Employing a transgenic animal model to obtain cementoblasts in vitro.
BACKGROUND
Proper formation of cementum, a mineralized tissue lining the tooth root surface, is required for development of a functional periodontal ligament. Further, the presence of healthy cementum is considered to be an important criterion for predictable restoration of periodontal tissues lost as a consequence of disease. Despite the significance of cementum to general oral health, the mechanisms controlling development and regeneration of this tissue are not well understood and research has been hampered by the lack of adequate in vitro experimental models.


METHODS
In an effort to establish cementoblast cell populations, without the trappings of a heterogeneous population containing periodontal ligament (PDL) cells, cells were obtained from the root surface of first mandibular molars of OC-TAg transgenic mice. These mice contain the SV40 large T-antigen (TAg) under control of the osteocalcin (OC) promoter. Therefore, only cells that express OC also express TAg and are immortalized in vitro. Based on results of prior in situ studies, OC is expressed by cementoblasts during root development, but not by cells within the PDL. Consequently, when populations are isolated from developing molars using collagenase/trypsin digestion, only cementoblasts, not PDL cells, are immortalized and thus, will survive in culture.


RESULTS
The resulting immortalized cementoblast population (OC/CM) expressed bone sialoprotein (BSP), osteopontin (OPN), and OC, markers selective to cells lining the root surface. These cells also expressed type I and XII collagen and type I PTH/PTHrP receptor (PTH1R). In addition to expression of genes associated with cementoblasts, OC/CM cells promoted mineral nodule formation and exhibited a PTHrP mediated cAMP response.


CONCLUSIONS
This approach for establishing cementoblasts in vitro provides a model to study cementogenesis as required to enhance our knowledge of the mechanisms controlling development, maintenance, and regeneration of periodontal tissues.
D'Errico
J A
JA
Department of Periodontics/Prevention/Geriatrics, University of Michigan, Ann Arbor 48109-1078, USA.
Berry
J E
JE
Ouyang
H
H
Strayhorn
C L
CL
Windle
J J
JJ
Somerman
M J
MJ
D000818:Animals; D000952:Antigens, Polyomavirus Transforming / Q000235:genetics; D002448:Cell Adhesion / Q000235:genetics; D002478:Cells, Cultured; D025021:Cementogenesis; D003094:Collagen / Q000235:genetics; D000242:Cyclic AMP / Q000378:metabolism; D003739:Dental Cementum / Q000166:cytology* / Q000378:metabolism / Q000502:physiology; D004195:Disease Models, Animal; D058574:Integrin-Binding Sialoprotein; D051379:Mice; D008815:Mice, Inbred Strains; D008822:Mice, Transgenic; D008903:Minerals / Q000378:metabolism; D009805:Odontogenesis / Q000502:physiology; D015675:Osteocalcin / Q000235:genetics; D053495:Osteopontin; D010281:Parathyroid Hormone / Q000235:genetics; D010750:Phosphoproteins / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics; D018016:Receptors, Parathyroid Hormone / Q000235:genetics; D012038:Regeneration; D012795:Sialoglycoproteins / Q000235:genetics; D014092:Tooth Root / Q000166:cytology / Q000502:physiology
D000952:Antigens, Polyomavirus Transforming; C546872:Ibsp protein, mouse; D058574:Integrin-Binding Sialoprotein; D008903:Minerals; D010281:Parathyroid Hormone; D010750:Phosphoproteins; D018016:Receptors, Parathyroid Hormone; D012795:Sialoglycoproteins; C506896:Spp1 protein, mouse; D015675:Osteocalcin; D053495:Osteopontin; D003094:Collagen; D000242:Cyclic AMP