Inductive specificity of mineralized bone matrix in ectopic osteoclast differentiation

Abstract

The present report describes the first in a series of studies designed to identify the factor or factors responsible for eliciting osteoclast differentiation. Particles of mineralized and demineralized bone, hydroxyapatite (HA), and eggshell were grafted onto the chorioallantoic membranes (CAMs) of chick embryos. After 3 of 6 days, portions of CAMs with associated grafts were harvested, processed for light and electron microscopy, and examined for the presence of multinucleated giant cells with the morphological characteristics of osteoclasts. Light microscopic examination revealed that, within only 3 days, many particles of mineralized materials had become surrounded or engulfed by multinucleated giant cells. Ultrastructurally, all such cells possessed a vacuolated and mitochondria-enriched cytoplasm, but they differed in the nature of the contacts formed at the cell-particle interface. With eggshell, the cells developed filopodia but lacked clear zones and ruffled membranes. With HA, clear zones were evident but cytoplasmic extensions and membrane ruffling were absent. Implants of mineralized bone, however, elicited the formation of giant cells with prominent clear zones and ruffling of the plasma membrane like that observed in bonafide osteoclasts. In contrast, grafts of demineralized bone did not evoke giant cell formation but rather recruited two cell types morphologically akin to either fibroblasts or macrophages. We conclude that the factor(s) responsible for osteoclast differentiation resides specifically within bone matrix and is intimately associated with the mineral phase. Further, in response to such a factor(s), osteoclast differentiation can occur ectopically, outside of the developing vertebrate body.

Saccharides mediate the attachment of rat macrophages to bone in vitro.

“…Similarly, observations by us (10,11) and other investigators on osteoclast development in vivo (12,13) indicate that contact between the osteoclast precursor (a cell belonging to the MO family) and mineralized bone is also essential for the initiation and completion of osteoclast differentiation. This realization of the pivotal role played by cell-matrix interaction in osteoclast formation and resorptive activity raises the question of how MO recognize and attach to bone surfaces.…”

“…These adhesive interactions determine not only whether the cell may engage in phagocytic or locomotory activity, but also its ability to respond to agents in its environment (e.g., hormones) (22), its principal physiological role (e.g., the activation of the lysosomal apparatus) (23), and its phenotypic expression and proliferative functions (24,25). In the particular instance of the M0 in bone, contact with the mineralized substrate appears essential for the development of the osteoclast phenotype (11).…”

Receptor activator of NF-κB ligand enhances the activity of macrophages as antigen presenting cells

“…In the presence of M-CSF, cell cycle withdrawal induced by RANKL is coordinated with differentiation into osteoclasts (Sanka et al, 2003). Although macrophages differentiate into osteoclasts by M-CSF plus RANKL in vitro, there are evidences that osteoclasts are differentiated only around mineralized materials in vivo (Krukowski and Kahn, 1982;Glowacki et al, 1986;Goldring et al, 1988). Even in vitro, osteoclastogenesis did not B occur efficiently in the semisolid culture system (Miyamoto et al, 2000).…”

The preosteoclast and its cytodifferentiation into the osteoclast: Ultrastructural and histochemical studies of rat fetal parietal bone.

“…x 24,000 ing the bone surface by regulating the surface area of exposed bone. As a result of the direct contact with the mineralized bone surface, the preosteoclasts may receive stimuli from factor(s) residing within the mineralized bone matrix, which lead to the differentiation into osteoclasts with ruffled border (KRUKOWSKI and KAHN, 1982). If preosteoclasts are capable of digesting bone matrix, there may be a release of osteocalcin, a, HS-glycoprotein and Type I collagen peptide, which are considered to be the chemoattractants for osteoclast precursor cells and induce other preosteoclasts (KAHN et al, 1981a).…”