Osamu Uehara

Differentiation of mouse iPS cells into ameloblast-like cells in cultures using medium conditioned by epithelial cell rests of Malassez and gelatin-coated dishes

Induced pluripotent stem (iPS) cells are generated from adult cells and are potentially of great value in regenerative medicine. Recently, it was shown that iPS cells can differentiate into ameloblast-like cells in cultures using feeder cells. In the present study, we sought to induce differentiation of ameloblast-like cells from iPS cells under feeder-free conditions using medium conditioned by cultured epithelial cell rests of Malassez (ERM) cells and gelatin-coated dishes. Two culture conditions were compared: co-cultures of iPS cells and ERM cells; and, culture of iPS cells in ERM cell-conditioned medium. Differentiation of ameloblast-like cells in the cultures was assessed using real-time RT-PCR assays of expression of the marker genes keratin 14, amelogenin, and ameloblastin and by immunocytochemical staining for amelogenin. We found greater evidence of ameloblast-like cell differentiation in the cultures using the conditioned medium. In the latter, the level of amelogenin expression increased daily and was significantly higher than controls on the 7th, 10th, and 14th days. Expression of ameloblastin also increased daily and was significantly higher than controls on the 14th day. The present study demonstrates that mouse iPS cells can be induced to differentiate into ameloblast-like cells in feeder-free cell cultures using ERM cell-conditioned medium and gelatin-coated dishes.

Immunohistochemical evaluation of Klotho and DNA methyltransferase 3a in oral squamous cell carcinomas

Carcinoma follows a course of multiple changes that are affected by several important factors, with epigenetic silencing of the promoter gene being one of them. A series of studies have suggested that epigenetic changes in the anti-aging gene Klotho may be one of the emerging areas of concern in the study of carcinogenesis. We hypothesized that epigenetic silencing of Klotho due to hypermethylation of DNMT3a may be one of the causes of carcinoma in the oral and maxillofacial region. In this study, we analyzed the immunohistochemical expressions of Klotho and DNMT3a in tissues obtained from oral dysplasia and oral squamous cell carcinoma. Our results showed increased immune expression of DNMT3a, and decreased expression of Klotho in cells of the cancer tissues when compared with those in the dysplasia and healthy control samples. Chi-square tests complemented by adjusted residual analysis revealed significantly higher number of Klotho-positive and DNMT3a-negative cases in healthy controls, Klotho-negative and DNMT3a-negative cases in ODL, and Klotho-negative and DNMT3a-positive cases in OSCC when compared with the other types among the three groups (X2 = 46.66, p < 0.001). Thus, downregulation of Klotho may be associated with the overexpression of DNMT3a in cancer tissues.

hBD-2 is downregulated in oral carcinoma cells by DNA hypermethylation, and increased expression of hBD-2 by DNA demethylation and gene transfection inhibits cell proliferation and invasion

Human β-defensin-2 (hBD-2) is a type of epithelial antimicrobial peptide. The expression level of hBD-2 mRNA is lower in oral carcinoma cells (OCCs) than in healthy oral epithelium. Yet, it is still unknown how hBD-2 expression is downregulated in OCCs. The present study investigated DNA hypermethylation of hBD-2 in OCCs and the effect of the demethylation and increased expression of hBD-2 on cell proliferation and invasion. Six different types of oral carcinoma cell lines (OSC-19, BSC-OF, SAS, HSC-2, HSC-4 and HSY) and normal oral keratinocytes (NOKs) were used. The expression levels of hBD-2 in all OCCs were significantly lower than that in the NOKs. Treatment with DNA methyltransferase inhibitor, 5-aza-dC, at the concentration of 50 μM significantly induced upregulation of expression of hBD-2 in the OCCs. Using methylation-specific PCR, DNA hypermethylation was observed in all OCCs. These results suggest that DNA hypermethylation is, at least in part, involved in the decreased expression of hBD-2 in OCCs. We examined the effect of 5-aza-dC on the cell proliferation and invasive ability of OCCs. The cell invasion assays showed that the number of OCCs treated with 5-aza-dC on the filters was significantly lower than that of the controls. We examined whether increased expression of hBD-2 generated by gene transfection inhibited the proliferation and invasion of SAS cells. The number of SAS cells exhibiting increased expression of hBD-2 on the filters in the invasion assay were significantly lower on day 7 when compared with the control. hBD-2 may function as a tumor suppressor. Increased expression of hBD-2 induced by demethylation or increased expression generated by gene transfection may be useful therapeutic methods for oral carcinoma.

