Sclerostin regulates release of bone mineral by osteocytes by induction of carbonic anhydrase 2

Masakazu Kogawa, Asiri R. Wijenayaka, Renee T. Ormsby, Gethin P. Thomas, Paul H. Anderson, Lynda Bonewald, David M. Findlay, Gerald J. Atkins

Research output: Contribution to journalArticle

73 Citations (Scopus)

Abstract

The osteocyte product sclerostin is emerging as an important paracrine regulator of bone mass. It has recently been shown that osteocyte production of receptor activator of NF-κB ligand (RANKL) is important in osteoclastic bone resorption, and we reported that exogenous treatment of osteocytes with sclerostin can increase RANKL-mediated osteoclast activity. There is good evidence that osteocytes can themselves liberate mineral from bone in a process known as osteocytic osteolysis. In the current study, we investigated sclerostin-stimulated mineral dissolution by human primary osteocyte-like cells (hOCy) and mouse MLO-Y4 cells. We found that sclerostin upregulated osteocyte expression of carbonic anhydrase 2 (CA2/Car2), cathepsin K (CTSK/Ctsk), and tartrate-resistant acid phosphatase (ACP5/Acp5). Because acidification of the extracellular matrix is a critical step in the release of mineral from bone, we further examined the regulation by sclerostin of CA2. Sclerostin stimulated CA2 mRNA and protein expression in hOCy and in MLO-Y4 cells. Sclerostin induced a decrease in intracellular pH (pHi) in both cell types as well as a decrease in extracellular pH (pHo) and the release of calcium ions from mineralized substrate. These effects were reversed in the co-presence of the carbonic anhydrase inhibitor, acetozolamide. Car2-siRNA knockdown in MLO-Y4 cells significantly inhibited the ability of sclerostin to both reduce the pHo and release calcium from a mineralized substrate. Knockdown in MLO-Y4 cells of each of the putative sclerostin receptors, Lrp4, Lrp5 and Lrp6, using siRNA, inhibited the sclerostin induction of Car2, Catk and Acp5 mRNA, as well as pHo and calcium release. Consistent with this activity of sclerostin resulting in osteocytic osteolysis, human trabecular bone samples treated ex vivo with recombinant human sclerostin for 7 days exhibited an increased osteocyte lacunar area, an effect that was reversed by the co-addition of acetozolamide. These findings suggest a new role for sclerostin in the regulation of perilacunar mineral by osteocytes.

Original languageEnglish (US)
Pages (from-to)2436-2448
Number of pages13
JournalJournal of Bone and Mineral Research
Volume28
Issue number12
DOIs
StatePublished - Dec 2013
Externally publishedYes

Fingerprint

Osteocytes
Carbonic Anhydrases
Minerals
Bone and Bones
Osteolysis
Calcium
Small Interfering RNA
Cathepsin K
Carbonic Anhydrase Inhibitors
Messenger RNA
Osteoclasts
Bone Resorption
Extracellular Matrix
Ions
Ligands

Keywords

  • carbonic anhydrase 2
  • osteocyte
  • osteocytic osteolysis
  • Sclerostin
  • sost

ASJC Scopus subject areas

  • Orthopedics and Sports Medicine
  • Endocrinology, Diabetes and Metabolism

Cite this

Kogawa, M., Wijenayaka, A. R., Ormsby, R. T., Thomas, G. P., Anderson, P. H., Bonewald, L., ... Atkins, G. J. (2013). Sclerostin regulates release of bone mineral by osteocytes by induction of carbonic anhydrase 2. Journal of Bone and Mineral Research, 28(12), 2436-2448. https://doi.org/10.1002/jbmr.2003

Sclerostin regulates release of bone mineral by osteocytes by induction of carbonic anhydrase 2. / Kogawa, Masakazu; Wijenayaka, Asiri R.; Ormsby, Renee T.; Thomas, Gethin P.; Anderson, Paul H.; Bonewald, Lynda; Findlay, David M.; Atkins, Gerald J.

In: Journal of Bone and Mineral Research, Vol. 28, No. 12, 12.2013, p. 2436-2448.

Research output: Contribution to journalArticle

Kogawa, M, Wijenayaka, AR, Ormsby, RT, Thomas, GP, Anderson, PH, Bonewald, L, Findlay, DM & Atkins, GJ 2013, 'Sclerostin regulates release of bone mineral by osteocytes by induction of carbonic anhydrase 2', Journal of Bone and Mineral Research, vol. 28, no. 12, pp. 2436-2448. https://doi.org/10.1002/jbmr.2003
Kogawa, Masakazu ; Wijenayaka, Asiri R. ; Ormsby, Renee T. ; Thomas, Gethin P. ; Anderson, Paul H. ; Bonewald, Lynda ; Findlay, David M. ; Atkins, Gerald J. / Sclerostin regulates release of bone mineral by osteocytes by induction of carbonic anhydrase 2. In: Journal of Bone and Mineral Research. 2013 ; Vol. 28, No. 12. pp. 2436-2448.
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