3D bioprinting meniscus tissue onboard the International Space Station

This study demonstrated extrusion bioprinting of an anatomically relevant meniscus-shaped tissue construct in microgravity aboard the International Space Station (ISS) using the BioFabrication Facility (BFF). A collagen- and chondroitin sulfate-based bioink (collagen I/II + methacrylated components with LAP photoinitiator) was mixed with human bone marrow MSCs on-orbit and printed into a support bath strategy (Pluronic containment “bathtub” plus a sheared agarose SLAM support) to overcome wetting/surface-tension challenges in microgravity. Following printing and 405 nm UV curing, constructs were intended to be cultured in ADSEP for 2 weeks, but media exchange malfunction resulted in prolonged static exposure to the same medium and later cold storage prior to return. Despite logistical/culture limitations, the ISS-printed meniscus showed good shape fidelity with dimensions comparable to ground controls. However, mechanical testing revealed substantially reduced stiffness: unconfined compression-derived Young’s modulus was ~9.8 kPa for ISS prints versus ~38.7 kPa for ground BFF prints, likely influenced by lower construct mass/density and/or differences in ink extrusion/crosslinking and culture history. Histology (H&E) indicated broadly similar cell distribution between ISS and ground prints, supporting feasibility of large-scale musculoskeletal bioprinting in microgravity and highlighting key operational constraints for future in-orbit tissue manufacturing.