Expression of amelin and trauma-induced dentin formation

Abstract

According to recent studies, amelin (ameloblastin, sheathlin) is expressed in young odontoblasts at the initiation of dentin formation during odontogenesis. The purpose of the present investigation was to study whether amelin is also expressed at the onset of traumainduced reparative dentin formation. The mandibular developing first molars of 5-day-old rats were surgically taken out, and their pulp tissue briefly separated from the inner dentin surface and immediately repositioned. Then the teeth were re-implanted in their alveoli. At 0, 2, 4, 6, 8, 12 or 14 days after surgery, the animals were sacrificed and the experimental teeth evaluated by histology and immunohistochemistry for amelin. At 2, 4, 6 and 8 days after surgery, the detached and traumatized odontoblasts in the experimental teeth exhibited increasing signs of degeneration and loss of intracellular structures. At days 6 and 8 after surgery, immunohistochemistry revealed a strong staining for amelin in the traumatized odontoblastic layer. Twelve and 14 days after replantation, only necrotic cell remnants of the traumatized odontoblasts were discernible. At this stage, no amelin could be detected by immunostaining. A wide zone of an unorganized mineralized tissue surrounded the odontoblastic cell remnants. On the pulpal side of the unorganized tissue, a new, highly organized tubular reparative dentin layer was observed, bordered by columnar odontoblast-like cells abutting on newly formed predentin.The results indicate that the initiation of trauma-induced reparative dentin formation mimics that of primary dentin formation and that amelin seems to be involved in both processes, possibly as a signaling molecule.

Ameloblastin upstream region contains structural elements regulating transcriptional activity in a stromal cell line derived from bone marrow

“…Our group has previously shown that rAMBN (20) and 5-HT (34) enhance proliferation and differentiation of mesenchymal stem cells. The rIFN-Y-enhanced promoter activity in the M2-10B4 cell line may be linked to our previous findings, where rAMBN strongly induced the IFN-Y pathway in osteoblasts (20) and DEX is a known factor in osteogenic differentiation (35), and strengthens the suggestion that AMBN may act as a signalling molecule in developing hard tissues (5,10,14,18,20,36).…”

“…The biological function of AMBN remains obscure, and it is now documented that AMBN expression is not restricted to enamel formation (5,6,10). In odontogenesis, Ambn is believed to be implicated in enamel biomineralization (11)(12)(13) and in interactions between the ameloblasts and the extracellular matrix (14)(15)(16).…”

FGF-9 accelerates epithelial invagination for ectodermal organogenesis in real time bioengineered organ manipulation

“…Preliminary results showed that FGF-9 can induce early, significant Ameloblastin, Amelogenin and Osteocalcin expression in mesenchymal cells cultured with FGF-9 (Additional file 1). These findings were concurrent with the gene expression of mesenchymal origin cells, such as odontoblasts, during the early stage of tooth development [19,20]. In addition, FGF-9 can induce early expression of the homeobox protein Msx genes Msx-1 in mesenchymal cells (Additional file 1), which is consistent with previous research [14].…”

“…Mesenchymal cells were cultured in vitro and FGF-9 (25 ng/ml) was added to the experimental group. FGF-9 significantly upregulated Ameloblastin and Amelogenin expression [19,20]. The homeobox protein Msx genes Msx-1 and Msx-2 (although expressed at low levels), and Osteocalcin were also upregulated after initial contact with FGF-9.…”

Immunohistochemical Characterization of Rapid Dentin Formation Induced by Enamel Matrix Derivative

“…On the basis of the timing and location of expression [23,24], Ambn could function in extracellular signaling during sequential and reciprocal developmental processes, cell adhesion, and/or act as crystal nucleator during dentin mineralization. Ambn expression has also been demonstrated during trauma-induced reparative dentin formation in adult teeth, suggesting that this protein also is expressed as a part of reparative processes in the dental pulp [25].…”