Publications by authors named "Dana Graves"

111 Publications

Osteoblast lineage cells and periodontal ligament fibroblasts regulate orthodontic tooth movement that is dependent on Nuclear Factor-kappa B (NF-kB) activation.

Angle Orthod 2021 Apr 14. Epub 2021 Apr 14.

Objectives: To investigate the role of NF-κB in osteoblast lineage cells and periodontal ligament (PDL) fibroblasts during orthodontic tooth movement (OTM).

Materials And Methods: Transgenic mice that expressed a dominant negative mutant of the inhibitor of kB kinase (IKK-DN) with lineage specific expression in osteoblastic cells and PDL fibroblasts driven by a response element in the collagen1α1 promoter and matched wild-type (WT) mice were examined. A 10-12 g force was applied by a NiTi coil and maintained for 5 or 12 days. OTM distance, PDL width, and bone volume fraction were measured using micro computed tomography. Osteoclast numbers were counted in tartrate-resistant acid phosphatase-stained sections. Activation of nuclear factor kappa B (NF-kB) was assessed by nuclear localization of p65, and the receptor activator of nuclear factor-κB ligand (RANKL) was measured by immunofluorescence and compared to control specimens with no orthodontic force.

Results: OTM-induced NF-kB activation (p65 nuclear localization) in WT mice was largely blocked in transgenic (TG) mice. OTM was significantly reduced in the TG mice compared to WT mice along with reduced osteoclastogenesis, narrower PDL width, higher bone volume fraction, and reduced RANKL expression.

Conclusions: Osteoblast lineage cells and PDL fibroblasts are key contributors to alveolar bone remodeling in OTM through IKKβ dependent NF-κB activation.
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http://dx.doi.org/10.2319/031520-182.1DOI Listing
April 2021

FOXO1 expression in chondrocytes modulates cartilage production and removal in fracture healing.

Bone 2021 Jul 1;148:115905. Epub 2021 Mar 1.

Department of Periodontics, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA, USA. Electronic address:

Fracture healing is a multistage process characterized by inflammation, cartilage formation, bone deposition, and remodeling. Chondrocytes are important in producing cartilage that forms the initial anlagen for the hard callus needed to stabilize the fracture site. We examined the role of FOXO1 by selective ablation of FOXO1 in chondrocytes mediated by Col2α1 driven Cre recombinase. Experimental mice with lineage-specific FOXO1 deletion (Col2α1CreFOXO1) and negative control littermates (Col2α1CreFOXO1) were used for in vivo, closed fracture studies. Unexpectedly, we found that in the early phases of fracture healing, FOXO1 deletion significantly increased the amount of cartilage formed, whereas, in later periods, FOXO1 deletion led to a greater loss of cartilage. FOXO1 was functionally important as its deletion in chondrocytes led to diminished bone formation on day 22. Mechanistically, the early effects of FOXO1 deletion were linked to increased proliferation of chondrocytes through enhanced expression of cell cycle genes that promote proliferation and reduced expression of those that inhibit it and increased expression of cartilage matrix genes. At later time points experimental mice with FOXO1 deletion had greater loss of cartilage, enhanced formation of osteoclasts, increased IL-6 and reduced numbers of M2 macrophages. These results identify FOXO1 as a transcription factor that regulates chondrocyte behavior by limiting the early expansion of cartilage and preventing rapid cartilage loss at later phases.
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http://dx.doi.org/10.1016/j.bone.2021.115905DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8106874PMC
July 2021

Clinical application of a FOXO1 inhibitor improves connective tissue healing in a diabetic minipig model.

Am J Transl Res 2021 15;13(2):781-791. Epub 2021 Feb 15.

Department of Periodontics, School of Dental Medicine, University of Pennsylvania Philadelphia, PA, USA.

The forkhead box O1 (FOXO1) transcription factor plays a key role in wound healing process. Recently it has been reported that lineage-specific genetic ablation of FOXO1 significantly improves diabetic wound healing in a mouse model. To investigate the clinical usefulness of these findings, translational preclinical studies with a large animal model are needed. We report for the first time that the local application of a FOXO1 inhibitor (AS1842856) significantly improves connective tissue healing in a preclinical T2DM minipig model, reflected by increased collagen matrix formation, increased myofibroblast numbers, improved angiogenesis, and a shift in cell populations from pro-inflammatory (IL-1β, TNF-α and iNOS) to pro-healing (CD163). Our results set up the basis for the clinical application of a FOXO1 antagonist in early diabetic wounds where there is impaired connective tissue healing.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7868841PMC
February 2021

Keratinocyte Function in Normal and Diabetic Wounds and Modulation by FOXO1.

J Diabetes Res 2020 28;2020:3714704. Epub 2020 Oct 28.

Department of Periodontics, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA, 19104 Pennsylvania, USA.

Diabetes has a significant and negative impact on wound healing, which involves complex interactions between multiple cell types. Keratinocytes play a crucial role in the healing process by rapidly covering dermal and mucosal wound surfaces to reestablish an epithelial barrier with the outside environment. Keratinocytes produce multiple factors to promote reepithelialization and produce factors that enhance connective tissue repair through the elaboration of mediators that stimulate angiogenesis and production of connective tissue matrix. Among the factors that keratinocytes produce to aid healing are transforming growth factor- (TGF-), vascular endothelial growth factor-A (VEGF-A), connective tissue growth factor (CTGF), and antioxidants. In a diabetic environment, this program is disrupted, and keratinocytes fail to produce growth factors and instead switch to a program that is detrimental to healing. Changes in keratinocyte behavior have been linked to high glucose and advanced glycation end products that alter the activities of the transcription factor, FOXO1. This review examines reepithelialization and factors produced by keratinocytes that upregulate connective tissue healing and angiogenesis and how they are altered by diabetes.
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http://dx.doi.org/10.1155/2020/3714704DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7641706PMC
October 2020

Depletion of the diabetic gut microbiota resistance enhances stem cells therapy in type 1 diabetes mellitus.

Theranostics 2020 17;10(14):6500-6516. Epub 2020 May 17.

Department of Oral and Maxillofacial Surgery, Peking University School and Hospital of Stomatology, 22 Zhongguancun Nandajie, Haidian District, Beijing 100081, People's Republic of China.

