INTRODUCTION: Few studies have tried to discriminate a differential behavior between osteoarthritic (OA) osteoblasts (Obs). Based on osteocalcin level, we aimed, in the present study, to evaluate the capacity of OA Obs for producing molecules of the Wnt/beta-catenin signaling pathway. METHODS: Human primary OA Obs (n = 11) were exposed or not to 50 nM of 1,25 dihydroxyvitamin D-3 (VitD(3)) for 24 h. Osteocalcin (OCN), TGF-beta 1, Dickkopf-related protein 2 (DKK2), R-spondin 2 (Rspo2), Wnt5b, and low density lipoprotein related-receptor 1 (LRP1) were evaluated by real time RT-PCR. RESULTS: All samples responded to VitD(3) as validated by the increase in OCN expression. However two populations of Obs were discriminated; one called ``high responders'' whose OCN stimulation was higher than 100 fold (mean 881 fold, p < 0.01, n = 5) and the second one whose stimulation was inferior to 100 fold (mean 47 fold, p < 0.01, n = 6), namely ``low responders''. In fact, high responders have a weaker basal expression of OCN. With regards to these two cell populations and in absence of VitD(3) challenge, the expression level of TGF-beta 1 (15 fold, p < 0.001), DKK2 (2.5 fold, p < 0.002) and Wnt5b (5.5 fold, p < 0.003) was higher in ``high responders'', meanwhile Rspo2 and LRP1 expression was unchanged. VitD(3) exacerbated this pattern but corrected OCN expression and favored Wnt agonist expression. CONCLUSION: We identified 2 populations of OA Obs according to the OCN expression under the control of VitD(3). In addition under basal conditions, these 2 populations expressed differently TGF-beta 1, Wnt5b, DKK2, suggesting a heterogeneous differentiation and phenotype in Obs among OA patients.