title: Cells isolated from inflamed periapical tissue express mesenchymal stem cell markers and are highly osteogenic.
abstract: BACKGROUND
  We previously reported the presence of mesenchymal stem/progenitor cells (MSCs) in inflamed pulp tissue. Here we asked whether MSCs also exist in inflamed periapical tissues resulting from endodontic infection. The objectives of this study were to detect the expression of MSC markers in periapical inflammatory tissues and to characterize isolated cells from these tissues.
  
  
  METHODS
  Human periapical inflammatory tissues were collected and processed to detect MSC marker expression by immunohistochemistry. Cells were isolated and tested for cell surface marker expression by using flow cytometry and examined for multiple differentiation potential into osteogenic and adipogenic pathways. In vivo formation of mineralized tissues was assessed in a mouse model.
  
  
  RESULTS
  Immunohistochemistry showed positive staining for MSC markers STRO-1, CD90, and CD146. Isolated cells at passage 0 appeared as typical fibroblastic cells, and a few cells formed colony-forming unit-fibroblasts (CFU-Fs). After passaging, the CFU-F forming ability diminished dramatically, and the population doubling was up to 26. Flow cytometry data showed that these cells at passage 2 expressed low levels of STRO-1 and CD146 and moderate to high levels of CD90, CD73, and CD105. At passage 6, the levels of these markers decreased. When incubated in specific differentiation medium, cells demonstrated a strong osteogenic but weak adipogenic capacity. After in vivo cell transplantation, mineralized tissues formed in immunocompromised mice.
  
  
  CONCLUSIONS
  Human periapical inflammatory tissues expressed MSC markers, suggesting the presence of MSCs. Isolated cells exhibited typical mesenchymal cell immunophenotype with a capacity to form mineralized matrix in vitro and in vivo.
authors.affiliation: Department of Endodontics, Henry M. Goldman School of Dental Medicine, Boston University, Boston, Massachusetts 02118, USA.
authors.forename: James
authors.initials: J
authors.lastname: Liao
authors.forename: Mohammed
authors.initials: M
authors.lastname: Al Shahrani
authors.forename: Mey
authors.initials: M
authors.lastname: Al-Habib
authors.forename: Toshinori
authors.initials: T
authors.lastname: Tanaka
authors.forename: George T-J
authors.initials: GT
authors.lastname: Huang
mesh_terms: D015720:5'-Nucleotidase; D050156:Adipogenesis; D000293:Adolescent; D000328:Adult; D000368:Aged; D000818:Animals; D015703:Antigens, CD; D000954:Antigens, Surface; D051929:CD146 Antigen; D002454:Cell Differentiation; D000071063:Endoglin; D005347:Fibroblasts / Q000637:transplantation; D005434:Flow Cytometry; D058851:GPI-Linked Proteins; D006801:Humans; D016130:Immunophenotyping; D059630:Mesenchymal Stem Cells; D051379:Mice; D008875:Middle Aged; D010012:Osteogenesis; D010485:Periapical Periodontitis / Q000473:pathology*; D010486:Periapical Tissue / Q000166:cytology / Q000473:pathology; D061251:Primary Cell Culture; D011956:Receptors, Cell Surface; D018800:Thy-1 Antigens; D055815:Young Adult
chemical_list: D015703:Antigens, CD; D000954:Antigens, Surface; D051929:CD146 Antigen; C064206:ENG protein, human; D000071063:Endoglin; D058851:GPI-Linked Proteins; C497902:MCAM protein, human; D011956:Receptors, Cell Surface; C525591:STRO-1 antigen, human; D018800:Thy-1 Antigens; D015720:5'-Nucleotidase; C548241:NT5E protein, human