Mechanical stretch does not reduce basal TGFβ expression in human cardiac fibroblast cells. Human primary cardiac fibroblast cells underwent either biaxial mechanical stretch for 72 h or were left un-stretched (control), in the presence or absence of 10 ng/mL transforming growth factor beta (TGFβ). Analysis of stretch induced basal gene expression changes of TGFβ, TGFβ receptor type-1 (TGFβ-R1), and TGFβ receptor type-2 (TGFβ-R2) by quantitative real-time PCR are highlighted (A). Presented gene expression fold changes in Figure A are independent of recombinant TGFβ treatment and represent the impact of mechanical stretch alone. Western blot analysis of the impact of 72 h of mechanical stretch on TGFβ induced phosphorylation of Smad2 and ERK protein expression (B). Quantitative real-time PCR analysis of the effect of exogenous TGFβ treatment on basal TGFβ expression (C). The impact of mechanical stretch and recombinant TGFβ treatment on cardiac fibroblast production and secretion of total and active TGFβ protein was assessed using ELISA-based methods (D). Bar graphs represent mean fold change ± SD. *P < 0.05, **P < 0.01.