Real-time polymerase chain reaction analysis of a 3895-bp mitochondrial DNA deletion in epithelial swabs and its use as a quantitative marker for sunlight exposure in human skin

Abstract

Background: The use of mitochondrial DNA (mtDNA) damage as a reliable and highly sensitive biomarker of ultraviolet (UV) radiation exposure in both the dermis and epidermis has now been well developed by our group and others. We have previously identified a 3895-bp mtDNA deletion which occurred more frequently and to a higher level in usually sun-exposed skin as opposed to occasionally sun-exposed skin. This work focused on older-aged individuals and, in particular, perilesional, histologically normal skin biopsies taken from patients with skin cancer.

Objectives: To develop novel, less-invasive methods of obtaining skin samples (i.e. epidermis) from volunteers covering a much wider age range and larger number of individuals (n = 239).

Methods: The 3895-bp deletion was quantified by a specific real-time polymerase chain reaction assay in normal human epidermis samples taken from three body sites with differing sun exposure.

Results: The results show a statistical increase of the level of the 3895-bp deletion with increasing sun exposure in the epidermal swabs of human skin (P < 0·001) and with increasing age of the donor in the needle biopsy samples.

Conclusions: These data suggest that the upper layers of the epidermis are an accessible and reliable site for assessing mtDNA damage caused by UV exposure.