Effect on bone healing by the application of low intensity pulsed ultrasound after injection of adipose tissue-derived stem cells at the implantation of titanium implant in the tibia of diabetes-induced rat

Introduction: This study examined the effect of the application of low intensity pulsed ultrasound on bone healing after an injection of adipose tissue- derived stem cells (ADSCs) during the implantation of a titanium implant in the tibia of diabetes-induced rats. Materials and Methods: Twelve Sprague-Dawely rats were used. After inducing diabetes, the ADSCs were injected into the hole for the implant. Customized screw type implants, 2.0 mm in diameter and 3.5. in length, were implanted in both the tibia of the diabetes-induced rats. After implantation, LIPUS was applied with parameters of 3 MHz, 40 mW/cm(2), and 10 minutes for 7 days to the left tibiae (experimental group) of the diabetesinduced rats. The right tibiae in each rat were used in the control group. At 1, 2 and 4 week rats were sacrificed, and the bone tissues of both tibia were harvested. The bone tissues of the three rats in each week were used for bone-to-implant contact (BIC) and bone area (BA) analyses and the bone tissues of one rat were used to make sagittal serial sections. Results: In histomorphometric analyses, the BIC in the experimental and control group were respectively, 39.00 +/- 18.17% and 42.87 +/- 9.27% at 1 week, 43.74 +/- 6.83% and 32.27 +/- 6.00% at 2 weeks, and 32.62 +/- 11.02% and 47.10 +/- 9.77% at 4 weeks. The BA in experimental and control group were respectively, 37.28 +/- 3.68% and 31.90 +/- 2.84% at 1 week, 20.62 +/- 2.47% and 15.64 +/- 2.69% at 2 weeks, and 11.37 +/- 4.54% and 17.69 +/- 8.77% at 4 weeks. In immunohistochemistry analyses, Osteoprotegerin expression was strong at 1 and 2 weeks in the experimental group than the control group. Receptor activator of nuclear factor kB ligand expression showed similar staining at each week in the experimental and control group. Conclusion: These results suggest that the application of low intensity pulsed ultrasound after an injection of adipose tissue-derived stem cells during the implantation of titanium implants in the tibia of diabetes-induced rats provided some positive effect on bone regeneration at the early stage after implantation. On the other hand, this method is unable to increase the level of osseointegration and bone regeneration of the implant in an uncontrolled diabetic patient.