Effect of Fibronectin and Laminin on Compaction of Myoblast-Seeded Collagen Hydrogels.

The extracellular matrix (ECM) regulates skeletal muscle development through biochemical signaling and mechanical interactions. While Matrigel supplementation is commonly used to enhance engineered muscle formation, the contribution of specific ECM proteins remain incompletely defined in 3D systems. Here, we evaluated the effects of laminin and fibronectin supplementation on myogenic differentiation in collagen type I hydrogels and assessed their influence on passive tissue compaction and alignment in 3D constructs. Two-dimensional collagen hydrogels supplemented with increasing concentrations (0-100 µg/mL) of laminin or fibronectin were screened to maximize the myoblast fusion index. These concentrations were incorporated into 3D myocyte-seeded hydrogels cultured between flexible posts to quantify passive compaction forces via cantilever mechanics. Fibronectin supplementation (10 µg/mL) resulted in significantly greater early post displacement and sustained passive compaction compared to laminin-supplemented and unsupplemented controls. Constructs cultured under tension between posts exhibited enhanced alignment, with fibronectin further increasing the proportion of fibers oriented within 0-20° of the tension axis. Together, these findings demonstrate that fibronectin enhances early passive compaction dynamics and tension-mediated alignment in collagen-based skeletal muscle constructs. These results provide insight into how specific ECM components influence 3D tissue organization and may inform the design of engineered muscle models for regenerative applications.