title: Expression of circadian core clock genes in fibroblasts of human gingiva and periodontal ligament is modulated by L-Mimosine and hypoxia in monolayer and spheroid cultures.
abstract: OBJECTIVE
  The circadian clock is involved in a plethora of physiological processes including bone formation and tooth development. While expression of circadian core clock genes was observed in various tissues, their role in the periodontium is unclear. We hypothesized that periodontal cells express circadian core clock genes and that their levels are modulated by hypoxia mimetic agents and hypoxia.
  
  
  METHODS
  Fibroblasts of human gingiva (GF) and periodontal ligament (PDLF) in monolayer and spheroid cultures were treated with the hypoxia mimetic agent L-Mimosine (L-MIM) or hypoxia. Reverse transcription and quantitative PCR were performed to assess the impact on mRNA levels of the circadian core clock genes Clock, Bmal1, Cry1, Cry2, Per1, Per2, and Per3.
  
  
  RESULTS
  GF and PDLF expressed Clock, Bmal1, Cry1, Cry2, Per1, Per2, and Per3 in monolayer and spheroid cultures. In monolayer cultures, L-MIM significantly reduced Clock, Cry2, and Per3 mRNA expression in GF and Clock, Cry1, Cry2, Per1, and Per3 in PDLF. Hypoxia significantly reduced Clock, Cry2, and Per3 in GF and Cry1, Cry2, and Per3 in PDLF. In spheroid cultures, L-MIM significantly decreased Clock, Cry1, Cry2, and Per3 in GF and PDLF. Hypoxia significantly decreased Cry2 and Per3 in GF and Clock and Per3 in PDLF.
  
  
  CONCLUSIONS
  GF and PDLF express circadian core clock genes. The hypoxia mimetic agent L-MIM and hypoxic conditions can decrease the expression of Clock, Cry1-2 and Per1 and Per3. The specific response depends on cell type and culture model. Future studies will show how this effect contributes to periodontal health and disease.
authors.affiliation: Department of Conservative Dentistry and Periodontology, School of Dentistry, Medical University of Vienna, Vienna, Austria; Austrian Cluster for Tissue Regeneration, Vienna, Austria.
authors.forename: Klara
authors.initials: K
authors.lastname: Janjić
authors.affiliation: Department of Conservative Dentistry and Periodontology, School of Dentistry, Medical University of Vienna, Vienna, Austria; Austrian Cluster for Tissue Regeneration, Vienna, Austria.
authors.forename: Christoph
authors.initials: C
authors.lastname: Kurzmann
authors.affiliation: Department of Conservative Dentistry and Periodontology, School of Dentistry, Medical University of Vienna, Vienna, Austria; Austrian Cluster for Tissue Regeneration, Vienna, Austria.
authors.forename: Andreas
authors.initials: A
authors.lastname: Moritz
authors.affiliation: Department of Conservative Dentistry and Periodontology, School of Dentistry, Medical University of Vienna, Vienna, Austria; Austrian Cluster for Tissue Regeneration, Vienna, Austria. Electronic address: hermann.agis@meduniwien.ac.at.
authors.forename: Hermann
authors.initials: H
authors.lastname: Agis
mesh_terms: D056930:ARNTL Transcription Factors / Q000235:genetics / Q000378:metabolism; D002478:Cells, Cultured; D057906:Circadian Clocks / Q000235:genetics* / Q000502:physiology*; D056931:Cryptochromes / Q000235:genetics / Q000378:metabolism; D005347:Fibroblasts / Q000378:metabolism*; D005786:Gene Expression Regulation; D005881:Gingiva / Q000378:metabolism*; D006801:Humans; D000860:Hypoxia / Q000378:metabolism*; D008898:Mimosine / Q000378:metabolism*; D056950:Period Circadian Proteins / Q000235:genetics / Q000378:metabolism; D010513:Periodontal Ligament / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction
chemical_list: D056930:ARNTL Transcription Factors; C538960:BMAL1 protein, human; C538963:CRY1 protein, human; C538966:CRY2 protein, human; D056931:Cryptochromes; C539022:PER1 protein, human; C421902:PER2 protein, human; C512644:PER3 protein, human; D056950:Period Circadian Proteins; D012333:RNA, Messenger; D008898:Mimosine
keywords: Circadian clock; Hypoxia; Hypoxia mimetic agents; Microtissue; Periodontics