Platelet contributions to the pathogenesis of systemic sclerosis

The purpose of this review is to focus attention on platelet contributions, in general, to systemic sclerosis. There have also been recent advances in characterization of the phenotype of platelets in systemic sclerosis which will be reviewed.

An extensive literature provides strong support for varying degrees of platelet activation and aggregation in different forms and stages of systemic sclerosis. A recent finding is that systemic sclerosis platelets overexpress a specific nonintegrin 65 kDa receptor for type I collagen as well as expressing enhanced phosphilidylinositol-3 kinase as an activation signature. Overexpression of a type I collagen receptor would make systemic sclerosis platelets more susceptible to binding to exposed type I collagen in the subendothelial lining of damaged blood vessels, facilitating the cycle of platelet aggregation and release of preformed bioactive molecules that include a host of inflammatory and fibrogenic, chemokines, cytokines and growth factors. This activation phenotype of systemic sclerosis platelets may be secondary to autoimmunity and driven by cytokines from autoreactive T cells.

The contributions of platelets to the pathogenesis of systemic sclerosis is likely substantial and may not be adequately represented in gene profiling of systemic sclerosis tissue due to the small amounts of RNA contained in platelets.