Biomedical subjects

G E Wise

Publications and source records attributed to G E Wise.

At least 19 recordsLinked to original sources

PubMed2005

Chronology and regulation of gene expression of RANKL in the rat dental follicle.

Tooth eruption in the rat requires bone resorption resulting from a major burst of osteoclastogenesis on postnatal day 3 and a minor burst of osteoclastogenesis on postnatal day 10 in the alveolar bone of the first mandibular molar. The dental follicle regulates the major burst on postnatal day 3 by down-regulating its osteoprotegerin (OPG) gene expression to enable osteoclastogenesis to occur. To determine the role of receptor activator of nuclear factor-kappa B ligand (RANKL) in tooth eruption, its gene expression was measured on postnatal days 1-11 in the dental follicle. The results show that RANKL expression was significantly elevated on postnatal days 9-11 in comparison to low expression levels at earlier time-points. As OPG expression is high at this latter time-point, this increase in RANKL expression would be needed for stimulating the minor burst of osteoclastogenesis. Tumor necrosis factor-alpha enhances RANKL gene expression in vitro and it may be responsible for up-regulating RANKL in vivo. Transforming growth factor-beta1 and interleukin-1alpha also enhance RANKL gene expression in vitro but probably have no effect in vivo because they are maximally expressed early. Bone morphogenetic protein-2 acts to down-regulate RANKL expression in vitro and, in vivo, may promote alveolar bone growth in the basal region of the tooth.

Alveolar Process↗

PubMed2005

CSF-1 regulation of osteoclastogenesis for tooth eruption.

The dental follicle regulates the alveolar bone resorption needed for tooth eruption. In the rat first mandibular molar, a decrease in the expression of osteoprotegerin (OPG) in the dental follicle at day 3 enables the osteoclastogenesis needed for eruption to occur. Because colony-stimulating factor-1 (CSF-1) is maximally expressed in the dental follicle at day 3, it was hypothesized that CSF-1 down-regulates OPG gene expression in the dental follicle in vivo. To test this, we compared the expression of OPG in osteopetrotic toothless (tl/tl) rats deficient in CSF-1 with expression in their normal littermates for given ages. OPG gene expression was found to be higher in the dental follicle of the tl/tl mutants than in normals. Transfecting short interfering RNA specific for CSF-1 mRNA into dental follicle cells resulted in an up-regulation of OPG expression. Thus, these studies support our hypothesis that the down-regulation of OPG needed for tooth eruption is mediated by CSF-1.

Animals↗

PubMed2004

Regulation of secretion of osteoprotegerin in rat dental follicle cells.

Tooth eruption requires alveolar bone resorption and formation, both of which appear to be regulated by the dental follicle. Osteoclastogenesis needed for this bone resorption appears to occur as a result of a reduction in the expression of the osteoprotegerin (OPG) gene in the dental follicle at a specific time. This reduction in expression is mediated in vitro in the follicle cells by colony-stimulating factor-1 (CSF-1) and parathyroid hormone-related protein (PTHrP). Using enzyme-linked immunosorbent assays and immunoblotting, this study shows that the reduction in expression of OPG after incubation of the dental follicle cells in either CSF-1 or PTHrP also results in a reduction in its secretion. We also show, by laser capture microdissection, that PTHrP is expressed in vivo in the stellate reticulum such that it could inhibit OPG expression via a paracrine effect on the follicle. Bone formation is enhanced by OPG secretion, and incubation of the follicle cells with bone morphogenetic protein-2 (BMP-2) enhances OPG secretion. Thus, a reduction in secretion of the OPG protein at defined times may promote the osteoclastogenesis and alveolar bone resorption needed for eruption, and enhancement of OPG secretion at other times may promote alveolar bone formation.

Animals↗

PubMed2003

Regulation of osteoprotegerin gene expression in dental follicle cells.

