Increased collagen biosynthesis and increased expression of type I and type III procollagen genes in tight skin (TSK) mouse fibroblasts

cRel expression regulates distinct transcriptional and functional profiles driving fibroblast matrix production in systemic sclerosis

OBJECTIVES

NF-κB regulates genes that control inflammation, cell proliferation, differentiation and survival. Dysregulated NF-κB signalling alters normal skin physiology and deletion of cRel limits bleomycin-induced skin fibrosis. This study investigates the role of cRel in modulating fibroblast phenotype in the context of SSc.

METHODS

Fibrosis was assessed histologically in mice challenged with bleomycin to induce lung or skin fibrosis. RNA sequencing and pathway analysis was performed on wild type and Rel-/- murine lung and dermal fibroblasts. Functional assays examined fibroblast proliferation, migration and matrix production. cRel overexpression was investigated in human dermal fibroblasts. cRel immunostaining was performed on lung and skin tissue sections from SSc patients and non-fibrotic controls.

RESULTS

cRel expression was elevated in murine lung and skin fibrosis models. Rel-/- mice were protected from developing pulmonary fibrosis. Soluble collagen production was significantly decreased in fibroblasts lacking cRel while proliferation and migration of these cells was significantly increased. cRel regulates genes involved in extracellular structure and matrix organization. Positive cRel staining was observed in fibroblasts in human SSc skin and lung tissue. Overexpression of constitutively active cRel in human dermal fibroblasts increased expression of matrix genes. An NF-κB gene signature was identified in diffuse SSc skin and nuclear cRel expression was elevated in SSc skin fibroblasts.

CONCLUSION

cRel regulates a pro-fibrogenic transcriptional programme in fibroblasts that may contribute to disease pathology. Targeting cRel signalling in fibroblasts of SSc patients could provide a novel therapeutic avenue to limit scar formation in this disease.

Bi-directional communication: Conversations between fibroblasts and immune cells in systemic sclerosis

Systemic Sclerosis (SSc) is an autoimmune idiopathic connective tissue disease, characterized by aberrant fibro-proliferative and inflammatory responses, causing fibrosis of multiple organs. In recent years the interactions between innate and adaptive immune cells with resident fibroblasts have been uncovered. Cross-talk between immune and stromal cells mediates activation of stromal cells to myofibroblasts; key cells in the pathophysiology of fibrosis. These cells and their cytokines appear to mediate their effects in both a paracrine and autocrine fashion. This review examines the role of innate and adaptive immune cells in SSc, focusing on recent advances that have illuminated our understanding of ongoing bi-directional communication between immune and stromal cells. Finally, we appraise current and future therapies and how these may be useful in a disease that currently has no specific disease modifying treatment.

Pathophysiology of systemic sclerosis: state of the art in 2014

Major work has been done in order to improve the understanding of systemic sclerosis (SSc) pathogenesis. A number of new experimental models have been set up, that should help to understand the disease pathogenesis and test new therapeutic targets. Reactive oxygen species represent a hallmark of the pathogenesis of SSc, both at the fibroblast and at the endothelial cell levels. Although a large number of genetic studies have been conducted, it is still difficult to identify a genetic background specific to SSc, and the major progress in this setting is probably the identification of an interferon signature. Besides endothelial cells and fibroblasts, major development has been made in the understanding of the role of B cells and autoantibodies in the pathogenesis of SSc. Plasmacytoid dendritic cells seem to play a major role in the pathogenesis of SSc through the secretion of CXCL4, although these data will need to be confirmed in the near future.

TGF-β-mediated downregulation of microRNA-196a contributes to the constitutive upregulated type I collagen expression in scleroderma dermal fibroblasts

Previous reports indicated the significance of the TGF-β signaling in the pathogenesis of systemic sclerosis. We tried to evaluate the possibility that microRNAs (miRNAs) play a part in the type I collagen upregulation seen in normal fibroblasts stimulated with exogenous TGF-β and systemic sclerosis (SSc) fibroblasts. miRNA expression profile was evaluated by miRNA PCR array and real-time PCR. The protein expression of type I collagen was determined by immunoblotting. In vivo detection of miRNA in paraffin section was performed by in situ hybridization. Several miRNAs were found to be downregulated in both TGF-β-stimulated normal fibroblasts and SSc fibroblasts compared with normal fibroblasts by PCR array. Among them, miR-196a expression was decreased in SSc both in vivo and in vitro by real-time PCR or in situ hybridization. In SSc fibroblasts, miR-196a expression was normalized by TGF-β small interfering RNA. miR-196a inhibitor leads to the overexpression of type I collagen in normal fibroblasts, whereas overexpression of the miRNA resulted in the downregulation of type I collagen in SSc fibroblasts. In addition, miR-196a was detectable and quantitative in the serum of SSc patients. Patients with lower serum miR-196a levels had significantly higher ratio of diffuse cutaneous SSc:limited cutaneous SSc, higher modified Rodnan total skin thickness score, and higher prevalence of pitting scars than those without. miR-196a may play some roles in the pathogenesis of SSc. Investigation of the regulatory mechanisms of type I collagen expression by miR-196a may lead to new treatments using miRNA.

Animal models of cutaneous and hepatic fibrosis

Fibrosis occurs as a part of normal wound healing. However, excessive or dysregulated fibrosis can lead to severe organ dysfunction and is a feature of a variety of diseases. Due to its insidious onset, fibrosis tends to go undetected in its early stages. This is in part why these diseases remain so poorly understood. Animal models have provided a means to examine these early stages and to isolate and understand the effect of perturbations in signaling pathways, chemokines, and cytokines. Here, we summarize recent progress in the understanding of the molecular pathogenesis of fibrosis, both its initiation and its maintenance phases, from animal models of fibrosis in the skin and liver. Due to these organs' properties, modeling fibrosis in them poses unique challenges. Elegant solutions have therefore been developed for modeling fibrosis in each, and now, great potential for animal models to contribute to our understanding appears scientifically imminent.

Molecular pathogenesis of skin fibrosis: insight from animal models

Skin fibrosis occurs in a variety of human diseases, most notably systemic sclerosis (SSc). The end stage of scleroderma in human skin consists of excess collagen deposition in the dermis with loss of adnexal structures and associated adipose tissue. The initiating factors for this process and the early stages are believed to occur through vascular injury and immune dysfunction with a dysregulated inflammatory response. However, because of the insidious onset of the disease, this stage is rarely observed in humans and remains poorly understood. Animal models have provided a means to examine these early stages and to isolate and understand the effect of perturbations in signaling pathways, chemokines, and cytokines. This article summarizes recent progress in the understanding of the molecular pathogenesis of skin fibrosis in SSc from different animal models, both its initiation and its maintenance phases.

