Novel roles of Ten-m/Odz3 in development of mandibular condylar cartilage

Objectives: Mandibular condyle has been speculated that it develops by differentiation of fibroblast-like cells covering the surface of the condyle to the chondrocyte, and by its subsequent endochondral ossification. However, it's developmental mechanisms have not been revealed. Previouosly, by applying laser-captured microdissection and cDNA microarray analysis, we found Ten-m/Odz3 showed high expression in the fibrous tissues on the superficial layer of mandibular condylar cartilage. Ten-m/odz3 is reported that to be concentrated in the developing and adult central nervous system and at site of pattern formation including the developing limb bud in vertebrates. However, little is known about temporal and spatial expression of ten-m/odz3 in cartilage. The aim of this study was to investigate the gene expression of Ten-m/Odz3 in mandibular condylar cartilage during development in the mice.

Methods: The mandible of 1, 7 and 21-day-old ICR mice were dissected, fixed, decalcified and embedded in paraffin. In situ hybridization using Digoxigenin-11-UTP labeled probe were performed. In addition, to examine the expression pattern of Ten-m/Odz3 during chondrogenic maturation in vitro, we performed reverse transcriptase-polymerase chain reaction using ATDC5 cells, a mouse chondrogenic cell line.

Results: Ten-m/Odz3 mRNA was distributed in fibrous and proliferating chondrocyte layers in which type I and II collagen mRNA was recognized, but not expressed in hypertrophic layer in which Type X collagen mRNA was found in 1, 7 and 21-day-old mice. In ATDC5 cells, strong ten-m/odz3 mRNA signal was also detected in early time points of culture that type II collagen mRNA expressed.

Conclusion: We found the novel expression pattern of Ten-m/Odz3 in incipient chondrogenic maturation in vivo and in vitro. Our findings suggest that Ten-m/Odz3 may act, at least in part, as a regulating factor in early developmental stage of chondrocyte, hypothetically to modulate the differentiation of mesenchymal cells and proliferation of chondrocytes.