Colony-stimulating factor-one (CSF-1) and parathyroid-hormone-related protein (PTHrP) down-regulate osteoprotegerin (OPG) gene expression in the dental follicle of the rat first mandibular molar. To examine this regulation at the signal transduction level, we treated cultured dental follicle cells with either phorbolmyristate acetate (PMA) or dibutyryl cyclic AMP (dbcAMP) to activate either protein kinase C (PKC) or protein kinase A (PKA). Our results demonstrate that PMA up-regulates OPG gene expression and down-regulates the expression of CSF-1 and the PTHrP receptor (PTHrP-R). Conversely, dbcAMP down-regulates OPG expression and up-regulates CSF-1 and PTHrP-R expression. Immunostaining shows that PMA also increases the steady-state levels of protein. Thus, treatment with agents that affect protein kinase activity also enhance the steady-state mRNA and protein levels of OPG, as well as decreasing the mRNA levels of CSF-1 and PTHrP-R. The PKC-alpha isoform may be critical in OPG regulation because PKC-alpha gene expression is enhanced by PMA and reduced by either CSF-1 or PTHrP.

Animals↗

PubMed2003

Expression of vascular endothelial growth factor in the dental follicle.

Tooth eruption requires the presence of the dental follicle to recruit mononuclear cells, which fuse to form osteoclasts that resorb the alveolar bone such that the tooth can erupt. In the rat first mandibular molar, there is a major burst of osteoclastogenesis at day 3 postnatally and a lesser burst at day 10. Eruption molecules, such as CSF-1, are maximally expressed at day 3 in the dental follicle to promote this maximal osteoclast formation, but by the time of the secondary burst of osteoclastogenesis their expression is dramatically reduced. Because vascular endothelial growth factor (VEGF) can substitute for CSF-1 to promote osteoclastogenesis, we examined its gene expression in vivo in the dental follicle and found that it and its two major isoforms (VEGF 120 and 164) were all maximally expressed at days 9-11, the time of the secondary burst. Treatment of the cells with phorbolmyristate acetate (PMA), a protein kinase C (PKC) activator, enhanced expression of the 2 major VEGF isoforms in the cultured dental follicle cells, whereas adding a specific PKC inhibitor prevented this. Treatment with PMA also increased the protein level of VEGF. Thus, VEGF may be involved in promoting the secondary burst of osteoclastogenesis, and activation of PKC may upregulate its expression.

Animals↗

PubMed2002

Cellular, molecular, and genetic determinants of tooth eruption.

Tooth eruption is a complex and tightly regulated process that involves cells of the tooth organ and the surrounding alveolus. Mononuclear cells (osteoclast precursors) must be recruited into the dental follicle prior to the onset of eruption. These cells, in turn, fuse to form osteoclasts that resorb alveolar bone, forming an eruption pathway for the tooth to exit its bony crypt. Some of the molecules possibly involved in the signaling cascades of eruption have been proposed in studies from null mice, osteopetrotic rodents, injections of putative eruption molecules, and cultured dental follicle cells. In particular, recruitment of the mononuclear cells to the follicle may require colony-stimulating factor-one (CSF-1) and/or monocyte chemotactic protein-1 (MCP-1). Osteoclastogenesis is needed for the bone resorption and may involve inhibition of osteoprotegerin transcription and synthesis in the follicle, as well as enhancement of receptor activator of NF kappa B ligand (RANKL), in the adjacent alveolar bone and/or in the follicle. Paracrine signaling by parathyroid-hormone-related protein and interleukin -1 alpha, produced in the stellate reticulum adjacent to the follicle, may also play a role in regulating eruption. Osteoblasts might also influence the process of eruption, the most important physiologic role likely being at the eruptive site, in the formation of osteoclasts through signaling via the RANKL/OPG pathway. Evidence thus far supports a role for an osteoblast-specific transcription factor, Cbfa1 (Runx2), in molecular events that regulate tooth eruption. Cbfa1 is also expressed at high levels by the dental follicle cells. This review concludes with a discussion of the several human conditions that result in a failure of or delay in tooth eruption.

