Biomedical subjects

M J Somerman

Publications and source records attributed to M J Somerman.

At least 19 recordsLinked to original sources

PubMed2006

Regulation of cementoblast gene expression by inorganic phosphate in vitro.

Examination of mutant and knockout phenotypes with altered phosphate/pyrophosphate distribution has demonstrated that cementum, the mineralized tissue that sheathes the tooth root, is very sensitive to local levels of phosphate and pyrophosphate. The aim of this study was to examine the potential regulation of cementoblast cell behavior by inorganic phosphate (P(i)). Immortalized murine cementoblasts were treated with P(i) in vitro, and effects on gene expression (by quantitative real-time reverse-transcriptase polymerase chain reaction [RT-PCR]) and cell proliferation (by hemacytometer count) were observed. Dose-response (0.1-10 mM) and time-course (1-48 hours) assays were performed, as well as studies including the Na-P(i) uptake inhibitor phosphonoformic acid. Real-time RT-PCR indicated regulation by phosphate of several genes associated with differentiation/mineralization. A dose of 5 mM P(i) upregulated genes including the SIBLING family genes osteopontin (Opn, >300% of control) and dentin matrix protein-1 (Dmp-1, >3,000% of control). Another SIBLING family member, bone sialoprotein (Bsp), was downregulated, as were osteocalcin (Ocn) and type I collagen (Col1). Time-course experiments indicated that these genes responded within 6-24 hours. Time-course experiments also indicated rapid regulation (by 6 hours) of genes concerned with phosphate/pyrophosphate homeostasis, including the mouse progressive ankylosis gene (Ank), plasma cell membrane glycoprotein-1 (Pc-1), tissue nonspecific alkaline phosphatase (Tnap), and the Pit1 Na-P(i) cotransporter. Phosphate effects on cementoblasts were further shown to be uptake-dependent and proliferation-independent. These data suggest regulation by phosphate of multiple genes in cementoblasts in vitro. During formation, phosphate and pyrophosphate may be important regulators of cementoblast functions including maturation and regulation of matrix mineralization.

Animals↗

PubMed2006

Extracellular phosphate alters cementoblast gene expression.

Genetic data from humans and mice reveal that the formation of cementum is sensitive to intra- and extracellular phosphate/pyrophosphate distribution. The intracellular molecular pathways whereby altered levels of extracellular phosphate concentration may affect cementum formation have not been elucidated. To initiate inquiry, we have studied the temporal effects of extracellular phosphate on global patterns of gene expression in a line of immortalized mouse cementoblasts. Total RNA from cultured cementoblasts treated with 5 mM inorganic phosphate over a designated time period, from 1-48 hrs, was analyzed for global patterns of gene expression by means of DNA microarrays representing the complete mouse genome. Analyses of significant hybridization signals indicated that 5 mM extracellular phosphate alters the expression of genes comprising several gene ontology (GO) groups, including transcription factor activity and Wnt signaling.

Animals↗

PubMed2006

Regulation of cementoblast function by P. gingivalis lipopolysaccharide via TLR2.

Although cementoblasts express Toll-like receptors (TLR)-2 and -4, little is known regarding the possible participation of cementoblasts in the inflammatory response. We investigated the effects of Porphyromonas gingivalis lipopolysaccharide (LPS), tetra- and penta-acylated lipid A species (designated PgLPS(1435/1449) and PgLPS(1690), respectively), on gene expression of osteoclastogenesis-associated molecules in murine cementoblasts. Real-time quantitative RT-PCR analysis revealed that receptor activator of NF-kappaB ligand (RANKL), interleukin-6, Regulated on activation, normal T-cell expressed, and secreted (RANTES), macrophage inflammatory protein-1alpha, and monocyte chemoattractant protein-1 were rapidly and dramatically induced upon stimulation with PgLPS(1690), but only slightly induced with PgLPS(1435/1449). Osteoprotegerin, which was expressed constitutively, was not altered significantly. ELISA demonstrated synthesis of corresponding proteins. PgLPS(1690) significantly induced transcripts for NF-kappaB, and this activation was inhibited by pre-treatment with anti-TLR-2 but not with TLR-4 antibodies. These results suggest that cementoblasts participate in the recruitment of osteoclastic precursor cells by up-regulation of chemokines/cytokines.

