title: In vivo differentiation of human periodontal ligament cells leads to formation of dental hard tissue.
abstract: OBJECTIVE
  Following trauma, periodontal disease, or orthodontic tooth movement, residual periodontal ligament (PDL) cells at the defect site are considered mandatory for successful regeneration of the injured structures. Recent developments in tissue engineering focus, as one pillar, on the transplantation of PDL cells to support periodontal regeneration processes. Here, we examined the ability of osteogenically predifferentiated PDL cells to undergo further osteoblastic or cementoblastic differentiation and to mineralize their extracellular matrix when transplanted in an in vivo microenvironment.
  
  
  METHODS
  Using collagen sponges as carriers, osteogenically predifferentiated human PDL cells were transplanted subcutaneously into six immunocompromised CD-1® nude mice. Following explantation after 28 days, osteogenic and cementogenic marker protein expression was visualized immunohistochemically.
  
  
  RESULTS
  After 28 days, transplanted PDL cells revealed both cellular, cytoplasmatic and extracellular immunoreactivity for the chosen markers alkaline phosphatase, osteopontin, PTH-receptor 1, and osteocalcin. Specific osteogenic and cementoblastic differentiation was demonstrated by RUNX2 and CEMP1 immunoreactivity. Early stages of mineralization were demonstrated by calcium and phosphate staining.
  
  
  CONCLUSIONS
  Our results reinforce the previously published reports of PDL cell mineralization in vivo and further demonstrate the successful induction of specific osteogenic and cementogenic differentiation of transplanted human PDL cells in vivo. These findings reveal promising possibilities for supporting periodontal remodeling and regeneration processes with PDL cells being potential target cells with which to influence the process of orthodontically induced root resorption.
authors.affiliation: Department of Orthodontics, University of Bonn, Welschnonnenstr. 17, 53111, Bonn, Germany, michael.wolf@ukb.uni-bonn.de.
authors.forename: M
authors.initials: M
authors.lastname: Wolf
authors.forename: S
authors.initials: S
authors.lastname: Lossdörfer
authors.forename: N
authors.initials: N
authors.lastname: Abuduwali
authors.forename: R
authors.initials: R
authors.lastname: Meyer
authors.forename: S
authors.initials: S
authors.lastname: Kebir
authors.forename: W
authors.initials: W
authors.lastname: Götz
authors.forename: A
authors.initials: A
authors.lastname: Jäger
mesh_terms: D000293:Adolescent; D000818:Animals; D001861:Bone Regeneration / Q000502:physiology; D002454:Cell Differentiation; D002478:Cells, Cultured; D002648:Child; D005260:Female; D005347:Fibroblasts / Q000166:cytology* / Q000502:physiology* / Q000637:transplantation; D006801:Humans; D008297:Male; D051379:Mice; D008819:Mice, Nude; D010012:Osteogenesis / Q000502:physiology*; D010513:Periodontal Ligament / Q000166:cytology* / Q000502:physiology; D023822:Tissue Engineering / Q000379:methods; D014070:Tooth / Q000166:cytology* / Q000254:growth & development*