Genetic factors in the etiology of systemic sclerosis and Raynaud phenomenon

The association of IL-33 and systemic sclerosis: a systematic review and meta-analysis

A meta-analysis of the association between IL-33 and these diseases is lacking, and we aimed to perform a meta-analysis of the association between IL-33 and systemic sclerosis (SSc). We searched relevant papers through PubMed (via Medline), Embase (via Ovid), and the Cochrane Library through May 18th, 2022. Odds ratios (ORs) and weighted mean differences (WMDs) were estimated using a random effect model. A total of 8 papers were included in our meta-analysis. The pooled results showed that SSc patients had significantly higher serum IL-33 levels than healthy controls (HCs) (SMD = 0.64; 95% CI = 0.34, 0.93; P < 0.001); early SSc patients had significantly higher serum IL-33 levels than late SSc patients (SMD = 1.04; 95% CI = 0.28, 1.80; P = 0.007). However, no significant difference was observed between limited cutaneous SSc and diffuse cutaneous SSc (SMD =  - 0.35; 95% CI =  - 0.76, 0.06; P = 0.094). Our meta-analysis provided important evidence for the use of IL-33 in therapeutic strategies for fibrotic disorders.

Raynaud's Phenomenon: A Brief Review of the Underlying Mechanisms

Raynaud’s phenomenon (RP) is characterized by exaggerated cold-induced vasoconstriction. This augmented vasoconstriction occurs by virtue of a reflex response to cooling via the sympathetic nervous system as well as by local activation of α_2C adrenoceptors (α_2C-AR). In a cold-initiated, mitochondrion-mediated mechanism involving reactive oxygen species and the Rho/ROCK pathway, cytoskeletal rearrangement in vascular smooth muscle cells orchestrates the translocation of α_2C-AR to the cell membrane, where this receptor readily interacts with its ligand. Different parameters are involved in this spatial and functional rescue of α_2C-AR. Of notable relevance is the female hormone, 17β-estradiol, or estrogen. This is consistent with the high prevalence of RP in premenopausal women compared to age-matched males. In addition to dissecting the role of these various players, the contribution of pollution as well as genetic background to the onset and prevalence of RP are also discussed. Different therapeutic approaches employed as treatment modalities for this disease are also highlighted and analyzed. The lack of an appropriate animal model for RP mandates that more efforts be undertaken in order to better understand and eventually treat this disease. Although several lines of treatment are utilized, it is important to note that precaution is often effective in reducing severity or frequency of RP attacks.

Genetics, Epigenetics, and Genomics of Systemic Sclerosis

Systemic sclerosis (SSc) is a complex autoimmune disease that occurs in a genetically susceptible host. Genetic studies performed so far reveal that multiple genetic loci contribute to disease susceptibility in SSc. The purpose of this review is to discuss the current knowledge of genetics in SSc by exploring the observational evidence, the different genetic studies, and their modalities as well as the most relevant genes discovered by these. The importance of gene expression variation and the different mechanisms that govern it, including the recently discovered field of epigenetics, are also explored, with an emphasis on microRNA.

The Pathogenesis of Systemic Sclerosis

Systemic sclerosis is a multisystem disorder with a high associated mortality. The hallmark abnormalities of the disease are in the immune system, vasculature, and connective tissue. Systemic sclerosis occurs in susceptible individuals and is stimulated by initiating events that are poorly understood at present. In order for the disease phenotype to appear there is dysfunction in the homoeostatic mechanisms of immune tolerance, endothelial physiology, and extracellular matrix turnover. The progression of disease is not sequential but requires simultaneous dysfunction in these normal regulatory mechanisms. Better understanding of the interplay of these factors is likely to contribute to improved treatment options.

