Secreted tartrate-resistant acid phosphatase 5b is a Marker of osteoclast number in human osteoclast cultures and the rat ovariectomy model

Calcif Tissue Int. 2008 Feb;82(2):108-15. doi: 10.1007/s00223-007-9091-4. Epub 2007 Dec 15.

Abstract

Purpose: To study the effects of estrogen withdrawal on osteoclast number and osteoclast activity in the rat ovariectomy (OVX) model.

Methods: We first cultured human CD34+ osteoclast precursor cells on bovine bone slices, allowing them to differentiate into mature resorbing osteoclasts. Secreted tartrate-resistant acid phosphatase 5b (TRACP 5b) and C-terminal cross-linked telopeptides of type I collagen (CTX) were determined from the culture medium. TRACP 5b correlated strongly with osteoclast number and CTX with osteoclast activity, facilitating their subsequent use in the rat OVX model. An 8 week OVX study was then performed including sham-operated rats receiving vehicle, OVX rats receiving vehicle, and OVX rats receiving 10 microg/kg/day 17 beta-estradiol (E2). Trabecular bone parameters were determined from the tibial metaphysis using peripheral quantitative computed tomography and histomorphometry. Osteoclast number was normalized with bone perimeter (N.Oc/B.Pm) and tissue area (N.Oc/T.Ar, indicating absolute number of osteoclasts). TRACP 5b and CTX were determined from fasting serum samples.

Results: Trabecular bone parameters indicated substantial bone loss after OVX that was prevented by E2. N.Oc/B.Pm increased after OVX, while N.Oc/T.Ar and TRACP 5b decreased, and TRACP 5b correlated strongly with N.Oc/T.Ar. However, CTX values increased after OVX, and the "resorption index" CTX/TRACP 5b showed more substantial changes than either CTX or TRACP 5b alone.

Conclusion: These results show that TRACP 5b is a reliable marker of osteoclast number, and the index CTX/TRACP 5b is a useful parameter in rat OVX model. The high elevation of CTX/TRACP 5b values by OVX demonstrates that estrogen withdrawal generates high activity of osteoclasts in the rat OVX model.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acid Phosphatase / blood*
  • Animals
  • Biomarkers / blood*
  • Bone Resorption*
  • Cattle
  • Cell Count
  • Cells, Cultured
  • Disease Models, Animal
  • Estradiol / pharmacology
  • Female
  • Humans
  • Isoenzymes / blood*
  • Osteoclasts / cytology*
  • Osteoclasts / drug effects
  • Osteoclasts / metabolism*
  • Ovariectomy*
  • Rats
  • Rats, Sprague-Dawley
  • Tartrate-Resistant Acid Phosphatase

Substances

  • Biomarkers
  • Isoenzymes
  • Estradiol
  • ACP5 protein, human
  • Acid Phosphatase
  • Tartrate-Resistant Acid Phosphatase