Mechanobiological properties can be indicative of cellular health and function [1]. For the oocyte, mechanobiological information provided via the cumulus matrix may impact developmental potential. Here, we propose a means to accurately measure these properties in situ using optical tweezers – a technique that uses tightly focused light to trap micron-sized particles in 3D [2]. In trapping microscopic dielectric spheres, we can generate a local probe to measure viscoelasticity of the cumulus-oocyte complex extracellular matrix (ECM). Here, we aim to corroborate viscoelastic profiles of cumulus ECM with subsequent pre- and post-natal outcomes in mice.
To examine whether the viscoelasticity of cumulus ECM correlates with oocyte developmental potential, we established a model of decreasing oocyte quality using three methods of oocyte maturation; (1) in vivo, (2) in vitro, and (3) compromised in vitro . The ECM was isolated following oocyte maturation using hyaluronidase and then mixed with 1 µm silica beads. Viscoelasticity was quantified by trapping microbeads and using equipartition and power spectrum density analysis. Viscoelastic measurements of the ECM will be correlated with oocyte developmental potential (cumulus expansion, fertilisation rate, development to the blastocyst-stage, foetal viability and placenta development).
Cumulus expansion was significantly lower in the compromised in vitro group when compared to standard in vitro maturation (P < 0.05). Fertilisation rate did not differ between the three maturation methods (P > 0.05), however, fewer embryos developed to the blastocyst stage in the standard in vitro and compromised in vitro maturation groups when compared to the in vivo matured group. Viscoelasticity measurements of the ECM will be correlated with developmental outcomes.
Using this model, we will explore the application of optical tweezers to further understand how the microenvironment of the oocyte during maturation impacts developmental potential.