Western- blot assay shows expression of aging marker proteins 4- Hydroxynonenal ( 4-HNE), p16 and Id1 in bmMSCs after exposure to 0, 1, 5 and 10 ng/ mL TGF- β1 for 24 hours. A. 4-HNE expression; B. P16 expression; C. Id1 expression. Bar graphs represent mean ± SD (4 independent experiments/group). *P < 0.05 vs. control.