Animals↗

PubMed2001

Effects of dexamethasone on tooth eruption in rats: differences in incisor and molar eruption.

A requirement for tooth eruption is the resorption of alveolar bone. Because bone resorption is stimulated by dexamethasone both in vivo and in vitro, dexamethasone 21-phosphate, a soluble form of dexamethasone, was injected into rats to determine its effect on tooth eruption. Such dexamethasone injections accelerate the time of intra-osseous eruption in rat incisors but do not accelerate the eruption time of rat molars when injected into rats. The injections of dexamethasone 21-phosphate also accelerate the time of eyelid opening in the postnatal rats, as well as retarding growth, as measured by body weight. These effects of dexamethasone 21-phosphate parallel the effects of epidermal growth factor injections, including the absence of an effect on molar eruption. This suggests that the molecular signals for the initiation of tooth eruption (i.e., onset of bone resorption) differ between rat incisors and molars. Given that rat incisors are teeth of continuous eruption whereas rat molars are teeth of limited eruption, as are human teeth, care must be taken in extrapolating results derived from rat incisors to human dentition. In vitro, dexamethasone has no effect on the gene expression of either osteoprotegerin or epidermal growth factor in dental follicle cells derived from molars. Because osteoprotegerin expression during normal tooth eruption is transitorily inhibited early postnatally in the molar dental follicle to allow osteoclast formation, the absence of inhibition of its expression by dexamethasone could explain why dexamethasone does not accelerate eruption in molars.

Animals↗

PubMed2000

Enhancement of gene expression in rat dental follicle cells by parathyroid hormone-related protein.

Recent studies indicate that parathyroid hormone-related protein (PTHrP) is required for tooth eruption in mice. Localized in the stellate reticulum, PTHrP might exert a paracrine effect on cells of the adjacent dental follicle to initiate eruption. The presence of a follicle is needed for eruption and, at the cellular level, there is an influx of mononuclear cells in the follicle early postnatally in the first mandibular molar of the rat. In turn, these mononuclear cells fuse to form osteoclasts, which erode the alveolar bone to form an eruption pathway. At the molecular level, the dental follicle cells of the rat molar maximally express the genes for monocyte chemotactic protein-1 (MCP-1) and colony-stimulating factor-1 (CSF-1) at day 3 postnatally. Because day 3 also is the time of maximal influx of the mononuclear cells into the follicle, MCP-1 and CSF-1 could be involved in the recruitment/maturation of these cells. To determine if PTHrP can modulate gene expression in the dental follicle, cultured follicle cells were immunostained to show the receptor for PTHrP. The gene expression of this receptor was enhanced by incubating the cells with interleukin-1alpha (IL-1alpha). Next, the ability of PTHrP itself to enhance gene expression of either MCP-1 or CSF-1 in the dental follicle cells was determined by incubating the cells with PTHrP in either a time- or concentration-course manner (1-15 h or 1-100 ng/ml). By reverse transcription-polymerase chain reaction, it was demonstrated that PTHrP enhanced MCP-1 expression in a concentration-dependent fashion, with 50 ng PTHrP/ml inducing maximal expression of either MCP-1 or CSF-1. In the time-dependent studies, PTHrP caused maximal expression within 30 min for either MCP-1 or CSF-1. Immunoblotting revealed that PTHrP also enhanced secretion of MCP-1 by the follicle cells. Thus, one of the actions of PTHrP in tooth eruption may be that it enhances MCP-1 and CSF-1 gene expression and secretion in the dental follicle. Moreover, IL-1alpha may accentuate its action by enhancing the expression for the PTHrP receptor in the follicle cells.

Animals↗

PubMed2000

Delay of tooth eruption in null mice devoid of the type I IL-1R gene.

