Putative role of basement membrane for dentinogenesis in the mesenchyme of murine dental papillae in vitro

Abstract

In a new culture-conditioning system of agar-coated mesenchyme of isolated incisor dental papillae, dentinogenesis has been induced adjacent to an agar substratum that functions as a foothold for cell immobilisation. To elucidate the role of the basement membrane (BM) in dentinogenesis, we have examined the way in which dentinogenesis depends upon BM components or transforming growth factor (TGF)-beta1 in this system. At the mesenchymal-epithelial junction of odontogenic organs (cut incisor tooth germs), TGF-beta1 visibly increased in the BM during incubation. In isolated dental papillae, BM components were synthesised and deposited at aligned peripheral cells of the explants, together with an increasing amount of TGF-beta1. These components were not assembled into extracellular matrix (ECM)-absorbed agar adjacent to explants, although dentinogenesis proceeded in the presence of pericellular BM components associated with TGF-beta1. When signalling via TGF-beta type II receptors was blocked, neither ECM production nor dentinogenesis was observed but explants partially detached from the agar surface, presumably as a result of the suppressed production of ECM, since attachment was retained by pre-coating explants with artificial matrices. Rescue experiments showed that TGF-beta1 regulated dentinogenesis through ECM production. With regard to BM components, inducible dentinogenesis was Arg-Gly-Asp (RGD)-dependent. Thus, pericellular BM components associated with TGF-beta1 and an ECM-absorbed agar substratum, which affects dentinogenesis, synergistically play a role similar to that of BM components in vivo. The BM therefore serves as a structural meshwork that acts as a foothold for cell immobilisation; its components act as ligands for RGD-dependent cell adhesion and it stores TGF-beta1, which regulates ECM production.

Odontoblasts induced from mesenchymal cells of murine dental papillae in three-dimensional cell culture

“…They were pre-coated with 2.0 mg/ml bovine type I collagen (Koken Co., Tokyo, Japan) mixed with 1.0 mg/ml mouse EHS laminin (Harbor Bio-products, Norwood, MA, USA). They were then coated with a 1.5% agar (Wako) solution (Kikuchi et al 2001). The agar blocks were incubated for 8 days in the same DMEM as described above.…”

“…Under experimental conditions, dentinogenesis can be induced by members of the transforming growth factor-β (TGF-β) superfamily combined with certain growth factors (Ruch et al 1995), and is induced adjacent to the structural surface of an ECM-absorbed agar substratum (Kikuchi et al 1996(Kikuchi et al , 2001. It can also be induced adjacent to artificial ECM or hydroxyapatite/tricalcium phosphate in grafts (Tziafas et al 1995;Gronthos et al 2000Gronthos et al , 2002.…”

“…Furthermore, the signals and pathways by which subodontoblastic cells differentiate into odontoblasts, including the TGF-β superfamily, fibroblast growth factors (FGFs) and insulin-like growth factors (IGFs), are also controversial. In an organ culture system under a three-dimensional microenvironment that provides the conditions needed for odontoblast differentiation, it has been postulated that the BM components and TGF-β 1 that are secreted, together with an ECM-absorbed agar substratum surrounding isolated dental papilla, play roles similar to those possibly played by BM in vivo (Kikuchi et al 2001). Moreover, the use of this system makes it possible to examine whether putative progenitor cells/stem cells in cells that are microinjected into dental papillae can migrate and differentiate into odontoblasts.…”

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In an organ culture system under a threedimensional microenvironment that provides the conditions needed for odontoblast differentiation, a row of odontoblasts can be induced (Kikuchi et al 1996(Kikuchi et al , 2001. Therefore, in a newly designed three-dimensional cell culture system that fulfils the conditions necessary for odontoblast differentiation (Kikuchi et al 2002), we examined whether dental papilla cells in rat mandibular incisors could differentiate into tubular dentine-forming cells.

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Essential role of ADAM28 in regulating the proliferation and differentiation of human dental papilla mesenchymal cells (hDPMCs)

“…The understanding that dentinogenesis can be induced by dental papilla under the effect of some growth factors like TGF-b or by contacting with Annexin v assay (c) and quantitative analysis (d) suggested that there were constitutively more numerous apoptotic cells in ADAM28 AS-ODN group specific extracellular matrix (ECM) substratum reveals remarkable new insights that hDPMCs may feature characteristics shared by putative progenitor cells/stem cells for dentin formation (Ruch et al 1995;Kikuchi et al 1996Kikuchi et al , 2001. The course of hDPMCs differentiation is synergistically or antagonistically modulated by sequential and interdependent transcription factors and accompanies the expression of corresponding markers.…”