Intraluminal fibromyxoid lesions in bronchiolitis obliterans organizing pneumonia are highly capillarized

Update on cryptogenic organizing pneumonia

Cryptogenic organizing pneumonia (COP) is a form of idiopathic interstitial pneumonia that results from the pulmonary reaction to various unidentified injuries. Secondary organizing pneumonia is diagnosed when the triggering factor has been identified; it is mainly caused by infections, toxic substance exposure, drugs, connective tissue diseases, malignancies, autoimmune diseases, bone marrow, or organ transplantation, and radiotherapy. There has been an increase in the number of reports of drug-induced organizing pneumonia (OP). New biological therapies, interferon, monoclonal antibodies, anti-interleukin antibodies, and PD1/PDL-1 inhibitors may induce this specific pulmonary reaction. The classical form of COP is usually subacute and does not manifest as severe disease. Patients maintain sufficient respiratory function, and treatment with steroids is usually effective. Several specific forms of OP (e.g., the cicatricial variant or acute fibrinous type) have distinct clinical and histological features, require higher doses of immunosuppressive drugs, and have a worse prognosis. In the era of administering steroid-sparing therapies for the treatment of interstitial lung diseases, connective tissue dases, and other conditions, it is important to emphasize this type of therapy for patients with COP.

Cryptogenic organising pneumonia: current understanding of an enigmatic lung disease

Organising pneumonia (OP) is currently recognised as a nonspecific lung injury response that is associated with a variety of imaging patterns obtained with high-resolution computed tomography (HRCT) of the chest and is characterised histopathologically by the presence of inflammatory cells and a connective tissue matrix within distal airspaces of the lungs. OP is associated with many conditions that include connective tissue disorders, various infections, drug reactions, hypersensitivity pneumonitis and aspiration. When OP cannot be linked to an associated condition and appears to be idiopathic, it is termed cryptogenic organising pneumonia.

Shifting gears: the search for group 3 pulmonary hypertension treatment

PURPOSE OF REVIEW

Treatment options for Group 3 pulmonary hypertension, characterized as secondary to chronic hypoxia or lung disease, remain an elusive holy grail for physicians and patients alike. Despite increasing identification and investigation into this pulmonary vasculopathy group with the second-highest frequency and highest mortality, there are no therapeutic interventions that offer the significant improvements in morbidity and mortality comparable to those benefiting other pulmonary hypertension groups including pulmonary arterial hypertension. This review examines the data on available and emerging Group 3 pulmonary hypertension treatments.

RECENT FINDINGS

Pulmonary vasodilators have yielded equivocal results in this patient population, although recent evidence shows modestly improved outcomes with inhaled treprostinil in interstitial lung disease-associated pulmonary hypertension. With pulmonary vasodilators providing limited benefit, emerging data support the right ventricle as a potential treatment target in Group 3 pulmonary hypertension.

SUMMARY

Group 3 pulmonary hypertension is associated with significant morbidity and mortality. Pulmonary vasodilators offer only limited haemodynamic and exertional benefits, and lung transplantation remains the only cure for this deadly disease. The right ventricle may provide a novel intervention target.

Artificial intelligence identifies inflammation and confirms fibroblast foci as prognostic tissue biomarkers in idiopathic pulmonary fibrosis

