Positive Modulation of Osteogenesis- and Osteoclastogenesis-related Gene Expression with Strontium-containing Microstructured Ti Implants in Rabbit Cancellous Bone

This study investigated the in vivo osteoblast and osteoclast gene expression in the peri-implant bone tissue of the strontium (Sr)-incorporated microstructured Ti implants (SLA/Sr) in order to evaluate whether local Sr delivery to the implant surface as in the form of SrTiO(3) also exerts original bone healing enhancement effect of Sr that take place through the dual modes of action of a stimulation of osteogenesis and an inhibition of osteoclastogenesis. The in vivo mRNA expression of osteoblast- and osteoclast-related genes in the peri-implant bone and removal torque forces of the SLA/Sr implants were compared with a chemically modified super-hydrophilic SLA implants (SLActive®) in rabbit cancellous bone after 2 weeks of implantation. There was no significant difference in the removal torque values between the two groups. Both the torque-tested SLA/Sr and SLActive implants exhibited a considerable quantity of bone attached to the surface. Real-time PCR analysis revealed notably increased mRNA expression of osteoblast genes (Runx2, osterix and osteocalcin) in the peri-implant bone of the SLA/Sr implants compared with the SLActive implants (p < 0.05), whereas osteoclast phenotype gene (TRAP) expression was markedly decreased in the SLA/Sr implant (p < 0.05). The results at the molecular level suggest that local Sr delivery as in the form of the Sr-incorporated Ti oxide layer favors early osseointegration of microrough Ti implants via a positive modulation of bone healing, that is, a promotion of osteoblast differentiation and suppression of osteoclastogenesis, in the bone-implant interface of cancellous bone.