不同载荷对大鼠尺骨影响的在体研究

The establishment of a new mechanobiology model of bone and functional adaptation studies in vivo

目的研究骨组织对应力应变参数的生物学响应。方法将微型电阻应变片粘贴在大鼠左尺骨表面,活体检测正常行走时尺骨应变参数。利用 INSTRON 材料试验机模拟体内应变参数对大鼠左侧尺骨实施不同频率的力学载荷,建立大鼠力学生物学模型。将60只大鼠随机分成4大组,正常组,5、10、15 Hz 组,各实验组分为2000με组和3000με组;加载振幅为0.1 mm、半正弦波,10 min/d,加载2周,右上肢作为对照组。实验结束前后双能 X 射线骨密度测定仪(DXA)检测各组大鼠尺骨骨密度值(BMD);三点弯曲实验测试骨材料力学特性;免疫组织化学染色评价骨基质蛋白分泌情况;常规 HE 染色、盐酸四环素及钙黄绿素双荧光标记观察骨组织形态学变化。结果在10、15Hz 组中,2000με和3000με组促进了骨钙蛋白、Ⅰ型胶原的分泌,双荧光标记可看到两条明显的黄色和绿色的荧光条带,且实验组骨密度值显著高于正常组,(102±8)mg/cm^2比(113±6)mg/cm^2,P<0.05,但骨的力学性质却明显低于对照组(P<0.05)和正常组(P<0.01);在5 Hz 组中未见骨密度明显增加。结论成功构建活体大鼠骨力学生物学模型,并证实在一定应变范围内,短期的低幅高频的应力可促进骨生长。

Objectives to study the functional adaptation in response to artifical loading in vivo. Methods A single element strain gauge of 〈 2 mm × 3 mm in size was attached in longitudinal alignment to the medial surface of the ulnar midshaft, in vivo recordings of ulnar strains during locomotion were obtained. The ulnae of matural female rats were subjected to dynamic axial loading in vivo simulate strains during locomotion using INSTRON materials-testing machine. The left ulna of adult female rats were subjected to applied loading at frequencies of 5 Hz, 10 Hz, 15 Hz for 10 min/d with a haversine, low-magnitude （ 1 mm peak to peak） waveform for a two weeks period, the peak strains at the Left ulnar midshaft is 2000με and 3000 με, the right ulna of each rat served as a paired internal control. Dual Energy X-ray Absorptiometry （DXA） was used to measure bone mineral density （BMD） at the ulnar; 3-point bending was used to test mechanical characteristics; the ulna＇s response to loading was traced by subcutaneously injecting each rat twice with 7.5 mg/kg calcein and 30 mg/kg Tetracycline Hcl on days 3 and 12 of the loading period, and analyzed by histomorphometry; immhistochemistry as an effect of elevated strain in the bone matrix. Results at frequencies of 10 Hz,15 Hz groups, loading promoted obviously secreted of alkaline phosphatase（ ALP）, osteocalcin（OCN） and collagen Ⅰ ; a relative benefit in BMD was found compare to the control （P 〈0. 05） followed the decline of material mechanical properties （ modulus of elasticity, ultimate stress） （ P 〈 0. 01 ）. Conclusion These data show that a new bionics mechanobiology model of the axial ulna loading technique had be established successfully in rat. A short daily period of low-magnitude, high-frequency mechanical stimuli results in an osteogenic response related to peak strain magnitude.