Nanomechanical characterization of the stiffness of eye lens cells: a pilot study.

Purpose: The purpose of this study is to probe the mechanical properties of individual eye lens cells isolated from nucleus and cortex of adult sheep eye lens, and to characterize the effect of cytoskeletal drugs.

Methods: We used atomic force microscopy (AFM), featuring a spherical tip at the end of a soft cantilever, to indent single lens cells, and measure the Young's modulus of isolated nuclear and cortical lens cells. Measurements were performed under basal conditions, and after addition of drugs that disrupt actin filaments and microtubules.

Results: We found that single lens cells were able to maintain their shape and mechanical properties after being isolated from the lens tissue. The median Young's modulus value for nuclear lens cells (4.83 kPa) was ~ 20-fold higher than for cortical lens cells (0.22 kPa). Surprisingly, disruption of actin filaments and microtubules did not affect the measured Young's moduli.

Conclusions: We found that single cells from the lens nucleus and cortex can be distinguished unambiguously using the elastic modulus as a criterion. The uncommon maintenance of shape and elastic properties after cell isolation together with the null effect of actin filaments and microtubules targeting drugs suggest that the mechanical stability of fiber cells is provided by cellular elements other than the usual cytoskeletal proteins.