BAFF Antagonist Attenuates the Development of Skin Fibrosis in Tight-Skin Mice

The tight-skin (TSK/+) mouse, a genetic model for systemic sclerosis (SSc), develops cutaneous fibrosis and autoimmunity. Although immunological abnormalities have been demonstrated in TSK/+ mice, the roles of B-cell-activating factor belonging to the tumor necrosis factor family (BAFF), a potent B-cell survival factor, have not been investigated. Serum BAFF levels in TSK/+ mice were examined by ELISA. Newborn TSK/+ mice were treated with BAFF antagonist, and then skin fibrosis of 8-week-old mice was assessed. Serum BAFF levels were significantly elevated in TSK/+ mice. Remarkably, BAFF antagonist inhibited the development of skin fibrosis, hyper-gamma-globulinemia, and the autoantibody production in TSK/+ mice. The skin from TSK/+ mice showed upregulated expressions of fibrogenic cytokines, such as IL-6 and IL-10, while BAFF antagonist significantly suppressed them. Reciprocally, BAFF antagonist augmented antifibrogenic cytokines, such as IFN-gamma, in the skin of TSK/+ mice. Furthermore, TSK/+ B cells with BAFF stimulation had a significantly enhanced ability to produce IL-6. The results suggest that BAFF/BAFF receptor system is critical for the development of skin fibrosis in TSK/+ mice and could be a potent therapeutical target.

B-lymphocyte depletion reduces skin fibrosis and autoimmunity in the tight-skin mouse model for systemic sclerosis

Systemic sclerosis (scleroderma) is an autoimmune disease characterized by excessive extracellular matrix deposition in the skin. A direct role for B lymphocytes in disease development or progression has remained controversial, although autoantibody production is a feature of this disease. To address this issue, skin sclerosis and autoimmunity were assessed in tight-skin mice, a genetic model of human systemic sclerosis, after circulating and tissue B-cell depletion using an anti-mouse CD20 monoclonal antibody before (day 3 after birth) and after disease development (day 56). CD20 monoclonal antibody treatment (10 to 20 microg) depleted the majority (85 to 99%) of circulating and tissue B cells in newborn and adult tight-skin mice by days 56 and 112, respectively. B-cell depletion in newborn tight-skin mice significantly suppressed (approximately 43%) the development of skin fibrosis, autoantibody production, and hypergammaglobulinemia. B-cell depletion also restored a more normal balance between Th1 and Th2 cytokine mRNA expression in the skin. By contrast, B-cell depletion did not affect skin fibrosis, hypergammaglobulinemia, and autoantibody levels in adult mice with established disease. Thereby, B-cell depletion during disease onset suppressed skin fibrosis, indicating that B cells contribute to the initiation of systemic sclerosis pathogenesis in tight-skin mice but are not required for disease maintenance.

Early emphysema in the tight skin and pallid mice: roles of microfibril-associated glycoproteins, collagen, and mechanical forces

The nature of the development of emphysema in the tight skin (Tsk) and the pallid (Pa) mice are not well understood. We assessed the mechanical and nonlinear properties of the respiratory system, the alveolar structure, and the levels of microfibril-associated glycoproteins (MAGP) 1 and 2 in Tsk mice with developmental emphysema; in Pa mice, which are thought to develop adult onset emphysema; and their background, the C57BL/6 mice, at an age of 7 wk. Minor differences between collagen-related elastic properties of the lungs of the Pa and C57BL/6 mice were seen at this early age. The lungs of the Tsk mice were significantly softer yet more nonlinear than those of the Pa and C57BL/6 mice. The MAGP-1 levels were similar in all three groups. However, the level of MAGP-2, which is associated with both fibrillin-1 and collagen, was higher in the Tsk than in the Pa mice, which also had more MAGP-2 than the C57BL/6. Both the mean and the variance of alveolar diameters were larger in the Tsk than in the other two groups, while the variance in the Pa was larger than in the C57BL/6 mice, implying early development of heterogeneity. Using a network model of the parenchyma, we linked the pathophysiologic changes in the Tsk mice to mechanical forces and failure of the alveolar walls. Our findings suggest the possibility that MAGP-2-related abnormal collagen assembly, combined with mechanical forces, is involved in the progression of emphysema in the Tsk mice.

Analysis of the tight skin (Tsk1/+) mouse as a model for testing antifibrotic agents

The tight skin 1 (B6.CgFbn1(Tsk)+/+Pldn(pa)/J, henceforth referred to as Tsk1/+) mouse was first described as a spontaneously occurring mutant that resulted in hyperplasia of the subcutaneous loose connective tissue, and has subsequently been proposed to be a model of the human fibrotic disorder scleroderma. We have investigated the Tsk1/+ mouse as a model system for testing the efficacy of antifibrotic agents against skin fibrosis. We find that the tightness of the skin at the scruff of the neck leads to a measurably thicker skin pinch, but we suggest that this is due to hyperplasia of the subdermal loose connective tissue, which results in increased tethering of the skin to the underlying muscle layers. In contrast to previously published data, we do not find a significant difference in the dermal thickness or collagen content of the Tsk1/+ mouse skin compared with wild-type controls. In addition, expression profiling of Tsk1/+ mouse skin indicated that there are very few changes in gene expression, and that there is no evidence for upregulation of the transforming growth factor beta signaling axis. Therefore, we conclude that this model is not suitable for testing the effect of antifibrotic agents on the dermis, and that changes potentially related to scleroderma may be confined to subdermal connective tissue.

Animal models in scleroderma

Scleroderma or systemic sclerosis is an insidious connective tissue disease with no known cure. A hallmark feature of scleroderma is the excess synthesis and deposition of collagen resulting in a fibrotic state. In scleroderma, fibrosis is not confined only to the skin but impacts internal organs as well. In an effort to better understand the pathophysiology of this disease, researchers have developed a variety of animal models that display features of the human condition. This paper focuses on mouse models of scleroderma and summarizes work conducted with these experimental paradigms that is focused on understanding the cellular and molecular events associated with the onset and maintenance of fibrosis.

Therapeutic effect of CpG-enriched plasmid administration on the tight-skin mouse model of scleroderma

Immunostimulatory CpG motifs can preferentially induce Th1 immune responses and have been applied to treat Th2-dominant disease. In this study, we investigated whether a plasmid with the addition of 20 copies of an immunostimulatory CpG motif (pB-CpG20) might prevent the development of scleroderma-like syndrome in tight-skin (Tsk/+) mice. Administration of pB-CpG20 to Tsk/+mice every 3 weeks starting at the age of 1 week reduced skin thickness and collagen content compared to that of pB or saline. The reduction was long lasting even after halting the treatment. Furthermore, this treatment partially reduced the production of anti-nuclear antibodies although it did not decrease the incidence of lung emphysema. pB-CpG20 increased the number of spleen cells secreting IFN-gamma and reduced that of the cells secreting IL-4 in vivo and in vitro compared to saline. These results suggest that repeated administration of a CpG-enriched plasmid can ameliorate scleroderma-like syndrome by biasing Th1 immunity in young Tsk/+mice.

