MAPK3 and dentin dysplasia: To determine the role of PDGF signalling in the augmented ERK1/2 phosphorylation observed in DD, we treated Dupuytren's fibroblasts with a selective PDGF receptor tyrosine kinase inhibitor (STI571, also known as imatinib mesylate) [36] and compared its effect with the effects of the inhibitors SB-431542 and PD98059.