A Longitudinal Biomarker for the Extent of Skin Disease in Patients With Diffuse Cutaneous Systemic Sclerosis

Abstract

Objective The goal of this study was to define a pharmacodynamic biomarker based on gene expression in skin that would provide a biological measure of disease extent in patients with diffuse cutaneous systemic sclerosis (dcSSc) and that could be used to monitor skin disease longitudinally. Methods Skin biopsies taken from a cohort of dcSSc patients that included longitudinal samples were analyzed by microarray. Expression of genes correlating with the modified Rodnan skin score (MRSS) were examined by nanostring for change over time, and a generalized estimating equation used to define and validate longitudinal, pharmacodynamic biomarkers composed of multiple genes. Results Microarray analysis of genes parsed to include only genes correlating with the MRSS revealed prominent clusters of profibrotic/TGFβ-regulated, IFN-regulated/proteasome, macrophage and vascular marker genes. Using genes changing longitudinally with the MRSS, two multigene, pharmacodynamic biomarkers were defined. The first was defined mathematically, applying a generalized estimating equation to longitudinal samples. This modeling method selected cross-sectional THBS1 and longitudinal THBS1 and MS4A4A genes. The second model was based on a weighted selection of genes, including additional genes with statistically significant change over time: CTGF, CD163, CCL2 and WIF1. Biomarker levels calculated using both models correlated highly with the MRSS in an independent validation dataset. Conclusion Skin gene expression can be used effectively to monitor SSc skin disease change over time. We have implemented these relatively simple models on a nanostring platform permitting highly reproducible assays that can be applied directly to samples from patients or collected as part of clinical trials.

Fresolimumab treatment decreases biomarkers and improves clinical symptoms in systemic sclerosis patients

“…On the other hand, skin thickness did not change significantly after fresolimumab treatment. The MRSS is primarily designed to detect changes in skin thickness; however, the effect of fresolimumab on the MRSS is likely due to changes in skin tightness and tethering that result from block- two genes in the 2GSSc skin biomarker (24). The change in macrophage marker genes was less dramatic (and not statistically significant in this small trial) but might suggest that TGF-β also contributes to the perivascular inflammation seen in this disease.…”

“…We tested the effect of treatment with fresolimumab on a recently developed, multianalyte, longitudinal pharmacodynamic biomarker (2GSSc skin biomarker; ref. 24). This biomarker is composed of weighted values for THBS1 and MS4A4A mRNA expression assessed by NanoString.…”

Altered Dermal Fibroblasts in Systemic Sclerosis Display Podoplanin and CD90

“…33 Two separate data sets were obtained using the same U133A 2.0 chip (Affymetrix, Santa Clara, CA). 33,34 These data were normalized for batch differences using the ComBat algorithm (SVA 3.18 package; Bioconductor http://www.bioconductor.org/packages/release/BiocViews. html#_Software).…”

Integrated, multicohort analysis of systemic sclerosis identifies robust transcriptional signature of disease severity

“…Although validated, the mRSS is problematic and subjective because it requires a long duration between measurements to assess interval change, and is confounded by obesity, edema, and interclinician variance. Although a number of previous studies have identified genomic biomarkers of skin disease (3)(4)(5), these studies have been performed on small numbers of patients and the biomarkers have not been robustly validated in independent cohorts from multiple clinical centers.…”