Low temperature 3D printing of tissue cartilage engineered with gelatin methacrylamide.

: Low concentration Gelatin methacryloyl (GelMA) hydrogels have been found to be promising cell-laden bioinks with excellent cell viability. Herein, we report a strategy that accurately deposits cell-containing bioinks at 5％ (w/v) GelMA using extrusion 3D bioprinting technology by utilizing its photo-crosslinkable and thermosensitive properties without the need for any sacrificial materials. During the 3D printing process, regular, smooth microfibers were formed without any discontinuity of extrusion or clogging, and photo-crosslinking was then used to stabilize the printed GelMA structure. After printing, the scaffolds were cultured in a chondrogenic medium to evaluate their significant roles in directing the behaviors of bone mesenchymal stem cells (BMSCs). Evidence of chondrogenic differentiation was demonstrated by Alcian blue staining and immunofluorescence (Col2a1) as well as the expression of chondrogenic genes. Finally, after platelet-rich plasma (PRP) treatment, the in vivo effects of the BMSCs on cartilage regeneration on the thigh muscles of female nude mice were measured using immunohistochemical techniques. The results showed that with this strategy, GelMA bioink displays excellent printability and a high cell survival rate. In vitro and in vivo, the cell-laden scaffold successfully regenerated mature cartilage via a cartilage-specific extracellular matrix, which seems to be suitable for cartilage regeneration and repair.