Collagen fibrils in functionally distinct tendons have differing structural responses to tendon rupture and fatigue loading
Collagen fibrils in functionally distinct tendons have differing structural responses to tendon rupture and fatigue loading
复制标题
DOI：
10.1016/j.actbio.2016.06.017
复制
发表时间：
2016-09-15
影响因子：
9.7
通讯作者：
Veres, Samuel P.
中科院分区：
文献类型：
--
作者：
Herod, Tyler W.;Chambers, Neil C.;Veres, Samuel P.
在这项研究中，我们研究了胶原纤维的纳米级结构和胶原组织的宏观功能反应之间的关系。要做到这一点，我们研究了两个功能不同的类肌腱，位置肌腱和储能肌腱，使用牛前肢模型。使用差示扫描量热法（DSC）进行分子水平评估，使用水热等长张力（HIT）分析进行功能交联评估，使用扫描电子显微镜（SEM）进行超微结构评估，用于研究两种肌腱类型的未受损、断裂和循环加载样本。HIT表明交联类型和交联密度存在差异，屈肌腱比伸肌肌腱具有更高的热稳定交联（>90与75.1 +/- 2.7 ℃的较高T-Fmax），总交联密度比伸肌肌腱更高（NaBH 4处理后t（1/2）为11.5 +/- 1.9与3.5 +/- 1.0 h）。尽管屈肌腱的交联密度较低，但伸肌肌腱明显更强（37.6 +/- 8.1对23.1 +/- 7.7 MPa）和更坚韧（14.3 +/- 3.6对6.8 +/- 3.4 Mj/m（3））。扫描电镜显示，胶原纤维在更强硬，更强的伸肌肌腱能够进行显着水平的塑性变形的形式离散塑性，而在屈肌腱不能塑性变形。当循环加载时，胶原纤维在伸肌腱中以扭结带的形式迅速累积疲劳损伤，而在屈肌腱中没有累积显著的疲劳损伤。结果表明，胶原纤维在功能不同的肌腱响应不同的机械负荷，并表明，纤维状胶原蛋白可能会受到强度与抗疲劳性tradeoff.Statement的SignificanceCollagen纤维纳米生物电缆是所有结构人体组织的基本承重元素。虽然所有胶原原纤维都具有共同的特征，例如由三螺旋胶原分子的精确四分之一交错聚合物排列组成，但它们的结构在组织类型之间，甚至在相同组织类型的不同解剖结构之间可以显著变化。为了了解胶原组织的正常功能、稳态和疾病，需要对胶原纤维结构-功能有详细的了解。使用解剖学上接近，但结构不同的肌腱，我们表明，胶原纤维在功能不同的肌腱有不同的probabilities下的拉伸过载和循环疲劳载荷的损害。我们的结果表明，胶原纤维的结构可能会导致强度与抗疲劳性的权衡，其中以牺牲抗疲劳性为代价获得高强度，反之亦然。(C)2016 Acta Materialia Inc.由爱思唯尔有限公司出版。保留所有权利。
In this study we investigate relationships between the nanoscale structure of collagen fibrils and the macroscale functional response of collagenous tissues. To do so, we study two functionally distinct classes of tendons, positional tendons and energy storing tendons, using a bovine forelimb model. Molecular-level assessment using differential scanning calorimetry (DSC), functional crosslink assessment using hydrothermal isometric tension (HIT) analysis, and ultrastructural assessment using scanning electron microscopy (SEM) were used to study undamaged, ruptured, and cyclically loaded samples from the two tendon types. HIT indicated differences in both crosslink type and crosslink density, with flexor tendons having more thermally stable crosslinks than the extensor tendons (higher T-Fmax of >90 vs. 75.1 +/- 2.7 degrees C), and greater total crosslink density than the extensor tendons (higher t(1/2) of 11.5 +/- 1.9 vs. 3.5 +/- 1.0 h after NaBH4 treatment). Despite having a lower crosslink density than flexor tendons, extensor tendons were significantly stronger (37.6 +/- 8.1 vs. 23.1 +/- 7.7 MPa) and tougher (14.3 +/- 3.6 vs. 6.8 +/- 3.4 Mj/m(3)). SEM showed that collagen fibrils in the tougher, stronger extensor tendons were able to undergo remarkable levels of plastic deformation in the form of discrete plasticity, while those in the flexor tendons were not able to plastically deform. When cyclically loaded, collagen fibrils in extensor tendons accumulated fatigue damage rapidly in the form of kink bands, while those in flexor tendons did not accumulate significant fatigue damage. The results demonstrate that collagen fibrils in functionally distinct tendons respond differently to mechanical loading, and suggests that fibrillar collagens may be subject to a strength vs. fatigue resistance tradeoff.Statement of SignificanceCollagen fibrils-nanoscale biological cables-are the fundamental load-bearing elements of all structural human tissues. While all collagen fibrils share common features, such as being composed of a precise quarter-staggered polymeric arrangement of triple-helical collagen molecules, their structure can vary significantly between tissue types, and even between different anatomical structures of the same tissue type. To understand normal function, homeostasis, and disease of collagenous tissues requires detailed knowledge of collagen fibril structure-function. Using anatomically proximate but structurally distinct tendons, we show that collagen fibrils in functionally distinct tendons have differing susceptibilities to damage under both tensile overload and cyclic fatigue loading. Our results suggest that the structure of collagen fibrils may lead to a strength versus fatigue resistance tradeoff, where high strength is gained at the expense of fatigue resistance, and vice versa. (C) 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.