Abstract:The regeneration process of the odontoblast cell layer incident to tooth injury, especially its relationship with immunocompetent cells in pulp healing, has not been fully understood. The purpose of the present study was to clarify this relationship between odontoblasts and immunocompetent cells in the process of pulp regeneration following cavity preparation in rat molars by immunocytochemistry for heat shock protein (Hsp) 25 as well as class II major histocompatibility complex (MHC) molecules. In untreated c… Show more
“…This finding is different from that reported by Schmalz et al (2001) who have shown that SV40 large T-antigen-transfected bovine pulp-derived cells proliferate extensively on processed dentin and do not show odontoblast-like morphology after 14 days. Whereas recent reports suggest that newly differentiated odontoblasts extend their processes into existing dentinal tubules after pulp injury in rats in an in vivo setting (Nakakura- Ohshima et al 2003;Ohshima et al 2003), our finding is the first evidence for the phenomenon that human pulp cells of odontoblast-lineage differentiate into odontoblasts in vitro upon contact with dentin, even if it has been treated mechanically and chemically. The chemical treatment of dentin (e.g., by EDTA) may solubilize various noncollagenous dentin matrix components and growth factors, such as transforming growth factor-β1, which may have an inductive effect on the differentiation of odontoblast progenitor cells (Smith 2002).…”
Our purpose was to characterize human dental pulp cells isolated by various methods and to examine the behavior of cells grown under various conditions for the purpose of pulp/dentin tissue engineering and regeneration. We compared the growth of human pulp cells isolated by either enzyme digestion or the outgrowth method. Expression of dentin sialophosphoprotein, Cbfa1, and two types of collagen (I and III) in these cells was examined by Western blot or reverse transcription/polymerase chain reaction. Growth of pulp cells on dentin and in collagen gel was also characterized. We found that different isolation methods give rise to different populations or lineages of pulp cells during in vitro passage based on their collagen gene expression patterns. Cells isolated by enzymedigestion had a higher proliferation rate than those isolated by outgrowth. Pulp cells did not proliferate or grew minimally on chemically and mechanically treated dentin surface and appeared to establish an odontoblast-like morphology with a cytoplasmic process extending into a dentinal tubule as revealed by scanning electron microscopy. The contraction of the collagen matrix caused by pulp cells was dramatic: down to 34% on day 14. Our data indicate that (1) the choice of the pulp cell isolation method may affect the distribution of the obtained cell populations, (2) a treated dentin surface might still promote odontoblast differentiation, and (3) a collagen matrix may not be a suitable scaffold for pulp tissue regeneration because of the marked contraction caused by pulp cells in the matrix. The present study thus provides important information and a basis for further investigations pre-requisite to establishing pulp tissue engineering/regeneration protocols.
“…This finding is different from that reported by Schmalz et al (2001) who have shown that SV40 large T-antigen-transfected bovine pulp-derived cells proliferate extensively on processed dentin and do not show odontoblast-like morphology after 14 days. Whereas recent reports suggest that newly differentiated odontoblasts extend their processes into existing dentinal tubules after pulp injury in rats in an in vivo setting (Nakakura- Ohshima et al 2003;Ohshima et al 2003), our finding is the first evidence for the phenomenon that human pulp cells of odontoblast-lineage differentiate into odontoblasts in vitro upon contact with dentin, even if it has been treated mechanically and chemically. The chemical treatment of dentin (e.g., by EDTA) may solubilize various noncollagenous dentin matrix components and growth factors, such as transforming growth factor-β1, which may have an inductive effect on the differentiation of odontoblast progenitor cells (Smith 2002).…”
Our purpose was to characterize human dental pulp cells isolated by various methods and to examine the behavior of cells grown under various conditions for the purpose of pulp/dentin tissue engineering and regeneration. We compared the growth of human pulp cells isolated by either enzyme digestion or the outgrowth method. Expression of dentin sialophosphoprotein, Cbfa1, and two types of collagen (I and III) in these cells was examined by Western blot or reverse transcription/polymerase chain reaction. Growth of pulp cells on dentin and in collagen gel was also characterized. We found that different isolation methods give rise to different populations or lineages of pulp cells during in vitro passage based on their collagen gene expression patterns. Cells isolated by enzymedigestion had a higher proliferation rate than those isolated by outgrowth. Pulp cells did not proliferate or grew minimally on chemically and mechanically treated dentin surface and appeared to establish an odontoblast-like morphology with a cytoplasmic process extending into a dentinal tubule as revealed by scanning electron microscopy. The contraction of the collagen matrix caused by pulp cells was dramatic: down to 34% on day 14. Our data indicate that (1) the choice of the pulp cell isolation method may affect the distribution of the obtained cell populations, (2) a treated dentin surface might still promote odontoblast differentiation, and (3) a collagen matrix may not be a suitable scaffold for pulp tissue regeneration because of the marked contraction caused by pulp cells in the matrix. The present study thus provides important information and a basis for further investigations pre-requisite to establishing pulp tissue engineering/regeneration protocols.
