Molecular Subsets in the Gene Expression Signatures of Scleroderma Skin

Abstract

BackgroundScleroderma is a clinically heterogeneous disease with a complex phenotype. The disease is characterized by vascular dysfunction, tissue fibrosis, internal organ dysfunction, and immune dysfunction resulting in autoantibody production.Methodology and FindingsWe analyzed the genome-wide patterns of gene expression with DNA microarrays in skin biopsies from distinct scleroderma subsets including 17 patients with systemic sclerosis (SSc) with diffuse scleroderma (dSSc), 7 patients with SSc with limited scleroderma (lSSc), 3 patients with morphea, and 6 healthy controls. 61 skin biopsies were analyzed in a total of 75 microarray hybridizations. Analysis by hierarchical clustering demonstrates nearly identical patterns of gene expression in 17 out of 22 of the forearm and back skin pairs of SSc patients. Using this property of the gene expression, we selected a set of ‘intrinsic’ genes and analyzed the inherent data-driven groupings. Distinct patterns of gene expression separate patients with dSSc from those with lSSc and both are easily distinguished from normal controls. Our data show three distinct patient groups among the patients with dSSc and two groups among patients with lSSc. Each group can be distinguished by unique gene expression signatures indicative of proliferating cells, immune infiltrates and a fibrotic program. The intrinsic groups are statistically significant (p<0.001) and each has been mapped to clinical covariates of modified Rodnan skin score, interstitial lung disease, gastrointestinal involvement, digital ulcers, Raynaud's phenomenon and disease duration. We report a 177-gene signature that is associated with severity of skin disease in dSSc.Conclusions and SignificanceGenome-wide gene expression profiling of skin biopsies demonstrates that the heterogeneity in scleroderma can be measured quantitatively with DNA microarrays. The diversity in gene expression demonstrates multiple distinct gene expression programs in the skin of patients with scleroderma.

FIZZ1-Induced Myofibroblast Transdifferentiation from Adipocytes and Its Potential Role in Dermal Fibrosis and Lipoatrophy

“…In humans, FIZZ2 is highly induced in the lungs of patients with idiopathic pulmonary fibrosis 12 and scleroderma-associated pulmonary hypertension 13 and in the serum of patients with SSc. 14 The findings with the use of the BLM-induced dermal fibrosis model found loss of adipogenic gene expression that was accompanied with increased myofibroblast differentiation and collagen deposition, consistent with the in vitro effects of FIZZ1 on adipocytes. Notch1 expression was also noted to be up-regulated simultaneously with elevation of FIZZ1 gene expression in WT but was essentially abolished in FIZZ1 KO skin.…”

“…29 In this study we report a potential role for FIZZ1 in regulating dermal fibrosis in SSc by targeting the dermal adipocyte and/or its progenitor cell, a suggestion that is supported by in vivo observations of up-regulation of FIZZ2 expression in SSc. 14 …”

Altered Dermal Fibroblasts in Systemic Sclerosis Display Podoplanin and CD90

“…Historically, elements of inflammation, proliferation, and fibrosis have been defined by transcriptional profiling of SSc skin. 58,59 To explore this question, we identified those genes from the total skin biopsy microarray analysis that correlated with the Pdpn/CD34 and CD90/CD34 RNA ratios as well as MRSS values. Using a cutoff of q < 0.05, we found 49 genes associated with the Pdpn/CD34 ratio, 530 with CD90/CD34, and 437 with MRSS ( Figure 4 and Supplemental Table S2).…”

Biomarkers in Systemic Sclerosis

“…Microarrays may also provide valuable molecular signatures that can be used as biomarkers of utility as diagnostic or prognostic tools and as markers of the effectiveness of disease-modifying therapies. Indeed, recent microarray studies of intact skin, peripheral blood mononuclear cells or cultured dermal fibroblasts disclosed distinct patterns of gene expression capable of distinguishing patients with limited SSc from those with diffuse SSc, and allowed the identification of separate subsets within these two groups that correlate with various clinical parameters and internal organ involvement [113][114][115][116][117][118]. Microarray studies have also been employed to identify specific patterns of gene expression in SSc-associated pulmonary fibrosis [119] and pulmonary hypertension [120], and have identified a subset of SSc patients who display a TGF-b signature in their skin [121].…”