Light and electron microscopic morphology of the temporomandibular joint in growing and mature crab-eating monkeys (Macaca fascicularis): the condylar articular layer

Abstract

In an attempt to establish maturational alterations in the morphology of the articular tissue layer, mandibular condyles of four immature and four mature male monkeys (Macaca fascicularis) were studied using light microscopy as well as scanning and transmission electron microscopy. Specimens were fixed in situ by perfusion in the presence of ruthenium red to stabilize proteoglycans. Preparations intended for observation in the scanning electron microscope were first dehydrated and sputtered for the examination of articular surfaces, and afterwards treated with trypsin to expose the spatial arrangement of collagen fibrils. Gross anatomical relations between joint components indicated that the anterior and central, but not the posterior region of the condylar articular surface can be subject to compressional load. Load-bearing and non-load-bearing regions differed with respect to the morphology of the articular layer. Load-bearing surfaces were covered by a prominent articular surface lamina similar to that observed on articular cartilage. This lamina seemed to constitute an integral part of the articular layer, distinct from the lining of synovial fluid, and to be composed largely of proteoglycans. It was unaffected by maturation. The subjacent, load-bearing articular layer differed markedly in structure, both from articular cartilage, and between immature and mature animals. Articular cells of immature animals were classified as fibroblastlike, but unlike typical fibroblasts, were surrounded by a thin, often incomplete halo of fibril-free pericellular matrix, presumably consisting of proteoglycans. In mature animals, articular cells closely resembled chondrocytes, but exhibited prominent nuclear fibrous laminae, which usually are found only in fibroblasts. Thus, the load-bearing part of the articular layer seems to undergo a maturation-dependent metaplastic conversion, from a dense connective tissue with some features of fibrocartilage, to a fibrocartilage-like tissue containing chondrocyte-like cells with some features of fibroblasts. This conversion might reflect an adaptation to a maturation-associated increase in articular stress.

Biomechanical properties of the mandibular condylar cartilage and their relevance to the TMJ disc

“…Table 2 summarizes available data for the fiber/fibrils diameters. Regarding orientation, previous microscopic structural investigations of the condylar cartilage indicated that the collagen fibers in the fibrous zone appear to run predominately parallel to the surface but not to each other, forming sheet-like structures (de Bont et al, 1984;Klinge, 1996;Luder and Schroeder, 1990;Mizuno et al, 1990;Shibata et al, 1991), indicating a transversely isotropic fiber orientation. However, in a recent macroscopic investigation of the condylar cartilage, an anisotropic fiber orientation in the fibrous zone of porcine condylar cartilage was observed via polarized light, where the predominant orientation of collagen fibers was in the anteroposterior direction , which coincides well with the mechanical anisotropy of the tissue (Kang et al, 2000a;Singh and Detamore, 2008).…”

Mandibular Cartilage Collagen Network Nanostructure

“…3 The HIM and TEM images revealed that the fibrous zone was composed of distinct layers of collagen bundles that were approximately orthogonal. This arrangement was also demonstrated in MCC of 8 week rats, 26 immature and mature cynomolgus monkeys, 27 and adult humans. 28 In the present study, the thicker layers were aligned in the anterior-posterior direction, the primary direction of condyle motion and shear loading.…”

Light and electron microscopic morphology of the temporomandibular joint in growing and mature crab-eating monkeys (Macaca fascicularis): the condylar calcified cartilage

“…During the growth period, transition from cartilage to bone took place far posterior to and below the top of the condyle. This location corresponds to a region of the articular surface which, even when the mouth is fully opened, is very unlikely to be subjected to compressive stress (Luder and Schroeder 1990). Therefore, the extension of cartilage in the growing condyle does not seem to depend primarily on articular loading, but possibly on other factors such as, for instance, the particular nutritional conditions faced by articular tissues.…”

“…These animals have been characterized previously with respect to their somatic development (Luder and Schroeder 1990). Likewise, the procedures applied to prepare the left and right mandibular condyles for LM, TEM and SEM have been described in the earlier report.…”

“…In order to characterize morphological maturation in the articular tissues of the temporomandibular joint, a series of light and electron microscopic studies of growing and adult monkeys has been initiated (Luder and Schroeder 1990). In the present investigation, second in this series, age-related differences in the mineralized tissues subjacent to the articular surface of the mandibular condyle, i.e.…”