The promise of transcription profiling for understanding the pathogenesis of scleroderma

Cytokines and cytokine profiles in human autoimmune diseases and animal models of autoimmunity

The precise pathomechanisms of human autoimmune diseases are still poorly understood. However, a deepened understanding of these is urgently needed to improve disease prevention and early detection and guide more specific treatment approaches. In recent years, many new genes and signalling pathways involved in autoimmunity with often overlapping patterns between different disease entities have been detected. Major contributions were made by experiments using DNA microarray technology, which has been used for the analysis of gene expression patterns in chronic inflammatory and autoimmune diseases, among which were rheumatoid arthritis, systemic lupus erythematosus, psoriasis, systemic sclerosis, multiple sclerosis, and type-1 diabetes. In systemic lupus erythematosus, a so-called interferon signature has been identified. In psoriasis, researchers found a particular immune signalling cluster. Moreover the identification of a new subset of inflammatory T cells, so-called Th17 T cells, secreting interleukin (IL)-17 as one of their major cytokines and the identification of the IL-23/IL-17 axis of inflammation regulation, have significantly improved our understanding of autoimmune diseases. Since a plethora of new treatment approaches using antibodies or small molecule inhibitors specifically targeting cytokines, cellular receptors, or signalling mechanisms has emerged in recent years, more individualized treatment for affected patients may be within reach in the future.

Cartilage oligomeric matrix protein is overexpressed by scleroderma dermal fibroblasts

Cartilage oligomeric matrix protein (COMP) is an extracellular glycoprotein that belongs to the thrombospondin gene family. It is found predominantly in cartilage, tendon, ligament, and bone. Mutations in the COMP gene have been linked to the development of pseudoachondroplasia and multiple epiphysial dysplasia. COMP influences the organization of collagen fibrils by interacting with collagens I, II and IX. Gene expression profiling of cultured skin fibroblasts suggested that COMP mRNA levels were elevated in scleroderma. We therefore examined COMP expression in SSc and normal skin biopsies. Immunohistochemistry confirmed that COMP protein accumulates in SSc but not normal skin, with SSc skin showing striking deposition in the papillary and deeper dermis. Significant staining was also seen in non-lesional skin from patients. Due to its involvement in the development of fibrosis, TGFbeta was examined for a possible role in regulating COMP expression. Cultured SSc fibroblasts demonstrated greater staining for COMP compared to normal controls prior to stimulation, and TGFbeta-1 induced a large increase in mRNA and protein. Murine fibroblasts engineered to overexpress human COMP demonstrated increased levels of fibronectin and collagen in the extracellular matrix. Taken together, these data demonstrate that COMP is overexpressed in SSc skin and cultured fibroblasts possibly due to autocrine TGFbeta stimulation, and COMP overexpression is sufficient to stimulate excess matrix deposition. By interactions with other matrix proteins and cells, COMP may play a role in pathogenic matrix deposition.

High plasminogen activator inhibitor type 2 expression is a hallmark of scleroderma fibroblasts in vitro

Systemic scleroderma is a chronic disease, which leads to fibrosis of the skin and internal organs. Fibroblasts obtained from patients with this disease demonstrate an activated state in culture. We, in this study, report strong, constitutive overexpression of plasminogen activator inhibitor type-2 (PAI-2) in scleroderma fibroblasts and demonstrate that this induction observed at the mRNA and protein level is dependent on serum addition. Induced PAI-2 protein levels were restricted to the non-glycosylated 47-kDa form, which is located intracellularly. Induction was stable for at least 12 passages. No modulation by fibrogenic cytokines--for example, transforming growth factor-beta1 or connective tissue growth factor--or by antagonizing IL-1 receptors was observed. The data indicate that scleroderma fibroblasts are more sensitive to the induction of PAI-2 expression than control fibroblasts by a presently unknown factor in serum.