骨髓间充质干细胞对不同时长应力刺激的力学响应

Responses from mesenchymal stem cells to mechanical stimulation for variable duration

目的通过检测骨髓间充质干细胞(mesenchymal stem cells,MSCs)的弹性模量和表征细胞应力纤维结构,研究不同时长应力刺激下MSCs的力学响应特点。方法利用原子力显微镜(atomic force microscope,AFM)和激光共聚焦显微镜(laser scanning confocal microscope,LSCM)对体外培养的大鼠MSCs细胞骨架进行高分辨成像,同时使用带有微球的微悬臂实施微区力曲线检测,进针时间分别选择为0.1、0.5、1、5、10 s,计算并比较300 nm压入深度时MSCs的弹性模量。结果大鼠MSCs的细胞骨架呈现致密交联网状结构。细胞弹性模量随应力刺激时长改变而发生明显变化,MSCs在作用时间分别为0.1、0.5、1、5、10 s时各组弹性模量中位数和4分位数(QR)间距分别为10.02(QR=9.66)、1.94(QR=7.71)、3.63(QR=19.33)、17.15(QR=35.13)、23.52 k Pa(QR=34.87)。除刺激时间极短(0.1 s)的情况,细胞弹性模量有随应力刺激时间增长而增大的趋势。结论大鼠MSCs具有完善的力学承载结构,与理想弹性体不同,可对较长时间应力刺激做出主动响应,导致弹性模量上升。研究结果可以为组织工程学通过力学刺激调控MSCs行为的研究提供基础数据。

Objective To study mechanical responses from mesenchymal stem cells（ MSCs） under different mechanical stimulus duration,by measuring its elastic modulus and characterizing its stress fibers. Methods High resolution images of MSCs cytoskeleton in vitro were acquired by using atomic force microscope（ AFM） and laser scanning confocal microscope（ LSCM）. AFM cantilever with micro-bead attached probe was used to perform force-distance curve experiment on MSCs at the approaching time of 0. 1,0. 5,1,5,10 s,respectively. The elastic modulus of MSCs at 300 nm indentation depth were measured and compared. Results The rat MSCs cytoskeleton presented an intensely organized network structure. The elastic modulus of rat MSCs varied obviously for different mechanical stimulus duration. The median and quartile（ QR） of MSCs elastic modulus were 10. 02（ QR = 9. 66）,1. 94（ QR = 7. 71）,3. 63（ QR = 19. 33）,17. 15（ QR = 35. 13）,23. 52 k Pa（ QR = 34. 87）,with probe approaching time at 0. 1,0. 5,1,5,10 s,respectively. The MSCs elastic modulus showed the tendency of increasing with stimulus duration increasing,except for the extremely short stimulus（ 0. 1 s）. Conclusions Unlike inorganic elastomer,rat MSCs possess complete and flexible mechanical load-bearing structure and can respond actively to a relatively longer mechanical stimulation,with an increase of elastic modulus. These results may provide basic data for further tissue engineering researches on mechanical regulation of MSCs behavior.