Skin experiences persistent self-renewal; however, its functional decline starts with aging. Human skin aging can only be apprehended by acquiring in-depth knowledge of the molecular and functional properties of different skin cell types. 

A group of researchers conducted single-cell RNA sequencing of human eyelid skin derived from healthy individuals of various ages and recognized 11 canonical cell types, and 6 subpopulations of basal cells. Also, a progressive assemblage of photoaging-related modifications and increased chronic inflammation with age was observed. Transcriptional factors facilitating the developmental process were seen to undergo an early-onset decline with aging. Furthermore, aging was also shown to inhibit key transcription factors HES1 in fibroblasts and KLF6 in keratinocytes which compromised cell proliferation and increased inflammation and cellular senescence. The last observation indicated that the genetic activation of HES1 or pharmacological treatment with quercetin can ameliorate cellular senescence of dermal fibroblasts. 

Thus, this study established a single-cell molecular framework of human skin aging, furnishing a rich resource for designing therapeutic strategies against aging-related skin disorders.

Source: Zou Z, Long X, Zhao Q, et al. A single-cell transcriptomic atlas of human skin aging. Dev Cell. 2020;56(3):P383-397.e8.