Molecular and Cellular Biology

Calcified Tissue International

, Volume 49, Issue 6, pp 421-426

Expression of bone sialoprotein (BSP) in developing human tissues

  • Paolo BiancoAffiliated withBone Research Branch, National Institute of Dental Research, National Institutes of Health
  • , Larry W. FisherAffiliated withBone Research Branch, National Institute of Dental Research, National Institutes of Health
  • , Marian F. YoungAffiliated withBone Research Branch, National Institute of Dental Research, National Institutes of Health
  • , John D. TermineAffiliated withBone Research Branch, National Institute of Dental Research, National Institutes of Health
  • , Pamela Gehron RobeyAffiliated withBone Research Branch, National Institute of Dental Research, National Institutes of Health

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Summary

Bone sialoprotein (BSP) and its messenger RNA were localized in developing human skeletal and nonskeletal tissues by means of immunohistochemistry andin situ hybridization. Both protein and mRNA were found in mature, bone-forming cells but not in their immature precursors. In addition, osteoclasts displayed positive immunostaining and high densities of autoradiographic grains byin situ hybridization experiments. BSP was expressed in fetal epiphyseal cartilage cells, particularly in hypertrophic chondrocytes of growth plates. Though neither the protein nor the mRNA were identified in a variety of other connective and nonconnective tissues, an unexpected finding was the expression of BSP in the trophoblast cells of placenta. These findings show that BSP is primarily an osteoblast-derived component of the bone matrix expressed at late stages of differentiation. We have also found that osteoclasts produce BSP, possibly as a mediator of cell attachment to bone.

Key words

Bone sialoprotein Developing bone Noncollagenous proteins In situ hybridization Osteoblast Osteoclast Cell adhesion