Applied Cosmetic Science and Technology Applied Cosmetic Science and Technology

The epidermis, the outermost layer of the skin, is constantly exposed to temperature fluctuations from both external and internal sources, which can disrupt epidermal barrier function and homeostasis. Keratinocyte stem cells in the basal layer of the epidermis are also influenced by these temperature changes. A recent study has demonstrated that changes in the temperature microenvironment modulate intracellular Ca²⁺ levels in cultured human epidermal keratinocyte stem cells via temperature-sensitive transient receptor potential (TRP) channels, which subsequently influence epidermal stemness through the regulation of mechanistic target of rapamycin 1 (mTORC1) signaling. These findings provide new insights into how temperature fluctuations contribute to the dysregulation of epidermal homeostasis and suggest a previously unrecognized mechanism by which thermal stimuli affect skin biology at the cellular level. This review summarizes the effects of temperature on epidermal homeostasis and highlights the roles of temperature-sensitive TRP channels in epidermal keratinocytes, as well as the thermosensitivity of human keratinocyte stem cells. A comprehensive understanding of how epidermal keratinocytes and their stem cells perceive and respond to temperature fluctuations via temperature-sensitive TRP channels is crucial for elucidating the mechanisms underlying epidermal homeostasis and its disruption in conditions such as atopic dermatitis. Furthermore, these insights may inform strategies to mitigate the impact of temperature fluctuations associated with climate change on skin health.