A syndrome resembling human systemic sclerosis (scleroderma) in MRL/lpr mice lacking interferon-gamma (IFN-gamma) receptor (MRL/lprgammaR-/-)

Mesenchymal stem cells in fibrotic diseases-the two sides of the same coin

Fibrosis is caused by extensive deposition of extracellular matrix (ECM) components, which play a crucial role in injury repair. Fibrosis attributes to ~45% of all deaths worldwide. The molecular pathology of different fibrotic diseases varies, and a number of bioactive factors are involved in the pathogenic process. Mesenchymal stem cells (MSCs) are a type of multipotent stem cells that have promising therapeutic effects in the treatment of different diseases. Current updates of fibrotic pathogenesis reveal that residential MSCs may differentiate into myofibroblasts which lead to the fibrosis development. However, preclinical and clinical trials with autologous or allogeneic MSCs infusion demonstrate that MSCs can relieve the fibrotic diseases by modulating inflammation, regenerating damaged tissues, remodeling the ECMs, and modulating the death of stressed cells after implantation. A variety of animal models were developed to study the mechanisms behind different fibrotic tissues and test the preclinical efficacy of MSC therapy in these diseases. Furthermore, MSCs have been used for treating liver cirrhosis and pulmonary fibrosis patients in several clinical trials, leading to satisfactory clinical efficacy without severe adverse events. This review discusses the two opposite roles of residential MSCs and external MSCs in fibrotic diseases, and summarizes the current perspective of therapeutic mechanism of MSCs in fibrosis, through both laboratory study and clinical trials.

Animal Models of Systemic Sclerosis: Using Nailfold Capillaroscopy as a Potential Tool to Evaluate Microcirculation and Microangiopathy: A Narrative Review

Systemic sclerosis (SSc) is an autoimmune disease with three pathogenic hallmarks, i.e., inflammation, vasculopathy, and fibrosis. A wide plethora of animal models have been developed to address the complex pathophysiology and for the development of possible anti-fibrotic treatments. However, no current model comprises all three pathological mechanisms of the disease. To highlight the lack of a complete model, a review of some of the most widely used animal models for SSc was performed. In addition, to date, no model has accomplished the recreation of primary or secondary Raynaud’s phenomenon, a key feature in SSc. In humans, nailfold capillaroscopy (NFC) has been used to evaluate secondary Raynaud’s phenomenon and microvasculature changes in SSc. Being a non-invasive technique, it is widely used both in clinical studies and as a tool for clinical evaluation. Because of this, its potential use in animal models has been neglected. We evaluated NFC in guinea pigs to investigate the possibility of applying this technique to study microcirculation in the nailfold of animal models and in the future, development of an animal model for Raynaud’s phenomenon. The applications are not only to elucidate the pathophysiological mechanisms of vasculopathy but can also be used in the development of novel treatment options.

Improving translational research in sex-specific effects of comorbidities and risk factors in ischaemic heart disease and cardioprotection: position paper and recommendations of the ESC Working Group on Cellular Biology of the Heart

Ischaemic heart disease (IHD) is a complex disorder and a leading cause of death and morbidity in both men and women. Sex, however, affects several aspects of IHD, including pathophysiology, incidence, clinical presentation, diagnosis as well as treatment and outcome. Several diseases or risk factors frequently associated with IHD can modify cellular signalling cascades, thus affecting ischaemia/reperfusion injury as well as responses to cardioprotective interventions. Importantly, the prevalence and impact of risk factors and several comorbidities differ between males and females, and their effects on IHD development and prognosis might differ according to sex. The cellular and molecular mechanisms underlying these differences are still poorly understood, and their identification might have important translational implications in the prediction or prevention of risk of IHD in men and women. Despite this, most experimental studies on IHD are still undertaken in animal models in the absence of risk factors and comorbidities, and assessment of potential sex-specific differences are largely missing. This ESC WG Position Paper will discuss: (i) the importance of sex as a biological variable in cardiovascular research, (ii) major biological mechanisms underlying sex-related differences relevant to IHD risk factors and comorbidities, (iii) prospects and pitfalls of preclinical models to investigate these associations, and finally (iv) will provide recommendations to guide future research. Although gender differences also affect IHD risk in the clinical setting, they will not be discussed in detail here.

