Chan Ho Park

The Ohio State University, Columbus, Ohio, United States

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Publications (23)77.03 Total impact

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    Full-text · Dataset · Aug 2015
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    ABSTRACT: Plant pathogens can deliver effector proteins to plant cells to target pattern recognition receptors (PRRs) or key components in the PAMP-triggered immunity (PTI) signaling pathway to suppress the defense response. APIP6, a RING-type E3 ligase, is targeted by the Magnaporthe oryzae effector AvrPiz-t for the suppression of PTI in rice plants. However, the downstream signal of APIP6 remains unclear. Here, we report that APIP6 interacts with OsELF3-2 (Homolog of Arabidopsis ELF3) in yeast two-hybrid screens using APIP6 as the bait. The expression of OsELF3-2 is induced in both incompatible and compatible rice–blast interactions. Transient expression assays in Nicotiana benthamiana leaves indicate that OsELF3-2 is localized predominantly in the nucleus. Compared with the wild type, the oself3-2 mutant and RNAi plants leads to a significant increase of flg22- and chitin-induced ROS generation, and enhanced resistance to compatible a M. oryzae isolate. Co-expression assays in rice protoplasts and N. benthamiana leaves indicate that APIP6 can promote OsELF3-2 degradation and the degradation can be inhibited by MG132. Take together; these results demonstrate that OsELF3-2 plays a negative role in PTI and is regulated by the APIP6-mediated ubiquitination pathway in rice.
    Full-text · Article · Aug 2015 · Molecular Plant
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    ABSTRACT: The ubiquitin proteasome system in plants plays important roles in plant-microbe interactions and in immune responses to pathogens. We previously demonstrated that the rice U-box E3 ligase SPL11 and its Arabidopsis ortholog PUB13 negatively regulate programmed cell death (PCD) and defense response. However, the components involved in the SPL11/ PUB13-mediated PCD and immune signaling pathway remain unknown. In this study, we report that SPL11-interacting Protein 6 (SPIN6) is a Rho GTPase-activating protein (Rho-GAP) that interacts with SPL11 in vitro and in vivo. SPL11 ubiquitinates SPIN6 in vitro and degrades SPIN6 in vivo via the 26S proteasome-dependent pathway. Both RNAi silencing in transgenic rice and knockout of Spin6 in a T-DNA insertion mutant lead to PCD and increased resistance to the rice blast pathogen Magnaporthe oryzae and the bacterial blight pathogen Xanthomonas oryzae pv. oryzae. The levels of reactive oxygen species and defense related gene expression are significantly elevated in both the Spin6 RNAi and mutant plants. Strikingly, SPIN6 interacts with the small GTPase OsRac1, catalyze the GTP-bound OsRac1 into the GDP-bound state in vitro and has GAP activity towards OsRac1 in rice cells. Together, our results demonstrate that the RhoGAP SPIN6 acts as a linkage between a U-box E3 ligase-mediated ubiquitination pathway and a small GTPase-associated defen-some system for plant immunity.
    Full-text · Article · Feb 2015 · PLoS Pathogens
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    ABSTRACT: Lesion mimic mutants have been used to dissect programmed cell death (PCD) and defense-related pathways in plants. The rice lesion-mimic mutant spl11 exhibits race nonspecific resistance to the bacterial pathogen Xanthomonas oryzae pv. oryzae and the fungal pathogen Magnaporthe oryzae. Spl11 encodes an E3 ubiquitin ligase and is a negative regulator of PCD in rice. To study the regulation of Spl11-mediated PCD, we performed a genetic screen and identified three spl11 cell-death suppressor (sds) mutants. These suppressors were characterized for their resistance to X. oryzae pv. oryzae and M. oryzae and for their expression of defense-related genes. The suppression of the cell-death phenotypes was generally correlated with reduced expression of defense-related genes. When rice was challenged with avirulent isolates of M. oryzae, the disease phenotype was unaffected in the sds mutants, indicating that the suppression might be Spl11-mediated pathway specific and may only be involved in basal defense. In addition, we mapped one of the suppressor mutations to a 140-kb interval on the long arm of rice chromosome 1. Identification and characterization of these sds mutants should facilitate our efforts to elucidate the Spl11-mediated PCD pathway.
