Ann Dermatol.  2020 Apr;32(2):101-108. 10.5021/ad.2020.32.2.101.

Exploratory Study of Epidermis, Basement Membrane Zone, Upper Dermis Alterations and Wnt Pathway Activation in Melasma Compared to Adjacent and Retroauricular Skin

Affiliations
  • 1Department of Dermatology and Radioterapy, Botucatu School of Medicine, São Paulo State University, Botucatu, Brazil. heliomiot@fmb.unesp.br
  • 2Department of Patology, Botucatu School of Medicine, São Paulo State University, Botucatu, Brazil.

Abstract

BACKGROUND
Melasma is a chronic acquired focal hypermelanosis which pathogenesis has not been fully elucidated. Classical pathophysiologic studies have analysed the affected and perilesional areas, but little is known about the status of sun-protected skin, which is subjected to the same endogenous and genetic factors.
OBJECTIVE
To assess the histological characteristics of melasma compared to adjacent and retroauricular skin.
METHODS
Skin samples were collected from 10 female from: melasma, perilesional area and retroauricular. The samples were stained (haematoxylin-eosin, periodic acid-Schiff, Fontana-Masson, picrosirius red, toluidine blue and Verhoeff), immunolabelled for CD34 and Wnt1. The data from the skin sites were analysed simultaneously by a multivariate model.
RESULTS
Melasma skin exhibited noteworthy stratum corneum compaction, greater collagen heterogeneity, solar elastosis, higher number of mast cells, basement membrane zone (BMZ) damage, Wnt1 expression, pendulum melanocytes, higher cellularity and vascular proliferation at the superficial dermis. Stratum corneum compaction, collagen heterogeneity and BMZ abnormalities were variables associated to melasma that not follow a continuum through retroauricular to adjacent skin. Mast cell count was the variable that disclosed correlation with the most other abnormalities as well as had the greater contribution in the multivariate model.
CONCLUSION
In addition to melanocyte hyperactivity, melasma skin exhibits alterations in the epidermal barrier, upper dermis and BMZ, which differ from the adjacent sun-exposed skin and retroauricular skin, indicating a distinct phenotype, rather than a mere extension of photoageing or intrinsic ageing. Mast cells appear to play a central role in the physiopathology of melasma.

Keyword

Basement membrane; Dermis; Epidermis; Melanosis

MeSH Terms

Basement Membrane*
Collagen
Dermis*
Epidermis*
Female
Humans
Hyperpigmentation
Mast Cells
Melanocytes
Melanosis*
Phenotype
Population Characteristics
Skin*
Tolonium Chloride
Wnt Signaling Pathway*
Collagen
Tolonium Chloride
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