Epigenetics of scleroderma: Integrating genetic, ethnic, age, and environmental effects

Prevalence, incidence, and mortality of Raynaud's phenomenon, Sjögren's syndrome and scleroderma: an umbrella review of systematic reviews

Objectives

To comprehensively review systematic reviews of prevalence, incidence, and mortality of Raynaud's, Sjögren's and Scleroderma, and to identify any research gaps.

Methods

An umbrella review of English language systematic reviews was undertaken using PubMed and Embase (OVID) covering the period 2000-2023 (PROSPERO CRD42023434865). The estimate and its corresponding 95% confidence interval were reported when available from each systematic review. The quality of systematic reviews was assessed using the Scottish Intercollegiate Guidelines Network (SIGN) tool. A narrative synthesis was undertaken.

Results

Seventeen systematic reviews were identified, of which 1 was for RP, 5 for Sjögren's and 11 for Scleroderma. There were some high-quality systematic reviews for Sjögren's and mortality of Scleroderma. However, there were only low-quality systematic reviews of prevalence and incidence of RP and Scleroderma. Furthermore, there were no systematic reviews for the mortality of RP. For RP, the pooled prevalence was 4850 per 100 000; pooled annual incidence was 250 per 100 000. For Sjögren's, prevalence was 60-70 per 100 000; annual incidence was 6.92 per 100 000 and the pooled standardized mortality ratio ranged from 1.38 to 1.48. For Scleroderma, pooled prevalence ranged from 17.6 to 23 per 100 000; annual incidence was 1.4 per 100 000; and the pooled standardized mortality ratio ranged from 2.72 to 3.53.

Conclusion

The outcomes of RP were less well described compared with Sjögren's and Scleroderma. There was a lack of high-quality systematic reviews for the prevalence and incidence of RP and Scleroderma. Therefore, further studies and systematic reviews with rigorous case definitions, assessing different ethnic groups are warranted in this area.

Recent Insights into Cellular and Molecular Mechanisms of Defective Angiogenesis in Systemic Sclerosis

In systemic sclerosis (SSc, or scleroderma), defective angiogenesis, clinically manifesting with abnormal capillary architecture and severe capillary reduction, represents a hallmark of early-stage disease, usually preceding the onset of tissue fibrosis, and is caused by several cellular and molecular mechanisms affecting microvascular endothelial cells with different outcomes. Indeed, once damaged, endothelial cells can be dysfunctionally activated, thus becoming unable to undergo angiogenesis and promoting perivascular inflammation. They can also undergo apoptosis, transdifferentiate into profibrotic myofibroblasts, or acquire a senescence-associated secretory phenotype characterized by the release of exosomes and several profibrotic and proinflammatory mediators. In this narrative review, we aimed to give a comprehensive overview of recent studies dealing with the cellular and molecular mechanisms underlying SSc defective angiogenesis and the related endothelial cell dysfunctions, mainly the endothelial-to-mesenchymal transition process. We also discussed potential novel vascular treatment strategies able to restore the angiogenic process and reduce the endothelial-to-mesenchymal transition in this complex disease.

Distinct genome-wide DNA methylation and gene expression signatures in classical monocytes from African American patients with systemic sclerosis

BACKGROUND

Systemic sclerosis (SSc) is a multisystem autoimmune disorder that has an unclear etiology and disproportionately affects women and African Americans. Despite this, African Americans are dramatically underrepresented in SSc research. Additionally, monocytes show heightened activation in SSc and in African Americans relative to European Americans. In this study, we sought to investigate DNA methylation and gene expression patterns in classical monocytes in a health disparity population.

METHODS

Classical monocytes (CD14+ + CD16-) were FACS-isolated from 34 self-reported African American women. Samples from 12 SSc patients and 12 healthy controls were hybridized on MethylationEPIC BeadChip array, while RNA-seq was performed on 16 SSc patients and 18 healthy controls. Analyses were computed to identify differentially methylated CpGs (DMCs), differentially expressed genes (DEGs), and CpGs associated with changes in gene expression (eQTM analysis).

RESULTS

We observed modest DNA methylation and gene expression differences between cases and controls. The genes harboring the top DMCs, the top DEGs, as well as the top eQTM loci were enriched for metabolic processes. Genes involved in immune processes and pathways showed a weak upregulation in the transcriptomic analysis. While many genes were newly identified, several other have been previously reported as differentially methylated or expressed in different blood cells from patients with SSc, supporting for their potential dysregulation in SSc.

CONCLUSIONS

While contrasting with results found in other blood cell types in largely European-descent groups, the results of this study support that variation in DNA methylation and gene expression exists among different cell types and individuals of different genetic, clinical, social, and environmental backgrounds. This finding supports the importance of including diverse, well-characterized patients to understand the different roles of DNA methylation and gene expression variability in the dysregulation of classical monocytes in diverse populations, which might help explaining the health disparities.

