Biomedical subjects

Martha J Somerman

Publications and source records attributed to Martha J Somerman.

At least 19 recordsLinked to original sources

PubMed2007

Cyclooxygenase-2-dependent prostaglandin E(2) upregulates interleukin (IL)-1alpha-induced IL-6 generation in mouse cementoblasts.

BACKGROUND: Prostaglandin E(2) (PGE(2)), which exerts its biologic actions via EP receptors (EP(1), EP(2), EP(3,) and EP(4)), is a bioactive metabolite of arachidonic acid that is produced by cyclooxygenase (COX)-1 and/or COX-2. In the present study, we investigated whether a mouse cementoblast cell line, OCCM-30 cells, that was stimulated with interleukin (IL)-1alpha produced COX-2-dependent PGE(2) and whether the produced PGE(2) affected IL-1alpha-induced IL-6 production. METHODS: OCCM-30 cells were stimulated with vehicle or IL-1alpha in the presence or absence of indomethacin (a COX-1/COX-2 inhibitor), NS-398 (a specific COX-2 inhibitor), PGE(2), and EP receptor agonists. PGE(2) and IL-6 levels were assayed by enzyme linked immunosorbent assay. RESULTS: IL-1alpha induced PGE(2) production in a time-dependent fashion. Indomethacin and NS-398 completely inhibited IL-1alpha-induced PGE(2) production. 17-phenyl-omega-trinor PGE(2) (an EP(1) agonist) and an EP(4) agonist mimicked PGE(2) enhancement of IL-1alpha-induced IL-6 production in OCCM-30 cells. CONCLUSIONS: From these data, we suggest that IL-1alpha induced PGE(2) production in a COX-2-dependent manner in OCCM-30 cells and that the COX-2-derived PGE(2) upregulates IL-1alpha-elicited IL-6 production via EP(1) and/or EP(4) receptors. PGE(2) and IL-6 produced by cementoblasts may be involved in the pathogenesis of periodontal disease.

Analysis of Variance↗

PubMed2006

Nano-fibrous scaffolding promotes osteoblast differentiation and biomineralization.

Nano-fibrous poly(L-lactic acid) (PLLA) scaffolds with interconnected pores were developed under the hypothesis that nano-fibrous scaffolding would mimic a morphological function of collagen fibrils to create a more favorable microenvironment for cells versus solid-walled scaffolds. In this study, an in vitro system was used to examine biological properties of the nano-fibrous scaffolds compared with those of solid-walled scaffolds for their potential use in bone tissue engineering. Biomineralization was enhanced substantially on the nano-fibrous scaffolds compared to solid-walled scaffolds, and this was confirmed by von Kossa staining, measurement of calcium contents, and transmission electron microscopy. In support of this finding, osteoblasts cultured on the nano-fibrous scaffolds exhibited higher alkaline phosphatase activity and an earlier and enhanced expression of the osteoblast phenotype versus solid-walled scaffolds. Most notable were the increases in runx2 protein and in bone sialoprotein mRNA in cells cultured on nano-fibrous scaffolds versus solid-walled scaffolds. At the day 1 of culture, alpha2 and beta1 integrins as well as alphav and beta3 integrins were highly expressed on the surface of cells seeded on nano-fibrous scaffolds, and linked to this were higher levels of phospho-Paxillin and phospho-FAK in cell lysates. In contrast, cells seeded on solid-walled scaffolds expressed significantly lower levels of these integrins, phospho-Paxillin, and phospho-FAK. To further examine the role of nano-fibrous architecture, we inhibited the formation of collagen fibrils by adding 3,4-dehydroproline to cultures and then assayed cells for expression of alpha2 integrin. Cells seeded on nano-fibrous scaffolds sustained expression of alpha2 integrin in the presence of dehydroproline, while suppression of alpha2 integrin was evident in cells seeded on solid-walled scaffolds. These results provide initial evidence that synthetic nano fibers may exhibit certain properties that are comparable to natural collagen fibers, and thus, the nano-fibrous architecture may serve as a superior scaffolding versus solid-walled architecture for promoting osteoblast differentiation and biomineralization.

Animals↗

PubMed2006

Amelogenins regulate expression of genes associated with cementoblasts in vitro.