Interleukin-one alpha (IL-1alpha) is located in the stellate reticulum and its receptor, type I IL-1R (IL-1R), is present in the adjacent dental follicle. IL-1alpha may play a role in initiating tooth eruption because of its ability to enhance the gene expression in the dental follicle of putative tooth eruption molecules colony-stimulating factor-one (CSF-1). monocyte chemotactic protein-1 (MCP-1), and nuclear factor kappa B (NFkappa-B). To directly examine the effect of IL-1alpha and IL-1R on tooth eruption, we observed the times of tooth eruption in null mice devoid of the type I IL-1R gene. The results showed that the time of eruption in the null mice was delayed by 2 d for the first mandibular molar and 1 d for incisors as compared to wild type controls. Reverse transcription-polymerase chain reaction (RT-PCR) techniques confirmed the absence of the IL-1R gene in the null mice, but the genes for CSF-1 and NFkappaB were still expressed. Thus, a molecule(s) other than IL-1alpha also may enhance the expression of CSF- and NFkappaB in the dental follicle. Because there is a slight delay of tooth eruption in IL-1R null mice, IL-1alpha may normally play a role in eruption. However, eruption eventually can occur without the signaling from IL-1alpha.

Animals↗

PubMed2000

Osteoprotegerin and osteoclast differentiation factor in tooth eruption.

A critical cellular event in tooth eruption is the formation of osteoclasts that are needed for bone resorption to form an eruption pathway. To analyze molecular regulation of osteoclast formation and activation, we examined the expression of osteoprotegerin (OPG), an inhibitor of osteoclast formation. In vivo, the gene expression of OPG is reduced in the dental follicle of the first mandibular molar of the rat at day 3 post-natally and in the mouse at day 5. This correlates with the days of maximal mononuclear cell influx and osteoclast numbers in the rat and mouse. Thus, inhibition of OPG gene expression on these days might allow osteoclasts to be formed and/or activated. In vitro studies demonstrated that both colony-stimulating factor-1 and parathyroid hormone-related protein reduced OPG gene expression in follicle cells, suggesting that these are candidate molecules for the in vivo inhibition of OPG expression. Osteoclast differentiation factor (ODF) immunolocalizes to the alveolar bone stromal cells adjacent to the follicle, whereby it might act to stimulate fusion of the mononuclear cells in the follicle.

Alveolar Process↗

PubMed1999

Implications for tooth eruption of the effect of interleukin-1alpha on nuclear factor-kappaB gene expression in the rat dental follicle.

Tooth eruption is a localized event and a cascade of molecular signals generated in the dental follicle and stellate reticulum appears to initiate its onset. Consequently, mononuclear cells are recruited into the follicle and, in turn, fuse to become osteoclasts needed to resorb the alveolar bone to form an eruption pathway. One of the transcription factors involved in the sequence of molecular signalling may be nuclear factor (NF)kappaB. This study shows that NFkappaB is expressed and synthesized by cultured dental follicle cells. Moreover, its transcription, activation and translocation were enhanced by interleukin (IL)-1alpha, a potential eruption molecule. The enhancement of transcription of the NFkappaB gene by IL-1alpha was blocked by a tyrosine-specific kinase inhibitor, suggesting that the enhancement may require the phosphorylation of the NFkappaB complex. In vivo, NFkappaB is maximally expressed in the dental follicle of the rat first mandibular molar at day 3 postnatally, the age at which there is a peak influx of mononuclear cells into the follicle. Thus, a transcription factor apparently required for eruption (NFkappaB) is present in the tissue required for eruption, the dental follicle, and its gene expression is maximal at a critical time in eruption.

Age Factors↗

PubMed1999

Gene expression of potential tooth eruption molecules in the dental follicle of the mouse.

