Identification of collagen fibrils in scleroderma skin

Collagen constitutes about 12% in females and 17% in males of the total protein in mice

Collagen has been postulated to be the most abundant protein in our body, making up one-third of the total protein content in mammals. However, a direct assessment of the total collagen levels of an entire mammal to confirm this estimate is missing. Here we measured hydroxyproline levels as a proxy for collagen content together with total protein levels of entire mice or of individual tissues. Collagen content normalized to the total protein is approximately 0.1% in the brain and liver, 1% in the heart and kidney, 4% in the muscle and lung, 6% in the colon, 20-40% in the skin, 25-35% in bones, and 40-50% in tendons of wild-type (CD1 and CB57BL/6) mice, consistent with previous reports. To our surprise, we find that collagen is approximately 12% in females and 17% in males of the total protein content of entire wild-type (CD1 and CB57BL/6) mice. Although collagen type I is the most abundant collagen, the most abundant proteins are albumin, hemoglobulin, histones, actin, serpina, and then collagen type I. Analyzing amino acid compositions of mice revealed glycine as the most abundant amino acid. Thus, we provide reference points for collagen, matrisome, protein, and amino acid composition of healthy wild-type mice.

Adipose-Derived Stem Cells Attenuate Skin Fibrosis and Improve Fat Retention of a Localized Scleroderma Mouse Model

BACKGROUND

Although autologous fat grafting is a feasible surgical technique to improve facial deformity in patients with localized scleroderma, its success is limited by the low graft retention induced by the local inflammatory environment. This study investigated the potential effect of adipose-derived stem cells (ASCs) on skin fibrosis and fat retention in a localized scleroderma mouse model.

METHODS

BALB/C nude mice that were induced by bleomycin to establish a localized scleroderma model were divided randomly into five groups: blank control; fat grafting; and low, moderate, and high doses of ASC-assisted fat grafting. The backs of the mice were subcutaneously injected with phosphate-buffered saline or fat, or fat with low, moderate, and high doses of ASCs (1 × 10 5 /mL, 5 × 10 5 /mL, and 25 × 10 5 /mL, respectively). The skin fibrosis and fat retention were analyzed after 1 month or 3 months, respectively.

RESULTS

Compared to the disease model group, the fat-grafting group, and the low- and moderate-dose ASC-enriched groups, the high-dose ASCs significantly attenuated skin fibrosis, inhibited the production of type III collagen and transforming growth factor-β1, increased fat graft retention, enhanced the expression of angiogenesis-related cytokines and angiogenesis, and increased the expression of adipogenesis-related cytokines.

CONCLUSIONS

The results demonstrated that high-dose ASCs attenuated skin fibrosis and improved fat retention in a localized scleroderma model by reducing inflammation and by promoting angiogenesis and adipogenesis. The authors further demonstrated that ASCs enhanced adipogenesis through the AKT/ERK signaling pathway.

CLINICAL RELEVANCE STATEMENT

Fat grafting has been used to treat localized scleroderma patients but with low fat retention. In this study, ASC attenuated skin fibrosis and improved fat retention in the localized scleroderma model, providing evidence for cell therapy in future application of localized scleroderma treatment.

Oxidative stress-induced senescence mediates inflammatory and fibrotic phenotypes in fibroblasts from systemic sclerosis patients

OBJECTIVE

Systemic sclerosis (SSc) is an autoimmune connective tissue disorder characterized by inflammation and fibrosis. Although constitutive activation of fibroblasts is proposed to be responsible for the fibrotic and inflammatory features of the disease, the underlying mechanism remains elusive and, effective therapeutic targets are still lacking. The aim of this study was to evaluate the role of oxidative stress-induced senescence and its contribution to the pro-fibrotic and pro-inflammatory phenotypes of fibroblasts from SSc patients.

METHODS

Dermal fibroblasts were isolated from SSc (n = 13) and healthy (n = 10) donors. Fibroblast's intracellular and mitochondrial reactive oxygen species were determined by flow cytometry. Mitochondrial function measured by Seahorse XF24 analyzer. Fibrotic and inflammatory gene expressions were assessed by qPCR and key pro-inflammatory components of the fibroblasts' secretome (interleukin (IL) 6 and IL8) were quantified by ELISA.

RESULTS

Compared to healthy fibroblasts, SSc fibroblasts displayed higher levels of both intracellular and mitochondrial ROS. Oxidative stress in SSc fibroblasts induced the expression of fibrotic genes and activated the transforming growth factor-β-activated kinase 1 (TAK1) -IκB kinase β (IKKβ)- interferon regulatory factor 5 (IRF5) inflammatory signaling cascade. These cellular responses paralleled the presence of a DNA damage response, a senescence-associated secretory phenotype and a fibrotic response. Treatment of SSc fibroblasts with ROS scavengers reduced their pro-inflammatory secretome production and fibrotic gene expression.

CONCLUSIONS

Oxidative stress-induced cellular senescence in SSc fibroblasts underlies their pro-inflammatory and pro-fibrotic phenotypes. Targeting redox imbalance of SSc fibroblasts enhances their in vitro functions and could be of relevance for SSc therapy.

Protective effects of halophyte complex extract against UVB-induced damage in human keratinocytes and the skin of hairless mice

Limonium tetragonum, Triglochin maritimum, Artemisia scoparia and red ginseng have been used as folk remedies for treating a variety of diseases. In the current study, the protective effects of halophyte and red ginseng against ultraviolet (UV)-induced skin damage were investigated. Halophyte red ginseng complex extract (HRCE) was prepared and its effects on UV-B irradiated human keratinocytes and mouse skin were studied through ELISA, Western blotting immunofluorescence and histological staining. HRCE inhibited peroxide-induced damage in human keratinocytes. HRCE also inhibited UVB-induced collagen and elastin degradation in human keratinocytes and mouse skin. In addition, HRCE inhibited mast cell infiltration in the skin of mice irradiated with UVB light. This effect was likely due to HRCE inhibiting the activation of MAPK and NF-κB. By protecting the skin from UVB-induced skin damage, HRCE has the potential to be used in the treatment and prevention of UV-induced skin damage and photoaging.

