Effects of Simulated Microgravity on Osseointegration of Titanium Implants and the Interventional Role of Icariin Combined with Exercise

This study investigated the impact of simulated microgravity on titanium implant osseointegration and assessed the reparative efficacy of icariin (ICA) combined with treadmill exercise. Male Sprague–Dawley rats ( n = 24) were divided into four groups: normal gravity control (CON), simulated microgravity (SMG), SMG + ICA, and SMG + ICA+treadmill exercise (SMG + ICA+EXER). SMG groups underwent tail suspension for four weeks, followed by ICA (25 mg/kg/day) and/or exercise interventions. Micro-CT, fluorochrome labeling, toluidine blue staining, and biomechanical tests were performed at week 8. Micro-CT analysis revealed that Groups SMG, SMG + ICA, and SMG + ICA+EXER exhibited a gradual increase in Tb.Th, Tb.BV/TV , DA, Tb.BMD, and Tb.BMC, and a gradual decrease in BS/BV , Tb.Sp, and SMI compared to Group CON, Mineral apposition rate (MAR) and bone-to-implant contact (BIC) were also significantly higher in ICA groups ( P < 0.05 ), matching CON levels ( P > 0.05 ). Biomechanical strength was enhanced in ICA groups, with superior performance in SMG + ICA+EXER. Simulated microgravity impairs osseointegration, but ICA mitigates these effects, with treadmill exercise further augmenting bone integration and biomechanical strength. This combined strategy may serve as a viable countermeasure for maintaining implant stability in space medicine.