Treatment of idiopathic pulmonary fibrosis: a position paper from a Nordic expert group.

Idiopathic pulmonary fibrosis (IPF) is a fatal progressive lung disease occurring in adults. In the last decade, the results of a number of clinical trials based on the updated disease classification have been published. The registration of pirfenidone and nintedanib, the first two pharmacological treatment options approved for IPF, marks a new chapter in the management of patients with this disease. Other nonpharmacological treatments such as lung transplantation, rehabilitation and palliation have also been shown to be beneficial for these patients. In this review, past and present management is discussed based on a comprehensive literature search. A treatment algorithm is presented based on available evidence and our overall clinical experience. In addition, unmet needs with regard to treatment are highlighted and discussed. We describe the development of various treatment options for IPF from the first consensus to recent guidelines based on evidence from large-scale, multinational, randomized clinical trials, which have led to registration of the first drugs for IPF.

Health effects of a subway environment in healthy volunteers.

Environmental particle exposure, often estimated as the particulate mass of particles with a diameter <10 microm, <2.5 microm or <1 microm (PM(10), PM(2.5) or PM(1)), is known to have a negative impact on the health of the population. Little is known about how the size and origin of particles influence the effects. We have previously shown that exposure to a road tunnel environment causes a cellular inflammatory response in the airways of healthy individuals. In the present study, our aim was to investigate potential airway health effects from exposure to a subway environment. 20 healthy volunteers were exposed to a subway and a control environment for 2 h, followed by measurements of lung function and the inflammatory response in the lower airways (bronchoscopy) and in the peripheral blood. No cellular response was found in the airways after exposure to the subway environment. In the blood, we found a statistically significant increase in fibrinogen and regulatory T-cells expressing CD4/CD25/FOXP3. Subway and road tunnel environments have similar levels of PM(10) and PM(2.5), whilst the concentrations of ultrafine particles, nitrogen monoxide and dioxide are lower in the subway. Although no cellular response was detected, the findings indicate a biological response to the subway environment. Our studies show that using gravimetric estimates of ambient particulate air pollution alone may have clear limitations in health-risk assessment.

Eosinophil cationic protein stimulates migration of human lung fibroblasts in vitro.

Asthma is characterized by eosinophilic inflammation and remodelling of the airways. Eosinophil cationic protein (ECP) is a protein released by activated eosinophils and the hypothesis that ECP contributes to the development of structural changes in the airways of asthmatics has been posed. Fibroblast recruitment is an important step in the remodelling process, and we therefore put the question whether ECP stimulates migration of human lung fibroblasts. Human peripheral eosinophils isolated from buffycoats from healthy individuals were cultured and conditioned media (CM) were collected. Native ECP was extracted from human peripheral eosinophils by gel filtration, ion-exchange and chelating chromatography. The ability of eosinophil CM and ECP to stimulate fibroblast migration was determined using the 48-well Boyden chamber. ECP concentrations in CM were assayed by ECP-CAP-FEIA. Both CM and ECP significantly stimulated fibroblast migration (48.4+/-cells/field versus 33+/-2 and 36+/-6 versus 25+/-4; P<0.001 and 0.05 respectively) in a time- and concentration-dependent manner. Adding neutralizing ECP antibodies attenuated fibroblast migration induced by both ECP as well as CM. ECP stimulates migration of human lung fibroblasts, suggesting a potential mechanism for eosinophils in the fibrotic response. This may be an important mechanism by which ECP promotes remodelling of extracellular matrix leading to airway fibrosis in asthmatics.

Increased levels of nerve growth factor in the airways of patients with sarcoidosis.

OBJECTIVES: Nerve growth factor (NGF) is a potent neuronal growth factor with inflammatory properties that recently has been proposed to be of importance in airway pathology. A role for NGF in the inflammatory granulomatous lung disease sarcoidosis is not well elucidated. The aims of this study were to investigate the secreted levels of NGF in bronchoalveolar lavage fluid (BALF) from sarcoidosis patients compared with patients with resolved disease, patients with another granulomatous disease--chronic beryllium disease (CBD)--and healthy subjects and also to investigate the relationship between NGF levels and markers of inflammation. METHODS AND RESULTS: NGF levels in BALF from 56 patients with active sarcoidosis (22 with Löfgren's syndrome), nine subjects with resolved sarcoidosis, six patients with CBD, and 31 healthy subjects were compared. A 10-fold elevation of NGF levels was found in patients with active sarcoidosis compared with subjects with clinically resolved sarcoidosis, patients with CBD and healthy subjects. In sarcoidosis patients, positive correlations between concentrations of NGF and lymphocytes, eosinophils and interferon-gamma, interleukin (IL)-4, IL-10, IL-12 were found. CONCLUSIONS: We demonstrate that secreted levels of NGF are markedly enhanced in the airways in active pulmonary sarcoidosis. Furthermore, a relationship between NGF and pulmonary inflammation in sarcoidosis is supported.

