Early molecular assessment of osseointegration in humans

To determine the early temporal-wide genome transcription regulation by the surface topography at the bone-implant interface of implants bearing microroughened or superimposed nanosurface topology.

Four commercially pure titanium implants (2.2 × 5.0 mm) with either a moderately roughened surface (TiOblast) or super-imposed nanoscale topography (Osseospeed) were placed (n = 2/surface) in edentulous sites of eleven systemically healthy subjects and subsequently removed after 3 and 7 days. Total RNA was isolated from cells adherent to retrieved implants. A whole-genome microarray using the Affymetrix Human gene 1.1 ST Array was used to describe the gene expression profiles that were differentially regulated by the implant surfaces.

There were no significant differences when comparing the two implant surfaces at each time point. However, the microarray identified several genes that were differentially regulated at day 7 vs. day 3 for both implant surfaces. Functionally relevant categories related to the extracellular matrix (ECM), collagen fibril organization, and angiogenesis were upregulated at both surfaces (day7 vs. day3). Abundant upregulation of several differential markers of alternative activated macrophages was observed (e.g., MRC1, MSR1, MS4A4A, SLC38A6, and CCL18). The biological processes involved with the inflammatory/immune response gene expression were concomitantly downregulated.

Gene regulation implicating collagen fibrillogenesis and ECM organization as well as the inflammatory/immune responses involving the alternative activated pathway are observed in implant adherent cells at early (3-7 days) after implantation. These gene expression events may indicate a pivotal role of collagen fibrillogenesis as well as immunomodulation in altering bone accrual and biomechanical physical properties of the implant-bone interface.