Gene Expression Variation and Implant Wound Healing Among Smokers and Diabetics
Condition: Smoking; Diabetes
Study type: Observational

Summary: 
      Periodontal wound healing is a complex multifactorial process that involves interactions
      among various cells, growth factors, hormones and extracellular matrices. Although still
      poorly understood, these interactions trigger a series of events that lead to new tissue
      formation. One growth factor that plays an important role in wound healing is fibroblast
      growth factor 2 (FGF2). Many animal and human studies have shown this protein is effective in
      periodontal regeneration. Recently, epigenetic modifications, such as DNA methylation, have
      been associated with changes in patterns of gene expression. Preliminary data suggests that
      FGF2 gene may be differentially methylated in periodontal tissues. Aberrant gene promoter
      methylation in smokers and diabetics has also been reported in many studies. However, the
      role of DNA methylation in wound healing has not yet been investigated.

      The investigators hypothesize that the methylation status of FGF2 gene can affect the levels
      of FGF2 secreted during wound healing phase after dental implant surgery. The investigators
      also hypothesize there exists a difference in methylation levels of FGF2 gene in healthy,
      smoking and diabetic patients that can interfere with wound healing. The investigators seek
      to determine whether DNA methylation plays a role in wound healing and whether the
      methylation level of FGF2 gene varies among healthy, smoking and diabetic patients.
    

Detailed description: 
      Periodontal wound healing is a complex multifactorial process that involves interactions
      among various cells, growth factors, hormones and extracellular matrices. Although still
      poorly understood, these interactions trigger a series of events that lead to new tissue
      formation. One growth factor that plays an important role in wound healing is fibroblast
      growth factor 2 (FGF2). FGF2 is a member of the heparin-binding growth factor family,
      secreted by macrophages and endothelial cells. During the proliferative healing phase, it
      stimulates fibroblast proliferation & ECM synthesis, and increases chemotaxis, proliferation
      and differentiation of endothelial cells. During the bone remodeling phase, FGF2 also
      stimulates mesenchymal progenitor cell migration. Many animal and human studies have shown
      FGF2 are effective in periodontal regeneration. In 1999, Murakami showed surgically treated
      3-wall intrabony defect in dogs grafted with FGF2 was able to demonstrate significantly
      greater cementum and bone formation. Four years later, his group again found that topical
      application of rhbFGF in surgically treated class 2 furcation defects in dogs also showed
      increase in formation of PDL, cementum and bone. In 2008, Kitamura performed a randomized
      controlled study in humans with 2- or 3-wall intrabony periodontal defects and found that
      rhbFGF was able to stimulate alveolar bone growth and PDL regeneration.

      Recently, epigenetic modifications, such as DNA methylation, have been associated with
      changes in patterns of gene expression that do not involve changes in DNA sequence. DNA
      methylation is characterized by the addition of the methyl group onto cytokines within CpG
      regions. Methylated CpG regions interfere with the access of transcription factors to the
      promoter region, thereby silencing the gene. This DNA methylation phenomenon has important
      regulatory functions in normal and pathological cellular processes. It was recognized that
      alteration in the methylation states at the promoter regions of tumor suppressor genes are
      implicated with cancer. A persistent inflammation was also observed to cause DNA methylation,
      which inactivates suppressors of cytokine signaling and results in exaggerated cytokine
      production. This makes an individual susceptible to periodontal disease. In our laboratory,
      the investigators have discovered that periodontal disease is associated with increased DNA
      methylation of the COX-2 promotor, especially the locus immediately adjacent to the NF-kB in
      the promoter region. Preliminary data (not shown) suggests that FGF2 may be differentially
      methylated in periodontal tissues. Aberrant gene promoter methylation in smokers and
      diabetics has also been reported in many studies. However, the role of DNA methylation in
      wound healing has not yet been investigated.

      We hypothesize that the methylation status of FGF2 can affect the levels of FGF2 secreted
      during wound healing phase after dental implant surgery. We also hypothesize there exists a
      difference in methylation levels of FGF2 in healthy, smoking and diabetic patients that can
      interfere with wound healing. We seek to determine whether DNA methylation plays a role in
      wound healing and whether the methylation level of FGF2 varies among healthy, smoking and
      diabetic patients.
    

Intervention name(s): Dental implant surgery
Intervention type(s): Procedure
Intervention description(s): Surgery involving placement of one dental implant, of either Astra Tech or Straumann system, is performed in all subjects within 2 weeks of screening examination. Implant placement is 1-stage, but can be either on edentulous ridges or in extraction sockets.This is not a randomized treatment arm/group design. The study is observational with regards to the analysis of tissue samples that are collected prior to the routine placement of implants. The implant choice is based upon patient needs and is not related to any outcome.
Observational model: Cohort
Time perspective: Prospective
Sampling method: Non-Probability Sample
Study population: 
        Patients in the graduate periodontal clinic in the school of dentistry at the University of
        North Carolina
      
Biospecimen description: 
      Gingival tissues, gingival crevicular fluid, saliva
    
Keywords: DNA methylation; FGF2; Wound healing; Smoking; Diabetes; Implant