Division of Engineering, Saint Mary's University, Halifax, Canada.
Division of Engineering, Saint Mary's University, Halifax, Canada; School of Biomedical Engineering, Dalhousie University, Halifax, Canada.
J Biomech. 2020 May 7;104:109720. doi: 10.1016/j.jbiomech.2020.109720. Epub 2020 Mar 2.
Despite many in vitro mechanical experiments of tendon being conducted at room temperature, few assessments have been made to determine how the structural response of tendon to mechanical overload may vary with ambient temperature. We explored whether damage to the collagen nanostructure of tendon resulting from tensile rupture varies with temperature. Use of bovine tail tendons in combination with NaBH crosslink stabilization treatment allowed us to probe the mechanisms underlying the observed changes. Untreated tendons and NaBH-stabilized tendons were pulled to rupture at temperatures of 24, 37, and 55 °C. Of nine mechanical parameters measured from the resulting stress-strain curves, only yield stress differed between the tendons tested at 37 and 24 °C. When tested at 55 °C, untreated tendons showed large reductions in ultimate strength and toughness, while NaBH-stabilized tendons showed smaller reductions. Differential scanning calorimetry was used to assess damage to the collagen fibril nanostructure of tendons resulting from rupture, with samples from the ruptured tendons compared to samples from the same tendons removed prior to loading. While there was indication that overload-induced molecular packing disruption to collagen fibrils may be heightened at 37 °C, statistical increases in damage compared to that occurring at 24 °C were only seen when testing was conducted at 55 °C. The results show that the temperature sensitivity of tendon to ramp loading depends on crosslinking within the tissue. In poorly crosslinked tissues, collagen may be more susceptible to mechanical damage when tested at physiologic temperature compared to room temperature. For tendons with a high density of thermally stable crosslinks, such as the human Achilles or patellar tendons, testing at room temperature should produce comparable results to testing at physiologic temperature.
尽管有许多在室温下进行的肌腱体外力学实验，但很少有评估来确定肌腱对机械过载的结构响应如何随环境温度而变化。我们探讨了肌腱胶原纳米结构因拉伸破坏而导致的损伤是否随温度而变化。使用牛尾肌腱结合 NaBH 交联稳定处理，使我们能够探测到观察到的变化背后的机制。未处理的肌腱和 NaBH 稳定的肌腱在 24、37 和 55°C 的温度下被拉至断裂。在所得到的应力-应变曲线上测量的九个力学参数中，只有在 37 和 24°C 下测试的肌腱之间的屈服应力有所不同。当在 55°C 下测试时，未处理的肌腱的极限强度和韧性明显降低，而 NaBH 稳定的肌腱的降低幅度较小。差示扫描量热法用于评估由于断裂而导致肌腱胶原原纤维纳米结构的损伤，将来自断裂肌腱的样品与加载前从相同肌腱中取出的样品进行比较。虽然有迹象表明，在 37°C 时，过载诱导的胶原原纤维分子堆积破坏可能会加剧，但只有在 55°C 下进行测试时，与在 24°C 时相比，才会出现统计学上的损伤增加。结果表明，肌腱对斜坡加载的温度敏感性取决于组织内的交联。在交联不良的组织中，与在室温下相比，在生理温度下测试时，胶原可能更容易受到机械损伤。对于具有高热稳定性交联密度的肌腱，如人类跟腱或髌腱，在室温下进行测试应产生与生理温度下测试相当的结果。
