VDR-mediated inhibition of DKK1 and SFRP2 suppresses adipogenic differentiation of murine bone marrow stromal cells

✍ Scribed by Luisella Cianferotti; Marie B. Demay

• Book ID: 102300030
• Publisher: John Wiley and Sons
• Year: 2007
• Tongue: English
• Weight: 205 KB
• Volume: 101
• Category: Article
• ISSN: 0730-2312
• DOI: 10.1002/jcb.21151

✦ Synopsis

Abstract

Osteoblasts and adipocytes are thought to derive from a common bone marrow stromal cell (BMSC) precursor. Activation of the canonical Wnt signaling pathway plays a pivotal role in the differentiation of BMSCs along either of these two lineages, promoting osteogenesis and inhibiting adipogenesis. Liganded nuclear receptors, including the vitamin D receptor (VDR) and peroxisomal proliferator‐activated receptor γ (PPARγ), can also affect BMSCs differentiation. To address whether VDR ablation modulates the differentiation of BMSCs into the osteoblast or adipogenic lineages, BMSCs were isolated from VDR null mice and from their wild‐type littermates. VDR ablation did not alter osteoblastic differentiation. However, when cultured under adipogenic conditions, BMSCs from the VDR null mice expressed higher mRNA levels of PPARγ and of markers of adipogenic differentiation. An increase in the size and number of mature adipocyte foci was also observed in cultures isolated from VDR null mice relative to those isolated from wild‐type mice. To address whether the increased adipogenesis observed in the VDR null cultures was associated with inhibition of the canonical Wnt signaling pathway, mRNA levels for DKK1 and SFRP2 were examined. Cultures from the VDR null mice expressed higher levels of mRNA encoding DKK1 and SFRP2 than did the wild‐type cultures. This difference is, at least in part, due to ligand‐dependent actions of the VDR, since 1,25‐dihydroxyvitamin D~3~ suppressed DKK1 and SFRP2 expression in wild‐type cultures. Thus, the VDR inhibits adipogenesis of BMSCs at least in part by suppressing the expression of inhibitors of the canonical Wnt signaling pathway. J. Cell. Biochem. 101: 80–88, 2007. © 2007 Wiley‐Liss, Inc.