In situ hybridisation study of type I, II, X collagens and aggrecan mRNAs in the developing condylar cartilage of fetal mouse mandible

Abstract

The aim of this study was to investigate the developmental characteristics of the mandibular condyle in sequential phases at the gene level using in situ hybridisation. At d 14.5 of gestation, although no expression of type II collagen mRNA was observed, aggrecan mRNA was detected with type I collagen mRNA in the posterior region of the mesenchymal cell aggregation continuous with the ossifying mandibular bone anlage prior to chondrogenesis. At d 15.0 of gestation, the first cartilaginous tissue appeared at the posterior edge of the ossifying mandibular bone anlage. The primarily formed chondrocytes in the cartilage matrix had already shown the appearance of hypertrophy and expressed types I, II and X collagens and aggrecan mRNAs simultaneously. At d 16.0 of gestation, the condylar cartilage increased in size due to accumulation of hypertrophic chondrocytes characterised by the expression of type X collagen mRNA, whereas the expression of type I collagen mRNA had been reduced in the hypertrophic chondrocytes and was confined to the periosteal osteogenic cells surrounding the cartilaginous tissue. At d 18.0 of gestation before birth, cartilage-characteristic gene expression had been reduced in the chondrocytes of the lower half of the hypertrophic cell layer. The present findings demonstrate that the initial chondrogenesis for the mandibular condyle starts continuous with the posterior edge of the mandibular periosteum and that chondroprogenitor cells for the condylar cartilage rapidly differentiate into hypertrophic chondrocytes. Further, it is indicated that sequential rapid changes and reductions of each mRNA might be closely related to the construction of the temporal mandibular ramus in the fetal stage.

Roles of Chondrocytes in Endochondral Bone Formation and Fracture Repair

“…This trend continued in the P21 mice, with more trabeculae apparent. Because prechondroblastic cells also secrete aggrecan (Fukada et al 1999), the pool of cells giving rise to bone cells was not purely comprised of chondrocytes. However, these images suggest that chondrocyte-derived bone cells are the primary agents of bone formation not only in the immediate subchondral bone but also in the entire condylar neck and upper ramus (Fig.…”

The biological mechanisms of PCNA and BMP in TMJ adaptive remodeling

“…BMPs also increase Cbfa1/Runx2 expression and stimulate differentiation (transcription factors required for osteogenic commitment and differentiation). [13][14][15][16] BMPs are molecular cues for osteoprogenitor cells to differentiate into osteoblasts. 17,18 Therefore, it is reasonable to speculate that, because of their unique properties, BMPs play a fundamental role in condylar remodeling in response to bite-jumping appliances.…”

Immunohistochemistry for Matrix Proteins in newly formed Mandibular Condylar Cartilage in a Human Fetus

“…We have demonstrated that newly formed condylar cartilage is derived from alkaline phosphatase-positive periosteum-like tissue, and supported this definition in mice and rats [7,8]. We also demonstrated that chondrocytes in initially formed condylar cartilage is rapidly differentiated into hypertrophic chondrocytes, and simultaneously expresses many kinds of matrix components including collagen types I, II, X, aggrecan, versican, hyaluronan, bone sialoprotein and osteopontin [7][8][9][10][11]. In human, we demonstrated that the newly formed condylar cartilage is continuous with the ossifying mandible [8], and also demonstrated that immunohistochemical localization of matrix proteins in already formed condylar cartilage in midterm fetuses [12].…”

“…These results lead to the conclusion that newly formed condylar cartilage has fibrocartilaginous characteristics and progenitor cells of this cartilage rapidly differentiate into hypertrophic chondrocytes, which can express many kinds of molecules simultaneously [7][8][9][10][11]. This is also characteristic of avian secondary cartilage [16].…”