    Full-text · Article · Jun 2014 · Molecular Plant-Microbe Interactions
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    ABSTRACT: The rice U-box/ARM E3 ubiquitin ligase SPL11 negatively regulates programmed cell death (PCD) and disease resistance, and controls flowering time through interacting with the novel RNA/DNA binding KH domain protein SPIN1. Overexpression of Spin1 causes late flowering in transgenic rice under short-day (SD) and long-day (LD) conditions. In this study, we characterized the function of the RNA-binding and SPIN1-interacting 1 (RBS1) protein in flowering time regulation. Rbs1was identified in a yeast-two-hybrid screen using the full-length Spin1 cDNA as a bait and encodes an RNA binding protein with three RNA recognition motifs. The protein binds RNA in vitro and interacts with SPIN1 in the nucleus. Rbs1 overexpression causes delayed flowering under SD and LD conditions in rice. Expression analyses of flowering marker genes show that Rbs1 overexpression represses the expression of Hd3a under SD and LD conditions. Rbs1 is upregulated in both Spin1 overexpression plants and in the spl11 mutant. Interestingly, Spin1 expression is increased but Spl11 expression is repressed in the Rbs1 overexpression plants. Western blot analysis revealed that the SPIN1 protein level is increased in the Rbs1 overexpression plants and that the RBS1 protein level is also up-regulated in the Spin1 overexpression plants. These results suggest that RBS1 is a new negative regulator of flowering time that itself is positively regulated by SPIN1 but negatively regulated by SPL11 in rice.
    Full-text · Article · Jan 2014 · PLoS ONE
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    ABSTRACT: In the oral and craniofacial complex, tooth loss is the most commonly acquired disfiguring injury. Among the most formidable challenges of reconstructing tooth-supporting osseous defects in the oral cavity is the regeneration of functional multi-tissue complexes involving bone, ligament, and tooth cementum. Furthermore, periodontal multi-tissue engineering with spatiotemporal orientation of the periodontal ligament (PDL) remains the most challenging obstacle for restoration of physiological loading and homeostasis. We report on the ability of a hybrid computer-designed scaffold - developed utilizing computed tomography - to predictably facilitate the regeneration and integration of dental supporting tissues. Here we provide the protocol for rapid prototyping, manufacture, surgical implantation, and evaluation of dual-architecture scaffolds for controlling fiber orientation and facilitating morphogenesis of bone-ligament complexes. In contrast to conventional single-system methods of fibrous tissue formation, our protocol supports rigorous control of multi-compartmental scaffold architecture using computational scaffold design and manufacturing by 3D printing, as well as the evaluation of newly-regenerated tissue physiology for clinical implementation.
    No preview · Article · Nov 2013 · Tissue Engineering Part C Methods
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    ABSTRACT: Background: Stem cell therapy offers potential in the regeneration of craniofacial bone defects however, has it not been studied clinically. Tissue repair cells (TRCs) isolated from bone marrow represent a mixed stem and progenitor population enriched in CD90 and CD14 positive cells. In this Phase I/II, randomized, controlled, feasibility trial, we investigated TRC cell therapy to reconstruct localized craniofacial bone defects. Methods: 24 patients requiring localized reconstruction of jawbone defects participated in this longitudinal trial. For regenerative therapy, patients were randomized to receive either guided bone regeneration (GBR) or TRC transplantation. 6 or 12 weeks following treatment, clinical and radiographic assessments of bone repair were performed. Bone biopsies were harvested and underwent quantitative micro-computed tomographic (μCT) and bone histomorphometric analyses. Oral implants were installed, subsequently restored and functionally loaded with tooth restorations. Reconstructed sites were assessed for one year following therapy. Results: No study-related, serious adverse events were reported. Following therapy, clinical, radiographic, tomographic, and histological measures demonstrated that TRC therapy accelerated alveolar bone regeneration compared to GBR therapy. Additionally, TRC treatment significantly reduced the need for secondary bone grafting at the time of oral implant placement with a 5-fold decrease in implant bony dehiscence exposure (residual bone defects) as compared to GBR-treated sites (p < 0.01). Conclusions: Transplantation of TRCs for treatment of alveolar bone defects appears safe and accelerates bone regeneration, enabling jawbone reconstruction with oral implants. The results from this trial support expanded studies of TRC therapy in the treatment of craniofacial deformities (ClinicalTrials.gov number CT00755911).
