Injectable calcium phosphate–alginate–chitosan microencapsulated MC3T3-E1 cell paste for bone tissue engineering in vivo

• MC3T3-E1 cells were delivered into CPC paste by alginate–chitosan microcapsules.
• Implanted MC3T3-E1 cells were traced and survived for at least 2 weeks in vivo.
• The new construct shows better bone formation potential than that without chitosan.
• Alginate–chitosan microcapsule is better than alginate one for seeding cells in CPC.

Osteoblasts or stem cells have been delivered into injectable calcium phosphate cement (CPC) to improve its effectiveness and biological function. However, the osteogenic potential of the new construct in vivo has been rarely reported, and there are no reports on alginate–chitosan microencapsulated osteoblasts mixed with CPC. This study aimed to develop alginate–chitosan microencapsulated mouse osteoblast MC3T3-E1 cells (AC-cells), evaluate the osteogenic potential of a calcium phosphate cement complex with these AC-cells (CPC-AC-cell), and trace the implanted MC3T3-E1 cells in vivo. MC3T3-E1 cells were embedded in alginate microcapsules, cultured in osteogenic medium for 7 days, and then covered with chitosan before mixing with a paste of β-tricalcium phosphate/calcium phosphate cement (β-TCP/CPC). The construct was injected into the dorsal subcutaneous area of nude mice. Lamellar-bone-like mineralization, newly formed collagen and angiogenesis were observed at 4 weeks. At 8 weeks, areas of newly formed collagen expanded; further absorption of β-TCP/CPC and osteoid-like structures could be seen. Cell tracing in vivo showed that implanted MC3T3-E1 cells were clearly visible at 2 weeks. These in vivo results indicate that the novel injectable CPC-AC-cell construct is promising for bone tissue engineering applications.