Elevated phosphorylated extracellular signal-regulated kinase 1/2 expression in Dupuytren's tissue samples. (A) Immunostaining for phosphorylated extracellular signal-regulated kinase 1/2 (P-ERK1/2) and secondary antibody control (P-ERK1/2 antibody omitted) of Dupuytren's and control tissue specimens. Representative staining from Dupuytren's patient 4 and control patient 1 is shown. (B) Quantitative analysis of P-ERK1/2-positive cells (shown in Figure 4A) from three control and three Dupuytren's tissue samples expressed as percentages. (C) Western blot analysis of lysates from pooled Dupuytren's fibroblasts (mixture 1 through 4) to determine P-ERK1/2 in untreated or rec. TGF-β3 (0.1 ng/mL)-treated cells for either 5 minutes or 18 hours in the presence or absence of SB-431542 (20 μmol) or rec. BMP6 (100 ng/mL). (D) Expression of PDGF-B (platelet-derived growth factor B) mRNA from four controls (mixture 1 through 4) and Dupuytren's fibroblasts (mixture 1 through 4) stimulated with 0.1 ng/mL rec. TGF-β3 in the presence or absence of 20 μmol SB-431542 or 100 ng/mL rec. BMP6 for 18 hours. Quantitative PCR was performed, and values are expressed relative to the average of the control (mixture 1 through 4) mRNA values using GAPDH as an internal reference.