FEV1, or duration of asthma. These results suggest that although increased collagen deposition in the SBM at the large airway level is a characteristic of asthma, it may not explain the differences in severity of asthma.

Tubulointerstitial disease in aging: evidence for underlying peritubular capillary damage, a potential role for renal ischemia.

Abstract: Aging is associated with a progressive decline in renal function and the development of glomerulosclerosis and interstitial fibrosis. Although many studies have addressed the cellular mechanisms of age-related glomerulosclerosis, less is known about the tubulointerstitial fibrosis. In this study, aging (24 mo) rats develop tubulointerstitial fibrosis characterized by tubular injury and focal tubular cell proliferation, myofibroblast activation, macrophage infiltration with increased immunostaining for the adhesive proteins osteopontin and intercellular adhesion molecule-1, and collagen IV deposition. Aging rats demonstrated immunostaining for endothelial nitric oxide synthase (eNOSIII) in renal tubular epithelial cells and infiltrating mononuclear cells in areas of tubulointerstitial injury, with a relative loss of staining of the peritubular capillaries compared with young rats. The aging rats also displayed focal loss of peritubular capillaries (as noted by focally decreased RECA-1 and OX-2 staining) in areas of tubulointerstitial injury. The areas of fibrosis and hypocellularity were associated with increased apoptosis of tubular and interstitial cells compared with young (3 mo) rats (25.4 +/- 5.3 versus 3.5 +/- 2.5 TUNEL-positive cells/0.25 mm2 in old versus young rats, P = 0.0001). It is concluded that tubulointerstitial fibrosis in aging is an active process associated with interstitial inflammation and fibroblast activation. The progressive loss of cells in areas of fibrosis may be due to accelerated apoptosis. Furthermore, the tubulointerstitial injury may be the consequence of ischemia secondary to peritubular capillary injury and altered eNOS expression.

Anti-CD40 Ligand Antibody Treatment of SNF1 Mice with Established Nephritis: Preservation of Kidney Function

Abstract: Prior studies have demonstrated that treatment of young, prenephritic lupus-prone mice with Ab directed against CD40 ligand (CD40L) prolongs survival and decreases the incidence of severe nephritis. In this report, we show that for (SWR x NZB)F1 (SNF1) animals with established lupus nephritis, long-term treatment with anti-CD40L beginning at either 5.5 or 7 mo of age prolonged survival and decreased the incidence of severe nephritis. "Older" mice were chosen for these studies to more closely resemble the clinical presentation of patients with established renal disease. We show that age at the start of treatment, which typically correlates with severity of disease, is an important factor when determining an efficacious therapeutic protocol since animals that began treatment at 7 mo of age required a more aggressive treatment protocol than animals at 5.5 mo of age. Remarkably, several anti-CD40L-treated animals beginning treatment at age 5.5 mo demonstrated a decline in proteinuria, as opposed to increasing proteinuria levels seen in hamster IgG (HIg)-treated controls, and histologic examination of kidneys from anti-CD40L-treated mice revealed dramatically diminished inflammation, sclerosis/fibrosis, and vasculitis, in marked contrast to the massive inflammation and kidney destruction observed in control animals that received hamster IgG. Spleens from anti-CD40L-treated mice also exhibited markedly reduced inflammation and fibrosis compared with controls. Together, these results show that treatment of older, nephritic SNF1 animals with long-term anti-CD40L immunotherapy significantly prolongs survival, reduces the severity of nephritis, and diminishes associated inflammation, vasculitis, and fibrosis.

The cell biology of liver fibrogenesis - an imbalance of proliferation, growth arrest and apoptosis of myofibroblasts

Abstract: Fibrosis following liver damage and factors influencing this process are discussed with special reference to hepatic stellate cells and their transformation to myo- fibroblasts.