A large number of fibroblast foci (FF) predict mortality in idiopathic pulmonary fibrosis (IPF). Other prognostic histological markers have not been identified. Artificial intelligence (AI) offers a possibility to quantitate possible prognostic histological features in IPF. We aimed to test the use of AI in IPF lung tissue samples by quantitating FF, interstitial mononuclear inflammation, and intra-alveolar macrophages with a deep convolutional neural network (CNN). Lung tissue samples of 71 patients with IPF from the FinnishIPF registry were analyzed by an AI model developed in the Aiforia® platform. The model was trained to detect tissue, air spaces, FF, interstitial mononuclear inflammation, and intra-alveolar macrophages with 20 samples. For survival analysis, cut-point values for high and low values of histological parameters were determined with maximally selected rank statistics. Survival was analyzed using the Kaplan-Meier method. A large area of FF predicted poor prognosis in IPF (p = 0.01). High numbers of interstitial mononuclear inflammatory cells and intra-alveolar macrophages were associated with prolonged survival (p = 0.01 and p = 0.01, respectively). Of lung function values, low diffusing capacity for carbon monoxide was connected to a high density of FF (p = 0.03) and a high forced vital capacity of predicted was associated with a high intra-alveolar macrophage density (p = 0.03). The deep CNN detected histological features that are difficult to quantitate manually. Interstitial mononuclear inflammation and intra-alveolar macrophages were novel prognostic histological biomarkers in IPF. Evaluating histological features with AI provides novel information on the prognostic estimation of IPF.

[Cryptogenic organizing pneumonia]

INTRODUCTION

Organizing pneumonia is a particular type of inflammatory reaction of the lung which gives rise to a clinico-pathological syndrome. It is called "secondary" when a cause such as an infection, a drug toxicity, or a connective tissue disease can be identified, or "cryptogenic" when no cause is identified. The clinical picture is usually characterized by the subacute onset of fever, fatigue, cough and dyspnea, with multiple subpleural areas of consolidation on thoracic imaging.

STATE OF THE ART

Organizing pneumonia is characterised by the presence of buds of endoalveolar connective tissue. These result from an injury to the alveolar epithelium, followed by the deposition of fibrin in the alveolar spaces, and the migration of fibroblasts which produce a myxoid endoalveolar matrix. A remarkable feature of organizing pneumonia is the complete disappearance of these endoalveolar buds with corticosteroid treatment, in sharp contrast with what is seen in pulmonary fibrosis. The clinical response to corticosteroids is usually prompt and excellent. Relapses are frequent but usually benign.

PERSPECTIVES AND CONCLUSION

As the clinical, imaging and pathological characteristics of organizing pneumonia are now well established, many questions remain unanswered, such as the mechanisms involved in the complete reversibility of the pulmonary lesions, and the role of steroid-sparing treatments such as immunomodulatory macrolides.

Lymphangiogenesis and Lesion Heterogeneity in Interstitial Lung Diseases

The lymphatic system has several physiological roles, including fluid homeostasis and the activation of adaptive immunity by fluid drainage and cell transport. Lymphangiogenesis occurs in adult tissues during various pathologic conditions. In addition, lymphangiogenesis is closely linked to capillary angiogenesis, and the balanced interrelationship between capillary angiogenesis and lymphangiogenesis is essential for maintaining homeostasis in tissues. Recently, an increasing body of information regarding the biology of lymphatic endothelial cells has allowed us to immunohistochemically characterize lymphangiogenesis in several lung diseases. Particular interest has been given to the interstitial lung diseases. Idiopathic interstitial pneumonias (IIPs) are characterized by heterogeneity in pathologic changes and lesions, as typified by idiopathic pulmonary fibrosis/usual interstitial pneumonia. In IIPs, lymphangiogenesis is likely to have different types of localized functions within each disorder, corresponding to the heterogeneity of lesions in terms of inflammation and fibrosis. These functions include inhibitory absorption of interstitial fluid and small molecules and maturation of fibrosis by excessive interstitial fluid drainage, caused by an unbalanced relationship between capillary angiogenesis and lymphangiogenesis and trafficking of antigen-presenting cells and induction of fibrogenesis via CCL21 and CCR7 signals. Better understanding for regional functions of lymphangiogenesis might provide new treatment strategies tailored to lesion heterogeneity in these complicated diseases.

