what is the interaction between the osteoclast?

Answer 1

Ultrastructural study of cell-cell interaction between osteoclasts and osteoblasts/stroma cells in vitro.Domon T, Yamazaki Y, Fukui A, Ohnishi Y, Takahashi S, Yamamoto T, Wakita M.
Department of Oral Health Science, Hokkaido University Graduate School of Dental Medicine, Sapporo, Japan.

Many biochemical reports support cell-cell interaction between osteoclasts and osteoblasts/stroma cells in vitro, however there have been few morphological studies supporting this. Details of cell-cell interaction between osteoclasts and osteoblasts/stroma cells remain unclear. The present study examined cell-cell interaction between osteoclasts and osteoblasts/stroma cells by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Osteoclasts, osteoblasts/stroma cells, and bone marrow cells obtained from 10-day-old ddY mice were cultured on dentin slices for 72 hr. Specimens were fixed, and some were examined by SEM. Specimens were decalcified, embedded in Epon after determination of the tartrate-resistant acid phosphatase activity (TRAP), and TRAP-positive cells for investigation were serially sectioned by alternating semithin and ultrathin sections, and then examined by TEM. By SEM, many cellular contacts were seen between the cells cultured on the dentin, but by TEM there were few special structures on the cell membranes between osteoclasts and osteoblasts/stroma cells, or between osteoclasts and bone marrow cells. A special structure on the cell membranes of osteoclasts was observed between an osteoclast and a cytoplasmic process of osteoblast/stroma cells, and this cell membrane was coated with electron dense or bristle-like structures. These bristle-like structures were very similar to those of coated pits. The present results show that the coated pit-like structure plays an important role in cell-cell interaction between osteoclasts and osteoblasts/stroma cells in vitro, and suggest that macromolecules binding to the osteoclast-surface receptor via ligands, accumulate in the coated pits, and enter the osteoclast as receptor-macromolecule complexes in endocytic vesicles.

PMID: 12056751 [PubMed - indexed for MEDLINE]
Related LinksThree-dimensional distribution of the clear zone of migrating osteoclasts on dentin slices in vitro. [Tissue Cell. 2002] PMID: 12270259 Osteoblast proliferation and differentiation on dentin slices are modulated by pretreatment of the surface with tetracycline or osteoclasts. [J Periodontol. 2000] PMID: 10807123 Osteoclast function is activated by osteoblastic cells through a mechanism involving cell-to-cell contact. [Endocrinology. 1996] PMID: 8612568 Osteoblast-like cells complete osteoclastic bone resorption and form new mineralized bone matrix in vitro. [Calcif Tissue Int. 2004] PMID: 15148559 Formation of osteoclasts and osteoblast-like cells in long-term human bone marrow cultures. [APMIS. 1991] PMID: 2018639 See all Related Articles...

Answer 2

Osteoclasts are the cells responsible for bone resorption (remodeling of bone to reduce its volume). Osteoclasts are large, multinucleated cells located on bone surfaces in what are called Howship's lacunae. These lacunae, or resorption pits, are left behind after the breakdown of bone and often present as scalloped surfaces. Because the osteoclasts are derived from a monocyte stem-cell lineage, they are equipped with engulfment strategies similar to circulating macrophages. Osteoclasts mature and/or migrate to discrete bone surfaces. Upon arrival, active enzymes, such as tartrate-resistant acid phosphatase, are secreted against the mineral substrate.
The process of bone resorption releases stored calcium into the systemic circulation and is an important process in regulating calcium balance. As bone formation actively fixes circulating calcium in its mineral form, removing it from the bloodstream, resorption actively unfixes it thereby increasing circulating calcium levels. These processes occur in tandem at site-specific locations and are known as bone turnover or remodeling. Osteoblasts and osteoclasts, coupled together via paracrine cell signalling, are referred to as bone remodeling units. The iteration of remodeling events at the cellular level is influential on shaping and sculpting the skeleton during growth and in response to stress (such as weight-bearing exercise or bone