Single-cell transcriptomics of human-skin-equivalent organoids.

Area of Science:

• Dermatology and regenerative medicine
• Organoid technology and single-cell analysis
• Skin biology and tissue engineering

Background:

• Human skin-equivalent (HSE) organoids are valuable tools for studying skin biology.
• Existing HSE models lack comprehensive characterization, limiting their utility.
• Understanding HSE cellular states and differentiation is crucial for improving models.

Purpose of the Study:

• To comprehensively characterize in vitro and xenograft human skin-equivalent (HSE) organoid cultures.
• To compare HSEs with in vivo human epidermis using single-cell transcriptomics.
• To identify limitations and areas for innovation in skin organoid models.

Main Methods:

• Single-cell transcriptomics (scRNA-seq) to analyze cellular composition and gene expression.
• Differential gene expression analysis to identify distinct cell populations.
• Pseudotime analysis and spatial localization to reconstruct differentiation trajectories.
• Cell-cell communication modeling to infer signaling pathway interactions.
• Comparison of in vitro HSEs, xenograft HSEs, and in vivo epidermis.

Main Results:

• HSE keratinocyte differentiation trajectories largely recapitulate in vivo epidermal pathways.
• HSEs contain major in vivo cellular states but also exhibit unique keratinocyte states.
• Organoid models show an expanded basal stem cell program and disrupted terminal differentiation.
• Aberrant epithelial-to-mesenchymal transition (EMT)-associated signaling pathways were identified in HSEs, modulated by epidermal growth factor (EGF).
• Xenograft HSEs showed improved characteristics compared to in vitro HSEs, with early transplantation rescuing deficits but inducing a hypoxic response.

Conclusions:

• Human skin-equivalent organoids offer a powerful system for studying skin biology but possess distinct limitations.
• Unique cellular states and disrupted differentiation pathways in HSEs highlight areas for model improvement.
• Xenografting and growth factor supplementation show potential for enhancing HSE fidelity.
• This research provides critical insights into the strengths and weaknesses of current skin organoid technology, guiding future innovations.