The effects of low dose X-irradiation on osteoblastic MC3T3-E1 cells in vitro.
BACKGROUND
It has been indicated that moderate or high dose of X-irradiation could delay fracture union and cause osteoradionecrosis, in part, mediated by its effect on proliferation and differentiation of osteoblasts. However, whether low dose irradiation (LDI) has similar roles on osteoblasts is still unknown. In this study, we investigated whether and to what extent LDI could affect the proliferation, differentiation and mineralization of osteoblasts in vitro.


METHODS
The MC3T3-E1 cells were exposed to single dose of X-irradiation with 0, 0.1, 0.5, 1.0 Gy respectively. Cell proliferation, apoptosis, alkaline phosphatase (ALP) activity, and mineralization was evaluated by methylthiazoletetrazolium (MTT) and bromodeoxyuridine (BrdU) assay, flow cytometry, ALP viability kit and von Kossa staining, respectively. Osteocalcin (OCN) and core-binding factor α1 (Cbfα1) expressions were measured by real time-PCR and western blot, respectively.


RESULTS
The proliferation of the cells exposed to 2.0 Gy was significantly lower than those exposed to ≤1.0 Gy (p < 0.05) from Day 4 to Day 8, measured by MTT assay and BrdU incorporation. For cells exposed to ≤1.0 Gy, increasing dosages of X-irradiation had no significant effect on cell proliferation and apoptosis. Importantly, LDI of 0.5 and 1 Gy increased ALP activities and mineralized nodules of MC3T3-E1 cells. In addition, mRNA and protein expressions of OCN and Cbfα1 were also markedly increased after treatment with LDI at 0.5 and 1 Gy.


CONCLUSIONS
LDI have different effects on proliferation and differentiation of osteoblasts from those of high dose of X-irradiation, which might suggest that LDI could lead to promotion of fracture healing through enhancing the differentiation and mineralization of osteoblasts.
Department of Orthopedics, The Second Affiliated Hospital of Soochow University, Suzhou, China.
Wei
W
Xu
Lan
L
Xu
Ming
M
Chen
Yong Tao
YT
Mao
Zong Gang
ZG
Xie
Shi Liang
SL
Wu
Qi Rong
QR
Dong
D016475:3T3 Cells / Q000378:metabolism / Q000473:pathology / Q000528:radiation effects; D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D017209:Apoptosis / Q000528:radiation effects; D001973:Bromodeoxyuridine / Q000378:metabolism; D002113:Calcification, Physiologic / Q000528:radiation effects*; D002118:Calcium / Q000032:analysis / Q000378:metabolism; D002454:Cell Differentiation / Q000528:radiation effects*; D002460:Cell Line; D049109:Cell Proliferation / Q000528:radiation effects*; D002470:Cell Survival / Q000528:radiation effects; D050659:Core Binding Factor Alpha 1 Subunit / Q000235:genetics / Q000378:metabolism; D004307:Dose-Response Relationship, Radiation; D015870:Gene Expression / Q000528:radiation effects; D051379:Mice; D010006:Osteoblasts / Q000378:metabolism / Q000473:pathology / Q000528:radiation effects*; D015675:Osteocalcin / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D013778:Tetrazolium Salts / Q000378:metabolism; D013844:Thiazoles / Q000378:metabolism
D050659:Core Binding Factor Alpha 1 Subunit; D012333:RNA, Messenger; C493716:Runx2 protein, mouse; D013778:Tetrazolium Salts; D013844:Thiazoles; D015675:Osteocalcin; D000469:Alkaline Phosphatase; C022616:thiazolyl blue; D001973:Bromodeoxyuridine; D002118:Calcium