Microbiome, considered as the "second genome" of the host, is altered in type 1 diabetes mellitus (T1DM) patients to a state of dysbiosis. Mesenchymal stem cell (MSC) transplantation is a promising treatment for T1DM but is limited by several factors in the diabetic host. In this study, we tested the hypothesis that dysbiotic gut microbiota may limit MSC therapy, and modulating gut microbiota may help to improve the effects of MSC transplantation. NOD/Ltj mice, treated with adipose-derived stem cells (ADSCs), were fed with an antibiotics cocktails (Abx) for 1 week. The blood glucose levels, insulitis, intestinal permeability and gut bacteria translocation to the pancreas were evaluated. 16s rRNA and colon tissue transcription sequencing were performed to analyze beneficial bacteria and reactive host biomolecules in the ADSCs+Abx group. Based on the sequencing results, specific bacteria were gavaged orally to diabetic mice to confirm their effect on ADSCs transplantation in T1DM was determined. We found that the recolonized the diabetic gut microbiota abolished the therapeutic effect of ADSCs. On the contrary, depletion of the diabetic gut microbiota by antibiotics treatment in diabetic mice significantly enhanced the therapeutic effects of ADSCs as measured by reversal of hyperglycemia, insulitis, and increased insulin output. Mechanistically, treatment with antibiotics increased the abundance of in the gut and reduced bacterial translocation to the pancreas by promoting Mucin2 expression and thickening the mucus layer through TRPM7. The mechanism was confirmed the re-colonization of the gut by through oral gavage that produced similar results. These results provide the rationale for a new approach to improve MSC therapy for T1DM by altering the gut microbiota.
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http://dx.doi.org/10.7150/thno.44113DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7255019PMC
April 2021

The Interrelationship Between Diabetes, IL-17 and Bone Loss.

Curr Osteoporos Rep 2020 02;18(1):23-31

Department of Periodontics, School of Dental Medicine, University of Pennsylvania, 240 S 40th St, Philadelphia, PA, 19104, USA.

Purpose Of Review: Diabetes has a detrimental effect on bone, increasing the risk of fracture and formation of osteolytic lesions such as those seen in periodontitis. Several diabetic complications are caused by diabetes-enhanced inflammation. This review examines mechanisms by which IL-17 contributes to diabetes-enhanced periodontitis and other effects of IL-17 on bone.

Recent Findings: IL-17 upregulates anti-bacterial defenses, yet its expression is also linked to a destructive host response in the periodontium. Periodontal disease is caused by bacteria that stimulate an inflammatory response. Diabetes-enhanced IL-17 increases gingival inflammation, which alters the composition of the oral microbiota to increase its pathogenicity. In addition, IL-17 can induce osteoclastogenesis by upregulation of TNF and RANKL in a number of cell types, and IL-17 has differential effects on osteoblasts and their progenitors. Increased IL-17 production caused by diabetes alters the pathogenicity of the oral microbiota and can promote periodontal bone resorption.
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http://dx.doi.org/10.1007/s11914-020-00559-6DOI Listing
February 2020

The impact of diabetes on periodontal diseases.

Periodontol 2000 2020 02;82(1):214-224

Department of Periodontics, School of Dental Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA.

The susceptibility and severity of periodontal diseases is made more severe by diabetes, with the impact on the disease process inversely proportional to the level of glycemic control. Although type 1 diabetes mellitus and type 2 diabetes mellitus have different etiologies, and their impact on bone is not identical, they share many of the same complications. Studies in animals and humans agree that both forms of diabetes increase inflammatory events in periodontal tissue, impair new bone formation, and increase expression of RANKL in response to bacterial challenge. High levels of glucose, reactive oxygen species, and advanced glycation end-products are found in the periodontium of diabetic individuals and lead to increased activation of nuclear factor-kappa B and expression of inflammatory cytokines such as tumor necrosis factor and interleukin-1. Studies in animals, moreover, suggest that there are multiple cell types in periodontal tissues that are affected by diabetes, including leukocytes, vascular cells, mesenchymal stem cells, periodontal ligament fibroblasts, osteoblasts, and osteocytes. The etiology of periodontal disease involves the host response to bacterial challenge that is affected by diabetes, which increases the expression of RANKL and reduces coupled bone formation. In addition, the inflammatory response also modifies the oral microbiota to render it more pathogenic, as demonstrated by increased inflammation and bone loss in animals where bacteria are transferred from diabetic donors to germ-free hosts compared with transfer from normoglycemic donors. This approach has the advantage of not relying upon limited knowledge of the specific bacterial taxa to determine pathogenicity, and examines the overall impact of the microbiota rather than the presumed pathogenicity of a few bacterial groups. Thus, animal studies have provided new insights into pathogenic mechanisms that identify cause-and-effect relationships that are difficult to perform in human studies.
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http://dx.doi.org/10.1111/prd.12318DOI Listing
February 2020

Mucosal Immunity and the FOXO1 Transcription Factors.

Front Immunol 2019 29;10:2530. Epub 2019 Nov 29.

Department of Periodontics, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA, United States.

FOXO1 transcription factors affect a number of cell types that are important in the host response. Cell types whose functions are modulated by FOXO1 include keratinocytes in the skin and mucosal dermis, neutrophils and macrophages, dendritic cells, Tregs and B-cells. FOXO1 is activated by bacterial or cytokine stimulation. Its translocation to the nucleus and binding to promoter regions of genes that have response elements is stimulated by the MAP kinase pathway and inhibited by the PI3 kinase/AKT pathway. Downstream gene targets of FOXO1 include pro-inflammatory signaling molecules (TLR2, TLR4, IL-1β, and TNF-α), wound healing factors (TGF-β, VEGF, and CTGF) adhesion molecules (integrins-β1, -β3, -β6, αβ, CD11b, CD18, and ICAM-1), chemokine receptors (CCR7 and CXCR2), B cell regulators (APRIL and BLYS), T-regulatory modulators (Foxp3 and CTLA-4), antioxidants (GPX-2 and cytoglobin), and DNA repair enzymes (GADD45α). Each of the above cell types are found in oral mucosa and modulated by bacteria or an inflammatory microenvironment. FOXO1 contributes to the regulation of these cells, which collectively maintain and repair the epithelial barrier, formation and activation of Tregs that are needed to resolve inflammation, mobilization, infiltration, and activation of anti-bacterial defenses in neutrophils, and the homing of dendritic cells to lymph nodes to induce T-cell and B-cell responses. The goal of the manuscript is to review how the transcription factor, FOXO1, contributes to the activation and regulation of key leukocytes needed to maintain homeostasis and respond to bacterial challenge in oral mucosal tissues. Examples are given with an emphasis on lineage specific deletion of to explore the impact of FOXO1 on cell behavior, inflammation and susceptibility to infection.
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http://dx.doi.org/10.3389/fimmu.2019.02530DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6896163PMC
November 2020

IFT80 Is Required for Fracture Healing Through Controlling the Regulation of TGF-β Signaling in Chondrocyte Differentiation and Function.