“…Tooth replantation induces extensive degeneration of almost all odontoblasts 1 day after operation (Nakakura- Ohshima et al 2003), showing that this type is the heavy injury model. Control dental pulp (6 weeks after birth) was composed of three layers: a diVerentiated odontoblast layer, a subodontoblastic layer including a cell-rich zone and the center of the pulp tissue (Fig.…”
Section: Responses Of Lrcs Against Tooth Replantation (Heavy Injury Mmentioning
confidence: 98%
“…The procedures of cavity preparation and tooth replantation induce destructive changes in odontoblasts at the aVected site as well as an acute inXammatory reaction in rat molars (Nakakura- Ohshima et al 2003;Ohshima 1990;Ohshima et al 2003). In these experimental models, pulpal mesenchymal cells take the place of the degenerated odontoblasts to diVerentiate into odontoblastlike cells resulting in the formation of reparative dentin, although the extent of aVected odontoblasts diVers between these diVerent models.…”
Recent studies have demonstrated that human dental pulp contains adult stem cells. A pulse of the thymidine analog BrdU given to young animals at the optimal time could clarify where slow-cycling long-term labelretaining cells (LRCs), putative adult stem cells, reside in the pulp tissue. This study focuses on the mapping of LRCs in growing teeth and their regenerative capacity after tooth injuries. Two to seven peritoneal injections of BrdU into pregnant Wistar rats revealed slow-cycling long-term dense LRCs in the mature tissues of born animals. Numerous dense LRCs were postnatally decreased in number and reached a plateau at 4 weeks after birth when they mainly resided in the center of the dental pulp, associating with blood vessels. Mature dental pulp cells were stained with Hoechst 33342 and sorted into (<0.76%) side population cells using FACS, which included dense LRCs. Some dense LRCs co-expressed mesenchymal stem cell markers such as STRO-1 or CD146. Tooth injuries caused degeneration of the odontoblast layer, and newly diVerentiated odontoblast-like cells contained LRCs. Thus, dense LRCs in Electronic supplementary material The online version of this article (
“…Tooth replantation/transplantation induces at least two types of healing patterns in the replanted teeth: dentin and bone tissue formation in the repaired dental pulp (Byers et al 1992;Hasegawa et al 2007;Kvinnsland et al 1991;Ohshima et al 2001;Rungvechvuttivittaya et al 1998;Shimizu et al 2000;Tsukamoto-Tanaka et al 2006;Unno et al 2009). Our recent studies have demonstrated that the types of cells appearing along the pulp-dentin border play crucial roles in determining the healing patterns in the replanted teeth: once osteoclast lineage cells appear at the pulp-dentin border, bone matrix deposition can be induced (Hasegawa et al 2007;Tsukamoto-Tanaka et al 2006;Unno et al 2009), whereas the temporal appearance of dendritic cells there induces dentin formation (Nakakura- Ohshima et al 2003;Shimizu et al 2000). Thus, the temporal appearance of dendritic cells at the pulp-dentin border is suggestive of a decisive phenomenon to induce the odontoblast differentiation during the pulpal healing process following tooth injuries (Nakakura- Ohshima et al 2003).…”
Dental pulp elaborates both bone and dentin under pathological conditions such as tooth replantation/transplantation. This study aims to clarify the expression of granulocyte macrophage colony-stimulating factor (GM-CSF) and osteopontin (OPN) in the process of reparative dentin formation by allogenic tooth transplantation using in situ hybridization for OPN and immunohistochemistry for GM-CSF and OPN at both levels of light and electron microscopes. Following the extraction of the mouse molar, the roots and pulp floor were resected and immediately allografted into the sublingual region. On days 1 to 3, immunocompetent cells such as macrophages and dendritic cells expressed both GM-CSF and OPN, and some of them were arranged along the pulp-dentin border and extended their cellular processes into the dentinal tubules. On days 5 to 7, tubular dentin formation commenced next to the preexisting dentin at the pulp horn where nestin-positive odontoblast-like cells were arranged. Until day 14, bone-like tissue formation occurred in the pulp chamber, where OPN-positive osteoblasts surrounded the bone matrix. These results suggest that the secretion of GM-CSF and OPN by immunocompetent cells such as macrophages and dendritic cells plays a role in the maturation of dendritic cells and the differentiation of odontoblasts, respectively, in the regenerated pulp tissue following tooth transplantation.
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