Tooth eruption requires alveolar bone resorption and the presence of the dental follicle, a loose connective tissue sac that surrounds each tooth. This bone resorption involves the follicle in that mononuclear cells enter the follicle to form osteoclasts which resorb bone to form the eruption pathway. In the rat first mandibular molar, probable eruption genes, CSF-1, c-fos, NFkappaB and MCP-1, are expressed maximally in the dental follicle at day 3 postnatally. This correlates with the time of peak influx of mononuclear cells into the follicle. In the mouse, the first peak influx of mononuclear cells into the first mandibular molar is at day 5 postnatally, and this study demonstrates that all four of the above resorption molecules are maximally expressed at this time in the dental follicle. Thus, this work suggests that these molecules may play a role in the cellular events of eruption (mononuclear cell influx and osteoclast formation) in the mouse molar at day 5 postnatally just as they do at day 3 in the rat molar. These results provide a standard for future studies on eruption in the mouse molar and extends the number of species in which putative eruption molecules are expressed at a critical time of eruption.

Animals↗

PubMed1999

Synthesis and secretion of MCP-1 by dental follicle cells--implications for tooth eruption.

The monocyte chemotactic protein-1 (MCP-1) gene is expressed in the dental follicle, a loose connective tissue sac that must be present for eruption to occur. The role of MCP-1 may be to recruit mononuclear cells (monocytes) to the dental follicle, where these cells, in turn, fuse to form osteoclasts to resorb alveolar bone for the formation of an eruption pathway. Thus, it was the aim of this study to determine if MCP-1 is secreted by dental follicle cells in culture and if its secretion is enhanced by potential tooth eruption molecules. Western blotting and a two-site capture enzyme-linked immunoabsorbent assay demonstrated that MCP-1 was synthesized and secreted into the medium by the follicle cells. Incubation of the cells with either transforming growth factor-beta one (TGF-beta 1) or interleukin-one alpha (IL-1 alpha) enhanced the secretion of MCP-1 by the cells. Measurement of the chemotactic ability of the conditioned medium to attract mouse monocytes demonstrated that the chemotaxis of the medium was increased if the cells had previously been incubated in IL-1 alpha, although there appears to be a threshold concentration of MCP-1 above which chemotaxis is not enhanced. These combined results suggest that the critical initial cellular event of tooth eruption, an influx of mononuclear cells into the dental follicle at an early post-natal age, may be initiated by the secretion of MCP-1 by the dental follicle cells.

Animals↗

PubMed1998

Tooth eruption molecules enhance MCP-1 gene expression in the dental follicle of the rat.

Tooth eruption is a localized developmental event that requires the presence of the dental follicle, a loose connective tissue sac that surrounds each tooth. Early postnatally in the first mandibular molar of the rat there is an influx into the follicle of mononuclear cells (monocytes) which, in turn, fuse to form osteoclasts that resorb the bone to form an eruption pathway. The chemoattractant that may attract the mononuclear cells to the follicle to initiate the cellular events of eruption is monocyte chemotactic protein-one (MCP-1). MCP-1 is secreted by the dental follicle cells and its gene is expressed maximally at an early postnatal age, correlating with the monocyte influx into the follicle. In this study, we show that other potential tooth eruption molecules--EGF, IL-1alpha, TGF-beta1 and CSF-1--all enhance the expression of the MCP-1 gene in the cultured dental follicle cells. In vivo, injections of IL-1alpha or EGF also enhance the gene expression of MCP-1 in the follicle with maximal enhancement occurring in the early postnatal days. Thus, there appears to be a redundant function of the different tooth eruption genes to ensure that the MCP-1 gene is expressed. In turn, expression of MCP-1 may be critical for recruiting the monocytes to the dental follicle to initiate the cellular events of tooth eruption.

Animals↗

PubMed1998

In vivo effect of interleukin-1 alpha on colony-stimulating factor-1 gene expression in the dental follicle of the rat molar.

Interleukin-1 alpha (IL-1 alpha) acts in vitro to enhance the gene expression of colony-stimulating factor-1 (CSF-1) of dental follicle cells. Because the dental follicle is required for tooth eruption and because CSF-1 appears to be a key molecule in initiating eruption, it was the aim of this study to determine if IL-1 alpha could enhance the expression of the CSF-1 gene in the dental follicle in vivo. To determine this, rats were injected with IL-1 alpha at different ages postnatally and the total RNA was isolated from the dental follicles of the first mandibular molars. Reverse transcription-polymerase chain reaction showed that IL-1 alpha enhanced the expression of CSF-1 in the follicle. Thus, IL-1 alpha may play a part in the cascade of molecular signals that initiate eruption by its effect upon the CSF-1 gene.

