Calcium phosphate combination biomaterials as human mesenchymal stem cell delivery vehicles for bone repair

A new class of biomimetic, bioresorbable apatitic calcium phosphate cement (CPC) biomaterial was recently developed. The handling characteristics and the ability to harden at body temperature in the presence of physiological saline makes it an attractive clinical bone substitute and delivery vehicle for therapeutic agents in orthopaedic applications. The major challenge with the material system consists in formulating an injectable paste with options for cell delivery in order to regenerate new bone faster with high quality. In this study, three different additives and/or viscosity modifiers (carboxymethylcellulose, silk and alginate) were incorporated into the CPC matrix. Injectability, cell viability and cell proliferation were evaluated by SEM, chemical content, and gene expression for osteogenesis of hMSCs. Injectable composites of CPC-gels for cell protection were achieved. The alginate provided the best outcomes, based on cell proliferation, ALP and collagen production, and osteogenic transcript increases for ALP, type I collagen, BSP and OP. Osteogenic analysis indicated lineage-specific differentiation of hMSCs into osteogenic outcomes in this CPC matrix. The results suggest that gel mixed CPC combination materials can be used as a cell delivery vehicle for bone regeneration.