01973nas a2200361   4500000000100000000000100001008004100002260001200043653002700055653002600082100001400108700001800122700001600140700002100156700001700177700002200194700001500216700002200231700002900253700001400282700002400296700001700320700002200337700001800359700002200377700002100399245008700420856005500507300001400562490000700576520101400583022001401597       2023                            d  c2023-0810aBiomaterials – cells10aCardiovascular models1 aSuji Choi1 aKeel Yong Lee1 aSean L. Kim1 aLuke A. MacQueen1 aHuibin Chang1 aJohn F. Zimmerman1 aQianru Jin1 aMichael M. Peters1 aHerdeline Ann M. Ardoña1 aXujie Liu1 aAnn-Caroline Heiler1 aRudy Gabardi1 aCollin Richardson1 aWilliam T. Pu1 aAndreas R. Bausch1 aKevin Kit Parker00aFibre-infused gel scaffolds guide cardiomyocyte alignment in 3D-printed ventricles  uhttps://www.nature.com/articles/s41563-023-01611-3  a1039-10460 v223 aHydrogels are attractive materials for tissue engineering, but efforts to date have shown limited ability to produce the microstructural features necessary to promote cellular self-organization into hierarchical three-dimensional (3D) organ models. Here we develop a hydrogel ink containing prefabricated gelatin fibres to print 3D organ-level scaffolds that recapitulate the intra- and intercellular organization of the heart. The addition of prefabricated gelatin fibres to hydrogels enables the tailoring of the ink rheology, allowing for a controlled sol–gel transition to achieve precise printing of free-standing 3D structures without additional supporting materials. Shear-induced alignment of fibres during ink extrusion provides microscale geometric cues that promote the self-organization of cultured human cardiomyocytes into anisotropic muscular tissues in vitro. The resulting 3D-printed ventricle in vitro model exhibited biomimetic anisotropic electrophysiological and contractile properties.  a1476-4660