Role of MyD88 signaling in the imiquimod-induced mouse model of psoriasis: focus on innate myeloid cells.

ABSTRACT: Psoriasis is a chronic skin disease associated with deregulated activation of immune cells and keratinocytes. In this study, we used the imiquimod (IMQ)-induced mouse model of psoriasis to dissect better the contribution of hematopoietic and skin-resident stromal cells to psoriasis development. The comparison of disease development in mice carrying the hematopoietic cell-specific deletion of MyD88 (Myd88^fl/flVav-cre⁺ mice) with mice carrying the total MyD88 deficiency (Myd88^-/- mice), we show that the progression of skin and systemic inflammation, as well as of epidermal thickening, was completely dependent on MyD88 expression in hematopoietic cells. However, both Myd88^-/- mouse strains developed some degree of epidermal thickening during the initial stages of IMQ-induced psoriasis, even in the absence of hematopoietic cell activation and infiltration into the skin, suggesting a contribution of MyD88-independent mechanisms in skin-resident stromal cells. With the use of conditional knockout mouse strains lacking MyD88 in distinct lineages of myeloid cells (Myd88^fl/flLysM-cre⁺ and Myd88^fl/flMRP8-cre⁺ mice), we report that MyD88 signaling in monocytes and M?, but not in neutrophils, plays an important role in disease propagation and exacerbation by modulating their ability to sustain ?? T cell effector functions via IL-1? and IL-23 production. Overall, these findings add new insights into the specific contribution of skin-resident stromal vs. hematopoietic cells to disease initiation and progression in the IMQ-induced mouse model of psoriasis and uncover a potential novel pathogenic role for monocytes/M? to psoriasis development.

SUBMITTER: Costa S 

PROVIDER: S-EPMC6608051 | biostudies-literature | 2017 Sep

REPOSITORIES: biostudies-literature