Tendon Enthesis Development and Regeneration

 描述(由申请人提供)：由于不同材料的界面产生应力集中，因此附着在不同材料上具有挑战性。肌腱-骨连接部位(“末端”)利用包括结构、细胞外基质成分和细胞表型的空间梯度的功能梯度移行组织来解决这一力学问题。这 强而坚韧的依恋系统是在分子和生物物理线索的调节下，在胎儿和出生后的时间点形成的。不幸的是，这种独特的结构在手术修复和愈合后没有被重建，导致了非常高的失败率。因此，我们的目标是了解肌腱末端的发育情况，以促进末端修复的再生策略。我们的总体假设是，生化(转化生长因子和IHH)和生物物理(肌肉力量)线索的时空调节对于推动功能性末端的发育和损伤后的再生是必要的。我们的假说是由我们最近的工作启发的，该工作表明，胚胎肌腱与骨的附着起源于不同的祖细胞群体，而出生后的末端成熟和矿化是由印度刺猬信号和肌肉负荷驱动的。然而，目前尚不清楚这些处于发育中的附着体的细胞群是如何调节成熟雌蕊的形成的。因此，目标1将确定组成成熟末端的细胞的谱系，从胚胎时间点开始，直到骨骼成熟。目的2将确定成巢细胞表型的分子和机械调节(S)，重点是早期发育事件的转化生长因子和晚期矿化事件的IHH信号。在目标3中，我们将确定末端细胞谱系和分子信号在损伤的末端修复和再生中的作用，重点是在末端负责IHH信号的细胞。这些目的将使我们能够识别和表征存在于末端的细胞，并揭示它们分化所需的分子和生物物理事件序列。结果将直接影响到 未来基于细胞和生长因子的肌腱到骨修复的再生策略。

 DESCRIPTION (provided by applicant): Attachment of dissimilar materials is challenging due to stress concentrations that arise at their interface. The tendon-to-bone attachment site ("enthesis") solves this mechanical problem using a functionally graded transitional tissue that includes spatial gradients in structure, extracellular matrix composition, and cell phenotype. This strong and tough attachment system is formed during fetal and postnatal timepoints under the regulation of molecular and biophysical cues. Unfortunately, this unique structure is not recreated after surgical repair and healing, leading to remarkably high failure rates. Therefore, our goal is to gain an understanding of tendon enthesis development in order to motivate regenerative strategies for enthesis repair. Our overall hypothesis is that temporal and spatial regulation of biochemical (TGFß and Ihh) and biophysical (muscle force) cues are necessary to drive the development of a functional enthesis and for regeneration after injury. Our hypothesis is motivated by our recent work, which showed that embryonic tendon-to-bone attachment initiates from a distinct population of progenitor cells and postnatal enthesis maturation and mineralization is driven by Indian hedgehog signaling and muscle loading. It remains unclear, however, how these cell populations at the developing attachment regulate the formation of a mature enthesis. Therefore, Aim 1 will determine the lineage (or lineages) of the cells that compose the mature enthesis, starting at embryonic timepoints and progressing through skeletal maturity. Aim 2 will determine the molecular and mechanical regulation of the enthesis cell phenotype(s), focusing on TGFß for early developmental events and Ihh signaling for later mineralization events. In Aim 3, we will determine the role of enthesis cell lineages and molecular signaling for repair and regeneration of the injured enthesis, focusing on cells responsible for Ihh signaling at the enthesis. These aims will allow us to identify and characterize the cells that populate the enthesis and to uncover the molecular and biophysical sequence of events that is required for their differentiation. Results will have a direct impact on future cell- and growth factor-based regenerative strategies for tendon-to-bone repair.