J Bone Miner Res 2020 03 22;35(3):571-582. Epub 2019 Nov 22.

Department of Anatomy and Cell Biology, University of Pennsylvania, Philadelphia, PA, USA.

Primary cilia are essential cellular organelles that are anchored at the cell surface membrane to sense and transduce signaling. Intraflagellar transport (IFT) proteins are indispensable for cilia formation and function. Although major advances in understanding the roles of these proteins in bone development have been made, the mechanisms by which IFT proteins regulate bone repair have not been identified. We investigated the role of the IFT80 protein in chondrocytes during fracture healing by creating femoral fractures in mice with conditional deletion of IFT80 in chondrocytes utilizing tamoxifen inducible Col2α1-CreER mice. Col2α1 IFT80 mice had smaller fracture calluses than IFT80 (control) mice. The max-width and max-callus area were 31% and 48% smaller than those of the control mice, respectively. Col2α1 IFT80 mice formed low-density/porous woven bony tissue with significantly lower ratio of bone volume, Trabecular (Tb) number and Tb thickness, and greater Tb spacing compared to control mice. IFT80 deletion significantly downregulated the expression of angiogenesis markers-VEGF, PDGF and angiopoietin and inhibited fracture callus vascularization. Mechanistically, loss of IFT80 in chondrocytes resulted in a decrease in cilia formation and chondrocyte proliferation rate in fracture callus compared to the control mice. Meanwhile, IFT80 deletion downregulated the TGF-β signaling pathway by inhibiting the expression of TGF-βI, TGF-βR, and phosphorylation of Smad2/3 in the fracture callus. In primary chondrocyte cultures in vitro, IFT80 deletion dramatically reduced chondrocyte proliferation, cilia assembly, and chondrogenic gene expression and differentiation. Collectively, our findings demonstrate that IFT80 and primary cilia play an essential role in fracture healing, likely through controlling chondrocyte proliferation and differentiation, and the TGF-β signaling pathway. © 2019 American Society for Bone and Mineral Research.
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http://dx.doi.org/10.1002/jbmr.3902DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7525768PMC
March 2020

Diabetes-Induced NF-κB Dysregulation in Skeletal Stem Cells Prevents Resolution of Inflammation.

Diabetes 2019 11 22;68(11):2095-2106. Epub 2019 Aug 22.

Department of Periodontics, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA

Type 1 diabetes (T1D) imposes a significant health burden by negatively affecting tissue regeneration during wound healing. The adverse effect of diabetes is attributed to high levels of inflammation, but the cellular mechanisms responsible remain elusive. In this study, we show that intrinsic skeletal stem cells (SSCs), a subset of mesenchymal stem cells, are essential for resolution of inflammation to occur during osseous healing by using genetic approaches to selectively ablate SSCs. T1D caused aberrant nuclear factor-κB (NF-κB) activation in SSCs and substantially enhanced inflammation in vivo. Constitutive or tamoxifen-induced inhibition of NF-κB in SSCs rescued the impact of diabetes on inflammation, SSC expansion, and tissue formation. In contrast, NF-κB inhibition in chondrocytes failed to reverse the effect of T1D. Mechanistically, diabetes caused defective proresolving macrophage (M2) polarization by reducing TGF-β1 expression by SSCs, which was recovered by NF-κB inhibition or exogenous TGF-β1 treatment. These data identify an underlying mechanism for altered healing in T1D and demonstrate that diabetes induces NF-κB hyperactivation in SSCs to disrupt their ability to modulate M2 polarization and resolve inflammation.
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http://dx.doi.org/10.2337/db19-0496DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6804629PMC
November 2019

Oral microbial dysbiosis linked to worsened periodontal condition in rheumatoid arthritis patients.

Sci Rep 2019 06 10;9(1):8379. Epub 2019 Jun 10.

Penn Dental School, University of Pennsylvania, Philadelphia, PA, USA.

Rheumatoid arthritis (RA) is an autoimmune disease characterized by joint inflammation. Individuals with RA have a higher risk of periodontitis and periodontitis has been linked to RA through the production of enzymes by periodontal pathogens that citrullinate proteins. This linkage is supported by findings that periodontitis is associated with increased RA severity and treatment of periodontitis can improve the symptoms of RA. The possible mechanism for this association is through dysbiosis of the oral microbiota triggered by RA-induced systemic inflammation. We examined the RA status of subjects by measuring the number of tender and swollen joints, anti-citrullinated protein antibody and rheumatoid factor. Periodontal disease status and salivary cytokine levels were measured, and dental plaque analyzed by 16S rRNA high throughput sequencing. RA patients had a higher bacterial load, a more diverse microbiota, an increase in bacterial species associated with periodontal disease, more clinical attachment loss, and increased production of inflammatory mediators including IL-17, IL-2, TNF, and IFN-γ. Furthermore, changes in the oral microbiota were linked to worse RA conditions. Our study provides new insights into the bi-directional relationship between periodontitis and RA and suggest that monitoring the periodontal health of RA patients is particularly important.
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http://dx.doi.org/10.1038/s41598-019-44674-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6557833PMC
June 2019

Deletion of FOXO1 in chondrocytes rescues the effect of diabetes on mechanical strength in fracture healing.

Bone 2019 06 21;123:159-167. Epub 2019 Mar 21.