Human T cells stimulate fibroblast-mediated degradation of extracellular matrix in vitro.

Several chronic diseases are characterized by inflammation, T cell recruitment and tissue remodelling. We hypothesized that activated T cells may stimulate remodelling of extracellular matrix (ECM) in vitro. Total T cells (CD3+) as well as CD4+ and CD8+ subsets were isolated from peripheral blood and stimulated, after which conditioned media (CM) were obtained. CM was added to human lung fibroblasts in three-dimensional collagen gels and the area of gels was measured daily. Hydroxyproline was determined as a measure of collagen degradation in the gels. Matrix metalloproteinase (MMP) activity in the culture media was analysed by gelatine zymography. Cytokine secretion of stimulated CD4+ and CD8+ T cells was analysed. CD3+ CM augmented collagen gel contraction in a time- and dose-dependent manner (P < 0.0001). CD4+ T cell CM was more potent than CD8+ T cell CM (P < 0.001). CD3+ CM and CD4+ T cell CM, but not CD8+ T cell CM, stimulated fibroblast-mediated collagen degradation and MMP-9 activity. A broad-spectrum MMP-inhibitor added to the culture system inhibited both gel contraction and MMP activity. Activated CD4+ T cells secreted significantly more tumour necrosis factor (TNF) and interleukin (IL)-6 compared to CD8+ T cells. CD3+ CM from patients with chronic obstructive pulmonary disease stimulated fibroblast-mediated collagen gel contraction to the same magnitude as CD3+ CM from healthy controls. In conclusion, activated CD4+ T cells can stimulate fibroblast-mediated degradation of ECM in vitro. This could be a mechanism by which activated T cells stimulate degradation of lung tissue leading to pulmonary emphysema.

Smoking increases peptidylarginine deiminase 2 enzyme expression in human lungs and increases citrullination in BAL cells.

OBJECTIVES: A gene-environment interaction between HLA-DR shared epitope genes and smoking in anti-cyclic citrullinated peptide antibody-positive rheumatoid arthritis (RA) has been reported. Identification of citrullinated proteins in bronchoalveolar lavage (BAL) cells from smokers has led to the suggestion that citrullination induced by smoking might be the first step in the pathogenic chain of RA. OBJECTIVE: To confirm and extend these findings. METHODS: Immunohistochemistry was performed on BAL cells and bronchial mucosal biopsy sections obtained through bronchoscopy from 14 healthy smokers and 16 healthy non-smokers. Two antibodies recognising citrullinated proteins, two antibodies recognising peptidylarginine deiminase (PAD)2 enzyme and one recognising PAD4 enzyme were used. RESULTS: Citrullinated proteins are upregulated in BAL cells of healthy smokers compared with healthy non-smokers. This was associated with higher expression of the PAD2 enzyme. The same level of citrullinated proteins was present in bronchial mucosal biopsy specimens of healthy smokers and non-smokers, despite higher expression of PAD2 in smokers. CONCLUSION: This study provides evidence that smoking enhances PAD2 expression in the bronchial mucosal and alveolar compartment, with consequent generation of citrullinated proteins in the latter. Smoking is an environmental factor that may lead to citrulline autoimmunity in genetically susceptible subjects.

Measures of bronchodilator response of FEV1, FVC and SVC in a Swedish general population sample aged 50-64 years, the SCAPIS Pilot Study.

