Jae-Hyun Sung

BMP-2-induced Runx2 Expression Is Mediated by Dlx5, and TGF-β1 Opposes the BMP-2-induced Osteoblast Differentiation by Suppression of Dlx5 Expression

Intramuscular injection of BMP-2 induces ectopic bone formation in vivo. Similarly, BMP-2 treatment blocks myogenic differentiation and induces osteoblastic transdifferentiation of premyoblastic C2C12 cells. Previous reports suggested that BMP-2-stimulated Runx2 expression could play a pivotal role in transdifferentiation. However, increased Runx2 expression by TGF-β1 did not support osteoblast differentiation in vitro. These results indicate that the induction of Runx2 is not sufficient to explain the BMP-induced transdifferentiation. We found that Dlx5 is specifically expressed in osteogenic cells, and is specifically induced by BMP-2 or -4 signaling but not by other osteotrophic signals or other TGF-β superfamily members. Cycloheximide treatment indicated that Dlx5 was immediately induced by BMP signaling, while Runx2 required de novo protein synthesis. In addition, blocking or overexpressing each transcription factor indicated that Dlx5 is an indispensable mediator of BMP-2-induced Runx2 expression but is not involved in TGF-β1-induced Runx2 expression. Moreover, TGF-β1 opposed BMP-2-induced osteogenic transdifferentiation through Dlx5 suppression by de novo induction of AP-1. Taken together, these results indicate that Dlx5 is an indispensable regulator of BMP-2-induced osteoblast differentiation as well as the counteraction point of the opposing TGF-β1 action.

Nonextraction treatment with microscrew implants.

The maxillary and mandibular posterior teeth were retracted with microscrew implants (1.2 mm in diameter and six to 10 mm long) that were placed into the alveolar bone and used as anchorage. The retraction proceeded without adverse reciprocal effects on the reactive part of the conventional mechanics, such as premolar extrusion and flaring of the incisors. The anterior crowding was resolved without any deleterious effect on the facial profile. En masse movement of the posterior teeth and the whole dentition after anterior tooth alignment can reducethe treatment period and maximize the efficiency of the treatment. The microscrew implants were maintained firmly throughout the treatment and were able to provide an anchorage for retraction of whole dentitions. The efficacy and potency of the microscrew implants aid mechanics in the nonextraction treatment of both labial and lingual treatments.

L’ancrage des micro-implants dans le système des forces directionnelles

Resume Le D r Merrifield nous a vivement encourages a utiliser la technique des forces directionnelles afin d’ameliorer l’esthetique faciale, d’obtenir une occlusion harmonieuse et une bonne stabilite des resultats. Neanmoins, la reussite de ce type de traitement depend en grande partie de la cooperation de nos patients en raison du port d’un casque de FEO utilise comme ancrage orthodontique. Par ailleurs, la duree de ce type de traitement etait assez longue. Pour notre part, nous avons utilise des micro-implants comme ancrage orthodontique a la place des FEO avec de bons resultats, en accord avec la philosophie Tweed-Merrifield. Les micro-implants n’exigent pas la cooperation des patients, raccourcissent la duree de traitement et fournissent de bons resultats. Les micro-implants pourraient nous fournir un ancrage absolu.