Stem cell migration and mechanotransduction on linear stiffness gradient hydrogels

TLDR

The spatial presentation of mechanical information is a key parameter for cell behavior. The authors developed a polymerization‑control method that creates tunable stiffness gradients at the cell‑matrix interface. Using this low‑cost, robust approach, polyacrylamide hydrogels with gradients ranging from 0.5 to 8.2 kPa mm⁻¹ were fabricated and used to study hASC morphology, migration, differentiation, and mechanosensitive protein expression. Three gradients proved non‑durotactic for hASCs, allowing a continuous stiffness spectrum in one well without migration bias, and analysis of YAP, Lamin A/C, Lamin B, MRTF‑A, and MRTF‑B revealed stiffness‑dependent expression and localization.

Abstract

The spatial presentation of mechanical information is a key parameter for cell behavior. We have developed a method of polymerization control in which the differential diffusion distance of unreacted cross-linker and monomer into a prepolymerized hydrogel sink results in a tunable stiffness gradient at the cell-matrix interface. This simple, low-cost, robust method was used to produce polyacrylamide hydrogels with stiffness gradients of 0.5, 1.7, 2.9, 4.5, 6.8, and 8.2 kPa/mm, spanning the in vivo physiological and pathological mechanical landscape. Importantly, three of these gradients were found to be nondurotactic for human adipose-derived stem cells (hASCs), allowing the presentation of a continuous range of stiffnesses in a single well without the confounding effect of differential cell migration. Using these nondurotactic gradient gels, stiffness-dependent hASC morphology, migration, and differentiation were studied. Finally, the mechanosensitive proteins YAP, Lamin A/C, Lamin B, MRTF-A, and MRTF-B were analyzed on these gradients, providing higher-resolution data on stiffness-dependent expression and localization.