Osteoclasts are multinuclear cells of the monocyte macrophage lineage. They are responsible
for bone remodeling by first resorbing packets of bone, which are subsequently replaced by new bone
produced by osteoblasts. Osteoblasts are derived from mesenchymal stem cells, and thus osteogenesis can
also be induced in various tissues at extra skeletal sites. Fifty years ago it was discovered that demineralized
bone matrix is able to induce ectopic bone formation. Since that time the differentiation of bone cells
has been studied intensively. The aim was to produce bone for the repair of bone defects. The molecular
basis of bone remodeling has been established in great detail and the mechanism of how bone resorption
and bone formation are coupled in bone remodeling sites has been delineated. Osteoclasts resorb bone,
but they also secrete anabolic signals that induce mesenchymal stem cells and osteoblasts to initiate osteogenesis
in resorption lacuna (remodeling) or another nonresorbed site (modeling). It is this osteoclast
derived influence on mesenchymal stem cells and osteoblasts that could be utilized in tissue engineering.
So far investigators have tried to find ways to induce bone formation by activating mesenchymal stem
cells, but a better understanding of the remodeling paradigm of bone, the intrinsic regulation of bone formation
through osteoclastic resorption, could be utilized for tissue engineering. Scaffold materials like
decellularized natural tissue extracellular matrices or bone type resorbable mineral matrices induce resorption
and simultaneously induce bone formation.
Keywords: Collagen, decalcified, decellularized, hematopoietic, mesenchymal, osteoblast, osteoclast, scaffold, stem cell.
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