Figure 1. Confirmation of the effect of methylglyoxal on the expression of selected genes.

(A) The effect of methylglyoxal (MG) treatment on the mRNA expression of sFRP-4, OPG, RANKL, Trx1, Runx2, OPN, BAMBI, PPARgamma, aP2, p16^INK4a, and Casp-3 in ST2 cells. Administration of 100 µM of MG resulted in a 3.88- and a 4.63-fold increase in sFRP-4 and RANKL mRNA expression, respectively, but a decrease in OPG expression to 10% of its basal level. Quantitative real-time reverse transcription PCR (Q-real-time RT-PCR) confirmed reciprocal change in the expression levels between sFRP-4 and OPG. Furthermore, MG treatment increased p16^INK4a and caspase 3 expression, leading to cell cycle arrest and apoptosis, while markers of osteoblastic differentiation (Runx2, BAMBI, and OPN) increased slightly, and those for adipocytic differentiation (PPARγαµµα and aP2) decreased. The statistical significance was determined by Student’s t test, *P<0.05. (B) In vitro MG treatment for 12 hr, a model for the acute phase of oxidative stress on stromal cells, showed rapid induction of sFRP-4 protein in the cytoplasm of ST2 cells (right, x200, counterstained with phalloidin and DAPI), while little sFRP-4 protein was observed in the control (left, x200, counterstained with phalloidin and DAPI).