Primary and secondary cartilages of the neonatal rat: the femoral head and the mandibular condyle

Abstract

Primary and secondary cartilages differ in embryonic origin and in histological organization, and are generally considered to have a different mode of growth. However, few studies have directly compared the two types of cartilage of the same animal at the same age. Therefore, we analysed several histological and biochemical differences between secondary cartilage of the mandibular condyle and primary cartilage of the femoral head of 4-d-old rats. We evaluated the tissue organization, the level of DNA and glycosaminoglycan (GAG) synthesis, and the GAG and collagen content. The expression of collagen types I, II and III and of receptors for insulin-like growth factor (IGF)-I, fibroblast growth factor (FGF), and transforming growth factor (TGF)-beta were investigated by immunohistochemistry. The ex vivo DNA and GAG synthesis as well as the GAG content of femoral heads were much higher than that of mandibular condyles. Mandibular condyles expressed both collagen types I and II, while femoral heads expressed only type II collagen. In the mandibular condyles, receptors for IGF-I, FGF, and TGF-beta were observed mainly in the superficial layers, whereas they were found throughout the entire femoral head. In conclusion, major differences were found between both types of cartilage, which might be related to their specific functional demands.

Biglycan and Fibromodulin Have Essential Roles in Regulating Chondrogenesis and Extracellular Matrix Turnover in Temporomandibular Joint Osteoarthritis

“…To understand basic cellular mechanisms underlying TMJ OA, we harvested primary MCCs. Because the mandibular condylar cartilage is distinct from knee hyaline articular cartilage, [3][4][5][6][7][8] we compared MCCs with HACs isolated from the knee joint. Our mRNA and protein profiling revealed that the two cell populations share overlaping gene/protein expression patterns.…”

“…This suggests that MCCs may contain a unique population of precursor cells that are most likely derived from the articular zone, which is present in the TMJ but not in the knee. 8 Therefore, the specialized nature of MCCs underscores the importance of using them specifically to study the TMJ.…”

“…12 On the other hand, the femoral head of the knee joint is constituted entirely of hyaline cartilage and type II collagen. 8 Consequently, the cellular mechanisms underlying TMJ OA pathology may be different from other articular joints. However, no studies have been implemented to determine specific mechanisms regulating mandibular condylar chondrocytes (MCCs) because of the unavailability of cell lines and the difficulty of isolating primary MCCs.…”

Histologic Effects of Bilateral Adrenalectomy under the Light Microscopy on Rat Mandibular Condyle

“…The growth of the skull is governed and influenced by a number of factors [7][8][9][10]. The morphology of the temporomandibular joint reflects the complex development of the entire skull.…”

“…The mandibular condyle is a major growth site and plays a significant role during mandibular development. Cartilage of the mandibular condyle provides regional adaptive growth, endochondral bone growth and a movable articulation [8,9]. Thus information on skull morphogenesis as a whole is a prerequisite for understanding growth process in the TMJ.…”