TGFβ-1 Induced Cross-Linking of the Extracellular Matrix of Primary Human Dermal Fibroblasts

Excessive cross-linking is a major factor in the resistance to the remodelling of the extracellular matrix (ECM) during fibrotic progression. The role of TGFβ signalling in impairing ECM remodelling has been demonstrated in various fibrotic models. We hypothesised that increased ECM cross-linking by TGFβ contributes to skin fibrosis in Systemic Sclerosis (SSc). Proteomics was used to identify cross-linking enzymes in the ECM of primary human dermal fibroblasts, and to compare their levels following treatment with TGFβ-1. A significant upregulation and enrichment of lysyl-oxidase-like 1, 2 and 4 and transglutaminase 2 were found. Western blotting confirmed the upregulation of lysyl hydroxylase 2 in the ECM. Increased transglutaminase activity in TGFβ-1 treated ECM was revealed from a cell-based assay. We employed a mass spectrometry-based method to identify alterations in the ECM cross-linking pattern caused by TGFβ-1. Cross-linking sites were identified in collagens I and V, fibrinogen and fibronectin. One cross-linking site in fibrinogen alpha was found only in TGFβ-treated samples. In conclusion, we have mapped novel cross-links between ECM proteins and demonstrated that activation of TGFβ signalling in cultured dermal fibroblasts upregulates multiple cross-linking enzymes in the ECM.

Fat Grafting for the Treatment of Scleroderma

BACKGROUND

Scleroderma is a chronic connective tissue disease that results in fibrosis of the skin and internal organs. Although internal organ involvement corresponds with poor prognosis, systemic agents are effective at improving the effects of scleroderma on internal organs. In contrast, skin manifestations are universally present in all patients diagnosed with scleroderma, yet no systemic agents have been shown to be successful. Fat grafting has been shown to improve skin quality and improve contour irregularities and may be helpful in the treatment of patients with scleroderma.

METHODS

The authors performed a thorough review of the pathophysiology of scleroderma and the current treatment options for scleroderma. The efficacy of fat grafting for the treatment of scleroderma and the mechanism by which fat grafting improves outcomes was also discussed.

RESULTS

Scleroderma is characterized by chronic inflammation and vascular compromise that leads to fibrosis of the skin and internal organs. Fat grafting has recently been the focus of significant basic science research. It has been shown to reduce inflammation, reduce fibrosis by limiting extracellular matrix proteins and increasing collagenase activity, and provide structural support through stem cell proliferation and differentiation. The adipocytes, adipose stem cells, endothelial cells, and vascular smooth muscle cells in the processed fat likely contribute to the effectiveness of this treatment.

CONCLUSIONS

Fat grafting in scleroderma patients likely improves skin manifestations by recreating fullness, correcting contour deformities, and improving skin quality. The injected fat provides a mixture of cells that influences the recipient site, resulting in improved outcomes.

Identification of regulators of the myofibroblast phenotype of primary dermal fibroblasts from early diffuse systemic sclerosis patients

Systemic sclerosis (SSc or scleroderma) is an auto-immune disease characterized by skin fibrosis. While primary cells from patients are considered as a unique resource to better understand human disease biology, the effect of in vitro culture on these cells and their evaluation as a platform to identify disease regulators remain poorly characterized. The goal of our studies was to provide insights into the utility of SSc dermal fibroblast primary cells for therapeutic target discovery. The disease phenotypes of freshly isolated and in vitro cultured SSc dermal fibroblasts were characterized using whole transcriptome profiling, alpha smooth muscle actin (ASMA) expression and cell impedance. SSc dermal fibroblasts retained most of the molecular disease phenotype upon in vitro culture for at least four cell culture passages (approximatively 10 cell doublings). We validated an RNA interference high throughput assay that successfully identified genes affecting the myofibroblast phenotype of SSc skin fibroblasts. These genes included MKL1, RHOA and LOXL2 that were previously proposed as therapeutic anti-fibrotic target, and ITGA5, that has been less studied in fibrosis biology and may be a novel potential modifier of SSc fibroblast biology. Together our results demonstrated the value of carefully-phenotyped SSc dermal fibroblasts as a platform for SSc target and drug discovery.

New developments on skin fibrosis - Essential signals emanating from the extracellular matrix for the control of myofibroblasts

Many different diseases are associated with fibrosis of the skin. The clinical symptoms can vary considerably with a broad range from isolated small areas to the involvement of the entire integument. Fibrosis is triggered by a multitude of different stimuli leading to activation of the immune and vascular system that then initiate fibroblast activation and formation of matrix depositing and remodeling myofibroblasts. Ultimately, myofibroblasts deposit excessive amounts of extracellular matrix with a pathological architecture and alterations in growth factor binding and biomechanical properties, which culminates in skin hardening and loss of mobility. Treatment depends certainly on the specific type and cause of the disease, for the autoimmune driven localized and systemic scleroderma therapeutic options are still limited, but recent research has pointed out diverse molecular targets and mechanisms that can be exploited for the development of novel antifibrotic therapy.

What can we learn from Fli1-deficient mice, new animal models of systemic sclerosis?