    Full-text · Article · Jul 2012 · Cell Transplantation
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    ABSTRACT: Regeneration of bone-ligament complexes destroyed due to disease or injury is a clinical challenge due to complex topologies and tissue integration required for functional restoration. Attempts to reconstruct soft-hard tissue interfaces have met with limited clinical success. In this investigation, we manufactured biomimetic fiber-guiding scaffolds using solid free-form fabrication methods that custom fit complex anatomical defects to guide functionally-oriented ligamentous fibers in vivo. Compared to traditional, amorphous or random-porous polymeric scaffolds, the use of perpendicularly oriented micro-channels provides better guidance for cellular processes anchoring ligaments between two distinct mineralized structures. These structures withstood biomechanical loading to restore large osseous defects. Cell transplantation using hybrid scaffolding constructs with guidance channels resulted in predictable oriented fiber architecture, greater control of tissue infiltration, and better organization of ligament interface than random scaffold architectures. These findings demonstrate that fiber-guiding scaffolds drive neogenesis of triphasic bone-ligament integration for a variety of clinical scenarios.
    Full-text · Article · Jan 2012 · Biomaterials
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    ABSTRACT: The aims of this article were to perform a detailed evaluation of the healing of extraction sockets covered with a resorbable collagen membrane 12 weeks following exodontia and to determine if this device had ossifying properties. Ten consecutive subjects in need of extraction of maxillary premolars were recruited. Each subject had a hopeless maxillary premolar extracted with minimal trauma. Sockets were then covered with a collagen barrier membrane alone. At 12 weeks, reentry surgery was performed, clinical measurements were repeated, and bone core biopsies were obtained prior to dental implant placement for histologic and microcomputed tomography (micro-CT) analysis. Study sites showed mean bone regeneration horizontally of 7.7 mm (buccopalatally) and 4.6 mm (mesiodistally). Vertical bone repair showed a mean gain of 10.9 mm. Subtraction radiography showed a mean apical shift of the crestal bone at the center of the socket of 2.1 mm (range, 0.7 to 4.3 mm). Micro-CT and histology revealed formation of well-mineralized tissue at 12 weeks, with a mean percentage of vital bone of 45.87% ± 12.35%. No signs of membrane ossification were observed. A detailed analysis of tissue neogenesis in extraction sites protected by this barrier membrane has demonstrated that adequate bone formation for implant placement occurs as early as 12 weeks following exodontia, with minimal changes in alveolar ridge dimensions. No evidence of membrane ossification was observed.
    No preview · Article · Sep 2011 · The International journal of periodontics & restorative dentistry
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    ABSTRACT: Ubiquitin-regulated protein degradation is a critical regulatory mechanism that controls a wide range of biological processes in plants. Here, we report that OsDIS1 (for Oryza sativa drought-induced SINA protein 1), a C3HC4 RING finger E3 ligase, is involved in drought-stress signal transduction in rice (O. sativa). The expression of OsDIS1 was up-regulated by drought treatment. In vitro ubiquitination assays showed that OsDIS1 possessed E3 ubiquitin ligase activity and that the conserved region of the RING finger was required for the activity. Transient expression assays in Nicotiana benthamiana leaves and rice protoplasts indicated that OsDIS1 was localized predominantly in the nucleus. Overexpression of OsDIS1 reduced drought tolerance in transgenic rice plants, while RNA interference silencing of OsDIS1 enhanced drought tolerance. Microarray analysis revealed that a large number of drought-responsive genes were induced or suppressed in the OsDIS1 overexpression plants under normal and drought conditions. Yeast two-hybrid screening showed that OsDIS1 interacted with OsNek6 (for O. sativa NIMA-related kinase 6), a tubulin complex-related serine/threonine protein kinase. Coexpression assays in N. benthamiana leaves indicated that OsNek6 was degraded by OsDIS1 via the 26S proteasome-dependent pathway and that this degradation was abolished by the OsDIS1(H71Y) mutation, which is essential for its E3 ligase activity. Together, these results demonstrate that OsDIS1 plays a negative role in drought stress tolerance through transcriptional regulation of diverse stress-related genes and possibly through posttranslational regulation of OsNek6 in rice.
