title: The effect of hydrophilic titanium surface modification on macrophage inflammatory cytokine gene expression.
abstract: OBJECTIVE
  Chemical modification of microrough titanium dental implants to produce a hydrophilic surface with increased wettability and improved surface energy has been demonstrated clinically to achieve superior bone wound healing and osseointegration compared to that achieved with a microrough titanium surface alone. As the recruitment of the necessary osseoinductive precursors involved in bone wound healing and osseointegration to the wound site is facilitated by the action of cytokines, this study sought to determine the in vitro effect of hydrophilic surface modification on the expression of pro-inflammatory cytokines from adherent macrophages.
  
  
  METHODS
  The surface topography and composition of the titanium surfaces was characterized by scanning electron microscopy and X-ray photoelectron spectroscopy. Macrophage attachment and proliferation was assessed using an MTT assay. The expression of 84 pro-inflammatory cytokines and chemokines by adherent RAW 264.7 cells, a murine leukaemic monocyte cell line, was assessed by PCR array after 24 h culture on either smooth polished, sand-blasted acid-etched (SLA) or hydrophilic-modified SLA (SLActive) titanium surfaces.
  
  
  RESULTS
  Following 24 h culture on titanium, surface microroughness activated pro-inflammatory cytokine gene transcription in RAW 264.7 cells. Although there was no significant difference in the degree of cellular attachment or proliferation of RAW 264.7 cells to the different titanium surfaces, by 24 h the hydrophilic surface elicited a gene expression profile with significant down-regulation of the key pro-inflammatory cytokines Tnfα, IL-1α, IL-1β and the chemokine Ccl-2.
  
  
  CONCLUSIONS
  Down-regulation of the expression of pro-inflammatory cytokine genes may thus modulate the inflammatory response and may facilitate the enhanced bone wound healing and osseointegration observed clinically using implants with a microrough hydrophilic surface.
authors.affiliation: School of Dentistry and Oral Health, Centre for Medicine and Oral Health, Griffith University, Gold Coast Campus, Gold Coast, QLD, Australia.
authors.forename: Stephen
authors.initials: S
authors.lastname: Hamlet
authors.forename: Mohammed
authors.initials: M
authors.lastname: Alfarsi
authors.forename: Roy
authors.initials: R
authors.lastname: George
authors.forename: Saso
authors.initials: S
authors.lastname: Ivanovski
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D002460:Cell Line; D049109:Cell Proliferation; D016207:Cytokines / Q000235:genetics* / Q000378:metabolism*; D015536:Down-Regulation; D020869:Gene Expression Profiling; D008264:Macrophages / Q000378:metabolism*; D051379:Mice; D008855:Microscopy, Electron, Scanning; D056951:Photoelectron Spectroscopy; D013499:Surface Properties; D014025:Titanium; D014158:Transcription, Genetic; D017155:Wettability
chemical_list: D016207:Cytokines; D014025:Titanium