The lipophilic vitamin C derivative, 6-o-palmitoylascorbate, protects human lymphocytes, preferentially over ascorbate, against X-ray-induced DNA damage, lipid peroxidation, and protein carbonylation.

The aim of this study was to investigate protective effects of the lipophilic vitamin C derivative, 6-o-palmitoylascorbate (PlmtVC), against X-ray radiation-induced damages including cell death, DNA double-strand breaks (DSBs), lipid peroxidation, and protein carbonylation in human lymphocytes HEV0082, and the stability of PlmtVC under cell-cultured or cell-free condition. Irradiation with X-ray (1.5 Gy) diminished the cell viability and induced apoptosis, both of which were protected by pre-irradiational administration with PlmtVC.

Cementogenic potential of multipotential mesenchymal stem cells purified from the human periodontal ligament.

The periodontal ligament (PDL) consists of a group of specialized connective tissue fibers embedded in the alveolar bone and cementum that are believed to contain progenitors for mineralized tissue-forming cell lineages. These progenitors may contribute to regenerative cell therapy or tissue engineering methods aimed at recovery of tissue formation and functions lost in periodontal degenerative changes. Some reports using immortal clonal cell lines of cementoblasts, which are cells containing mineralized tissue-forming cell lineages, have shown that their phenotypic alteration and gene expression are associated with mineralization.

Human dental mesenchymal stem cells and neural regeneration.

Nerve tissue presents inherent difficulties for its effective regeneration. Stem cell transplantation is considered an auspicious treatment for neuronal injuries. Recently, human dental mesenchymal stem cells (DMSCs) have received extensive attention in the field of regenerative medicine due to their accessibility and multipotency.

Characterization of human dental pulp cells-derived spheroids in serum-free medium: stem cells in the core.

Spheroid models have led to an increased understanding of differentiation, tissue organization and homeostasis. In the present study, we have observed that under a serum-free medium, human dental pulp cells (DPCs) spontaneously formed spheroids, and could survive over 15 weeks. To characterize these spheroids, we investigated their dynamics, microenvironment, cell distribution, molecular profiles, and neuronal/osteogenic potential.

Expression status of mRNA for sex hormone receptors in human dental pulp cells and the response to sex hormones in the cells.

Objectives: Sex hormone receptors are reported to be present in human dental pulp (HDP) cells. The purpose of this study was to examine the biological significance of oestrogen and androgen receptors (ER and AR, respectively) in HDP cells.

Design: We isolated HDP cells expressing ER- and AR-mRNAs and investigated the expression status of the receptors and the response to sex hormones in the cells.

Three-dimensional epithelial and mesenchymal cell co-cultures form early tooth epithelium invagination-like structures: expression patterns of relevant molecules.

Epithelium invagination is the key feature of early tooth development. In this study, we built a three-dimensional (3D) model to represent epithelium invagination-like structure by tissue engineering. Human normal oral epithelial cells (OECs) and dental pulp stem cells (DPSCs) were co-cultivated for 2-7 weeks on matrigel or collagen gel to form epithelial and mesenchymal tissues.

Sensitivity of human dental pulp cells to eighteen chemical agents used for endodontic treatments in dentistry.

To determine the adverse effects against human dental pulp tissue, the sensitivity of human dental pulp cells (D824 cells) to 18 chemical agents used for endodontic treatments in dentistry was examined. The cytotoxicity, as determined by a decrease in colony-forming ability of cells treated with the chemical agents, increased as the concentration increased. As a quantitative measure of the cytotoxic effect, LC(50), the concentration which induces a 50% lethality, was extrapolated from the concentration-response curves.

Cytotoxic effect of eugenol on the expression of molecular markers related to the osteogenic differentiation of human dental pulp cells.

The cytotoxic effect of eugenol on the expression of molecular markers related to the osteogenic differentiation of human dental pulp cells such as collagen synthesis and the expression of two osteogenesis-related genes, alkaline phosphatase (ALP) and bone sialoprotein (BSP), was studied using human dental pulp cells (D824 cells). Cellular growth and survival were decreased by treatment of cells with eugenol in a concentration-dependent manner. The incorporation rate of [(3)H] proline into the acid-insoluble fraction and the synthesis of type I-V collagens were also reduced by treatment of cells with eugenol in a concentration-dependent fashion.

Possible involvement of loss of imprinting in immortalization of human fibroblasts.

Disruption of the normal pattern of parental origin-specific gene expression is referred to as loss of imprinting (LOI), which is common in various cancers. To investigate a possible role of LOI in the early stage of human cell transformation, we studied LOI in 18 human fibroblast cell lines immortalized spontaneously, by viral oncogenes, by chemical or physical carcinogens, or by infection with a retrovirus vector encoding the human telomerase catalytic subunit, hTERT cDNA. LOI was observed in all the 18 immortal cell lines.

