title: Hypoxia modulates the differentiation potential of stem cells of the apical papilla.
abstract: BACKGROUND
  Stem cells from the apical papilla (SCAP) are a population of mesenchymal stem cells likely involved in regenerative endodontic procedures and have potential use as therapeutic agents in other tissues. In these situations, SCAP are exposed to hypoxic conditions either within a root canal devoid of an adequate blood supply or in a scaffold material immediately after implantation. However, the effect of hypoxia on SCAP proliferation and differentiation is largely unknown. Therefore, the objective of this study was to evaluate the effect of hypoxia on the fate of SCAP.
  
  
  METHODS
  SCAP were cultured under normoxia (21% O2) or hypoxia (1% O2) in basal or differentiation media. Cellular proliferation, gene expression, differentiation, and protein secretion were analyzed by live imaging, quantitative reverse-transcriptase polymerase chain reaction, cellular staining, and enzyme-linked immunosorbent assay, respectively.
  
  
  RESULTS
  Hypoxia had no effect on SCAP proliferation, but it evoked the up-regulation of genes specific for osteogenic differentiation (runt-related transcription factor 2, alkaline phosphatase, and transforming growth factor-β1), neuronal differentiation ( 2'-3'-cyclic nucleotide 3' phosphodiesterase, SNAIL, neuronspecific enolase, glial cell-derived neurotrophic factor and neurotrophin 3), and angiogenesis (vascular endothelial growth factor A and B). Hypoxia also increased the sustained production of VEGFa by SCAP. Moreover, hypoxia augmented the neuronal differentiation of SCAP in the presence of differentiation exogenous factors as detected by the up-regulation of NSE, VEGFB, and GDNF and the expression of neuronal markers (PanF and NeuN).
  
  
  CONCLUSIONS
  This study shows that hypoxia induces spontaneous differentiation of SCAP into osteogenic and neurogenic lineages while maintaining the release of the proangiogenic factor VEGFa. This highlights the potential of SCAP to promote pulp-dentin regeneration. Moreover, SCAP may represent potential therapeutic agents for neurodegenerative conditions because of their robust differentiation potential.
authors.affiliation: Pharmaceutics and Drug Delivery Unit, Louvain Drug Research Institute, Université Catholique de Louvain, Brussels, Belgium. Electronic address: julie.vanacker@uclouvain.be.
authors.forename: Julie
authors.initials: J
authors.lastname: Vanacker
authors.affiliation: Pharmaceutics and Drug Delivery Unit, Louvain Drug Research Institute, Université Catholique de Louvain, Brussels, Belgium.
authors.forename: Aiswarya
authors.initials: A
authors.lastname: Viswanath
authors.affiliation: Pharmaceutics and Drug Delivery Unit, Louvain Drug Research Institute, Université Catholique de Louvain, Brussels, Belgium.
authors.forename: Pauline
authors.initials: P
authors.lastname: De Berdt
authors.affiliation: Metabolism and Nutrition Research Group, WELBIO (Walloon Excellence in Life Sciences and BIOtechnology), Louvain Drug Research Institute, Université catholique de Louvain, Brussels, Belgium.
authors.forename: Amandine
authors.initials: A
authors.lastname: Everard
authors.affiliation: Metabolism and Nutrition Research Group, WELBIO (Walloon Excellence in Life Sciences and BIOtechnology), Louvain Drug Research Institute, Université catholique de Louvain, Brussels, Belgium.
authors.forename: Patrice D
authors.initials: PD
authors.lastname: Cani
authors.affiliation: Pole of Pharmacology, Institute of Experimental and Clinical Research, Université Catholique de Louvain, Brussels, Belgium.
authors.forename: Caroline
authors.initials: C
authors.lastname: Bouzin
authors.affiliation: Pole of Pharmacology, Institute of Experimental and Clinical Research, Université Catholique de Louvain, Brussels, Belgium.
authors.forename: Olivier
authors.initials: O
authors.lastname: Feron
authors.affiliation: University of Texas Health Science Center at San Antonio, San Antonio, Texas.
authors.forename: Anibal
authors.initials: A
authors.lastname: Diogenes
authors.affiliation: Pharmaceutics and Drug Delivery Unit, Louvain Drug Research Institute, Université Catholique de Louvain, Brussels, Belgium.
authors.forename: Julian G
authors.initials: JG
authors.lastname: Leprince
authors.affiliation: Pharmaceutics and Drug Delivery Unit, Louvain Drug Research Institute, Université Catholique de Louvain, Brussels, Belgium.
authors.forename: Anne
authors.initials: A
authors.lastname: des Rieux
mesh_terms: D015087:2',3'-Cyclic-Nucleotide Phosphodiesterases / Q000032:analysis; D050156:Adipogenesis / Q000502:physiology; D000293:Adolescent; D000469:Alkaline Phosphatase / Q000032:analysis; D018929:Cell Culture Techniques; D002454:Cell Differentiation / Q000502:physiology; D015687:Cell Hypoxia / Q000502:physiology; D049109:Cell Proliferation; D050659:Core Binding Factor Alpha 1 Subunit / Q000032:analysis; D003470:Culture Media; D003771:Dental Papilla / Q000166:cytology*; D003782:Dental Pulp / Q000166:cytology*; D005260:Female; D051100:Glial Cell Line-Derived Neurotrophic Factor / Q000032:analysis; D006801:Humans; D059630:Mesenchymal Stem Cells / Q000502:physiology*; D055495:Neurogenesis / Q000502:physiology; D020933:Neurotrophin 3 / Q000032:analysis; D010012:Osteogenesis / Q000502:physiology; D010751:Phosphopyruvate Hydratase / Q000032:analysis; D000071250:Snail Family Transcription Factors; D014157:Transcription Factors / Q000032:analysis; D053773:Transforming Growth Factor beta1 / Q000032:analysis; D042461:Vascular Endothelial Growth Factor A / Q000032:analysis; D042561:Vascular Endothelial Growth Factor B / Q000032:analysis
chemical_list: D050659:Core Binding Factor Alpha 1 Subunit; D003470:Culture Media; C495039:GDNF protein, human; D051100:Glial Cell Line-Derived Neurotrophic Factor; D020933:Neurotrophin 3; C493709:RUNX2 protein, human; D000071250:Snail Family Transcription Factors; D014157:Transcription Factors; D053773:Transforming Growth Factor beta1; C467484:VEGFA protein, human; C467485:VEGFB protein, human; D042461:Vascular Endothelial Growth Factor A; D042561:Vascular Endothelial Growth Factor B; D000469:Alkaline Phosphatase; D015087:2',3'-Cyclic-Nucleotide Phosphodiesterases; D010751:Phosphopyruvate Hydratase
keywords: Angiogenic factor; apical papilla; dental stem cells; gene expression; hypoxia; neurodifferentiation; regenerative endodontics; stem cells from the apical papilla