Identification of two populations of osteoarthritic osteoblasts according to the 1,25[OH]2 vitamin D3 potency to stimulate osteocalcin

Abstract

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/β-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-β1, 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-β1 (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-β1, Wnt5b, DKK2, suggesting a heterogeneous differentiation and phenotype in Obs among OA patients.

Orexins Facilitates Osteogenic Differentiation of MC3T3‐E1 Cells

“…Biological factors such as cytokines, hormones, and neuropeptides have been reported to regulate osteoblast differentiation and mineralization by activating osteoblastogenic factors, including runt‐related transcription factor 2 (Runx‐2) and osterix (Osx) . Increased activity of alkaline phosphatase (ALP), secretion of extracellular matrix proteins such as type I collagen, and elevated expression of various non‐collagenous proteins, such as osteocalcin (OCN), osteonectin, and osteopontin, are also key events during osteoblast maturation .…”

The collective influence of 1, 25-dihydroxyvitamin D3with physiological fluid shear stress on osteoblasts

“…3). Therefore, one conclusion could be made that 1, 25 (OH) 2 Furthermore, cell proliferation and differentiation as a long-term response of ROBs was further investigated to evaluate the synergistic effect of 1, 25 (OH) 2 D 3 and FSS by using PI, ALP activity, gene expressions of OPN and OCN. We found the same phenomenon that 1, 25 (OH) 2 D 3 inhibits osteoblast proliferation consistent with the report of K. Van der Meijden [5] .…”

“…5). From the perspective of cell differentiation, 1nmol/L 1, 25 (OH)2 D 3 has little effect on ALP activity, OPN and OCN gene expressions, but the addition of FSS appear a remarkable increase for these parameters. This phenomenon illustrates that low concentration of 1, 25 (OH) 2 D 3 , such as 1nmol/L, could not promote cell differentiation.…”

“…1, 25-dihydroxyvitamin D 3 (1,25 (OH) 2 applied widely. What's more, 1, 25-dihydroxyvitamin D 3 is one of the most widely applied vitamin D active metabolite and plays an significant role in the regulation of calcium and phosphate metabolism, also can obviously affect the proliferation, differentiation of osteoblasts [1][2][3] .…”

“…1, 25-dihydroxyvitamin D 3 (1,25 (OH) 2 applied widely. What's more, 1, 25-dihydroxyvitamin D 3 is one of the most widely applied vitamin D active metabolite and plays an significant role in the regulation of calcium and phosphate metabolism, also can obviously affect the proliferation, differentiation of osteoblasts [1][2][3] . The researchers found that 1, 25 (OH) 2 D 3 inhibits cell growth and enhances osteoblast differentiation by regulating the expression of collagenous and non-collagenous proteins, including osteocalcin and osteopontin [4,5] .…”