Therapeutic targets in systemic sclerosis

Abstract

The precise aetiology of systemic sclerosis (SSc) remains elusive, but significant advances over the past few years have improved our understanding of the underlying pathogenic processes and identified key pathways and mediators that are potential therapeutic targets. The situation is complicated by the clinical heterogeneity of SSc and the differential pathogenesis that underlies the two commonest subsets, namely diffuse and limited cutaneous disease. However, there are common mediators that could be targeted to provide clinical benefit in both types of disease. To date, clinical success with therapies directed against logical profibrotic mediators, such as connective tissue growth factor and transforming growth factor-beta, is yet to be reported, although studies are ongoing. More promising clinical results have been obtained with the dual endothelin receptor antagonist bosentan, which has been shown to manage two vascular complications of SSc effectively: pulmonary arterial hypertension and digital ulceration. It remains to be determined whether the identification of additional mediators merely furthers our knowledge of the natural history of SSc or presents targets that can be manipulated to manage SSc patients effectively.

Figure 1

Cellular interactions in pathogenesis of SSc. The multiple cell types implicated in pathogenesis of SSc are illustrated. Soluble mediators involved in this intercellular cross-talk are candidate targets for therapeutic intervention. bFGF, basic fibroblast growth factor; CTGF, connective tissue growth factor; EC, endothelial cell; ECM, extracellular matrix; ET, endothelin; IFN, interferon; IL, interleukin; MCP, monocyte chemoattractant protein; PDGF, platelet-derived growth factor; SMA, smooth muscle actin; SSc, systemic sclerosis; TGF, transforming growth factor; TH, T-helper (cell); Treg, regulatory T (cell); VEGF, vascular endothelial growth factor. Reproduced with permission from [1].