The effects of mechanical strain on mouse eye lens capsule and cellular microstructure

The understanding of multiscale load transfer within complex soft tissues is incomplete. The eye lens is ideal for multiscale mechanical studies because its principal function is to fine-focus light at different distances onto the retina via shape changes. The biomechanical function, resiliency, and intricate microstructure of the lens makes it an excellent nonconnective soft tissue model. We hypothesized that strain applied onto whole-lens tissue leads to deformation of specific microstructures and that this deformation is reversible following load removal. For this examination, mouse lenses were compressed by sequential application of increasing load. Using confocal microscopy and quantitative image analysis, we determined that axial strain >= 10% reduces capsule thickness, expands epithelial cell area, and separates fiber cell tips at the anterior region. At the equatorial region, strain >= 6% increases fiber cell widths. The effects of strain on lens epithelial cell area, capsule thickness, and fiber cell widths are reversible following the release from strain. However, the separation of fiber cell tips is irreversible at high loads. This irreversible separation between fiber cell tips leads to incomplete whole-lens resiliency. The lens is an accessible biomechanical model system that provides new insights on multiscale transfer of loads in soft tissues.