Induction of mRNA expression of osteogenesis-related genes by guaiacol in human dental pulp cells.

To investigate the stimulating effect of endodontic medications on the mRNA expression of some osteogenesis-related genes associated with reparative dentinogenesis and hard-tissue formation, human dental pulp cells (D824 cells) were treated with calcium hydroxide (Ca (OH)(2)), formocresol, or guaiacol. The effect on growth was determined by growth curves of D824 cells treated for 1-3 days with 0.03-0.

Immortalization of normal human gingival keratinocytes and cytological and cytogenetic characterization of the cells.

Most in vitro studies of oral carcinogenesis in human cells are carried out with oral keratinocytes immortalized by human papillomavirus type 16 DNA. However, because various etiological factors for oral cancer are known, it is important to establish new human keratinocyte cell lines useful for studying the mechanism of oral carcinogenesis. Normal human gingival keratinocytes in secondary cultures grown in serum-free medium were either transfected with origin (-) SV40 DNA or sequentially transfected with origin (-) SV40 DNA and human c-fos.

Changes in expression of imprinted genes following treatment of human cancer cell lines with non-mutagenic or mutagenic carcinogens.

It remains possible that chemicals that act by mutagenic mechanisms as well as chemicals that do not induce gene mutations may affect epigenetic gene expression. To test the possibility, we investigated the ability of both types of chemicals to alter the expression of five imprinted genes, PEG3, SNRPN, NDN, ZAC and H19, using two human colon cancer cell lines and a human breast cancer cell line. The expression of imprinted genes was changed by some non-mutagenic and mutagenic carcinogens independent of their mutagenic activity.

Clastogenic activity of seven endodontic medications used in dental practice in human dental pulp cells.

Numerous and varied chemical agents are used for endodontic treatments in dental practice. Endodontic medications are administered directly to the teeth in relatively high concentrations and chemical agents applied to enamel or dentin can penetrate the dental pulp tissue and circulate through the body in the bloodstream. In the present study, to assess safety regarding mutagenicity, we investigated the ability of seven endodontic medications to induce chromosome aberrations in human dental pulp cells.

Ability of root canal antiseptics used in dental practice to induce chromosome aberrations in human dental pulp cells.

Root canal antiseptics are topically applied to root canals within the pulpless teeth to treat the root canal and periapical infections. Because the antiseptics that are applied to root canals can penetrate through dentin or leak out through an apical foramen into the periodontium and distribute by the systemic circulation, it is important to study the safety of these antiseptics. In the present study, we examined the ability to induce chromosome aberrations in human dental pulp cells of five root canal antiseptics, namely, carbol camphor (CC), camphorated p-monochlorophenol (CMCP), formocresol (FC), calcium hydroxide, and iodoform which are most commonly used in dental practice.

Assessment using human dental pulp cells of clastogenicity of antiseptics used in dental practice and agents for root canal enlargement and cleaning.

Numerous and varied chemical agents are used as topically applied drugs in dental practice. As they are administered directly to the oral cavity, it is important to study the safety of these agents. In the present study, to assess safety regarding mutagenicity, we investigated the abilities of six antiseptics to induce chromosome aberrations in human dental pulp cells.

Effects of a catechol-O-methyltransferase inhibitor on catechol estrogen-induced cellular transformation, chromosome aberrations and apoptosis in Syrian hamster embryo cells.

To examine a possible mechanism of endogenous estrogen-induced carcinogenesis, we studied the effect of the catechol-O-methyltransferase (COMT) inhibitor Ro 41-0960 on cell transforming and clastogenic activities of 2 catechol estrogens 2- and 4-hydroxyestrone (2- or 4-OHE1) using Syrian hamster embryo (SHE) cells. COMT activity was assayed by determining the methylation of 2- or 4-OHE1 using gas chromatography. The production of 2-methoxyestrone in cultures treated with 2-OHE1 was approximately 2-fold that of 4-methoxyestrone in cultures treated with 4-OHE1.

In vitro chromosome aberration tests using human dental pulp cells to detect the carcinogenic potential of chemical agents.

To examine if human dental pulp cells are useful for assessing the carcinogenic potential of chemical agents, we cultured human dental pulp cells from adults and studied the ability of chemical agents known to be carcinogenic to induce chromosome aberrations in these cells. We confirmed that human dental pulp cells in primary or secondary cultures had the capability of accumulating calcium in vitro as detected by Alizarin red staining and generating dentin-like tissue in immunocompromised mice. These phenotypes were maintained even in cells at seven passages.

Effects of minocycline and doxycycline on cell survival and gene expression in human gingival and periodontal ligament cells.