Systemic sclerosis is a complex multifactorial disease characterized by autoimmunity, vasculopathy, and selective organ fibrosis. A series of genetic and epidemiological studies have demonstrated that environmental influences play a central role in the onset of systemic sclerosis, while genetic factors determine the susceptibility to and the severity of this disease. Therefore, the identification of predisposing factors related to environmental influences would provide us with an informative clue to better understand the pathological process of this disease. Based on this concept, the deficiency of transcription factor Friend leukemia virus integration 1, which is epigenetically suppressed in systemic sclerosis, seems to be a potential candidate acting as the predisposing factor of this disease. Indeed, Fli1-mutated mice serve as a set of useful disease models to disclose the complex pathology of systemic sclerosis. This article overviews the recent advancement in systemic sclerosis animal models associated with Friend leukemia virus integration 1 deficiency.

Nrf2 exerts cell-autonomous antifibrotic effects: compromised function in systemic sclerosis and therapeutic rescue with a novel heterocyclic chalcone derivative

The transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2) governs antioxidant, innate immune and cytoprotective responses and its deregulation is prominent in chronic inflammatory conditions. To examine the hypothesis that Nrf2 might be implicated in systemic sclerosis (SSc), we investigated its expression, activity, and mechanism of action in SSc patient samples and mouse models of fibrosis and evaluated the effects of a novel pharmacologic Nrf2 agonist. We found that both expression and activity of Nrf2 were significantly reduced in SSc patient skin biopsies and showed negative correlation with inflammatory gene expression. In skin fibroblasts, Nrf2 mitigated fibrotic responses by blocking canonical transforming growth factor-β (TGF-β)-Smad signaling, whereas silencing Nrf2 resulted in constitutively elevated collagen synthesis, spontaneous myofibroblast differentiation, and enhanced TGF-ß responses. Bleomycin treatment of Nrf2-null mice resulted in exaggerated fibrosis. In wild-type mice, treatment with a novel pharmacologic Nrf2 agonist 2-trifluoromethyl-2'-methoxychalcone prevented dermal fibrosis induced by TGF-β. These findings are the first to identify Nrf2 as a cell-intrinsic antifibrotic factor with key roles in maintaining extracellular matrix homeostasis and a pathogenic role in SSc. Pharmacologic reactivation of Nrf2, therefore, represents a novel therapeutic strategy toward effective treatment of fibrosis in SSc.

Epithelial Fli1 deficiency drives systemic autoimmunity and fibrosis: Possible roles in scleroderma

Systemic sclerosis (SSc), or scleroderma, is a multisystem autoimmune disorder characterized by vasculopathy and fibrosis in the skin and internal organs, most frequently in the esophagus and lungs. Hitherto, studies on SSc pathogenesis centered on immune cells, vascular cells, and fibroblasts. Although dysregulated keratinocytes in SSc have been recently reported, the contribution of epithelial cells to pathogenesis remains unexplored. In this study, we demonstrated the induction of SSc-like molecular phenotype in keratinocytes by gene silencing of transcription factor Friend leukemia virus integration 1 (Fli1), the deficiency of which is implicated in SSc pathogenesis. Keratin 14-expressing epithelial cell-specific Fli1 knockout mice spontaneously developed dermal and esophageal fibrosis with epithelial activation. Furthermore, they developed remarkable autoimmunity with interstitial lung disease derived from thymic defects with down-regulation of autoimmune regulator (Aire). Importantly, Fli1 directly regulated Aire expression in epithelial cells. Collectively, epithelial Fli1 deficiency might be involved in the systemic autoimmunity and selective organ fibrosis in SSc. This study uncovers unidentified roles of dysregulated epithelial cells in SSc pathogenesis.

Fibroblast-Derived MMP-14 Regulates Collagen Homeostasis in Adult Skin

Proteolytic activities in the extracellular matrix by the matrix metalloproteinase (MMP)-14 have been implicated in the remodeling of collagenous proteins during development. To analyze the function of fibroblast-derived MMP-14 in adult skin homeostasis, we generated mice with inducible deletion of MMP-14 in the dermal fibroblast (MMP-14^Sf–/–). These mice are smaller and display a fibrosis-like phenotype in the skin. The skin of these mice showed increased stiffness and tensile strength but no altered collagen cross-links. In vivo, we measured a significantly increased amount of collagen type I accumulated in the skin of MMP-14^Sf–/– mice without an increase in collagen fibril diameters. However, bleomycin-induced fibrosis in skin proceeded in a comparable manner in MMP-14^Sf+/+ and MMP-14^Sf–/– mice, but resolution over time was impaired in MMP-14^Sf–/– mice. Increased accumulation of collagen type I was detected in MMP-14^Sf–/– fibroblasts in culture without significant enhancement of collagen de novo synthesis. This points to a degradative but not synthetic phenotype. In support of this, MMP-14^Sf–/– fibroblasts lost their ability to process fibrillar collagen type I and to activate proMMP-2. Taken together, these data indicate that MMP-14 expression in fibroblasts plays a crucial role in collagen remodeling in adult skin and largely contributes to dermal homeostasis underlying its pathogenic role in fibrotic skin disease.

Gastrointestinal Manifestations, Malnutrition, and Role of Enteral and Parenteral Nutrition in Patients With Scleroderma

Scleroderma (systemic sclerosis) is an autoimmune disease that can affect multiple organ systems. Gastrointestinal (GI) involvement is the most common organ system involved in scleroderma. Complications of GI involvement including gastroesophageal reflux disease, small intestinal bacterial overgrowth, and chronic intestinal pseudoobstruction secondary to extensive fibrosis may lead to nutritional deficiencies in these patients. Here, we discuss pathophysiology, progression of GI manifestations, and malnutrition secondary to scleroderma, and the use of enteral and parenteral nutrition to reverse severe nutritional deficiencies. Increased mortality in patients with concurrent malnutrition in systemic sclerosis, as well as the refractory nature of this malnutrition to pharmacologic therapies compels clinicians to provide novel and more invasive interventions in reversing these nutritional deficiencies. Enteral and parenteral nutrition have important implications for patients who are severely malnourished or have compromised GI function as they are relatively safe and have substantial retrospective evidence of success. Increased awareness of these therapeutic options is important when treating scleroderma-associated malnutrition.

