Differential osteogenicity of multiple donor-derived human mesenchymal stem cells and osteoblasts in monolayer, scaffold-based 3D culture and in vivo.

We set out to compare the osteogenicity of human mesenchymal stem (hMSCs) and osteoblasts (hOBs). Upon osteogenic induction in monolayer, hMSCs showed superior matrix mineralization expressing characteristic bone-related genes. For scaffold cultures, both cell types presented spindle-shaped, osteoblast-like morphologies forming a dense, interconnected network of high viability. On the scaffolds, hOBs proliferated faster. A general upregulation of parathyroid hormone-related protein (PTHrP), osteoprotegrin (OPG), receptor activator of NF-κB ligand (RANKL), sclerostin (SOST), and dentin matrix protein 1 (DMP1) was observed for both cell types. Simultaneously, PTHrP, RANKL and DMP-1 expression decreased under osteogenic stimulation, while OPG and SOST increased significantly. Following transplantation into NOD/SCID mice, µCT and histology showed increased bone deposition with hOBs. The bone was vascularized, and amounts further increased for both cell types after recombinant human bone morphogenic protein 7 (rhBMP-7) addition also stimulating osteoclastogenesis. Complete bone organogenesis was evidenced by the presence of osteocytes and hematopoietic precursors. Our study results support the asking to develop 3D cellular models closely mimicking the functions of living tissues suitable for in vivo translation.