Cell Fate Mediators in Mandibular Condylar Cartilage

Twist and Notch1 have been shown to modulate chondrogenic/osteogenic differentiation in progenitor cell populations. However, the presence of these factors in the mandibular condylar cartilage has not been studied. Objective: The goal of this study was to establish whether Twist and Notch1 were present in mouse mandibular condylar cartilage (MCC) and whether their gene expression could be altered by exogenous growth factors. Methods: Mandibular condyles with ramus bone harvested from E17 mice pups were placed in serum-free explant culture in media containing 0, 3, or 30 ng/mL of FGF-2 or TGF-ß2. After 3d, the MCC was dissected from the adjacent bone and the RNA extracted for real-time RT-PCR. In E17 half-heads, localization of Twist and Notch1 in MCC was examined using confocal microscopy. Results: Both Twist and Notch1 were localized primarily to the prechondroblastic (chondroprogenitor) layer of the MCC. Notch1 expression was upregulated 3-fold by FGF-2 and down-regulated 3-fold by TGF-ß2. Twist 2 was increased 3-fold by 3 ng/mL FGF-2 but decreased 6-fold by TGF-ß2. Twist 1 was less affected by either growth factor. Conclusions: As in other tissues, Notch1 and Twist may regulate differentiation of the pluripotent cells of the MCC. This study was supported by NIDCR grant DE015401 to RJH.