Low-intensity laser irradiation stimulates bone nodule formation via insulin-like growth factor-I expression in rat calvarial cells.
OBJECTIVE
We previously reported that low-intensity laser irradiation stimulated bone nodule formation through enhanced cellular proliferation and differentiation. However, the mechanisms of irradiation are unclear. Thus, we attempted to determine the responsibility of insulin-like growth factor (IGF)-I for the action observed.


METHODS
Osteoblast-like cells were isolated from fetal rat calvariae and cultured with rat recombinant (r) IGF-I, IGF-I-antibody (Ab), and/or the cells were irradiated once (3.75 J/cm(2)) with a low-intensity Ga-Al-As laser (830 nm). The number and area of bone nodules formed in the culture were analyzed, and IGF-I expression was also examined.


RESULTS
Treatment with rIGF-I significantly stimulated the number and area of bone nodules. This stimulatory effect was quite similar to those by laser irradiation, and this stimulation was abrogated dose-dependently by treatment with IGF-I-Ab. Moreover, laser irradiation significantly increased IGF-I protein and gene expression.


CONCLUSIONS
The stimulatory effect of bone nodule formation by low-intensity laser irradiation will be at least partly mediated by IGF-I expression.
Shimizu
Noriyoshi
N
Department of Orthodontics, Nihon University School of Dentistry, 1-8-13 Kanda, Surugadai, Chiyoda-Ku, Tokyo101-8310, Japan. shimizu-n@dent.nihon-u.ac.jp
Mayahara
Kotoe
K
Kiyosaki
Takeshi
T
Yamaguchi
Akikuni
A
Ozawa
Yasuhiro
Y
Abiko
Yoshimitsu
Y
D000818:Animals; D000906:Antibodies; D002478:Cells, Cultured; D015232:Dinoprostone / Q000096:biosynthesis; D005260:Female; D005333:Fetus; D015870:Gene Expression; D007334:Insulin-Like Growth Factor I / Q000096:biosynthesis*; D028022:Low-Level Light Therapy; D023421:Models, Animal; D010006:Osteoblasts / Q000378:metabolism / Q000528:radiation effects; D010012:Osteogenesis / Q000502:physiology / Q000528:radiation effects; D011247:Pregnancy; D051381:Rats; D017208:Rats, Wistar; D012886:Skull / Q000166:cytology / Q000378:metabolism* / Q000528:radiation effects*
D000906:Antibodies; D007334:Insulin-Like Growth Factor I; D015232:Dinoprostone