Biology Reference
In-Depth Information
Chapter 8
Degradation of Bone and the Role of Osteoclasts,
Bone Lining Cells and Osteocytes
Vincent Everts and Paul Saftig
Abstract Resorption of bone depends on the combined action of osteoblast-like
bone lining cells and osteoclasts. The bone lining cell plays an essential role in
modulating the formation of the osteoclasts and in the mean time prepares the bone
surface for these multinucleated bone resorbing cells to attach to. The osteoclast
attaches to the bone and the resorption starts with lowering the pH at the resorption
site, a site that is secluded from the rest of the bone surface and the surrounding
environment. The lowered pH results in dissolution of the mineral component, thus
exposing the matrix. The bone matrix is subsequently digested by proteolytic
enzymes, among which the cysteine proteinase cathepsin K appears to be essential.
Recent findings indicate that not all osteoclasts are alike, different bones may
harbour osteoclasts that differ in several aspects, among which the proteolytic
enzymes used for resorption. In this chapter we will discuss the different steps
that result in the degradation of bone, the onset of new bone matrix deposition and
the presence of different osteoclasts at various bone sites.
Abbreviations
AE2
Anion exchanger 2
CCl9
Chemokine ligand 9
ClC7
Chloride channel 7
DC-STAMP
Dendritic cell-specific transmembrane protein
V. Everts (
*
)
Department of Oral Cell Biology, Academic Centre for Dentistry Amsterdam University of
Amsterdam and VU University Amsterdam, Research Institute MOVE, G. Mahlerlaan 3004,
1081 LA Amsterdam, The Netherlands
e-mail: v.everts@acta.nl
P. Saftig
Biochemisches Institut Christian-Albrecht-Universit
at Kiel, 24098 Kiel, Germany
€