Human adipose-derived stromal cells for cell-based therapies in the treatment of systemic sclerosis

The present study was designed to evaluate the clinical outcome of cell-based therapy with cultured adipose derived stromal cells (ASCs) for the treatment of cutaneous manifestations in patients affected by systemic sclerosis (SSc). ASCs have an extraordinary developmental plasticity, including the ability to undergo multilineage differentiation and self-renewal. Moreover, ASCs can be easily harvested from small volumes of liposuction aspirate, showing great in vitro viability and proliferation rate. Here we isolated, characterized, and expanded ASCs, assessing both their mesenchymal origin and their capability to differentiate towards the adipogenic, osteogenic, and chondrogenic lineage. We developed an effective method for ASCs transplantation into sclerodermic patients by means of a hyaluronic acid (HA) solution, which allowed us to achieve precise structural modifications. ASCs were isolated from subcutaneous adipose tissue of six sclerodermic patients and cultured in a chemical-defined medium before autologous transplantation to restore skin sequelae. The results indicated that transplantation of a combination of ASCs in HA solution determined a significant improvement in tightening of the skin without complications such as anechoic areas, fat necrosis, or infections, thus suggesting that ASCs are a potentially valuable source of cells for skin therapy in rare diseases such as SSc and generally in skin disorders.

The pathogenesis of systemic sclerosis revisited

Although infectiological stimuli, environmental factors and genotypic features are known to contribute to the initiation and perpetuation of systemic sclerosis (SSc), its etiology still remains to be enigmatic, and less elusive insights are to be achieved by ongoing and future investigations. Being characterized, however, as chronic autoimmune disease with excessive collagen accumulation in skin, synovia and visceral organs such as lung, heart, and digestive tract along with obliterating angiopathy, the pathophysiology of SSc can be summarized as being based on imbalances of the cellular and humoral immune system, vascular dysfunction and activation of resident connective tissue cells. A complex interplay between these major components manages to establish and maintain the inability of the vasculature to adequately react to the need for dilatation, constriction and growth of new vessels, to cause the increased deposition of extracellular matrix constituents as well as to facilitate immunological disarrangement. Despite parallels to the chicken and egg causality dilemma, all of these account for what later clinicians observe in patients suffering from Raynaud's phenomenon, digital ulcers, sclerodactyly, rigidity of the face, microstomia, sicca syndrome, dyspnea, dry cough, pulmonary hypertension, palpitations, syncopes, renal insufficiency, dysphagia, gastroesophageal reflux, dyspepsia, generalized arthralgias, but also dyspareunia, or erectile dysfunction.

Fibrosis and immune dysregulation in systemic sclerosis

Autoimmune and inflammatory phenomena are characteristically present in systemic sclerosis (SSc) and impact on dysregulated fibroblast extracellular matrix deposition, hallmark of the disease in conjunction with fibroproliferative vasculopathy. Oligoclonal T helper 2-like cells are present in the skin and peripheral blood in early diffuse disease. Type 2 cytokines synergize with profibrotic cytokines including transforming growth factor beta, favoring collagen deposition and metalloproteinase inhibition by fibroblasts. Furthermore, chemokine with pro-fibrotic and pro-angiogenic properties are preferentially produced by fibroblasts under the influence of Th2-like cells. The profibrotic monocyte chemotactic protein 1 is also produced by fibroblasts, partially in response to Toll-like receptor 4 (TLR4) recognition, when autoantibodies (autoAb) bind to fibroblast surface. In addition, immune-complex formed by autoAb and ubiquitous antigens including topoisomerase-1 favor the production of interferon-alpha (IFN-α) possibly by interacting with intravesicular TLRs. Consistent with this findings, unbiased gene screening has revealed that SSc peripheral blood cells express genes induced by IFN-α, a characteristic shared with systemic lupus erythematosus and other autoimmune disorders. These findings highlight the complex relationship between adaptive and acquired immune responses, which may participate to the pathogenesis of SSc in manners until now unsuspected, which may help in identifying novel therapeutic targets.

