Pro-resorptive activity of human osteoarthritis subchondral bone osteoblasts. Resorption activity of osteoblasts co-incubated with differentiated peripheral blood mononuclear cells in the presence of macrophage colony-stimulating factor and in the absence or presence of chondroitin sulfate (CS) (200 μg/mL), glucosamine sulfate (GS) (200 μg/mL), or both (200 μg/mL each) in the absence or presence of vitamin D3 at 50 nM. Data are in the absence or presence of vitamin D3 from nine or five independent experiments, respectively. They are expressed as the mean resorbed surface per total surface upon treatment with the factors. Statistical significance was assessed by paired Student t test versus autologous control. Underlined p value indicates the statistical difference between control (C, basal conditions) and vitamin D3-treated specimens.