title: Survival of the Apical Papilla and Its Resident Stem Cells in a Case of Advanced Pulpal Necrosis and Apical Periodontitis.
abstract: BACKGROUND
  Apical papilla represents a source of an enriched mesenchymal stem cell (MSC) population (stem cells of the apical papilla [SCAPs]) that modulates root development and may participate in regenerative endodontic procedures in immature teeth with pulp necrosis. The characteristics and phenotype of this tissue in the presence of inflammation are largely unknown. The purpose of this study was to characterize a human apical papilla sample that was isolated from an immature tooth with pulp necrosis and apical periodontitis.
  
  
  METHODS
  Inflamed periapical tissue that included part of the apical papilla (apical papilla clinical sample [CS]) was collected from an immature mandibular premolar previously diagnosed with pulp necrosis and apical periodontitis during an apexification procedure. Harvested cells from this tissue (SCAP CS) were compared with inflamed periapical progenitor cells (IPAPCs) and normal SCAP (SCAP-RP89) in flow cytometry and quantitative osteogenesis experiments. Part of the issue was further processed for immunohistochemistry and compared with apical papilla and coronal pulp sections from normal immature teeth as well as inflamed periapical tissues from mature teeth.
  
  
  RESULTS
  Similar to SCAP-RP89, 96.6% of the SCAP CS coexpressed the MSC markers CD73, CD90, and CD105, whereas only 66.3% of IPAPCs coexpressed all markers. The SCAP CS showed a significantly greater mineralization potential than both SCAP-RP89 and IPAPCs. Finally, immunohistochemical analysis revealed moderate infiltration of cells expressing the inflammatory markers CD45/68 in the apical papilla CS and prominent CD24, CD105, and von Willebrand factor expression.
  
  
  CONCLUSIONS
  Under inflammatory conditions, human apical papilla was found moderately inflamed with retained SCAP vitality and stemness and increased osteogenic and angiogenesis potential.
authors.affiliation: Department of Endodontics, University of Washington, Seattle, Washington; Department of Endodontics, University of Texas Health Science Center at San Antonio, San Antonio, Texas.
authors.forename: Vanessa
authors.initials: V
authors.lastname: Chrepa
authors.affiliation: Department of Endodontics, University of Texas Health Science Center at San Antonio, San Antonio, Texas.
authors.forename: Brandon
authors.initials: B
authors.lastname: Pitcher
authors.affiliation: Department of Endodontics, University of Texas Health Science Center at San Antonio, San Antonio, Texas; University of Colorado School of Dental Medicine, Aurora, Colorado.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Henry
authors.affiliation: Department of Endodontics, University of Texas Health Science Center at San Antonio, San Antonio, Texas. Electronic address: Diogenes@uthscsa.edu.
authors.forename: Anibal
authors.initials: A
authors.lastname: Diogenes
mesh_terms: D001641:Bicuspid / Q000166:cytology / Q000473:pathology; D002648:Child; D003771:Dental Papilla / Q000166:cytology* / Q000473:pathology; D003790:Dental Pulp Necrosis / Q000473:pathology*; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D059630:Mesenchymal Stem Cells / Q000166:cytology* / Q000502:physiology; D018613:Microscopy, Confocal; D010485:Periapical Periodontitis / Q000473:pathology*; D013234:Stem Cells / Q000166:cytology / Q000502:physiology; D019227:Tooth Apex / Q000166:cytology* / Q000473:pathology
keywords: Apical papilla survival; apical periodontitis; characterization; periapical inflammation; regenerative endodontics; stem cell; stem cells of the apical papilla