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

Abstract

AbstractThe understanding of multiscale load transfer within complex soft tissues is incomplete. The eye lens is ideal for multiscale tissue mechanics studies as its principal function is to fine focus light at different distances onto the retina via mechanical shape changes. The biomechanical function, resiliency, and intricate microstructure of the lens make it an excellent non-connective soft tissue model. We hypothesized that compressive strain applied onto whole lens tissue leads to deformation of specific microstructures and that this deformation is reversible following removal of load. 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 of the lenses. At the equatorial region, strain ≥6% increases fiber cell widths. The effects of strain on lens epithelial cell area, capsule thickness, and equatorial fiber cell widths are reversible following the release of lenses from strain. However, although fiber cell tip separation following the removal of low loads is reversible, the separation becomes irreversible with application of higher loads. This irreversible separation between fiber cell tips leads to incomplete bulk lens resiliency. The lens is an accessible biomechanical model system that provides new insights on multiscale transfer of loads in soft tissues.