A Role of Myocardin Related Transcription Factor-A (MRTF-A) in Scleroderma Related Fibrosis

In scleroderma (systemic sclerosis, SSc), persistent activation of myofibroblast leads to severe skin and organ fibrosis resistant to therapy. Increased mechanical stiffness in the involved fibrotic tissues is a hallmark clinical feature and a cause of disabling symptoms. Myocardin Related Transcription Factor-A (MRTF-A) is a transcriptional co-activator that is sequestered in the cytoplasm and translocates to the nucleus under mechanical stress or growth factor stimulation. Our objective was to determine if MRTF-A is activated in the disease microenvironment to produce more extracellular matrix in progressive SSc. Immunohistochemistry studies demonstrate that nuclear translocation of MRTF-A in scleroderma tissues occurs in keratinocytes, endothelial cells, infiltrating inflammatory cells, and dermal fibroblasts, consistent with enhanced signaling in multiple cell lineages exposed to the stiff extracellular matrix. Inhibition of MRTF-A nuclear translocation or knockdown of MRTF-A synthesis abolishes the SSc myofibroblast enhanced basal contractility and synthesis of type I collagen and inhibits the matricellular profibrotic protein, connective tissue growth factor (CCN2/CTGF). In MRTF-A null mice, basal skin and lung stiffness was abnormally reduced and associated with altered fibrillar collagen. MRTF-A has a role in SSc fibrosis acting as a central regulator linking mechanical cues to adverse remodeling of the extracellular matrix.

Simultaneous downregulation of KLF5 and Fli1 is a key feature underlying systemic sclerosis

Systemic sclerosis (SSc) is manifested by fibrosis, vasculopathy and immune dysregulation. So far, a unifying hypothesis underpinning these pathological events remains unknown. Given that SSc is a multifactorial disease caused by both genetic and environmental factors, we focus on the two transcription factors, which modulate the fibrotic reaction and are epigenetically suppressed in SSc dermal fibroblasts, Friend leukemia integration 1 (Fli1) and Krüppel-like factor 5 (KLF5). In addition to Fli1 silencing-dependent collagen induction, simultaneous knockdown of Fli1 and KLF5 synergistically enhances expression of connective tissue growth factor. Notably, mice with double heterozygous deficiency of Klf5 and Fli1 mimicking the epigenetic phenotype of SSc skin spontaneously recapitulate all the three features of SSc, including fibrosis and vasculopathy of the skin and lung, B cell activation, and autoantibody production. These studies implicate the epigenetic downregulation of Fli1 and KLF5 as a central event triggering the pathogenic triad of SSc.

Collagen XII and XIV, new partners of cartilage oligomeric matrix protein in the skin extracellular matrix suprastructure

The tensile and scaffolding properties of skin rely on the complex extracellular matrix (ECM) that surrounds cells, vasculature, nerves, and adnexus structures and supports the epidermis. In the skin, collagen I fibrils are the major structural component of the dermal ECM, decorated by proteoglycans and by fibril-associated collagens with interrupted triple helices such as collagens XII and XIV. Here we show that the cartilage oligomeric matrix protein (COMP), an abundant component of cartilage ECM, is expressed in healthy human skin. COMP expression is detected in the dermal compartment of skin and in cultured fibroblasts, whereas epidermis and HaCaT cells are negative. In addition to binding collagen I, COMP binds to collagens XII and XIV via their C-terminal collagenous domains. All three proteins codistribute in a characteristic narrow zone in the superficial papillary dermis of healthy human skin. Ultrastructural analysis by immunogold labeling confirmed colocalization and further revealed the presence of COMP along with collagens XII and XIV in anchoring plaques. On the basis of these observations, we postulate that COMP functions as an adapter protein in human skin, similar to its function in cartilage ECM, by organizing collagen I fibrils into a suprastructure, mainly in the vicinity of anchoring plaques that stabilize the cohesion between the upper dermis and the basement membrane zone.

Histomorphometric analysis of cutaneous remodeling in the early stage of the scleroderma model

INTRODUCTION/OBJECTIVES

Systemic sclerosis, or scleroderma, is a rheumatic disease characterized by autoimmunity, vasculopathy, and fibrosis of the skin and several internal organs. In the present study, our aim was to assess the skin alterations in animals with scleroderma during the first stages of disease induction.

METHODS

To induce scleroderma, female New Zealand rabbits (n = 12) were subcutaneously immunized with 1 mg/ml of collagen V (Col V) in complete Freund's adjuvant, twice with a thirty-day interval. Fifteen days later, the animals received an intramuscular booster with type V collagen in incomplete Freund's adjuvant, twice with a fifteen-day interval. The control group was inoculated with 1 ml of 10 mM acetic acid solution diluted with an equal amount of Freund's adjuvant. Serial dorsal skin biopsies were performed at 7, 15, and 30 days and stained with H&E, Masson's trichrome and Picrosírius for morphological and morphometric analyses.

RESULTS

Immunized rabbits presented a significant increase in collagen in skin collected seven days after the first immunization (p=0.05).

CONCLUSION

The results from this experimental model may be very important to a better understanding of the pathogenic mechanisms involved in the beginning of human SSc. Therapeutic protocols to avoid early remodeling of the skin may lead to promising treatments for SSc in the future.