Analysis of Variance↗

PubMed2006

Effects of endogenous and exogenous prostaglandin E2 on the proliferation and differentiation of a mouse cementoblast cell line (OCCM-30).

BACKGROUND: Cementum formation is considered to be a critical event for successful regeneration of periodontal tissues. Cementoblasts share many characteristics with osteoblasts. Prostaglandin E(2) (PGE(2)) is an important local factor in bone metabolism. Although the effects of PGE(2) on osteoblasts are well known, its effects on cementoblasts have not yet been established. We examined the effects of PGE(2) on proliferation and differentiation in a mouse cementoblast cell line, OCCM-30 cells. METHODS: OCCM-30 cells were treated with three concentrations of PGE(2) (10, 100, and 1,000 ng/ml). Cell number, alkaline phosphatase (ALP) activity, and expression for mineralization-related genes were determined. Osteoprotegerin (OPG) and receptor activator of nuclear factor-kappa B (NF-kappaB) ligand (RANKL) expression were also examined by real-time polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay (ELISA). RESULTS: The addition of PGE(2) at the highest dose used in this study suppressed cell proliferation of OCCM-30 cells. The expression of mineralization-related marker mRNA, such as type 1 collagen, ALP, bone sialoprotein (BSP), and osteocalcin (OCN), was constitutively detected in OCCM-30 cells. PGE(2) dose dependently stimulated ALP activity and BSP-mRNA expression in OCCM-30 cells at day 3. Transcripts for OPG and RANKL and the protein level of OPG in culture media were upregulated with PGE(2) stimulation. CONCLUSION: These results demonstrate that PGE(2) suppressed cementoblast proliferation but stimulated ALP activity and the BSP-mRNA level, suggesting a role of PGE(2) in controlling cementoblast differentiation, and further indicate that PGE(2) modulates RANKL and OPG expression in cementoblasts; the increase of OPG secreted from cementoblasts with PGE(2) stimulation may be essential to protect the root surface from resorption.

Alkaline Phosphatase↗

PubMed2005

Regenerating the periodontium: is there a magic formula?

OBJECTIVE: Left untreated, periodontal disease results in destruction of periodontal tissues including cementum, bone and the periodontal ligament, and subsequently, tooth loss. Increased research efforts focused on understanding periodontal disease at the cellular, molecular and clinical level have resulted in improved modalities for arresting disease progression; however, outcomes of existing procedures are not predictable and often disappointing. Critical to improving the predictability of regenerative therapies is targeting studies toward enhancing our understanding of the cellular and molecular events required to restore periodontal tissues. DESIGN: Toward this goal our laboratory has focused on defining cells, mechanisms and factors regulating development of periodontal tissues, using in vitro and in vivo rodent models. RESULTS AND CONCLUSION: Results from these studies have enabled us to identify attractive candidate factors/cells including: 1) products secreted by epithelial cells that act on mesenchymal cells (amelogenins): we observed that both follicle cells and cementoblasts are responsive to amelogenin-like molecules resulting in changes in the expression of genes associated with cell maturation; 2) morphogens (bone morphogenetic proteins, BMP): we report that follicle cells respond differently to BMPs vs. cementoblasts, depending on dose of and specific BMP used; 3) phosphates: existing data suggest that phosphates act as signaling molecules regulating the expression of genes associated with cementoblast maturation. Knowledge gained from these studies has provided insight as to the cells/factors required for designing improved regenerative therapies.

Amelogenin↗

PubMed2005

Defining the roots of cementum formation.

