The Molecular Anatomy of Oral Wound Healing
Condition: Wounds and Injuries; Wound Healing; Ulcer
MeSH terms: Wounds and Injuries
Study type: Observational

Summary: 
      Background:

        -  Two important properties distinguish the healing process of skin wounds from that of
           wounds of the mucous membranes of the mouth (oral mucosa). Although the skin and the
           oral mucosa tissues are similar in nature, oral mucosa have more rapid healing and a
           lack of scar tissue formation. However, oral wound healing in general has been poorly
           studied, and more information is needed to determine how specific aspects of the oral
           environment affect the healing process.

        -  Researchers are interested in identifying various factors that contribute to oral wound
           healing. Studying this process would help researchers explore procedures to accelerate
           the healing of critically-sized oral lesions formed by trauma, surgery, radiation
           therapy, infection, and other damage to the mouth. In addition, research into scar-free
           healing could be applied to other mucosal sites to promote healing and minimize
           unsightly scars that may compromise the tissue.

      Objectives:

      - To identify the specific factors that enable rapid and nearly scar-free healing of oral
      mucosa.

      Eligibility:

        -  Healthy male volunteers between 18 and 40 years of age.

        -  Regular cigarette, cigar, and pipe smokers; occasional smokers who smoke more than 1 day
           a week or have smoked in the prior month; users of chewing tobacco or betel nut; and
           heavy drinkers (three or more alcoholic drinks per day) will be excluded.

      Design:

        -  Participants will have a medical history and examination, and will provide blood samples
           at the start of the study.

        -  Participants will provide oral mucosa samples from the inside of the cheek, taken using
           a dermal punch. At the same time, participants will provide skin biopsy samples of
           approximately the same size. After the skin and oral mucosa samples are taken,
           participants will be divided into three groups for follow-up procedures.

        -  Group 1: No further samples will be collected. This group will help document the normal
           healing process.

        -  Group 2: A second, slightly larger biopsy, which will include the area of the first
           biopsy, will be taken on day 3. Both skin and oral mucosa biopsies will be taken.

        -  Group 3: A second, slightly larger biopsy will be taken on day 6, in a similar way as
           described for Group 2. Both skin and oral mucosa biopsies will be taken.

        -  Wounds will be photographed with a digital camera on days 3, 6, 9, 13, and 15; and the
           healing will be monitored at the scheduled clinic visits.
    

Detailed description: 
      BACKGROUND:

      Two important properties distinguish the process of healing of oral mucosa wounds from those
      of the skin: more rapid healing and the absence of scar tissue formation. This is remarkable
      given the apparent similarities of the two tissues. There are, however, prominent differences
      in the healing environment, such as hydration, growth factor availability, inflammatory
      response, and microbial exposure. Knowledge as to the causal contribution of each of these
      factors to the differential healing response of the two epithelia is mostly anecdotal, and
      oral wound healing has generally been poorly studied. This study seeks to provide a global
      molecular definition of oral wound healing in comparison to that of the skin. The overall aim
      will be to identify the specific factors that enable rapid and nearly scar-free healing of
      oral mucosa. Identification of these physiological and molecular determinants will have
      widespread implications for human oral health. Among others, it would provide venues for the
      targeted exploration of procedures to accelerate the healing of critically-sized oral lesions
      formed by trauma, surgery, radiation therapy, infection, and other oral pathologies, which,
      if untreated, lead to permanent disability and dysfunction. Moreover, pathways and/or
      molecules identified in these studies which may facilitate rapid, scar-less healing could be
      considered for application to non-oral mucosal sites to promote healing and minimize
      unsightly scars, which may also compromise the functional integrity of the tissue.

      Hypotheses:

        -  There are significant differences in gene and protein expression between wound healing
           in skin and oral mucosa.

        -  The recruitment of inflammatory cells associated with a large up-regulation of
           inflammation-associated genes, including cytokines and chemokines, in the epithelial
           cells of skin wounds may account for these differences.

        -  There are specific gene programs that can explain the presence of significant scarring
           in skin tissues but not in oral mucosa.

      OBJECTIVES:

      The overall objective of this pilot study proposal is to establish the gene and protein
      expression profiles during the early stages (1-6 days) of normal oral wound repair. By
      comparing these profiles with those of cutaneous wound healing, we may be able to identify
      molecules exclusive to oral wound repair that could represent biomarkers of the healing
      process or serve as new therapeutic targets in pathological wound healing and cancer. One
      specific hypothesis to be tested is that the level of expression of pro-inflammatory gene
      networks by wound-infiltrating keratinocytes constitutes the most significant difference
      between the human oral and cutaneous wound transcriptomes. The specific hypothesis has been
      developed from data obtained from our recent complementary oral and skin wound healing
      studies in animals.

      ELIGIBILITY:

      Healthy male volunteers age 18 to 40 will be enrolled in this study.

      DESIGN:

      Oral mucosa samples: A sterile 3-mm dermal punch will be used to create uniform,
      full-thickness biopsy in the mucosa of the cheek just above the occlusal plane. Circular
      pieces of tissue of approximately 2 mm in depth will be removed on the day of biopsy (day 1).
      These subjects will be subsequently be randomly grouped as follows:

      Group 1: no further samples will be collected; pictures will be taken on days 3, 6, 9, 13,
      and 15 (see Timetable). This group will help document the normal healing process under the
      conditions of the present study, including the lack of scaring in the area selected for the
      initial wound in the oral mucosa as compared with the skin.

      Group 2: a second biopsy will be taken on day 3, which will include the area of the first
      biopsy with sterile 5 mm punch, following the same procedure as described for day 0; pictures
      will be taken according to the schedule set in the Timetable. This second biopsy will enabled
      sampling the healing area induced by the first biopsy. By selecting a punch size two
      millimeters wider and taking a sample concentric to the first one, we can assure complete
      removal of the area of interest.

      Group 3: a second biopsy will be taken on day 6, respectively, in a similar way as described
      for Group 2; pictures will be taken according to the Timetable.

      Skin samples: In parallel to the oral biopsies, skin biopsies of similar size and depth as
      the oral biopsy from the same subjects will be obtained from the axillary region following
      the same schedule and procedure, including a second biopsy for groups 2 and 3.

      Wounds will be photographed with a digital camera and the healing monitored at clinic visits
      per schedule above. The excised tissues in each case will be immediately bisected on ice;
      half of the sample will be fixed in 4% formaldehyde/PBS and embedded in paraffin for standard
      histology and immunohistochemistry, and the remaining half will be placed in OCT-filled
      plastic base molds, flash frozen in liquid nitrogen, and stored at 80 (Infinite)C until
      processed for genomic and proteomic analysis.
    

Time perspective: Prospective
Keywords: Wound Healing; Oral Wounds; Cutaneous Wounds; Gene Array Analysis; Proteomic Analysis; Healthy Volunteer; HV