Melt electrowritten microfiber-hydrogel composite scaffolds with local cross-bridging reinforcements for aligned...

Effective regeneration of skeletal muscle with highly aligned fiber architecture remains a significant challenge in tissue engineering. Structural alignment of muscle constructs along with mechanical integrity are crucial for effective engineering of grafts and microphysiological systems. This study introduced a composite microfiber-hydrogel platform using melt electrowriting (MEW) with a reinforcing architecture for aligned fiber scaffolds that maintains directional consistency while providing mechanical cohesion. Three MEW scaffold designs (Isotropic, Aligned T with perpendicular fiber reinforcements, and Aligned X with local cross-bridging fiber reinforcements) were developed and fabricated into composite scaffolds with collagen hydrogels and seeded with myoblasts. Aligned X scaffolds with cross-bridge reinforcements exhibited enhanced mechanical strength and continuous alignment without structural interruption that led to highly aligned and multinucleated cellular organization. The incorporation of collagen hydrogel improved cell seeding efficiency, viability, and metabolic activity compared to scaffolds alone. All scaffold designs provided fiber reinforcement that prevented hydrogel contraction. The Aligned X architecture increased myogenic differentiation, evidenced by increased myosin heavy chain expression and myotube diameter. This effect was attributed to topographical cues of alignment and mechanotransduction signaling measured by YAP nuclear localization. Overall, this composite microfiber-hydrogel approach provides structurally stable and highly aligned platform for enhanced muscle tissue engineering applications, representing an advancement towards clinical challenges associated with muscle injuries. STATEMENT OF SIGNIFICANCE: The study introduces large and highly aligned tissue engineered composite constructs of skeletal muscle using a natural hydrogel and a microfiber scaffold. The approach enables large and scalable tissue constructs with robust mechanical integrity that resists soft tissue contraction, a challenge in tissue engineering. Moreover, a new reinforcing scheme for aligned scaffolds is used to fabricate a scaffold architecture termed Aligned X, that provided structural integrity and geometrical continuity of aligned fiber walls. The composite system enabled formation of highly aligned and multinucleated myotubes while maintaining bulk construct shape by resisting cell-mediated contractions. The Aligned X architecture significantly improved myogenic differentiation and maturation, and induced increased mechanosensitive signaling.