Sung-Hee Pi

Effects of nicotine on antioxidant defense enzymes and RANKL expression in human periodontal ligament cells.

BACKGROUND This study examined the effects of nicotine on osteoblastic differentiation and the osteoclastogenesis regulatory molecules receptor activator of nuclear factor-kappa B ligand (RANKL) and osteoprotegerin (OPG). In addition, we investigated the mechanism by which nicotine induced antioxidant defense enzyme expression as a protective response. METHODS The expression of osteoblast markers, RANKL, OPG, and antioxidant defense enzymes were examined in nicotine-treated human periodontal ligament (PDL) cells by reverse transcription-polymerase chain reaction and Western blotting. RESULTS Nicotine treatment concomitantly downregulated the expression of OPG and osteoblastic differentiation markers, such as alkaline phosphatase, osteocalcin, and osteopontin, and upregulated the expression of RANKL. Nicotine induced the synthesis of the transcription factor NF-E2-related factor-2 (Nrf2) as well as a number of cellular antioxidants and phase II enzymes, such as heme oxygenase-1. Pretreatment with antioxidants inhibited the upregulation of RANKL, the downregulation of OPG expression, and cytotoxicity by nicotine in PDL cells. CONCLUSIONS Nicotine upregulated RANKL and antioxidant defense enzymes. These data suggest that Nrf2-mediated induction of cellular antioxidants and phase II enzymes could contribute to the cellular defense against nicotine-induced cytotoxicity and osteoclastic differentiation in PDL cells.

Functionalization of scaffolds with chimeric anti-BMP-2 monoclonal antibodies for osseous regeneration

Recent studies have demonstrated the ability of murine anti-BMP-2 monoclonal antibodies (mAb) immobilized on an absorbable collagen sponge (ACS) to mediate de novo bone formation, a process termed antibody-mediated osseous regeneration (AMOR). The objectives of this study were to assess the efficacy of a newly generated chimeric anti-BMP-2 mAb in mediating AMOR, as well as to evaluate the suitability of different biomaterials as scaffolds to participate in AMOR. Chimeric anti-BMP-2 mAb was immobilized on 4 biomaterials, namely, titanium microbeads (Ti), alginate hydrogel, macroporous biphasic calcium phosphate (MBCP) and ACS, followed by surgical implantation into rat critical-size calvarial defects. Animals were sacrificed after 8 weeks and the degree of bone fill was assessed using micro-CT and histomorphometry. Results demonstrated local persistence of chimeric anti-BMP-2 mAb up to 8 weeks, as well as significant de novo bone regeneration in sites implanted with chimeric anti-BMP-2 antibody immobilized on each of the 4 scaffolds. Ti and MBCP showed the highest volume of bone regeneration, presumably due to their resistance to compression. Alginate and ACS also mediated de novo bone formation, though significant volumetric shrinkage was noted. In vitro assays demonstrated cross-reactivity of chimeric anti-BMP-2 mAb with BMP-4 and BMP-7. Immune complex of anti-BMP-2 mAb with BMP-2 induced osteogenic differentiation of C2C12 cells in vitro, involving expression of RUNX2 and phosphorylation of Smad1. The present data demonstrated the ability of chimeric anti-BMP-2 mAb to functionalize different biomaterial with varying characteristics to mediate osteogenesis.

Healing pattern of the mucous membrane after tooth extraction in the maxillary sinus

