工程化肌腱修复肌腱缺损后力学特性的组织学基础

探讨组织工程化肌腱修复肌腱缺损后体内愈合过程中力学特性的组织学基础。取罗曼鸡肌腱细胞 ,经体外培养、扩增 ,与可降解生物材料聚羟基乙酸筛网构建工程化肌腱 ;将其植入修复 2 0只罗曼鸡第二趾深屈肌腱0 .5～ 0 .8cm缺损。术后第 2、4、6、8周取材 ,对标本进行大体、组织学及生物力学测定。植入 2、4、6、8周 ,新生肌腱在大体形态、细胞及胶原纤维排列方式上与正常肌腱相似 ,但新生肌腱的胶原纤维束并未形成较多的沿肌腱长度方向的致密结构 (“塑形”) ,导致其最大张力增加缓慢 ,到 8周时为 15 .4 0± 10 .6 3N,仅达正常肌腱的 2 3 ;8周时最大张应变为 2 2 .4 9± 10 .2 1 ,比正常肌腱大 10。结果表明 ,单纯聚羟基乙酸作支架 ,材料降解过快 ,新生肌腱失去了正常的力学刺激 ,“塑形”能力差 ,其生物力学强度低。提示 ,保持新生肌腱形成过程中正常的力学刺激对新生肌腱的“塑形”可能是至关重要的。

Histologic Pattern and Mechanical Properties of Tissue-engineered Tendon Implants for Tendon Defects

This is a study on the histologic pattern and mechanical properties of tissue-engineered tendon implanted for treatment of tendon defects. Tendons were resected from Roman chickens. Tendon cells were isolated from the tendons and cultured in vitro. The 2nd-4th passages of tendon cells were seeded on the degradable polyglycolic acid mesh to form cell-scaffold composites, which were further cultured for 7-10 days to construct tissue-engineered tendons. The tendon defects, 0.5 cm-0.8 cm in length, were made in the second digit flexor tendon bilaterally in 20 Roman chickens and then bridged with the constructed tissue-engineered tendons. At 2 weeks, 4 weeks, 6 weeks, and 8 weeks post-operation, the samples of regenerated tendons were collected for gross examination, histologic staining and biomechanical test. After implantation of the tissue-engineered tendons, the wounds healed well. The gross appearance, the cells and collagen fibers arrangement of the regenerated tendons were similar to those of natural tendons, but there were relatively not many closely packed collagen fiber bundles organized in parallel with the tendons ("remodel"), so the maximum tensile force increased slowly and its value was 15.40+/-10.63 N at 8 weeks after surgery, reaching only 23% of that of natural tendon. The maximum strain was 22.49%+/-10.21% at 8 weeks, being 10% higher than that of natural tendons. Polyglycolic acid scaffolds are degraded in vivo so rapidly that the regenerated tendons lose the normal biomechanical stimulus and then are unable to be remodeled. As a result, the mechanical strength of regenerated tendons is much lower than that of natural tendons. These results suggest that the normal biomechanical stimulus may be an important factor for the regenerated tendons to remodel.