Symptomatic fractures in systemic sclerosis: A case-control study

This case-control study analyzed risk factors for symptomatic fractures in a group of 52 patients with systemic sclerosis compared with a group of 104 patients without fractures, matched for sex and age, who were attended at a single systemic sclerosis outpatient clinic from 2010 to 2020. Fractures affected predominantly vertebral (65.4%), rib (13.5%), and hip (7.7%) joints, while the mean age of fracture was 55.3 ± 9.5 years. Age at disease onset, age at diagnosis, disease duration, age at menarche, and age at menopause were similar in both groups, and 58.9% of the patients were menopausal at the time of the fracture. The presence of fractures had a significant association with densitometric osteoporosis (p < 0.001), lower weight (p = 0.032), and bone mineral index (p = 0.044), anti-RNA polymerase III (p = 0.040), use of corticosteroids (p = 0.019), and bisphosphonates (p < 0.001), as well as with densitometric T-scores of lumbar spine (p < 0.001), femoral neck (p = 0.025), and total hip (p = 0.013). Multivariate analysis showed that the variables significantly associated with fractures were high doses of corticosteroids (odds ratio = 4.10; 95% confidence interval = 1.290-13.090; p = 0.017), bisphosphonates (odds ratio = 3.91; 95% confidence interval = 1.699-8.984; p = 0.001), negative anti-Scl70 (OR = 0.34; 95% confidence interval = 0.124-0.943; p = 0.038), and lumbar T-score (odds ratio = 0.39; 95% confidence interval = 0.034-0.460; p = 0.010). In conclusion, symptomatic fractures were associated predominantly with lower bone mineral density of lumbar spine and use of high doses of corticosteroids and bisphosphonates in this cohort.

A positive loop formed by SOX11 and periostin upregulates TGF-β signals leading to skin fibrosis

Systemic sclerosis (SSc) is a chronic, heterogenous disease of connective tissue characterized by organ fibrosis together with vascular injury and autoimmunity. Transforming growth factor (TGF)-β plays a central role in generating fibrosis, including SSc. Periostin is a matricellular protein playing a key role in the generation of fibrosis by amplifying the TGF-β signals. SOX (SRY-related HMG box) 11 is a transcription factor playing several important roles in organ development in embryos. We have previously shown that SOX11 induces periostin expression. However, the roles of the interactions among the TGF-β signals, periostin, and SOX11 remain unknown in the pathogenesis of SSc. In this study, we found that most clones of dermal fibroblasts derived from SSc patients showed constitutive, high expression of SOX11, which is significantly induced by TGF-β1. SOX11 forms a positive loop with periostin to activate the TGF-β signals in SSc dermal fibroblasts. Genetic deletion of Sox11 in Postn-expressing fibroblasts impairs dermal fibrosis by bleomycin. Moreover, using the DNA microarray method, we identified several fibrotic factors dependent on the TGF-β/SOX11/periostin pathway in SSc dermal fibroblasts. Our findings, taken together, show that a positive loop formed by SOX11 and periostin in fibroblasts upregulates the TGF-β signals, leading to skin fibrosis.

Differential DNA Methylation Landscape in Skin Fibroblasts from African Americans with Systemic Sclerosis

The etiology and reasons underlying the ethnic disparities in systemic sclerosis (SSc) remain unknown. African Americans are disproportionally affected by SSc and yet are underrepresented in research. The aim of this study was to comprehensively investigate the association of DNA methylation levels with SSc in dermal fibroblasts from patients of African ancestry. Reduced representation bisulfite sequencing (RRBS) was performed on primary dermal fibroblasts from 15 SSc patients and 15 controls of African ancestry, and over 3.8 million CpG sites were tested for differential methylation patterns between cases and controls. The dermal fibroblasts from African American patients exhibited widespread reduced DNA methylation. Differentially methylated CpG sites were most enriched in introns and intergenic regions while depleted in 5' UTR, promoters, and CpG islands. Seventeen genes and eleven promoters showed significant differential methylation, mostly in non-coding RNA genes and pseudogenes. Gene set enrichment analysis (GSEA) and gene ontology (GO) analyses revealed an enrichment of pathways related to interferon signaling and mesenchymal differentiation. The hypomethylation of DLX5 and TMEM140 was accompanied by these genes' overexpression in patients but underexpression for lncRNA MGC12916. These data show that differential methylation occurs in dermal fibroblasts from African American patients with SSc and identifies novel coding and non-coding genes.

The contribution of epigenetics to the pathogenesis and gender dimorphism of systemic sclerosis: a comprehensive overview

Systemic sclerosis (SSc) is a life-threatening connective tissue disorder of unknown etiology characterized by widespread vascular injury and dysfunction, impaired angiogenesis, immune dysregulation and progressive fibrosis of the skin and internal organs. Over the past few years, a new trend of investigations is increasingly reporting aberrant epigenetic modifications in genes related to the pathogenesis of SSc, suggesting that, besides genetics, epigenetics may play a pivotal role in disease development and clinical manifestations. Like many other autoimmune diseases, SSc presents a striking female predominance, and even if the reason for this gender imbalance has yet to be completely understood, it appears that the X chromosome, which contains many gender and immune-related genes, could play a role in such gender-biased prevalence. Besides a short summary of the genetic background of SSc, in this review we provide a comprehensive overview of the most recent insights into the epigenetic modifications which underlie the pathophysiology of SSc. A particular focus is given to genetic variations in genes located on the X chromosome as well as to the main X-linked epigenetic modifications that can influence SSc susceptibility and clinical phenotype. On the basis of the most recent advances, there is realistic hope that integrating epigenetic data with genomic, transcriptomic, proteomic and metabolomic analyses may provide in the future a better picture of their functional implications in SSc, paving the right way for a better understanding of disease pathogenesis and the development of innovative therapeutic approaches.