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.

The role of B cells in systemic sclerosis

Systemic sclerosis (SSc) is a connective disease characterized by features of autoimmunity, vasculopathy, inflammation, and fibrosis. The disease typically starts with Raynaud's phenomenon, followed by skin thickening in the extremities due to inflammation and fibrosis. Fibrosis results from excessive collagen production by fibroblasts, which constitutes the final common pathway of complex cellular interactions including B cells. Several studies have indicated that B cells may play a role in SSc. Lesional skin infiltrates from SSc patients consist of a variety of cells, including eosinophils, neutrophils, lymphocytes, plasma cells, and macrophages. Autoantibodies of several specificities are present in the serum of SSc patients of which antitopoisomerase 1 is the most common, and evidence has been gathered for a potential pathogenic role of some autoantibodies, eg, anti-PDGF antibodies. The blood of SSc patients contains an increased proportion of naïve B cells but a decreased proportion of memory B cells. Furthermore, serum levels of interleukin-6, an important pro-inflammatory cytokine, have been shown to correlate with skin fibrosis. Animal models of SSc have provided more in-depth information on the role of B lymphocytes, eg, through disruption of B cell function. In this review we will discuss the evidence that B cells are involved in the pathogenesis of SSc.

The pathology of scleroderma vascular disease

Systemic sclerosis is characterized by three distinct pathologic processes: fibrosis, cellular/humoral autoimmunity, and specific vascular changes. Although a mild vasculitis may sometimes be present, the vascular pathology of scleroderma is not necessarily inflammatory and is best characterized as a vasculopathy. In this article, the authors propose that SSc vasculopathy is the result of an early event involving vascular injury that eventuates in a vicious cycle mediated in part by the immune process. The subsequent vascular malformation and rarefaction may be a function of systemic angiogenic dysregulation, with over expression of vascular endothelial growth factor but a lack of proper interactions with smooth muscle cells needed to stabilize and organize blood vessels.

Gender and autoimmunity

The enhanced immunoreactivity in females is a double-edged sword that provides better protection against infections, but may lead to enhanced autoreactivity and thereby contribute to the induction of autoimmunity. Autoimmune diseases demonstrate a gender bias and represent the fifth leading cause of death by disease among females of reproductive age. Clinical and murine experimental studies indicate that the gender bias in autoimmunity may be influenced by sex hormones, predominantly displayed in the development and exacerbations of the prototypical autoimmune disease lupus. The associations between sex hormones and other autoimmune diseases are less clear. Our review on the impact of gender via sex hormones and sex related genes in the pathogenesis of several autoimmune diseases suggests that a better understanding of the underlying mechanisms behind the sexual dimorphism of the immune system may lead to the development of novel therapeutic approaches to autoimmunity.

Facteurs de prédisposition génétiques à la fibrose au cours de la sclérodermie systémique

PURPOSE

Physiopathology of systemic sclerosis includes autoimmunity factors, endothelial lesions and abnormal fibrotic process which characterizes this disease in the field of systemic autoimmune disorders. Genetic factors of susceptibility are showed by possibility of familial forms of the disease, Choctaw American Indians homogenous population with high disease prevalence of systemic sclerosis and experimental animal models.

KEY POINTS

We propose a review of the articles published to date in the literature concerning genetical analysis of genes coding for factors potentially involved in the fibrotic process of systemic sclerosis. This includes cytokines (TNF-alpha, interleukin-1, chemokines), growth factors (TGF-beta), extracellular matrix proteins (collagen, fibrillin, fibronectine) and agents acting on vascular tone (angiotensin-converting enzyme and NO synthase).

