Actinic lentigines from Japanese and European volunteers share similar impaired biological functions

Abstract

Background: Hyperpigmented spots develop earlier and with a higher incidence in Asian individuals compared with Europeans. Although actinic lentigines (AL) are very common, the biological events underlying their formation remain ill-defined.

Objective: AL from Japanese volunteers were characterized through morphological and gene expression analyses. Data were then compared with published data on European volunteers.

Methods: AL on hands were selected through dermoscopic imaging and pattern scoring in Japanese women. Skin biopsies of AL and adjacent non-lesional (NL) skin were processed for histology and gene expression profiling. Japanese and European studies were compared after harmonizing the data using the same mathematical and statistical methods.

Results: Histologically, AL from Japanese individuals revealed deep epidermal invaginations with melanin accumulation in the depth of epidermal rete ridges. Transcriptomic data identified 245 genes differentially expressed in AL versus NL skin samples, associated with the different skin compartments and multiple functional families and biological processes, such as epidermal homeostasis, extracellular matrix organization and ion binding/transmembrane transport. Strikingly, melanogenesis-related genes were not significantly modulated in AL compared with NL skin. Comparison of the molecular profiles of Japanese and European AL showed that a huge majority of genes were modulated in the same way, recapitulating the overall biological alterations.

Conclusion: AL from Japanese volunteers exhibited morphological and molecular alterations of the whole skin structure with impairment of multiple biological functions similar to that found in European women. These findings will contribute to the development of efficient treatments of AL lesions.

Keywords: Melanocytes; Photoaging; Pigmentary disorders; Pigmentation.