Adipose-derived mesenchymal stem cells demonstrate milder response to ultraviolet and doxorubicin-induced DNA damage and to oxidative stress. (A), (B) p21 and btg2 RNA expression after ultraviolet (UV) irradiation in elevating doses (J/m2) in four bone marrow mesenchymal stem cell (BM MSC) preparations and three adipose-derived mesenchymal stem cell (ASC) preparations. No irradiation was normalized as 1, bars indicate mean ± standard deviation. Regression of gene expression fold-change as a function of UV intensity was compared between tissues using analysis of covariance, with tissue as a categorical factor, and UV intensity as a covariate. (C), (D) Induction of RNA expression of the indicated genes following incubation with either 0.5 μg/ml doxorubicin for 24 hours or 6 hours following incubation with hydrogen peroxide (H2O2), respectively, was compared between six adipose-derived mesenchymal stem cell and BM MSC preparations. *P <0.05, unpaired equal variance two-tailed t test of adipose-derived mesenchymal stem cells vs. BM-MSCs.