RGD-coated titanium implants stimulate increased bone formation in vivo

Numerous studies have demonstrated that peptide modified surfaces influence short- and long-term cell responses such as attachment, shape and function in vitro. These responses are mediated via cell receptors known as integri ns which bind specifically to short peptide sequences from larger proteins. Integrins transduce information to the nucleus through several cytoplasmic signalling pathways. Little is known, however, about the ability of peptid e-coated surfaces to influence cell responses in vivo. The present study wa s designed to evaluate the quality and quantity of the new bone formed in r esponse to titanium rods surface-coated with the peptide sequence Arg-Gly-A sp-Cys (RGDC) using gold-thiol chemistry and implanted in rat femurs. Histo morphometric analysis of cross-sections perpendicular to the implant long a xis showed a significantly thicker shell of new bone formed around RGD-modi fied Versus plain implants at 2 weeks (26.2 +/- 1.9 vs. 20.5 +/- 2.9 mu m; P < 0.01). A significant increase in bone thickness for RGD implants was al so observed at 4 weeks while bone surrounding controls did not change signi ficantly in thickness (32.7 +/- 4.6 vs. 22.6 +/- 4.0 mu m; P < 0.02). Mecha nical pull-out testing conducted at 4 weeks revealed the average interfacia l shear strength of peptide modified rods was 38% greater than control rods although this difference was not statistically significant. These pilot da ta suggest that an RGDC peptide coating may enhance titanium rod osseointeg ration in the rat femur. Long-term studies and evaluation of other peptides in larger animal models are warranted. (C) 1999 Elsevier Science Ltd. All rights reserved.