Hypoxia and vitamin D differently contribute to leptin and dickkopf-related protein 2 production in human osteoarthritic subchondral bone osteoblasts

被引：21

作者：

Bouvard B. ^{[1
,2
]}

Abed E. ^{[3
]}

Yéléhé-Okouma M. ^{[1
]}

Bianchi A. ^{[1
]}

Mainard D. ^{[1
,4
]}

Netter P. ^{[1
,4
]}

Jouzeau J.-Y. ^{[1
,4
]}

Lajeunesse D. ^{[3
]}

Reboul P. ^{[1
]}

机构：

[1] UMR 7365 CNRS-Université de Lorraine, IMoPA, Biopôle de l'Université de Lorraine, Campus Biologie-Santé, 9 Avenue de la Forêt de Haye- CS 50184, Vandoeuvre lès Nancy, Cedex

[2] Service de Rhumatologie, Centre Hospitalier Universitaire, 4 rue Larrey, Angers cedex 9

[3] Unité de Recherche en Arthrose, Centre de Recherche de l'Université de Montréal (CR-CHUM), 900, rue Saint-Denis, Montréal, H2X 0A9, QC

[4] Centre Hospitalier Universitaire, 29 Avenue du Maréchal de Lattre de Tassigny, Nancy

来源：

Arthritis Research & Therapy | / 16卷 / 5期

关键词：

Vascular Endothelial Growth Factor; Subchondral Bone; Tibial Plateau; Subchondral Bone Plate; DKK2 Expression;

D O I：

10.1186/s13075-014-0459-3

中图分类号：

学科分类号：

摘要：

Introduction: Bone remodelling and increased subchondral densification are important in osteoarthritis (OA). Modifications of bone vascularization parameters, which lead to ischemic episodes associated with hypoxic conditions, have been suspected in OA. Among several factors potentially involved, leptin and dickkopf-related protein 2 (DKK2) are good candidates because they are upregulated in OA osteoblasts (Obs). Therefore, in the present study, we investigated the hypothesis that hypoxia may drive the expression of leptin and DKK2 in OA Obs. Methods: Obs from the sclerotic portion of OA tibial plateaus were cultured under either 20% or 2% oxygen tension in the presence or not of 50 nM 1,25-dihydroxyvitamin D3 (VitD3). The expression of leptin, osteocalcin, DKK2, hypoxia-inducible factor 1α (Hif-1α) and Hif-2α was measured by real-time polymerase chain reaction and leptin production was measured by enzyme-linked immunosorbent assay (ELISA). The expression of Hif-1α, Hif-2α, leptin and DKK2 was reduced using silencing RNAs (siRNAs). The signalling pathway of hypoxia-induced leptin was investigated by Western blot analysis and with mitogen-activated protein kinase (MAPK) inhibitors. Results: The expression of leptin and DKK2 in Obs was stimulated 7-fold and 1.8-fold, respectively (P < 0.05) under hypoxia. Interestingly, whereas VitD3 stimulated leptin and DKK2 expression 2- and 4.2-fold, respectively, under normoxia, it stimulated their expression by 28- and 6.2-fold, respectively, under hypoxia (P < 0.05). The hypoxiainduced leptin production was confirmed by ELISA, particularly in the presence of VitD3 (P < 0.02). Compared to Obs incubated in the presence of scramble siRNAs, siHif-2α inhibited VitD3-stimulated leptin mRNA and protein levels by 70% (P =0.004) and 60% (P < 0.02), respectively, whereas it failed to significantly alter the expression of DKK2. siHif- 1α has no effect on these genes. Immunoblot analysis showed that VitD3 greatly stabilized Hif-2α under hypoxic conditions. The increase in leptin expression under hypoxia was also regulated, by p38 MAPK (P < 0.03) and phosphoinositide 3-kinase (P < 0.05). We found that the expression of leptin and DKK2 were not related to each other under hypoxia. Conclusions: Hypoxic conditions via Hif-2 regulation trigger Obs to produce leptin, particularly under VitD3 stimulation, whereas DKK2 is regulated mainly by VitD3 rather than hypoxia. © 2014 Bouvard et al.

引用

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