    Full-text · Article · Jun 2011 · Plant physiology

  • No preview · Conference Paper · May 2011
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    ABSTRACT: Inflammatory periodontal diseases are a leading cause of tooth loss and are linked to multiple systemic conditions, such as cardiovascular disease and stroke. Reconstruction of the support and function of affected tooth-supporting tissues represents an important therapeutic endpoint for periodontal regenerative medicine. An improved understanding of periodontal biology coupled with current advances in scaffolding matrices has introduced novel treatments that use cell and gene therapy to enhance periodontal tissue reconstruction and its biomechanical integration. Cell and gene delivery technologies have the potential to overcome limitations associated with existing periodontal therapies, and may provide a new direction in sustainable inflammation control and more predictable tissue regeneration of supporting alveolar bone, periodontal ligament, and cementum. This review provides clinicians with the current status of these early-stage and emerging cell- and gene-based therapeutics in periodontal regenerative medicine, and introduces their future application in clinical periodontal treatment. The paper concludes with prospects on the application of cell and gene tissue engineering technologies for reconstructive periodontology.
    Preview · Article · Feb 2011 · Journal of Periodontology
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    Chan Ho Park · Minsuk Kahng
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    ABSTRACT: Although temporal context may significantly affect the popularity of items and user preference over items, traditional information filtering techniques such as recommender systems have not sufficiently considered temporal factors. Modeling temporal dynamics in user behavior is not trivial, and it is challenging to study its effect in order to provide better recommendation results to users. To incorporate temporal effects into information filtering systems, we analyze a large sized real-world usage log data gathered from Bugs Music, which is one of the well-known online music service in Korea, and study temporal dynamics in users' music listening behaviors considering periodicity of time dimension and popularity change. We insist that the result of our analysis can be a useful guideline to the industry which delivers music items to users and tries to consider temporal context in their recommendations.
    Preview · Conference Paper · Aug 2010
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    ABSTRACT: A major clinical challenge in the reconstruction of large oral and craniofacial defects is the neogenesis of osseous and ligamentous interfacial structures. Currently, oral regenerative medicine strategies are unpredictable for repair of tooth-supporting tissues destroyed as a consequence of trauma, chronic infection or surgical resection. Here, we demonstrate multi-scale computational design and fabrication of composite hybrid polymeric scaffolds for targeted cell transplantation of genetically modified human cells for the formation of human tooth dentin-ligament-bone complexes in vivo. The newly-formed tissues demonstrate the interfacial generation of parallel- and obliquely-oriented fibers that grow and traverse within the polycaprolactone (PCL)-poly(glycolic acid) (PGA) designed constructs forming tooth cementum-like tissue, ligament, and bone structures. This approach offers potential for the clinical implementation of customized periodontal scaffolds that may enable regeneration of multi-tissue interfaces required for oral, dental and craniofacial engineering applications.
    Full-text · Article · Aug 2010 · Biomaterials
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    ABSTRACT: For the determination of key factors or devices that promote periodontal regeneration, preclinical investigations using in vivo animal models are critical for evaluating the biological responses before human clinical trial testing. In this chapter, we provide an overview on the commonly used preclinical animals for the study of reconstructive procedures to promote bone and soft tissue repair of tooth-supporting periodontal defects. Steps are provided on the animal management for evaluation of outcome measures using descriptive histology, histomorphometry, three-dimensional imaging, and safety assessments. The use of these key measures of periodontal regeneration should aid investigators in the selection of appropriate surrogate endpoints to be utilized in the clinical arena, which are not practical or ethical in humans. These methods will prepare investigators and assist them in identifying endpoints that can then be adapted to human clinical trial planning.
