*2.9. HSC Contraction Assay*

For quantification of activated HSC contraction, 6-well plates were covered with a thick layer of 1 mL/well rat tail collagen. Rat HSCs were isolated as described before [32]. Cells were put on 6-well plates at a density of 6 <sup>×</sup> 105 cells/well. Cells were kept in DMEM supplemented with 10% FCS and 1% antibiotics for 7 days. Medium was exchanged every 48 h starting the day after isolation. At day 7 after isolation, cells were treated with serum-free medium containing DMSO, 10 μM TGR5 agonist, or 10 μM forskolin for 30 min. After detachment of collagen lattices from the 6-well surface, cells were treated with ET-1 (Sigma-Aldrich) at a concentration of 1nM to induce contraction for 2 h and 24 h. Photos of cell/collagen lattice areas were taken at the time of ET-1 addition and after 2 h and 24 h (Supplementary Figure S2). Surface area was measured using the ImageJ distribution Fiji V.2.0.0 [33,34]. The lattice area used as control treated with DMSO and vehicle for the respective time points was set to 1.0.