Significant progress has been seen in research aimed at regeneration of the disease-damaged periodontium. Our own strategy has been to approach periodontal tissue development (i.e. root, cementum, periodontal ligament, and bone) as a source for the identification of key regulators of cellular processes that may be applicable to periodontal tissue repair. Specifically, enamel-like molecules, bone morphogenetic proteins (BMPs), and phosphates have been investigated for their role in altering gene expression and cell functions in follicle cells, periodontal ligament cells, and cementoblasts. Amelogenin, leucine-rich amelogenin peptide, and tyrosine-rich amelogenin peptide have been found to similarly affect cementoblast gene expression and cementoblast-mediated mineralization in vitro; however, these enamel-like factors do not increase cell proliferation as has been observed in cells treated with Emdogain (Biora AB, Malmö, Sweden), an enamel matrix derivative. BMP-2 has been found to promote differentiation of follicle cells into a cementoblast/osteoblast phenotype, and BMP-3 is being investigated as a negative regulator of mineralization. The increased ratio of phosphate to pyrophosphate in the local region during root development has been found to significantly enhance the extent of cementum formation in animal models. Furthermore, phosphate has been identified as a regulator of cementoblast SIBLING (small integrin-binding ligand N-linked glycoprotein) gene expression in vitro. These investigations of candidate factors for periodontal regeneration have uncovered mechanisms regulating gene expression and cell function in cells controlling the behavior of periodontal tissues (i.e. follicle cells, periodontal cells, and cementoblasts) and offer new directions to consider for clinical repair of periodontal defects.

Animals↗

PubMed2004

Noggin gene delivery inhibits cementoblast-induced mineralization.

Bone morphogenetic proteins (BMPs) are known to promote periodontal tissue regeneration, while noggin inhibits the biological activities of BMP-2, -4, and -7. To investigate the effect of BMPs and noggin gene transfer on cementogenesis, we used cloned murine cementoblasts (OCCM). Cells were transduced using adenoviruses encoding BMP-7 (Ad-BMP-7), noggin devoid of the heparin binding site (Ad-NOGDeltaB2), or a control adenovirus encoding green fluorescent protein (Ad-GFP). Cells were seeded into 3D polymer scaffolds and implanted into SCID mice to determine the in vivo mineral-inducing ability of the cells. Cells transduced with Ad-NOGDeltaB2 at 3 and 6 weeks postimplantation exhibited reduced mineral formation compared with all other groups. Although gene expression of osteocalcin and bone sialoprotein increased after Ad-BMP-7 transduction in vitro, following BMP-7 gene transfer in vivo, transcripts for OCN and BSP were not significantly different from controls, and mineral density was not significantly increased compared with Ad-GFP and NT groups. These results indicate that in mature cementoblast populations, gene transfer of noggin inhibits biomineralization induced by cementoblasts, whereas exogenous BMP has minimal effects on mineralization.

Animals↗

PubMed2004

Cementoblast gene expression is regulated by Porphyromonas gingivalis lipopolysaccharide partially via toll-like receptor-4/MD-2.

Lipopolysaccharides are potent inflammatory mediators considered to contribute to destruction of periodontal tissues. Here, we hypothesized that Porphyromonas gingivalis lipopolysaccharide (P-LPS) treatment would regulate gene expression in murine cementoblasts through Toll-like receptor 4. Real-time (RT)-PCR and Northern blot analysis indicated that P-LPS decreased expression of transcripts for osteocalcin (OCN) and receptor activator of nuclear factor kappaB ligand (RANKL). In contrast, a dose-dependent up-regulation in mRNA levels for osteopontin (OPN) and osteoprotegerin (OPG) was observed. Similarly, ELISA demonstrated decreased RANKL and increased OPG levels. A monoclonal antibody specific for mouse TLR-4/MD-2 partially neutralized the P-LPS effect on cementoblasts. These results indicate that exposure of cementoblasts to P-LPS can alter cell function by regulating markers of osteoclastic activity (e.g., RANKL/OPG), thereby potentially affecting the inflammation-associated resorption of mineralized tissues.

Animals↗

PubMed2003

Cementum engineering with three-dimensional polymer scaffolds.

Cloned cementoblasts (OCCMs), periodontal ligament fibroblasts (SV-PDLs), and dental follicle (SV-F) cells obtained from mice were used as a tool to study periodontal tissue engineering. OCCM, SV-PDL, and SV-F cells were seeded onto three-dimensional poly lactic-co-glycolic acid (PLGA) scaffolds and cultured with the use of bioreactors or implanted subcutaneously in severe combined immune deficiency (SCID) mice for up to 6 weeks. We explored the behavior of these cells in porous PLGA sponges by cell growth, expression of mineral-associated genes using reverse transcriptase polymerase chain reaction, and mineralization by histologic analysis in vitro and in vivo. Results indicated that cells attached to PLGA scaffolds under either static or dynamic conditions in vitro. Only OCCM implants, retrieved from both in vitro bioreactors and SCID mice at 3-and 6-weeks post-cell implantation exhibited mineral formation. Types I and XII collagens, osteocalcin, and bone sialoprotein genes were detected in all implants retrieved from SCID mice. These results suggest that delivery of selected cells via PLGA scaffolds may serve as a viable approach for promoting periodontal tissue regeneration.

