Table 3.
Compilation of studies with human skin exposed to UV radiation and DNA methylation
| Country, Year [Reference] | Study Design | Groups | Tissue/Cell Lines | UV Radiation Exposition | Methylation Type | Technique | Outcome and Conclusion | Other Outcomes |
|---|---|---|---|---|---|---|---|---|
| Germany, 2010 [47] | Comparison of sun-exposed and non-exposed body areas of healthy individuals | 30 volunteers (10 suction blisters for male individuals; 20 punch biopsies for female individuals) | Dermal and epidermal cells from outer forearm and inner arm regions | Lifelong solar radiation | Genome-wide and site-specific | Human Methylation 27 BeadChip; BS (KRT75, SEC31L2, DDAH2, TET2) |
Hypomethylation in chronically-exposed epidermis; hypomethylation of KRT5; ↑ expression levels of KRT5; hypermethylation of SEC31L2 | ≠ methylation profiles in male and female skin; age-related hypermethylation in 104 markers; hypermethylation of DDAH2 and TET2; ≠ methylation profile between dermis and epidermis |
| Sweden, 2015 [48] | Effect of phototherapy upon the skin methylation profile of patients with psoriasis | 24 individuals divided into 2 groups: psoriasis patients (n = 12) and healthy subjects (n = 12, control group) | Epidermis cells obtained from punch biopsies | Whole body narrow band (311–312 nm) UVB light irradiation in a cabinet equipped with fluorescent lamps (UVB TL100W/01, Philips); 24 sessions in for 2–3 months | Genome-scale | Human Methylation 450 | Hypomethylation on psoriasis group; after phototherapy, the methylation profile was similar to that of the healthy group. | Altering in the methylation profile was associated with a better response to treatment. |
| USA, 2015 [49] | Comparison of sun-exposed and non-exposed areas of the body in healthy and skin cancer patients | 36 individuals <35 and >60 years old divided into 2 groups: healthy subjects (n = 26) and squamous cell carcinoma (SCC) patients (n = 10) | Dermis and epidermis cells obtained by punch biopsies of the arm (upper inner arm) and face (outer forearm or lateral epicanthus) | Lifelong solar radiation | Genome-scale | Human Methylation 450; WGBS | Hypomethylation blocks throughout the genome in sun-exposed regions, mainly in older individuals. | Hypomethylation in sun-exposed regions of healthy volunteers was similar to the profile of individuals with SCC. |
| Brazil, 2015 [50] | Comparison of sun-exposed and non-exposed areas of the body | Corpses of both genders, over 30 years old and with healthy skin (n = 28) | Skin punch biopsies (dermis + epidermis) from the inner arm or outer forearm | Lifelong solar radiation | Site-specific | MSP (MMP9, miR-137, KRT14); MSRE (KRT19) | No difference was detected between exposed and non-exposed regions | Methylated profile of miR-137 seemingly more frequent in women |
| Brazil, 2017 [51] | Comparison of sun-exposed and non-exposed areas of the body | Corpses from both genders, ranging from 18–89 years old and with healthy skin (n = 24) | Skin punch biopsies (dermis + epidermis) from the inner arm or outer forearm | Lifelong solar radiation | Global and site-specific. | ELISA; MSP (miR-9-1, miR-9-3, MTHFR) | No difference was detected between exposed and non-exposed regions | global methylation levels > global hydroxymethylation levels |
BS: Bisulfite sequencing; WBSG: Whole-genome bisulfite sequencing; MSP: Methylation specific PCR; MSRE: Methylation sensitive restriction enzyme; ELISA: Enzyme-linked immunosorbent assay.