Heterogeneity of collagen synthesis in normal and systemic sclerosis skin fibroblasts. Increased proportion of high collagen-producing cells in systemic sclerosis fibroblasts

Objective. The goal of this study was to quantitatively analyze the distribution of collagen synthesis in normal and systemic sclerosis (SSc) fibroblast populations in order to determine the extent of activation in SSc populations. Methods. We used quantitative in situ hybridization to assess the population distribution of type I collagen synthesis. Fibroblast cultures were derived from both clinically involved and uninvolved skin regions of patients with SSc, and from healthy adults, and assessed for levels of α1(I) procollagen messenger RNA (mRNA). Results. Dermal fibroblasts from both patients with SSc and normal adults were heterogeneous for distribution of α1(I) procollagen mRNA when assessed by in situ hybridization, with a wide range of grains per cell. In contrast, clones of neonatal fibroblasts showed a relatively homogeneous distribution of grain counts. Involved SSc skin fibroblasts had a larger proportion of cells in the high collagen-producing mRNA subpopulation (mean ± SEM 28.4 ± 6.85%), compared with normal fibroblasts (1.75 ± 1.44%) and uninvolved fibroblasts (9.6 ± 6.73%). Conversely, within the low collagen-producing mRNA subpopulation, involved fibroblasts had a smaller proportion of cells (mean ± SEM 14.0 ± 5.63%) than did uninvolved fibroblasts (37.8 ± 13.69%), while normal fibroblasts had a majority of the cells in this subpopulation (53.5 ± 8.68%). Conclusion. These results suggest that only a specific subset of fibroblasts are activated in SSc, as evidenced by an increased proportion of cells with high levels of α1(I) procollagen mRNA. Differences between the SSc and normal fibroblast populations appeared to be quantitative rather than qualitative. This may be a result of either clonal selection or selective activation in the pathogenesis of SSc.     

Impaired collagen gel contraction with cultured skin fibroblasts from patients with systemic sclerosis

We investigated the capacity of skin fibroblasts, derived from 9 patients with systemic sclerosis (SSc), to contract collagen lattices in a three-dimensional culture system. In comparison with control fibroblasts (N = 8), more than 30% of SSc fibroblasts exhibited markedly impaired ability to contract collagen lattices. The expression of alpha2beta1 integrins and integrin-mediated signals were not significantly different between normal and SSc fibroblasts. Although the underlying mechanisms remain to be determined, our present data provide evidence that certain aspects of interaction with collagen are impaired in SSc fibroblasts.     

Mutant fibronectin gene in skin fibroblasts of sclerotic lesions from patients with progressive systemic sclerosis

A mutant fibronectin gene was identified in skin fibroblasts obtained from sclerotic lesions of 7 patients with progressive systemic sclerosis. We found 2 point mutations adjacent to the cell-attachment tetrapeptide DNA sequence in the cell-binding domain of the fibronectin gene. This observation suggests that the mutant fibronectin is related to an integral component of sclerotic pathogenesis through abnormal cellular interactions.     

Antifibroblast antibodies from systemic sclerosis patients are internalized by fibroblasts via a caveolin-linked pathway

OBJECTIVE: Fibroblast activation is a crucial event in the development of systemic sclerosis (SSc). Antifibroblast autoantibodies (AFAs), detectable in the sera of SSc patients, are able to induce a proinflammatory phenotype on cultured fibroblasts. This study was undertaken to investigate the mechanisms of the interaction between AFAs and living fibroblasts. METHODS: We coupled to fluorescein 1) IgG purified from AFA-positive and AFA-negative SSc sera (as assessed by cellular enzyme-linked immunosorbent assay) and 2) single healthy donor and pooled normal IgG. The interaction of IgG with living cultured fibroblasts from healthy individuals and from a patient with SSc was visualized by real-time confocal microscopy. Intracellular colocalization of caveolin and internalized AFA-positive IgG was assessed by immunofluorescence. RESULTS: AFA-positive IgG bound to living fibroblasts and was internalized with a cytoplasmic fibrillar pattern, in contrast to AFA-negative IgG. In the IgG tested, no correlation with antinuclear antibody activity was found. Preincubation of fibroblasts with normal IgG did not affect internalization. Internalized AFA-positive IgG colocalized with caveolin, and internalization was entirely inhibited by disassembling fibroblast caveolae with filipin. CONCLUSION: The finding that both normal and pathologic fibroblasts specifically internalized AFA-positive, but not AFA-negative, IgG demonstrates that AFAs in SSc patient sera interact with constitutively expressed membrane molecules on fibroblasts, via an Fc-independent mechanism. The results of colocalization and inhibition experiments suggest that microdomains containing caveolin are involved in the interaction between AFAs and fibroblasts. These data, together with the reported ability of AFAs to activate fibroblasts, provide evidence for a role of AFAs in the pathogenesis of SSc.     

Microalbuminuria in systemic sclerosis.

A prospective study was performed to determine urinary albumin excretion in a group of 28 patients with systemic sclerosis. At the initial screen one patient had proteinuria and three had microalbuminuria. One year later these abnormalities persisted and in two of of the patients serum creatinine had significantly increased. In addition, a further three patients had developed microalbuminuria. In a control group of 10 patients with primary Raynaud's disease none had microalbuminuria. In a second control group of 16 patients with unrelated skin diseases one patient had microalbuminuria and one proteinuria, but both these patients had a history of hypertension. It is concluded that microalbuminuria is more common in patients with systemic sclerosis than in patients of equivalent age with other dermatological conditions but no vascular disease.     

