COL1A2 and osteogenesis imperfecta: For subsequent analyzes, we chose the concentrations of RA (0.1, 1, and 10 μM), RE (0.1, 1, and 10 μg/mL), and LBE (0.1, 1, and 10 μg/mL), at which they had the most beneficial effect on procollagen type I in OI fibroblasts.