Department of Periodontics, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA. Electronic address:

Diabetes increases the risk of fracture, impairs fracture healing and causes rapid loss of the fracture callus cartilage, which was linked to increased FOXO1 expression in chondrocytes. We recently demonstrated that deletion of FOXO1 in chondrocytes blocked the premature removal of cartilage associated with endochondral bone formation during fracture healing. However, the ultimate impact of this deletion on mechanical strength was not investigated and remains unknown. Closed fractures were induced in Col2α1Cre.FOXO1 mice with lineage specific deletion of FOXO1 in chondrocytes compared to littermate controls. Type 1 diabetes was induced by multiple low dose streptozotocin treatment. Thirty-five days after fracture micro CT analysis showed that diabetes significantly reduced callus volume and bone volume (P < 0.05), both which were reversed by FOXO1 deletion in chondrocytes. Diabetes significantly reduced mechanical strength measured by maximum torque, stiffness, modulus of rigidity and toughness and FOXO1 deletion in diabetic mice rescued each parameter (P < 0.05). Diabetes also reduced both bone volume and mechanical strength in non-fractured femurs. However, FOXO1 deletion did not affect bone volume or strength in non-fractured bone. These results point to the important effect that diabetes has on chondrocytes and show for the first time that the premature removal of cartilage induced by FOXO1 in chondrocytes has a significant impact on the mechanical strength of the healing bone.
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http://dx.doi.org/10.1016/j.bone.2019.03.026DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6491266PMC
June 2019

Chondrocytes Promote Vascularization in Fracture Healing Through a FOXO1-Dependent Mechanism.

J Bone Miner Res 2019 03 20;34(3):547-556. Epub 2018 Nov 20.

Department of Periodontics, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA, USA.

Chondrocytes play an essential role in fracture healing by producing cartilage, which forms an anlage for endochondral ossification that stabilizes the healing fracture callus. More recently it has been appreciated that chondrocytes have the capacity to produce factors that may affect the healing process. We examined the role of chondrocytes in angiogenesis during fracture healing and the role of the transcription factor forkhead box-O 1 (FOXO1), which upregulates wound healing in soft tissue. Closed fractures were induced in experimental mice with lineage-specific FOXO1 deletion by Cre recombinase under the control of a collagen-2α1 promoter element (Col2α1Cre FOXO1 ) and Cre recombinase negative control littermates containing flanking loxP sites (Col2α1Cre FOXO1 ). Experimental mice had significantly reduced CD31 new vessel formation. Deletion of FOXO1 in chondrocytes in vivo suppressed the expression of vascular endothelial growth factor-A (VEGFA) at both the protein and mRNA levels. Overexpression of FOXO1 in chondrocytes in vitro increased VEGFA mRNA levels and VEGFA transcriptional activity whereas silencing FOXO1 reduced it. Moreover, FOXO1 interacted directly with the VEGFA promoter and a deacetylated FOXO1 mutant enhanced VEGFA expression whereas an acetylated FOXO1 mutant did not. Lastly, FOXO1 knockdown by siRNA significantly reduced the capacity of chondrocytes to stimulate microvascular endothelial cell tube formation in vitro. The results indicate that chondrocytes play a key role in angiogenesis which is FOXO1 dependent and that FOXO1 in chondrocytes regulates a potent angiogenic factor, VEGFA. These studies provide new insight into fracture healing given the important role of vessel formation in the fracture repair process. © 2018 American Society for Bone and Mineral Research.
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http://dx.doi.org/10.1002/jbmr.3610DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6414243PMC
March 2019

FOXO1 Deletion Reverses the Effect of Diabetic-Induced Impaired Fracture Healing.

Diabetes 2018 12 2;67(12):2682-2694. Epub 2018 Oct 2.

Department of Periodontics, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA

Type 1 diabetes impairs fracture healing. We tested the hypothesis that diabetes affects chondrocytes to impair fracture healing through a mechanism that involves the transcription factor FOXO1. Type 1 diabetes was induced by streptozotocin in mice with FOXO1 deletion in chondrocytes (Col2α1CreFOXO1) or littermate controls (Col2α1CreFOXO1) and closed femoral fractures induced. Diabetic mice had 77% less cartilage and 30% less bone than normoglycemics evaluated histologically and by micro-computed tomography. Both were reversed with lineage-specific FOXO1 ablation. Diabetic mice had a threefold increase in osteoclasts and a two- to threefold increase in RANKL mRNA or RANKL-expressing chondrocytes compared with normoglycemics. Both parameters were rescued by FOXO1 ablation in chondrocytes. Conditions present in diabetes, high glucose (HG), and increased advanced glycation end products (AGEs) stimulated FOXO1 association with the RANKL promoter in vitro, and overexpression of FOXO1 increased RANKL promoter activity in luciferase reporter assays. HG and AGE stimulated FOXO1 nuclear localization, which was reversed by insulin and inhibitors of TLR4, histone deacetylase, nitric oxide, and reactive oxygen species. The results indicate that chondrocytes play a prominent role in diabetes-impaired fracture healing and that high levels of glucose, AGEs, and tumor necrosis factor-α, which are elevated by diabetes, alter RANKL expression in chondrocytes via FOXO1.
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http://dx.doi.org/10.2337/db18-0340DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6245226PMC
December 2018

FOXO1 regulates VEGFA expression and promotes angiogenesis in healing wounds.

J Pathol 2018 07 20;245(3):258-264. Epub 2018 Apr 20.

Department of Periodontics, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA, USA.

Angiogenesis is a critical aspect of wound healing. We investigated the role of keratinocytes in promoting angiogenesis in mice with lineage-specific deletion of the transcription factor FOXO1. The results indicate that keratinocyte-specific deletion of Foxo1 reduces VEGFA expression in mucosal and skin wounds and leads to reduced endothelial cell proliferation, reduced angiogenesis, and impaired re-epithelialization and granulation tissue formation. In vitro FOXO1 was needed for VEGFA transcription and expression. In a porcine dermal wound-healing model that closely resembles healing in humans, local application of a FOXO1 inhibitor reduced angiogenesis. This is the first report that FOXO1 directly regulates VEGFA expression and that FOXO1 is needed for normal angiogenesis during wound healing. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
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http://dx.doi.org/10.1002/path.5075DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6566901PMC
July 2018

Effect of Obesity or Metabolic Syndrome and Diabetes on Osseointegration of Dental Implants in a Miniature Swine Model: A Pilot Study.