Organizing Pneumonias

Organizing pneumonia is a particular type of inflammatory and reparative reaction of the lung parenchyma characterized by fibroblast proliferation in the distal airspaces with overall preservation of the lung architecture. When microscopic, it is an asymptomatic and nonspecific reaction of little clinical significance accompanying many pathological processes. When macroscopic and affecting large portions of the lung parenchyma, it manifests by restrictive ventilatory defect and gas exchange impairment leading to dyspnea, cough, hypoxemia, alveolar opacities at chest imaging, and symptoms of systemic inflammation such as fever, malaise, and weight loss. This picture constitutes the clinico-pathological syndrome of organizing pneumonia, which has been recognized and characterized as a distinct entity in the past 30 years. Although the classical features of organizing pneumonia are increasingly familiar to chest physicians, and the efficacy of corticosteroid treatment makes it appear at first sight as an easy problem to resolve, atypical clinical presentations, similarities with other diseases, severe forms, histological variants, side effects of therapy, and relapses can make the management more difficult than initially expected. This chapter will address the classical and less common features of organizing pneumonia, and will provide practical clues to the diagnosis and management of this disorder.

Republished: Fibrosing organising pneumonia

Organising pneumonia (otherwise referred to as bronchiolitis obliterans organising pneumonia) is characterised histologically by plugs of granulation tissue, which are present predominantly within small airways, alveolar ducts and peri-bronchiolar alveoli. This pattern is not specific for any disorder or cause, but is one type of inflammatory response to pulmonary injury, which may be seen in a wide variety of clinical conditions. Typically, organising pneumonia responds very well to corticosteroid treatment; however, a small percentage of patients appear to develop progressive fibrosis.

[Lymphatics in non-tumoral pulmonary diseases. Review]

Whereas lymphatics in pulmonary non-tumoral diseases have been less studied than blood microcirculation, they clearly play a significant role. This review is a short update on lymphatics in various non-tumoral pulmonary diseases, from asthma to interstitial pneumonitis, excluding lymphangioleiomyomatosis. A lymphatic remodelling has been evidenced in asthma as well as in acute or chronic (UIP as NSIP) interstitial lung diseases. Such a remodelling can be explained as a side effect of local changes in fluidics but could also be an active player in the fibrosing process. Moreover the association of juxta-alveloar lymphatics and granulomas provides new insights in the emergence of these lesions in pulmonary sarcoidosis.

Cryptogenic Organizing Pneumonia in Tomm5–/– Mice

Almost all mitochondrial proteins are encoded in the nuclear DNA and synthesized in the cytosol as pre-proteins. There is a protein translocase located in the mitochondrial outer membrane that transports mitochondrial pre-proteins into mitochondria. The central component of this translocase of the outer mitochondrial membrane (TOMM) complex is TOMM40, and TOMM5 is one of three small subunits associated with TOMM40. Translocase of outer mitochondrial membrane 5 homolog ( Tomm5–/–) knockout mice demonstrated an unexpected lung-specific phenotype characterized by widespread intra-alveolar fibrosis. Although TOMM5-deficient mice tested normal in a very broad range of phenotyping assays, they displayed histopathological lesions in the lung that were consistent with those reported in humans with cryptogenic organizing pneumonia (COP), which is also known as bronchiolitis obliterans organizing pneumonia (BOOP). The lesions had a patchy distribution in the lung and were characterized by the presence of intraluminal fibrogenic buds consisting of fibroblasts and myofibroblasts embedded in a loose connective tissue matrix that occupied the lumina of alveoli and alveolar ducts, with preservation of underlying alveolar architecture. In addition to macrophages, which were numerous in affected and surrounding alveoli, eosinophils comprised the most common and widespread inflammatory cell. Taken together, the findings in Tomm5–/– mice provide yet another example of the value of histopathology as a baseline assay in high-throughput phenotyping systems.

Bronchiolitis obliterans organizing pneumonia: pathogenesis, clinical features, imaging and therapy review

Bronchiolitis obliterans organizing pneumonia (BOOP) was first described in the early 1980s as a clinicopathologic syndrome characterized symptomatically by subacute or chronic respiratory illness and histopathologically by the presence of granulation tissue in the bronchiolar lumen, alveolar ducts and some alveoli, associated with a variable degree of interstitial and airspace infiltration by mononuclear cells and foamy macrophages. Persons of all ages can be affected. Dry cough and shortness of breath of 2 weeks to 2 months in duration usually characterizes BOOP. Symptoms persist despite antibiotic therapy. On imaging, air space consolidation can be indistinguishable from chronic eosinophilic pneumonia (CEP), interstitial pneumonitis (acute, nonspecific and usual interstitial pneumonitis, neoplasm, inflammation and infection). The definitive diagnosis is achieved by tissue biopsy. Patients with BOOP respond favorably to treatment with steroids.

