[Low dose X-irradiation promotes callus mineralization: experiment with rats].
OBJECTIVE
To investigate the effect of low dose irradiation (LDI) on callus formation and mineralization.


METHODS
80 SD rats were subjected to standard closed fracture on right femur so as to establish animal models and then were randomly divided into 2 equal groups: LDI group undergoing low dose whole body X-ray irradiation of 1Gy right after fracture induction and control group without irradiation. 1, 2, 3, 4, and 8 weeks later blood samples were collected from the heart to examine the amounts of white blood cells and platelets and alkaline phosphatase (ALP) level. Conventional X-ray films were taken and MicroCT was conducted to evaluate the callus bridging. Then the rats were killed to take out the femurs to undergo histological examination. Peripheral quantitative computed tomography (pQCT) was conducted to quantify the bone mineral content (BMC). Four-point bending test was used to examine the mechanical properties of the callus.


RESULTS
The maximum load value and histological score 2 weeks later of the LDI group were both lower than those of the control group, however, the serum ALP, BMC, maximum load level, callus bridging score, and histological score 3 weeks later of the LDI group were all significantly higher than those of the control groups (all P<0.05). 4 and 8 weeks later there were not significant differences in all these parameters between the 2 groups. The WBC amount in the first 2 weeks of experiment of the LDI group was remarkably lower in these 2 groups, however, in the third week, the WBC value of the LDI group was higher than that of the control group (P<0.05).


CONCLUSIONS
LDI promotes the mineralization at the stage of hard callus formation which is probably associated with progenitor cell mobilization.
Zhou
Xiao-zhong
XZ
Department of Orthopedics, Second Affiliated Hospital, Soochow University, Suzhou 215004, China.
Zhang
Ge
G
Qin
Ling
L
Zhou
Hai-bin
HB
She
Chang
C
Zhang
Jian
J
Liu
Chun-feng
CF
Dong
Qi-rong
QR
D000818:Animals; D002146:Bony Callus / Q000528:radiation effects*; D004195:Disease Models, Animal; D017102:Fracture Healing / Q000528:radiation effects*; D008297:Male; D011829:Radiation Dosage; D051381:Rats; D017207:Rats, Sprague-Dawley; D055114:X-Ray Microtomography