Development with age of the human mandibular condyle: histological study

Evaluating the mandibular condyles of patients with osteoarthritis for bone marrow abnormalities using magnetic resonance T2 mapping

OBJECTIVES

This study investigated whether erosion and osteophyte correlates with condyle bone marrow abnormalities (BMA), as detected with quantitative T2 mapping.

METHODS

Fifty-six joints (in 44 patients) that demonstrated evidence of bony erosion (ER) or osteophytes (OS) related to disc displacement without reduction were studied with MR images. A control group of 50 joints (in 50 patients) was included. The subjects were divided into five groups; noAR (control), noBMA-ER, BMA-ER, noBMA-OS, and BMA-OS. T2 mapping was performed and the regions of interest were placed over the bone marrow at the top of the condyle. The mean T2 values of the bone marrow of the mandibular condyle were calculated for all mapping images. After assessing age-related changes in T2 values of noAR group using Pearson's product-moment, differences in median T2 values of five groups were analyzed using Kruskal-Wallis test, and Steel-Dwass test (p < 0.05).

RESULTS

There was no significant correlation between age and T2 value in noAR group. The median T2 values of noBMA-ER and BMA-ER groups were significantly higher than those of noAR, noBMA-OS and BMA-OS groups. Those of noBMA-OS and BMA-OS groups were significantly lower than those of noAR, noBMA-ER and BMA-ER groups. There was no significant difference between noBMA and BMA groups.

CONCLUSIONS

It is suggested that erosion and osteophyte of the condyle may correlate with bone marrow abnormalities. T2 mapping could be show slight marrow changes of the arthritic condyle.

An Immunohistochemical Study of Matrix Components in Early-Stage Vascular Canals Within Mandibular Condylar Cartilage in Midterm Human Fetuses

Matrix components of vascular canals (VCs) in human fetal mandibular condylar cartilage (15-16 weeks of gestation) were analyzed by immunohistochemistry. Prevascular canals (PVCs), consisting of spindle-shaped cells without capillary invasion, were observed within the cartilage. Intense immunoreactivity for collagen type I, weak immunoreactivity for aggrecan and tenascin-C, weak hyaluronan (HA) staining, and abundant argyrophilic fibers in PVCs indicated that they contain noncartilaginous fibrous connective tissues that was different from those in the perichondrium/periosteum. These structural and immunohistochemical features of PVCs are different from those of previously reported cartilage canals of the long bone. Capillaries entered the VCs from the periosteum and ascended through VCs. Following capillary invasion, loose connective tissue had formed in the lower part of VCs, and immunoreactivity for collagen types I and III, tenascin-C, and HA staining was evident in the matrix of loose connective tissue. No chondroclasts or osteogenic cells were seen at the front of capillary invasion, although small, mononuclear tartrate-resistant acid phosphatase (TRAP)-positive cells were present. Meanwhile, TRAP-positive, multinucleated chondroclasts and flattened, osteoblast-like cells were observed in the loose connective tissue at the lower part of VCs. These results may indicate slow progress of endochondral ossification in human fetal mandibular condyle. Further, unique matrix components in PVCs/VCs, which were different from those in cartilage canals in long bone, may reflect the difference of speed of endochondral ossification in cartilage canals and human fetal mandibular condyles.

Development of the mandibular condylar cartilage in human specimens of 10-15 weeks' gestation

This study analyses some morphological and histological aspects that could have a role in the development of the condylar cartilage (CC). The specimens used were serial sections from 49 human fetuses aged 10-15 weeks. In addition, 3D reconstructions of the mandibular ramus and the CC were made from four specimens. During weeks 10-11 of development, the vascular canals (VC) appear in the CC and the intramembranous ossification process begins. At the same time, in the medial region of the CC, chondroclasts appear adjacent to the vascular invasion and to the cartilage destruction. During weeks 12-13 of development, the deepest portion of the posterolateral vascular canal is completely surrounded by the hypertrophic chondrocytes. The latter emerge with an irregular layout. During week 15 of development, the endochondral ossification of the CC begins. Our results suggest that the situation of the chondroclasts, the posterolateral vascular canal and the irregular arrangement of the hypertrophic chondrocytes may play a notable role in the development of the CC.

Development of the human temporomandibular joint

A great deal of research has been published on the development of the human temporomandibularjoint (TMJ). However, there is some discordance about its morphological timing. The most controversial aspects concern the moment of the initial organization of the condyle and the squamous part of the temporal bone, the articular disc and capsule and also the cavitation and onset of condylar chondrogenesis. Serial sections of 70 human specimens between weeks 7 and 17 of development were studied by optical microscopy (25 embryos and 45 fetuses). All specimens were obtained from collections of the Institute of Embryology of the Complutense University of Madrid and the Department of Morphological Sciences of the University of Granada. Three phases in the development of the TMJ were identified. The first is the blastematic stage (weeks 7-8 of development), which corresponds with the onset of the organization of the condyle and the articular disc and capsule. During week 8 intramembranous ossification of the temporal squamous bone begins. The second stage is the cavitation stage (weeks 9-11 of development), corresponding to the initial formation of the inferior joint cavity (week 9) and the start condylar chondrogenesis. Week 11 marks the initiation of organization of the superior joint cavity. And the third stage is the maturation stage (after week 12 of development). This work establishes three phases in TMJ development: 1) the blastematic stage (weeks 7-8 of development); 2) the cavitation stage (weeks 9-11 of development); and 3) the maturation stage (after week 12 of development). This study identifies the critical period of TMJ morphogenesis as occurring between weeks 7 and 11 of development.