Loss of epidermal miR-149 sensitizes to skin inflammation

Keratinocytes play a central role in amplifying skin inflammation in psoriasis and atopic dermatitis (AD). However, the epithelial-intrinsic regulators involved in responsiveness to inflammatory cues remain poorly defined. MicroRNAs are fundamental regulators of gene expression.

We sought to define the role of miR-149 in keratinocyte immune functions in healthy skin and chronic inflammatory skin diseases.

Keratinocyte-specific Mir149-knockout mice (Mir149^EKO) were generated. Experimental AD (ovalbumin) and psoriasis (IL-23/imiquimod) models were performed, followed by severity scoring, quantitative PCR, RNA sequencing, immunohistochemistry, single-cell RNA sequencing, and flow cytometry. Chemokine array was performed on keratinocyte supernatants. In mice, in vivo TNF-related weak inducer of apoptosis (Tweak) antibody blockade was performed. Ex vivo skin biopsy samples from patients with psoriasis and allergic contact dermatitis were injected with synthetic miR-149.

Mir149^EKO mice exhibited a preinflammatory transcriptional state. In both AD and psoriasis models, Mir149^EKO mice developed exaggerated skin inflammation with epidermal thickening and increased immune infiltration with mast cell accumulation. miR-149 represses the TNF receptor family member Tweakr, and its loss led to enhanced Tweak-induced NF-κB activation and chemokine production. Single-cell RNA sequencing revealed expansion of activated basal keratinocytes enriched for Tweak-responsive chemokines and immune cell accumulation in Mir149^EKO skin. Antibody-mediated neutralization of Tweak strongly attenuated enhanced inflammation in vivo. Notably, the miR-149/TWEAKR axis is dysregulated in human psoriasis and AD. Ex vivo delivery of synthetic miR-149 to inflamed skin suppressed inflammatory mediators.

miR-149 acts as a fundamental brake on epithelial-immune interactions, and its loss in AD and psoriasis can lead to amplification of keratinocyte inflammatory responses.