Both Substance P (SP) and Transforming Growth Factor Beta 1 (TGFβ-1) increased proliferation in cultured rat tenocytes. After allowing equal numbers of cells to adhere overnight in 10% FBS, cells were serum restricted (1% FBS) for 24 hours, and then treated with TGFβ-1, SP, or their combination, at the indicated concentrations for 72 hours. (A) Proliferation was evaluated by CyQUANT® NF Cell Proliferation Assay and normalized to cell number using a standard curve. Data are the means of six independent experiments ± standard error (SEM). (B) BRDU incorporation was assayed. Data are the means of three independent experiments. Two-way ANOVA results shown. * and **: p<0.05 and p<0.01, respectively, compared to vehicle controls (PBS and 1% BSA only; indicated as “0”); #: p<0.05, compared to SP only treatment.