Peterson Benjamin E, Szczesny Spencer E
Department of Biomedical Engineering, Pennsylvania State University, University Park PA.
Department of Biomedical Engineering, Pennsylvania State University, University Park PA; Department of Orthopaedics and Rehabilitation, Pennsylvania State University, Hershey PA.
Acta Biomater. 2020 Nov;117:302-309. doi: 10.1016/j.actbio.2020.09.046. Epub 2020 Sep 30.
While collagen fibrils are understood to be the primary load-bearing elements in tendon, controversy still exists on how fibrils functionally transmit load from muscle to bone. Specifically, it's unclear whether fibrils are structurally continuous along the tendon length and bear load independently, or if they are discontinuous and transfer load through interfibrillar shear forces. To address this question, we investigated whether the multiscale mechanics of rat tail tendon fascicles is dependent on sample gauge length. We hypothesized that as the grip-to-grip length is reduced and approaches the length of the collagen fibrils, tendon fascicles will adopt a multiscale mechanical response consistent with structurally continuous fibrils. Our findings show that, for gauge lengths of 20 mm or greater, the local fibril strains are less than the bulk tissue strains, which can be explained by relative sliding between discontinuous collagen fibrils. In contrast, at a 5 mm gauge length, the fibril strains are equivalent to the applied tissue strains, suggesting that the collagen fibrils are structurally continuous between the grips. Additionally, the macroscale tissue modulus is increased at gauge lengths of 5 and 10 mm. Together, these data support the hypothesis that collagen fibrils in rat tail tendon fascicles are discontinuous and also suggest that their length is between 5 and 10 mm. This fundamental information regarding tendon structure-function relationships underscores the importance of the tissue components that transmit load between fibrils and is critical for understanding tendon pathology as well as establishing structural benchmarks for suitable tissue engineered replacements.
虽然胶原纤维被认为是肌腱中主要的承重元件，但关于纤维如何将负荷从肌肉功能性地传递到骨骼仍存在争议。具体而言，尚不清楚纤维在肌腱长度上是否结构连续并独立承受负荷，或者它们是否不连续并通过纤维间剪切力传递负荷。为了解决这个问题，我们研究了大鼠尾腱束的多尺度力学是否取决于样本标距长度。我们假设，随着夹距长度减小并接近胶原纤维的长度，肌腱束将呈现与结构连续纤维一致的多尺度力学响应。我们的研究结果表明，对于20毫米或更长的标距长度，局部纤维应变小于整体组织应变，这可以通过不连续胶原纤维之间的相对滑动来解释。相比之下，在5毫米的标距长度下，纤维应变与施加的组织应变相当，这表明胶原纤维在夹具之间结构连续。此外，在5毫米和10毫米的标距长度下，宏观组织模量增加。总之，这些数据支持大鼠尾腱束中的胶原纤维是不连续的这一假设，并且还表明它们的长度在5到10毫米之间。这种关于肌腱结构 - 功能关系的基本信息强调了在纤维之间传递负荷的组织成分的重要性，对于理解肌腱病理学以及为合适的组织工程替代物建立结构基准至关重要。
