Objective. Microarray analyses of peripheral blood leukocytes have shown that patients with systemic lupus erythematosus express increased levels of type I interferon (IFN)-regulated genes. In this study we examined gene expression by peripheral blood mononuclear cells (PBMCs) from patients with systemic sclerosis (SSc) to better understand the dysregulation of the immune system in this disease. Methods. PBMC gene expression was analyzed by microarray and confirmed by real-time polymerase chain reaction (PCR). Surface protein expression of

Skin biopsy gene expression was analyzed by DNA microarray from 13 dSSc patients enrolled in an open label study of rituximab, 9 dSSc patients not treated with rituximab, and 9 healthy controls. These data recapitulate the patient ‘intrinsic’ gene expression subsets described previously including proliferation, inflammatory, and normal-like groups. Serial skin biopsies showed consistent and non-progressing gene expression over time, and importantly, the patients in the inflammatory subset do not move to the fibroproliferative subset, and vice versa. We were unable to detect significant differences in gene expression before and after rituximab treatment, consistent with an apparent lack of clinical response. Serial biopsies from each patient stayed within the same gene expression subset regardless of treatment regimen or the time point at which they were taken. Collectively, these data emphasize the heterogeneous nature of SSc and demonstrate that the intrinsic subsets are an inherent, reproducible and stable feature of the disease that is independent of disease duration. Moreover, these data have fundamental importance for the future development of personalized therapy for SSc; drugs targeting inflammation are likely to benefit those patients with an inflammatory signature, whereas drugs targeting fibrosis are likely to benefit those with a fibroproliferative signature.

BackgroundPulmonary arterial hypertension (PAH) is a common complication for individuals with limited systemic sclerosis (lSSc). The identification and characterization of biomarkers for lSSc-PAH should lead to less invasive screening, a better understanding of pathogenesis, and improved treatment.Methods and FindingsForty-nine PBMC samples were obtained from 21 lSSc subjects without PAH (lSSc-noPAH), 15 lSSc subjects with PAH (lSSc-PAH), and 10 healthy controls; three subjects provided PBMCs one year later. Genome-wide gene expression was measured for each sample. The levels of 89 cytokines were measured in serum from a subset of subjects by Multi-Analyte Profiling (MAP) immunoassays. Gene expression clearly distinguished lSSc samples from healthy controls, and separated lSSc-PAH from lSSc-NoPAH patients. Real-time quantitative PCR confirmed increased expression of 9 genes (ICAM1, IFNGR1, IL1B, IL13Ra1, JAK2, AIF1, CCR1, ALAS2, TIMP2) in lSSc-PAH patients. Increased circulating cytokine levels of inflammatory mediators such as TNF-alpha, IL1-beta, ICAM-1, and IL-6, and markers of vascular injury such as VCAM-1, VEGF, and von Willebrand Factor were found in lSSc-PAH subjects.Conclusions and SignificanceThe gene expression and cytokine profiles of lSSc-PAH patients suggest the presence of activated monocytes, and show markers of vascular injury and inflammation. These genes and factors could serve as biomarkers of PAH involvement in lSSc.

Objective. Improved outcome measures in systemic sclerosis (SSc) are critical to finding active therapeutics for this disease. The modified Rodnan skin thickness score (MRSS) is the current standard for evaluating skin disease in SSc, but it is not commonly used in the clinical setting, in part because it requires specialized training to perform accurately and consistently. The purpose of this study was to investigate whether skin gene expression might serve as a more objective surrogate outcome measure to supplement skin score evaluations.Methods. Skin RNAs from a group of patients with diffuse cutaneous SSc were studied for expression levels of genes known to be regulated by transforming growth factor ␤ (TGF␤) and interferon (IFN). These levels were correlated with the MRSS, using multiple regression analyses to obtain best-fit models.Results. Skin expression of the TGF␤-regulated genes cartilage oligomeric matrix protein (COMP) and thrombospondin 1 (TSP-1) correlated moderately well with the MRSS, but the addition of other TGF␤-regulated genes failed to significantly improve best-fit models. IFN-regulated genes were also found to correlate with the MRSS, and the addition of interferoninducible 44 (IFI44) and sialoadhesin (Siglec-1) to COMP and TSP-1 in multiple regression analyses significantly improved best-fit models, achieving an R 2 value of 0.89. These results were validated using an independent group of skin biopsy samples. Longitudinal scores using this 4-gene biomarker indicated that it detects change over time that corresponds to changes in the MRSS.Conclusion. We describe a 4-gene predictor of the MRSS and validate its performance. This objective measure of skin disease could provide a strong surrogate outcome measure for patient care and for clinical trials.

Systemic sclerosis (SSc) is a complex human disorder characterized by progressive skin fibrosis. To better understand the molecular basis of dermal fibrosis in SSc, we analyzed microarray gene expression in skin of the Tight-skin (Tsk) mouse, an animal model where skin fibrosis is caused by an in-frame duplication in fibrillin-1 (Fbn-1). Tsk skin showed increased mRNA levels of several genes involved in Wnt signaling, including Wnt2, Wnt9a, Wnt10b and Wnt11; Dapper homolog antagonist of beta-catenin (DACT1) and DACT2; Wnt-induced secreted protein 2; and secreted frizzled-related protein (SFRP)2 and SFRP4. RNase protection and northern blot confirmed microarray results. Furthermore, Wnt3a markedly stimulated matrix assembly of microfibrillar proteins, including Fbn-1, by cultured fibroblasts, suggesting that Wnts contribute to increased microfibrillar matrices in Tsk skin. Further analysis showed that SFRP4 expression is specifically increased in tissues expressing Tsk-Fbn-1, such as skeletal muscle and skin. The increase in SFRP4 mRNA in Tsk skin started 2 weeks after birth, following the increase in Wnt2 mRNA that occurred at birth. This suggests that SFRP4 may modulate Wnt functions in Tsk skin fibrosis. Lesional skin from SSc patients also showed large increases in SFRP4 mRNA and protein levels in the deep dermis compared to healthy skin, suggesting that the Wnt pathway might regulate skin fibrosis in SSc.