Efficient wet-spinning of pre-aligned microtissues for 3D bioprinting complex tissue alignment.

Engineering functional smooth muscle tissues requires precise control of cellular alignment, particularly in complex anatomical regions such as the gastroesophageal junction (GEJ). We present a scalable wet-spinning approach for generating pre-aligned microtissues (PAMs) from immortalized human esophageal smooth muscle cells embedded in a collagen-alginate core-shell fiber. After maturation, fibers were sectioned into uniform PAMs with preserved alignment and high cell viability. Immunofluorescence and gene expression analyses confirmed the expression of key contractile markers. PAMs were incorporated into a gelatin-methacryloyl bioink and 3D bioprinted to demonstrate alignment along the extrusion path. This method does not require specialized culture platforms and enables efficient production of aligned microtissues for bioprinting. It offers a promising strategy for fabricating anisotropic tissues and may facilitate the reconstruction of complex muscle structures such as the GEJ.