Retinoic acid increased MGP in human VIC. (A) MGP mRNA levels and secreted protein from VIC treated for two weeks in CM or PM with DMSO vehicle (0.1%) or 1 μmol/L ATRA. (B) Alizarin red stain and relative quantification for VIC treated for three weeks. (C) RAR siRNA knockdown validation by mRNA level quantification, and Alizarin red stain and relative quantification for primary human VIC treated for two weeks in PM with negative control, RARα, RARβ, or RARγ siRNA. Error bars indicate STDEV of mean. *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001 analyzed by ANOVA or Student’s t-test; n = 3 donors.