Effect of MK-4 treatment on 2-D cultured hOBs. hOBs were cultured in osteogenic medium (OM) combined or not with MK-4 at 10 μM (OM + MK-4) for 14 days. Mineral matrix deposition was evaluated by ARS and results are expressed as (a) the median and 1st and 3rd quartile of at least three independent experiments (n = 10). (b,c) Expression of typical osteoblast markers (ALP, Runx2, OC, OPN, and COL1a1) analyzed both at the mRNA and protein level, by RT-qPCR and flow cytometry, respectively. Data are presented as mean ± standard deviation (SD) of at least three independent experiments (n = 5). (* p < 0.05 vs. OM).