Fibulin-2 and fibulin-5 alterations in tsk mice associated with disorganized hypodermal elastic fibers and skin tethering

The Tight skin (Tsk) mouse is an important model of skin fibrosis that occurs in systemic sclerosis. These mice develop skin tethering and thickening associated with expression of a mutant fibrillin-1 gene. We show that Tsk fibrillin-1 leads to marked alterations in elastic fibers of the hypodermis of Tsk animals. In Tsk mice, a prominent elastic fiber layer found normally at the interface between hypodermal muscle and connective tissue was absent from an early age. The lack of elastic fibers at the hypodermal muscle-connective tissue (M-CT) interface was associated with a loss of staining for fibulin-5 in the same region. These mice also formed disorganized elastic fibers throughout hypodermal connective tissue as they aged. The increased elastic fibers in Tsk hypodermal connective tissue was associated with increased fibrillin-1 and fibulin-2 matrices. These results suggest that Tsk fibrillin-1 causes skin tethering by altering matrix protein composition in Tsk hypodermal connective tissues. The closely parallel alterations in elastogenesis associated with increased fibulin-2 in hypodermal connective tissues and decreased fibulin-5 at the hypodermal M-CT interface suggest that these proteins mediate the effect of Tsk-fibrillin-1 on elastogenesis.

Mutant fibrillin 1 from tight skin mice increases extracellular matrix incorporation of microfibril-associated glycoprotein 2 and type I collagen

OBJECTIVE

Skin fibrosis in the TSK mouse, a model of skin fibrosis seen in systemic sclerosis (SSc), is caused by a large in-frame duplication in the Fbn1 gene, tsk-Fbn1. We investigated whether tsk-Fbn1 might cause dermal fibrosis by affecting Fbn1 and associated extracellular matrices. We also studied whether deposition of microfibril-associated glycoprotein 2 (MAGP-2), a protein that is associated with fibrillin 1, was altered in the skin of patients with SSc.

METHODS

An in vitro model of the TSK mouse was created by conditionally expressing tsk-Fbn1 in mouse embryonic fibroblasts (MEFs). Cell cultures were examined by immunofluorescence and Western and Northern blotting to determine the effect of tsk-Fbn1 on the structure, expression, and deposition of fibrillin 1 (Fbn-1), type I collagen, and MAGP-2. The skin of TSK mice and SSc patients was analyzed by immunohistochemistry for MAGP-2 expression.

RESULTS

Expression of tsk-Fbn1 in cultured MEF cells altered the morphology of Fbn-1 fibers and increased the deposition of type I collagen into the extracellular matrix (ECM) without concomitantly changing messenger RNA expression, secretion, or processing of type I procollagen. Moreover, MEF cells expressing tsk-Fbn1 showed increased MAGP-2 matrix. MAGP-2 was increased in the dermis of TSK mice. Fibrotic SSc skin also showed higher levels of MAGP-2 in the dermis than nonfibrotic SSc skin and normal skin.

CONCLUSION

Tsk-Fbn1 altered ECM organization and caused fibrosis by affecting the deposition of MAGP-2 or other Fbn-1-associated proteins. Alterations in microfibril structure or deposition might contribute to fibrosis in SSc.

Sustained activation of fibroblast transforming growth factor-beta/Smad signaling in a murine model of scleroderma

Transforming growth factor-beta is responsible for triggering a cascade of events leading to fibrosis in scleroderma. The Smads are intracellular signal transducers recently shown to mediate fibroblast activation and other profibrotic responses elicited by transforming growth factor-betain vitro. To understand better the involvement of Smads in the pathogenesis of fibrosis, we examined Smad expression and activation in situ in a murine model of scleroderma. Bleomycin injections induced striking dermal infiltration with macrophages by 3 d, and progressive fibrosis by 2 wk. Infiltrating macrophages and resident fibroblasts expressed Smad3, the positive mediator for transforming growth factor-beta responses. Importantly, in bleomycin-injected skin, fibroblasts showed predominantly nuclear localization of Smad3 and intense staining for phospho-Smad2/3. Furthermore, phosphorylated Smad2/3 in fibroblasts was detected even after the resolution of inflammation. Expression of Smad7, the endogenous inhibitor of transforming growth factor-beta/Smad signaling, was strongly induced in dermal cells by transforming growth factor-beta, but not by bleomycin injections. Collectively, these results indicate that bleomycin-induced murine scleroderma is associated with rapid and sustained induction of transforming growth factor-beta/Smad signaling in resident dermal fibroblasts. Despite apparent activation of the intracellular transforming growth factor-beta signaling pathway in the lesional dermis, the expression of transforming growth factor-beta-inducible Smad7 was not upregulated. In light of the critical function of Smad7 as an endogenous inhibitor of Smad signaling that restricts the duration and magnitude of transforming growth factor-beta responses, and as a mediator of apoptosis, relative Smad7 deficiency observed in the present studies may account for sustained activation of transforming growth factor-beta/Smad signaling in lesional tissues. These findings raise the possibility that Smads plays an important part in the pathogenesis of fibrosis, and may therefore represent targets for selective anti-fibrotic interventions.

Halofuginone to treat fibrosis in chronic graft-versus-host disease and scleroderma

Chronic graft-versus-host disease (cGvHD) and systemic sclerosis (scleroderma [SSc]) share clinical characteristics, including skin and internal organ fibrosis. Fibrosis, regardless of the cause, is characterized by extracellular matrix deposition, of which collagen type I is the major constituent. The progressive accumulation of connective tissue results in destruction of normal tissue architecture and internal organ failure. In both SSc and cGvHD, the severity of skin and internal organ fibrosis correlates with the clinical course of the disease. Thus, there is an unmet need for well-tolerated antifibrotic therapy. Halofuginone is an inhibitor of collagen type I synthesis in cells derived from various tissues and species and in animal models of fibrosis in which excess collagen is the hallmark of the disease. Halofuginone decreased collagen synthesis in the tight skin mouse (Tsk) and murine cGvHD, the 2 experimental systems that show many features resembling those of human GvHD. Inhibition of collagen synthesis by halofuginone is achieved by inhibiting transforming growth factor beta-dependent Smad3 phosphorylation. Dermal application of halofuginone caused a decrease in collagen content at the treated site of a cGvHD patient, and reduction in skin scores was observed in a pilot study with SSc patients. The results of the human studies provide basis for using halofuginone treatment for dermal fibrosis. As a first step toward future treatment of internal organ involvement, an oral administration study was performed in which halofuginone was well tolerated and plasma levels surpassed the predicted therapeutic exposure.

