Promoting osteointegration effect of Cu-alloyed titanium in ovariectomized rats

Abstract

Osteoporosis is a common skeletal disease making patients be prone to the osteoporotic fracture. However, the clinical implants made of titanium and its alloys with a poor osseointegration need a long time for healing and easily to loosening. Thus, a new class of Cu-alloyed titanium (TiCu) alloys with excellent mechanical properties and bio-functionalization has been developed. In this study, the osteoporosis modeled rats were used to study the osteointegration effect and underlying mechanism of TiCu. The results showed that after implantation for 4 weeks, TiCu alloy could promote the reconstruction of vascular network around the implant by up-regulating vascular endothelial growth factor expression. After 8 weeks, it could further promote the proliferation and differentiation of osteoblasts, mineralization and deposition of collagens, and then significantly increasing bone mineral density around the implant. In conclusion, TiCu alloy would enhance the fixation stability, accelerate the osteointegration, and thus reduce the risk of aseptic loosening during the long-term implantation in the osteoporosis environment. This study was the first to report the role and mechanism of a Cu-alloyed metal in promoting osteointegration in osteoporosis environment, which provides a new attractive support for the improvement of future clinical applications of Cu-alloyed antibacterial titanium alloys.

Keywords: copper-alloyed titanium alloy; implant; osseointegration; osteoporosis; vascularization.

Figure 1.

General background information: (A) dimension of implant screw; (B) surgery procedure and image of the uterus; (C and D) body weight; and (E and F) uterine weight after surgical implantation for 4 and 8 weeks. Data were expressed as mean±SD. n = 7 for Week 4 group, and n = 8 for Week 8 group in panels (D) and (F). ^***P < 0.001

Figure 2.

Micro-CT analyses of bone vessels after 4 weeks of screw implantation: (A) micro-CT scan modeling; (B) ROI for analysis; and (C–E) quantitative analysis results of volume, number and thickness distribution of blood vessels in ROI. The data were expressed as mean±SD. n = 7 in panels (C) and (E). ^*P < 0.05

Figure 3.

Micro-CT analyses of bone structure after 8 weeks of screw implantation: (A) micro-CT scans on Sham-Ti, OVX-Ti and OVX-TiCu groups, respectively; (B and J) ROI for analyses; and (C–Q) quantitative analyses of bone structure parameters. Data were expressed as mean±SD. n = 8 in panels (C) and (I). ^*P < 0.05, ^**P < 0.01, ^***P < 0.001

Figure 4.

Results of biomechanical experiment: (A and B) ultimate load of pull-out of samples after 4 and 8 weeks of screw implantations, respectively; (C and D) volumes of holes left after pulling out of screws with 4 and 8 weeks of implantations, respectively; (E) cross-head of biomechanical testing machine; and (F) ROI for analysis. Data were expressed as mean±SD. For 4 weeks n = 7, and for 8 weeks n = 8 in panels (A) to (D). ^*P < 0.05

Figure 5.

Analyses of soft tissue slices and immunohistochemical staining after 4 weeks of screw implantation: (A and B) soft tissue slices of H&E staining and Masson staining; (C) immunohistochemical staining of VEGF; (D) quantitative Tb. Ar around the screws; and (E) ratio of VEGF positive area to total bone area around the screws. Data were expressed as mean±SD. n = 7 in panels (D) and (E). ^*P < 0.05, ^***P < 0.001

Figure 6.

Analyses of hard tissue after screw implantation over 8 weeks: (A) hard tissue slices of fluorescence staining; and (B and D) quantitative analyses of OB activity. Data were expressed as mean±SD. n = 8 in panels (B) to (D). ^*P < 0.05, ^**P < 0.01

Figure 7.

Illustration on different effects of TiCu and Ti screws implanted in tibia of osteoporotic rats