Amelogenins are major proteins expressed by ameloblasts during development of the crown (enamel and dentin). These matrix proteins guide crystal habits of the mineral phase of developing enamel and are possible regulators of other genes/proteins during development and maturation of crown and root (dentin and cementum). This study focused on defining the effect that a specific proteolytic cleavage product of amelogenin, tyrosine-rich amelogenin peptide (TRAP), has on cementoblast behavior. Immortalized cementoblasts (OCCM-30) were exposed to TRAP in vitro. Cells treated with TRAP were evaluated for cell proliferation, gene expression for osteocalcin (OCN), osteopontin (OPN), and bone sialoprotein (BSP), and induction of mineral nodule formation. No significant difference in cell proliferation was found between vehicle-treated cells and those treated with TRAP for up to 9 d after treatment. Gene expression of OCN, OPN, and BSP in TRAP-treated cementoblasts showed down-regulation, up-regulation, and no significant change, respectively, relative to vehicle control. A marked decrease in mineral nodule formation was found in cells treated with TRAP compared with the vehicle control, in a dose-dependent manner. These data, along with our previous results demonstrating similar activity with full-length amelogenin and leucine-rich amelogenin peptide (LRAP), suggest that amelogenin-like molecules regulate mesenchymal cell behavior.

Amelogenin↗

PubMed2006

Bone sialoprotein gene transfer to periodontal ligament cells may not be sufficient to promote mineralization in vitro or in vivo.

BACKGROUND: To improve regenerative therapies, it is important to understand the cells and factors modulating periodontal tissues. Our group has focused on bone sialoprotein (BSP), a mineralized tissue-selective protein considered to be involved in the initiation of cementogenesis and osteogenesis. In this study, we examined whether gene transfer of BSP into periodontal ligament (PDL) cells would result in an increased ability of PDL cells to promote mineralization in vitro and in vivo. METHODS: PDL cells obtained from CD-1 mice were immortalized using simian virus (SV) 40 large T antigen (TAg) and designated SV-PDL cells. SV-PDL cells were infected in vitro with LacZ gene-expressing control adenovirus vector. A 1,000 plaque-forming unit (pfu) titer was selected (based on X-gal staining) and cells were infected with mouse BSP-expressing replication-deficient adenoviral vector to determine the mRNA expression and protein level of BSP. Total RNA was isolated from cells on days 2, 4, and 6. Media were obtained on days 3, 5, and 7 for protein determination. Northern blot analysis was performed for mRNA expression and Western blot analysis for protein expression. To test the effect of BSP gene transfer on the mineralization of PDL cells, in vitro (von Kossa) and in vivo (severe combined immunodeficiency [SCID] mice) experiments were performed. RESULTS: Under normal conditions, PDL cells do not express BSP transcripts and do not promote significant mineralization. SV-PDL cells infected with a BSP viral vector expressed and secreted substantial levels of BSP as confirmed by Northern and Western blot analysis. BSP mRNA and protein levels were strong on day 2 and still apparent on day 6, although not as great. However, no mineral nodule formation was noted either in vitro or in vivo. CONCLUSIONS: Although BSP is an important and necessary protein for mineralization, it may not be sufficient for promoting mineralization without the addition or removal of other factors. Further studies will help to clarify the specific factors required for promoting mineralization, a required step for designing predictable periodontal regenerative therapies.

3T3 Cells↗

PubMed2005

JunB as a downstream mediator of PTHrP actions in cementoblasts.

UNLABELLED: The role of AP-1 family members in the action of PTHrP was examined in cementoblasts. PTHrP increased mRNA and protein levels of all Fos members, but only one Jun member (JunB) was increased. Overexpression of JunB in cementoblasts mimicked actions of PTHrP to support osteoclastogenesis and inhibit cementoblast differentiation, suggesting that the actions of PTHrP on mesenchymal cells operate through JunB. INTRODUCTION: Cementoblasts are mesenchymal cells that share phenotypic features with osteoblasts in vitro; however, unlike osteoblasts, cementoblasts rarely support osteoclastogenesis in vivo. The osteoblast-mediated support of osteoclastogenesis involves PTH-induced reduction in osteoprotegerin (OPG) expression. PTH acts on osteoblastic cells through specific signaling pathways and transcription factors such as activator protein 1 (AP-1). The purpose of this study was to determine the impact of PTH-related protein (PTHrP) on AP-1 transcription factors in cementoblasts and the role of JunB in the actions of PTHrP. MATERIALS AND METHODS: Cementoblastic cells were treated with PTHrP and evaluated for mRNA and protein levels of AP-1 family members. Stable transfectants of OCCM cells overexpressing JunB were evaluated for OPG production, ability to support osteoclastogenesis, and measures of proliferation and differentiation. RESULTS: PTHrP treatment in vitro resulted in a time-dependent upregulation of mRNA and proteins for the Fos family members, but only JunB of the Jun family. OPG mRNA and protein levels were reduced by PTHrP in OCCM and were lower in JunB overexpressing cells than controls. In co-culture experiments, TRACP+ cells were increased with RANKL treatment in JunB overexpressing cells compared with controls. Cementoblast differentiation was reduced with overexpression of JunB as measured by a decrease in mineralized nodule formation and gene expression for bone sialoprotein and osterix. Measures of proliferation including cell number and cyclin D1 levels were increased in JunB overexpressing clones. In vivo, cementoblast implants exhibited a cementoblastoid nature with copious mineral-like matrix, whereas JunB-overexpressing implants were densely cellular with little mineralized matrix. CONCLUSIONS: JunB was the only Jun family member increased by PTHrP, and its overexpression showed similar patterns of gene expression and OPG production as PTHrP treatment of controls. These data suggest that JunB may be a key mediator of PTHrP actions in cementoblasts.

