Functional Dynamics of Dendritic Cells in Response to Cutibacterium acnes Strains Associated with Healthy and Acne-prone Skin

The pathogenesis of acne vulgaris is multifactorial and is influenced by the presence of Cutibacterium acnes. This study investigated how different strains of C. acnes, associated with either healthy skin (CH) or acne-prone skin (CA), selectively modulate the function of three dendritic cell (DC) subtypes: Langerhans cell-derived (LCDC), monocyte-derived (moDCs), and myeloid (mDCs). Our findings revealed that all DC subtypes secreted varying levels of TGF-β, IL-1β, IL-6, IL-12p70, and IL-23 in response to C. acnes stimulation. Notably, moDCs exhibited the highest cytokine secretion in response to CA-ribotypes, indicating their potent immune responsiveness. Conversely, LCDCs were the least responsive, regardless of the ribotypes. Principal component (PCA) and gene ontology (GO) analysis of bulk RNA sequencing data of DCs exposed to C. acnes identified extensive transcriptional changes, particularly in immune response pathways. moDCs showed the most pronounced transcriptional changes, aligning with their high cytokine secretion levels. Additionally, we identified specific genes upregulated by CA-ribotypes, with notable differences among the DC types, highlighting the unique contributions of each DC subtype to the skin's immune defense mechanisms against C. acnes. Overall, our study underscores the complexity of DC responses in the skin's immune environment and provides valuable insights into their roles in acne. LCDC moDC and mDC cells have been stimulated with selected C. acne strains for 24 hours. The total RNA has been extracted to perform bulk RNA-sequencing and define the immune signatures unique to each DC cell type.