Combination treatment with whole body vibration and simvastatin improves the early osseointegration in aged rats

Abstract

Background: Current research has demonstrated that Simvastatin (SIM) and Whole Body Vibration (WBV) actively contributes to the repair of osteoporotic bones. However, there is still limited knowledge regarding the impact of this combined therapy on osseointegration in elderly individuals. Objective: The objective of this study was to verify the influence of WBV and SIM combination treatment on Titanium implants' fixation strength in aged rats.

Methods: Male Sprague-Dawley rats at 24 months old were utilized for this investigation. Titanium rods were surgically inserted into the distal femoral canal on their left side. Subsequently, all animals were randomly assigned to one of four groups: Control group; WBV group; SIM group; and WBV + SIM group. Each group received Saline, Whole Body Vibration, Simvastatin, or a combination of Whole Body Vibration plus Simvastatin treatment until they reached their natural death after 12 weeks. The bilateral femurs and serum samples from these rats were collected for evaluation purposes.

Results: Both WBV and SIM treatments exhibited an increase in bone mass, osseointegration, and push-out force compared to the Control group (all, P < 0.05). Additionally, levels of oxidative stress and inflammatory factors decreased with both treatments when compared to the Control group alone (all, P < 0.05). Notably, the WBV + SIM group displayed superior effects on new bone formation, biomechanical strength, BMP2 expression in bone tissue as well as SOD2 expression regulation related to bone repair genes when compared to other groups involved in this study (all, P < 0.05).

Conclusion: These findings suggest that combining physiotherapy (WBV) with drug therapy (SIM) proves beneficial for enhancing implant fixation in aged rats.

Keywords: Bone loss; Osseointegration; Oxidative stress; Simvastatin; Whole body vibration.

Fig. 1

WBV plus SIM can significantly improve osseointegration in aged rats. A. Micro-CT scans were conducted on the distal femur at a 12-week interval following the placement of implants in four groups: Con, WBV, SIM, and WBV + SIM. B. Assessment of implant osseointegration at the 12-week milestone after implantation through micro-CT analysis, employing quantitative measures.

Fig. 2

Combined treatment with WBV and SIM can significantly improve osseointegration in aged rats. A. Images of representative Von-Gieson stained sections of the distal femur 12 weeks after implantation in Con, WBV, SIM and WBV + SIM groups. B. Changes of BIC and BAR values in Con, WBV, SIM and WBV + SIM groups.

Fig. 3

The biomechanical outcomes were quantified as the maximum force (N) required for push-out in four groups: Control group, WBV group, SIM group, and WBV + SIM group.

Fig. 4

The results obtained from micro-CT and Histological evaluation were employed to demonstrate that the combination of WBV with SIM resulted in a significant increase in bone mass in OVX rats. A: Representative Micro-CT 2D and 3D reconstructions, as well as scan images after 12 weeks of treatment from the Con, WBV, SIM, and WBV + SIM groups (scale bar = 1 mm). B: The quantitative parameters including BMD, BV/TV, Tb. Th, Tb. N, Conn.D and Tb.Sp (N = 5). C: Systemic administration of WBV and SIM led to increased bone mass in OVX rats when evaluated using HE and Masson stainings (scale bar = 100 μm).

Fig. 5

Changes in serum IL-1β, IL-6, and TNF-α at 12 weeks of intervention were observed in Con group, WBV group, SIM group, and WBV + SIM group.

Fig. 6

Changes in serum ALP, CTX-1, TRACP-5b and BGP at 12 weeks of intervention were observed in Con group, WBV group, SIM group, and WBV + SIM group.

Fig. 7

Changes in serum MDA, SOD, and GSH-PX at 12 weeks of intervention were observed in Con group, WBV group, SIM group, and WBV + SIM group.

Fig. 8

Immunofluorescence detection of BMP2 and SOD2 demonstrates that BMP2 and SOD2 expression in the contralateral femoral epiphysis WBV plus SIM treatment maximally increases BMP2 and SOD2 expression in the contralateral femoral epiphysis. A. Representative images of BMP2 and SOD2 immunofluorescence detection taken at 200 x original magnification in Con group, WBV group, SIM group, and WBV + SIM group. Bar = 5 μm. B. Quantitative results of BMP2 and SOD2 immunofluorescence mean intensity in 0.42 mm² of epiphyseal bone tissue measured per section per animal for each group. N = 5.

Fig. 9

The mRNA levels of Runx2, RANKL, and OPG in the VIO region were obtained from different groups. The values for each were normalized to GAPDH expression. Subsequently, the control values were standardized to be equal to 1, and all other groups were compared in terms of fold difference from the control.