Decreased susceptibility to Fas-induced apoptosis of systemic sclerosis dermal fibroblasts

OBJECTIVE: To determine whether dysregulated apoptosis of systemic sclerosis (SSc) fibroblasts contributes to progressive fibrosis by promoting fibroblast longevity. METHODS: We examined the pattern of fibroblast proliferation and apoptosis in SSc skin lesions and the susceptibility of cultured SSc dermal fibroblasts to apoptosis. Skin biopsy samples from SSc patients and control subjects were used to establish fibroblast cultures and were examined histologically. In skin sections, apoptosis was examined by TUNEL, and proliferation by immunostaining for proliferating cell nuclear antigen. Susceptibility of fibroblasts to apoptosis induced in vitro by different stimuli was studied by TUNEL. Expression of Bcl-2, Bcl-x, and Bax proteins in cultured fibroblasts was studied by Western blotting. RESULTS: Proliferation of dermal fibroblasts was not observed in normal skin but was present in skin from patients with SSc and other inflammatory skin diseases. Apoptosis of fibroblasts in SSc fibrotic skin lesions was not observed. In vitro, SSc fibroblasts were specifically resistant to apoptosis induced by Fas receptor stimulation but had normal susceptibility to apoptosis induced by nonspecific stimuli (protein kinase inhibition or serum withdrawal). Decreased susceptibility to Fas stimulation was not caused by decreased levels of surface Fas receptor. In SSc fibroblasts, quiescence induced by confluence and serum starvation was followed by an abnormal down-regulation of proapoptotic Bax protein. Up-regulation of the Bax:Bcl-2 ratio in SSc fibroblasts by Bcl-2 antisense oligonucleotides restored their susceptibility to Fas-mediated apoptosis. CONCLUSION: Our findings suggest that abnormal apoptotic regulation in fibroblasts can contribute to the pathogenesis of progressive fibrosis in SSc. Modulation of Bcl-2-related proteins appears to be a potential target for the development of apoptosis-based antifibrotic strategies.     

Regressive systemic sclerosis.

Systemic sclerosis is a disease which usually progresses or reaches a plateau with persistence of symptoms and signs. Regression is extremely unusual. Four cases of established scleroderma are described in which regression is well documented. The significance of this observation and possible mechanisms of disease regression are discussed.     

Antireticulin antibody in systemic sclerosis.

The prevalence, immunoglobulin class, and IgG subclass of antireticulin antibody in the serum samples of 32 patients with systemic sclerosis were investigated by indirect immunofluorescence on unfixed rodent tissue. Antireticulin antibody was present in 22/32 (69%) of patients and belonged to the IgG class in 19/22 (86%), the IgA class in 13/22 (59%), and the IgM class in 6/22 (27%) of positive sera. IgG1 was the predominant subclass of IgG antireticulin antibody, occurring either alone or in association with IgG3 in 12/19 cases (63%). Thus antireticulin antibody of the IgG and IgA classes is found in most patients with systemic sclerosis. The finding of an autoantibody with reactivity for collagen-like fibres in systemic sclerosis indicates that the antibody has a potential role in the pathogenesis of the disease, and as it belongs to the IgA class this suggests that it arises in response to antigens presented to the immune system at the mucosal level.     

Cardiac involvement in systemic sclerosis.

OBJECTIVE. To assess the incidence and extent of cardiac involvement in systemic sclerosis (SSc) patients with no apparent cardiac symptoms. METHODS. Surface electrocardiography, ambulatory electrocardiography, radionuclide ventriculography, myocardial scintigraphy, and echocardiography were performed in 18 patients. RESULTS. These studies demonstrated ventricular tachycardia in 1 patient, nonsustained ventricular tachycardia in 5, supraventricular tachycardia in 6, decreased left ventricular ejection fraction in 2, decreased right ventricular ejection fraction in 8, and stress-induced reversible myocardial perfusion abnormalities in 6. CONCLUSION. These observations demonstrate a high rate of cardiac abnormalities in SSc patients without cardiac symptoms.     

Serologic abnormalities in systemic sclerosis.

Recent evidence has confirmed that sera from most systemic sclerosis (SSc) patients contain one of three mutually exclusive, SSc-associated autoantibodies (anti-RNA polymerase III, anti-topoisomerase I, or anti-centromere antibodies). Each is associated with the presence of particular clinical features and certain human lymphocyte antigen (HLA) alleles. Based on the available data the most likely model is for the existence of three distinct disease processes, each with certain key pathologic features. In turn, each pathologic state is responsible for characteristic symptoms, and leads to the production of a distinctive set of modified autoantigens. Certain cryptic epitopes are consequently produced by antigen-presenting cells, and are effectively presented according to the available HLA molecules, with subsequent HLA-restricted autoantibody production. Thus, while not directly involved in disease pathogenesis, SSc-associated autoantibodies appear to be reliable reporters of disease-specific pathologic phenomena, and may prove valuable pointers toward the etiopathogenesis of the different subtypes of SSc.     

Pharyngo-oesophageal dysphagia in systemic sclerosis.

A patient with systemic sclerosis developed recurrent dysphagia consistently localised to the pharyngo-oesophageal region. This was due to narrowing of the lumen as a result of gross thickening of the pharyngo-oesophageal muscles. Histologically the changes were typical of systemic sclerosis. The lower oesophagus was less involved. Eventually she died of aspiration pneumonia and respiratory arrest.