Department of Biomedical Engineering, University of Delaware, Newark, USA.
J Anat. 2019 Feb;234(2):252-262. doi: 10.1111/joa.12913. Epub 2018 Nov 28.
Rodent tendons are widely used to study human pathologies such as tendinopathy and repair, and to address fundamental physiological questions about development, growth, and remodeling. However, how the gross morphology and multi-scale hierarchical structure of rat tendons, such as the tail, plantaris, and Achilles tendons, compare with that of human tendons are unknown. In addition, there remains disagreement about terminology and definitions. Specifically, the definitions of fascicle and fiber are often dependent on diameter sizes, not their characteristic features, and these definitions impair the ability to compare hierarchical structure across species, where the sizes of the fiber and fascicle may change with animal size and tendon function. Thus, the objective of the study was to select a single species that is commonly used for tendon research (rat) and tendons with varying mechanical functions (tail, plantaris, Achilles) to evaluate the hierarchical structure at multiple length scales using histology, SEM, and confocal imaging. With the exception of the specialized rat tail tendon, we confirmed that in rat tendons there are no fascicles and the fiber is the largest subunit. In addition, we provided a structurally based definition of a fiber as a bundle of collagen fibrils that is surrounded by elongated cells, and this definition was supported by both histologically processed and unprocessed samples. In all rat tendons studied, the fiber diameters were consistently between 10 and 50 μm, and this diameter range appears to be conserved across larger species. Specific recommendations were made highlighting the strengths and limitations of each rat tendon as a research model. Understanding the hierarchical structure of tendon can advance the design and interpretation of experiments and development of tissue-engineered constructs.
啮齿动物的肌腱被广泛用于研究人类病理，如腱病和修复，并解决关于发育、生长和重塑的基本生理问题。然而，鼠类肌腱（如尾巴、跖肌和跟腱）的大体形态和多层次的层次结构与人类肌腱的比较情况尚不清楚。此外，术语和定义也存在分歧。具体来说，束和纤维的定义通常取决于直径大小，而不是其特征，这些定义损害了跨物种比较层次结构的能力，在跨物种比较中，纤维和束的大小可能会随着动物体型和肌腱功能的变化而变化。因此，本研究的目的是选择一种常用于肌腱研究的单一物种（鼠）和具有不同机械功能的肌腱（尾巴、跖肌、跟腱），以使用组织学、SEM 和共聚焦成像来评估多个长度尺度的层次结构。除了特殊的鼠尾肌腱外，我们确认在鼠肌腱中没有束，纤维是最大的亚单位。此外，我们提供了一种基于结构的纤维定义，即纤维是由胶原原纤维束组成的，被拉长的细胞包围，这个定义得到了组织学处理和未处理样本的支持。在所研究的所有鼠肌腱中，纤维直径始终在 10 到 50 微米之间，这个直径范围似乎在更大的物种中是保守的。我们提出了一些具体的建议，强调了每种鼠肌腱作为研究模型的优势和局限性。了解肌腱的层次结构可以促进实验的设计和解释以及组织工程构建体的开发。
