Chen Xinyue, Bonfiglio Rita, Banerji Suneale, Jackson David G, Salustri Antonietta, Richter Ralf P
CIC biomaGUNE, San Sebastian, Spain; Max Planck Institute for Intelligent Systems, Stuttgart, Germany.
Department of Biomedicine and Prevention, Faculty of Medicine, University of Rome Tor Vergata, Rome, Italy.
Biophys J. 2016 Jun 21;110(12):2779-2789. doi: 10.1016/j.bpj.2016.03.023.
The cumulus cell-oocyte complex (COC) matrix is an extended coat that forms around the oocyte a few hours before ovulation and plays vital roles in oocyte biology. Here, we analyzed the micromechanical response of mouse COC matrix by colloidal-probe atomic force microscopy. We found that the COC matrix is elastic insofar as it does not flow and its original shape is restored after force release. At the same time, the COC matrix is extremely soft. Specifically, the most compliant parts of in vivo and in vitro expanded COC matrices yielded Young's modulus values of 0.5 ± 0.1 Pa and 1.6 ± 0.3 Pa, respectively, suggesting both high porosity and a large mesh size (≥100 nm). In addition, the elastic modulus increased progressively with indentation. Furthermore, using optical microscopy to correlate these mechanical properties with ultrastructure, we discovered that the COC is surrounded by a thick matrix shell that is essentially devoid of cumulus cells and is enhanced upon COC expansion in vivo. We propose that the pronounced nonlinear elastic behavior of the COC matrix is a consequence of structural heterogeneity and serves important functions in biological processes such as oocyte transport in the oviduct and sperm penetration.
卵丘细胞 - 卵母细胞复合体（COC）基质是一种在排卵前数小时围绕卵母细胞形成的扩展包被，在卵母细胞生物学中发挥着至关重要的作用。在此，我们通过胶体探针原子力显微镜分析了小鼠COC基质的微机械响应。我们发现，COC基质具有弹性，因为它不会流动，并且在力释放后其原始形状得以恢复。同时，COC基质极其柔软。具体而言，体内和体外扩展的COC基质中最柔顺部分的杨氏模量值分别为0.5±0.1 Pa和1.6±0.3 Pa，这表明其具有高孔隙率和大的网格尺寸（≥100 nm）。此外，弹性模量随着压痕的增加而逐渐增大。此外，利用光学显微镜将这些力学性能与超微结构相关联，我们发现COC被一层厚的基质壳所包围，该基质壳基本上没有卵丘细胞，并且在体内COC扩展时会增强。我们提出，COC基质明显的非线性弹性行为是结构异质性的结果，并且在诸如输卵管中卵母细胞运输和精子穿透等生物过程中发挥着重要作用。
