Label-free Raman imaging defines distinct cell populations in human skin

Understanding cellular heterogeneity in human skin is crucial for regenerative medicine and tissue engineering. In this study, we applied label-free Raman imaging to visualize molecular features corresponding to the three-dimensional architecture of the epidermis. Spatially resolved Raman spectra, combined with multivariate data analysis, enabled the identification of cell-layer–specific molecular signatures. Based on the region-specific spectra analysis, component C5 was predominantly localized to the basal layer within rete ridges and was characterized by β-sheet–enriched keratin features. This spatially restricted distribution reflects the molecular microenvironment of epidermal stem cell niches, suggesting that C5 may serve as a biomarker for basal stem cell populations associated with skin undulations. These findings provide insight into the molecular basis of epidermal architecture and demonstrate the potential of Raman spectroscopy as a label-free tool for evaluating stem cell localization and differentiation status.