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压缩刺激影响关节软骨细胞代谢和力学特性的研究进展
在日常生活中，膝关节在站立、行走、跑步和其他日常活动时受到不断的机械刺激。在膝关节中，基质结构的高含水量(70%～80%)使关节软骨可以经受住复杂的压缩、拉伸和剪切应力。力学的刺激不仅在四肢软骨下骨的形成中调节软骨的稳定，而且在成人软骨的修复和骨骼重塑方面也发挥着重要的作用[1]。软骨体外培养的临床观察表明：力学刺激可以调节体外培养软骨细胞的合成和降解、影响改变组织的结构，在组织形态和细胞外基质新陈代谢方面有着重要的影响。这些信息意味着在生理的力学加载条件下也许是对膝关节功能的适当维护所必需的。出于对这个考虑，大量的对软骨组织工程的研究在施加持续的周期性压力后都表明有很好的预期效果。研究表明体外的力学刺激包括剪切力、动态压缩和低强度的脉冲等有助于软骨细胞表型的表达[2-3]。现就压缩刺激对软骨细胞代谢和力学特性的影响综述如下。
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压缩刺激影响关节软骨细胞代谢和力学特性的研究进展
在日常生活中，膝关节在站立、行走、跑步和其他日常活动时受到不断的机械刺激。在膝关节中，基质结构的高含水量(70%～80%)使关节软骨可以经受住复杂的压缩、拉伸和剪切应力。力学的刺激不仅在四肢软骨下骨的形成中调节软骨的稳定，而且在成人软骨的修复和骨骼重塑方面也发挥着重要的作用[1]。软骨体外培养的临床观察表明：力学刺激可以调节体外培养软骨细胞的合成和降解、影响改变组织的结构，在组织形态和细胞外基质新陈代谢方面有着重要的影响。这些信息意味着在生理的力学加载条件下也许是对膝关节功能的适当维护所必需的。出于对这个考虑，大量的对软骨组织工程的研究在施加持续的周期性压力后都表明有很好的预期效果。研究表明体外的力学刺激包括剪切力、动态压缩和低强度的脉冲等有助于软骨细胞表型的表达[2-3]。现就压缩刺激对软骨细胞代谢和力学特性的影响综述如下。
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关节软骨磁共振成像的研究进展
关节软骨损伤是临床常见病，可以导致关节疼痛、积液和功能障碍，严重者可致残。外伤、骨性关节炎( osteoarthritis，OA )、剥脱性骨软骨炎等原因均可造成关节软骨的损伤，并且一旦损伤极难修复。在长期大量运动的人群和老年人中，关节软骨的退变、损伤几乎都不同程度的存在。早期的软骨损伤易被忽视，临床诊断也缺乏特异性。关节镜虽是关节软骨损伤诊断的“金标准”，但有创伤、视野小、有盲区、无法显示软骨下骨损伤程度等局限；常规X线、CT检查无法直观显示关节软骨。MRI凭借其多方位、多序列、多参数成像及组织分辨率高、对比度好等诸多优势，不仅能无创性地观察软骨损伤的部位、范围、程度、软骨表面的病理变化，而且能准确观察软骨内部、软骨下骨及骨髓的病变情况，被公认为目前评价软骨损伤的佳无创检查方法[1]。尤其是近年来定量磁共振成像技术的快速发展，使得关节软骨无创性检查从形态学发展到了分子生化水平，为早期关节软骨损伤的检测以及修复效果的评估提供了更多行之有效的技术手段[2]。但在临床工作中，对于关节软骨的 MRI 序列选择及优化组合、软骨损伤在不同 MRI 序列中的表现和诊断等方面尚无统一标准[3]。
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The Effect of Opsteoporotic Model Rats Induced by Retinoic Acid
Objective: To study the effect of retinoic acid on inducing osteoporosis in female rat. Methods: 48SD female rats were divided randomly into experiment group and control group. Retinoic acid was administered orally to experiment group with 80mg.kg-1d-1 for 15 days. Then the rats were sacrificed on the 0th, 30th, 60th days after last administration. The serum concentration of Ca, P, BGP, E2, AKP and TRAP were detected. Components of collagen and proteoglycan in the bones and BMD were also assayed .The femoral morphometric change and epiphyseal plate cartilage histological changes were observed. Results: After a 15-day period treatment with retinoic acid, charateristics of experiment group were compared with control, it is shown that the concentration of serum E2 and BGP declined, the activity of AKP and TRAP increased while BMP decreased, the bone mass of both spongy bone and cortical bone reduced, the number of spongy bone osteoclasts and their activity increased, number of epiphyseal plate chondrocyte reduced, cartilage hypertrophic zone displayed dyscalcification, and no difference of other markers was found in the two groups. On the 30th day after the last administration, the experiment group appeared a declined number of cancellous bone osteoclast and level of serum AKP yet they were still higher than control. Number of epiphyseal chondrocyte, serum BGP and tibial BMD, though higher than before, were still lower than control. Other markers were no difference. On the 60th day after treatment, although the femoral cancellous bone mass was still less and cancellous osteoblast was more than control, the cortical bone mass, cancellous osteoclast number and level of serum Ca and P were all remained no different between two groups.Conclusion: Retinoic acid possessed a better short-term effect than long-term effect. Cancellous bone loss lasted much longer than cortical bone and more obviously; the bone matrix in this osteoporosis model was able to repair itself gradually after withdrawal of retinoic acid.
