Enhanced tenogenic differentiation in response to Pro-Hyp in adult tenocytes and tendon progenitor cells.A, real-time PCR analysis of Scx, Sox9, Mkx, and Tnmd mRNA levels. Cells were treated with Pro-Hyp and cultured for 3, 6, and 11 days. mRNA expression levels are shown relative to the control value of 1 (untreated cells). Error bars represent the standard deviation (n = 3). ∗p < 0.05; ∗∗p < 0.01; and ∗∗∗p < 0.001 (in post hoc analysis). B, the effect of Pro-Hyp on ScxGFP expression in adult tenocytes and tendon progenitor cells. In adult tenocyte cultures, TGF-β1 (2 ng/ml) was used as a positive control (46). The scale bars represent 100 μm. Pro-Hyp, prolyl-4-hydroxyproline; ScxGFP, Scx promoter–driven GFP; TGF-β1, transforming growth factor-beta.