Improving tendon-to-bone repair with hedgehog signaling therapeutics

总结 大约30%的美国成年人患有肌腱和韧带损伤。这些损伤通常需要修复 (e.g.,旋转套）或重建（例如，前交叉韧带（ACL））重新整合中间物质， 邻近的骨头。重建带状肌腱-骨插入部位（即，对恢复正常至关重要 功能带状附着点的形成包括固定胶原纤维，合成富含蛋白多糖的 纤维软骨和矿化纤维软骨。Hedgehog（Hh）信号通路对细胞的增殖和分化至关重要。 通过促进未矿化和矿化的形成，在发育过程中形成带状插入物 附着点的纤维软骨区。不幸的是，在传统的肌腱-骨修复中研究这一途径， 这是一个挑战，因为这些修复模型不能充分地将胶原纤维锚到骨上，更不用说产生 纤维软骨区相反，韧带重建，其中肌腱移植物通过骨放置 隧道，可以产生带状附着。因此，我们利用创新的转基因小鼠ACL重建， 模型来阐明带状肌腱-骨修复的机制，以开发新的治疗方法， 改善修复效果。我们的初步数据表明，Hh信号促进带状腱骨 ACL重建后的整合。这个建议的目的是局部刺激刺猬信号 通过Hh激动剂的支架递送以增加带状腱-骨附着的形成。我们的假设 激动剂递送将刺激局部祖细胞增殖，然后分化成 纤维软骨细胞的附件，导致改善隧道整合。我们将使用多路复用， 矿化冷冻组织学用于监测区域附着，新的机械测试用于评估隧道 整合实力。如果Hh通路可以在治疗上加以利用，那么它将导致一种范式的转变， 治疗这些使人衰弱的创伤

SUMMARY Approximately 30% of U.S. adults suffer from tendon and ligament injuries. These injuries often require repair (e.g., rotator cuff) or reconstruction (e.g., anterior cruciate ligament (ACL)) to re-integrate the midsubstance with the adjacent bone. Recreating the zonal tendon-to-bone insertion site (i.e., enthesis) is critical to restoring normal function. Zonal enthesis formation involves anchoring collagen fibers, synthesizing proteoglycan-rich fibrocartilage, and mineralizing this fibrocartilage. The hedgehog (Hh) signaling pathway is critical to the formation of a zonal insertion during development by promoting the formation of unmineralized and mineralized fibrocartilage zones of the enthesis. Unfortunately, studying this pathway in traditional tendon-to-bone repair has been a challenge since these repair models do not sufficiently anchor collagen fibers to bone, much less produce zones of fibrocartilage. Conversely, ligament reconstructions, where a tendon graft is placed through bone tunnels, can produce zonal attachments. Therefore, we utilize innovative transgenic murine ACL reconstruction models to elucidate the mechanisms of zonal tendon-to-bone repair in order to develop novel therapies to improve the repair outcome. Our preliminary data demonstrate that Hh signaling promotes zonal tendon-to-bone integration following ACL reconstruction. The objective of this proposal is to locally stimulate hedgehog signaling via scaffold delivery of Hh agonist to increase the formation of zonal tendon-to-bone attachments. Our hypothesis is that delivery of the agonist will stimulate the local progenitor cells to proliferate and then differentiate into fibrochondrocytes in the attachments, leading to improved tunnel integration. We will use multiplexed, mineralized cryohistology to monitor the zonal attachments and novel mechanical testing to assess tunnel integration strength. If the Hh pathway could be harnessed therapeutically, it would result in a paradigm shift in the treatment of these debilitating injuries.