The definition of fibrogenic processes in fibroblastic foci of idiopathic pulmonary fibrosis based on morphometric quantification of extracellular matrices

There is limited information regarding the process of tissue remodeling in fibroblastic foci associated with idiopathic pulmonary fibrosis. The aim of this study was to identify the different pathologic stages of tissue remodeling in fibroblastic foci based on the histopathologic differences in the glycosaminoglycan distribution and collagen deposition. In addition, we also aimed at clarifying the stage-specific characteristics by taking into consideration the expression pattern of matrix metalloproteinase and angiogenesis. Lung biopsies of 16 patients with idiopathic pulmonary fibrosis were used. The presence of glycosaminoglycans was detected by Alcian blue staining, and type I collagen was detected by immunohistochemical analysis with a primary antibody specific to the cross-linked carboxyterminal telopeptide of type I collagen. The fibroblastic foci characterized by the expression intensity of Alcian blue and telopeptide of type I collagen were divided into 3 groups, namely, Alcian blue(+)telopeptide of type I collagen(weak), Alcian blue(+)telopeptide of type I collagen(+), and Alcian blue(weak)telopeptide of type I collagen(+); consequently, 3 new stages were defined--stages I, II, and III, respectively. A significant inverse correlation was observed between the area densities of Alcian blue(+) and telopeptide of type I collagen(+) in fibroblastic foci. Stage I was characterized by the expression of matrix metalloproteinase-2 and tissue inhibitor of matrix metalloprotease-2 in fibroblasts and the overlying epithelium of fibroblastic foci, and also the absence of capillary angiogenesis. In contrast, the expression of these proteins was attenuated in stage III, except for that of matrix metalloproteinase-2 in fibroblasts. In stages II and III, capillary angiogenesis was observed. Lymphangiogenesis was undetected in all the 3 stages. Thus, pathologic staging helps understand the roles of the factors involved in tissue remodeling in idiopathic pulmonary fibrosis.

Characterization of lymphangiogenesis in various stages of idiopathic diffuse alveolar damage

In pulmonary fibrosis, an abnormal healing process, is believed to be involved in the damage to lung tissue. This process has not been correlated with lymphangiogenesis, which has garnered current interest in relation to wound healing. The aim of the present study was to clarify the characteristics of lymphangiogenesis in pulmonary fibrosis associated with idiopathic diffuse alveolar damage. Formalin-fixed and paraffin-embedded lung tissues from 13 autopsy cases with idiopathic diffuse alveolar damage were used. Antibodies specific to CD34 and D2-40 were used to detect blood vessels and lymphatics, respectively, and immunohistochemical examinations and morphometry analyses were performed. The standardized density of capillaries was increased significantly in the exudative stage of diffuse alveolar damage, whereas that of the lymphatics remained unchanged. In the proliferative stage, new lymphatics emerged, primarily in the intra-alveolar fibrotic lesions where capillaries were absent. In the fibrotic stage, in which the lung was shrunken, as revealed by the elevated density of pulmonary arteries, the standardized density of capillaries was reduced significantly. The standardized area density of the interstitium was elevated in the proliferative stage and subsequently reduced in the fibrotic stage. Three-dimensional reconstruction of images revealed that some new lymphatics lacked connection to existing lymphatics. During the progression of diffuse alveolar damage, lymphangiogenesis occurs independent of capillary angiogenesis.