    No preview · Article · Jan 2010 · Methods in molecular biology (Clifton, N.J.)
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    ABSTRACT: Periodontal disease is a chronic inflammatory condition induced by tooth-associated microbial biofilms that induce a host immune response. Therapeutic control of progressive tissue destruction in high-risk patients is a significant challenge in therapy. Soluble protein delivery of antagonists to tumor necrosis factor-alpha (TNF-alpha) inhibits alveolar bone resorption due to periodontitis. However, protein therapy raises several concerns, such as recurrence of disease activity after treatment cessation and repeated dosing regimens. In this study, we used pseudotyped adeno-associated virus vector based on serotype 1 (AAV2/1) to deliver the TNF receptor-immunoglobulin Fc (TNFR:Fc) fusion gene to rats subjected to experimental Porphyromonas gingivalis (Pg)-lipopolysaccharide (LPS)-mediated bone loss. Animals received Pg-LPS delivered to the gingivae thrice weekly for 8 weeks, vehicle alone, Pg-LPS and intramuscular delivery of pseudotyped AAV2/1-TNFR:Fc vector (1 x 10(11) DNase I-resistant particles) or AAV2/1-TNFR:Fc vector delivered to naive animals. AAV2/1-TNFR:Fc therapy led to sustained therapeutic levels of serum TNFR protein and protected against Pg-LPS-mediated loss of bone volume and density. Furthermore, AAV2/1-TNFR:Fc administration reduced local levels of multiple proinflammatory cytokines and osteoclast-like cells at the periodontal lesions. These findings suggest that delivery of AAV2/1-TNFR:Fc may be a viable approach to modulate periodontal disease progression.
    Full-text · Article · Mar 2009 · Gene therapy
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    ABSTRACT: Rice blast disease, caused by the fungus Magnaporthe oryzae, is a leading constraint to rice production and is a serious threat to food security worldwide. To elucidate the function of effector proteins from M. oryzae in pathogenesis and interaction with the host, we have performed RL-SAGE and MPSS approaches to study the gene expression profiles of M. oryzae during the interaction. The RL-SAGE and MPSS analyses identified 3,441 and 3,004 annotated M. oryzae genes from blast infected rice leaf tissues, respectively. Among them, 217 genes encoding putative secreted proteins, which may play important roles as effectors, were identified. We developed a highly efficient transient protoplast system for gene functional analysis in rice. We present here the detailed procedure of the rice protoplast transient expression system and show the examples of using the system for functional analysis of putative effectors from M. oryzae. The combination of RL-SAGE/MPSS genomic profiling approaches with a protoplast functional assay system has provided an efficient approach for large-scale isolation and analysis of effectors from M. oryzae.
    No preview · Chapter · Dec 2008
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    ABSTRACT: Ubiquitin ligases play a central role in determining the specificity of the ubiquitination system by selecting a myriad of appropriate candidate proteins for modification. The U-box is a recently identified, ubiquitin ligase activity-related protein domain that shows greater presence in plants than in other organisms. In this study, we identified 77 putative U-box proteins from the rice genome using a battery of whole genome analysis algorithms. Most of the U-box protein genes are expressed, as supported by the identification of their corresponding expressed sequence tags (ESTs), full-length cDNAs, or massively parallel signature sequencing (MPSS) tags. Using the same algorithms, we identified 61 U-box proteins from the Arabidopsis genome. The rice and Arabidopsis U-box proteins were classified into nine major classes based on their domain compositions. Comparison between rice and Arabidopsis U-box proteins indicates that the majority of rice and Arabidopsis U-box proteins have the same domain organizations. The inferred phylogeny established the homology between rice and Arabidopsis U-box/ARM proteins. Cell death assay using the rice protoplast system suggests that one rice U-box gene, OsPUB51, might act as a negative regulator of cell death signaling. In addition, the selected U-box proteins were found to be functional E3 ubiquitin ligases. The identification and analysis of rice U-box proteins hereby at the genomic level will help functionally characterize this class of E3 ubiquitin ligase in the future.
