低剂量X射线照射促进大鼠骨折骨痂矿化的研究

目的 探讨低剂量X线照射对骨折愈合的影响及初步机理.方法 80个SD大鼠随机分为实验组和对照组.制作标准的单侧股骨中段闭合骨折模型,对实验组立即采用医用直线加速器对大鼠进行总量为1 Gy的低剂量伞身照射.对照组不予照射.术后2、3、4、8周处死动物.使用常规摄片和微焦点CT(MicroCT)观察骨痂桥接,肢体定量CT(pQCT)检测骨矿含量,四点弯曲试验检测骨痂的力学性能并对标本作组织学分析.同时测定周围血白细胞数量和血清碱性磷酸酶(ALP).结果 骨折后第3周,实验组的ALP、骨痂桥接评分值、骨矿含量、组织学评分及力学测试结果均大于对照组(P<0.05).实验组的白细胞数量尽管在最初两周内降低,但随后(第3周)则高于对照组.实验组ALP数值也在第3、4周高于对照组.结论 LDI对硬骨痂形成期的骨痂形成和矿化具有促进作用.

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 thin of the control group (P<0.05 ). Conclusion LDI promotes the mineralization at the stage of hard callus formation which is probably associated with progenitor cell mobilization.