Dextrin hydrogel loaded with a macroporous Bonelike® scaffold and dental pulp stem cells for critical-sized defect repair

Regeneration of severe bone defects remains a challenge. A formulation of synthetic glass-reinforced hydroxyapatite bone substitute, Bonelike® Poro (BL®P), 250–500 µm-diameter, with a dextrin-based hydrogel (HG), further loaded with human dental pulp stem cells (hDPSCs) with osteogenic differentiation ability, was tested for the management of critical-sized defects in an ovine model. Morphology, calcium release, and mechanical strength of HG + BL®P were analyzed. Then, BL®P, HG + BL®P, and 106 hDPSCs-loaded HG + BL®P were implanted in ovine critical-sized 14 mm-diameter calvaria defects. Bone samples were collected after 3 and 6 weeks for histological and micro-CT analysis. BL®P exhibits a suitable porous size for cell ingrowth, from the nm (>200 nm) to the µm (5 µm) range. The addition of BL®P granules to the HG resulted in increased compressive elastic modulus and ultimate tensile strength. The mildly acidic nature of the HG contributed to a faster dissolution of granules. In vivo results confirmed the HG suitability as a carrier, providing better defect filling, easy handling, and injectability of BL®P without compromising new bone formation nor biocompatibility. The HG + BL®P formulations can successfully regenerate critical-sized defects; however, addition of hDPSCs did not significantly enhance new bone formation under these conditions. Granular BL®P provides an effective alternative to autologous grafts. The HG acts as a biocompatible carrier of granular bone substitutes and cells, conferring injectability and cohesivity.