Animals↗

PubMed2005

Bisphosphonate modulates cementoblast behavior in vitro.

BACKGROUND: Cementum formation is deemed to be instrumental for the successful regeneration of periodontal tissues, and thus events and modifiers of cementum formation and mineralization need to be determined. This study aimed to determine whether the bisphosphonate 1-hydroxyethylidene-1,1-bisphosphonate (HEBP) altered the behavior of immortalized cementoblasts (osteocalcin-cementoblasts [OCCM]). METHODS: OCCM from transgenic mice were exposed to HEBP at concentrations ranging from 0.01 to 10.0 microM. The assays performed included the count of cell number for proliferation, Northern blot analysis for gene expression (up to 10 days for core binding factor alpha-1 [Cbfa1], bone sialoprotein [BSP], osteocalcin [OCN], and osteopontin [OPN], markers for cementoblast/osteoblast maturation/mineralization), von Kossa stain and alizarin red S stain for mineralization, and enzyme assay (p-nitrophenol phosphate cleavage) for alkaline phosphatase (ALP) activity. RESULTS: Mineral nodule formation was inhibited at the higher doses of HEBP (1.0 and 10.0 microM) only. At early stages (1, 3, and 6 days), gene expression assays revealed only subtle changes in treated cells versus untreated cells, but by day 10, groups treated with lower doses (0.01 and 0.1 microM) were markedly different at the gene expression level. OCN was significantly downregulated (70%) at the lowest dose, with less pronounced effects at higher doses. In concurrence, the master switch gene for osteoblasts, Cbfa1, was also downregulated at the lower doses. Inversely, OPN mRNA was enhanced at the lower doses. ALP activity was not altered by HEBP. CONCLUSION: Bisphosphonate alters cementoblast function in vitro through the regulation of gene expression and mineral formation.

Alkaline Phosphatase↗

PubMed2005

Periodontal status in two siblings with severe congenital neutropenia: diagnosis and mutational analysis of the cases.

BACKGROUND: Severe congenital neutropenia (SCN), also known as Kostmann syndrome, was originally reported as an autosomal recessive disease of neutrophil production. The disease is characterized by a maturation arrest of neutrophil precursors at the promyelocytic stage of differentiation and by extremely low levels of mature neutrophils in peripheral blood. METHODS: A 6-year-old male presented with a complaint of gingival swelling and bleeding, and swelling at the left side of his face. Upon clinical examination, severe inflammation of all gingival tissues was apparent, and a periapical abscess with mobility was noted on the left mandibular second molar. Medical and dental histories revealed numerous recurrent bacterial infections associated with oral and non-oral tissues. His medical history with recurrent infections led us to evaluate his 3-year-old sister to determine the status of her oral health. Inflammation of her oral tissues and recurrent bacterial infections were apparent. Their consanguineous parents were in good health. To assist in identifying possible systemic diseases underlying the inflammatory situation in the siblings, consultations were requested from the Pediatric Hematology Department at Selcuk University and Pediatric Oncology Department at Gulhane Military Medical Academy. RESULTS: Based on absolute neutrophil count (< or =200/mm(3)) and bone marrow aspiration findings consistent with early maturation arrest in myelopoiesis, the cases were diagnosed as SCN. No chromosomal abnormality was detected upon cytogenetic examination. Sequencing analysis also revealed no mutation in the neutrophil elastase or growth factor independent-1 (GFI-1) genes in these patients. Severe periodontal disease, attachment loss, and mobility for over 50% of the deciduous teeth were noted. Within 6 months, the male sibling lost all of his deciduous teeth due to periapical and periodontal infections. His sister presented with tooth mobility for all mandibular incisors. Monthly visits, including scaling, polishing, and 0.2% chlorhexidine digluconate irrigation were performed to support their oral hygiene and to avoid recurrent oral infections. We have been able to stabilize these patients' periodontal conditions during a 2-year follow-up period. CONCLUSION: This case report emphasizes the role of periodontists and pediatric dentists in the diagnosis of diseases linked with neutrophil and other systemic disorders and highlights the need to optimize the health of oral tissues with regular appointments.

