Collagen gel contraction assay

Collagen gel contraction assays were performed as previously described [23]. In brief, 1.2 mg/ml collagen solution (Invitrogen, USA), 10× DMEM/F12, 0.5N NaOH and ARPE-19 cells (1 × 10⁵ cells per well) were mixed and added to a 24-well culture plate. After incubation for 1 hour at 37°C to allow collagen polymerization, the gelatinous suspension was detached from the well edges using a sterile pipette tip. The collagen gel was allowed to float in serum free DMEM/F12 media containing TGF-β and AdLacZ or AdCCN5. ImageJ software was used to calculate the extent of collagen gel contraction.