# Spatially Resolved Proteomic Mapping in Skin Organoid for Hair Follicle Development

## TL;DR

This study maps protein changes in skin organoids to understand how hair follicles develop and mature over time.

## Contribution

A spatiotemporal proteomic map of hair follicle development in skin organoids is presented.

## Key findings

- Stage-specific proteins involved in RNA processing and lipid metabolism are active during hair germ and peg formation.
- Keratinization and extracellular matrix proteins are prominent during hair follicle maturation.
- Abnormal expression of CSNK1A1 and SFN is linked to cicatricial alopecia, highlighting their role in hair follicle development.

## Abstract

Hair follicle development is a complex, highly regulated process involving interactions between epithelial and mesenchymal cells. However, the specific molecular mechanisms and important biological processes of hair follicle development remain poorly understood. How the extracellular matrix is involved in the hair follicle formation from hair germs remains to be investigated. In this study, we applied spatially resolved proteomic mapping to investigate the process of hair follicle development in skin organoids at different stages: D55, D75, D90, D140, D150, and D170, which corresponds to that from hair germ formation to hair follicle aging. Our analysis identified dynamic changes in protein expression and active protein synthesis during hair follicle appearance. We observed stage-specific protein expression patterns, with hair germ and hair peg formation, enriched in proteins involved in RNA processing and lipid metabolism. Meanwhile, hair follicle initial and full maturation highlighted proteins related to keratinization and extracellular matrix organization. Notably, trend proteins involved in keratinization and neuron–neuron synaptic transmission were upregulated from hair germ formation to the hair follicle appearance. We also found that CSNK1A1 and SFN exhibit abnormal expression in the hair follicles of patients with cicatricial alopecia, which further proves the role of CSNK1A1 and SFN in the normal development of hair follicles. The results provide a comprehensive spatial proteomic map of hair follicle development and offer new insights into the biological process driving hair follicle formation and maturation. These findings may guide future therapeutic strategies for hair regeneration and the treatment of hair disorders.

•Spatiotemporal proteome map of hair follicle development in skin organoids.•Identification of stage-specific proteins and dynamic proteomic changes.•Clarification of key molecular processes involved in hair follicle development.

Spatiotemporal proteome map of hair follicle development in skin organoids.

Identification of stage-specific proteins and dynamic proteomic changes.

Clarification of key molecular processes involved in hair follicle development.

We applied spatially resolved proteomic mapping to study hair follicle development in skin organoids at different stages: hair germ formation, hair peg formation, hair follicle appearance, hair follicle initial maturation, hair follicle full maturation, and hair follicle aging. Stage-specific proteins and dynamic changes of proteins in a time series of hair follicle development were identified to clarify key molecular mechanisms involved in hair follicle formation and maturation.