Bacterial Infections↗

PubMed2005

Dexamethasone and basic-fibroblast growth factor regulate markers of mineralization in cementoblasts in vitro.

BACKGROUND: The aim of this study was to determine the effects of basic-fibroblast growth factor (b-FGF) and/or dexamethasone (Dex) on cementoblasts in vitro. METHODS: Murine cementoblasts were treated as follows: 1) 5% FBS (fetal bovine serum) + ascorbic acid (AA, 50 microg/ml, control); 2) 5% FBS + Dex (10(7)M) + AA; 3) 5% FBS + b-FGF (50 ng/ml)+AA; or 4) 5% FBS + Dex (10(7) M) + b-FGF (50 ng/ml)+AA and then evaluated by Northern analysis for changes in specific genes and by von Kossa stain for changes in mineral nodule formation. RESULTS: Mitotic activity: b-FGF stimulated DNA synthesis significantly versus negative control. Gene expression: osteocalcin (OCN): Dex or b-FGF or the combination resulted in a decrease in expression versus control. Bone sialoprotein (BSP): Dex increased expression of BSP mRNA levels, b-FGF decreased transcript for BSP at 6 and 24 hours. Long-term (8 days) Dex, b-FGF, or Dex plus b-FGF caused a decrease in BSP expression versus control; osteopontin (OPN): both Dex and b-FGF increased transcripts for OPN seen by 6 hours, with a greater increase noted with b-FGF versus Dex. No apparent additive effect of Dex with b-FGF was noted; matrix gamma-carboxyglutamic acid protein (MGP): b-FGF induced transcripts for MGP and addition of Dex increased this effect, while Dex alone had no effect on expression. Biomineralization: Dex increased cementoblast- mediated biomineralization, while b-FGF blocked this activity, and addition of Dex to b-FGF did not alter FGF associated inhibition. CONCLUSION: Dex and FGF alone and in combination alter cementoblast behavior, but additional studies are required to determine whether these factors have beneficial effects at the clinical level.

Animals↗

PubMed2005

The crowning achievement: getting to the root of the problem.

An ideal goal of oral-craniofacial dental reconstructive therapy is to establish treatment modalities that predictably restore functional tissues. One major area of focus has been in the area of dental materials with marked improvements in the design of materials used to restore teeth/periodontium/bone lost as a consequence of disease or disorders. With advances in understanding the cell and molecular controls for development and regeneration of tooth structures, it is now possible to consider therapies that promote regeneration of lost tissues, along with replacement of these tissues. This review presents a background on our current knowledge as to the composition of the tooth/periodontium followed by a discussion on successes to date, both in vitro and in vivo, toward regenerating a whole tooth and next steps required to regenerate a functional tooth.

Humans↗

PubMed2004

Cementoblast delivery for periodontal tissue engineering.