Blocking sp1 transcription factor broadly inhibits extracellular matrix gene expression in vitro and in vivo: implications for the treatment of tissue fibrosis

Fibrosis is a consequence of injury characterized by accumulation of excess collagen and other extracellular matrix components, resulting in the destruction of normal tissue architecture and loss of function. Sp1 was originally described as a ubiquitous transcription factor. It is involved in the basal expression of extracellular matrix genes and may, therefore, be important in fibrotic processes. To evaluate the effect of Sp1 blockade on the expression of extracellular matrix genes, clones of NIH 3T3 fibroblasts stably transfected with an anti-sense Sp1 expression vector. Simultaneously reduced expression of several extracellular matrix genes as compared with mock-transfected clones was noted using differential hybridization of cDNA microarrays, without significant alteration in cell growth. Transfection of human dermal fibroblasts with several extracellular matrix gene (COL1A1, COL1A2, COL3A1, COL5A2, COL7A1, TIMP-1, and decorin) promoter/reporter constructs demonstrated that anti-sense Sp1-induced reduction of extracellular matrix gene mRNA steady-state levels results from transcriptional repression, consistent with the role of Sp1 as a transcription factor. Decoy Sp1 binding oligonucleotides inhibited COL1A2 promoter activity both in cultured fibroblasts and in vivo, in the skin of transgenic mice, which have integrated a mouse COL1A2 promoter/luciferase reporter gene construct. These results indicate that targeting Sp1 efficiently blocks extracellular matrix gene expression, and suggest that such an approach may represent an interesting therapeutic alternative toward the treatment of fibrotic disorders.

Disaccharide analysis of skin glycosaminoglycans in atrophoderma of Pasini and Pierini

There are divergent opinions as to whether atrophoderma of Pasini and Pierini (APP) is a nosologic entity or a primary atrophic morphoea. In this study, we used high performance liquid chromatography to analyse the skin disaccharide contents of glycosaminoglycan (GAG) in two patients with APP and compared the results with those from a typical atrophic morphoea patient. Perilesional uninvolved skin was used as a control in each patient. In the atrophic phase morphoea, both the total amount of disaccharide per skin punch-biopsy and the amount of DeltaDi-4S(DS) - the main disaccharide unit of dermatan sulphate - per mg dry weight were increased. These changes were consistent with sclerotic phase morphoea. In contrast, the total amount of disaccharide per skin punch-biopsy was decreased and the amount of DeltaDi-4S(DS) per mg dry weight was decreased or unchanged in APP. Our results suggest that GAG metabolism in APP may be unique and quite different from that in morphoea.

Remodeling of elastic fiber components in scleroderma skin

The skin of patients with scleroderma is characterized by an excess accumulation of collagen in the extracellular matrix of the fibrotic reticular dermis. Elastic fibers are also disrupted in this disease, however, in contrast to collagen, relatively few studies have provided information concerning the changes that occur to elastic fiber components in scleroderma. In the present study, the extracellular matrix in scleroderma skin was examined with a specific focus on the integrity of elastic fibers. Electron microscopic observations confirmed an excess of 10 nm microfibrils present in small bundles independent of amorphous elastin in the fibrotic reticular dermis. In the same area, a population of stellate-shaped fibroblasts was identified in close association with the dermal elastic fibers. In contrast to the uniform black appearance of the elastic fibers seen in the papillary dermis and in areas of the reticular dermis not infiltrated by these cells, the elastic fibers apposed to the cells were mottled in density and often almost electron-lucent. These observations suggest that the elastic fibers in the reticular dermis were being actively degraded. Results from this study provide evidence for disintegration of elastic fibers in the skin of scleroderma patients and suggest the possibility that degradation products from the elastic matrix in the diseased tissues may act as a feedback signal for increased matrix production.

Morphea and localized scleroderma in children

Localized scleroderma refers to a diverse spectrum of disorders that involve fibrosis of the skin. Children are more likely than adults to develop localized forms of scleroderma. This condition may have devastating effects on growth and development such as limb asymmetry, flexion contractures, and psychological disability. The pathogenesis of localized scleroderma is unknown but its possible relation to Borrelial infection is discussed. This article reviews associated laboratory and radiologic abnormalities, and discusses implications for monitoring disease activity. There is no universally effective therapy for this idiopathic condition and therapy is limited. A rationale for treatment based on disease subtype and severity is provided.

Circulating type I collagen degradation products: a new serum marker for clinical severity in patients with scleroderma?

Systemic sclerosis (SSc; scleroderma) results in the excessive deposition of extracellular matrix components in affected organs. This is partly due to enhanced synthesis; however, the role of degradative processes in this disease is still poorly understood. Sera of 32 patients with SSc (22 with the diffuse, 10 with the limited form) and of six patients with morphoea were assessed using radioimmunoassays for the cross-linked carboxy terminal telopeptide of type I collagen (ICTP) and for the amino terminal propeptide of type I procollagen (PINP) reflecting type I collagen degradation and synthesis, respectively. In 27 of the 32 patients with SSc, the concentration of ICTP was above the upper limit of the normal value (4.6 micrograms/L) and the mean level was clearly elevated at 7.92 micrograms/L. The ICTP concentration correlated with the skin score measuring the extent of the lesions, whereas no such correlation was found for PINP. The ICTP antigen in serum, studied by immunoblotting, had a molecular weight of about twice that of the trypsin-generated fragment isolated from human bone collagen. The mean concentration of serum PINP was 43.9 micrograms/L and no patient exceeded the upper limit of the normal range (80 micrograms/L). We report here for the first time that the concentration of the type I collagen degradation product ICTP in serum shows a close correlation with the extent of skin fibrosis in patients with SSc. We conclude that the increased deposition of type I collagen in this disease is accompanied by an increased turnover of this molecule, indicating a more complex derangement of synthetic and degradative processes than previously acknowledged.