What epidemiology has told us about risk factors and aetiopathogenesis in rheumatic diseases

This article will review how epidemiological studies have advanced our knowledge of both genetic and environmental risk factors for rheumatic diseases over the past decade. The major rheumatic diseases, including rheumatoid arthritis, juvenile idiopathic arthritis, psoriatic arthritis, ankylosing spondylitis, systemic lupus erythematosus, scleroderma, osteoarthritis, gout, and fibromyalgia, and chronic widespread pain, will be covered. Advances discussed will include how a number of large prospective studies have improved our knowledge of risk factors, including diet, obesity, hormones, and smoking. The change from small-scale association studies to genome-wide association studies using gene chips to reveal new genetic risk factors will also be reviewed.

Genetics and genomic studies in scleroderma (systemic sclerosis)

It currently is believed that scleroderma is a complex polygenic disease that occurs in genetically predisposed individuals who have encountered specific environment exposures and/or other stochastic factors. The nature of these genetic determinants and how they interact with environmental factors are areas of active investigation. This article discusses the evidence that supports a strong genetic link to scleroderma. These studies implicate potential pathogenetic mechanisms involved in scleroderma, which, it is hoped, may translate into clinical utility, including determination of disease risk, diagnosis, prognosis, and novel therapeutics.

Incidence and prevalence of systemic sclerosis: a systematic literature review

OBJECTIVES

To determine the incidence and prevalence of systemic sclerosis (SSc) in adults, its epidemiological tendencies over time, and its possible key determinants.

METHODS

We performed a systematic literature review using the keywords "systemic sclerosis," "incidence," "prevalence," and "epidemiology."

RESULTS

We found 32 articles published from 1969 to 2006 in which the prevalence of SSc ranged from 7/million to 489/million and its incidence from 0.6/million/y to 122/million/y. There were many geographical variations: SSc prevalence was higher in the USA (276/million in 1990) and Australia (233/million in 1999) than in Japan and Europe, where a north-south gradient was also observed (France: 158/million in 2001 and England: 88/million in 2000). In some regions (Ontario, Rome, near London's airports) there was an unusually high number of SSc cases (3, 5, or 1000 times greater than expected), suggesting spatiotemporal clustering, although no key determinants could be identified. Furthermore, there seemed to be a trend toward an increase in the incidence of SSc over time, but this tendency is uncertain due to lack of uniformity in study methods and designs. We also found that susceptibility to the disease differed according to sex, age, and race.

CONCLUSION

Uniform clinico-epidemiological studies with standard diagnostic and classification criteria are needed to refine the epidemiological features of SSc. Homogeneous study methods with exhaustive case ascertainment as seen in a "capture-recapture" analysis will also be necessary to obtain reliable data.

Mechanisms of Raynaud's disease

Raynaud's phenomenon is due to transient cessation of blood flow to the digits of the hands or feet. An attack of Raynaud's phenomenon is classically manifested as triphasic color changes. The white phase is due to excessive vasoconstriction and cessation of regional blood flow. This phase is followed by a cyanotic phase, as the residual blood in the finger desaturates. The red phase is due to hyperemia as the attack subsides and blood flow is restored. An attack is frequently associated with pain and/or paresthesia due to sensory nerve ischemia. Variants of Raynaud's phenomenon include acrocyanosis and primary livedo reticularis, each of which is associated with reduced skin blood flow, exacerbated by cold or emotional upset. Raynaud's phenomenon in the absence of other disorders is primary Raynaud's phenomenon, or Raynaud's disease. The mechanisms of Raynaud's disease include increased activation of the sympathetic nerves, in response to cold or emotion; an impaired habituation of the cardiovascular response to stress may contribute. In addition, there appears to be a local fault, which is likely multifactorial. This local fault is due to an alteration in vascular function rather than vascular structure. The alteration in vascular function may be related to increased sensitivity to cold of the adrenergic receptors on the digital artery vascular smooth muscle. In some cases, locally released or systemically circulating vasoconstrictors may participate, including endothelin, 5-hydroxytryptamine and thromboxane. A deficiency or increased degradation of nitric oxide, possibly due to increased oxidative stress, may be involved in some cases. These recent pathophysiological insights may lead to new therapeutic options.