BACKGROUND: Predictable periodontal regeneration following periodontal disease is a major goal of therapy. The objective of this proof of concept investigation was to evaluate the ability of cementoblasts and dental follicle cells to promote periodontal regeneration in a rodent periodontal fenestration model. METHODS: The buccal aspect of the distal root of the first mandibular molar was denuded of its periodontal ligament (PDL), cementum, and superficial dentin through a bony window created bilaterally in 12 athymic rats. Treated defects were divided into three groups: 1) carrier alone (PLGA polymer sponges), 2) carrier + follicle cells, and 3) carrier + cementoblasts. Cultured murine primary follicle cells and immortalized cementoblasts were delivered to the defects via biodegradable PLGA polymer sponges, and mandibulae were retrieved 3 weeks and 6 weeks post-surgery for histological evaluation. In situ hybridization, for gene expression of bone sialoprotein (BSP) and osteocalcin (OCN), and histomorphometric analysis were further done on 3-week specimens. RESULTS: Three weeks after surgery, histology of defects treated with carrier alone indicated PLGA particles, fibrous tissue, and newly formed bone scattered within the defect area. Defects treated with carrier + follicle cells had a similar appearance, but with less formation of bone. In contrast, in defects treated with carrier + cementoblasts, mineralized tissues were noted at the healing site with extension toward the root surface, PDL region, and laterally beyond the buccal plate envelope of bone. No PDL-bone fibrous attachment was observed in any of the groups at this point. In situ hybridization showed that the mineralized tissue formed by cementoblasts gave strong signals for both BSP and OCN genes, confirming its nature as cementum or bone. The changes noted at 3 weeks were also observed at 6 weeks. Cementoblast-treated and carrier alone-treated defects exhibited complete bone bridging and PDL formation, whereas follicle cell-treated defects showed minimal evidence of osteogenesis. No new cementum was formed along the root surface in the above two groups. Cementoblast-treated defects were filled with trabeculated mineralized tissue similar to, but more mature, than that seen at 3 weeks. Furthermore, the PDL region was maintained with well-organized collagen fibers connecting the adjacent bone to a thin layer of cementum-like tissue observed on the root surface. Neoplastic changes were observed at the superficial portions of the implants in two of the 6-week cementoblast-treated specimens, possibly due in part to the SV40-transformed nature of the implanted cell line. CONCLUSIONS: This pilot study demonstrates that cementoblasts have a marked ability to induce mineralization in periodontal wounds when delivered via polymer sponges, while implanted dental follicle cells seem to inhibit periodontal healing. These results confirm the selective behaviors of different cell types in vivo and support the role of cementoblasts as a tool to better understand periodontal regeneration and cementogen-

Absorbable Implants↗

PubMed2004

Effect of sustained gene delivery of platelet-derived growth factor or its antagonist (PDGF-1308) on tissue-engineered cementum.

BACKGROUND: Cementum, a mineralized tissue lining the tooth root surface, is destroyed during the inflammatory process of periodontitis. Restoration of functional cementum is considered a criterion for successful regeneration of periodontal tissues, including formation of periodontal ligament, cementum, and alveolar bone. Short-term administration of platelet-derived growth factor (PDGF) has been shown to partially regenerate periodontal structures. Nonetheless, the role of PDGF in cementogenesis is not well understood. The aim of the present study was to determine the effect of sustained PDGF gene transfer on cementum formation in an ex vivo ectopic biomineralization model. METHODS: Osteocalcin (OC) promoter-driven SV40 transgenic mice were used to obtain immortalized cementoblasts (OCCM). The OCCM cells were transduced with adenoviruses (Ad) encoding either PDGF-A, an antagonist of PDGF signaling (PDGF-1308), a control virus (green fluorescent protein, GFP), or no treatment (NT). The transduced cells were incorporated into polymer scaffolds and implanted subcutaneously into severe combined immunodeficient (SCID) mice. The implants were harvested at 3 and 6 weeks for histomorphometric analysis of the newly formed mineralized tissues. Northern blot analysis was performed to determine the expression levels of mineral-associated genes including bone sialoprotein (BSP), OC, and osteopontin (OPN) in the cell-implant specimens at 3 and 6 weeks. RESULTS: The results indicated mineralization was significantly reduced in both the Ad/PDGF-A and Ad/PDGF-1308 treated specimens when compared to the NT or Ad/GFP groups at 3 and 6 weeks (P<0.01). In addition, the size of the implants treated with Ad/PDGF-A and Ad/PDGF-1308 was significantly reduced compared to implants from Ad/GFP and NT groups at 3 weeks (P<0.05). At 6 weeks, the size of implants and mineral formation increased in NT, Ad/GFP, and Ad/PDGF-A groups, while the Ad/PDGF-1308 treated implants continued to decrease in size and mineral formation (P<0.01). Northern blot analysis revealed that in the Ad/PDGF-A treated implants OPN was increased, whereas OC gene expression was downregulated at 3 weeks. In the Ad/PDGF-1308 treated implants, BSP, OC, and OPN were all downregulated at 3 weeks. At 3 weeks, the Ad/PDGF-A treated implants contained significantly higher multinucleated giant cell (MNGC) density compared to NT, Ad/GFP, and Ad/PDGF-1308 specimens. The MNGC density in NT, Ad/GFP, and Ad/PDGF-A treated groups reduced over time, while the Ad/PDGF-1308 transduced implants continued to exhibit significantly higher MNGC density compared with the other treatment groups at 6 weeks. CONCLUSIONS: The results showed that continuous exposure to PDGF-A had an inhibitory effect on cementogenesis, possibly via the upregulation of OPN and subsequent enhancement of MNGCs at 3 weeks. On the other hand, Ad/PDGF-1308 inhibited mineralization of tissue-engineered cementum possibly due to the observed downregulation of BSP and OC and a persistence of stimulation of MNGCs. These findings suggest that continuous exogenous delivery of PDGF-A may delay mineral formation induced by cementoblasts, while PDGF is clearly required for mineral neogenesis.

