An In Vivo Model for Postinflammatory Hyperpigmentation
Condition: Post-inflammatory Hyperpigmentation
MeSH terms: Hyperpigmentation
Study type: Interventional

Summary: 
      Post-inflammatory hyperpigmentation (PIH) is an acquired hypermelanosis that occurs after
      cutaneous inflammation or injury that frequently affects darker skinned populations.
      Previously, a model of 35% TCA-induced PIH was validated against acne induced PIH, which has
      value in product testing for the treatment of PIH. In this second phase of the study, the
      investigators would like to determine if a lower concentration of TCA-induced PIH is
      comparable to acne-induced PIH.
    

Detailed description: 
      Post-inflammatory hyperpigmentation (PIH) is an acquired hypermelanosis that occurs after
      cutaneous inflammation or injury. This process can occur in all skin types but more
      frequently affects darker skinned patients, such as African-Americans, Hispanics, Asians,
      Native Americans, Pacific Islanders and those of Middle Eastern descent. PIH can occur after
      infection, allergic reactions, contact dermatitis, some medications, burns, following
      procedures, or inflammatory disease such as acne. In skin of color, PIH frequently occurs in
      resolving acne lesions and can persist for months after the acne lesion itself has
      disappeared. In many cases, the resulting PIH can be more distressing than the original
      insult.

      During the first phase of this study, the investigators investigated the clinical,
      spectroscopic and histologic characteristics of acne-induced PIH versus irritant induced PIH
      using Trichloroacetic acid (TCA), 35% solution. From this initial study, the investigators
      concluded that the similarity of Investigator's Global Assessment scores, and spectroscopic
      measurements using Diffuse Reflectance Spectroscopy and Colorimetry in both acne and
      TCA-induced PIH at Day 28 suggest that TCA-induced PIH could be a reproducible model for acne
      induced PIH.

      MicroRNAs (miRNAs) are a class of small non-coding RNA molecules that regulate the expression
      of multiple genes at the post-transcriptional level through degradation and translation of
      target mRNAs. In the initial study, the investigators hypothesized that miRNAs derived from
      melanocytes and immune cells during PIH development could be detected in tissue and serve as
      novel biomarkers for PIH and making appropriate therapeutic decisions. To test this
      hypothesis, the investigators first examined miRNA gene expression profiles during PIH
      development using different models, and then evaluated miRNAs profiles in acne- induced PIH,
      TCA- induced PIH and normal skin. The investigators have defined some miRNAs that potentially
      are involved in PIH development and may be also serve as the biomarkers for PIH. The
      investigators found that there were 19 miRNA changes in acne-induced PIH versus normal skin,
      while 43 miRNA changes in TCA-inducedPIH versus normal skin. Interestingly, about 80% changed
      genes in acne were included in TCA-mediated miRNA changes, suggesting TCA can partially mimic
      acne-PIH.

      Overall, this initial model for PIH, using TCA, serves as a foundation to better understand
      and improve our ability to manage PIH. In this next phase of the study, the investigators
      will refine this in vivo model for PIH by determining the optimal concentration of TCA to
      induce PIH.
    

Intervention name(s): Tricholoacetic Acid (TCA)
Intervention type(s): Drug
Intervention description(s): We will be applying 4 concentrations of TCA (20%, 25%, 30%, 35%) to the buttocks to two spots each (total of 8 lesions) and following characteristics of these lesions and comparing them to acne induced PIH during the course of the study.
Intervention model: Single Group Assignment
Masking: None (Open Label)
Primary purpose: Other