Microfibrillar elements of the dermal matrix

Connective tissue microfibrils are key structural elements of the dermal matrix which play major roles in establishing and maintaining the structural and mechanical integrity of this complex tissue. Type VI collagen microfibrils form extensive microfibrillar networks which intercalate between the major collagen fibrils and are juxtaposed to cellular basement membranes, blood vessels and other interstitial structures. Fibrillin microfibrils define the continuous elastic network of skin, and are present in dermis as microfibril bundles devoid of measureable elastin extending from the dermal-epithelial junction and as components of the thick elastic fibres present in the deep reticular dermis. Electron microscopic analyses have revealed both classes of microfibrils to have complex ultrastructures. The ability to isolate intact native microfibrils from skin has enabled a combination of high resolution and biochemical techniques to be applied to elucidate their structure:function relationships. These approaches have generated new information about their molecular organisation and physiological interactions in health and disease.

Pathogenesis of scleroderma. Collagen

It is now evident that persistent overproduction of collagen and other connective tissue macromolecules results in excessive tissue deposition, and is responsible for the progressive nature of fibrosis in SSc. Up-regulation of collagen gene expression in SSc fibroblasts appears to be a critical event in the development of tissue fibrosis. The coordinate transcriptional activation of a number of extracellular matrix genes suggests a fundamental alteration in the regulatory control of gene expression in SSc fibroblasts. Trans-acting nuclear factors that bind to cis-acting elements in enhancer and promoter regions of the genes modulate the basal and inducible transcriptional activity of the collagen genes. The identity of the nuclear transcriptional factors that regulate normal collagen gene expression remains to be firmly established, and to date, no alterations in the level or in the activity of such DNA binding factors has been demonstrated in SSc fibroblasts. In addition to important interactions between fibroblasts and the extracellular matrix, cytokines and other cellular mediators can positively and negatively influence fibroblast collagen synthesis. Some of these signaling molecules may have physiologic roles, and their aberrant expression, or altered responsiveness of SSc fibroblasts to them, may result in the acquisition of the activated phenotype. The rapid expansion of knowledge regarding the effects of cytokines on extracellular matrix synthesis has led to an appreciation of the enormous complexity of regulatory networks that operate in the physiologic maintenance of connective tissue and which may be responsible for the occurrence of pathologic fibrosis. The ubiquitous growth factor TGF beta is the most potent inducer of collagen gene expression and connective tissue accumulation yet discovered. The expression of TGF beta in activated infiltrating mononuclear cells suggests a role for this cytokine as a mediator of fibroblast activation in SSc. Furthermore, the recognition that TGF beta is capable of inducing its own expression in a variety of cell types, coupled with the demonstration that a subpopulation of SSc dermal fibroblasts produces TGF beta, indicates the existence of a possible autocrine loop whereby lymphocyte-derived TGF beta in early SSc not only signals biosynthetic activation of fibroblasts in a paracrine manner, but autoinduces endogenous TGF beta production by the target fibroblasts themselves. Such an autocrine loop involving TGF beta may explain the persistent activation of collagen gene expression in SSc fibroblasts, and could be responsible for the progressive nature of fibrosis in SSc. Numerous other cytokines, as well as cell-matrix interactions, also modify collagen gene expression and can significantly influence the effects of TGF beta. Although their physiologic function in tissue remodeling or their involvement in abnormal fibrogenesis has not yet been conclusively demonstrated, the study of the biologic effects of these cytokines may provide important clues to understanding the pathogenesis of SSc, and to the development of rational drug therapy aimed at interrupting the abnormal fibrogenic process in this disease.

Differential regulation of transcription and transcript stability of pro-alpha 1(I) collagen and fibronectin in activated fibroblasts derived from patients with systemic scleroderma

Activated fibroblasts were derived from the skin of patients with systemic scleroderma (SSc), used as a model for fibrosis. Such cells are characterized by increased production of collagens and other matrix constituents. Increased collagen and fibronectin production has been correlated with similarly elevated mRNA steady-state levels. In the present study we analysed the contribution of transcriptional activity and post-transcriptional transcript stability to the increases in pro-alpha 1(I) collagen and fibronectin mRNA steady-state levels in activated (scleroderma) fibroblasts. Fibroblasts, when cultured in close contact with a three-dimensional collagenous matrix, down-regulate collagen synthesis. Culture of skin fibroblasts from two patients with SSc in three-dimensional collagen lattices, however, showed 4-fold elevated pro-alpha 1(I) collagen mRNA levels over fibroblasts from healthy donors. Transcription of the COL1A1 gene in SSc fibroblasts was induced 2-3-fold over that in controls in both monolayer and lattice cultures, accounting in part for the elevated steady-state level. A 50% decrease in transcription rate in lattice compared with monolayer culture occurred, as in control cells. In contrast, whereas control cells in lattices responded with decreased (50%) pro-alpha 1(I) collagen mRNA stability, in SSc cells these transcripts were found to be more stable (half-life of 5 h compared with 2 h in control cells). Fibronectin steady-state mRNA levels, in contrast, were not significantly regulated by the three-dimensional environment. In SSc fibroblasts, fibronectin mRNA levels were induced 1.5-4.9-fold over controls. In part, this increase appears to be due to elevated transcription, and an increase in fibronectin transcript stability was also detected. We therefore conclude that activated fibroblasts such as those derived from scleroderma patients utilize transcriptional and posttranscriptional mechanisms to maintain increased collagen and fibronectin production, which contribute to the pathogenesis of the disease.

Polarization microscopic investigation of collagen and acid glycosaminoglycans in the skin of progressive systemic sclerosis (PSS)

Collagen and acid glycosaminoglycans in the skin of progressive systemic sclerosis (PSS) were examined by polarization microscopy. Picrosirius Red and Toluidine Blue (pH 5.8) were used as stains. Digestion with chondroitinase ABC or streptomyces hyaluronidase were also employed. Under polarized light, the Picrosirius Red-stained collagen appeared green at any stage in PSS and orange in controls. Toluidine Blue-induced birefringence at stage I diminished in the presence of 0.2 M MgCl2 and in stage II in the presence of 0.3 M MgCl2. The collagen fibrils in PSS skin were significantly smaller in diameter than in controls. These results suggest that the change of polarization colours is due to the modulation of collagen thickness caused by an increased accumulation of acid glycosaminoglycans.