Morphological and molecular markers in idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis is a progressive, lethal, interstitial lung disease with no proven effective therapy other than lung transplantation. A definitive diagnosis of the disease requires surgical lung biopsy to show a histological appearance of usual interstitial pneumonia. The main histological features include temporal and spatial heterogeneity, fibroblastic foci, extracellular matrix deposition with vessel remodeling and honeycomb changes. There are some morphological aspects that have recently been taken into account as possible prognostic markers for disease progression. Although the cellular and molecular pathways driving disease pathogenesis are complex and not fully delineated, increasing evidence suggests that a key event is ongoing alveolar epithelial injury in association with an abnormal host repair response. Inflammation seems to play a less important role and remains largely debated while increased attention has been on the role of noninflammatory structural cells, such as fibroblasts, epithelial cells and endothelial cells. The modifications and interactions among these cells are complex and regulated by various molecular factors. This article reviews the morphology of the disease, focusing on some new facets and on the principal molecular factors involved in the different aspects of parenchymal remodeling.

Organizing pneumonia and pulmonary lymphatic architecture in diffuse alveolar damage

Diffuse alveolar damage represents the pathologic basis of most cases of the acute respiratory distress syndrome. Diffuse alveolar damage reflects injury to the pulmonary alveolar wall and microvasculature, leading to the exudation of water and plasma proteins that can overwhelm the local lymphatic drainage. Organizing pneumonia is a prominent histopathologic feature in some cases of diffuse alveolar damage. We examined whether diffuse alveolar damage-organizing pneumonia and changes in lymphatic architecture might be indicators of clinical outcome in acute respiratory distress syndrome. Formalin-fixed lung sections (n = 26) from thoracoscopic lung biopsies of patients with diffuse alveolar damage in the fibroproliferative phase, with or without organizing pneumonia, were immunostained with anti-CD31 and anti-D240, markers of vascular and lymphatic endothelium, respectively, and examined by morphometric analysis. Positively staining vessels were enumerated and maximal luminal diameters recorded in randomly selected low-power fields. Patients with diffuse alveolar damage-organizing pneumonia showed greater survival than those with diffuse alveolar damage (67% versus 33%, P = .03). The maximal luminal diameter of D240+ lymphatic vessels was larger for diffuse alveolar damage-organizing pneumonia than diffuse alveolar damage (28 +/- 4 versus 59 +/- 16 microm, P = .02). In addition, larger lymphatic luminal diameters (28 +/- 4 versus 47 +/- 11 microm) were associated with increased survival (P = .12). We conclude that lung biopsy histopathology and pulmonary lymphatic morphology may predict survival in acute respiratory distress syndrome.

Angiogenesis in interstitial lung diseases: a pathogenetic hallmark or a bystander?

The past ten years parallels have been drawn between the biology of cancer and pulmonary fibrosis. The unremitting recruitment and maintenance of the altered fibroblast phenotype with generation and proliferation of immortal myofibroblasts is reminiscent with the transformation of cancer cells. A hallmark of tumorigenesis is the production of new blood vessels to facilitate tumor growth and mediate organ-specific metastases. On the other hand several chronic fibroproliferative disorders including fibrotic lung diseases are associated with aberrant angiogenesis. Angiogenesis, the process of new blood vessel formation is under strict regulation determined by a dual, yet opposing balance of angiogenic and angiostatic factors that promote or inhibit neovascularization, respectively. While numerous studies have examined so far the interplay between aberrant vascular and matrix remodeling the relative role of angiogenesis in the initiation and/or progression of the fibrotic cascade still remains elusive and controversial. The current article reviews data concerning the pathogenetic role of angiogenesis in the most prevalent and studied members of ILD disease-group such as IIPs and sarcoidosis, presents some of the future perspectives and formulates questions for potential further research.

