Sensory neuron-derived TAFA4 promotes macrophage tissue repair functions

Inflammation is a defence response to tissue damage that requires tight regulation in order to prevent impaired healing. Tissue-resident macrophages have a key role in tissue repair(1), but the precise molecular mechanisms that regulate the balance between inflammatory and pro-repair macrophage responses during healing remain poorly understood. Here we demonstrate a major role for sensory neurons in promoting the tissue-repair function of macrophages. In a sunburn-like model of skin damage in mice, the conditional ablation of sensory neurons expressing the G alpha(i)-interacting protein (GINIP) results in defective tissue regeneration and in dermal fibrosis. Elucidation of the underlying molecular mechanisms revealed a crucial role for the neuropeptide TAFA4, which is produced in the skin by C-low threshold mechanoreceptors-a subset of GINIP(+) neurons. TAFA4 modulates the inflammatory profile of macrophages directly in vitro. In vivo studies in Tafa4-deficient mice revealed that TAFA4 promotes the production of IL-10 by dermal macrophages after UV-induced skin damage. This TAFA4-IL-10 axis also ensures the survival and maintenance of IL-10(+)TIM4(+) dermal macrophages, reducing skin inflammation and promoting tissue regeneration. These results reveal a neuroimmune regulatory pathway driven by the neuropeptide TAFA4 that promotes the anti-inflammatory functions of macrophages and prevents fibrosis after tissue damage, and could lead to new therapeutic perspectives for inflammatory diseases.