    Full-text · Article · Sep 2008 · Molecular Plant
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    ABSTRACT: The RANKL-OPG axis is a key regulator of osteoclastogenesis and bone turnover activity. Its contribution to bone resorption under altered mechanical states, however, has not been fully elucidated. Here we examined the role of OPG in regulating mechanically induced bone modeling in a rat model of orthodontic tooth movement. The maxillary first molars of male Sprague-Dawley rats were moved mesially using a calibrated nickel-titanium spring attached to the maxillary incisor teeth. Two different doses (0.5 mg/kg, 5.0 mg/kg) of a recombinant fusion protein (OPG-Fc), were injected twice weekly mesial to the first molars. Tooth movement was measured using stone casts that were scanned and magnified. Changes in bone quantity were measured using micro-computed tomography and histomorphometric analysis was used to quantify osteoclasts and volumetric parameters. Finally, circulating levels of TRAP-5b (a bone resorption marker) was measured using enzyme-linked immunosorbent assay. The 5.0 mg/kg OPG-Fc dose showed a potent reduction in mesial molar movement and osteoclast numbers compared to controls (p<0.01). The molar movement was inhibited by 45.7%, 70.6%, and 78.7% compared to controls at days 7, 14, and 21 respectively, with the high dose of OPG. The 0.5 mg dose also significantly (p<0.05) inhibited molar movement at days 7 (43.8%) and 14 (31.8%). While incisor retraction was also decreased by OPG-Fc, the ratio of incisor to molar tooth movement was markedly better in the high-dose OPG group (5.2:1, p<0.001) compared to the control group (2.3:1) and the low-dose OPG group (2.0:1). Local delivery of OPG-Fc inhibits osteoclastogenesis and tooth movement at targeted dental sites.
    Full-text · Article · Sep 2007 · Bone
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    ABSTRACT: Prevention of alveolar bone destruction is a clinical challenge in periodontal disease treatment. The receptor activator of nuclear factor-kappa B ligand (RANKL) inhibitor osteoprotegerin (OPG) inhibits osteoclastogenesis and suppresses bone resorption. To study the effects of RANKL inhibition on alveolar bone loss, an experimental ligature-induced model of periodontitis was used. A total of 32 rats were administered human OPG-Fc fusion protein (10 mg/kg) or vehicle by subcutaneous delivery twice weekly for 6 weeks. Negative or positive controls received no treatment or disease through vehicle delivery, respectively. Biopsies were harvested after 3 and 6 weeks, and mandibulae were evaluated by microcomputed tomography (microCT) and histology. Serum levels of human OPG-Fc and tartrate-resistant acid phosphatase-5b (TRAP-5b) were measured throughout the study by enzyme-linked immunosorbent assay (ELISA). Statistical analyses included analysis of variance (ANOVA) and Tukey tests. Human OPG-Fc was detected in the sera of OPG-Fc-treated animals by 3 days and throughout the study. Serum TRAP-5b was sharply decreased by OPG-Fc treatment soon after OPG-Fc delivery and remained low for the observation period. Significant preservation of alveolar bone volume was observed among OPG-Fc-treated animals compared to the controls at weeks 3 and 6 (P <0.05). Descriptive histology revealed that OPG-Fc significantly suppressed osteoclast surface area at the alveolar crest. Systemic delivery of OPG-Fc inhibits alveolar bone resorption in experimental periodontitis, suggesting that RANKL inhibition may represent an important therapeutic strategy for the prevention of progressive alveolar bone loss.
    Full-text · Article · Jul 2007 · Journal of Periodontology

Publication Stats

515 Citations
77.03 Total Impact Points

Institutions

  • 2008-2015
    • The Ohio State University
      • Department of Plant Pathology
      Columbus, Ohio, United States
  • 2007-2012
    • University of Michigan
      • • Department of Periodontics and Oral Medicine
      • • Department of Biomedical Engineering
      Ann Arbor, Michigan, United States