Animals↗

PubMed2004

Leucine-rich amelogenin peptide: a candidate signaling molecule during cementogenesis.

BACKGROUND: Cementum is a critical mineralized tissue; however, control of its formation remains undefined. One hypothesis is that enamel matrix proteins/peptides secreted by ameloblasts and/or epithelial rest cells contribute to the control of cementum formation via epithelial-mesenchymal interactions. Here, we focused on determining whether or not leucine-rich amelogenin peptide (LRAP), translated from an alternatively spliced amelogenin RNA, altered cementoblast behavior. METHODS: Immortalized murine cementoblasts (OCCM-30) were exposed to LRAP and evaluated for: 1) proliferative activity; 2) gene expression using Northern blot for Cbfal (core binding factor alpha-1); OCN (osteocalcin), OPN (osteopontin), and real-time reverse transcription-polymerase chain reaction (RT-PCR) for OPG (osteoprotegerin); and RANKL (receptor activator of NF-kappaB ligand); 3) signaling pathway using inhibitors of PKA (THFA), PKC (GF109203X), and MAPK (UO126); and 4) mineralization evaluated by von Kossa and Alizarin-red. RESULTS: LRAP had no effect on cell proliferation up to 6 days, with a decrease in cell growth observed at the highest dose by 9 days versus untreated cells. LRAP down regulated OCN and up regulated OPN in a dose- and time-response fashion, and inhibited the capacity of mineral nodule formation. Transcripts for OPG were increased in LRAP-treated cells compared to control, but RANKL mRNA levels were not affected. Core binding factor alpha (Cbfa) mRNA, expressed constitutively, was not affected by LRAP. Signaling pathway assays suggested involvement of the MAPK pathway, since the addition of the MAPK inhibitor suppressed OPN expression in LRAP-treated cells. CONCLUSION: Leucine-rich amelogenin peptide appears to have a direct effect on cementoblast activity that may prove significant during development as well as in regeneration of periodontal tissues.

Animals↗

PubMed2004

The role of parathyroid hormone-related protein in the regulation of osteoclastogenesis by cementoblasts.

BACKGROUND: Parathyroid hormone-related protein (PTHrP) promotes osteoclastogenesis by inhibiting expression of osteoprotegerin (OPG), a decoy receptor for the receptor activator of nuclear factor kappa B (RANK), and by enhancing production of RANK ligand (RANKL) by osteoblasts. However, little is known regarding the role of PTHrP in regulating cementoblast-mediated osteoclastogenesis. METHODS: This study determined the impact of PTHrP on osteoclastogenesis using: 1) OCCM-30 (immortalized murine cementoblasts), 2) RAW 264.7 cells (murine myeloid cells), or 3) OCCM-30 plus RAW 264.7 cells. Cells were treated with PTHrP (1-34), RANKL, or PTHrP and RANKL combined. Enzyme-linked immunosorbent assays (ELISAs) for OPG and RANKL were performed on media and cell lysates, and tartrate-resistant acid phosphatase (TRAP) and mRNA detection for the osteoclast associated receptor (OSCAR) were performed. RESULTS: The highest numbers of TRAP-positive cells and cells expressing OSCAR were found in the RAW cell group treated with either RANKL alone or RANKL and PTHrP. TRAP-positive cells were fewer when OCCM cells were co-cultured with RAW, but the greatest numbers were still with both PTHrP and RANKL. OPG levels were highest from OCCM cells and PTHrP decreased these levels. In contrast, RANKL levels were low in OCCM cell lysates and PTHrP increased RANKL. In vivo studies also revealed high osteoclastic activity surrounding developing teeth in mice administered PTH. CONCLUSIONS: These results demonstrate that PTHrP influences the balance of OPG and RANKL production by cementoblasts, and further indicate that this effect, in the context of surrounding cells, might have a significant impact on osteoclastogenesis, root resorption, and tooth eruption.

