Carbon dioxide laser irradiation stimulates mineralization in rat dental pulp cells.
OBJECTIVE
To examine the effect of carbon dioxide laser irradiation on mineralization in dental pulp cells.


METHODS
Rat dental pulp cells were irradiated with a carbon dioxide laser at 2 W output power for 20, 40 and 60 s, and were cultured in ascorbic acid and beta-glycerophosphate containing media. Cell viability was examined 24 h after laser irradiation by a modified MTT assay. Alizarin Red S staining was performed 10 days after laser irradiation. The amounts of secreted collagen from the cells after irradiation were quantified following Sirius Red staining. The expression levels of collagen type I and HSP47, collagen-binding stress protein, were analysed by real-time PCR. HSP47 protein expression was examined by Western blotting. Statistical analysis was performed using one-way analysis of variance (anova) followed by the Tukey's multiple comparison test.


RESULTS
The cell viability was not affected by laser irradiation at 2 W for up to 40 s. However, it was significantly decreased by 20% at 60 s (P < 0.05). The amount of mineralization after 10 days of irradiation at 2 W for 40 s was significantly increased in comparison to the other conditions (P < 0.05). The extracellular collagen production was significantly increased by 73% on day 2 and 38% on day 4 after laser irradiation (P < 0.05). Although collagen type I gene expression was not changed by laser irradiation, HSP47 gene and protein expression was induced within 12 and 24 h, respectively.


CONCLUSIONS
These results suggested that carbon dioxide laser irradiation stimulated mineralization in dental pulp cells. The laser irradiation also increased HSP47 expression but not collagen gene expression.
Yasuda
Y
Y
Division of Clinical Cariology and Endodontology, Department of Oral Rehabilitation, School of Dentistry, Health Sciences University of Hokkaido, Hokkaido 061-0293, Japan. yasuda@hoku-iryo-u.ac.jp
Ohtomo
E
E
Tsukuba
T
T
Okamoto
K
K
Saito
T
T
D000818:Animals; D000880:Anthraquinones; D001205:Ascorbic Acid; D002113:Calcification, Physiologic / Q000528:radiation effects*; D002470:Cell Survival / Q000528:radiation effects; D002478:Cells, Cultured; D003094:Collagen / Q000032:analysis / Q000378:metabolism; D024042:Collagen Type I / Q000032:analysis; D004396:Coloring Agents; D003470:Culture Media; D003782:Dental Pulp / Q000166:cytology / Q000378:metabolism / Q000528:radiation effects*; D005260:Female; D005994:Glycerophosphates; D050958:HSP47 Heat-Shock Proteins / Q000032:analysis; D054020:Lasers, Gas / Q000627:therapeutic use*; D051381:Rats; D017208:Rats, Wistar; D013778:Tetrazolium Salts; D013844:Thiazoles; D013997:Time Factors
D000880:Anthraquinones; D024042:Collagen Type I; D004396:Coloring Agents; D003470:Culture Media; D005994:Glycerophosphates; D050958:HSP47 Heat-Shock Proteins; C494662:Serpinh1 protein, rat; D013778:Tetrazolium Salts; D013844:Thiazoles; C004468:Alizarin Red S; D003094:Collagen; C022616:thiazolyl blue; D001205:Ascorbic Acid; C031463:beta-glycerophosphoric acid