Heterogeneous Increase in CD34-positive Alveolar Capillaries in Idiopathic Pulmonary Fibrosis

To elucidate the apparent contradictions in vascular remodeling in the lungs of patients with idiopathic pulmonary fibrosis, we evaluated alveolar vascularity in relation to the various degrees of fibrosis in surgically biopsied lungs of usual interstitial pneumonia. Alveolar capillary endothelial cells were intensely immunoreactive with CD34 but not with von Willebrand factor. Vascular density, that is, the relative ratio of capillary area to total area of alveolar walls, was significantly higher at low grades of fibrosis than in control lungs, whereas vascular density gradually decreased as the degree of fibrosis increased and was lower than that of control lungs in the most extensively fibrotic lesions. No vessels were observed inside fibroblastic foci. The potent angiogenic factors vascular endothelial growth factor and interleukin-8 were abundantly produced by capillary endothelial cells and alveolar epithelial cells in highly vascularized alveolar walls. In contrast, venules with CD34-negative but von Willebrand factor-positive endothelial cells localized in the center of the fibrotic lesions were slightly increased and identified as postcapillary venules by three-dimensional reconstructed images. These results indicate the presence of heterogeneous vascular remodeling in usual interstitial pneumonia.

Mechanisms of pulmonary fibrosis

Tissue injury evokes highly conserved, tightly regulated inflammatory responses and less well-understood host repair responses. Both inflammation and repair involve the recruitment, activation, apoptosis, and eventual clearance of key effector cells. In this review, we propose the concept of pulmonary fibrosis as a dysregulated repair process that is perpetually "turned on" even though classical inflammatory pathways may be dampened or "switched off." Significant regional heterogeneity, with varied histopathological patterns of inflammation and fibrosis, has been observed in individual patients with idiopathic pulmonary fibrosis. We discuss environmental factors and host response factors, such as genetic susceptibility and age, that may influence these varied manifestations. Better understanding of the mechanisms of lung repair, which include alveolar reepithelialization, myofibroblast differentiation/activation, and apoptosis, should offer more effective therapeutic options for progressive pulmonary fibrosis.

Pigment epithelium-derived factor in idiopathic pulmonary fibrosis: a role in aberrant angiogenesis

Pigment epithelium-derived factor (PEDF) is a 50-kD protein with angiostatic and neurotrophic activities that regulates vascular development within the eye. PEDF expression was increased in the lungs of patients with idiopathic pulmonary fibrosis (IPF) based on microarray analyses. Angiogenesis has been implicated in the pathogenesis of fibrotic lung diseases, we therefore hypothesized that regional abnormalities in vascularization occur in IPF as a result of an imbalance between PEDF and vascular endothelial growth factor. We demonstrated that vascular density is regionally decreased in IPF within the fibroblastic foci, and that within these areas PEDF was increased, whereas vascular endothelial growth factor was decreased. PEDF colocalized with the fibrogenic cytokine, transforming growth factor (TGF)-beta 1, particularly within the fibrotic interstitium and the fibroblastic focus, and prominently within the epithelium directly overlying the fibroblastic focus. This suggested that TGF-beta 1 might regulate PEDF expression. Using 3T3-L1 fibroblasts and human lung fibroblasts, we showed that PEDF was indeed a TGF-beta 1 target gene. Collectively, our findings implicate PEDF as a regulator of pulmonary angiogenesis and an important mediator in IPF.

Laminin-5 γ2Chain in Cryptogenic Organizing Pneumonia and Idiopathic Pulmonary Fibrosis

Insufficient reepithelialization of injured alveolar walls may be important in the pathogenesis of idiopathic pulmonary fibrosis (IPF). Laminin-5 is expressed in epithelial cells of healing wounds, promoting cell attachment and migration. In this study we have studied the extent of reepithelialization of newly formed intraluminal connective tissue, the immunohistochemical expression and ultrastructural localization of the laminin-5 gamma2 chain protein, and the synthesis of the laminin-5 gamma2 chain mRNA in regenerating epithelial cells in cryptogenic organizing pneumonia (COP) and IPF. The results show that the mean extent of reepithelialization of intraluminal connective tissue lesions was 76% (SD, +/- 27%) in COP, and 54% (SD, +/- 23%) in IPF (p < 0.025). The laminin-5 gamma2 chain was synthesized and widely expressed in regenerating epithelial cells in both diseases. Immunohistochemistry for surfactant-associated protein A suggests a pneumocyte origin for the regenerating epithelial cells in IPF. It is concluded that both in COP and IPF, regenerating epithelial cells are capable of synthesizing the laminin-5 gamma2 chain needed for adhesive connections to the underlying basement membrane. However, in IPF, the reepithelialization seems to be disturbed or delayed.

