Gene expression profiling of glucocorticoid-inhibited osteoblasts.
Glucocorticoid (GC) treatment for the management of autoimmune and inflammatory diseases is associated with decreased bone formation and increased risk for fracture. In MC3T3-E1 cell cultures, 0.1-1 microM dexamethasone (DEX) arrests development of the osteoblast phenotype when administration commences at a commitment stage around the time of confluency. To gain new insights into GC-induced osteoporosis, we performed microarray-based gene expression analysis of GC-arrested MC3T3-E1 cultures, 2.5 days after the administration of DEX. Of the >12 000 transcripts interrogated, 74 were up-regulated and 17 were down-regulated by at least 2.5-fold (P < or = 0.05). Some of these genes, such as Mmp13, Serum/GC-regulated kinase and Tieg, have previously been reported as GC-responsive. Others are shown here for the first time to respond to GCs. DEX strongly repressed Krox20/Egr2 at both the mRNA and the protein level. This is especially significant because mice lacking this transcription factor develop osteoporosis. The data also suggest that the bone morphogenetic protein (BMP) pathway, which is involved in regulating bone mass, and other pathways that influence BMP signaling, are abrogated by GCs: (i) DEX increased the mRNA levels of the BMP antagonists Follistatin and Dan; (ii) DEX increased the levels of p21 Rasgap3 and Ptpn16/MKP-1 mRNAs, negative regulators of the MAP kinase pathway; and (iii) DEX decreased Cox mRNA levels. DEX also increased thrombospondin mRNA levels, which negatively regulate bone mass in vivo, as well as the adipocytic marker Fkbp51. These and other observations disclose novel gene targets, whose regulation by GCs in osteoblasts may shed light on and provide new therapeutic approaches to osteoporosis.
Department of Biochemistry and Molecular Biology, Institute for Genetic Medicine, Keck School of Medicine at the University of Southern California, 2250 Alcazar Street, Los Angeles, California 90033, USA.
Nathalie
N
Leclerc
Cynthia A
CA
Luppen
Vincent V
VV
Ho
Shailender
S
Nagpal
Joseph G
JG
Hacia
Elisheva
E
Smith
Baruch
B
Frenkel
D016475:3T3 Cells; D000818:Animals; D001483:Base Sequence; D015153:Blotting, Western; D017931:DNA Primers; D003907:Dexamethasone / Q000494:pharmacology*; D020869:Gene Expression Profiling; D051379:Mice; D020411:Oligonucleotide Array Sequence Analysis; D010006:Osteoblasts / Q000187:drug effects* / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000235:genetics
D017931:DNA Primers; D003907:Dexamethasone