Cell culture and reagents
Human BMSCs were purchased from American Type Culture Collection. Mononuclear cells were cultured with low glucose-Dulbecco’s modified Eagle’s medium (Gibco) containing 10% fetal bovine serum and 1% penicillin/streptomycin at 37℃ in a 5% CO2. Cells with passages 3 or 4 were used for the experiments treated with ginsenoside Rg3 (Cayman Chemical) or 0.25% ethanol as a vehicle. The detailed information is described in Supplemental Methods.
Quantitative polymerase chain reaction (qPCR)
Total RNA was isolated from BMSCs and used to synthesizing cDNA. Transcript levels were measured by QuantStudio™ 6 Real‐Time PCR System (Applied Biosystems) using sequence-specific primers listed in supplementary figure 1. The cycle threshold (Ct) values of the target genes were normalized to control (Peptidylprolyl isomerase A), and the relative amount was calculated by using the equation, 2-ΔΔCt.
Western blot analysis
The cells were lysed using RIPA lysis buffer and lysates were separated by 10-15% sodium dodecyl sulfate-polyacrylamide gel electrophoresis and transferred to polyvinylidene fluoride membranes. The membranes were incubated overnight with primary antibodies, the detailed information of which is described in Supplemental Methods. After washing, the membranes were incubated for 1 h in horseradish peroxidase-conjugated secondary antibodies. The membranes were incubated in a developing solution (GE Healthcare) and signal was detected using Chemi-Doc System (Bio-rad)..
Senescence-associated β-galactosidase (SA-β-gal) staining
SA-β-gal activity was assessed with a senescence β-gal staining kit (Cell Signaling Technologies) according to the manufacturer’s instructions.
Adipogenic and Osteogenic Differentiation
BMSCs were maintained for two or three weeks in either osteogenic or adipogenic medium. The osteogenic medium contains 10 mM β-glycerophosphate (Sigma), 0.2 mM Ascorbic acid-2-phosphate (Sigma) and 100 nM dexamethasone (Sigma). After 14 days, Alizarin Red staining was performed and the absorbance at 540 nm were detected by spectrophotometer. The adipogenic medium contains 1 mM dexamethasone, 0.5 mM 1-methyl-3-isobutylxanthine (Sigma), 100 µM indomethacin (Sigma), and 10 µg/mL insulin (Sigma). After 21 days, Oil Red-O staining was performed and the absorbance at 520 nm were detected.
Oxygen Consumption Rate (OCR) and ExtraCellular Acidification Rate (ECAR) measurement
OCR and ECAR were measured in BMSCs using the Seahorse XFe96 Analyzer (Agilent Technologies) in response to XF Cell Mito Stress Test Kit or Glycolysis Stress Test Kit (Agilent Technologies). Supplemental Experimental Procedures provides detailed information about OCR and ECAR measurement from BMSCs.
Cytosolic ROS measurement
BMSCs were loaded with 5 µM DCFH2DA (Invitrogen) for 20 min at 37℃ and fluorescence intensity reflecting ROS production was measured at the excitation and emission wavelengths of 485 and 538 nm using a fluorescence-activated cell sorting (FACSAria III, BD Biosciences, USA).
Live-cell Ca2+ imaging
BMSCs seeded on 12 mm coverslip were loaded with 5 µM Fura-2/AM (Thermo Fisher Scientific) for 30 min at 37°C. Then, cells were transferred to a perfusion chamber on an inverted microscope (IX73, Olympus). Fluorescence images with an illuminator (pe-340Fura; CoolLED) were captured at 510 nm with a CCD camera (Prime-BSI; Teledyne Photometrics) and the ratio of fluorescence intensities (F340/F380) reflecting intracellular Ca2+ was analyzed by MetaFluor 6.1 (Molecular Devices).
Statistical analysis
Student’s t-test was used to compare means of two data groups. One-way ANOVA was used to compare means of two or more data groups. All graphs and statistical analysis were performed using software (Prism version 6.0, GraphPad Software). Data are presented as mean ± SD and P < 0.05 was considered significant.