Chondroid Bone Research Articles

The in vitro behavior of fetal condylar cartilage in serum-free hormone-supplemented medium

Mandibular condyles of fetal mice 19–20 days in utero were kept in a serum-free organ culture system for up to 14 days and were investigated for their capacity to develop osteoid and to mineralize in vitro. After 3 days in culture, the cartilage of the mandibular condyle appeared to have maintained all its inherent structural characteristics, including its various cell layers: chondroprogenitor, chondroblastic, and hypertrophic. After 7–9 days in culture, no chondroblasts could be seen; instead, most of the cartilage consisted of hypertrophic chondrocytes. In addition, various areas throughout the explant revealed the appearance of osteoidlike material. The process of matrix mineralization progressed with time, and by the 14th day new bonelike material was found to occupy a larger portion of the explant. The newly formed matrix reacted positively with antibodies against type I and type III collagens, as well as against bone alkaline phosphatase. Electron microscopic examination showed that the mineralization appeared to be associated with collagen fibers as well as the matrix vesicles. In composition, the in vitro-formed mineral deposits resembled hydroxyapatite crystals. Biochemical assays indicated that the newly formed tissue reacted strongly for alkaline phosphatase and incorporated 45Ca. The findings of the present study imply that fetal condylar cartilage possesses the potential to develop in vitro osseouslike tissue even in a system that is serum-free. Due to the fact that the newly formed extracellular matrix mineralized and reacted positively to bone markers as well as to cartilage macromolecules, it would seem justifiable to define the new tissue as chondroid bone.

Chondroid bone on the upper pharyngeal jaws and neurocranial base in the adult fish Astatotilapia elegans.

Serial cross sections of several adult specimens of the cichlid Astatotilapia elegans were used to investigate the fate and structure of the chondroid bone on the articulation between upper pharyngeal jaws and neurocranial base. The tissue persists in the adult on the three elements on which it previously developed, i.e., infrapharyngobranchial III-IV, parasphenoid, and basioccipital bones. It consists of haphazardly arranged, large vesicular cells without a canalicular system, embedded in a matrix histologically indistinguishable from bone matrix. Except for a narrow zone at the distal side, it is mineralized throughout. As in younger stages, the fibrous covering of the chondroid bone forms the articular tissue proper on each of the three elements. Acellular bone, found at the basal margin of the chondroid bone, it is argued, does not result from endochondral replacement of the latter but rather from dermal ossification projecting from the marrow cavity. Although lacunae may be filled in this way with bone, true obliteration of cells does not occur, so that there is no metaplasia from chondroid bone to bone. The part played by the chondroid bone in the outgrowth of the joint apophyses is discussed.

Late skeletal development at the articulation between upper pharyngeal jaws and neurocranial base in the fish, Astatotilapia elegans, with the participation of a chondroid form of bone.

This paper presents light-microscopical details of the late development of skeletal tissues at the joint between upper pharyngeal jaws (UPJs) and neurocranial base (parasphenoid and basioccipital bones) in the acellular-boned teleost Astatotilapia elegans. On each of the supporting elements, a bone tissue (AB) is deposited that is anomalous because of its retention of cells within the matrix. Later, this layer is gradually replaced by the anomalous large-celled chondroid kind of bone (CB). Both AB and CB probably grow by apposition from the overlying fibrous layer. Osteoblastlike cells secrete osteoid, which soon calcifies and traps the cells. As in young cellular membrane bone, cells in the AB have a wide, elongate shape and lie amidst sparse, calcified, bonelike matrix but lack a canalicular system. Later generations of enclosed cells have a more vesicular shape, with at least some cells remaining alive in the calcified matrix. Appositional growth of the chondroid bone at its articular side is matched from a certain stage onward by erosion at its basal side. On the upper pharyngeal jaws this resorption is clearly related to the development of new teeth. Although in older stages and adults the chondroid tissue resembles a secondary cartilage, the term chondroid bone (CB) was preferred because of (1) the continuing formation by osteoblastlike cells; (2) the staining affinities of its matrix with that of bone; and (3) its formation both on cartilage bone (the infrapharyngobranchials III-IV and basioccipital bone) and on membrane bone (the parasphenoid bone).

Soft-tissue bone interface: how do attachments of muscles, tendons, and ligaments change during growth? A light microscopic study.

This study addressed the problem of how soft structures maintain approximately the same relative positional relationships during long bone growth. Attachments of the popliteus muscle, semitendinosus tendon, medial collateral knee ligament, and extensor retinaculum were examined histologically in rabbits, aged 2-60 days, to determine the manner in which soft structures attached to long bones during growth. Soft structures inserted principally into fibrous periosteum or perichondrium in the age range studied. However, an extensive collagen fiber framework within the cellular periosteum and perichondrium, present by at least 2 days of age, linked the fibrous periosteum or perichondrium to subjacent bone or cartilage. Maturation of soft tissue-bone interfaces was viewed from two related perspectives. The first stressed temporal patterning of cartilage and bone differentiation. The second emphasized incorporation of attachments of soft structures into bone and cartilage matrices during growth and remodeling. Differentiation and remodeling of bone and cartilage varied not only with age, but also between regions of attachment of single muscles and ligaments. Insertion regions were characterized by the presence of coarse-fibered periosteal bone and chondroid bone, both morphologically intermediate between fibrocartilage and lamellar bone. These results provide evidence that periosteal attachments, characterizing the soft-tissue bone interface, are a necessary structural prerequisite for compensatory movement and invariance of the relative positions of muscles, tendons, and ligaments during long bone growth.

