Enhanced Osteogenesis by Combining Exogenous BMPs with Hydroxyapatite/Aragonite Bone Grafts: In Vitro and In Vivo Studies

Synthetic biomaterials are widely used as bone graft substitutes, but their osteogenic capacity is limited as they lack osteogenic growth factors. This study aimed to enhance the osteogenesis of a novel hydroxyapatite/aragonite (HAA) biomaterial by incorporating decellularized bone matrix and bone morphogenetic protein (BMP)-2 and BMP-7 (BMP-2/7). Human umbilical mesenchymal stem cells (MSCs) were able to proliferate and differentiate on HAA. HEK-293T cells exogenously expressing BMP-2/7 successfully secreted BMP-2/7, which was assessed by enzyme-linked immunosorbent assay. By establishing a co-culture of MSCs with HEK-293T cells expressing BMP-2/7, we successfully created an artificial allograft that integrates both synthetic biomaterials and functional organic components, offering the potential to enhance osteogenesis. The decellularized (by freeze/thawing) functional HAA was implanted between the tibia and anterior tibialis muscle in murine models and assessed the induced bone formation via micro-computer tomography, histology, and osteogenic markers mRNA expression by a reverse transcription-quantitative polymerase chain reaction. A significant increase in new bone formation was seen in the functional HAA implanted group. In conclusion, this study revealed that bone formation following the HAA implantation can be enhanced by a functional decellularized matrix, comprising BMP-2/7, via in vitro tissue engineering using MSCs and HEK-293T cells expressing BMP-2/7.