Transforming growth factor-β induces contraction of activated hepatic stellate cells

Abstract

Background/Aims Transforming growth factor-β (TGF-β) is a cytokine produced in abundance during liver injury. Recognizing the prominent roles that hepatic stellate cells (HSCs) and TGF-β play in portal hypertension and fibrogenesis, respectively, we sought to evaluate the effect of TGF-β on the contractility of activated HSCs. Methods Spontaneous immortalized cell lines of HSC origin were used in this study. Cells were grown in three-dimensional collagen gel lattice, transferred to 60 mm dishes and exposed to varying concentrations of TGF-β1 in serum-free medium at 37 °C for up to 120 h. The area of the floating gels was measured using a Fluor S-MultiImager (Biorad), the cellular smooth muscle-α actin (SMA) content quantified and PKC activation studies conducted. Results TGF-β1 induced a time- and dose-dependent decrease in lattice area up to 40% of control ( P<0.05) that reflects the contraction of activated HSCs. This induced contraction was associated with increases in SMA content (3-fold, P<0.05) and PKC activation (5-fold, P<0.05) in these cells. Furthermore, pre-incubating with a PKC-ε-specific inhibitor completely abrogated the TGF-β-induced contraction. Conclusions TGF-β induces contraction of activated HSCs via an increase in SMA content and a PKC-ε-mediated pathway.