Power law scaling in the mechanics of the developing mammalian retina

The mechanical properties of neuronal tissues determine how forces lead to movement and remodeling. In the mammalian retina, these forces are generated by activities on hour timescales, but mechanical measurements at these timescales do not exist. Recently, we directly probed the time-dependent mechanics of developing mammalian retina using ferrofluid droplets in mouse stem cell-derived organoids. By recording strain under constant stress across four orders of magnitude in time (up to one hour), we discovered that the tissue compliance follows a power law with exponent 0.14 ± 0.05, suggesting that neuronal tissue remodels in a scale-free manner. This weak scaling indicates semi-solid properties, consistent with a material just above its glass transition. This could explain how the developing retina balances competing requirements of formation and function. During formation, the retina must maintain some fluidity to relax stresses and refine neuronal architecture as it grows. Conversely, optimal visual system performance demands high neuron density, favoring a solid, crystalline packing. By quantifying the time-dependent mechanical properties, we gain insights into how mechanics drives movement and connectivity in the retina and central nervous system.