Transcriptional activation of alpha 1(III) procollagen gene in Tsk2/+ dermal fibroblasts

Transient transfection experiments into Tsk2/+ and normal dermal fibroblasts were performed using four successively shorter Col3a1 promoter deletion constructs: #103, #110, #114, and #120 fused to the chloramphenicol-acetyl-transferase (CAT) reporter gene. The transcriptional activity in Tsk2/+ and normal dermal fibroblasts driven by the three longer constructs was equal. With the shortest construct, #120 (-96 to +16bp) the transcriptional activity in Tsk2/+ fibroblasts was 25 times higher than in normal fibroblasts. Electrophoretic mobility shift assays with a labeled #120 probe revealed that increased DNA-protein binding occurred with nuclear extracts prepared from Tsk2/+ fibroblasts and that this binding was displaced by consensus Sp1 and NF-1 oligonucleotide sequences. These data indicate that sequences from -96 to +16bp of the Col3a1 promoter play an important role in the upregulated expression of this gene in Tsk2/+ fibroblasts and that the promoter contains sequences which bind the trans-acting nuclear factors, Sp1(like) and NF-1(like).

Murine animal models of systemic sclerosis

Animal models of systemic connective tissue diseases have provided valuable insights into the causative mechanisms and the pathogenesis of these diseases, and have provided the means to test potentially useful therapeutic interventions. Although numerous animal models for systemic sclerosis (SSc) have been described, the most extensively studied are murine. One advantage of murine animal models is the large body of genetic information available for the mouse that is not available for other species. No animal model described to date reproduces precisely all manifestations of SSc. However, all animal models display tissue fibrotic changes similar to those present in SSc. The prudent interpretation of the results obtained from the study of animal models has provided substantial and valuable information about the pathogenesis of the human disease.

Association of 5'-untranslated region of the Fibrillin-1 gene with Japanese scleroderma

Excessive production of extracellular matrix (ECM) constituents is a hallmark scleroderma or systemic sclerosis (SSc). Fibrillin-1, a major component of microfibrils in the ECM, may play a role in the pathogenesis of SSc. The TSK1 mouse model of SSc bears an in-frame duplication of the Fibrillin-1 gene (FBN1) which results in a larger than normal protein that is more susceptible to proteolysis. Metabolic labeling studies of Fibrillin-1 in human SSc dermal fibroblasts demonstrated that while normal amounts of Fibrillin-1 are synthesized, the protein itself appears to be unstable. Moreover, autoantibodies specific for Fibrillin-1 have been demonstrated in serum from SSc patients and TSK1 mice. In particular, a high frequency of anti-Fibrillin-1 was observed in Japanese patients with diffuse and limited scleroderma or CREST (calcinosis, Raynaud phenomenon, esophageal dysmotility, sclerodactyly, telangiectasia) syndrome. Genetic studies in a Native American population with high prevalence of using microsatellite marker showed strong association between FBN1 haplotypes and SSc. Subsequently, studies of FBN1 single nucleotide polymorphisms (SNPs) demonstrated that certain FBN1 haplotypes were associated with SSc in both Native American and Japanese patients with limited scleroderma. Thus, FBN1 was sequenced in 22 Japanese SSc patients to ascertain the presence of any relevant mutations or SNPs. Sequence analysis revealed eight coding and 14 non-coding SNPs and other polymorphisms. Among them, a CT insertion in the 5'-untranslated region of exon A had a significant negative association with disease.

Reduction in dermal fibrosis in the tight-skin (Tsk) mouse after local application of halofuginone

The effect of dermal application of halofuginone-an inhibitor of collagen type I synthesis-on skin collagen and collagen alpha1(I) gene expression in an animal model of scleroderma and chronic graft versus host disease (cGvHD) was evaluated. Halofuginone-containing cream was applied on the tight-skin mouse (Tsk) and skin biopsies were taken for collagen staining by sirius red and for collagen alpha1(I) gene expression by in situ hybridization. In addition, cell proliferation was evaluated by immunostaining for proliferation cell nuclear antigen (PCNA) alone or in combination with collagen alpha1(I) probe. The number of mast cells was assessed by toluidine blue. Dermal application of halofuginone (0.01%) for 60 days was as good as systemic administration (1 microg/mouse/day) in reducing collagen alpha1(I) gene expression in skin biopsy and almost as good in reducing skin width. Halofuginone was stable and effective only at acidic pH. The effect of halofuginone (0.03%) was time-dependent. After 40 days of daily treatment, a significant reduction in the collagen alpha1(I) gene expression was observed and further decrease was observed after 60 days. The reduction in collagen alpha1(I) gene expression and the reduction in the proliferation of dermal fibroblasts probably occur in the same subset of cells. No effect of halofuginone on the proliferation of keratinocytes or on mast cell number was observed. These results suggest that target-oriented application of halofuginone may become a novel therapy for fibrotic disorders in general and for scleroderma in particular.

Activation of a fibroblast-specific enhancer of the proalpha2(I) collagen gene in tight-skin mice

OBJECTIVE

Reporter transgenes were introduced into the type 1 tight-skin (Tsk1/+) mouse model of scleroderma to test the hypothesis that fibroblast-specific genetic programs are activated in fibrosis.

METHODS

Transgenes harboring upstream fragments of the 5' flanking region of the mouse proalpha2(I) collagen gene (Col1a2), linked to a 400-bp minimal Col1a2 promoter driving an Escherichia coli beta-galactosidase (LacZ) reporter gene, were introduced into Tsk1/+ mice by breeding. Expression of these transgenes, which function as lineage-specific markers of fibroblast differentiation, was compared between the Tsk-LacZ mice and non-Tsk littermates. Responsiveness of these constructs to the profibrotic cytokine, transforming growth factor beta1 (TGFbeta1), was investigated by transient transfection of reporter constructs in tissue-culture cells.

RESULTS

There was significant activation of reporter genes harboring the upstream enhancer in Tsk1/+ mice starting from 1 week of age. This was maximal at 6 weeks old (mean +/- SD 237 +/- 24% of non-Tsk controls; P= 0.001). Recombinant TGFbeta1 significantly activated reporter genes regulated by the upstream enhancer in transient transfection, and Tsk-LacZ fibroblasts showed elevated LacZ expression in tissue culture.

CONCLUSION

These data suggest that activating signals in Tsk1/+ mice may act via fibroblast-specific regulatory elements within the murine Col1a2 gene. Although TGFbeta has been implicated in the pathogenesis of fibrosis, and reporter genes regulated by the upstream enhancer appear to be TGFbeta responsive in vitro, our results suggest that fibroblast-specific pathways may also be involved.

