Mechanical force loading

The force-loading plates (7.6 × 3.6 cm² and 1.2 mm thick) were prepared on the bottom surface of a 75-cm² cell canted-neck culture flask. Passage 3 rBMSCs were seeded onto the center area (5 × 3.6 cm) of the force-loading plates at a density of 2 × 10⁵ cells. The force-loading plates were subjected to daily cyclic uniaxial tensile strain (0.5 Hz, 2000 με, 2 h/day) in an osteogenic differentiation medium (1 × 10^-8 M dexamethasone, 10 mM β-glycerophosphate, and 50 μg/ml L-ascorbic acid) (Sigma-Aldrich, St Louis, MO, USA) by a four-point bending system (Sichuan University, Chengdu, China) [27, 46].