J Oral Maxillofac Surg 2018 Aug 1;76(8):1677-1687. Epub 2018 Mar 1.

Associate Professor, Section of Oral, Diagnostic and Rehabilitation Sciences, College of Dental Medicine, Columbia University, New York, NY; and Global Medical Director, Straumann Group, Basel, Switzerland.

Purpose: The increasing prevalence of obesity or metabolic syndrome (O/MS) and type 2 diabetes mellitus (DM) remains a global health concern. Clinically relevant and practical translational models mimicking human characteristics of these conditions are lacking. This study aimed to demonstrate proof of concept of the induction of stable O/MS and type 2 DM in a Göttingen minipig model and validate both of these disease-adjusted Göttingen minipig models as impaired healing models for the testing of dental implants.

Materials And Methods: Nine minipigs were split into 3 groups-control (normal diet), obese (cafeteria diet), and diabetic (cafeteria diet plus low-dosage streptozotocin)-followed by placement of dental implants. Inflammatory markers including tumor necrosis factor α, C-reactive protein, and cortisol were recorded for each study group. Removal torque was measured, and histomorphometric analysis (bone-to-implant contact and bone area fraction occupancy) was performed.

Results: O/MS pigs showed, on average, a 2-fold increase in plasma C-reactive protein (P < .05) and cortisol (P < .09) concentrations compared with controls; DM pigs showed, on average approximately, a 40-fold increase in plasma tumor necrosis factor α levels (P < .05) and a 2-fold increase in cortisol concentrations (P < .05) compared with controls. The impact of O/MS and DM on implants was determined. The torque to interface failure was highest in the control group (200 N-cm) and significantly lower in the O/MS (90 N-cm) and DM (60 N-cm) groups (P < .01). Bone formation around implants was significantly greater in the control group than in the O/MS and DM groups (P < .02).

Conclusions: Both O/MS and DM minipigs express a human-like disease phenotype, and both presented bone-healing impairment around dental implants. Our finding of no significant difference between type 2 DM and O/MS in bone formation around implants provides evidence that further investigation of the impact of O/MS is warranted.
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http://dx.doi.org/10.1016/j.joms.2018.02.021DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6064394PMC
August 2018

RANKL deletion in periodontal ligament and bone lining cells blocks orthodontic tooth movement.

Int J Oral Sci 2018 02 26;10(1). Epub 2018 Feb 26.

Department of Periodontics, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA, USA.

The bone remodeling process in response to orthodontic forces requires the activity of osteoclasts to allow teeth to move in the direction of the force applied. Receptor activator of nuclear factor-κB ligand (RANKL) is essential for this process although its cellular source in response to orthodontic forces has not been determined. Orthodontic tooth movement is considered to be an aseptic inflammatory process that is stimulated by leukocytes including T and B lymphocytes which are presumed to stimulate bone resorption. We determined whether periodontal ligament and bone lining cells were an essential source of RANKL by tamoxifen induced deletion of RANKL in which Cre recombinase was driven by a 3.2 kb reporter element of the Col1α1 gene in experimental mice (Col1α1.CreER.RANKL) and compared results with littermate controls (Col1α1.CreER.RANKL). By examination of Col1α1.CreER.ROSA26 reporter mice we showed tissue specificity of tamoxifen induced Cre recombinase predominantly in the periodontal ligament and bone lining cells. Surprisingly we found that most of the orthodontic tooth movement and formation of osteoclasts was blocked in the experimental mice, which also had a reduced periodontal ligament space. Thus, we demonstrate for the first time that RANKL produced by periodontal ligament and bone lining cells provide the major driving force for tooth movement and osteoclastogenesis in response to orthodontic forces.
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http://dx.doi.org/10.1038/s41368-017-0004-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5944595PMC
February 2018

The Role of Forkhead Box 1 (FOXO1) in the Immune System: Dendritic Cells, T Cells, B Cells, and Hematopoietic Stem Cells.

Crit Rev Immunol 2017 ;37(1):1-13

Department of Periodontics, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA, USA.

Forkhead box-O (FOXO) transcription factors have a fundamental role in the development and differentiation of immune cells. FOXO1 and FOXO3 are FOXO members that are structurally similar and bind to the same conserved consensus DNA sequences to induce transcription. FOXO1 has been studied in detail in the activation of dendritic cells (DCs), where it plays an important role through the regulation of target genes such as ICAM-1, CCR7, and the integrin αvβ3. FOXO1 is activated by bacteria challenge in DCs and promotes DC bacterial phagocytosis, migration, homing to lymph nodes, DC stimulation of CD4+ T cells and resting B cells, and antibody production. Deletion of FOXO1 in DCs enhances susceptibility to bacteria-induced periodontal disease. FOXO1 and FOXO3 maintain naive T cell quiescence and survival. FOXO1 and FOXO3 enhance the formation of regulatory T cells and inhibit the formation of T-helper 1 (Th1) and Th17 cells. FOXO1 promotes differentiation, proliferation, survival, immunoglobulin gene rearrangement, and class switching in B cells, but FOXO3 has little effect. Both FOXO1 and FOXO3 are important in the maintenance of hematopoietic stem cells by protecting them from oxidative stress. This review examines FOXO1/FOXO3 in the adaptive immune response, key target genes, and FOXO inhibition by the phosphoinositide 3-kinase/AKT pathway.
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http://dx.doi.org/10.1615/CritRevImmunol.2017019636DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6085137PMC
April 2019

Osteocytes play an important role in experimental periodontitis in healthy and diabetic mice through expression of RANKL.

J Clin Periodontol 2018 03 25;45(3):285-292. Epub 2018 Jan 25.

Department of Periodontics, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA, USA.

Aim: Periodontitis results from bacteria-induced inflammation. A key cytokine, RANKL, is produced by a number of cell types. The cellular source of RANKL critical for periodontitis has not been established.

Methods: We induced periodontal bone loss by oral inoculation of Porphyromonas gingivalis and Fusobacterium nucleatum in both normoglycaemic and streptozotocin-induced type 1 diabetic mice. Experimental transgenic mice had osteocyte-specific deletion of floxed receptor activator of nuclear factor kappa-B ligand (RANKL) mediated by DMP-1-driven Cre recombinase. Outcomes were assessed by micro-CT, histomorphometric analysis, immunofluorescent analysis of RANKL and tartrate-resistant acid phosphatase staining for osteoclasts and osteoclast activity.

