Timing of geranylgeraniol addition increases osteoblast activities under alendronate condition

Alendronate (ALN), a nitrogen-containing bisphosphonate, is prescribed to treat bone diseases. ALN acts as an inhibitor of enzymes in the mevalonate pathway, which results in reducing osteoblast viability and mineralization. Geranylgeraniol (GGOH) is a substrate in mevalonate pathway and mediates protein prenylation in the cells.

To investigate the effects of GGOH on ALN-treated osteoblast activities in order to improve the application of GGOH.

MC3T3 cells were treated with ALN. GGOH were added at different time points. Cell activities were examined using alizarin red S, MTT assay, alkaline phosphatase (ALP) activity, and quantitative polymerase chain reaction.

ALN decreased mineralization. In the presence of ALN, GGOH addition at the first week of culture increased mineralization compared with the addition at other time points. ALN treatment for 7 days caused a reduction in osteoblast and pre-osteoblast viability compared with untreated cells. GGOH supplement partially rescued cell viability and increased total protein in cells treated with ALN. Furthermore, GGOH significantly upregulated gene expressions of Col I, OPN, VEGF, and VEGFR2.

GGOH could be best applied at the early stage of osteogenesis since GGOH helped increasing cell viability and differentiation at the first 7 day of treatment.