Co-culture bioprinting of tissue-engineered bone-periosteum biphasic complex for repairing critical-sized skull defects in rabbits

Tissue engineering based on bioprinting technology has broad prospects in the treatment of critical-sized bone defect. Nevertheless, it is challenging to construct composite tissues or organs with structural integrity. Periosteum and stem cells are important in bone regeneration, and it has been shown that co-culture engineering system could successfully repair bone defects. Here, a strategy of co-culture bioprinting was proposed, and a tissue-engineered bone-periosteum biphasic complex was designed. Poly-L-lactic acid/hydroxyapatite (PLLA/HA) was used to construct the supporting scaffold of bone phase. Gelatin methacryl (GelMA) loaded with rabbit bone mesenchymal stem cells (BMSCs) and periosteum-derived stem cells (PDSCs) were used to simulate the extracellular matrix and cellular components of bone and periosteum, respectively, and a co-culture layer was formed between the bone and the periosteum phase. By adjusting material ratios of PLLA/HA and crosslinking time of GelMA, a complex with good mechanical strength and cell activity was constructed and then implanted into the defect area of rabbit skull. The quantitative results of imaging and histology showed that the repair effect of bone-periosteum biphasic complex group was significantly better than that of other control groups, which demonstrated that the bone-periosteum biphasic complex was advantageous to both bone repair and regeneration. In general, using the co-culture bioprinting to construct engineered tissue is a very promising strategy, which is expected to be applied in the construction of more complex tissues and solid organs for tissue repair and organ transplantation.