PERSPECTIVES

Identification of genetic factors involved in the susceptibility to fibrosis of systemic sclerosis would lead to a better understanding of physiopathological mechanisms of this disease and to therapeutic targets using immunomodulation with drugs, such as already performed in rheumatoid arthritis.

Transgenic analysis of scleroderma: understanding key pathogenic events in vivo

Modern molecular genetic methods have allowed better understanding of established mouse models of scleroderma and also facilitated the development of new and better defined mouse strains for investigating the pathogenesis of the disease. The best characterized scleroderma animal model is the type 1 tight skin mouse (Tsk1). Backcrossing these animals with other mutant strains has been informative. These experiments implicate the IL-4 ligand-receptor axis in the development of skin fibrosis. Parallel expression analysis of genes using microarrays has provided insight into novel mediators of fibrosis including the C-C chemokine MCP-3. Other experiments suggest that embryonically defined fibroblast-specific regulatory elements may be targets for activation in this model. The same lineage-specific elements have been used to selectively activate TGF beta signaling pathways in fibrosis to generate a novel model for scleroderma and also have been used to develop systems for ligand-dependent fibroblast-specific genetic recombination that will allow further analysis key candidate genes implicated in scleroderma pathogenesis. Better mouse models will improve understanding of this intractable rheumatic disease and can be expected to ultimately lead to improved treatments and outcome.

A modified model of graft-versus-host-induced systemic sclerosis (scleroderma) exhibits all major aspects of the human disease

OBJECTIVE

Diffuse systemic sclerosis (SSc; scleroderma) is a debilitating disease characterized by excessive dermal fibrosis with later progression to internal organs. In addition to the fibrotic component, major aspects of the disease include vascular or circulatory involvement and immune dysregulation evidenced by inflammatory cells in affected tissues and production of autoantibodies. Many animal models resembling this disease have been studied, including genetic models in mice and chickens, challenge with chemicals such as bleomycin or vinyl chloride to induce fibrosis, and models of graft-versus-host (GVH)-induced disease using certain strains of mice with differences in minor histocompatibility loci. The present studies were undertaken to determine if alteration of the induction of GVH-induced scleroderma could result in a model that more fully represented the human condition.

METHODS

Disease was induced by injection of spleen cells from B10.D2 mice into BALB/c mice deficient in mature T and B cells (recombination-activating gene 2 targeted). Dermal thickening, collagen deposition, vasoconstriction, and parameters of immunity were analyzed.

RESULTS

Similar to the human disease, this modified GVH model of SSc demonstrated evidence of dermal thickening, particularly in the extremities, progressive fibrosis of internal organs, vasoconstriction and altered expression of vascularity markers in skin and internal organs, early immune activation, inflammation in skin and internal organs, and autoantibody generation.

CONCLUSION

This modified model of GVH-induced SSc exhibits all major components of human disease and is likely to contribute to better understanding of the disease mechanisms and, ultimately, improved treatments for patients.

Use of localised gene transfer to develop new treatment strategies for the salivary component of Sjögren's syndrome

Effective treatment for Sjögren's syndrome (SS) might be developed locally by introducing genes encoding cytokines, which are potentially anti-inflammatory, or by introducing a cDNA encoding a soluble form of a key cytokine receptor, which can act as an antagonist and decrease the availability of certain cytokines, such as soluble tumour necrosis factor alpha receptors. Currently, the preferred choice of viral vector for immunomodulatory gene transfer is recombinant adeno-associated virus. The use of gene transfer to help determine the pathophysiology and to alter the course of the SS-like disease in the NOD mouse model can ultimately lead to the development of new treatments for managing the salivary component in patients with SS.

