title: Micromechanical Analysis of the Hyaluronan-Rich Matrix Surrounding the Oocyte Reveals a Uniquely Soft and Elastic Composition.
abstract: 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.
authors.affiliation: CIC biomaGUNE, San Sebastian, Spain; Max Planck Institute for Intelligent Systems, Stuttgart, Germany.
authors.forename: Xinyue
authors.initials: X
authors.lastname: Chen
authors.affiliation: Department of Biomedicine and Prevention, Faculty of Medicine, University of Rome Tor Vergata, Rome, Italy.
authors.forename: Rita
authors.initials: R
authors.lastname: Bonfiglio
authors.affiliation: MRC Human Immunology Unit, Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, United Kingdom.
authors.forename: Suneale
authors.initials: S
authors.lastname: Banerji
authors.affiliation: MRC Human Immunology Unit, Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, United Kingdom.
authors.forename: David G
authors.initials: DG
authors.lastname: Jackson
authors.affiliation: Department of Biomedicine and Prevention, Faculty of Medicine, University of Rome Tor Vergata, Rome, Italy.
authors.forename: Antonietta
authors.initials: A
authors.lastname: Salustri
authors.affiliation: CIC biomaGUNE, San Sebastian, Spain; Max Planck Institute for Intelligent Systems, Stuttgart, Germany; Laboratory of Interdisciplinary Physics, University Grenoble Alpes-CNRS, Grenoble, France. Electronic address: rrichter@cicbiomagune.es.
authors.forename: Ralf P
authors.initials: RP
authors.lastname: Richter
mesh_terms: D000818:Animals; D004548:Elasticity / Q000502:physiology*; D005109:Extracellular Matrix / Q000378:metabolism* / Q000648:ultrastructure*; D005260:Female; D006820:Hyaluronic Acid / Q000378:metabolism*; D051379:Mice; D018625:Microscopy, Atomic Force; D009865:Oocytes / Q000378:metabolism* / Q000648:ultrastructure*; D061848:Optical Imaging; D014783:Viscosity
chemical_list: D006820:Hyaluronic Acid