Skeletal Muscle Tissue Engineering: From Tissue Regeneration to Biorobotics

Abstract

With its remarkable adaptability, energy efficiency, and mechanical compliance, skeletal muscle is a powerful source of inspiration for innovations in engineering and robotics. Originally driven by the clinical need to address large irreparable muscle defects, skeletal muscle tissue engineering (SMTE) has evolved into a versatile strategy reaching beyond medical applications into the field of biorobotics. This review highlights recent advancements in SMTE, including innovations in scaffold design, cell sourcing, usage of external physicochemical cues, and bioreactor technologies. Furthermore, this article explores the emerging synergies between SMTE and robotics, focusing on the use of robotic systems to enhance bioreactor performance and the development of biohybrid devices integrating engineered muscle tissue. These interdisciplinary approaches aim to improve functional recovery outcomes while inspiring novel biohybrid technologies at the intersection of engineering and regenerative medicine.

Fig. 1.

Anatomy of skeletal muscle tissue, illustrating the hierarchical structure from whole muscle down to sarcomeres. The contraction process involves interactions between actin and myosin filaments within the sarcomeres to generate force.

Fig. 2.

Myogenesis steps, from precursors cells of various sources to fully differentiated myotubes. As differentiation progresses, muscle cells express several transcription factors, including Myf5, MyoD, and MHC expressing subsequent level of maturation. Cell pictures are adapted from [137] with permission from Development.

Fig. 3.

External stimuli in SMTE. (A) Two weeks after seeding myoblasts on collagen-coated substrates, Engler et al. [64] stained for myosin (green) and nuclei (blue). Gels of intermediate stiffness showed notable actin–myosin striation, with an optimal reached for E = 12 kPa (scale bar: 20 μm). (B) Morphology of C2C12 cells after stimulation, investigated by Chen et al. [65] Sarcomere lengths increased with the strain ratios (scale bars: 200 μm). (C) Pulsative fluid shear stress doubled nitric oxide production and up-regulated proliferation marker expression in muscle stem cells, presented by Haroon et al. [67]. (D) Khodabukus et al. [68] studied the effects of electrical stimulation on myotube structure. Myobundles stained for α-actinin (red), filamentous actin (green), and nuclei (blue) showed an increase in striation, myotube length, and tetanic force for stimulated constructs. (E) Ahadian et al. [70] presented a contactless electrical stimulator for SMTE. The pH of the culture media remained stable over the time of culture when compared to traditional electrical stimulators, and expression of myogenic factors increased under a 10 V–1 Hz stimulation. (F) Supplementing myoblasts with IGF-1 resulted in enhanced MHC expression and higher fusion indexes after 5 d of culture, presented by Guan et al. [73] (scale bar: 100 μm). Permissions granted where necessary.

Fig. 4.

Examples of SMTE bioreactors. (A) Static monolayer culture bioreactors: petri dishes, tissue culture flasks (T-flasks), and well plates. (B) Bioreactors with mixed media: stirred flasks, rotating wall vessels, perfusion [138]. Rigid bioreactors: (C) mechanical cell stimulator (modified 6-well plate) by Powell et al. [139] and (D) the MagneTissue bioreactor (custom tube-inlet fitted into a modified falcon tube) by Heher et al. [140]. Flexible bioreactors: (E) pneumatic soft robotic in vitro platform for cell culture by Paek et al. [110] and (F) perfused flexible tubing lines hosting one bioconstruct each, fitted into a Plexiglas chamber, by Quarta et al. [141]. Permissions granted where necessary.

Fig. 5.

Complementary relationship between advanced robotic systems and SMTE. Musculoskeletal humanoid robots, like (A) “Eccerobot” [112], (B) “Kenshiro” [111], or (C) “Robody” [113], have the potential to serve as bioreactor platforms for SMTE. (D) Adapted shoulder from “Robody” hosting a tendon tissue construct, presented by Mouthuy et al. [114]. In return, skeletal muscle is a source of inspiration for artificial robotic systems. (E) Comparison between human quadriceps muscle structure and multifilament musculoskeletal McKibben muscle robot developed by Kurumaya et al. [117]. (F) Self-growing double-network hydrogels inspired by skeletal muscle mechanical training presented by Matsuda et al. [118]. Skeletal muscle can also be used as an actuator. Example of current muscle-actuated systems include (G) a 2D cantilever ridged system by Sun et al. [121], (H) a walker by Kinjo et al. [125], (I) a gripper by Morimoto et al. [124], and (J) a swimmer by Guix et al. [128]. (K) An 18-cm biohybrid hand, capable of moving individual fingers and manipulating objects by Ren et al. [129]. Permissions granted where necessary.