Results: Oral infection stimulated RANKL expression in osteocytes of wild-type mice, which was increased by diabetes and blocked in transgenic mice. Infected wild-type mice had significant bone loss and increased osteoclast numbers and activity, which were further enhanced by diabetes. No bone loss or increase in osteoclastogenesis or activity was detected in transgenic mice with RANKL deletion in osteocytes that were normoglycaemic or diabetic.

Conclusions: This study demonstrates for the first time the essential role of osteocytes in bacteria-induced periodontal bone loss and in diabetes-enhanced periodontitis.
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http://dx.doi.org/10.1111/jcpe.12851DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5811370PMC
March 2018

FOXO1 Regulates Bacteria-Induced Neutrophil Activity.

Front Immunol 2017 4;8:1088. Epub 2017 Sep 4.

Department of Periodontics, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA, United States.

Neutrophils play an essential role in the innate immune response to microbial infection and are particularly important in clearing bacterial infection. We investigated the role of the transcription factor FOXO1 in the response of neutrophils to bacterial challenge with and . In these experiments, the effect of lineage-specific FOXO1 deletion in LyzM.CreFOXO1 mice was compared with matched littermate controls. FOXO1 deletion negatively affected several critical aspects of neutrophil function including mobilization of neutrophils from the bone marrow (BM) to the vasculature, recruitment of neutrophils to sites of bacterial inoculation, and clearance of bacteria. FOXO1 regulated neutrophil chemotaxis and bacterial killing. Moreover, bacteria-induced expression of CXCR2 and CD11b, which are essential for several aspects of neutrophil function, was dependent on FOXO1 and . Furthermore, FOXO1 directly interacted with the promoter regions of CXCR2 and CD11b. Bacteria-induced nuclear localization of FOXO1 was dependent upon toll-like receptor (TLR) 2 and/or TLR4 and was significantly reduced by inhibitors of reactive oxygen species (ROS and nitric oxide synthase) and deacetylases (Sirt1 and histone deacetylases). These studies show for the first time that FOXO1 activation by bacterial challenge is needed to mobilize neutrophils to transit from the BM to peripheral tissues in response to infection as well as for bacterial clearance . Moreover, FOXO1 regulates neutrophil function that facilitates chemotaxis, phagocytosis, and bacterial killing.
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http://dx.doi.org/10.3389/fimmu.2017.01088DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5591501PMC
September 2017

FOXO1 deletion in keratinocytes improves diabetic wound healing through MMP9 regulation.

Sci Rep 2017 09 5;7(1):10565. Epub 2017 Sep 5.

Department of Periodontics, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA, USA.

Keratinocyte migration is a key aspect of re-epithelialization during wound healing. Matrix metalloproteinase 9 (MMP9) contributes to this process and deficiencies in the MMP9 lead to impaired healing. Inappropriate expression of MMP9 also contributes to impaired re-epithelialization. Previously we demonstrated that FOXO1 was activated in wound healing but to higher levels in diabetic wounds. To address mechanisms of impaired re-epithelialization we examined MMP9 expression in vivo in full thickness dermal scalp wounds created in experimental K14.Cre .Foxo1 mice with lineage-specific Cre recombinase deletion of floxed FOXO1 and compared the results to control littermates. MMP9 was induced during wound healing but at a significantly higher level in diabetic compared to normal wounds. FOXO1 deletion substantially blocked this increase. By chromatin immunoprecipitation FOXO1 was shown to bind to the MMP9 promoter, FOXO1 overexpression increased MMP9 transcriptional activity and increased MMP9 expression stimulated by high glucose was blocked by FOXO1 deletion or FOXO1 knockdown. We also show for the first time that high glucose impairs keratinocyte migration by inducing high levels of MMP9 expression and establish that it involves FOXO1. Thus, FOXO1 drives high levels of MMP9 expression in diabetic wound healing, which represents a novel mechanism for impaired re-epithelization in diabetic wounds.
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http://dx.doi.org/10.1038/s41598-017-10999-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5585410PMC
September 2017

Diabetes Enhances IL-17 Expression and Alters the Oral Microbiome to Increase Its Pathogenicity.

Cell Host Microbe 2017 Jul;22(1):120-128.e4

Department of Periodontics, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA, USA. Electronic address:

Diabetes is a risk factor for periodontitis, an inflammatory bone disorder and the greatest cause of tooth loss in adults. Diabetes has a significant impact on the gut microbiota; however, studies in the oral cavity have been inconclusive. By 16S rRNA sequencing, we show here that diabetes causes a shift in oral bacterial composition and, by transfer to germ-free mice, that the oral microbiota of diabetic mice is more pathogenic. Furthermore, treatment with IL-17 antibody decreases the pathogenicity of the oral microbiota in diabetic mice; when transferred to recipient germ-free mice, oral microbiota from IL-17-treated donors induced reduced neutrophil recruitment, reduced IL-6 and RANKL, and less bone resorption. Thus, diabetes-enhanced IL-17 alters the oral microbiota and renders it more pathogenic. Our findings provide a mechanistic basis to better understand how diabetes can increase the risk and severity of tooth loss.
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http://dx.doi.org/10.1016/j.chom.2017.06.014DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5701758PMC
July 2017

Subgingival microbiota dysbiosis in systemic lupus erythematosus: association with periodontal status.

Microbiome 2017 03 20;5(1):34. Epub 2017 Mar 20.

Faculty of Dentistry, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil.

Background: Periodontitis results from the interaction between a subgingival biofilm and host immune response. Changes in biofilm composition are thought to disrupt homeostasis between the host and subgingival bacteria resulting in periodontal damage. Chronic systemic inflammatory disorders have been shown to affect the subgingival microbiota and clinical periodontal status. However, this relationship has not been examined in subjects with systemic lupus erythematosus (SLE). The objective of our study was to investigate the influence of SLE on the subgingival microbiota and its connection with periodontal disease and SLE activity.