Bone healing after amputation of mouse digits and newt limbs: Implications for induced regeneration in mammals

Postamputational healing was compared in nonregenerating and regenerating animals to determine whether bone healing might interfere with a regenerative response in mice. More than 150 mouse toes and 100 newt limbs were examined at the light microscope level. Stages of normal bone healing with approximate times of occurrence were established. Major differences in healing of these two species were seen. The periosteum produced hyaline cartilage, woven bone, and chondroid bone in mice, but only hyaline cartilage in newts. The endosteum produced woven bone in mice but no new growth in newts. Dead bone persisted in mice but was removed in newts. The marrow cavity became sealed in mice but remained open in newts. Despite these differences both animals produced skeletal tissue distal to the amputation plane. Woven bone formed distal to the amputation plane of mice. Cartilage formed distal to the amputation plane of newts, but cartilage was never seen distal to the plane of mice. Results of previous studies reveal that cartilage can be formed distal to the amputation plane of experimentally treated mice. Thus, although it does not regenerate, mouse bone is capable of producing, distal to the amputation plane, the type of skeletal tissue which appears at that location during an epimorphic regenerative response. This observation, in combination with other experimental results, indicates that both skeletal and soft tissues at the amputation site of treated mammals can resemble comparable tissues of newt limbs at an early stage of regeneration.

Presence of chondroid tissue in the symphyseal region of the growing human mandible.

The mandibular symphysis studied by histology and microradiography in the fetus and in the newborn shows a mineralized tissue different from the calcified cartilage observed in endochondral ossification and also different from bone aspects. In 1888, Schaffer coined it ‘chondroid bone’, but this tissue derives from secondary cartilage. We therefore suggest the term ‘chondroid tissue’ to designate it.

Chondroid Bone, Secondary Cartilage and Metaplasia

Chondroid Bone, Secondary Cartilage and Metaplasia

Modulation of chondrocyte activity in vitro in response to ascorbic acid.

The aim of this study was to examine the response of secondary cartilage to ascorbic acid in vitro. Cells which had not attained the prechondroblast stage when cultured, did not chondrify in vitro, even when exposed to high levels (400 microgram/ml) of ascorbic acid. On the other hand, prechondroblasts cultured in the presence of low levels (100 microgram/ml) of ascorbic acid did chondrify. Once cytodifferentiation commenced, chondrogenesis was independent of the presence of ascorbic acid in the medium. Cartilage which differentiated in the presence of continuous high levels ( greater than 200 microgram/ml) of ascorbic acid modulated to a tissue which consisted of hypertropic chondrocytes in a highly collagenous extracellular matrix. At the light-microscopic level, this tissue was classified as chondroid bone. At the ultrastructural level, the collagen was seen to be in the form of cross-banded fibres more typical of bone than cartilage. Prelabelling of cultures with either [3H]-thymidine or [3H]-proline showed that neither dedifferentiation of chondrocytes nor the resumption of mitotic activity was responsible for the alterations in the extracellular matrix. The differentiated chondrocytes can secrete an altered extracellular matrix without undergoing cytological dedifferentiation. The role of ascorbic acid in the attainment and maintenance of the differentiated state is briefly discussed.

The human incudomalleal joint. Chondroid articular cartilage and degenerative arthritis.

AbstractThe articular cartilage of the incudomalleal joint appears to be secondary or chondroid cartilage, formed and maintained by the synovial cells of the joint space. It might be considered epiphyseal cartilage, forming chondroid cartilage and chondroid bone normally within the deep cartilage of the joint. The early joint changes seen with age consist of globule formation and cell clustering in the superficial cartilage layer, with gradual transformation to a chondro‐osseous matrix at the surface. The changes of degenerative arthritis are loss of surface demarcation, focal surface defects, and foci of thinning and absence of the intra‐articular disc with approximation of uneven, calcified joint surfaces.

Articular and internal remodeling in the human otic capsule.

AbstractA comprehensive histologic study of the human otic capsule is presented demonstrating the interrelations between cartilage, bone, blood vessels and soft tissue throughout life. Remodeling occurs through continual degeneration of chondrocytes within the uncalcified articular surfaces of the stapediovestibular joint and through continual degeneration of cartilage about the cochlea and semicircular canals. Degenerated chondrocytes are removed by macrophages and new endochondral bone forms from adjacent osteogenically active blood vessels. The cartilage surfaces of the footplate and oval window are constantly replenished by new cartilage formed by mesenchymal cells of the annular ligament. Within the otic capsule, new cartilage forms from mesenchymal cells lining the labyrinth. Cartilage foci continually undergo partial replacement by endochondral bone with remnants of uncalcified cartilage matrix remaining, forming globuli ossei and interglobular spaces. In addition to continual endochondral bone formation partially replacing the continually forming and degenerating cartilage, chondroid bone forms by direct transformation of some cartilage to bone. These chondroid bone areas are cellular in young age groups, but become pale and relatively acellular with age. These processes occur throughout life, regardless of age or sex.