Vascular tissues bioprinted with smooth muscle cell-only bioinks in support baths mimic features of native coronary arteries.

This study explores the bioprinting of a smooth muscle cell-only bioink into ionically crosslinked oxidized methacrylated alginate (OMA) microgel baths to create self-supporting vascular tissues. The impact of OMA microgel support bath methacrylation degree and cell-only bioink dispensing parameters on tissue formation, remodeling, structure and strength was investigated. We hypothesized that reducing dispensing tip diameter from 27G (210 µm) to 30G (159 µm) for cell-only bioink dispensing would reduce tissue wall thickness and improve the consistency of tissue dimensions while maintaining cell viability. Printing with 30G tips resulted in decreased mean wall thickness (318.6 µm) without compromising mean cell viability (94.8%). Histological analysis of cell-only smooth muscle tissues cultured for 14 days in OMA support baths exhibited decreased wall thickness using 30G dispensing tips, which correlated with increased collagen deposition and alignment. In addition, a TUNEL assay indicated a decrease in cell death in tissues printed with thinner (30G) dispensing tips. Mechanical testing demonstrated that tissues printed with a 30G dispensing tip exhibit an increase in ultimate tensile strength compared to those printed with a 27G dispensing tip. Overall, these findings highlight the importance of precise control over bioprinting parameters to generate mechanically robust tissues when using cell-only bioinks dispensed and cultured within hydrogel support baths. The ability to control print dimensions using cell-only bioinks may enable bioprinting of more complex soft tissue geometries to generate in vitro tissue models.