BACKGROUND: Data are lacking from general population studies on how to define changes in lung function after bronchodilation. This study aimed to analyze different measures of bronchodilator response of forced expiratory volume in 1 second (FEV1), forced vital capacity (FVC) and slow vital capacity (SVC). MATERIALS AND METHODS: Data were derived from the Swedish Cardiopulmonary Bioimage Study (SCAPIS) Pilot study. This analysis comprised 1,050 participants aged 50-64 years from the general population. Participants were investigated using a questionnaire, and FEV1, FVC and SVC were recorded before and 15 minutes after inhalation of 400 µg of salbutamol. A bronchodilator response was defined as the relative change from baseline value expressed as the difference in units of percent predicted normal. Predictors of bronchodilator responses were assessed using multiple linear regression models. Airway obstruction was defined as FEV1/FVC ratio below lower limit of normal (LLN) before bronchodilation, and COPD was defined as an FEV1/FVC ratio below LLN after bronchodilation. Physician-diagnosed asthma was defined as an affirmative answer to "Have you ever had asthma diagnosed by a physician?". Asymptomatic never-smokers were defined as those not reporting physician-diagnosed asthma, physician-diagnosed COPD or emphysema, current wheeze or chronic bronchitis and being a lifelong never-smoker. RESULTS: Among all subjects, the greatest bronchodilator responses (FEV1, FVC and SVC) were found in subjects with asthma or COPD. The upper 95th percentile of bronchodilator responses in asymptomatic never-smokers was 8.7% for FEV1, 4.2% for FVC and 5.0% for SVC. The bronchodilator responses were similar between men and women. In a multiple linear regression model comprising all asymptomatic never-smokers, the bronchodilator response of FEV1 was significantly associated with airway obstruction and height. CONCLUSION: When the bronchodilator response in asymptomatic never-smokers is reported as the difference in units of predicted normal, significant reversibility of FEV1, FVC and SVC to bronchodilators is ~9%, 4% and 5%, respectively.

Quenching of intracellular autofluorescence in alveolar macrophages permits analysis of fluorochrome labelled surface antigens by flow cytofluorometry.

We report a new technique in which the autofluorescence of alveolar macrophages from smokers is quenched by crystal violet. This technique permits immunostaining of surface antigens of these cells and enables the stained cells to be analysed by flow cytofluorometry. The variable solubility of crystal violet makes it important to characterize the crystal violet solution by its quenching properties and not rely on the assumed concentration of dissolved dye. High concentrations of crystal violet lowered the number of cells and gave a decreased amount of surface antigen (CD11b). However, a lower concentration of crystal violet could be used if the cells were fixed with paraformaldehyde (4%) and the membranes were permeabilized with n-octyl-beta-D-glucopyranoside (0.6%). Using a phagocytic model with FITC-conjugated particles we were able to show that this treatment gave an efficient permeabilization of phagolysosomal membranes.

Altered expression of CD11b/CD18 and CD62L on human monocytes after cell preparation procedures.

We have investigated the effect of different cell preparation procedures on the surface expression of CD11b/CD18 and CD62L on human monocytes. Both EDTA and heparin anticoagulated blood were used as sources for leukocytes. The monocytes were analysed by flow cytometry in a mixed leukocyte suspensions obtained after ammonium chloride mediated lysis and in mononuclear cell suspension prepared by density gradient centrifugation (Ficoll-Paque) performed both at 4 degrees C and at 20 degrees C. Monocytes from heparinized blood had a higher expression of CD11b/CD18 and a more pronounced inter-individual variation than monocytes from EDTA blood. Monocytes isolated by Ficoll-Paque had a higher degree of ex vivo activation by means of altered expression of CD11b/CD18 and CD62L compared to monocytes prepared by ammonium chloride mediated lysis. This was more pronounced when the isolation procedure was performed at 20 degrees C. Our findings indicate that monocytes prepared by ammonium chloride mediated lysis of EDTA blood and with the cell handling temperature kept at 4 degrees C are exposed to the smallest ex vivo modulation by means of receptor alteration. An awareness of ex vivo modulation by different cell preparation procedures is of importance especially when comparing the expression of functional receptors on leukocytes of disparate origin.

Adhesion properties of human alveolar macrophages with respect to extracellular matrix components and chemotactic agonists.

Adherence has an essential impact on the differentiation and activation of tissue dwelling monocytes/macrophages. We have considered the effect of selected chemotactic agonists (fMLP, RANTES, IL-8) on the adhesion properties of human alveolar macrophages prepared by bronchoalveolar lavage. The macrophages were co-incubated in buffer alone or buffer supplemented with respective agonist, for different time points, in culture wells precoated with albumin, vitronectin and fibronectin, respectively. The macrophages displayed a gradual increase in adhesion in all three surfaces and discriminated between the different matrix components, but did not respond to the selected agonists with increased adhesion.