Effect of IL-12 encoding plasmid administration on tight-skin mouse

The tight-skin (Tsk/+) mutant mice, a putative murine model of scleroderma, are characterized by the excessive deposition of collagen and the presence of antinuclear antibodies. Type 2 cytokines, such as IL-4 and IL-6, are capable of regulating the synthesis of various matrix molecules, including type I collagen, by fibroblasts. IL-12 is well known to induce type 1 cytokine production and to reduce type 2 activity. Here, we examined the effect of IL-12 encoding plasmid (pCAGGSIL-12) on the disease progression of Tsk/+ mice. pCAGGSIL-12 plasmid or pCAGGS parental vector was injected intramuscularly 7 times at 3 week intervals into Tsk/+ mice. One week after the last injection, pCAGGSIL-12 administered Tsk/+ mice exhibited a marked decrease in the skin thickness compared with the mice treated with pCAGGS vector. The serum levels of antinuclear antibodies were diminished in pCAGGSIL-12 treated mice. IL-4 production by spleen cells from pCAGGSIL-12 plasmid treated mice was significantly lower than that from vector treated mice. These results indicate that pCAGGSIL-12 administration into Tsk/+ mice had beneficial effects in preventing the collagen accumulation in the skin and suppressing the autoimmunity via improvement of Th1/Th2 balance. The present study suggests that the IL-12 encoding plasmid administration might have a therapeutic effect on systemic sclerosis.

Genetic and immunologic features associated with scleroderma-like syndrome of TSK mice

Tight-skin (TSK) mouse, the experimental model for scleroderma, develops cutaneous hyperplasia and autoantibodies to scleroderma specific autoantigens. TSK syndrome is caused by a mutation on chromosome 2. Induction of cutaneous hyperplasia is due to intragenic duplication of exons 17 to 40 of fibrillin-1 gene, mapping close to TSK locus. The mutant mouse expresses a 14kb Fbn transcript in addition to 11kb wild-type transcript. Immunoprecipation analysis confirms that the mutant transcript is functional and codes for a 420kD fibrillin. The occurrence of TSK syndrome is independent of the presence of mature lymphocytes although splenic/bone marrow cells appear to be capable of transferring the disease in normal animals. Transgenic mice expressing mutant transgene develop mild skin thickness with associate biochemical changes but do not develop anti-topo I antibodies. Among the other factors that may contribute to the develop- ment of hyperplasia, collagen V seems to play an important role.

Characterization of mutated protein encoded by partially duplicated fibrillin-1 gene in tight skin (TSK) mice

Fibrillin-1 (Fbn-1) is a ubiquitous protein present in the extracellular matrix of various organs and it is a major component of microfibrils embedded in the core of elastic fibers. In humans, mutations or deletions of the Fbn-1 gene are associated with several genetic diseases. In addition, several microsatellite alleles near Fbn-1 gene were found associated with diffuse scleroderma. In TSK/+ mice, which develop a scleroderma-like syndrome, the Fbn-1 gene exhibits an inframe duplication of exons 17-40. In this study, we report that the synthesis and secretion of wild-type Fbn-1 in TSK/+ is higher than that of the mutated Fbn-1 protein excluding the possibility that TSK genetic defect is due to a loss of the wild allele. We also demonstrate for the first time that TGF-beta, which plays a crucial role in skin fibrosis, binds to both wild-type and mutated Fbn-1. The amount of bound TGF-beta was higher in mutated than wild-type Fbn-1 and appears related to the number of TGF-beta binding motifs.

Spontaneous occurrence of anti-fibrillin-1 autoantibodies in tight-skin mice

Tight-skin (TSK) mouse represents an experimental for systemic sclerosis, displaying cutaneous hyperplasia, connective tissue alterations in the internal organs and developing autoantibodies against several scleroderma target autoantigens. TSK mouse syndrome is associated with a mutation in fibrillin-1 (Fbn-1), the major component of 10 nm microfibrils. Here, we have investigated whether TSK mouse develops autoimmunity to Fbn-1 similar to scleroderma target autoantigens. Our results show that anti-Fbn-1 IgG autoantibodies are present in high titer in many TSK mice. Specificity of these antibodies was confirmed by competitive inhibition assays and Western blotting analysis using recombinant human Fbn-1 protein. TSK mouse autoantibodies recognize a conserved epitope present in the C region of Fbn-1. These results indicate the presence of Fbn-1 specific T and B cells in TSK mouse repertoire.

Transcriptional activation of the alpha1(I) procollagen gene and up-regulation of alpha1(I) and alpha1(III) procollagen messenger RNA in dermal fibroblasts from tight skin 2 mice

OBJECTIVE

To investigate the levels of expression of type I and type III collagen genes in dermal fibroblasts from tight skin 2 (Tsk2) and normal mice and to examine the transcriptional regulation of the alpha1(I) procollagen gene (COL1A1) in these cells.

METHODS

Dermal fibroblasts from Tsk2 mice and from normal age- and sex-matched control mice were studied. Steady-state levels of alpha1(I) and alpha1(III) procollagen messenger RNA (mRNA) were evaluated by Northern and dot-blot hybridization analyses. The transcriptional regulation of COL1A1 was examined by transient transfection experiments with deletion constructs containing portions of the COL1A1 promoter ligated to the chloramphenicol acetyltransferase reporter gene. To identify DNA binding proteins that interact with regulatory elements within the COL1A1 promoter, gel mobility shift assays were performed with nuclear extracts prepared from normal and Tsk2 dermal fibroblasts.

RESULTS

Synthesis of collagen was almost 100% higher in Tsk2 dermal fibroblasts than in control fibroblasts. Up-regulation of mRNA for 2 extracellular matrix proteins was observed in the Tsk2 dermal fibroblasts compared with the normal cells: the alpha1(I) procollagen mRNA steady-state levels were 50% higher, and those of the alpha1(III) procollagen mRNA 100% higher, in Tsk2 cells. The results of transient transfection experiments with COL1A1 promoter constructs demonstrated that the elevated levels of alpha1(I) collagen mRNA in Tsk2 cells were largely due to increased transcriptional activity of the corresponding gene. Electrophoretic mobility shift assays performed with a probe encompassing a relevant COL1A1 promoter region revealed increased DNA-protein binding activities in nuclear extracts prepared from Tsk2 fibroblasts compared with normal fibroblasts. Competition experiments using consensus Spl and nuclear factor 1 (NF-1) oligonucleotides and supershift experiments using anti-Sp1 and anti-NF-1 antibodies indicated that at least 2 transcription factors, Sp1 and NF-1, or their homologs are involved in the up-regulated transcriptional activity of the COL1A1 promoter in Tsk2 fibroblasts.

CONCLUSION

Dermal fibroblasts from Tsk2 mice display increased collagen synthesis and up-regulation of alpha1(I) and alpha1(III) procollagen mRNA in vitro. The data also directly demonstrate the transcriptional activation of COL1A1 in dermal fibroblasts from Tsk2 mice and suggest that the transcription factors Sp1 and NF-1 or their homologs play an important role in the upregulated expression of this gene in Tsk2 fibroblasts. These findings are similar to those described for fibroblasts from humans with systemic sclerosis and validate the use of Tsk2 as a model for the study of the connective tissue alterations in this disease.

