Scale invariance of mechanical properties in the developing mammalian retina

Abstract

Neuronal tissues, like the retina, form through physical forces which induce remodeling over a range of time and length scales. How these mechanical stresses accumulate and relax during retinogenesis is unknown due to the difficulty in applying stress in situ from seconds to hours in living neuronal tissue. In non-neuronal tissue and 2D cell culture, previous studies have revealed that material properties exhibit scale-free behavior. Whether this translates to developing neuronal tissues has remained an open question.

Here we demonstrate the existence of scale-free rheology in 3D neuronal tissue. We probed time-dependent tissue mechanics in an in vitro model of the developing retina using magnetic droplets in mouse stem cell-derived retina organoids. We recorded strain responses to an applied stress across four orders of magnitude in time, up to one hour. Dynamic creep compliance and tensile moduli followed a power law with an exponent consistent with a material just above the glass transition. Our findings demonstrate that neuronal tissue remodels in a scale-free manner, prompting the question of whether scale-invariant mechanical properties are a general motif of neurodevelopment.