Smoking cessation rapidly reduces cell recovery in bronchoalveolar lavage fluid, while alveolar macrophage fluorescence remains high.

Bronchoalveolar lavage (BAL) was performed in smokers (22.6 +/- 7.8 pack-years) before (n = 18) and 1 (n = 14), 3 (n = 13), 6 (n = 11), 9 (n = 9), and 15 (n = 8) months after smoking cessation. The recovery of the BAL fluid increased after smoking cessation (p less than 0.05). The total number of cells and the cell concentration were significantly lower already at one month (p less than 0.05 and p less than 0.01, respectively), and this decline was more pronounced at the following lavages. By using flow cytofluorometry, alveolar macrophage (AM) fluorescence was quantified, since it is known that AMs lavaged from smokers have an increased fluorescence, due to interaction with fluorescent substances in the inhaled smoke. Not until six months after smoking cessation was a significant (p less than 0.05) decrease in AMs fluorescence noted. At 15 months, the fluorescence was still increased, with great individual variations, compared with AMs from nonsmokers. The decline in fluorescence of AMs after smoking cessation was negatively correlated to the previous cigarette consumption. The absence of new, low fluorescent cells in the BAL fluid, despite a slow, but significant decrease in the fluorescence intensity of the whole cell population, suggests that the fluorescent material is redistributed from older AMs to newly recruited cells. These substances can thus remain in the alveolar space for a longer time than the estimated life span of the AMs.

Clara cell secretory protein. Levels in BAL fluid after smoking cessation.

STUDY OBJECTIVES: The bronchiolar Clara cell is a major target for tobacco smoke exposure. To improve our understanding of the putative regenerative/repair mechanism(s) in the bronchiolar epithelium, we measured the levels of the Clara cell secretory protein (CCSP) in BAL fluid in healthy volunteers following smoking cessation. DESIGN: BAL was performed before smoking cessation, and at 1, 3, 6, 9, and 15 months following smoking cessation, in eight healthy volunteers with a previous mean cigarette consumption of 19 pack-years. The levels of CCSP in BAL fluid were assessed in immunoblotting experiments using an antibody against human CCSP. RESULTS: Significantly (p < 0.05) higher levels of CCSP in BAL fluid were observed at 3, 6, and 9 months after smoking cessation, while the levels of CCSP in BAL fluid at 15 months after smoking cessation were the same as those before smoking cessation. CONCLUSIONS: Despite the long history of smoking among patients in the present study group, signs of early regeneration in the bronchiolar epithelium were noted, in that the levels of CCSP in BAL fluid were elevated at the indicated time points following smoking cessation. Furthermore, we propose that the insult to the bronchiolar epithelium made by cigarette smoking caused the levels of CCSP in the BAL fluid at 15 months after smoking cessation to return to the levels noted before smoking cessation. The present study suggests a role for CCSP as a marker for nonciliated bronchiolar cell function.

Different cell surface and phagocytic properties in mononuclear phagocytes from blood and alveoli. A comparative study of blood monocytes and alveolar macrophages from human nonsmokers using flow cytofluorometry.

Flow cytofluorometry was used to compare blood monocytes (BMs) and alveolar macrophages (AMs) from the same nonsmoking subject (n = 13). Autofluorescence was quantified, cell surface markers (HLA-DR, CR3) were detected by monoclonal antibodies, and phagocytic ability was determined using C3b-coated yeast particles. AMs expressed more HLA-DR (p less than 0.001) and CR3 (p less than 0.01) on their surfaces than did BMs. The phagocytic capacity was enhanced in AMs compared to BMs (p less than 0.001) and the cells showed an increased autofluorescence (p less than 0.001) in the alveoli compared to blood. The findings suggest that the mononuclear phagocyte is activated when it migrates from blood to alveoli in order to adapt to the milieu in the alveolar space.

Detection of extrathoracic manifestations in sarcoidosis with somatostatin analogue scintigraphy.

