title: Gene-expression analysis of cementoblasts and osteoblasts.
abstract: OBJECTIVE
  Cementum and bone are similar mineralized tissues, but cementum accumulates much more slowly than bone, does not have vasculature or innervation and does not undergo remodeling. Despite these differences, there are no well-established markers to distinguish cementoblasts from other mature mineralizing cells such as osteoblasts and odontoblasts. The purpose of this study was to assess differences in gene expression between cementoblasts and osteoblasts using gene profiling of cell populations isolated directly from osteocalcin-green fluorescent protein (OC-GFP) transgenic mice.
  
  
  METHODS
  OC-GFP reporter mice were used as they show labeling of cementoblasts, osteoblasts and odontoblasts, but not of periodontal ligament fibroblasts, within the periodontium. We sorted cells digested from the molar root surface to isolate OC-GFP(+) cementoblasts. Osteoblasts were isolated from calvarial digests. Microarray analysis was performed, and selected results were confirmed by real-time PCR and immunostaining or in situ hybridization.
  
  
  RESULTS
  Microarray analysis identified 95 genes that were expressed at least two-fold higher in cementoblasts than in osteoblasts. Our analysis indicated that the Wnt signaling pathway was differentially regulated, as were genes related to skeletal development. Real-time PCR confirmed that expression of the Wnt inhibitors Wnt inhibitory factor 1 (Wif1) and secreted frizzled-related protein 1 (Sfrp1) was elevated in cementoblasts compared with osteoblasts, and Wif1 expression was localized to the apical root region. In addition, the transcription factor BARX homeobox 1 (Barx1) was expressed at higher levels in cementoblasts, and immunohistochemistry indicated that BARX1 was expressed in apical cementoblasts and cementocytes, but not in osteoblasts or odontoblasts.
  
  
  CONCLUSIONS
  The OC-GFP mouse provides a good model for selectively isolating cementoblasts, and allowed for identification of differentially expressed genes between cementoblasts and osteoblasts.
authors.affiliation: Department of Reconstructive Sciences, School of Dental Medicine, University of Connecticut Health Center, Farmington, CT, USA.
authors.forename: B G
authors.initials: BG
authors.lastname: Matthews
authors.affiliation: Department of Reconstructive Sciences, School of Dental Medicine, University of Connecticut Health Center, Farmington, CT, USA.
authors.forename: H
authors.initials: H
authors.lastname: Roguljic
authors.affiliation: Department of Reconstructive Sciences, School of Dental Medicine, University of Connecticut Health Center, Farmington, CT, USA.
authors.forename: T
authors.initials: T
authors.lastname: Franceschetti
authors.affiliation: Department of Reconstructive Sciences, School of Dental Medicine, University of Connecticut Health Center, Farmington, CT, USA.
authors.forename: E
authors.initials: E
authors.lastname: Roeder
authors.affiliation: Department of Reconstructive Sciences, School of Dental Medicine, University of Connecticut Health Center, Farmington, CT, USA.
authors.forename: I
authors.initials: I
authors.lastname: Matic
authors.affiliation: Division of Pediatric Dentistry, Department of Craniofacial Sciences, School of Dental Medicine, University of Connecticut Health Center, Farmington, CT, USA.
authors.forename: I
authors.initials: I
authors.lastname: Vidovic
authors.affiliation: Department of Computer Science and Engineering, University of Connecticut, Storrs, CT, USA.
authors.forename: P
authors.initials: P
authors.lastname: Joshi
authors.affiliation: Division of endodontology, Department of Oral Health and Diagnostic Sciences, School of Dental Medicine, University of Connecticut Health Center, Farmington, CT, USA.|Department of Conservative Dentistry, Dental Research Institute, Seoul National University School of Dentistry, Seoul, Korea.
authors.forename: K-Y
authors.initials: KY
authors.lastname: Kum
authors.affiliation: Department of Reconstructive Sciences, School of Dental Medicine, University of Connecticut Health Center, Farmington, CT, USA.
authors.forename: I
authors.initials: I
authors.lastname: Kalajzic
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D002113:Calcification, Physiologic; D002454:Cell Differentiation / Q000235:genetics; D003739:Dental Cementum / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D016326:Extracellular Matrix Proteins / Q000494:pharmacology; D005347:Fibroblasts / Q000166:cytology; D005786:Gene Expression Regulation; D018398:Homeodomain Proteins / Q000096:biosynthesis / Q000235:genetics; D036341:Intercellular Signaling Peptides and Proteins / Q000494:pharmacology; D008565:Membrane Proteins / Q000494:pharmacology; D051379:Mice; D008822:Mice, Transgenic; D009804:Odontoblasts / Q000166:cytology; D010006:Osteoblasts / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D015675:Osteocalcin; D010513:Periodontal Ligament / Q000166:cytology; D012333:RNA, Messenger / Q000235:genetics; D014092:Tooth Root / Q000166:cytology; D014157:Transcription Factors / Q000096:biosynthesis / Q000235:genetics; D060449:Wnt Signaling Pathway / Q000187:drug effects / Q000235:genetics*; D000094742:Secreted Frizzled-Related Proteins
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D016326:Extracellular Matrix Proteins; D018398:Homeodomain Proteins; D036341:Intercellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D015675:Osteocalcin; D012333:RNA, Messenger; D014157:Transcription Factors; C095587:Barx1 protein, mouse; C485539:Sfrp1 protein, mouse; D000094742:Secreted Frizzled-Related Proteins; C118544:Wif1 protein, mouse
keywords: Wnt signaling pathway; cementoblast; gene expression; osteoblast; osteocalcin