Purpose To investigate the healing pattern of the mucous membrane after tooth extraction necessitated by periodontal disease in the maxillary sinus. Methods One hundred and three patients with 119 maxillary sinuses were investigated. Before implant placement, cone-beam computed tomography (CT) scanning was performed. The causes of extraction, the time elapsed since extraction, smoking, periodontal disease in adjacent teeth, and gender were recorded. In addition, the thickness of the mucous membrane of the maxillary sinus and the height of residual alveolar bone at the extracted area were calculated from CT images. Results The thickness of the mucous membrane in the periodontal disease group (3.05±2.71 mm) was greater than that of the pulp disease group (1.92±1.78 mm) and the tooth fracture group (1.35±0.55 mm; P<0.05). The causes of extraction, the time elapsed since extraction, and gender had relationships with a thickening of the mucous membrane of the maxillary sinus (P<0.05). In contrast, the height of the residual alveolar bone at the extracted area, periodontal disease in adjacent teeth, and smoking did not show any relation to the thickening of the mucous membrane of the maxillary sinus. Conclusions The present study revealed distinct differences in healing patterns according to the causes of extraction in the maxillary sinus, especially periodontal disease, which resulted in more severe thickening of the mucous membrane.

Heme oxygenase-1 mediates nicotine- and lipopolysaccharide-induced expression of cyclooxygenase-2 and inducible nitric oxide synthase in human periodontal ligament cells

BACKGROUND AND OBJECTIVE Although heme oxygenase-1 (HO-1) plays a key role in inflammation, its anti-inflammatory effects and mechanism of action in periodontitis are still unknown. This study aimed to identify the effects of HO-1 on the proinflammatory mediators activated by nicotine and lipopolysaccharide (LPS) stimulation in human periodontal ligament (PDL) cells. MATERIAL AND METHODS The production of nitric oxide (NO) and prostaglandin E(2) (PGE(2)) was evaluated using Griess reagent and an enzyme immunoassay, respectively. The expression of inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2) and HO-1 proteins was evaluated by Western blot analysis. RESULTS Lipopolysaccharide and nicotine synergistically induced the production of NO and PGE(2) and increased the protein expression of iNOS, COX-2 and HO-1. Treatment with an HO-1 inhibitor and HO-1 small interfering RNAs blocked the LPS- and nicotine-stimulated NO and PGE(2) release as well as the expression of iNOS and COX-2. CONCLUSION Our data suggest that the nicotine- and LPS-induced inflammatory effects on PDL cells may act through a novel mechanism involving the action of HO-1. Thus, HO-1 may provide a potential therapeutic target for the treatment of periodontal disease associated with smoking and dental plaque.

The Anti-Inflammatory Role of Heme Oxygenase-1 in Lipopolysaccharide and Cytokine-Stimulated Inducible Nitric Oxide Synthase and Nitric Oxide Production in Human Periodontal Ligament Cells

BACKGROUND Although heme oxygenase-1 (HO-1) is involved in anti-inflammation, the mechanisms of its activity in regulating periodontal inflammation are largely unclear. Therefore, the aim of this study is to investigate the anti-inflammatory properties of HO-1 in lipopolysaccharide (LPS)- and proinflammatory cytokine-stimulated inducible nitric oxide synthase (iNOS) expression and nitric oxide (NO) production in human periodontal ligament (PDL) cells. METHODS PDL cells were treated with LPS plus a combination of tumor necrosis factor (TNF)-alpha and interleukin (IL)-1beta in serum-free media for 1 day. The production of NO was evaluated using a Griess reagent kit. The expression of iNOS and HO-1 proteins and mRNAs was evaluated using Western blotting and reverse transcriptase-polymerase chain reaction, respectively. RESULTS Proinflammatory cytokines and LPS triggered iNOS and HO-1 expression and NO production in PDL cells. HO-1 inhibitor and HO-1 small interfering RNA (siRNA) attenuated the LPS- and cytokine-stimulated NO release and iNOS and HO-1 expression. Specific inhibitors of p38, extracellular signal-regulated kinase (ERK), and c-Jun N-terminal kinase (JNK) mitogen-activated protein kinases phosphatidylinositol 3-kinase (PI3K), nuclear factor-kappa B (NF-kappaB), and protein kinase C delta (PKC-delta) greatly reduced the levels of iNOS and HO-1 expression induced by LPS plus cytokines. CONCLUSIONS Collectively, these data suggested that HO-1 inhibition blocked LPS- and proinflammatory cytokine-stimulated iNOS expression and NO production in PDL cells via a mechanism that involves p38, ERK, PI3K, NF-kappaB, and PKC-delta. Thus, the regulation of HO-1 activity may be a therapeutic strategy for periodontal disease.