Animals↗

PubMed1998

Secretion of CSF-1 and its inhibition in rat dental follicle cells: implications for tooth eruption.

Tooth eruption requires the presence of a dental follicle around the unerupted tooth. Before the onset of eruption there is an influx of mononuclear cells into the follicle which, in turn, form osteoclasts that erode the alveolar bone. Eruption can be accelerated by the injection of colony-stimulating factor-one (CSF-1), a molecule that is maximally transcribed and translated in the dental follicle cells at the time of peak influx of mononuclear cells into the follicle of the rat first mandibular molar. To determine if the rat dental follicle cells secrete the CSF-1 needed for these cellular events, conditioned medium was collected from cultures of these cells. Using as a bioassay, a cell line (m-NFS 60) that is responsive to CSF-1 for growth, it was shown that conditioned medium from the follicle cells stimulated growth of the m-NFS 60 cells by almost 33% over the controls. Western blots confirmed that CSF-1 was secreted into the medium. Treating the dental follicle cells with an antisense oligodeoxynucleotide probe against CSF-1 reduced the amount of CSF-1 produced. These results demonstrate that CSF-1 is secreted by the dental follicle cells and that the production of CSF-1 can be reduced with an antisense probe. This secretion by the dental follicle might recruit mononuclear cells into the follicle to initiate tooth eruption.

Alveolar Process↗

PubMed1998

Effect of CSF-1 on in vivo expression of c-fos in the dental follicle during tooth eruption.

It has been demonstrated that both colony-stimulating factor-one (CSF-1) and the transcription factor, c-fos are required for tooth eruption. Osteopetrotic mutant rats deficient in CSF-1 activity have unerupted teeth which can be induced to erupt by injections of CSF-1, and osteopetrotic mice deficient in c-fos, have unerupted teeth. Both CSF-1 and c-fos are expressed and translated in the dental follicle, the tissue that is required for eruption. Recent in vitro studies indicate that CSF-1 can enhance the expression of the c-fos gene in cultured dental follicle cells, but the effects in vivo are not known. In the present studies. postnatal rats were injected with 10(6) units of CSF-1 at different ages from birth to day 10 and sacrificed 30 min after injection. Isolation of total RNA from the follicle and reverse transcription PCR showed that CSF-1 injection enhanced the expression of c-fos over the non-injected controls. Chronologically, day 3 postnatally appeared to show the greatest increase of c-fos mRNA following CSF-1 injection. These results suggest that one of the functions of CSF-1 in tooth eruption is to enhance the early expression of c-fos. In turn, c-fos might act to promote fusion of monocytes into the osteoclasts needed for alveolar bone resorption and tooth eruption.

Animals↗

PubMed1998

Inhibition of tooth eruption in the rat by a bisphosphonate.

Studies of osteopetrotic rodents suggest that localized alveolar bone resorption must occur if the tooth is to erupt. To test this hypothesis directly, we injected postnatal rats with pamidronate, a bisphosphonate that reduces bone resorption by osteoclasts. The results of these experiments demonstrate that this bisphosphonate inhibits the time of tooth eruption of both rat molars and incisors. Pamidronate does not inhibit the gene expression of the putative tooth eruption molecules, colony-stimulating factor-1 and c-fos, both of which are expressed in the dental follicle, the tissue that is required for eruption to occur. Pamidronate does increase the size of the osteoclasts, including an increase in the number of nuclei, suggesting that the precursor mononuclear cells can still fuse to form osteoclasts despite the reduced ability of the osteoclasts to resorb bone. Thus, we report the discovery of an agent that inhibits tooth eruption and also show that tooth eruption requires alveolar bone resorption.

Acid Phosphatase↗