Regulation of connective tissue synthesis in systemic sclerosis

Excessive connective tissue deposition in the skin and other organs is the pathologic hallmark of systemic sclerosis (SSc), and fibrosis accounts for much of the chronic morbidity of this disease. Unregulated production of collagen in SSc skin fibroblasts has been demonstrated both in vivo and in vitro, and is considered to be a critical process in the development of fibrosis. In addition to collagen, other components of the extracellular matrix are also overexpressed in SSc fibroblasts, and may be important in the functional alterations of connective tissue. The transcriptional activity of several genes coding for matrix macromolecules is upregulated in SSc fibroblasts. The pleiotropic signaling molecule transforming growth factor-beta (TGF beta) is likely to be intimately involved in initiating and perhaps perpetuating the fibrotic response in SSc. TGF beta, a potent profibrotic cytokine, is highly expressed in endothelial cells, in fibroblasts near blood vessels, and in perivascular inflammatory cells in involved tissues in SSc. The apparent failure of SSc fibroblasts to down-regulate their collagen synthesis when cultured in a three-dimensional matrix suggest an additional mechanism for the maintenance of unregulated collagen production in these cells. Finally, subpopulations of fibroblasts with an activated biosynthetic phenotype may become dominant in SSc. Therefore, persistent elevation of extracellular matrix gene expression in SSc tissues may be the result of a series of events representing the interaction of genetic and hormonal factors. A precise delineation of the mechanisms of fibroblast activation is needed for understanding the pathogenesis of SSc, and for the rational design of therapeutic interventions aimed at interfering with the fibrotic process.

Elevated expression of type VII collagen in the skin of patients with systemic sclerosis. Regulation by transforming growth factor-beta

A hallmark of systemic sclerosis (SSc) is the development of tissue fibrosis. Excessive production of several connective tissue components normally present in the dermis, including type I, III, V, and VI collagens as well as fibronectin and proteoglycans, is a consistent finding in the skin of SSc patients. Type VII collagen is a major constituent of anchoring fibrils, present in the skin at the dermal-epidermal basement membrane zone. TGF-beta has been shown to upregulate the expression of the type VII collagen gene. In this study, we assessed the expression of type VII collagen and TGF-beta in the skin of patients with SSc. Indirect immunofluorescence showed an abundance of type VII collagen in the patients' skin, including the dermis. Ultrastructural analysis of SSc skin revealed an abundance of fibrillar material, possibly representing type VII collagen. The increased expression of type VII collagen epitopes was accompanied by the elevated expression of immunodetectable TGF-beta 1 and TGF-beta 2. Dermal fibroblasts cultured from the affected individuals showed a statistically significant (P < 0.02) increase in the expression of type VII collagen at the mRNA level, as detected by reverse transcription-PCR with a mutated cDNA as an internal standard, and increased deposition of the protein as assessed by indirect immunofluorescence. Thus, type VII collagen is abundantly present in SSc patients' dermis, a location not characteristic of its normal distribution, and its aberrant expression may relate to the presence of TGF-beta in the same topographic distribution. The presence of type VII collagen in the dermis may contribute to the tightly bound and indurated appearance of the affected skin in SSc patients.

Collagen alterations in chronically sun-damaged human skin

The major histological characteristic of sun-damaged skin is the accumulation of an elastotic material that appears to replace collagen. This elastotic material consists primarily of elastin and histological studies suggest a large loss of collagen in the dermis of chronically sun-damaged skin. In this study, we examine the content and distribution of collagen and procollagen in sun-damaged human skin. The total collagen content of sun-damaged skin was 20% less than nonsolar-exposed skin (524 micrograms collagen per mg total protein in sun-damaged skin and 667 micrograms collagen per mg total protein in nonsolar-exposed skin). In addition, there was a 40% decrease in the content of intact amino propeptide moiety of type III procollagen in sun-damaged skin (0.68 U per 50 mg wet weight) as compared to nonsolar-exposed skin (1.12 U per 50 mg wet weight). The data suggest that this change in collagen content is due to increased degradation. The distribution of collagen in sun-damaged skin was examined by indirect immunofluorescence. Mild digestion of sun-damaged skin with elastase removed the elastin and revealed the presence of collagen in the elastotic material. Therefore, the elastin appears to mask the presence of collagen fibers in the dermis of sun-damaged skin.

Control of fibrosis in systemic scleroderma

Scleroderma is characterized by an excessive deposition of collagen in all involved organs. This is due to an overproduction of extracellular matrix (ECM) molecules following induction of gene expression, whereas there is no evidence that the composition of the connective tissue matrix is altered. Several in vivo studies and in vitro experiments suggest that a close interaction between inflammatory cells and fibroblasts is required for the initial activation of fibroblasts. TGF-beta presumably plays an important role, but other cytokines, e.g., PDGF or FGF, may also be involved. Many of the ECM molecules have been shown to interact closely with fibroblasts and provide signals that regulate fibroblast metabolism. The cellular response towards those signals is a further aspect of fibrosis that has attracted attention during recent years. The altered expression of receptor proteins on the cell surface of scleroderma fibroblasts for example might explain in part the lack of down-regulation of collagen synthesis in late phases of the disease. This review summarizes the alterations of connective tissue in scleroderma, and discusses the role of cytokines as well as the ECM for the regulation of fibroblast function and their implication for the development of fibrosis.

