Tuning local matrix compliance accelerates mesenchymal stem cell chondrogenesis in 3D sliding hydrogels

The mechanical properties of the extracellular matrix critically regulate stem cell differentiation in 3D. Alginate hydrogels with tunable bulk stiffness and viscoelasticity can modulate differentiation in 3D through mechanotransduction. Such enhanced differentiation is correlated with changes in the local matrix compliance- the extent of matrix deformation under applied load. However, the causal effect of local matrix compliance changes without altering bulk hydrogel mechanics on stem cell differentiation remains unclear. To address this, we report sliding hydrogel (SG) designs with tunable local matrix compliance obtained by varying the molecular mobility of the hydrogel network without changing bulk mechanics. Atomic force microscopy showed increasing SG mobility allowed cells to increasingly deform local niches with lesser forces, indicating higher local matrix compliance. Increasing SG mobility accelerates MSC chondrogenesis in a mobility-dependent manner and is independent of exogenous adhesive ligands or cell volume expansion. The enhanced chondrogenesis in SG is accompanied by enhanced cytoskeletal organization and TRPV4 expression, and blocking these elements abolished the effect. In conclusion, this study establishes a causal link between local matrix compliance and stem cell differentiation and establishes it as a crucial hydrogel design parameter. Furthermore, it offers novel SG designs to probe the role of local matrix compliance in various biological processes.