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Exp Hematol. 2003 Nov;31(11):1081-8.

Expression of osteoprotegerin mRNA and protein in murine megakaryocytes.

Author information

  • 1INSERM U362, IFR 54, Institut Gustave Roussy, Villejuif, France.

Abstract

OBJECTIVE:

Osteoprotegerin (OPG) is a soluble member of the tumor necrosis factor receptor superfamily critically involved in the regulation of bone resorption. Within the bone microenvironment, OPG is abundantly produced by osteoblast/stromal cells, and its expression is regulated by transforming growth factor-beta(1) (TGF-beta(1)). However, OPG expression and regulation in primary hematopoietic cells have not been fully investigated.

MATERIALS AND METHODS:

Opg mRNA was studied in murine hematopoietic cells by semiquantitative reverse transcriptase-polymerase chain reaction. The OPG protein was identified by immunofluorescence labeling and secretion was assessed by enzyme-linked immunosorbent assay.

RESULTS:

Opg transcripts were detected in platelets, megakaryocytes (MK), monocytes, and B lymphocytes, but not in erythroblasts, neutrophils, and T lymphocytes. Mature MK and proplatelets exhibited strong immunostaining for OPG outside the storage alpha-granules, and secretion was detected in the conditioned medium. To analyze whether opg transcription in MK was influenced by TGF-beta(1), the opg/GpIIb mRNA ratio was compared in cultured MK derived from TGF-beta(1) null mutants and wild-type littermates without or after the addition of bioactive TGF-beta(1). No difference was seen, indicating that opg expression in MK was not modulated by TGF-beta(1). However, mRNA levels were increased when thrombopoietin was present in the culture medium, suggesting that MK maturation was correlated with enhanced opg expression.

CONCLUSIONS:

With these results we document for the first time that murine MK and platelets express OPG. This suggests a novel role for MK in bone homeostasis, in addition to its role in vascular homeostasis.

PMID:
14585373
[PubMed - indexed for MEDLINE]
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