Acta Biomaterialia ( IF 9.4 ) Pub Date : 2023-10-05 , DOI: 10.1016/j.actbio.2023.09.047 Niamh Hennessy 1 , Ciaran Simms 1
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The mechanical and structural properties of passive skeletal muscle are important for musculoskeletal models in impact biomechanics, rehabilitation engineering and surgical simulation. Passive properties of skeletal muscle depend strongly on the architecture of the extracellular matrix (ECM), but the structure of ECM and its realignment under applied deformation remain poorly understood. We apply second harmonic generation (SHG) microscopy to study muscle ECM in intact muscle samples both under deformation and in the undeformed state. A method for regional relocation was developed, so that the same ECM segment could be viewed before and after applying deformations. Skeletal muscle ECM was viewed at multiple scales and in three states: undeformed, under compression and under tension. Results show that second harmonic generation microscopy provides substantial detail of skeletal muscle ECM over a wide range of length scales, especially the perimysium structure. We present images of individual portions of skeletal muscle ECM both undeformed and subjected to tensile/compressive deformation. We also present data showing the response of the perimysium to a partial thickness cut applied to a section under tensile deformation.
Statement of significance
Second Harmonic Generation (SHG) microscopy is an imaging technique which takes advantage of a non-linear and coherent frequency doubling optical effect that is present in a small number of biological molecules, primarily collagen Type I, II and myosin. Collagen I is the most abundant collagen type in skeletal muscle, making SHG a promising option for visualisation of the skeletal muscle extracellular matrix (ECM). SHG microscopy does not require fixing or staining. This short communication presents the application of SHG microscopy to skeletal muscle ECM to improve our understanding of how collagen fibres reorganise under applied tensile and compression, including microscopic observations of collagen fibre reorganisation for intact samples by using a method to re-identify specific regions in repeated deformation tests.
中文翻译：
使用二次谐波发生显微镜观察施加变形下的骨骼肌细胞外基质结构
被动骨骼肌的机械和结构特性对于冲击生物力学、康复工程和手术模拟中的肌肉骨骼模型非常重要。骨骼肌的被动特性在很大程度上取决于细胞外基质 (ECM) 的结构，但 ECM 的结构及其在施加变形下的重新排列仍然知之甚少。我们应用二次谐波发生 (SHG) 显微镜来研究变形和未变形状态下完整肌肉样本中的肌肉 ECM。开发了一种区域重定位方法，以便在应用变形之前和之后可以查看相同的 ECM 片段。骨骼肌 ECM 在多种尺度和三种状态下进行观察：未变形、受压和受拉。结果表明，二次谐波显微镜可提供各种长度尺度上骨骼肌 ECM 的大量细节，尤其是肌束膜结构。我们展示了骨骼肌 ECM 各个部分的未变形和拉伸/压缩变形的图像。我们还提供了显示肌束膜对拉伸变形下部分厚度切割的响应的数据。
重要性声明
二次谐波发生 (SHG) 显微镜是一种成像技术，利用少量生物分子（主要是 I 型、II 型胶原蛋白和肌球蛋白）中存在的非线性和相干倍频光学效应。 I 型胶原蛋白是骨骼肌中最丰富的胶原蛋白类型，这使得 SHG 成为骨骼肌细胞外基质 (ECM) 可视化的有前途的选择。 SHG 显微镜不需要固定或染色。这篇简短的交流介绍了 SHG 显微镜在骨骼肌 ECM 中的应用，以提高我们对胶原纤维在施加拉伸和压缩下如何重组的理解，包括通过使用重复识别特定区域的方法对完整样品的胶原纤维重组进行显微观察变形测试。
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