Interstitial vascularity in fibrosing alveolitis

The aim of this study was to evaluate interstitial vascularity in cryptogenic fibrosing alveolitis (CFA) and in fibrosing alveolitis associated with systemic sclerosis (FASSc). Open lung biopsies from eight patients with CFA, nine patients with FASSc, and normal lung from 12 patients undergoing surgery for lung cancer were studied. Markers for endothelial cells (CD34) and cell proliferation (proliferating cell nuclear antigen) were localized by sequential immunohistochemistry and quantified using computer-assisted analysis. Vascular distribution was evaluated at increasing distances (up to 160 microm) from the airspaces. Vessel density was markedly reduced in both FASSc (3.9%) and in CFA (4.5%) compared with control samples (20.4%, p < 0.0001). The percentage of tissue occupied by vessels decreased with increasing distance from alveoli in control samples but not in CFA or FASSc samples. Endothelial cell proliferation indices were increased in FASSc but not in CFA, compared with control samples (p = 0.006). In conclusion, there is net vascular ablation and redistribution of blood vessels in areas of interstitial thickening in both CFA and FASSc, which may contribute to gas exchange impairment.

VEGF and bFGF are highly expressed in intraluminal fibromyxoid lesions in bronchiolitis obliterans organizing pneumonia

Bronchiolitis obliterans organizing pneumonia (BOOP) and usual interstitial pneumonia (UIP) are fibrous pulmonary disorders in which new fibromyxoid connective tissue is formed in distal air spaces. In BOOP this tissue is susceptible to even complete reversal, but in UIP it participates in the remodelling of the interstitium. Our previous study showed that in BOOP this newly formed intraluminal tissue is more capillarized than in UIP. This paper studies the immunohistochemical expression of vascular endothelial growth factor (VEGF) and its receptors Flt-1 and Flk-1, and basic fibroblast growth factor (bFGF) in BOOP and UIP. It was hypothesized that there would be a difference in the expression of these angiogenic growth factors paralleling the difference in their capillarization. The results show that both VEGF and bFGF are widely expressed in BOOP and in UIP. It was shown with two different VEGF antibodies that its expression was more pronounced in the intraluminal fibromyxoid lesions in BOOP than in UIP (p<0.001 and 0.004, respectively). Similarly, bFGF also showed stronger espression in BOOP than in UIP (p<0.02) in these areas. The expression of Flt-1 and Flk-1 was in agreement with the expression of VEGF. It is concluded that the growth factors VEGF and bFGF may have an important role in the pathogenesis of BOOP and UIP; furthermore, their expression correlates with the angiogenic activity of the newly formed intraluminal fibromyxoid connective tissue in BOOP. Angiogenesis mediated by these growth factors may be one reason for the reversal of intraluminal fibromyxoid connective tissue in BOOP and for its good clinical outcome.

Angiogenesis in the pathogenesis of inflammatory joint and lung diseases

This paper reviews hypotheses about roles of angiogenesis in the pathogenesis of inflammatory disease in two organs, the synovial joint and the lung. Neovascularisation is a fundamental process for growth and tissue repair after injury. Nevertheless, it may contribute to a variety of chronic inflammatory diseases, including rheumatoid arthritis, osteoarthritis, asthma, and pulmonary fibrosis. Inflammation can promote angiogenesis, and new vessels may enhance tissue inflammation. Angiogenesis in inflammatory disease may also contribute to tissue growth, disordered tissue perfusion, abnormal ossification, and enhanced responses to normal or pathological stimuli. Angiogenesis inhibitors may reduce inflammation and may also help to restore appropriate tissue structure and function.