Aspects héréditaires et génétiques de la maladie de Raynaud

The pathophysiology of primary Raynaud's phenomenon (Raynaud's disease) remains uncertain but the transmission of this primary microcirculatory dysregulation seems strongly influenced by genetic factors. For a long time, physicians have found that the hereditary factor plays an important role in the genesis of Raynaud's disease. Familial analysis and twin studies have confirmed the role of an hereditary factor. It seems heterogeneous but pedigree analysis indicates the possibility of an autosomal dominant transmission influenced by sex, in some families, allowing an approach called "reverse genetic" based on linkage analysis. Such an approach has focused on few loci but sequencing of candidate genes for genetic mutations remains negative. Given the supposed heterogeneity of the genetic transmission of Raynaud's disease, diversification of strategies in molecular genetics is suitable with reference to techniques applied to multifactorial heredity.

Transforming growth factor-beta1 polymorphisms in Korean patients with systemic sclerosis

Transforming growth factor-beta1 (TGF-beta1) plays an important role in the pathogenesis of systemic sclerosis (SSc). To investigate the role of TGF-beta1 gene polymorphisms in SSc, we genotyped six biallelic polymorphic positions (position -988, -800, and -509; and codons 10, 25, and 263) in 61 Korean SSc patients and in 148 healthy controls, using polymerase chain reaction-sequence-specific primers. Genetic polymorphisms were found at position -509 and codon 10 in Koreans. The allele frequencies of C/T at position -509 were 0.59/0.41 in patients and 0.56/0.44 in controls. The allele frequencies of C/T at codon 10 were 0.40/0.60 in patients and 0.50/0.50 in controls. In conclusion, no skewed distribution of TGF-beta1 gene polymorphisms was found in Korean patients with SSc.

Systemic sclerosis: the susceptible host (genetics and environment)

It is becoming evident that several genetic factors participate in modulating susceptibility to SSc and its clinical manifestations. Some genes that specifically affect ECM metabolism and vascular function may be unique to SSc and scleroderma-related disorders; others, such as those genes involved in regulating immune tolerance, are likely shared with other autoimmune diseases. The effect of genetic variations (or polymorphisms) that are found in most of these genes taken individually will likely have only a small or modest effect on disease risk; only a few genetic variations are expected to be highly penetrant. Moreover, genetic studies in SSc have to deal with the additional issues of heterogeneous phenotypes, low disease prevalence in the general population, and an even greater paucity of multiplex families that makes traditional linkage studies difficult, if not impossible. Alternative approaches include allelic association studies, but conventional case-controls designs may be subject to selection bias and will require large sample sizes if the genes that are under investigation confer only modest (OR = 1.5-2.0) disease risk (Fig. 2). The simultaneous examination of several genes that are biologically relevant to a specific disease process to attain higher aggregate ORs, is one approach that was used in several reports that were cited in this review. The use of family-based controls, such as in the transmission-disequilibrium test (based on assessment of the transmitted or nontransmitted alleles that are associated with disease from heterozygous parents to affected offspring), would provide more robustness to spurious associations from population stratification, but is actually less powerful and efficient than case-control designs. Furthermore, for many late adult-onset diseases the effort required to obtain samples from living parents are for a variety of reasons not trivial. The success of these allelic association-based approaches depends on the identification of likely candidate disease genes (or at least markers in disequilibrium with disease genes), careful definition/ascertainment of disease phenotypes to minimize genetic heterogeneity, and for case-control designs, strategies to account for population stratification or admixture. The identification of candidate genes will be aided by rapid progress in the Human Genome Project and other genome efforts that will eventually identify all human genetic variations. Although this will lead to better understanding of the genes that might be involved in complex diseases, much work is required to understand the basic biology of how disease genotypes become clinical phenotypes. This is especially daunting in complex diseases, such as SSc, where the phenotype (including disease susceptibility and clinical presentation) is influenced by dynamic interactions between genetic variations and environment. Multi-center collaborative efforts with research paradigms that integrate genetic and environmental factors (including sociodemographic variables) will be required to elucidate the contribution of environment and genetics in the pathogenesis of SSc.

