Mechanical Compatibility of Biomaterials evaluated by Culture System

在这个实验中，我们开发了一个培养系统来检测机械刺激对胶原凝胶标本的影响，包括成纤维细胞。应变大小设定为10%的拉伸和压缩，频率0.5Hz，每天24小时，持续1或2周。在显微镜下进行微拉伸试验，测量了试验后试样和静态状态下对照试样的弹性模量和最大应力的力学性能。实验和对照试样的力学性能指标均随培养时间的增加而增加。在力学测试中，我们进一步利用标记颗粒测量试样的应变分布，标记颗粒的位置通过图像分析来确定。强度主要集中在拉应力条件下的中部部位，而两端压应力条件下的强化程度最低。机械刺激作用的程度因细胞类型而异。在骨髓基质细胞中，细胞产生的拉伸应力非常强，即使在静态条件下，样品也会收缩得非常大，并与承载凝胶的不锈钢丝网分离。另一方面，L细胞产生的拉应力很小，机械刺激的影响很小。体内实验，这是之前的体外实验的对应发展。在大鼠模型中，股骨-髌骨肌腱-胫骨标本固定在不锈钢支架中，移植到背部皮肤下，施加人工重复拉伸应力。如果施加机械刺激，肌腱的最大强度不会降低，但在静态条件下的对照标本会降低。因此，在生物体中执行机械功能的结缔组织中，组织的命运是由机械环境支配的。人工材料与活体组织的机械完整性是建立在胶原蛋白与生物材料之间强结合的基础上的，由于细胞尤其是成纤维细胞和成骨细胞在界面处产生的张力可能与它们相匹配，这可能导致组织和材料之间的生物相容性存在差异。少

In this experiment, we developed a culture system to examine the effect of mechanical stimuli on the collagen gel specimen involving fibroblasts. The magnitude of strains were set to 10% in tension and compression, the frequency was 0.5Hz, 24 hours a day and last 1 or 2 weeks. The mechanical properties of elastic moduli and maximum stress of specimens after testing and the control specimens at static condition were measured by micro tensile testing under microscope. It was found that both indicators of mechanical properties increase in accordance with the culture time in experimental and control specimens. It also found that the strengthening of specimens were more significant in experimental group than control group In mechanical testing we further measure the strains distributions of spesimens by the use of the marker particles which locations were measured by image analyzes. The strenghtening was induced mainly on the central parts of the specimens where the tensile stress condition … More s were realized, whereas both ends of the specimens where compressive stress were generated were least strengthened. The degree of the effects of mechanical stimuli differ among the type of the cells. In bone marrow stromal cells, the tensile stresses generated by the cells were very strong and even the specimens in static conditions shrank very much and they detached from the stainless steel t wire mesh holding the gel. On the other hand, the tensile stress generated by the L cells were very small and very little effect of mechanical stimuli were observed.The in vivo experiments, which were the couterparts of the previous vitro experiments were developed. In this rat model in which a femora-patellar tendon-tibia specimen were fixed in a stainless steel holder and transplanted under the back skin, artificial repetitive tensile stress were applied. The maximum strength of the tendon did not decreased if the mechanical stimuli were applied, but the control specimens under static conditions did. Thus in the connective tissue which carried out mechanical functions in living body, the fate of the tissues is governed by the mechanical environment. It also suggests that the mechanical integrity of the artificial materials and the living tissue is based on the strong binding between collagen and biomaterials, and since the cells especially fibroblasts and osteoblasts generate tensile stress which may datatch them at the interface, it may result in the differences in biocompatibilty among the tissues and materials. Less