The Tight skin mouse: demonstration of mutant fibrillin-1 production and assembly into abnormal microfibrils

Mice carrying the Tight skin (Tsk) mutation harbor a genomic duplication within the fibrillin-1 (Fbn 1) gene that results in a larger than normal in-frame Fbn 1 transcript. In this study, the consequences of the Tsk mutation for fibrillin-containing microfibrils have been examined. Dermal fibroblasts from Tsk/+ mice synthesized and secreted both normal fibrillin (approximately 330 kD) and the mutant oversized Tsk fibrillin-1 (approximately 450 kD) in comparable amounts, and Tsk fibrillin-1 was stably incorporated into cell layers. Immunohistochemical and ultrastructural analyses of normal and Tsk/+ mouse skin highlighted differences in the gross organization and distribution of microfibrillar arrays. Rotary shadowing of high Mr preparations from Tsk/+ skin demonstrated the presence of abundant beaded microfibrils. Some of these had normal morphology and periodicity, but others were distinguished by diffuse interbeads, longer periodicity, and tendency to aggregate. The presence of a structurally abnormal population of microfibrils in Tsk/+ skin was unequivocally demonstrated after calcium chelation and in denaturating conditions. Scanning transmission electron microscopy highlighted the presence of more mass in Tsk/+ skin microfibrils than in normal mice skin microfibrils. These data indicate that Tsk fibrillin-1 polymerizes and becomes incorporated into a discrete population of beaded microfibrils with altered molecular organization.

Apoptosis and proliferation of fibroblasts during postnatal skin development and scleroderma in the tight-skin mouse

Tight-skin (Tsk) is a dominant gene mutation that causes a fibrotic skin disease in mice, similar to human scleroderma. Both conditions are characterized by increased numbers of dermal fibroblasts containing high levels of procollagen mRNA. Whether this fibroblast population arises from fibroblast growth or fibroblast transcriptional activation is debated. Proliferation and apoptosis of fibroblasts of normal and Tsk mice were studied in skin sections before, at onset, and in established fibrosis. Tissues sections were immunostained with proliferating cell nuclear antigen (PCNA) as proliferation marker. Apoptosis was investigated by in situ end-labeling of fragmented DNA and nuclear staining with propidium iodide. The expression of the apoptosis inhibitor Bcl-2 was investigated by immunohistochemistry. We demonstrate differences in fibroblast proliferation and apoptosis related to postnatal skin growth and development. Neonatal skin exhibits the highest levels of proliferation and apoptosis in fibroblasts. In contrast, low proliferation and absence of apoptosis characterizes adult fibroblasts. Skin fibroblasts express Bcl-2 only in newborns, and at other ages Bcl-2 was restricted to epithelial cells. Our results also suggest that neither increased fibroblast proliferation nor defective apoptosis accounts for the fibrotic phenotype of Tsk. Therefore, transcriptional activation of extracellular matrix genes appears more relevant in the pathogenesis of Tsk fibrosis.

Morphological and biochemical studies of the elastic fibres in the craniomandibular joint articular disc of the tight-skin mouse

The tight-skin (TSK) mouse is characterized by the hyperplasia of loose connective tissues, and of excessive growth of cartilage and of bones including the mandible. Since the fibroelastic connective tissues of the craniomandibular joint (CMJ) are essential to the functions of this joint, the present histological study compared the presence and general distribution of elastic fibres in CMJ discal tissues of TSK and normal mice. The excised CMJs were processed for light microscopy. The tissues were fixed, demineralized, embedded in paraffin, sectioned and then stained with resorcin-fuchsin to demonstrate elastic fibres. There were no obvious histological differences in either the amount or the distribution of elastic fibres in the discs from the two groups. In both groups, elastic fibres were found in the disc and in many of the attachments of the disc to the mandible and squamosal bone. In addition to the morphological preparations, articular discs and samples of lung tissue were excised from other mice and subjected to a radioimmunoassay for desmosine in order to estimate the amounts of elastin in these tissues; the amount of elastin was significantly reduced in the TSK lung, but the amounts of elastin in the TSK and normal CMJ discal tissues were not significantly different statistically. These morphological and histochemical results suggest that the distribution and quantity of elastic fibres in the TSK mouse disc are not significantly different from those in the normal mouse articular disc. Moreover, these data may be interpreted to either suggest a differential effect on the elastic fibres in different TSK tissues, or to support the suggestion that abnormal degradation of elastic fibres may not be characteristic of the TSK mouse.

Inhibition of collagen synthesis and changes in skin morphology in murine graft-versus-host disease and tight skin mice: effect of halofuginone

The effect of halofuginone, a plant alkaloid known to inhibit collagen type I synthesis, on skin collagen content and skin morphology was evaluated in two in vivo models of scleroderma: the murine chronic graft-versus-host disease (cGvHD) and the tight skin mouse. Skin collagen was assessed by hydroxyproline levels in skin biopsies and by immunohistochemistry using anti-collagen type I antibodies. Daily intraperitoneal injections of halofuginone (1 microgram/mouse) for 52 d starting 3 d before spleen cell transplantation, abrogated the increase in skin collagen and prevented the thickening of the dermis and the loss of the subdermal fat, all of which are characteristic of the cGvHD mice. Halofuginone had a minimal effect on collagen content of the control mice. The halofuginone-dependent decrease in skin collagen content was concentration-dependent and was not accompanied by changes in body weight in either the cGvHD or the control mice. Injections of halofuginone (1 microgram/mouse) for 45 d caused a decrease in the collagen content and dermis width in tight skin mice, but did not affect the dermis width of control mice. Collagen content determination from skin biopsies confirmed the immunohistochemical results in the same mice. The low concentration of halofuginone needed to prevent collagen deposition in fibrotic skin without affecting body weight suggests that halofuginone may serve as a novel and promising anti-fibrotic therapy.

The tight skin 2 mouse. An animal model of scleroderma displaying cutaneous fibrosis and mononuclear cell infiltration

OBJECTIVE

To describe the histopathologic and biochemical characteristics of skin from the Tsk2/+ mouse, a mutation with phenotypic features resembling those of systemic sclerosis (SSc), and to report the initial genetic mapping of the Tsk2 locus.

METHODS

Histologic examination was performed and collagen content and type I collagen messenger RNA (mRNA) levels were determined in skin biopsy specimens from Tsk2/+ mice and normal mice. An intersubspecific backcross was conducted as a first step toward identifying the position of the Tsk2 locus on mouse chromosome 1.

