To apply human embryonic stem cells (hESCs) as a source of osteoblast-like cells (hESC-OS), factors influencing bone formation potential of hESC-OS need to be evaluated.

Aims: The study aimed to investigate effects of implantation sites and biomaterials on bone formation capacity of hESC-OS.

Materials and methods: Human ESC-OS were seeded on various biomaterials including porous collagen type I and polycarpolactone/ß-tricalcium phosphate scaffolds, gelatin sponges and ß-TCP particles. Samples were subcutaneously transplanted in immunodeficient mice for 6 weeks. Human ESC-OS on ß-TCP particles were transplanted in calvarial defects of immunodeficient rats for 6 weeks as a positive control. Bone formation and mineralization were investigated using soft radiograph, micro-computer tomography, polarized light microscope, histological analysis, von Kossa and immunohistochemical staining and qRT-PCR. Oligonucleotide microarry was applied to compare expression of genes related to osteogenesis of hESC-OS with osteoblast-like cells derived from human bone marrow stromal cells (hBMSC-OS).

Results: Human ESC-OS deposited bone on ß-TCP particles in rat calvarial defects. Only mineralization of bone matrixes on the scaffolds and expression of human osteoblast-related genes were detected in subcutaneous transplantation. In comparison to hBMSC-OS, microarray analysis demonstrated lower expression levels of genes related to osteogenesis and mineralization, such as MSX1, TGFBR1, BGLAP, IBSP, BMP4, BMP6 and wnt1 and higher levels of osteogenesis inhibitor, DKK3 of hESC-OS.

Conclusion: Bone formation capacity of hESC-OS is influenced by implantation sites. Human ESC-OS required osteogenic stimuli from local host cells to enhance their bone formation capacity. Local stimuli are essential to survival, growth and differentiation of transplanted hESC-OS.

Conflict of interest: None declared.