剪切应力和牵拉应力对骨腱界面愈合的作用及相关机制研究

Bone tendon junction injury is one of the most common diseases in sports medicine. Tendon to bone healing is generally recognized as the most difficult hurdle, with excessive scar formation and a lack of fibrocartilage formation. The applicant has long been working on how to enhance tendon to bone healing with an established partial patellectomy (PT) model in rabbits. A fibrocartilaginous enthesis, not fibrous scar tissue, was formed at the remaining patella/patellar tendon interface. Through a comparative analysis of the rotator cuff and ACL reconstruction model with our PT model, we found that the collagen fibers of rotator cuff and ACL graft was usually parallel to the bone surface after reconstruction, thus mainly suffering to shear force; while the collagen fibers of patellar tendon was vertical to the surface of the remaining patella, thus mainly suffering to tensile force. Therefore, this study intends to employ the PT model (mainly tensile force) and the remaining patellar tendon was sutured through a bone tunnel (mainly shear force) to study the effects of tensile force and shear force on tendon to bone healing with the use of histological, radiological and biomechanical analysis. Furthermore, the expression of TGF-β/BMP, Ihh/PTHrP, Sox-9, Scleraxis and other biological molecules will be investigated to explore the related molecular biological mechanism. This study will provide a theoretical basis for surgical approaches and biological interventions related to tendon/bone healing.

具有独特结构的骨腱连接点损伤后修复一直是运动医学领域里的难题。其愈合常常以紊乱的瘢痕组织形成为主，而缺少纤维软骨层的再生。课题组长期从事髌骨髌腱连接点损伤后愈合过程的研究，我们利用兔髌骨部分切除模型（PT）研究发现，修复后的髌骨髌腱界面会形成纤维软骨性骨腱连接点，而不是纤维瘢痕组织（常见于肩袖和ACL重建）。通过对比分析，我们考虑肩袖和ACL重建时肌腱胶原纤维与骨界面常常呈平行状态，以剪切应力为主；而PT模型的肌腱胶原纤维与重建骨面呈垂直状态，以牵拉应力为主。因此本研究拟采用髌腱直接缝合模型（牵拉应力为主）和髌腱经骨隧道缝合模型（剪切应力为主），利用组织学、影像学以及生物力学系统分析剪切应力和牵拉应力对骨腱愈合的影响，并通过分析TGF-β/BMP 通路，Ihh/PTHrP通路，Sox-9和Scleraxis等生物分子的表达特点，为骨腱连接点损伤后的重建方式和生物学干预提供理论依据。

骨腱连接点具有独特而且复杂的结构和生物力学特性。然而，涉及骨腱连接点修复的运动损伤在骨科及运动医学领域却十分常见。本项目建立残余髌腱直接缝合重建模型和残余髌腱经骨槽缝合到髌骨的动物模型，前者髌腱胶原纤维与重建骨界面垂直（骨腱界面以牵拉应力为主）；后者髌腱胶原纤维与重建骨界面平行（骨腱界面以剪切应力为主）。利用组织学、影像学以及生物力学等方法系统的分析研究剪切应力和牵拉应力对髌骨髌腱愈合的影响，并通过分析II/X 型胶原， Biglycan， Decorin， Sox-9， Scleraxis， TGF-β1 和Gli3等生物分子在骨、纤维软骨、肌腱层的时间和空间表达特点，初步分析剪切应力和牵拉应力如何调控髌骨髌腱连接点损伤后的再生愈合。我们发现髌骨部分切除髌腱直接缝合模型时，骨腱界面损伤愈合主要表现为纤维软骨性愈合，形成类似正常骨腱连接点的四层结构；髌骨部分切除髌腱经骨槽缝合模型，槽内以剪切应力为主，骨腱界面损伤愈合主要表现为纤维性愈合，未能形成类似骨腱连接点四层结构，骨腱截骨面处表现为纤维软骨性愈合。髌腱经骨槽缝合可以获得较髌腱直接缝合更好的生物力学性能，为骨腱连接点损伤后的手术重建方式和生物学干预提供理论依据。