Osteoclastogenesis is negatively regulated by D-serine produced by osteoblasts

Takeshi Takarada, Mika Takarada-Iemata, Yoshifumi Takahata, Daisuke Yamada, Tomomi Yamamoto, Yukari Nakamura, Eiichi Hinoi, Yukio Yoneda

Research output: Contribution to journalArticle

9 Citations (Scopus)

Abstract

We have shown the functional expression by chondrocytes of serine racemase (SR) which is responsible for the synthesis of D-serine (Ser) from L-Ser in cartilage. In this study, we evaluated the possible functional expression of SR by bone-forming osteoblasts and bone-resorbing osteoclasts. Expression of SR mRNA was seen in osteoblasts localized at the cancellous bone surface in neonatal rat tibial sections and in cultured rat calvarial osteoblasts endowed to release D-Ser into extracellular medium, but not in cultured osteoclasts differentiated from murine bone marrow progenitor cells. Sustained exposure to D-Ser failed to significantly affect alkaline phosphatase activity and Ca 2+ accumulation in cultured osteoblasts, but significantly inhibited differentiation and maturation in a concentration-dependent manner at a concentration range of 0.1-1mM without affecting cellular survival in cultured osteoclasts. By contrast, L-Ser promoted osteoclastic differentiation in a manner sensitive to the inhibition by D-Ser. Matured osteoclasts expressed mRNA for the amino acid transporter B 0,+ (ATB 0,+) and the system alanine, serine, and cysteine amino acid transporter-2 (ASCT2), which are individually capable of similarly incorporating extracellular L- and D-Ser. Knockdown of these transporters by siRNA prevented both the promotion by L-Ser and the inhibition by D-Ser of osteoclastic differentiation in pre-osteoclastic RAW264.7 cells. These results suggest that D-Ser may play a pivotal role in osteoclastogenesis through a mechanism related to the incorporation mediated by both ATB 0,+ and ASCT2 of serine enantiomers in osteoclasts after the synthesis and subsequent release from adjacent osteoblasts. J. Cell. Physiol. 227: 3477-3487, 2012. © 2012 Wiley Periodicals, Inc.

Original languageEnglish
Pages (from-to)3477-3487
Number of pages11
JournalJournal of cellular physiology
Volume227
Issue number10
DOIs
Publication statusPublished - Oct 2012

ASJC Scopus subject areas

  • Physiology
  • Clinical Biochemistry
  • Cell Biology

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