BACKGROUND AND AIM OF WORK: Scintigraphy using a long lived radiolabelled somatostatin analogue [111In-DTPA-D-Phe1]-octreotide (OctreoScan) has previously been shown to be useful in the detection and management of neuroendocrine tumours, as well as in the imaging of various other malignant tumours. It was recently reported that the radiopharmaceutical accumulates also in the granulomatous lesions in Wegener's disease and in sarcoidosis. The present study was undertaken in order to evaluate the usefulness of the technique in detection of extrathoracic manifestations. METHODS: OctreoScan scintigraphy was performed in 5 patients with biopsy-proven sarcoidosis. A patient with a familial history of multiple endocrine neoplasia served as control. RESULTS: In 4/5 patients previously unknown granulomas were registered, and in the remaining subject the findings at the physical examination were confirmed. CONCLUSIONS: We conclude that somatostatin analogue scintigraphy may be helpful in finding extrathoracic granulomatous lesions in sarcoidosis, thus providing good prerequisites for focused biopsy attempts.

ECG-abnormalities in Japanese and Swedish patients with sarcoidosis. A comparison.

BACKGROUND AND AIM OF THE WORK: ECG abnormalities are more common in patients with sarcoidosis than in controls. The incidence of cardiac sarcoid granulomas in the Japanese population has been found to be higher than that seen in Caucasians. We compared the prevalence of ECG abnormalities in Japanese and Swedish patients with sarcoidosis. METHODS: Twelve-lead routine ECG's were compared between consecutive patients (134 Japanese and 149 Swedish) of similar age with histologically verified sarcoidosis or a high clinical probability of the disease and a history of no more than 12 months before the ECG. RESULTS: There was no statistically significant difference in the prevalence of first degree AV block, ST-T-segment abnormalities, right bundle branch block (RBBB) and left anterior block (LAH) in Japanese and Swedish patients. Among the Swedes, the results were compared with those of a smaller group (n = 29) of older patients with a longer disease course. In these few patients LAH and RBBB occurred more frequently than in patients with a recent diagnosis. CONCLUSIONS: ECG abnormalities in patients with sarcoidosis seem to be of similar frequency in Japan and Sweden. ST-T changes and first degree AV block would appear early in the course of the disease, whereas more pronounced conduction defects may appear later.

Transient increases in albumin and hyaluronan in bronchoalveolar lavage fluid after quitting smoking: possible signs of reparative mechanisms.

Inhalation of tobacco smoke results in an accumulation of cells in the lower respiratory tract. The inflammatory response in the alveoli and lung interstitium may also be reflected by increased bronchoalveolar lavage (BAL) fluid concentrations of extracellular matrix components. The present study investigated the influence of smoking on the BAL fluid concentrations of albumin (ALB), hyaluronan (HA) and fibronectin (FN). Lavage fluids from 18 smokers were analysed before and at 1, 3, 6, 9 and 15 months after smoking cessation. Never-smokers (n = 112) served as a reference group. The total cell concentration and the concentrations of macrophages, lymphocytes, neutrophils and eosinophils were higher (P < 0.001-0.01) in smokers' BAL fluid than in never-smokers', but the values returned to normal within 9 months of smoking cessation. The HA concentration was higher (P < 0.001) in smokers' than in never-smokers' BAL fluid, but FN and ALB did not differ. Transient increases in the concentrations of ALB and HA (P < 0.01 for both) was observed within 6 months of smoking cessation. These findings indicate a temporary heightened alveolar-capillary permeability and an increased production and/or degradation of HA, being enhanced following smoking cessation. The findings probably reflect an initiation of a reparative process.

Metabolic activity in human alveolar macrophages increases after cessation of smoking.

Alveolar macrophages (AMs) were recruited by bronchoalveolar lavage (BAL) from human smokers before and one, three, and six months after smoking cessation. The metabolic activity of the AM was quantified as luminol-enhanced chemiluminescence (CL) both at rest and after in vitro stimulation with phorbol myristate acetate (PMA). The resting CL values did not differ before and after smoking cessation. The activity after PMA stimulation was unaltered at one and three months. However, the maximal metabolic response, as well as the rate, were significantly (P < 0.02 and P < 0.01, respectively) higher at six months, compared to prior smoking cessation. In addition, the time to reach the maximal peak was reduced after six smoke-free months, indicating a more rapid cell activation. The cell concentration in the BAL-fluid decreased (P < 0.001) as soon as after one smoke-free month and remained low at the following lavages. The lower metabolic response one and three months after smoking cessation, and the increased response six months after, together with a rapid normalization of the cell concentration in the BAL fluid, may be explained by the persistence of tobacco-smoke particles in the alveolar space, which could influence cell activity.

