title: High-throughput gene expression analysis in bone healing around titanium implants by DNA microarray.
abstract: OBJECTIVE
  Bone generation occurs around titanium implants; however, its underlying mechanisms are relatively unknown. We attempt to identify gene transcripts specifically upregulated in in vivo bone healing with titanium implants using DNA microarray.
  
  
  METHODS
  Titanium implants were placed into rat femurs, and total RNA was extracted from the implant-associated tissue at weeks 1, 2 and 4 of healing. As a control, RNA was extracted from the tissue undergoing osteotomy healing. The RNA samples were hybridized onto oligo DNA microarray.
  
  
  RESULTS
  Most of the 20,000 genes tested were expressed similarly in both the implant- and osteotomy-healing groups. Eighty-six genes were upregulated (>2-fold) in the implant-healing group compared with the osteotomy-healing group in at least one time point of healing. Twelve genes were upregulated in the implant healing at week 2 and earlier, while 31 genes were upregulated at week 2 and later. Only one gene was upregulated specifically at week 1, while three genes were consistently upregulated from weeks 1 to 4. The upregulated genes included collagenous and non-collagenous extracellular matrix (ECM)-related genes, proteoglycans and bone resorption-related genes. Pathway analysis revealed the involvement of ECM and receptor interaction in implant healing.
  
  
  CONCLUSIONS
  This study provides evidence that a set of gene transcripts is upregulated in the implant healing over the osteotomy healing, which seems to represent the coordinated biological events of long-lasting osteogenesis and bone remodeling required for osseointegration. Further studies are needed to identify the significance and biological roles of the transcripts in osseointegration. Proven reliability and usefulness of microarray technology should encourage future approaches to develop a high-throughput molecular assessment for osseointegration capacity of new implant surfaces.
authors.affiliation: Department of Prosthodontics, Aichi-Gakuin University School of Dentistry, Nagoya, Japan.
authors.forename: Norinaga
authors.initials: N
authors.lastname: Kojima
authors.forename: Shogo
authors.initials: S
authors.lastname: Ozawa
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Miyata
authors.forename: Hideki
authors.initials: H
authors.lastname: Hasegawa
authors.forename: Yoshinobu
authors.initials: Y
authors.lastname: Tanaka
authors.forename: Takahiro
authors.initials: T
authors.lastname: Ogawa
mesh_terms: D000818:Animals; D001672:Biocompatible Materials; D003758:Dental Implantation, Endosseous / Q000379:methods*; D015921:Dental Implants; D015870:Gene Expression / Q000235:genetics*; D008297:Male; D020411:Oligonucleotide Array Sequence Analysis / Q000379:methods*; D016348:Osseointegration / Q000235:genetics*; D012313:RNA / Q000032:analysis; D051381:Rats; D017208:Rats, Wistar; D014025:Titanium; D015854:Up-Regulation / Q000235:genetics
chemical_list: D001672:Biocompatible Materials; D015921:Dental Implants; D012313:RNA; D014025:Titanium