Bio-inspired micropatterned hydrogel to direct and deconstruct hierarchical processing of geometry-force signals by human mesenchymal stem cells during smooth muscle cell differentiation

Micropatterned biomaterial-based hydrogel platforms allow the recapitulation of in vivo-like microstructural and biochemical features that are critical physiological regulators of stem cell development. Herein, we report the use of muscle mimicking geometries patterned on polyacrylamide hydrogels as an effective strategy to induce smooth muscle cell (SMC) differentiation of human mesenchymal stem cells (hMSCs). hMSCs were systemically coerced to elongate with varying aspect ratios (AR) (that is, 1:1, 5:1, 10:1 and 15:1) at a fixed projection area of ~7000 μm2. The results showed engineered cellular anisotropy with an intermediate AR 5:1 and AR 10:1, promoting the expression of alpha smooth muscle actin (α-SMA) and enhancement of contractile output. Further mechanistic studies indicated that a threshold cell traction force of ~3.5 μN was required for SMC differentiation. Beyond the critical cytoskeleton tension, hMSCs respond to higher intracellular architectural cues such as the stress fiber (SF) alignment, SF subtype expression and diphosphorylated myosin regulatory light-chain activity to promote the expression and incorporation of α-SMA to the SF scaffold. These findings underscore the importance of exploiting biomimetic geometrical cues as an effective strategy to guide hMSC differentiation and are expected to guide the rational design of advanced tissue-engineered vascular grafts. Muscle-mimicking geometries patterned on hydrogel facilitate the acquisition of a smooth-muscle-cell-like phenotype from human stem cells. Adult mesenchymal stem cells (MSCs) are a valuable source of cells for regenerative medicine. Now, researchers in Singapore and China have examined the complex interdependence of engineered cell shape and human transforming growth factor beta-1 treatment to direct smooth muscle cells differentiation of MSCs. They discovered that geometries resembling those of human smooth muscle cells provide the optimal shape for the expression and recruitment of the mechano-sensitive protein α-smooth muscle actin to the filamentous actin cytoskeleton. Based on these results, the researchers proposed an elegant model to describe the decision-making process that human MSCs take during differentiation into smooth muscle cells. The findings highlight the importance of using biomimetic cues for guiding differentiation of human MSCs. Inspired by the intrinsic morphology of smooth muscle cells (SMCs), a micropatterned hydrogel is developed to direct and define the boundary conditions for efficient SMC differentiation of human mesenchymal stem cells (hMSCs). The results show that in conjunction with TGF-β1 treatment, muscle-mimicking shapes with intermediate aspect ratios ranging from 5:1 to 10:1 exert the strongest pro-SMC differentiation effects in a structural–contractile force-dependent manner. These findings are expected to provide critical insights and design rules for vascular-related engineered tissue grafts.