Localization of types I, II and X collagen and osteocalcin in intramembranous, endochondral and chondroid bone of rats

Abstract

Chondroid bone is a unique calcified tissue intermediate between bone and cartilage. To clarify its characteristics, we examined the distributions of the ECMs associated with chondrogenic differentiation and matrix calcification in the chondroid bone of the rat glenoid fossa, and compared them to those in two typical bone tissues, alveolar bone of the maxilla (intramembranous bone) and the growth plate of long bone (endochrondral bone), using immunofluorescence techniques. Morphologically, the glenoid fossa consisted of the fibrous, progenitor and cartilaginous cell layers and the cartilaginous cell layer was further divided into the superficial non-hypertrophic layers (secondary cartilage) and the deep hypertrophic cell layers (chondroid bone). The co-distribution of type I and type II collagens was observed in secondary cartilage and chondroid bone, whereas type X collagen was restricted to the pericellular matrix of hypertrophied cells (chondroid bone). Osteocalcin, which was absent from the calcified cartilage of endochondral bone formation, was also present in the ECM of the chondroid bone, but not in cells. These results demonstrate that chondroid bone of rats, which is adjacent to secondary-type cartilage in the glenoid fossa, has phenotypic expressions associated with both hypertrophied chondrocytes and osteocytes.

An immunohistochemical study of matrix proteins in the craniofacial cartilage in midterm human fetuses

“…Reportedly, cartilaginous tissue is present in the mandibular fossa or the continuous articular eminence of rats, 46,47 young monkeys. 48 Only a few studies have investigated whether this type of cartilage exists in the mandibular fossa of the human fetus.…”

The enigmas of bone without osteocytes

“…Even within tetrapods, there are several types of 'bony' tissues, ranging from the various and well-studied types of lamellar bone, to stable (nontransitional) bone-cartilage intermediates like chondroid bone, to hyperossified otic bone tissue. 4,5,24,25 These tissues, however, are unified by their compositional features, the vast majority of which are shared by the bones of fishes: fish bones consist of the same basic building blocks as tetrapod bones (type I collagen fibers and calcium phosphate crystals). 26 Furthermore, as with mammalian bone, fish bone provides a light yet stiff material to serve as anchor points for muscles and protection for internal organs (although the fish bone tissue itself is apparently less stiff than that of mammals 27,28 ).…”

Expression of osteogenic proteins during the intrasplenic transplantation of Meckel's chondrocytes: A histochemical and immunohistochemical study

“…Some investigators including Enlow (1962), Hall (1972), and Luder and Schroeder (1992) have suggested the possibility that the cells in the chondroid bone transdifferentiate into osteogenic cells. Mizoguchi et al (1997) detected the expression of types I, II, and X collagen as well as osteocalcin in the chondroid bone matrix of rat glenoid fossa using immunocytochemistry, and reported that, since neither the active deposition of a bone matrix nor intracellular labeling for osteocalcin were observed, the cells within the chondroid bone apparently displayed osteocytic, rather than osteoblastic, characteristics. These reports further support our hypothesis that neural crest-derived ectomesenchymal cells have a higher potential than mesoderm-derived cells for cellular transformation into bone-forming cells in response to altered environmental stimuli.…”