FUNCTIONAL TISSUE ENGINEERING FOR TENDON REPAIR

我们的总体假设是，含有间充质干细胞的“功能性”组织工程构建物可用于肌腱损伤模型，以改善修复的生物力学、结构和生化。植入物将在体外设计，具有适当的收缩特性和初始生物力学，以改善肌腱修复。功能组织工程或FTE将用于在培养中对组织工程(TE)植入物进行机械刺激，并建立植入物有望在手术后传递的体内作用力阈值。我们将回答四个研究问题。首先，通过改变体外培养条件，我们能显著改善修复结果吗？第二，正常肌腱传递的活体力的阈值是什么，这些力是如何在植入手术后通过修复部位分布的？第三，改变应用于体外构建物的机械信号是否会增强手术后的修复生物力学？最后，是否存在与体内结果相关的体外标记物，无论是短期还是长期？在一系列体外和体内研究中，将检验以下特定目标：1.使用选定的细胞种植密度、胶原浓度和胶原辫的组合作为缝线替代物，在培养中创建长达6周的MSC构建物。评估体外收缩特性、初始生物力学特性、细胞形态、胶原合成以及碱性磷酸酶和骨钙素的表达。2.在正常跟腱和髌腱上建立各种活动的活体负荷方案。3.利用有限元模型估算不同种植条件组合下修复组织中的载荷分布。4.根据SA2和SA3的设计标准，在体内评估从SA1中选择的组合，以确定植入物在替换受损组织方面的成功。5.评估连续和间歇循环应变对体外构建收缩、初始生物力学性能、细胞形态和生化的潜在益处。6.根据先前的研究目的，在体内评价SA5中最有希望的组合，以确定体外机械刺激对术后修复的生物力学、组织学和生化的潜在益处。7.通过将体外生物力学、组织学和生化结果与体内早期和长期结果相关联，确定可能预测体内结果的因素。

Our global hypothesis is that "functional" tissue-engineered constructs containing mesenchymal stem cells can be used in models of tendon injury to improve repair biomechanics, structure, and biochemistry. Implants will be designed in vitro with appropriate contraction characteristics and initial biomechanics to improve tendon repair. Functional tissue engineering or FTE will be used to mechanically stimulate the tissue engineered (TE) implants in culture and to establish thresholds of in vivo forces that the implants will be expected to transmit after surgery. We will address four research questions. First, can we significantly improve repair outcome by varying the in vitro culture conditions? Second, what are the thresholds of in vivo force transmitted by normal tendons and how are these forces distributed through the repair site after implant surgery? Third, would altering the mechanical signals applied to the constructs in vitro enhance repair biomechanics after surgery? Finally, do in vitro markers exist that correlate with in vivo outcome, both short and long term? In a series of in vitro and in vivo studies, the following Specific Aims will be examined: 1. Create MSC constructs for up to 6 weeks in culture using selected combinations of cell-seeding density, collagen concentration, and collagen braids as suture replacements. Evaluate in vitro contraction characteristics, initial biomechanical properties, cell morphology, collagen synthesis, and expression of alkaline phosphatase and osteocalcin. 2. Establish in vivo loading regimens on normal Achilles and patellar tendons for various activities. 3. Estimate load distributions in the repair tissues for different combinations of implant conditions using finite element modeling. 4. Evaluate in vivo selected combinations from SA1 in light of design criteria derived from SA2 and SA3 to determine the success of the implant in replacing the injured tissue. 5. Assess the potential benefits of continuous and intermittent cyclic strain on construct contraction, initial biomechanical properties, cell morphology, and biochemistry in vitro. 6. Evaluate in vivo the most promising combinations from SA5 in light of the previous aims to determine the potential benefits of in vitro mechanical stimulation on repair biomechanics, histology, and biochemistry after surgery. 7. Identify possible predictors of in vivo outcome by correlating in vitro biomechanical, histological, and biochemical results with early and long-term in vivo outcomes.