Objectives And Background: Periodontitis is an infectious disease in the gingival crevice caused by periodontopathic bacteria, including Porphyromonas gingivalis, Prevotella intermedia, Actinobacillus actinomycetemcomitans, and Tennerella forsythensis, and antibacterial agents are directly administered to the site of infection to treat it. To maximize the therapeutic effects while reducing the adverse effects, the antibacterial agents should be administered at concentrations greater than their MIC(90) doses required to inhibit the growth of 90% of periodontopathic bacteria and the administration should not damage the periodontal tissue. One approach for estimating cellular damage in the periodontal tissue caused by the administration is to assay cytological damages following exposures of cultured human cells derived from periodontal tissues to antibacterial agents.

Assessment of genotoxicity of 14 chemical agents used in dental practice: ability to induce chromosome aberrations in Syrian hamster embryo cells.

To assess the genotoxicity of 14 chemical agents used as locally applied agents in dental practice, the ability of these agents to elicit chromosome aberrations was examined using Syrian hamster embryo (SHE) cells. Chromosome aberrations in SHE cells were induced by treatment with three of eight chemical agents used as endodontic medicaments, i.e.

Ability of 13 chemical agents used in dental practice to induce sister-chromatid exchanges in Syrian hamster embryo cells.

To evaluate the genotoxic potential of 13 chemical agents used in dental practice, the abilities of these agents to induce sister-chromatid exchanges (SCEs) were examined using Syrian hamster embryo (SHE) cells. Statistically significant increases in the frequencies of SCEs were observed in SHE cells treated with all seven of the chemical agents used as endodontic medicaments: p-chlorophenol, m-cresol, formaldehyde, guaiacol, hydrogen peroxide, p-phenolsulfonic acid, and sodium hypochlorite (P < 0.01; Student t test).

Reversible conversion of immortal human cells from telomerase-positive to telomerase-negative cells.

Immortal cell lines and tumors maintain their telomeres via the telomerase pathway or via a telomerase-independent pathway, referred to as alternative lengthening of telomeres (ALT). Here, we show the reversible conversion of the human papillomavirus type 16 E6-induced immortal human fibroblasts E6 Cl 6 from telomerase-positive (Tel(+)) to telomerase-negative (Tel(-)) cells. Tel(+) cells converted spontaneously to Tel(-) cells that reverted to Tel(+) cells following treatment with trichostatin A (TSA) and/or 5-aza-2'-deoxycytidine (5-AZC), which induced the reversion from complete to partial methylation of the CpG islands of the human telomerase reverse transcriptase (hTERT) promoter in Tel(-) E6 Cl 6 cells.

Ability of fourteen chemical agents used in dental practice to induce chromosome aberrations in Syrian hamster embryo cells.

To assess the genotoxicity of 14 chemical agents used in dental practice, the ability of these agents to induce chromosome aberrations was examined using Syrian hamster embryo (SHE) cells. Statistically significant increases in the frequencies of chromosome aberrations were induced in SHE cells treated with 7 of 10 chemical agents used as endodontic medicaments, that is, carbol camphor, m-cresol, eugenol, guaiacol, zinc oxide, hydrogen peroxide, and formaldehyde. The other 3 chemical agents, that is, thymol, glutaraldehyde, and iodoform, did not increase the levels of chromosome aberrations.

A trivalent dimethylarsenic compound, dimethylarsine iodide, induces cellular transformation, aneuploidy, centrosome abnormality and multipolar spindle formation in Syrian hamster embryo cells.

The abilities of dimethylarsine iodide (DMI), a model compound of trivalent dimethylarsenicals, to induce cellular transformation, aneuploidy, centrosome abnormality, and multipolar spindle formations were investigated using the Syrian hamster embryo (SHE) cell model. Cellular growth was decreased in a concentration-dependent manner by treatment with DMI at concentrations over 0.1 microM.

Cell-transforming activity of fourteen chemical agents used in dental practice in Syrian hamster embryo cells.

Fourteen chemical agents used in dental practice were assessed for their cell-transforming activity using the Syrian hamster embryo (SHE) cell transformation assay system. The cell-transforming activity was quantitatively assessed by the frequency of morphological transformation (MT) in SHE cells induced by these agents. MT was induced by m-cresol, guaiacol, formaldehyde, sodium hypochlorite, hydrogen peroxide, sodium arsenite, acid fuchsin, and basic fuchsin, but not by p-chlorophenol, p-phenolsulfonic acid, glutaraldehyde, and erythrosine B.

Involvement of telomere dysfunction in the induction of genomic instability by radiation in scid mouse cells.

To determine the effects of a defect in NHEJ on the induction of genomic instability by radiation, we investigated X-ray-induced delayed chromosomal aberrations such as dicentrics and fragments in scid mouse cells. We found that radiosensitive scid mouse cells are more susceptible than wild-type mouse cells to the induction of delayed chromosomal aberrations when the cells are exposed to an equivalent survival dose of X-rays. Telomere FISH analysis revealed that radiation enhances the induction of telomeric fusions where telomeric sequences remain at the fused position (tel+ end-fusions), suggesting that radiation induces telomere dysfunction.