Acid Phosphatase↗

PubMed2003

Cementoblasts maintain expression of osteocalcin in the presence of mineral trioxide aggregate.

This study investigated the effects of mineral trioxide aggregate on cementoblast growth and osteocalcin production in tissue culture. For cellular morphology studies, cementoblasts on mineral trioxide aggregate, IRM, and amalgam were incubated for 48 h then fixed for scanning electron microscopic analysis. For gene expression on mineral trioxide aggregate and IRM, reverse transcriptase polymerase chain reaction was performed using primer sets for glyceraldehyde-3-phosphate dehydrogenase, type I collagen, alkaline phosphatase, osteocalcin, and bone sialoprotein after 3 and 5 days. In vitro matrix protein expression was evaluated by confocal microscopy for the presence of osteocalcin on MTA after 7 and 12 days. Images were compared with controls to assess qualitative differences. Results suggest that mineral trioxide aggregate permits cementoblast attachment and growth and the production of mineralized matrix gene and protein expression. Our data indicates that mineral trioxide aggregate can be considered cementoconductive.

Alkaline Phosphatase↗

PubMed2003

Growth and amelogenin-like factors in periodontal wound healing. A systematic review.

BACKGROUND: Regeneration of tooth-supporting structures destroyed by periodontitis is a major goal of periodontal therapy. Periodontal tissue engineering utilizing growth and amelogenin-like factors (GAFs) applies advances in materials science and biology to regenerate alveolar bone, periodontal ligament, and cementum. Amelogenin-like factors (e.g., enamel matrix derivative [EMD]) and growth factors (e.g., platelet-derived growth factor [PDGF] and bone morphogenetic proteins [BMPs, also considered morphogens]) have demonstrated pleotrophic effects on the stimulation of several key events required for tissue regeneration including DNA synthesis, chemotaxis, differentiation, and matrix synthesis. RATIONALE: GAFs have been used for the treatment of periodontal disease as shown in preclinical and clinical studies. This systematic review evaluates the evidence to support the utilization of EMD and growth factors (GFs) for periodontal repair and regeneration associated with natural teeth. FOCUSED QUESTION: In patients with periodontal osseous defects, what is the effect of GAFs compared with controls on clinical, radiographic, histologic, adverse, and patient-centered outcomes? SEARCH PROTOCOL: Two investigators searched MEDLINE, pre-MEDLINE, and the Cochrane Oral Health Group trials register for clinical and preclinical studies published in English. Hand searches were performed on the International Journal of Periodontics and Restorative Dentistry, Journal of Clinical Periodontology, Journal of Dental Research, Journal of Periodontology, and Journal of Periodontal Research. Searches were performed for articles published through April 2002. In addition, investigators contacted manufacturers of GAF products for related unpublished data and studies in progress. SELECTION CRITERIA INCLUSION CRITERIA: Randomized controlled clinical trials (RCTs), cohort studies, case-control studies, case reports, and preclinical (animal) randomized controlled investigations that included a cohort population diagnosed with periodontal disease and presenting data on intrabony/interproximal defects and/or furcation defects were screened. EXCLUSION CRITERIA: In vitro studies or those that did not include quantifiable data with respect to clinical or bone measures were not included. DATA COLLECTION AND ANALYSIS: Meta-analyses were performed for studies that fulfilled the eligibility criteria for the following continuous variables: clinical attachment level (CAL), probing depth (PD), or bone level (radiographic, re-entry, or histologic). Heterogeneity was assessed to determine whether the differences among therapies were due to systematic confounding factors (as noted in study quality assessments). MAIN RESULTS: 1. Eight studies, representing 7 RCTs and 1 quasi-experimental study, representing a total population of 511 subjects were analyzed with respect to EMD. 2. The majority of the remaining papers had a low evidence rating. 3. Most reports were case studies or case series without controls. 4. There were insufficient data to conduct a meta-analysis on the effect of growth factors used in periodontal repair around teeth. REVIEWERS' CONCLUSIONS: 1. There is evidence supporting the use of EMD for periodontal osseous defects to improve CAL and reduce PD, although long-term benefits have not been established. 2. EMD has demonstrated notable consistency among the studies investigated in terms of superiority to controls (in general compared to open flap debridement [OFD]). 3. EMD appears to be safe for single and multiple administrations in terms of lack of elicitation of antibody responses or other local/systemic inflammatory events. 4. Preclinical and initial clinical data for growth factors appear promising but are insufficient to draw definitive conclusions at this time.