Animals↗

PubMed2003

Bone morphogenetic protein-2 inhibits differentiation and mineralization of cementoblasts in vitro.

As an approach for improving the outcome and predictability of periodontal regenerative therapies, we have focused on determining the responses of cells within the local environment to putative regenerative factors. This study examined the effects of bone morphogenetic protein-2 (BMP-2) on murine cementoblasts in vitro. Northern blot analysis indicated that BMP-2 decreased mRNA levels of bone sialoprotein and type I collagen dose-dependently (10-300 ng/mL). At low doses, up to 100 ng/mL, BMP-2 had no effect on transcripts for osteocalcin and osteopontin, whereas at 300 ng/mL, BMP-2 greatly increased expression of these two genes. BMP-2 also inhibited cementoblast-mediated mineral nodule formation in a dose-dependent manner (inhibition was noted at 10 ng/mL). Noggin reversed the effects of BMP-2 on gene expression and on mineralization. These findings reflect the diverse responses of periodontal cells to BMP-2 and highlight the need to consider the complexity of factors involved in designing predictable regenerative therapies.

Animals↗

PubMed2003

Parathyroid hormone protects against periodontitis-associated bone loss.

Parathyroid hormone (PTH) functions as a major mediator of bone remodeling and as an essential regulator of calcium homeostasis. In addition to the well-established catabolic effects (activation of bone resorption) of PTH, it is now recognized that intermittent PTH administration has anabolic effects (promotion of bone formation). The aim of this study was to investigate whether intermittent administration of PTH in rodents would block the alveolar bone loss observed in rats when a ligature model of periodontitis is used. Morphometric analysis showed that intermittent PTH administration (40 microg/kg) was able to protect the tooth site from periodontitis-induced bone resorption. In addition, there was a significant reduction in the number of inflammatory cells at the marginal gingival area in sections obtained from animals receiving PTH compared with control animals. These findings demonstrated that intermittent PTH administration was able to protect against periodontitis-associated bone loss in a rodent model.

Alveolar Bone Loss↗

PubMed2002

Cementum: a phosphate-sensitive tissue.

Ectopic calcification within joints has been reported in humans and rodents exhibiting mutations in genes that regulate the level of extracellular pyrophosphate, e.g., ank and PC-1; however, periodontal effects of these mutations have not previously been examined. These initial studies using ank and PC-1 mutant mice were done to see if such mineral deposition and resulting ankylosis were occurring in the periodontium as well. Surprisingly, results indicated the absence of ankylosis; however, a marked increase in cementum formation on the root surfaces of fully developed teeth of these mutant mice was noted. Examination of ank mutant mice at earlier ages of tooth root formation indicated that this striking observation is apparent from the onset of cementogenesis. These findings suggest that cells within the periodontal region are highly responsive to changes in phosphate metabolism. This information may prove valuable in attempts to design successful therapies for regenerating periodontal tissues.

Animals↗

PubMed2001

TGFbeta and BMP-2 activation of the OPN promoter: roles of smad- and hox-binding elements.

Members of the transforming growth factor superfamily are known to transduce signals via the activation of Smad proteins. Ligand binding to transmembrane cell surface receptors triggers the phosphorylation of pathway-specific Smads. These Smads then complex with Smad 4 and are translocated to the nucleus where they effect gene transcription. Smads 1 and 4 were recently demonstrated to mediate BMP activation of the OPN promoter by inhibiting the interaction of Hoxc-8 protein with a Hox-binding element. While previous studies have indicated that specific DNA sequences are recognized by Smad complexes in several promoters, the role of Smad-binding elements (SBEs) in activation of the OPN promoter by members of the TGFbeta superfamily has not been previously evaluated. In this study we tested the hypothesis that a putative Smad-binding region containing the sequence AGACTGTCTGGAC is involved in the activation of the OPN promoter by members of the TGFbeta superfamily. Functional analyses demonstrated that the both the HBE- and Smad-binding region were involved in BMP-2-induced activation of the promoter, whereas, the HBE appeared to be the primary region involved in activation by TGFbeta. Deletion of the first 9 bases in the Smad-binding region substantially reduced BMP-2-mediated activation of the promoter. These results strongly suggest that both the Hox- and the Smad-binding regions play a role in BMP-2-induced activation of the OPN promoter.

