The Surface Antigen CD45R Identifies a Population of Estrogen-Regulated Murine Marrow Cells That Contain Osteoclast Precursors

Bone. 2003 Jun;32(6):581-90. doi: 10.1016/s8756-3282(03)00097-8.


We examined the osteoclastogenic potential of murine bone marrow cells that were fractionated according to their expression of the surface antigen CD45R. Osteoclast-like cells (OCL) with many authentic osteoclast characteristics readily formed in purified CD45R(+) murine bone marrow cell cultures after treatment with receptor activator of nuclear factor kappaB ligand (RANKL) and M-CSF. Ovariectomy (Ovx) caused a 1.5- to 2-fold increase in OCL number in unfractionated and CD45R(+) murine bone marrow cell cultures without affecting OCL formation in CD45R(-) marrow cells. Limiting dilution assays confirmed that Ovx caused an increase in osteoclast precursor cell number in CD45R(+) but not CD45R(-) cells. Mice deficient in the type 1 IL-1 receptor (IL-1R1 KO) do not lose bone mass after Ovx. We found that unfractionated, CD45R(+), and CD45R(-) bone marrow cells from IL-1R1 KO mice showed no increase in OCL formation in vitro after Ovx. In both the wild-type (WT) and the IL-1R1 KO mice Ovx was associated with a 2-fold increase in pre-B-lymphocytes. About 1.3-3.5% of murine marrow cells expressed surface RANK (the receptor for RANKL) while about 11.9-15% of murine bone marrow cells expressed c-Fms (the receptor for M-CSF). There was little effect of Ovx on cells expressing either RANK or c-Fms. These results demonstrate that CD45R expression identifies a subset of murine bone marrow cells whose ability to form OCL in vivo is regulated by estrogen in WT but not IL-1R1 KO cells. The effects of estrogen on bone mass may be related to these responses.

Publication types

  • Comparative Study
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Bone Marrow Cells / cytology
  • Bone Marrow Cells / metabolism
  • Cattle
  • Cells, Cultured
  • Estrogens / genetics
  • Estrogens / metabolism*
  • Female
  • Granulocyte Precursor Cells / cytology
  • Granulocyte Precursor Cells / metabolism*
  • Leukocyte Common Antigens / analysis*
  • Leukocyte Common Antigens / biosynthesis
  • Leukocyte Common Antigens / genetics
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Osteoclasts / cytology
  • Osteoclasts / metabolism*
  • Ovariectomy
  • Protein Tyrosine Phosphatase, Non-Receptor Type 1
  • Rats
  • Receptors, Interleukin-1 / deficiency
  • Receptors, Interleukin-1 / genetics


  • Estrogens
  • Receptors, Interleukin-1
  • Leukocyte Common Antigens
  • Protein Tyrosine Phosphatase, Non-Receptor Type 1