THE ROLE OF THE EXTRACELLULAR MATRIX IN SCARLESS TENDON HEALING

 描述(申请人提供)：肌腱撕裂是一种常见的肌肉骨骼损伤，可以在不恢复功能结构的情况下愈合。愈合肌腱不能恢复功能结构会导致损伤的进展和手术修复后再撕裂的高发生率。无疤痕肌腱愈合，通过恢复自然组织特性，可以改善手术结果或完全消除手术修复的需要，但在出生后的哺乳动物中通常不会观察到这种情况。成年Murphy Roths大鼠(MRL/MPJ)表现出再生能力的发现使该小鼠品系成为研究成年再生愈合基础机制的一个令人兴奋的模型。对MRL/MPJ小鼠再生机制的研究已经产生了涉及全身和局部组织水平的假说，但没有确凿的数据存在。这项拟议的研究询问了MRL/MPJ小鼠的全身环境和其肌腱的局部环境对无疤痕肌腱愈合的贡献。我们的假设是，MRL/MPJ肌腱的无瘢痕愈合是由一种独特的临时细胞外基质(ECM)介导的，该细胞外基质促进基质生成细胞的排列和增殖，但最终不会由于基质金属蛋白酶9(MMP9)分解代谢活性的增加而导致过度的基质沉积。除了我们发表的数据表明mrl/mpj小鼠在中间物质撞击损伤后表现出更好的愈合能力，其他支持这一新假说的证据包括：(1)数据表明再生的mrl/mpj小鼠的临时细胞外基质在结构和组成上与修复B6肌腱的临时细胞外基质不同；(2)数据表明在愈合的早期阶段，mrl/mpj小鼠的肌腱在这种明显不同且排列更好的临时细胞外基质;的背景下，细胞增殖增加，排列改善；(3)相关数据显示MMP9和临时细胞外基质的表达增加，由排列更好的长期细胞外基质取代。我们建议询问有助于合成MRL/MPJ独特的临时ECM的系统和局部因素(目标2)，并阐明这种临时ECM在调节细胞反应中的作用(目标1)。我们还将探索来自MRL/MPJ愈合肌腱的临时ECM在促进SCART介导的B6小鼠的无疤痕肌腱愈合方面的治疗潜力(目标3)。新的显微外科技术和近交系小鼠品系被用来分离全身环境和肌腱对无疤痕肌腱愈合的贡献。肌腱器官培养也被用来确定再生MRL/MPJ小鼠的临时ECM在调节导致无疤痕肌腱愈合的细胞活动中的作用。这些研究通过分离先天性肌腱和全身环境对无疤痕肌腱愈合的作用，为开发治疗干预措施奠定了基础。MRL/MPJ的临时ECM作为一种治疗干预的潜在用途，利用导致无疤痕肌腱愈合的生物和结构队列，可能对肌腱组织工程领域产生极大的影响。

 DESCRIPTION (provided by applicant): Tendon tears are common musculoskeletal injuries that heal without restoration of the functional structure. Failure of healing tendons to restore th functional structure leads to progression of injury and high incidence of retear after surgical repair. Scarless tendon healing, with restored native tissue properties, could improve surgical outcome or eliminate the need for surgical repair altogether, but is not typically observed in postnatal mammals. The discovery that adult Murphy Roths Large (MRL/MpJ) mice exhibit a regenerative capacity has distinguished this mouse strain as an exciting model to investigate mechanisms that underlie adult regenerative healing. Investigation into the regenerative mechanisms of MRL/MpJ mice has generated hypotheses that implicate both, the systemic and local tissue level, but no conclusive data exists. The proposed studies interrogate the contribution of the systemic environment of the MRL/MpJ mouse and the local environment of its tendon to scarless tendon healing. Our hypothesis is that scarless healing in MRL/MpJ tendons is mediated by a unique provisional extracellular matrix (ECM) that promotes improved alignment and proliferation of matrix producing cells but does not ultimately lead to excessive matrix deposition due to increased catabolic activity of Matrix Metalloproteinase 9 (MMP9). In addition to our published data that show that MRL/MpJ mice exhibit improved healing in midsubstance punch injuries, additional evidence that supports this novel hypothesis includes: (1) data that show that the provisional ECM in regenerative MRL/MpJ mice differs in structure and composition than the provisional ECM in healing B6 tendons; (2) data that show that during the early phases of healing, MRL/MpJ tendons exhibit increased cell proliferation and improved alignment in the context of this distinctly different and better aligned provisional ECM; and (3) correlated data that show increased expression of MMP9 and a provisional ECM that is replaced by a better aligned long term ECM. We propose to interrogate the systemic and local factors that contribute to synthesis of MRL/MpJ's unique provisional ECM (Aim 2) and elucidate the role of this provisional ECM in modulating the cellular response (Aim 1). We will also explore the therapeutic potential of the provisional ECM derived from MRL/MpJ healing tendons to promote scarless tendon healing in scarmediated B6 mice (Aim 3). Novel microsurgical techniques and inbred mouse strains are utilized to uncouple the contribution of the systemic environment and the tendon to scarless tendon healing. Tendon organ culture is also employed to determine the role of the provisional ECM from regenerative MRL/MpJ mice in modulating the cellular activity that leads to scarless tendon healing. These studies set the foundation for development of therapeutic interventions by isolating the contributions of the innate tendon and the systemic environment to scarless tendon healing. The potential utility of MRL/MpJ's provisional ECM as a therapeutic intervention that harnesses the biological and structural queues that lead to scarless tendon healing could be highly impactful for the field of tendon tissue engineering.