The involvement of platelet-derived growth factor receptors and insulin-like growth factor-I receptors signaling during mineralized nodule formation by human periodontal ligament cells.
OBJECTIVE
Periodontal ligament cells are regarded to have the capacity to differentiate into cementoblasts or osteoblasts, and are capable of forming a mineralized nodule in vitro. However, the precise mechanisms are unclear. Here we evaluated the possible involvement of growth factor receptors, such as the platelet-derived growth factor receptor (PDGFR), insulin-like growth factor-I receptor (IGF-IR), and epidermal growth factor receptor (EGFR) on periodontal ligament cells and their ligands during periodontal ligament cells differentiation in vitro.


METHODS
Human periodontal ligament cells were differentiated via culturing in the presence of dexamethasone, ascorbic acid, and beta-glycerophosphate for mineralized nodule formation, characterized by von Kossa staining. Expressions of receptors and their ligands were analyzed by flow cytometry/reverse transcription-polymerase chain reaction.


RESULTS
During the differentiation, PDGFR-alpha was held at a lower level compared with the control. PDGFR-beta, however, was maintained at a slightly higher level that was reversed to the control level when mineralized nodules formed. In contrast, IGF-IR and EGFR were not substantially different from the control. The mineralized nodule formation was strongly inhibited by a PDGFR kinase blocker (AG1295 and AG1296), partially inhibited by an IGF-IR kinase blocker (I-Ome-AG538 and AG1024), and not inhibited by an EGFR kinase blocker (AG99). PDGF-A, PDGF-C, PDGF-D, IGF-I, and IGF-II, but not PDGF-B, were expressed on the control as well as dexamethasone/ascorbic acid-treated periodontal ligament cells during mineralized nodule formation; however, the pattern of their expressions was quite different.


CONCLUSIONS
These findings suggest that a pathway of PDGFs/PDGFR and IGFs/IGF-IR on periodontal ligament cells are involved during mineralized nodule formation, and that PDGFs and IGFs expressed by periodontal ligament cells may contribute to the formation.
Nemoto
Eiji
E
Division of Periodontology and Endodontology, Tohoku University School of Graduate Dentistry, Sendai, Japan.
Shimonishi
Mitsuru
M
Nitta
Yasutaka
Y
Shimauchi
Hidetoshi
H
D000293:Adolescent; D000328:Adult; D000704:Analysis of Variance; D001205:Ascorbic Acid / Q000494:pharmacology; D019898:Autocrine Communication; D002454:Cell Differentiation / Q000187:drug effects; D049109:Cell Proliferation; D002478:Cells, Cultured; D003907:Dexamethasone / Q000494:pharmacology; D066246:ErbB Receptors / Q000037:antagonists & inhibitors / Q000378:metabolism; D005434:Flow Cytometry; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D008875:Middle Aged; D010513:Periodontal Ligament / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D010982:Platelet-Derived Growth Factor / Q000378:metabolism*; D047428:Protein Kinase Inhibitors / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis; D017526:Receptor, IGF Type 1 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D017479:Receptors, Platelet-Derived Growth Factor / Q000037:antagonists & inhibitors / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014074:Tooth Calcification / Q000502:physiology*
D010982:Platelet-Derived Growth Factor; D047428:Protein Kinase Inhibitors; D012333:RNA, Messenger; D007334:Insulin-Like Growth Factor I; D003907:Dexamethasone; D066246:ErbB Receptors; D017526:Receptor, IGF Type 1; D017479:Receptors, Platelet-Derived Growth Factor; D001205:Ascorbic Acid