Genetic effects of a titanium surface on osteoblasts: a meta-analysis.

Titanium is used worldwide to make osseointegrable devices. The favorable characteristics that make this material desirable for implantation are i) its mechanical properties and ii) its biocompatibility. The latter has been demonstrated by in vivo studies with animal models and clinical trials over a forty-year period. However, the exact genetic effect of the titanium layer on cells is still not well characterized. To detect the genetic effect of titanium surfacing on osteoblasts without porosity as a confounding variable, a meta-analysis of genetic expression profiling obtained from several titanium surfaces was performed. One hundred seventy-three genes were selected, 84 up-regulated and 95 down-regulated. Among them, the most notable were genes that participate in osteoblast differentiation and bone regeneration, such as TIMP1, PTN, and RUNX1. Titanium surfacing has i) a direct genetic effect on osteoblasts, ii) induces several bone-related genes, and iii) is relevant to the osseointegration process. These properties should be taken into consideration in separating the effect of porosity (i.e. the micro-dimension) from implant coating (i.e. the nano-dimension).