3T3 Cells↗

PubMed2001

"Come on in".

Explore the source record for details and available documents.

Humans↗

PubMed2001

Matrix gamma-carboxyglutamic acid protein is a key regulator of PTH-mediated inhibition of mineralization in MC3T3-E1 osteoblast-like cells.

As part of its overall function as a major regulator of calcium homeostasis, PTH stimulates bone resorption and inhibits osteoblast-mediated biomineralization. To determine the basis for the inhibitory actions of this hormone, we compared the time course of PTH-dependent inhibition of mineralization in MC3T3-E1 osteoblast-like cells with changes in mRNA levels for several extracellular matrix proteins previously associated either with induction or inhibition of mineralization. Mineralizing activity was rapidly lost in PTH-treated cells ( approximately 30% inhibition after 3 h, 50% inhibition at 6 h). Of the proteins examined, changes in matrix gamma-carboxyglutamic acid protein were best correlated with PTH-dependent inhibition of mineralization. Matrix gamma-carboxyglutamic acid protein mRNA was rapidly induced 3 h after PTH treatment, with a 6- to 8-fold induction seen after 6 h. Local in vivo injection of PTH over the calvaria of mice also induced a 2-fold increase in matrix gamma-carboxyglutamic acid protein mRNA. Warfarin, an inhibitor of matrix gamma-carboxyglutamic acid protein gamma-carboxylation, reversed the effects of PTH on mineralization in MC3T3-E1 cells, whereas vitamin K enhanced PTH activity, as would be expected if a gamma-carboxyglutamic acid-containing protein were required for PTH activity. Levels of the other mRNAs examined were not well correlated with the observed changes in mineralization. Osteopontin, an in vitro inhibitor of mineralization, was induced approximately 4-fold 12 h after PTH addition. Bone sialoprotein mRNA, which encodes an extracellular matrix component most frequently associated with mineral induction, was inhibited by 50% after 12 h of PTH treatment. Osteocalcin mRNA, encoding the other known gamma-carboxyglutamic acid protein in bone, was also inhibited by PTH, but, again, with a significantly slower time course than was seen for mineral inhibition. Taken together, these results show that the rapid inhibition of osteoblast mineralization induced by in vitro PTH treatment is at least in part explained by induction of matrix gamma-carboxyglutamic acid protein.

1-Carboxyglutamic Acid↗

PubMed2001

An economic evaluation of a chlorhexidine chip for treating chronic periodontitis: the CHIP (chlorhexidine in periodontitis) study.

BACKGROUND: The authors previously suggested that an adjunctive, controlled-release chlorhexidine, or CHX, chip may reduce periodontal surgical needs at little additional cost. This article presents an economic analysis of the CHX chip in general dental practice. METHODS: In a one-year prospective clinical trial, 484 chronic periodontitis patients in 52 general practices across the United States were treated with either scaling and root planing, or SRP, plus any therapy prescribed by treating, unblinded dentists; or SRP plus other therapy as above but including the CHX chip. Economic data were collected from bills, case report forms and 12-month treatment recommendations from blinded periodontist evaluators. RESULTS: Total dental charges were higher for SRP + CHX chip patients vs. SRP patients when CHX chip costs were included (P = .027) but lower when CHX chip costs were excluded (P = .012). About one-half of the CHX chip acquisition cost was offset by savings in other charges. SRP + CHX chip patients were about 50 percent less likely to undergo surgical procedures than were SRP patients (P = .021). At the end of the trial, periodontist evaluators recommended similar additional procedures for both groups: SRP, about 46 percent; maintenance, about 37 percent; surgery, 56 percent for SRP alone and 63 percent for SRP + CHX chip. CONCLUSIONS: Adjunctive CHX chip use for general-practice patients with periodontitis increased costs but reduced surgeries over one year. At study's end, periodontists recommended similar additional surgical treatment for both groups. CLINICAL IMPLICATIONS: In general practice, routine use of the CHX chip suggests that costs will be partially offset by reduced surgery over at least one year.

