Intrinsic versus Extrinsic Aging: A Histopathological, Morphometric and Immunohistochemical Study of Estrogen Receptor β and Androgen Receptor.

Skin is a target organ of sex steroids which play important roles in skin health and disease. The aim of this study is to investigate the expression of estrogen receptor β (ERβ) and androgen receptor (AR) in human skin from different age groups for a better understanding of the hormonal regulation of skin aging. Using standard immunohistochemical techniques, biopsies of sun-unprotected and sun-protected skin were taken from 60 normal subjects. Sun-protected skin showed significantly higher immunoreactivity for ERβ and AR compared to sun-unprotected skin of all age groups. Significantly higher ERβ H score and percent of expression were associated with the 20-35 years age group compared to the groups that were 35-50 years and >50 years old (p < 0.02, p = 0.03, respectively) in sun-unprotected and sun-protected skin (p < 0.001, p = 0.01, respectively). AR H score showed a negative correlation with age (p = 0.04) with no significant difference in immunoreactivity in different age groups, either in sun-unprotected or sun-protected skin. There was also a significant correlation between ERβ H score and epidermal thickness in sun-unprotected (p = 0.04) and sun-protected skin (p = 0.04) in studied subjects regardless of age. The same relationships did not reach significance with AR expression. However, a significant positive correlation was detected between H scores and percent of expression of ERβ and AR in sun-unprotected (p = 0.01, p = 0.02, respectively) and sun-protected skin (p = 0.005, p = 0.02, respectively) regardless of age. In conclusion, both ERβ and AR decline gradually with intrinsic and extrinsic aging. This decline is more obvious with extrinsic aging. Further large-scaled studies are recommended to expand, validate and translate current findings to clinically significant, diagnostic and therapeutic applications. Molecular studies to investigate the probable ligand-independent action of both receptors are warranted. In addition, their gene expression patterns and associated signaling and metabolic pathways can also be tackled to provide a basis for further interventions in pathological processes that involve their dysregulation.