FIG. 6.

Maturation of tissue engineered muscle. (a) Indications of maturity in (i) non-printed 3D culture of C2C12 s in muscle dECM demonstrates (ii) multinucleated myotubes by day 3 (scale bar 50 μm) and (iii) the beginning of striations by day 6 (arrows) (scale bar 25 μm). (b) Graphic of extrusion printing biofabrication process. (c) Comparison of 3D culture and 3D fabrication (ITOP system) of primary human muscle progenitors in a gelatin/HA/fibrinogen/glycerol bioink, showing alignment enabled through printing-induced placement and tensional forces from PCL supporting material. (i) Viability in printed and non-printed materials at 1 and 5 days. (ii) Staining of maturation markers, where myosin heavy chain and DAPI staining demonstrate multinucleated myofibers after 7 days of differentiation. (iii) α-sarcomeric actin, laminin, and DAPI staining of deposited ECM protein and striations of contractile protein. (a) Adapted and reproduced with permission from Chaturvedi et al., PLoS One 10(6), e0127675 (2015). Copyright 2015 Authors, licensed under a Creative Commons Attribution (CC BY) license.¹² (c) Reproduced with permission from Kim et al., Sci. Rep. 8(1), 12307 (2018). Copyright 2018 Authors, licensed under a Creative Commons Attribution (CC BY) license.³⁷