Adult↗

PubMed2001

The effect of enamel matrix protein derivative on follicle cells in vitro.

BACKGROUND: It is thought that during development of the periodontium, dental follicle cells, when appropriately triggered, have the ability to differentiate into periodontal ligament fibroblasts, cementoblasts, and osteoblasts. However, the exact mechanisms/factors responsible for initiating cell differentiation are not defined. The purpose of this in vitro study was to further characterize follicle cells and to determine the effects of an enamel matrix-derived protein (EMD) on these cells. METHODS: Murine follicle cells, transformed with simian virus 40 (SV 40) T antigen-containing virus (SVF cells), were used. SVF cells were cultured in Dulbecco's modified Eagle's medium (DMEM) plus 2% fetal bovine serum (FBS) or 2% FBS plus EMD (100 microg/ml), with and without ascorbic acid (50 microg/ml). For proliferation assays, cells were plated at 500 cells/cm2 in 24-well plates and counted on days 3, 4, and 5. For Northern analysis, total RNA was isolated on days 8, 12, and 18. Induction of mineral nodules by SVF cells was determined by von Kossa staining. RESULTS: EMD had a significant proliferative effect on SVF cells, when compared with 2% FBS control. Based on investigations in situ, follicle cells at the time point used here do not express key mineral-associated markers, e.g., osteocalcin (OCN) or bone sialoprotein (BSP). Significantly, by day 12 in culture, Northern analysis indicated that the follicle cells expressed transcripts for BSP, OCN, and osteopontin (OPN). EMD increased OPN mRNA and decreased OCN mRNA expression. SVF cells were capable of inducing mineralization on day 18, but EMD blocked this activity. CONCLUSIONS: These results suggest the follicle cells have the capacity to act as cementoblasts or osteoblasts. Furthermore, EMD can regulate follicle cell activity, thus suggesting that epithelial-mesenchymal interactions may be important during development of periodontal tissues.

Analysis of Variance↗

PubMed2000

Bone morphogenetic proteins secreted by breast cancer cells upregulate bone sialoprotein expression in preosteoblast cells.

It is well established that bone metastases comprise bone; however, the exact factors/mechanisms involved remain unknown. We hypothesized that tumor cells secreted factors capable of altering normal bone metabolism. The aims of the present study were to (1) determine the effects of secretory products isolated from HT-39 cells, a human breast cancer cell line, on osteoprogenitor cell (MC3T3-E1 cells) behavior, and (2) identify tumor-derived factor(s) that alters osteoblast activities. Conditioned media (CM) from HT-39 cells were collected following a 24-h serum-free culture. The ability of CM to alter gene expression in MC3T3-E1 cells was determined by Northern analysis. CM effects on cell proliferation and mineralization ability were determined using a Coulter counter and von Kossa stain, respectively. MC3T3-E1 cells were treated with CM plus noggin, a factor known to block bone morphogenic proteins (BMPs), to determine whether BMPs, shown to be present in CM, were linked with CM effects on MC3T3-E1 cell activity. In addition, inhibitors of MAP kinase kinase (MEK), protein kinase C (PKC), and protein kinase A were used to identify the intracellular signaling pathway(s) by which the active factors in CM regulated osteoblast behavior. CM treatment significantly enhanced BSP mRNA (2.5-fold over control), but had no effect on cell proliferation. Mineralization assay showed that CM enhanced mineral nodule formation compared to controls. Noggin inhibited CM-induced upregulation of BSP mRNA, suggesting that BMPs were responsible for upregulating BSP gene expression in MC3T3-E1 cells. The PKC inhibitor blocked CM-mediated upregulation of BSP, suggesting involvement of the PKC pathway in regulating BSP expression. BMPs secreted by HT-39 cells may be responsible for enhancing BSP expression in MC3T3-E1 cells. Continued studies targeted at determining the role of BMPs in regulating bone metabolism are important for understanding the pathogenesis of bone diseases.

3T3 Cells↗