Altered Balance Between Matrix Metalloproteinases and Their Inhibitors in Experimental Biliary Fibrosis

Abstract: A rat model of common bile duct ligation (BDL)-induced hepatic fibrosis was used to assess the expression and activities of collagen-degrading proteinases and their inhibitors during the progression of fibrosis. Expression of four members of the matrix metalloproteinase (MMP) family (MMP-2/gelatinase A, MMP-3, MMP-9/gelatinase B, and MMP-13) and three tissue inhibitors of metalloproteinases-1, -2, and -3 (TIMP-1, TIMP-2, and TIMP-3) were evaluated by Northern blot analysis of RNA from liver tissue isolated at 0, 2, 5, 10, 20, and 30 days after either a BDL or sham operation. In addition, we analyzed free gelatinase and TIMP activities by zymography and reverse zymography, respectively. We found that the proteolytic activities of MMP-2 and MMP-9 increased by 2 days after ligation, reached maximal levels at day 10, and remained high through the study period, whereas the gelatinolytic activities in plasma were unchanged. The increase in gelatinase activities was accompanied by an increase in the TIMP mRNA transcripts. TIMP-1 transcripts appeared at day 2, increased until day 10, and remained elevated throughout the study period. TIMP-2 and TIMP-3 transcripts become detectable on day 10 and remained stable afterwards. No corresponding increase in TIMP protein activity was detected by reverse zymography. This appears to result from the formation of TIMP/MMP complexes. These findings indicate a likely surplus in the BDL model of fibrosis of free gelatinases as compared with the TIMPs. Thus, excessive TIMP production is not a sufficient explanation for the observed extracellular matrix accumulation, but complex changes in the local MMP/TIMP balance may underlie the pathomechanisms of fibrosis.

Early Induction of Transforming Growth Factor-β via Angiotensin II Type 1 Receptors Contributes to Cardiac Fibrosis Induced by Long-term Blockade of Nitric Oxide Synthesis in Rats

Abstract: We previously reported that the chronic inhibition of nitric oxide (NO) synthesis increases cardiac tissue angiotensin-converting enzyme expression and causes cardiac fibrosis in rats. However, the mechanisms are not known. Transforming growth factor-beta (TGF-beta) is a key molecule that is responsible for tissue fibrosis. The present study investigated the role of TGF-beta in the pathogenesis of cardiac fibrosis. The development of cardiac fibrosis by oral administration of the NO synthesis inhibitor N(omega)-nitro-L-arginine methyl ester (L-NAME) to normal rats was preceded by increases in mRNA levels of cardiac TGF-beta1 and extracellular matrix (ECM) proteins. TGF-beta immunoreactivity was increased in the areas of fibrosis. Treatment with a specific angiotensin II type 1 receptor antagonist, but not with hydralazine, completely prevented the L-NAME-induced increases in the gene expression of TGF-beta1 and ECM proteins and also prevented cardiac fibrosis. Intraperitoneal injection of neutralizing antibody against TGF-beta did not affect the L-NAME-induced increase in TGF-beta1 mRNA levels but prevented an increase in the mRNA levels of ECM protein. These results suggest that the early induction of TGF-beta1 via the angiotensin II type 1 receptor plays a major role in the development of cardiac fibrosis in this model.

Prevention of late effects of irradiation lung damage by manganese superoxide dismutase gene therapy.

Abstract: Organ and tissue damage caused by ionizing irradiation is directly related to volume irradiated, total dose and dose rate. The acute effects are in part mediated by cellular activation of early response genes, including those for transcriptional activators of genes for humoral cytokines. In the lung, as in other organs, recovery from the acute effects of ionizing irradiation does not always correlate with prevention of the critical fate effects, including fibrosis, which contribute to organ failure. An interventional technique by which to protect normal organs from the late effects of irradiation has remained elusive. We now demonstrate that overexpression of a transgene for human manganese superoxide dismutase (MnSOD) delivered by plasmid-liposome, or adenovirus to the lungs of C57BL/6J or Nu/J mice, respectively, before irradiation exposure, decreases the late effects of whole lung irradiation (organizing alveolitis/fibrosis). These data provide a rational basis for the design of gene therapy approaches to organ protection from irradiation damage.

Pathogenesis of fibrosis: type 1 collagen and the skin.

Abstract: This review on the pathogenesis of fibrosis emphasizes the similarities between tissue repair, a tightly regulated salutary biological response, and fibrosis, an unregulated pathological process. It focuses on the transcriptional regulation of type I collagen, the role of cytokines in fibroblast activation, integrins as examples of cell-matrix signaling pathways, and the heterogeneity of fibroblast populations as factors contributing to fibrosis. Tissue remodeling and the role of matrix metalloproteinases and metalloproteinase inhibitors are mentioned briefly. The capacity of extracellular matrix to modulate cellular function is a recurring theme.