Heme oxygenase-1 protects human periodontal ligament cells against substance P-induced RANKL expression

BACKGROUND AND OBJECTIVE Although substance P (SP) stimulates bone resorption activity and this is reported to be correlated with the degree of periodontal inflammation, it is unclear how human periodontal ligament cells regulate neuropeptide-induced osteoclastogenesis or the possible involvement of heme oxygenase-1 (HO-1) might be. This study examines how SP affects osteoprotegerin (OPG) and RANKL expression via HO-1. MATERIAL AND METHODS Using immortalized human periodontal ligament cells, the effects of SP on the expression of HO-1, RANKL and OPG mRNA and proteins were determined by RT-PCR and western blotting, respectively. Various concentrations of SP (10(-7), 10(-8), 10(-9) and 10(-10) m) were added to the medium, and the cells were treated for 0, 0.25, 0.5, 1, 2 and 3 d. RESULTS Substance P upregulated RANKL and HO-1 and downregulated OPG mRNA and protein expression in periodontal ligament cells, in a concentration- and time-dependent manner. A HO-1 inducer inhibited both the upregulation of RANKL expression and downregulation of OPG expression by SP in periodontal ligament cells. By contrast, treatment with a HO-1 inhibitor or HO-1 small interferring RNA (siRNA) enhanced SP-stimulated RANKL expression. Inhibitors of ERK and p38 MAP kinases, phosphoinositide 3-kinase and nuclear factor-kappaB blocked the effects of SP on RANKL expression in periodontal ligament cells. CONCLUSION These results suggest that SP stimulates osteoclastic differentiation by increasing the expression of RANKL vs. OPG via the HO-1 pathway in periodontal ligament cells. The HO-1 pathway may be an effective therapeutic target for inhibiting chronic periodontitis involving alveolar bone resorption.

IFITM1 increases osteogenesis through Runx2 in human alveolar-derived bone marrow stromal cells

The exact molecular mechanisms governing the differentiation of bone marrow stromal stem/progenitor cells (BMSCs) into osteoblasts remain largely unknown. In this study, a highly expressed protein that had a high degree of homology with interferon-induced transmembrane protein 1 (IFITM1) was identified using differentially expressed gene (DEG) screening. We sought to determine whether IFITM1 influenced osteoblast differentiation. During differentiation, IFITM1 expression gradually increased from 5 to 10days and subsequently decreased at 15 days in culture. Analysis of IFITM1 protein expression in several cell lines as well as in situ studies on human tissues revealed its selective expression in bone cells and human bone. Proliferation of human alveolar-derived bone marrow stromal cells (hAD-BMSCs) was significantly inhibited by IFITM1 knockdown by using short hairpin RNA, as were bone specific markers such as alkaline phosphatase, collagen type I α 1, bone sialoprotein, osteocalcin, and osterix were decreased. Calcium accumulation also decreased following IFITM1 knockdown. Moreover, IFITM1 knockdown in hAD-BMSCs was associated with inhibition of Runx2 mRNA and protein expression. Collectively, the present data provide evidence for the role of IFITM1 in osteoblast differentiation. The exact mechanisms of IFITM1s involvement in osteoblast differentiation are still under investigation.

