In Vitro Free Implantation of Stem Cells from Apical Papilla Using Injectable Hydrogel-Laden 3D-Printed Scaffold to Enhance Tissue Organization and Vascular Infiltration In Vivo

In emergency situations involving the loss of hard tissues, immediate treatment is crucial. While 3D-printed scaffolds offer structural support for damaged tissue, the processes of tissue integration and blood vessel formation remain challenging. To address these issues, stem cell therapies show promise; however, current treatments lack efficacy in urgent situations due to limited transplantation methods available for the defect. In this study, a 3D-printed poly(methyl methacrylate) (PMMA) scaffold loaded with high-density stem cells from the apical papilla (SCAP) using an injectable hydrogel composed of carboxymethyl chitosan (CMCTS) and oxidized hyaluronic acid (oHA) is developed. The SCAPs are directly incorporated in CMCTS/oHA hydrogel through self-crosslinking and subsequently injected in the 3D-printed PMMA scaffold. The hydrogel-laden scaffold exhibits excellent mechanical properties. In vitro analysis shows that the hydrogel is fully degraded, leading to the formation of 3D tissue both within and outside the scaffold. When implanted in mice without prior in vitro culture, the transplants are fully fused after 3 weeks, achieving strong tissue integration. In addition, mature blood vessels are histologically confirmed. Therefore, this research has potential applications in musculoskeletal tissue engineering, where immediate treatment is required, making these results suitable for volumetric tissue regeneration through stem cell transplantation.