Animal models for scleroderma: an update

Scleroderma is a progressive debilitating fibrosing disease that may involve multiple organs. The pathogenesis of this disease remains unclear. Animal models for scleroderma are valuable for studying the pathogenesis of this complex disorder and for testing potential treatments for human scleroderma. There are several animal models available that exhibit important features of scleroderma, each with an emphasis on different aspects of the disease (tissue fibrosis, inflammation, vascular injury, or immunologic changes). These models can be separated into several categories in which fibrosis is induced by external agents (vinyl chloride, bleomycin), by breeding of mutant strain combinations (integrin alpha 1 null mouse, MRL/lpr gamma R-/- mouse), and by transplantation of disparate immune cells (sclerodermatous graft versus host disease). In addition, there are spontaneous mutations (UCD 200 chicken, tight skin mouse) in which fibrosis occurs. The tight skin mouse has been reviewed recently. This review discusses the other animal models and some interventions in each.

Pathology of "toxic oils" and selected metals in the MRL/lpr mouse

The Toxic Oil Syndrome epidemic that occurred in Spain in 1981 and affected nearly 20,000 people was caused by ingestion of oil mixtures that contained analine-denatured rapeseed oil. To date, an animal model in which to identify the actual etiologic agents(s) and to investigate the pathogenesis of the disease has not been discovered. In this study, the MRL/lpr was used to assess the histopathological response of 3 "toxic oils" and 3 metals. The oils tested were a denatured rapeseed oil collected from a family who were affected by the Toxic Oil Syndrome epidemic in Spain (CO756) plus two synthesized oils (RSD and RSA). Female mice, 7 weeks of age, received an undiluted (neat) or a 1:10 diluted dose of each oil; mercury (50 ppm), cadmium (100 ppm), or lead (50 ppm). Half of each group was killed after 5 weeks of exposure and the remaining mice after 10 weeks of exposure. Body and organ weights (liver, kidney, thymus, and spleen) were recorded and selected organs were collected for histopathology. Ten weeks after treatment, body weights (BW) of the cadmium and lead groups were significantly suppressed, and the body weight of the C0756-neat group was significantly increased compared to their respective controls. Kidney/BW were decreased in the RSA-neat and RSA 1:10 groups after 10 weeks of exposure, and the kidney/BW in the mercury and cadmium groups were increased. Spontaneous development (12 weeks of age) and progression (17 weeks of age) of histopathological lesions are described for selected organs examined in the naïve mice as are changes that resulted from exposure to the "toxic oils" and metals. C0756-neat, mercury, and lead suppressed progression of the glomerulonephritis that normally occurs in the MRL/lpr mouse. Also of interest were lesions that included mononuclear cuffing of hepatic bile ducts, progression of the granulomas that formed in the renal glomeruli, vessels in the lymphoid organs that contained tightly packed lymphocytes, and the presence of plasma cells in the thymus. All 3 oils stimulated early development of the lymphoproliferative syndrome characteristic of the MRL/lpr mouse as demonstrated by an increase in the thymus/BW and spleen/BW ratios after 5 weeks of treatment. These data contribute to our knowledge of spontaneous disease progression in the thymus, spleen, lymph nodes, and kidneys in the MRL/lpr mouse and the effects of 3 different "toxic oils" and metals on the development and progression of those lesions.

Genetic factors in the etiology of systemic sclerosis and Raynaud phenomenon

There is increasing evidence that genetic factors play important roles in susceptibility to and expression of systemic sclerosis (SSc), as well as primary Raynaud phenomenon. Familial aggregation for SSc, although infrequent (1.2%-1.5% of SSc families), has now been established, and when compared with population prevalence represents a significant risk factor for the disease and lays a firmer foundation for genetics in etiopathogenesis. Major histocompatibility complex class II alleles increase disease risk in some populations but are more strongly correlated with specific autoantibody profiles. Microchimerism influenced by human leukocyte antigen also remains an intriguing hypothesis. A variety of extracellular matrix genes, including fibrillin-1, have become additional candidates for contributing to what is likely a complex genetic disease. Reviewed here is evidence relating to these concepts, especially new data reported over the last year.