MTOR and systemic sclerosis: To evaluate the role of mTOR as a possible downstream effector in stimulated HPASMC, we treated the cells with PDGF (15 ng/ml) or distinct SSc IgG (200 μg/ml; n = 11) for 24 h in the presence or absence of rapamycin (10 nM), a specific inhibitor of mTOR added 48 h before.