Morphea with high titer of fibronectin antibodies

A 20-year-old man with a 9-year history of unusual subcutaneous morphea with nodular lesions in a circular arrangement and wooden-hard symmetrical induration of the arms, had high titers of fibronectin antibodies. A possible role of fibronectin and antifibronectin antibodies in the pathogenesis of scleroderma is discussed.

Endothelial and fibroblastic activation in scleroderma. The myth of the "uninvolved skin"

We studied the immunohistochemistry of the skin of scleroderma patients to determine the differences (if any) between clinically "affected" and "nonaffected" areas. We examined paired skin biopsy samples from clinically involved forearm skin ("affected") and clinically uninvolved proximal skin ("nonaffected") taken from 19 patients with diffuse scleroderma and from 15 normal control subjects. We stained the sections with antibodies to endothelial leukocyte-adherence molecule type 1 (ELAM-1; to detect endothelial activation) and to procollagen-1 (PC-1; to detect newly formed, unprocessed collagen). There was increased expression of ELAM-1 and PC-1 in sclerodermatous skin as compared with the controls, but there was no difference between clinically affected and nonaffected skin samples. In 10 of 11 patients whose condition was getting worse, endothelial and fibroblast activation preceded fibrosis. Endothelial and fibroblast activation are more widespread in the skin of scleroderma patients than is evident by inspection on physical examination. What appears to be "normal" skin in diffuse scleroderma is already pathologic, as shown by abnormal endothelial activation and procollagen production.

Steady-state mRNA levels of collagens I, III, fibronectin, and collagenase in skin biopsies of systemic sclerosis patients

Total RNA was extracted from skin biopsies of nine patients suffering from systemic sclerosis (SSc). Steady-state mRNA levels of collagen alpha 1(I) and alpha 1(III), collagenase, fibronectin, and beta-actin were studied using specific cDNA probes and compared to those of 12 sex- and age-matched healthy individuals. There was a more than three-fold elevation of collagen I mRNA levels in SSc skin compared to controls. No difference was found, however, for collagen III, collagenase, and fibronectin mRNA levels in SSc and control biopsies. The selective increase of collagen alpha 1(I) mRNA levels indicates a specific alteration of fibroblast metabolism in scleroderma. Analysis of mRNA levels in skin biopsies might not only offer a direct approach to the understanding of the pathophysiology of SSc, but also facilitate the monitoring of fibrotic activity in SSc patients during therapeutic trials.

Collagen type I and III occur together in hybrid fibrils in the space of Disse of normal rat liver

Collagen type I and procollagen type III were localized at the ultrastructural level on ultrathin frozen sections of rat liver by the protein A-gold technique using affinity-purified primary antibodies. Both collagen type I and procollagen type III were localized on nearly all solitary and bundled fibrils in the space of Disse. Simultaneous localization of collagen type I and procollagen type III by a double-labeling procedure using protein A-gold probes of different sizes unequivocally demonstrated the presence of both collagens in the same fibrils. Measurement of the diameter of large numbers of collagen fibrils in the space of Disse of the rat liver showed a unimodal distribution of the fibril diameters around an average value of 62.4 nm (S.D. = 12.8 nm), and 91% of the collagen bundles contained less than 30 fibrils. Additional measurements on epoxy resin-embedded material of five biopsy specimens of normal human liver showed a comparable unimodal distribution of the fibril diameters around an average value of 57.2 nm (S.D. = 9.6 nm), and 74% of the bundles contained less than 60 fibrils. The latter observation demonstrates that human liver contains broader interstitial collagen bundles than rat liver. From these results, we conclude that the space of Disse of normal rat and human liver contains a uniform population of striated interstitial collagen fibrils. In the rat liver, these fibrils contain both collagen type I and procollagen type III. Therefore the concept that procollagen type III is predominantly localized in small diameter fibrils or bundles, whereas collagen type I is preferentially localized in thick ones, does not hold.

Histochemical differentiation of localized morphea-scleroderma and lichen sclerosus et atrophicus

Dermatologic literature has debated the occurrence of concomitant morphea-scleroderma (M-S) and lichen sclerosus et atrophicus (LSA) for sometime. Presentation of a case which has the appearance of both M-S and LSA creates a diagnostic dilemma frequently unresolved even by histopathology. Routine hematoxylin and eosin stained sections may add to the confusion and the difficulty of the differentiation, but examination for the presence or absence of elastic fibers in the upper corium of the lesions affords a definitive separation of these two conditions.

Alterations in dermal collagen in ultraviolet irradiated hairless mice

Chronic exposure of the skin to sunlight results in severe dermal connective tissue damage that is characterized by the basophilic degeneration of collagen and the accumulation of an elastotic material. The aim of this study was to identify changes in collagen (the major structural protein of the skin) in ultraviolet irradiated mouse skin using immunochemical and biochemical techniques. Specific antibodies directed against the aminopropeptide of type III procollagen were used in immunofluorescence and immunoblotting studies. Immunofluorescent staining of irradiated and nonirradiated mice skin showed that the aminopropeptide of type III procollagen was distributed throughout the dermis in a pattern similar to that observed for type I collagen. Extracts of irradiated (5 and 10 weeks) and nonirradiated skins were then subjected to immunoblotting techniques. Levels of pN alpha 1, type III procollagen (measured by radioimmunoassay) were reduced in the extracts prepared from skins of mice that were irradiated for 5 and 10 weeks. Immunoelectron microscopy verified the loss of pN alpha 1 type III procollagen in irradiated skin. Collagen fibers of nonirradiated skin demonstrated normal labeling with antibody directed against the aminopropeptide of type III procollagen. In contrast, collagen fibers of 10 week irradiated skin failed to label with this antibody. The pN alpha 1 type III collagen is known to coat type I collagen fibers of normal skin. Therefore, its absence from the surface of type I collagen fibers of irradiated skin may play a role in the development of the elastotic material.