Methods: We evaluated 52 patients with SLE compared to 52 subjects without SLE (control group). Subjects were classified as without periodontitis and with periodontitis. Oral microbiota composition was assessed by amplifying the V4 region of 16S rRNA gene from subgingival dental plaque DNA extracts. These amplicons were examined by Illumina MiSeq sequencing.

Results: SLE patients exhibited higher prevalence of periodontitis which occurred at a younger age compared to subjects of the control group. More severe forms of periodontitis were found in SLE subjects that had higher bacterial loads and decreased microbial diversity. Bacterial species frequently detected in periodontal disease were observed in higher proportions in SLE patients, even in periodontal healthy sites such as Fretibacterium, Prevotella nigrescens, and Selenomonas. Changes in the oral microbiota were linked to increased local inflammation, as demonstrated by higher concentrations of IL-6, IL-17, and IL-33 in SLE patients with periodontitis.

Conclusions: SLE is associated with differences in the composition of the microbiota, independently of periodontal status.
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http://dx.doi.org/10.1186/s40168-017-0252-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5359961PMC
March 2017

TNFα contributes to diabetes impaired angiogenesis in fracture healing.

Bone 2017 06 8;99:26-38. Epub 2017 Mar 8.

Department of Periodontics, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA. Electronic address:

Diabetes increases the likelihood of fracture, interferes with fracture healing and impairs angiogenesis. The latter may be significant due to the critical nature of angiogenesis in fracture healing. Although it is known that diabetes interferes with angiogenesis the mechanisms remain poorly defined. We examined fracture healing in normoglycemic and streptozotocin-induced diabetic mice and quantified the degree of angiogenesis with antibodies to three different vascular markers, CD34, CD31 and Factor VIII. The role of diabetes-enhanced inflammation was investigated by treatment of the TNFα-specific inhibitor, pegsunercept starting 10days after induction of fractures. Diabetes decreased both angiogenesis and VEGFA expression by chondrocytes. The reduced angiogenesis and VEGFA expression in diabetic fractures was rescued by specific inhibition of TNF in vivo. In addition, the TNF inhibitor rescued the negative effect of diabetes on endothelial cell proliferation and endothelial cell apoptosis. The effect of TNFα in vitro was enhanced by high glucose and an advanced glycation endproduct to impair microvascular endothelial cell proliferation and tube formation and to stimulate apoptosis. The effect of TNF, high glucose and an AGE was mediated by the transcription factor FOXO1, which increased expression of p21 and caspase-3. These studies indicate that inflammation plays a major role in diabetes-impaired angiogenesis in endochondral bone formation through its effect on microvascular endothelial cells and FOXO1.
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http://dx.doi.org/10.1016/j.bone.2017.02.014DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5563392PMC
June 2017

FOXO1 expression in keratinocytes promotes connective tissue healing.

Sci Rep 2017 02 21;7:42834. Epub 2017 Feb 21.

Department of Periodontics, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA, USA.

Wound healing is complex and highly orchestrated. It is well appreciated that leukocytes, particularly macrophages, are essential for inducing the formation of new connective tissue, which requires the generation of signals that stimulate mesenchymal stem cells (MSC), myofibroblasts and fibroblasts. A key role for keratinocytes in this complex process has yet to be established. To this end, we investigated possible involvement of keratinocytes in connective tissue healing. By lineage-specific deletion of the forkhead box-O 1 (FOXO1) transcription factor, we demonstrate for the first time that keratinocytes regulate proliferation of fibroblasts and MSCs, formation of myofibroblasts and production of collagen matrix in wound healing. This stimulation is mediated by a FOXO1 induced TGFβ1/CTGF axis. The results provide direct evidence that epithelial cells play a key role in stimulating connective tissue healing through a FOXO1-dependent mechanism. Thus, FOXO1 and keratinocytes may be an important therapeutic target where healing is deficient or compromised by a fibrotic outcome.
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http://dx.doi.org/10.1038/srep42834DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5318899PMC
February 2017

NOD1 in the modulation of host-microbe interactions and inflammatory bone resorption in the periodontal disease model.

Immunology 2016 Dec 6;149(4):374-385. Epub 2016 Sep 6.

Department of Diagnosis and Surgery, School of Dentistry at Araraquara, Universidade Estadual Paulista (UNESP), Araraquara, SP, Brazil.

Periodontitis is a chronic inflammatory condition characterized by destruction of non-mineralized and mineralized connective tissues. It is initiated and maintained by a dysbiosis of the bacterial biofilm adjacent to teeth with increased prevalence of Gram-negative microorganisms. Nucleotide-binding oligomerization domain containing 1 (NOD1) is a member of the Nod-like receptors (NLRs) family of proteins that participate in the activation of the innate immune system, in response to invading bacteria or to bacterial antigens present in the cytoplasm. The specific activating ligand for NOD1 is a bacterial peptidoglycan derived primarily from Gram-negative bacteria. This study assessed the role of NOD1 in inflammation-mediated tissue destruction in the context of host-microbe interactions. We used mice with whole-genome deletion of the NOD1 gene in a microbe-induced periodontitis model using direct injections of heat-killed Gram-negative or Gram-negative/Gram-positive bacteria on the gingival tissues. In vitro experiments using primary bone-marrow-derived macrophages from wild-type and NOD1 knockout mice provide insight into the role of NOD1 on the macrophage response to Gram-negative and Gram-negative/Gram-positive bacteria. Microcomputed tomography analysis indicated that deletion of NOD1 significantly aggravated bone resorption induced by Gram-negative bacteria, accompanied by an increase in the numbers of osteoclasts. This effect was significantly attenuated by the association with Gram-positive bacteria. In vitro, quantitative PCR arrays indicated that stimulation of macrophages with heat-killed Gram-negative bacteria induced the same biological processes in wild-type and NOD1-deficient cells; however, expression of pro-inflammatory mediators was increased in NOD1-deficient cells. These results suggest a bone-sparing role for NOD1 in this model.
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http://dx.doi.org/10.1111/imm.12654DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5095495PMC
December 2016

Role of NOD2 and RIP2 in host-microbe interactions with Gram-negative bacteria: insights from the periodontal disease model.

Innate Immun 2016 11 22;22(8):598-611. Epub 2016 Sep 22.

