Lynch Barbara, Bancelin Stéphane, Bonod-Bidaud Christelle, Gueusquin Jean-Baptiste, Ruggiero Florence, Schanne-Klein Marie-Claire, Allain Jean-Marc
LMS, Ecole Polytechnique, CNRS, Université Paris-Saclay, Palaiseau, France.
LOB, Ecole Polytechnique, CNRS, INSERM, Université Paris-Saclay, Palaiseau, France.
Acta Biomater. 2017 Mar 1;50:302-311. doi: 10.1016/j.actbio.2016.12.051. Epub 2016 Dec 30.
Skin is a complex, multi-layered organ, with important functions in the protection of the body. The dermis provides structural support to the epidermal barrier, and thus has attracted a large number of mechanical studies. As the dermis is made of a mixture of stiff fibres embedded in a soft non-fibrillar matrix, it is classically considered that its mechanical response is based on an initial alignment of the fibres, followed by the stretching of the aligned fibres. Using a recently developed set-up combining multiphoton microscopy with mechanical assay, we imaged the fibres network evolution during dermis stretching. These observations, combined with a wide set of mechanical tests, allowed us to challenge the classical microstructural interpretation of the mechanical properties of the dermis: we observed a continuous alignment of the collagen fibres along the stretching. All our results can be explained if each fibre contributes by a given stress to the global response. This plastic response is likely due to inner sliding inside each fibre. The non-linear mechanical response is due to structural effects of the fibres network in interaction with the surrounding non-linear matrix. This multiscale interpretation explains our results on genetically-modified mice with a simple alteration of the dermis microstructure.
Soft tissues, as skin, tendon or aorta, are made of extra-cellular matrix, with very few cells embedded inside. The matrix is a mixture of water and biomolecules, which include the collagen fibre network. The role of the collagen is fundamental since the network is supposed to control the tissue mechanical properties and remodeling: the cells attach to the collagen fibres and feel the network deformations. This paper challenges the classical link between fibres organization and mechanical properties. To do so, it uses multiscale observations combined to a large set of mechanical loading. It thus appears that the behaviour at low stretches is mostly controlled by the network structural response, while, at large stretches, the fibre inner-sliding dominate.
皮肤是一个复杂的多层器官，在保护身体方面具有重要功能。真皮为表皮屏障提供结构支撑，因此吸引了大量的力学研究。由于真皮由嵌入柔软非纤维基质中的硬纤维混合物组成，传统上认为其力学响应基于纤维的初始排列，随后是排列好的纤维的拉伸。我们使用最近开发的将多光子显微镜与力学检测相结合的装置，对真皮拉伸过程中纤维网络的演变进行了成像。这些观察结果与一系列广泛的力学测试相结合，使我们能够挑战对真皮力学性能的经典微观结构解释：我们观察到胶原纤维在拉伸过程中持续排列。如果每根纤维对整体响应贡献一定的应力，那么我们所有的结果都可以得到解释。这种塑性响应可能是由于每根纤维内部的滑动。非线性力学响应是由于纤维网络与周围非线性基质相互作用的结构效应。这种多尺度解释解释了我们在真皮微观结构有简单改变的转基因小鼠上得到的结果。
软组织，如皮肤、肌腱或主动脉，由细胞外基质组成，内部嵌入的细胞很少。基质是水和生物分子的混合物，其中包括胶原纤维网络。胶原的作用至关重要，因为该网络被认为控制着组织的力学性能和重塑：细胞附着在胶原纤维上并感受网络的变形。本文挑战了纤维组织与力学性能之间的经典联系。为此，它使用了多尺度观察结果并结合了大量的力学加载。因此，似乎在低拉伸时的行为主要由网络结构响应控制，而在大拉伸时，纤维内部滑动起主导作用。