Alveolar Bone Loss↗

PubMed2003

Amelogenin: a potential regulator of cementum-associated genes.

BACKGROUND: Studies suggest that enamel matrix proteins induce differentiation and mineralization of a variety of mesenchymal cells, including odontoblasts, osteoblasts, and cementoblasts. It has been postulated that this activity could be due to amelogenin-like proteins, known to be present in some mixtures of enamel matrix derivatives. Amelogenins have been reported to induce expression of a mineralized tissue-specific marker, bone sialoprotein (BSP), indicating that epithelial products can regulate the activity of mesenchyme-derived cells. METHODS: To explore the molecular mechanisms involved in BSP regulation, a clonal population of immortalized murine cementoblasts (OCCM-30) was exposed to full-length murine amelogenin protein (rp(H)M180), 0.1 microg/ml to 10.0 microg/ml, for 8 days in vitro. To further investigate the potential epithelial-mesenchymal interaction, an amelogenin knockout mouse model was used to examine expression of BSP and other markers, including Type I collagen, in tissue samples. RESULTS: The lowest dose of amelogenin slightly enhanced BSP expression, whereas at the highest dose, a dramatic decrease (three-fold) in BSP expression was observed. Parallel experiments showed a corresponding decrease in mineral nodule formation in vitro for cells treated with the higher dose of rp(H)M180. In situ hybridization and immunohistochemical analysis of sections from amelogenin null mice revealed a dramatic reduction in expression of BSP mRNA and protein in cementoblasts and surrounding osteoblasts in comparison to age-matched controls. In contrast, the expression of Type I collagen was not significantly different from controls. CONCLUSION: These data suggest that amelogenin may be a critical signaling molecule required for appropriate development of the periodontium.

Amelogenin↗

PubMed2003

Exploring the origins of cementoblasts and their trigger factors.

Future directions for designing periodontal regenerative therapies hinge on characterization of cells associated with periodontal tissues and on signals instrumental in regulating their behavior. Studies here focused on determining the responsiveness of putative cementoblast progenitor cells (follicle cells), periodontal ligament cells, and cementoblasts to specific factors. Cementoblasts (OCCM), periodontal ligament (SVPDL) cells, and follicle cells (SVF4) were isolated from mouse tissues and immortalized, where SV indicates the use of SV-40 for immortalization. Cultured cells were examined for response to parathyroid hormone-related protein (PTHrP), bone morphogenetic protein-2 (BMP-2), and enamel matrix derivative (EMD) using RT-PCR, Northern analysis, and in vitro and in vivo mineralization assays. Results showed that the three cell lines varied in their expression of bone sialoprotein (BSP) and osteocalcin (OCN), and in their capacity to promote mineralization. RT-PCR indicated that all cell lines had PTH/PTHrP-R1 and BMP receptors; however, the response of individual cell lines to PTHrP, BMP-2, and EMD was quite different. Such dissimilarities in responsiveness associated with cell type may need to be considered when designing regenerative therapies.

Animals↗

PubMed2003

Addressing disparities through dental-medical collaborations, part 1. The role of cultural competency in health disparities: training of primary care medical practitioners in children's oral health.

This paper introduces a series of articles examining specific dental-medical educational collaborations intended to decrease oral health disparities. The first article discusses cultural competency and its relationship to oral health disparities. The next two articles present pediatric oral health educational programs for medical practitioners, one targeting primary care practitioners and the other training family practice residents. This introductory article reviews the national public health agenda for oral health, explains the rationale for targeting dental-medical educational collaborations to address health disparities, and identifies important gaps in dental as well as medical education, especially in the area of infant oral health. Key findings of the two projects are reviewed as well as lessons learned. We call for leadership in dental education in three critical areas: cultural competency, infant oral health, and ethical and professional values. Given the historical isolation of dentistry, strong leadership at the level of the dean's office is needed to advance the agenda of eliminating oral health disparities through collaborations among dentistry, medicine, and the other health professions. Finally, an appreciation of the professional obligations of dental educators, practitioners, and the profession of dentistry can add resolve to this new prioritization.

Child↗