Abstract
Osteoblasts and adipocytes are derived from common mesenchymal progenitor cells. The bone loss of osteoporosis is associated with altered progenitor differentiation from an osteoblastic to an adipocytic lineage. cDNA microarrays and quantitative real-time PCR (Q-PCR) were carried out in a differentiating mouse stromal osteoblastic cell line, Kusa 4b10, to identify gene targets of factors that stimulate osteoblast differentiation including parathyroid hormone (PTH) and gp130-binding cytokines, oncostatin M (OSM) and cardiotrophin-1 (CT-1). Zinc finger protein 467 (Zfp467) was rapidly down-regulated by PTH, OSM, and CT-1. Retroviral overexpression and RNA interference for Zfp467 in mouse stromal cells showed that this factor stimulated adipocyte formation and inhibited osteoblast commitment compared with controls. Regulation of adipocyte markers, including peroxisome proliferator-activated receptor (PPAR) γ, C/EBPα, adiponectin, and resistin, and late osteoblast/osteocyte markers (osteocalcin and sclerostin) by Zfp467 was confirmed by Q-PCR. Intra-tibial injection of calvarial cells transduced with retroviral Zfp467 doubled the number of marrow adipocytes in C57Bl/6 mice compared with vector control-transduced cells, providing in vivo confirmation of a pro-adipogenic role of Zfp467. Furthermore, Zfp467 transactivated a PPAR-response element reporter construct and recruited a histone deacetylase complex. Thus Zfp467 is a novel co-factor that promotes adipocyte differentiation and suppresses osteoblast differentiation. This has relevance to therapeutic interventions in osteoporosis, including PTH-based therapies currently available, and may be of relevance for the use of adipose-derived stem cells for tissue engineering.
Highlights
Senior Research Fellowship. 3 To whom correspondence should be addressed: St
Suppression of Zinc finger protein 467 (Zfp467) mRNA by parathyroid hormone (PTH) and gp130 Cytokines—Microarray analysis revealed that Zfp467 mRNA was down-regulated 1.5-fold by 10 nM PTH[1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34] at 1 and 6 h
Validation experiments using quantitative real-time PCR (Q-PCR) in differentiated Kusa 4b10 cells and calvarial osteoblasts confirmed that PTH[1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34] suppressed Zfp467 mRNA levels at 1 h and levels returned to basal by 6 h (Fig. 1, A and B); this occurred in a dose-dependent manner with a maximal effect at 10 ng/ml
Summary
Senior Research Fellowship. 3 To whom correspondence should be addressed: St. Vincent’s Institute of MSC lineage commitment is dependent on the expression of key transcription factors that, on induction, initiate a cascade of events culminating in cellular differentiation and development. Overexpression of sense Zfp467 suppressed expression of intermediate and late markers of osteoblast differentiation including PTH receptor-1, osteocalcin, and sclerostin compared with vector-infected control cells (Fig. 2B).
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