title: Effect of tensile force on the expression of IGF-I and IGF-I receptor in the organ-cultured rat cranial suture.
abstract: Insulin-like growth factors (IGFs) play an important role in the regulation of bone metabolism. In this study, we investigated changes in the expression of IGF-I and IGF-I receptor and cell proliferation when a continuous tensile force was applied to the cranial suture of cultured rat calvaria. The parietal bones with the midsagittal suture were removed from male Wistar rats (19-days old), cultured for 24h, and divided into two groups. In the experimental group, tensile force (3 x 10(-3)N) was applied by helical springs to the midsagittal suture, whereas helical springs with no tension (0 N) were set in the control group. The tensile force significantly increased the expression of both IGF-I mRNA and protein (P < 0.05). By using in situ hybridisation, we also confirmed that IGF-I and IGF-I receptor mRNAs were localized in osteoblast-like and fibroblastic cells subjected to the tensile force. Also, this force stimulated the proliferation of osteoblast-like and fibroblastic cells in calvaria, without affecting their alkaline phosphatase activity. These results indicate that a tensile force applied to a cranial suture can cause an increase in the production of IGF-I and IGF-I receptors in osteoblast-like and fibroblastic cells, and this increase in IGF-I may cause the proliferation of the cells in an autocrine or paracrine manner.
authors.affiliation: Department of Orthodontics, School of Dentistry, Aichi-Gakuin University, Nagoya 464-8650, Japan. hirukawa@dpc.aichi-gakuin.ac.jp
authors.forename: Koji
authors.initials: K
authors.lastname: Hirukawa
authors.forename: Ken
authors.initials: K
authors.lastname: Miyazawa
authors.forename: Hatsuhiko
authors.initials: H
authors.lastname: Maeda
authors.forename: Yoichiro
authors.initials: Y
authors.lastname: Kameyama
authors.forename: Shigemi
authors.initials: S
authors.lastname: Goto
authors.forename: Akifumi
authors.initials: A
authors.lastname: Togari
mesh_terms: D000818:Animals; D004396:Coloring Agents; D003393:Cranial Sutures / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D017403:In Situ Hybridization; D007334:Insulin-Like Growth Factor I / Q000032:analysis* / Q000235:genetics; D008297:Male; D009924:Organ Culture Techniques; D018809:Proliferating Cell Nuclear Antigen; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017208:Rats, Wistar; D017526:Receptor, IGF Type 1 / Q000032:analysis* / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013314:Stress, Mechanical; D013718:Tensile Strength
chemical_list: D004396:Coloring Agents; D018809:Proliferating Cell Nuclear Antigen; D012333:RNA, Messenger; D007334:Insulin-Like Growth Factor I; D017526:Receptor, IGF Type 1