Proteomic analysis identification of a pattern of shared alterations in the secretome of dermal fibroblasts from systemic sclerosis and nephrogenic systemic fibrosis.

A proteomic analysis of the secretome of cultured dermal fibroblasts from patients with systemic sclerosis (SSc) and nephrogenic systemic fibrosis (NSF) was performed to identify proteins that reflect the fibrotic process. Confluent culture supernatants from three cell strains each of normal, SSc, and NSF dermal fibroblasts were pooled separately, and each pool was labeled with a specific fluorochrome. The three pools were electrophoresed together on two-dimension SDS gels, and protein differential expression was evaluated by quantitative fluorescence analysis. The secretome analysis identified 1694 spots per sample, among which 890 spots (52%) were differentially increased or decreased (more than twofold) in SSc fibroblasts, and 985 spots (58%) were differentially increased or decreased in NSF fibroblasts compared with normal fibroblasts. Mass spectrometry analysis was then used to identify the proteins that had increased by the greatest extent in both NSF and SSc secretomes. Three reticulocalbin family members were among the 10 most up-regulated proteins. Confocal microscopy results validated the differential increase of reticulocalbin-1 in affected SSc and NSF skin, and Western blot findings demonstrated its presence in SSc sera. The secretomes of both SSc and NSF fibroblasts display a pattern of shared changes compared with the normal fibroblast secretome. The differentially increased proteins reflect an activated fibroblast phenotype and may represent a specific "fibrosis signature" that can be used as a biomarker for fibrotic diseases.