880 Single cell transcriptomics identifies elevated Th2 lymphocytes in the pathobiology of dominant dystrophic epidermolysis bullosa

Dominant dystrophic epidermolysis bullosa (DDEB) is caused by pathogenic variants in COL7A1, encoding type VII collagen which is essential for dermal-epidermal adhesion. Clinically, in DDEB there are trauma-induced blisters, milia and scarring but a major additional symptom is itch which can lead to prurigo-like papules. Precisely what causes itch in DDEB, however, has not been fully determined. We undertook bulk RNA-seq of affected (n=5) and unaffected (n=5) DDEB skin which revealed enriched Th1/2 and Th17 pathways compared to healthy skin (n=4). To link these pathways to specific cell types, we used scRNA-seq on affected (n=2) and unaffected (n=1) DDEB and healthy (n=2) skin. Intercellular communication analysis identified the MIF-CD74/CXCR4 axis as the most likely signaling association between keratinocytes and CD4+ T cells in DDEB cells (pval=0.00) but not in healthy cells. Pseudotime analysis showed the distinct separation of DDEB- and healthy-associated GATA3+Th2 subsets. Overrepresentation analysis of cluster-specific differentially expressed genes showed enrichment of glycolysis in DDEB-associated Th2 cells (FC=50.80, FDR=1.07E-2) but not control cells, underpinning the active state of DDEB Th2 cells. Treatment with dupilumab in one DDEB patient showed improved wound healing and reduced VAS itch scores after 12 weeks (VAS=3.5) compared to pre-treatment (VAS=8). Correlating with a good clinical response, bulk RNA-seq showed that healthy skin and dupilumab-treated DDEB skin show very similar transcriptomic profiles, including reduced Th1/2 and Th17 pathway enrichment. Thus, scRNA-seq helps define an enhanced DDEB-associated Th2 profile and rationalizes drug repurposing of anti-Th2 drugs, such as dupilumab, in treating DDEB.