IGF-1R deficiency in human keratinocytes disrupts epidermal homeostasis and stem cell maintenance

Background: Epidermal stem cells (ESCs) are keratinocytes that reside in the basal layer of the epidermis and mediate epidermal homeostasis. Insulin-like growth factor 1 (IGF-1) signaling through its receptor (IGF-1R) has been identified as an important regulator in rodent skin development and differentiation. However, the role of IGF-1/IGF-1R signaling in human keratinocytes is not yet well understood. Objective: This study aimed to clarify the role of IGF-1/IGF-1R signaling in human epidermal homeostasis. Methods: IGF-1R specific knockout (KO) HaCaT keratinocytes were generated by CRISPR-Caspase-9-mediated non-homologous end joining frame-shift mutations. Further, the behavior of these keratinocytes in epidermal homeostasis was investigated using reconstructed epidermis and human skin equivalents. Results: IGF-1R KO HaCaT keratinocytes were successfully established and produced thin epidermis in three-dimensional culture models. Keratin 10-positive cells were frequently found in the basal layer of the reconstructed epidermis. Conclusions: IGF-1/IGF-1R signaling was demonstrated to play a key role in maintaining human epidermal homeostasis. This method provides a new framework to investigate gene function in human epidermal homeostasis. (C) 2019 Japanese Society for Investigative Dermatology. Published by Elsevier B.V. All rights reserved.