RESULTS

Histologic examination of Tsk2/+ mouse skin revealed marked accumulation of collagen and infiltration with mononuclear cells in the dermis and adipose tissue. Biochemical studies of Tsk2/+ mouse skin showed increased collagen content and elevated steady-state levels of alpha 1 (I) procollagen mRNA. Tsk2 was mapped to a 15.3-centimorgan interval on mouse chromosome 1.

CONCLUSION

Tsk2 is a novel mutation which displays histopathologic and biochemical abnormalities similar to those present in the skin of patients with SSc, including increased collagen content and expression of type I collagen genes. This mutation has been mapped to a 15.3-cM region on mouse chromosome 1. Further study of this novel mutation will allow the identification of previously undescribed mechanisms involved in the regulation of normal and pathologic collagen gene expression.

Increased alpha 1(I) procollagen gene expression in tight skin (TSK) mice myocardial fibroblasts is due to a reduced interaction of a negative regulatory sequence with AP-1 transcription factor

The TSK mouse, a model of fibrosis, displays exaggerated connective tissue accumulation in skin and visceral organs including the heart. To study the mechanisms of myocardial fibrosis in TSK mice, we established several strains of TSK mice myocardial fibroblasts in culture and examined the regulation of collagen gene expression in these cells. These strains displayed increased collagen gene expression in comparison with myocardial fibroblasts established from normal mice. On an average, the TSK myocardial fibroblast cultures showed a 4-fold increase in collagen synthesis and 4.4- and 3.6-fold increases, respectively, in alpha 1(I) and alpha 1(III) collagen mRNA steady state levels. The increased alpha 1(I) and alpha 1(III) collagen mRNA levels were mainly due to increased transcription rates (3.4- and 3.8-fold higher, respectively) of the respective genes. Furthermore, we showed that the up-regulation of alpha 1(I) procollagen gene transcription in TSK mice myocardial fibroblasts was due to the lack of the strong inhibitory influence of a regulatory sequence contained in the promoter region encompassing nucleotides -675 to -804. Nuclear extracts from TSK mice myocardial fibroblasts showed lower DNA binding activity to oligonucleotides spanning the mapped regulatory sequence as well as to a consensus AP-1 sequence, but not to a consensus SP-1 sequence, and supershift experiments with an AP-1 antibody confirmed the interaction of these oligonucleotides with AP-1 protein. These observations indicate that a strong negative regulatory sequence contained within -0.675 to -0.804 kilobase of the alpha 1(I) procollagen promoter binds AP-1 transcription factor and mediates inhibition of gene transcription in normal murine myocardial fibroblasts. The TSK mice myocardial fibroblasts lack this inhibitory control, due to lower available amounts and/or decreased binding activity to this inhibitory sequence, and hence display increased alpha 1(I) procollagen gene expression.

Autoantibodies in scleroderma and tightskin mice

There is much evidence to suggest that scleroderma in human patients is caused by a fundamental defect in the immune system. In tightskin mice, the scleroderma syndrome is associated with autoimmunity, particularly autoantibodies interacting with scleroderma target antigens.

TGF beta 1 regulation of collagen metabolism by embryonic palate mesenchymal cells

Proper metabolism of the extracellular matrix (ECM) in mammalian embryonic palatal tissue is required for normal development of the palate. In particular, perturbation of collagen metabolism in the embryonic orofacial region results in the production of cleft palate. Although several types of collagen have been localized in the embryonic palate, factors responsible for regulating their synthesis have not been identified. Transforming growth factor beta (TGF beta), shown to be capable of modulating ECM metabolism in other tissues, has been localized in the developing palate. Thus, we examined the ability of TGF beta 1 to modulate collagen synthesis and degradation in murine embryonic palate mesenchymal (MEPM) cells in vitro. Immunohistochemical analysis confirmed that type III collagen was predominant in the mesenchyme of the embryonic palate, whereas type I collagen was ubiquitous throughout palatal epithelium and mesenchyme. Total collagen production by TGF beta-treated confluent MEPM cells in serum-free conditioned medium was determined by measuring incorporation of L-[2-3-4-5-3H]proline into hydroxyproline. Treatment for 24 hr with TGF beta 1 stimulated incorporation into both cell layer and medium fractions. Quantification of collagen types by ELISA indicated that TGF beta 1 stimulated the accumulation of type III collagen as early as 3 hr after treatment. Northern blot analysis of MEPM cells treated with TGF beta 1 revealed that steady-state levels of mRNA encoding for procollagen alpha 1 (I) and alpha 1 (III) were increased and that these effects were ablated by cycloheximide but not actinomycin. The effects of TGF beta treatment on MEPM cell collagen levels also reflected alterations in collagen degradation. TGF beta-treated MEPM cells exhibited a significant diminution of total protease activity. Moreover, analysis by substrate gel electrophoresis indicated specific decreases in vertebrate collagenase and stromelysin. These data represent the first report of changing proteolytic profiles during palatogenesis. Thus, TGF beta regulates the amount of collagen present in embryonic palatal tissue at the level of synthesis and degradation.

Fibrillin genes map to regions of conserved mouse/human synteny on mouse chromosomes 2 and 18

Fibrillin proteins are major structural components of the 10-nm microfibrils found in elastic and nonelastic connective tissues. Previous studies have mapped the human genes for two fibrillins to chromosome bands 15q21 (FBN1) and 5q23-q31 (FBN2) and have demonstrated that FBN1 mutations are associated with Marfan syndrome, while FBN2 is linked to the gene for congenital contractural arachnodactyly. Here, we report the isolation of genomic clones of the corresponding mouse fibrillin genes (Fbn-1 and Fbn-2). By analyzing a mapping panel of mouse x rodent somatic hybrid cell lines, we have assigned the Fbn-1 gene to mouse chromosome 2 and the Fbn-2 gene to mouse chromosome 18. We then sublocalized the fibrillin genes to bands 2F (Fbn-1) and 18D-E1 (Fbn-2) by fluorescence in situ hybridization. These regions are known to exhibit conserved synteny with the regions on human chromosomes 15 and 5 that carry the homologous human fibrillin genes. In addition, the Fbn-1 gene maps in the vicinity of the gene for a connective tissue disorder on mouse chromosome 2 called Tight-skin (Tsk).