1 Department of Diagnosis and Surgery, School of Dentistry at Araraquara-Univ Estadual Paulista (UNESP), Araraquara, SP, Brazil.

NOD2 is a member of the NLR family of proteins that participate in the activation of the innate immune response. RIP2 is a downstream kinase activated by both NOD1 and NOD2. There is scarcity of information regarding the relevance of NOD2 in periodontitis, a chronic inflammatory condition characterized by inflammatory bone resorption. We used NOD2-KO and RIP2-KO mice in a model of microbial-induced periodontitis. Heat-killed Aggregatibacter actinomycetemcomitans was injected in the gingival tissues three times/wk for 4 wk. Bone resorption was assessed by μCT analysis; osteoclasts were identified by immunohistochemical staining for TRAP and inflammation was assessed using a severity score system in H/E-stained sections. In vitro studies using primary macrophages assessed the response macrophages using qPCR-based array and multi-ligand ELISA. Bone resorption and osteoclastogenesis were significantly reduced in NOD2-KO mice. Severity of inflammation was not affected. qPCR-focused arrays and multi-ligand ELISA showed that expression of pro-inflammatory mediators was reduced in NOD2- and RIP2-deficient cells. RANKL-induced osteoclastogenesis was impaired in NOD2- and RIP2-deficient macrophages. We conclude that NOD2 is important for osteoclast differentiation and inflammatory bone resorption in vivo and also for the macrophage response to Gram-negative bacteria.
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http://dx.doi.org/10.1177/1753425916666652DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6525631PMC
November 2016

Diabetes and increased lipid peroxidation are associated with systemic inflammation even in well-controlled patients.

J Diabetes Complications 2016 Nov - Dec;30(8):1593-1599. Epub 2016 Jul 21.

Department of Diagnosis and Surgery, Araraquara School of Dentistry UNESP-Univ Estadual Paulista, Araraquara, São Paulo, Brazil.

Background: The effect of the interaction between type 2 diabetes and dyslipidemia on inflammation and lipid peroxidation (LPO) has not been assessed.

Aim: To investigate whether diabetes coupled with dyslipidemia alters oxidative metabolism leading to increased LPO products and inflammatory status.

Methods: 100 patients were divided into four groups based upon diabetic and dyslipidemic status: poorly controlled diabetes with dyslipidemia (DM-PC/D), well-controlled diabetes with dyslipidemia (DM-WC/D), normoglycemic individuals with dyslipidemia (NG/D), and normoglycemic individuals without dyslipidemia (NG/ND). Plasma was evaluated for an LPO product (MDA), antioxidant levels and inflammatory cytokines.

Results: Diabetics presented significantly higher levels of LPO (p<0.05) and the DM-PC/D had higher levels of proinflammatory cytokines and MDA in the plasma in comparison with normoglycemics (p<0.05). Interestingly IL1-β, IL-6, and TNF-α in DM-WC/D were not statistically different from those in DM-PC/D. Normoglycemic individuals with dyslipidemia presented significantly increased levels of IL-6 and TNF-α when compared to normoglycemic without dyslipidemia (p<0.05). MDA levels were also positively correlated with the presence of DM complications (r=0.42, p<0.01).

Conclusions: These findings show that dyslipidemia is associated with an increased inflammatory status, even in well-controlled diabetics and in normoglycemics. Our results suggest that lipid metabolism and peroxidation are important for the development of inflammation, which is elevated in several complications associated with diabetes.
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http://dx.doi.org/10.1016/j.jdiacomp.2016.07.011DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5120401PMC
March 2018

Sustained, localized salicylic acid delivery enhances diabetic bone regeneration via prolonged mitigation of inflammation.

J Biomed Mater Res A 2016 10 19;104(10):2595-603. Epub 2016 Jul 19.

Department of Biomedical Engineering, Rutgers, the State University of New Jersey, 599 Taylor Road, Piscataway, New Jersey.

Diabetes is a metabolic disorder caused by insulin resistance and/or deficiency and impairs bone quality and bone healing due to altered gene expression, reduced vascularization, and prolonged inflammation. No effective treatments for diabetic bone healing are currently available, and most existing treatments do not directly address the diabetic complications that impair bone healing. We recently demonstrated that sustained and localized delivery of salicylic acid (SA) via an SA-based polymer provides a low-cost approach to enhance diabetic bone regeneration. Herein, we report mechanistic studies that delve into the biological action and local pharmacokinetics of SA-releasing polymers shown to enhance diabetic bone regeneration. The results suggest that low SA concentrations were locally maintained at the bone defect site for more than 1 month. As a result of the sustained SA release, a significantly reduced inflammation was observed in diabetic animals, which in turn, yielded reduced osteoclast density and activity, as well as increased osteoblastogenesis. Based upon these results, localized and sustained SA delivery from the SA-based polymer effectively improved bone regeneration in diabetic animals by affecting both osteoclasts and osteoblasts, thereby providing a positive basis for clinical treatments. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 2595-2603, 2016.
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http://dx.doi.org/10.1002/jbm.a.35781DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7679602PMC
October 2016

Osteoblast Lineage Cells Play an Essential Role in Periodontal Bone Loss Through Activation of Nuclear Factor-Kappa B.

Sci Rep 2015 Dec 15;5:16694. Epub 2015 Dec 15.

Department of Periodontics, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA.

Bacterial pathogens stimulate periodontitis, the most common osteolytic disease in humans and the most common cause of tooth loss in adults. Previous studies identified leukocytes and their products as key factors in this process. We demonstrate for the first time that osteoblast lineage cells play a critical role in periodontal disease. Oral infection stimulated nuclear localization of NF-κB in osteoblasts and osteocytes in the periodontium of wild type but not transgenic mice that expressed a lineage specific dominant negative mutant of IKK (IKK-DN) in osteoblast lineage cells. Wild-type mice were also susceptible to bacteria induced periodontal bone loss but transgenic mice were not. The lack of bone loss in the experimental group was linked to reduced RANKL expression by osteoblast lineage cells that led to diminished osteoclast mediated bone resorption and greater coupled new bone formation. The results demonstrate that osteoblast lineage cells are key contributors to periodontal bone loss through an NF-κB mediated mechanism.
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http://dx.doi.org/10.1038/srep16694DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4678879PMC
December 2015