Mesenchymal stem cells and porous β-tricalcium phosphate composites prepared through stem cell screen-enrich-combine(-biomaterials) circulating system for the repair of critical size bone defects in goat tibia

Background: Efficacious bone substitute is essential for the treatment of a critical size bone defect. Currently, the bone substitutes commonly used in clinical practice lack osteogenic capacity and the therapeutic efficacy is not ideal. Herein, a novel stem cell screen-enrich-combine(-biomaterials) circulating system (SECCS) was introduced to provide the substitutes with osteogenic ability. The stem cell screening, enrichment, and recombination with substitutes could be integrated during the surgical operation. Using SECCS, the bioactive mesenchymal stem cells (MSCs) and porous P-tricalcium phosphate ((beta-TCP) composites (MSCs/beta-TCP) were rapidly prepared for critical size bone defect repair and validated in goat models of critical size tibia defects. Methods: Twelve goats with right hind limb tibia defects of 30 mm were randomly divided into two groups: six (the experimental group) were treated with MSCs/P-TCP prepared by SECCS and the other six goats (the control group) were treated with pure porous beta-TCP. The repair effect was assessed by x-ray, computed tomography (CT), micro-CT, histology and histomorphology 6 months after the operation. In addition, the enrichment efficacy of MSCs and the characteristics of the MSCs/beta-TCP prepared by SECCS were evaluated. Results: The SECCS could compound about 81.3 +/- 3.0% of the MSCs in bone marrow to the porous P-TCP without affecting the cell viability. The average number of MSCs for retransplantation was 27,655.0 +/- 5011.6 for each goat from the experimental group. In vitro, satisfactory biocompatibility of the MSCs/beta-TCP was performed, with the MSCs spreading adequately, proliferating actively, and retaining the osteogenic potential. In vivo, the defect repair by MSCs/beta-TCP with good medullary cavity recanalization and cortical remodeling was significantly superior to that of pure porous beta-TCP. Conclusions: The MSCs/beta-TCP prepared through SECCS demonstrated significant therapeutic efficacy in goat models of critical size bone defect. This provides a novel therapeutic strategy for critical size bone defects caused by severe injury, infection, and bone tumor resection with a high profile of safety, effectiveness, simplicity, and ease.