Tight-skin mouse autoantibody repertoire: analysis of VH and VK gene usage

In the previous studies we have shown that tight-skin (TSK) mouse is an experimental model for systemic sclerosis. This mutant mouse develops autoantibodies specific for scleroderma target antigens. To determine whether the expansion of autoantibody repertoire in TSK mouse occurs by selective expansion of certain variable region gene families, and whether CD5+ B cells contribute significantly to the production of autoantibodies, we have analyzed a panel of 60 hybridomas producing autoantibodies specific for scleroderma target autoantigens. Northern analysis of RNAs from these hybridomas showed that 70% were expressing genes from VHJ558 family while genes from 36-09 and J606 families were not at all represented. In contrast, in the cDNA libraries derived from splenic B cells, the expression of VHJ558 and 36-09 gene families were at an expected frequency corresponding to their genomic complexity (44% and 11.6%, respectively). These results demonstrate that there is a strong bias toward the use of J558 genes in TSK mouse autoantibody repertoire. On the other hand the expression of VK gene families was mostly random and corresponded to their frequency in splenic C kappa cDNA library. The pairing of VH:VK genes was stochastic. Analysis of the expression of J segments, however, revealed that JH2 and JK2 were predominantly used in the autoantibodies. Analysis of the expression CD5 mRNA in these hybridomas indicate that CD5+ B cells do not contribute significantly to the autoimmunity in TSK mice. These findings suggest that the expansion of peripheral autoreactive B cells in TSK mouse is determined by their immunoglobulin variable region rather than the genetic properties linked to a particular B cell subset.

The synthetic retinoid (4-hydroxyphenyl)retinamide decreases collagen expression in vitro and in the tight-skin mouse

OBJECTIVE

We documented the effect of the retinoid (4-hydroxyphenyl)retinamide on collagen expression in a tissue culture and in an animal model of scleroderma.

METHODS

We used RNA analysis, chloramphenicol acetyltransferase assays, organ culture, and histologic evaluation.

RESULTS

We showed that (4-hydroxyphenyl)retinamide decreases alpha 1(I) collagen messenger RNA and transcription in cultured cells, and decreases collagen levels in the dermis of tight-skin mice.

CONCLUSION

These results provide a basis for further experiments to address the efficacy of (4-hydroxyphenyl)retinamide in the treatment of scleroderma.

Granulated metrial gland cells: a natural killer cell subset of the pregnant murine uterus

The metrial gland develops in the uterus of many rodent species during normal pregnancy. It is a maternally-derived tissue that contains stromal and vascular elements plus a population of large cells, striking in their light microscopic appearance due to the presence of numerous cytoplasmic granules. These cells, which have become known in mice and rats as granulated metrial gland (GMG) cells, are derived from bone marrow precursors and recent work suggests they are a subset of lymphocytes belonging to the natural killer (NK) cell lineage. The functions of GMG cells during normal gestation have not been clearly defined. In vitro, GMG cells have been shown to produce cytokines and their cytokine profile is altered upon addition of medium containing the T cell growth factor interleukin-2 (IL-2). GMG cell granules contain the cytolytic protein perforin but GMG cells have a very limited capacity to kill in vitro unless they have been stimulated by IL-2 or interferon-gamma. Histological study of GMG cells has suggested they preferentially associate with fetal trophoblast. Since trophoblast appears resistant to immune lysis, except by IL-2-activated effector lymphocytes, and because resorbing murine embryos become infiltrated by lytic cells of the NK cell lineage, it is important to establish whether GMG cells are activated by pregnancy-associated events to play a major lytic role in vivo.

Quantification of ventricular remodeling in the tight-skin mouse cardiomyopathy with acoustic microscopy

To determine the role of ultrasonic tissue characterization for the detection of changes in myocardial architecture associated with cardiomyopathy, acoustic microscopy was performed on the hearts of 4- to 6-month-old tight-skin mice [TSK/+, C57-B10.D2 (58B)/SN strain], a model of cardiomyopathy characterized by diffuse interstitial fibrosis. Ultrasonic backscatter was measured from excised segments of left ventricular free walls of five TSK mice and five sex- and age-matched normal controls with a 50 MHz broad band focused piezoelectric transducer operated in a saline-filled water tank at room temperature. Forty-nine radio frequency (RF) lines were digitized from each specimen at 2 ns/sample. Power spectral analysis of RF data was performed and mean integrated backscatter (IB) computed. The TSK group demonstrated greater IB (-53.6 +/- 0.6 dB, n = 5) than did the control group (-56.6 +/- 0.7 dB, n = 5; p < 0.02). Myocardial collagen content determined by hydroxyproline assay increased by 11% in the TSK group (2.54 +/- 0.08 microgram/mg dry wt, n = 5) over that in controls (2.28 +/- 0.07 microgram/mg dry wt, n = 5; p < 0.05). A significant linear relationship was observed between myocardial hydroxyproline concentration and IB (r = 0.74; p < 0.02). Thus, ultrasonic tissue characterization permits sensitive detection of modest changes in the extent of interstitial fibrosis that accompany tissue remodeling in the early stages of cardiomyopathy.

Self-reactive repertoire of tight skin (TSK/+) mouse: immunochemical and molecular characterization of anti-cellular autoantibodies

The tight skin (TSK/+) mouse has been proposed as an experimental model for progressive systemic sclerosis because of the biochemical alterations in collagen synthesis and pathological similarities to the human disease. Here, we report the analysis of tight skin mice sera for the presence of anti-cytoplasmic and anti-nuclear autoantibodies and determination of the frequency of hybridomas producing anti-cellular autoantibodies. The binding specificity of TSK mAbs to nuclear and cytoplasmic antigens such as keratin, actin, vimentin, and mitochondria was determined. Of 71 monoclonal antibodies that we have studied, only 3 appear to bind to foreign as well as self-antigens, indicating that the majority of these antibodies do not belong to the class of natural autoantibodies. Our results also showed that the frequency of hybridomas producing anti-nuclear and anti-cytoplasmic antibodies was higher in TSK mice than in C57BL/6 pa/pa, the control mouse strain, used in these studies. The results of the analysis of V gene usage showed that the majority of anti-cytoplasmic and anti-nuclear antibodies are encoded by genes from a restricted number of VH and VK genes families. In the sera of TSK mice we have detected the presence autoantibodies specific for cytoplasmic antigens in addition to anti-nuclear and anti-topoisomerase I antibodies which are characteristic of scleroderma. Since the presence of anti-cytoplasmic antibodies has not been described in scleroderma, the significance of their production in tight skin mice is not clear. However, the presence of such autoantibodies in the animal model provides a basis for investigation of this type of antibodies in human disease.

Granulated metrial gland cells in the pregnant uterus of mice expressing the collagen mutation tight-skin (Tsk/+)

Influences of the extracellular matrix (ECM) on the differentiation and distribution of granulated metrial gland (GMG) cells, a uterine natural killer (NK)-like cell subset, were studied by histological examination of implantation sites in the mouse mutant Tsk/+. Tsk/+ mice overproduce collagens I and III. GMG cell differentiation appeared to progress normally in Tsk/+ mice between days 6.5 and 12.5 of gestation. The distribution of GMG cells, however, was abnormal. Significant numbers of GMG cells were found in the antimesometrial and lateral decidual regions at day 8.5 of gestation and in the regions between implantation sites until day 10.5 of gestation. Loss of GMG cells from these regions normally occurs by day 6.5 of gestation. These data suggest that alterations to the ECM change the migration properties or life span of GMG cells.