Co-cultured human mast cells stimulate fibroblast-mediated contraction of collagen gels.

In the current study, we asked whether mast cells might modulate remodeling of extracellular matrix by affecting fibroblast-mediated contraction of three-dimensional collagen gels. Mast cells and human lung fibroblasts were co-cultured in floating type I collagen gels. The area of the gels was measured by an image analyzer. Mast cells in co-culture augmented fibroblast contractility (P < 0.001) in a time- and concentration dependent manner. The tryptase inhibitor bis(5-amidino-2-benzimidazo-lyl)methane (BABIM) were unable to block the augmented fibroblast contractility induced by co-cultured mast cells and tryptase added alone in the culture system had no effect on contractility, suggesting that other mediators besides tryptase might be involved. The amount of collagen in dissolved gels, measured as hydroxyproline, did not change after co-culture indicating that degradation of collagen may not be a major mechanism. Our findings support the hypothesis that the activity of mast cells may drive rearrangement of extracellular matrix and this and could subsequently lead to fibrosis and tissue dysfunction.

Glucocorticoids and TGF-beta1 synergize in augmenting fibroblast mediated contraction of collagen gels.

TGF-beta plays a central role in the initiation and progression of pulmonary fibrosis. Glucocorticoids are frequently used to treat fibrotic diseases, but beneficial effects are often modest. Both TGF-beta and glucocorticoids have been reported to increase fibroblast contraction of native collagen gels, a model of fibrotic tissue remodeling. Therefore, we sought to determine how glucocorticoids interact with TGF-beta in this system. In this study, human fetal lung fibroblasts (HFL-1) were pretreated with or without TGF-beta for 72 h before they were cast into type I collagen gels. Various concentrations of glucocorticoids (budesonide or hydrocortisone) were added at the time of casting. Gel size was then monitored at different times after gel release. The surrounding media were collected for the assay of prostaglandin E2 (PGE2) and the cell lysates were analyzed for cyclooxygenase (COX) expression by immunoblot. Glucocorticoids alone significantly enhanced fibroblast-mediated contraction of collagen gels (P < 0.01) and dose-dependently inhibited PGE2 release by HFL-1 fibroblasts. TGF-beta significantly augmented gel contraction but also induced a 30% increase in PGE2 release and increased the expression of COX-1. Glucocorticoids inhibited TGF-beta1 induced-PGE2 release, and enhanced TGF-beta augmented gel contraction without significantly affecting TGF-beta augmented COX-1 expression. Indomethacin, a COX inhibitor, increased TGF-beta augmented gel contraction but had no further effect when added together with glucocorticoids. Thus, glucocorticoids can synergize with TGF-beta in augmenting fibroblast mediated collagen gel contraction through the inhibition of PGE2 production. Such interactions between glucocorticoids and TGF-beta may account, in part, for the lack of response of fibrotic diseases to glucocorticoids.

Red blood cells stimulate human lung fibroblasts to secrete interleukin-8.

Following lung injury, red blood cells (RBC) may interact with extracellular matrix (ECM). Fibroblasts, the resident cell in the ECM, have the capacity to produce and secrete a variety of mediators including interleukin-8 (IL-8). In the present study we hypothesized that RBC, or soluble factors released from them, may stimulate IL-8 production by fibroblasts. Fibroblasts were cultured in a three-dimensional collagen gel culture system in the presence or absence of RBC or conditioned medium from RBC (RBC-CM). IL-8 release from fibroblasts was significantly increased when cultured with RBC or RBC-CM and both tumor necrosis factor-alpha (TNF-alpha) and interleukin-1beta (IL-1beta) further stimulated this IL-8 secretion. The enhanced production of IL-8 within fibroblasts was accompanied by increased IL-8 mRNA expression. To evaluate whether RBC-fibroblast interaction may lead to recruitment of neutrophils, a functional migration assay was performed. RBC and RBC-CM, in the presence of IL-1beta and TNF-alpha, increased the transmigration of neutrophils. Our results indicate that RBC, when interacting with ECM, may participate in the recruitment of inflammatory cells by stimulating fibroblasts to secrete IL-8. This might be an important mechanism regulating tissue repair after injury.