Fig. 6
Activation of mTORC1 pathway and heterochromatin organization in D-Gal-induced rat aging. SD male rats were randomly divided into two groups. The D-gal-treated group was injected with 125 mg/kg D-galactose dissolved in sterile 0.9% saline intra-peritoneally daily. The control group was injected with the same volume of 0.9% saline. After consecutive injection for 4 months, the animals were sacrificed and the tibia and femur were collected for further study. a Weight increment of rats of each group (n = 8) at the end of experiments, **p < 0.01 by Student t test. b Femur length of rats of each group (n = 4). c Test of maximum load, ultimate stress, and Young’s modulus of femurs from each group (n = 8), *p < 0.05 by Student t test. d Representative 3D image of femurs (n = 4) and representative 3D image of femur regions of interest (the range between 300 and 450 slices below the growth plate). e Quantification of morphometric parameters including bone volume (BV), trabecular volume (TV), bone fraction (BV/TV), trabecular number (Tb.N, 1/mm), trabecular separation (Tb.Sp, mm), and trabecular thickness (Tb, Th, mm) are shown. *p < 0.05; **p < 0.01 by Student t test (n = 4). f Western blot analysis in BMSCs (p3-4) isolated from rats of each group (CT: n = 3, D-gal, n = 4). Quantification data is shown below, *p < 0.05; **p < 0.01;***p < 0.001 by Student t test. g 1 × 106 primary BMSCs derived from control or D-Gal treated rats (p3-p5) were treated with rapamycin for 48 h. RT-PCR shows the expression levels of senescence markers were significantly reduced in rapamycin-treated rBMSCs (n = 3), *p < 0.05;**p < 0.01 by Student t test. h 1 × 106 primary BMSCs derived from control or D-Gal-treated rats (p3-p5) were treated with rapamycin for 48 h. Representative Western blot results shows that rapamycin treatment suppresses p70S6K activation and upregulates the expression of H3K9me3 in rBMSCs derived from control and D-Gal-treated rats (n = 4)