Effect of Sildenafil on the Microcirculatory Blood Flow and Endothelial Progenitor Cells in Systemic Sclerosis

Inclusion Criteria: * Systemic sclerosis according to the classification criteria of the American College of Rheumatology (1980) with no more than 4 years since diagnosis * Early systemic sclerosis as defined by LeRoy and Medsger (2001) * 6 or more Raynaud's crisis per week * Written informed consent provided by the subjects prior to initiating study procedures Exclusion Criteria: * Smoking * Peripheral or central vasculopathy other than Systemic sclerosis * Uncontrolled Diabetes * Liver disease * Pregnant or lactating woman * Current use of cyclosporin, prostanoids, bosentan or any PDE-5 inhibitors (including current Sildenafil use during randomization) * History of stroke, myocardial infarction or life threatening cardiac condition within the last 6 months * History of surgical sympathectomy * Systolic blood pressure \< 85mm Hg * History of scleroderma renal crisis * Known hypersensitivity to Sildenafil or any of the excipients * History of Retinitis Pigmentosa * Current use of Nitrates