Association of gingival biotype with the results of scaling and root planing

Purpose The concept of gingival biotype has been used as a predictor of periodontal therapy outcomes since the 1980s. In the present study, prospective and controlled experiments were performed to compare periodontal pocket depth (PPD) reduction and gingival shrinkage (GSH) after scaling and root planing (SRP) according to gingival biotype. Methods Twenty-five patients diagnosed with chronic periodontitis participated in the present study. The PPD and GSH of the labial side of the maxillary anterior teeth (from the right canine to the left canine) were evaluated at baseline and 3 months after SRP. Changes in the PPD following SRP were classified into 4 groups according to the gingival thickness and initial PPD. Two more groups representing normal gingival crevices were added in evaluation of the GSH. The results were statistically analyzed using the independent t-test. Results In the end, 16 patients participated in the present study. With regard to PPD reduction, there were no significant differences according to gingival biotype (P>0.05). Likewise, sites with a PPD of over 3 mm failed to show any significant differences in the GSH (P>0.05). However, among the sites with a PPD of under 3 mm, those with the thin gingival biotype showed more GSH (P<0.05). Conclusions PPD changes after SRP were not affected by gingival biotype with either shallow or deep periodontal pockets. GSH also showed equal outcomes in all the groups without normal gingival crevices. The results of SRP seem not to differ according to gingival biotype.

BST2 Mediates Osteoblast Differentiation via the BMP2 Signaling Pathway in Human Alveolar-Derived Bone Marrow Stromal Cells

The molecular mechanisms controlling the differentiation of bone marrow stromal stem cells into osteoblasts remain largely unknown. In this study, we investigated whether bone marrow stromal antigen 2 (BST2) influences differentiation toward the osteoblasts lineage. BST2 mRNA expression in human alveolar-derived bone marrow stromal cells (hAD-BMSCs) increased during differentiation into osteoblasts. hAD-BMSCs differentiation into osteoblasts and the mRNA expression of the bone-specific markers alkaline phosphatase, collagen type α 1, bone sialoprotein, osteocalcin, and osterix were reduced by BST2 knockdown using siRNA. Furthermore, BST2 knockdown in hAD-BMSCs resulted in decreased RUNX2 mRNA and protein expression. We hypothesized that BST2 is involved in differentiation of into osteoblasts via the BMP2 signaling pathway. Accordingly, we evaluated the mRNA expression levels of BMP2, BMP receptors (BMPR1 and 2), and the downstream signaling molecules SMAD1, SMAD4, and p-SMAD1/5/8 in BST2 knockdown cells. BMP2 expression following the induction of differentiation was significantly lower in BST2 knockdown cells than in cells treated with a non-targeting control siRNA. Similar results were found for the knockdown of the BMP2 receptor- BMPR1A. We also identified significantly lower expression of SMAD1, SMAD4, and p-SMAD1/5/8 in the BST2 knockdown cells than control cells. Our data provide the first evidence that BST2 is involved in the osteogenic differentiation of bone marrow stromal cells via the regulation of the BMP2 signaling pathway.

Alveolar Crestal Approach for Maxillary Sinus Membrane Elevation with <4 mm of Residual Bone Height: A Case Report

Introduction For maxillary sinus membrane elevation (MSME), the lateral window approach and crestal approach are available, and high success rates have been achieved with low residual bone height as a development of technology. Objective To evaluate MSME using the crestal approach with a rotary-grind bur (RGB (including reamer or sinus bur)) in patients with residual bone height of <4 mm. Materials and Methods Ten implants were placed in 10 patients with residual bone height of <4 mm, by sinus elevation using an RGB. The implant stability quotient (ISQ) was measured immediately after implant placement (ISQ 1) and before taking impression for the final prosthesis (ISQ 2). The extent of marginal bone loss was measured on periapical radiographs. Results The mean residual bone height before implant placement was 3.41 ± 0.53 mm; no complications, including membrane perforation, severe postoperative pain, or discomfort, occurred either during or after surgery. The mean ISQ 1 was 63.4 ± 12.1, whereas the mean ISQ 2 was 77.6 ± 5.8. The mean marginal bone resorption was 0.23 ± 0.18 mm on periapical radiographs. Conclusions MSME using the crestal approach with an RGB is a reliable technique for implant placement in sites where available bone is insufficient.