Enhanced frequency of a PTPRC (CD45) exon A mutation (77C-->G) in systemic sclerosis

A point mutation in exon A (C to G transversion at position 77) of human PTPRC (CD45) has recently been associated with the development of multiple sclerosis (MS) for at least a subgroup of patients. In the present report, we studied the frequency of the 77C-->G transversion in two other autoimmune diseases namely systemic sclerosis (SSc) and systemic lupus erythematosus (SLE). The mutation was found with significantly enhanced frequency in patients suffering from SSc suggesting that PTPRC could play a role as susceptibility gene not only in MS but also in other autoimmune diseases. Further understanding of the mode of interaction of mutant PTPRC with other susceptibility genes may uncover mechanisms common in various autoimmune disorders.

Systemic sclerosis

Systemic sclerosis (SSc) presents with a great deal of variability from patient to patient and classification and subset criteria will be analysed and discussed. SSc has been reported in people from all over the world. The prevalence and incidence, however, varies from country to country and within the same country in different ethnic groups. These differences will be elucidated. Genetic and environmental factors associated with the disease will be discussed.SSc is predominantly a female disease, with the female:male ratio ranging from 3:1 to 8:1 and being higher in childbearing years. Progenitor cells acquired during pregnancy have been suggested to play a role by inducing a graft-versus-host disease (microchimerism). Recent epidemiological studies on the relationship between SSc and previous pregnancies will be discussed. SSc is associated with a significant morbidity and mortality. Survival has improved in the last 15 years. Factors associated with such improvement will be analysed.

The genetics of systemic sclerosis

The etiopathogenesis of systemic sclerosis (SSc) is unclear. With no definitive evidence supporting an environmental cause, recent attention has focused on genetic factors. Familial clustering and ethnic influences have been demonstrated. Human leukocyte antigen (HLA) associations exist but are more related to the presence of particular autoantibodies rather than to the disease. In addition, no single major histocompatibility complex (MHC) allele predisposes to SSc in all ethnic groups. The role of microchimerism in SSc is a novel yet unproven hypothesis that may be related to intergenerational HLA compatibility. Recent studies investigating polymorphisms in genes coding for extracellular matrix proteins and cell-signaling molecules implicate non-MHC areas in SSc pathogenesis. The data reviewed suggest that SSc is a multigenic complex disorder.

Genetic epidemiology: systemic sclerosis

Systemic sclerosis (SSc) is a multisystem connective tissue disease characterised phenotypically by fibrosis and ischaemic atrophy. Its aetiology is most likely multifactorial. A genetic predisposition to the condition is suggested by reports of familial SSc (a positive family history is the strongest risk factor yet identified), by animal models, and by disease-association studies, in which researchers have examined a wide variety of genes including those involved in fibrosis, in vascular function and structure, and in autoimmunity - the relative rarity of SSc has precluded linkage studies, except in the Choctaw Indians. Recent advances in genetic methodologies should further our understanding of this complex disease process.

Inflammatory myopathy associated with mixed connective tissue disease and scleroderma renal crisis

Mixed connective tissue disease is a rheumatological syndrome with neuromuscular manifestations that may include inflammatory myopathy and carpal tunnel syndrome. We report a patient who presented with an inflammatory myopathy and bilateral carpal tunnel syndrome prior to the diagnosis of a connective tissue disorder. Early in the course of treatment, a syndrome of acute renal failure developed. Knowledge of this syndrome, scleroderma renal crisis, and its possible relation to corticosteroid treatment is important to clinicians involved in the management of patients with inflammatory myopathies.