In vitro biofilm formation by Staphylococcus aureus isolated from wounds of hospital-admitted patients and their association with antimicrobial resistance

Introduction Staphylococcus aureus including methicillin-resistant S. aureus (MRSA) has the propensity to form biofilms, and causes significant mortality and morbidity in the patients with wounds. Our aim was to study the in vitro biofilm-forming ability of S. aureus isolated from wounds of hospitalized patients and their association with antimicrobial resistance. Materials and methods Forty-three clinical isolates of S. aureus were obtained from 150 pus samples using standard microbiological techniques. Biofilm formation in these isolates was detected by tissue culture plate (TCP) method and tube adherence method (TM). Antimicrobial susceptibility test was performed using the modified Kirby–Bauer disk diffusion method as per Clinical and Laboratory Standards Institute guidelines. MRSA was detected using the cefoxitin disk test. Results Biofilm formation was observed in 30 (69.8%) and 28 (65.1%) isolates of S. aureus via TCP method and TM, respectively. Biofilm-producing S. aureus exhibited a higher incidence of antimicrobial resistance when compared with the biofilm nonproducers (P<0.05). Importantly, 86.7% of biofilm-producing S. aureus were multidrug resistant (MDR), whereas all the biofilm nonproducers were non-MDR (P<0.05). Large proportions (43.3%) of biofilm producers were identified as MRSA; however, none of the biofilm nonproducers were found to be MRSA (P<0.05). Conclusion Both the in vitro methods showed that S. aureus isolated from wound infection of hospitalized patients have high degree of biofilm-forming ability. Biofilm-producing strains have very high tendency to exhibit antimicrobial resistance, multidrug resistance and methicillin resistance. Regular surveillance of biofilm formation by S. aureus and their antimicrobial resistance profile may lead to the early treatment of the wound infection.

Protective effects of oral astaxanthin nanopowder against ultraviolet-induced photokeratitis in mice

Purpose Astaxanthin (AST) has a strong antioxidant cellular membrane chaperone protective effect. Recently, a water-soluble nanosized AST (nano-AST) form was produced, which is expected to improve the efficacy of oral intake effects. The purpose of this study was to examine whether oral nano-AST has therapeutic effects on UV-induced photokeratitis in mice. Methods C57BL/6 mice were administered twice with either nano-AST, AST oil, lutein, or bilberry extracts 3 hours before and shortly before UV irradiation (dose: 400 mJ/cm2). The corneas were collected 24 hours after irradiation and stained with H&E and TUNEL. NF-κB, dihydroethidium (DHE), COX-2, p-IκB-α, TNFα, and CD45 expression were evaluated through immunohistochemistry, Western blot analysis, and qPCR. Results Corneal epithelium was significantly thicker in mice orally administered with nano-AST than in the others (p < 0.01), with significantly less NF-κB nucleus translocation (p < 0.001), and significantly fewer TUNEL cells (p < 0.01). Weaker DHE signals were detected in the nano-AST group (p < 0.05) relative to the others. Furthermore, reduced inflammation and decreased cell death in corneal tissue were observed in the nano-AST group, as indicated by a reduction in the expression of COX-2, p-IκB-α, TNFα, and CD45. Conclusions Oral administration of nano-AST demonstrated a protective effect on UV-induced photokeratitis via antioxidative, anti-inflammatory, and antiapoptotic activity.

Upregulated expression of MMP-9 in gingival epithelial cells induced by prolonged stimulation with arecoline

Betel quid chewing is implicated in the high prevalence of oral cancer in Southeast Asian countries. One of the major components of betel quid is arecoline. In the present study, in order to characterize the association between chronic arecoline stimulation and carcinogenesis the expression level of matrix metalloproteinase (MMP)-2, MMP-9, tissue inhibitor of metalloproteinase (TIMP)-1 and TIMP-2 mRNA in human gingival epithelial progenitor cells (HGEPs) stimulated with arecoline was assessed. The HGEPs were alternated between 3 days of incubation with arecoline (50 µg/ml), and 3 days without arecoline, for up to 30 days. The expression levels of the MMPs and TIMPs in the cells stimulated with arecoline were evaluated by reverse transcription-quantitative polymerase chain reaction at 18 and 30 days. The expression of MMP-9 mRNA in the experimental group was significantly increased compared with in the control group (P<0.01). No significant differences in the expression of MMP-2, TIMP-1 or TIMP-2 mRNA were observed between the experimental and control groups. Using an MMP-9 activity assay, the levels of MMP-9 activity in the experimental group were demonstrated to be significantly higher than in the control group (P<0.05). To investigate associated cellular signaling pathways, PDTC [a nuclear factor (NF)-κB/inhibitor of NF-κB (IκB) inhibitor], PD98059 [a mitogen-activated protein kinase kinase (MAPKK)1 and MAPKK2 inhibitor], SB203580 (a p38 MAPK inhibitor) and 5,15-DPP [a signal transduction and activator of transcription (STAT) 3 inhibitor] were used. All inhibitors decreased the extent of MMP-9 upregulation induced by stimulation with arecoline. Based on the data, it is hypothesized that MMP-9 activity may be involved in the pathological alterations of oral epithelium induced by betel quid chewing, and that the NF-κB/IκB, MAPK, p38 MAPK and STAT3 signaling pathways may be involved in the production of MMP-9 induced by betel quid chewing.