Keratinocyte and myeloid MCPIP1 have distinct roles in maintaining skin homeostasis.

The skin is a complex organ, and the intricate network between keratinocytes and immune cells is critical for ensuring skin function. Monocyte chemotactic protein-1-induced protein 1 (MCPIP1) is a ribonuclease that functions as a key negative modulator of inflammation. We previously reported that conditional deletion of MCPIP1 in keratinocytes (Mcpip1) impairs skin integrity in adult mice. A similar phenotype was observed following the depletion of MCPIP1 in the myeloid compartment (Mcpip1). The aim of this study was to develop a keratinocyte and myeloid double-MCPIP1 knockout mouse model to clarify the specific roles of myeloid and epidermal MCPIP1 in skin biology. Histological analyses indicated that the skin morphology changed after depletion of MCPIP1 in cells of myeloid origin as well as in keratinocytes. The thicknesses of the epidermal and subcutaneous fat layers increased in the mice with a loss of epidermal MCPIP1, whereas the loss of myeloid MCPIP1 had the opposite effect. In addition, both types of mice showed opposite responses to stimulation with 12-O-tetradecanoylphorbol-13-acetate. Transcriptomic profiling of whole-skin lysates revealed some common target transcripts in all the knockout mice. Further analyses revealed that distinct pathways are modulated following the loss of epidermal or myeloid MCPIP1. The skin morphology and inflammatory phenotype of keratinocyte and myeloid double-MCPIP1 knockout mice resembled those of mice with only keratinocyte-specific knockout of MCPIP1. Overall, myeloid and epidermal MCPIP1 play important but distinct roles in the modulation of skin-related processes.