Collagen I-discoidin domain receptor 1 signalling promotes inflammation development during keloid formation

BACKGROUND: Keloid is a chronic inflammatory skin disease, which is marked by abnormal fibroproliferative scar, without effective treatments. Many factors are involved in keloid formation, primarily highly activated inflammatory, wound tension, and hereditary susceptibility. Collagen signaling plays important roles in various diseases, including tumors and fibrotic diseases, but its function in keloid inflammation remains unknown. We aimed to study the roles and mechanisms of collagen signaling in the inflammation development during keloid formation. METHODS: Normal and keloid keratinocytes and fibroblasts were isolated from fresh normal skin and keloid tissues. Picrosirius red staining, Western Blotting, Q-PCR, co-immunoprecipitation, APEX2-mediated proximity biotinylation, Elisa, immunohistochemistry, and immunofluorescence assays were used to discover the roles of collagen-DDR1 signaling in the inflammation development. Human Keloid samples were subcutaneously transplanted to nude mice to building keloid xenograft model. The therapeutic potential of DDR1 inhibitor (7rh) and ARF6 inhibitor (NAV-2729) was examined in the keloid inflammation development. RESULTS: Both phosphorylated NFκB and STAT3 were obviously elevated in keloid tissues. Collagen I accounted for the vast majority of collagens in keloids. Collagen I signaling promoted keloid inflammation amplifier activation by DDR1. DDR1 and ARF6 were upregulated in keloid tissues, and the levels of both were positively correlated. In keloid dermal tissues, elevated DDR1 was mainly expressed in fibroblasts. Collagen I-DDR1 signaling activated NFκB and STAT3 signaling. DDR1 inhibitor (7rh) restrained keloid inflammation development and growth in keloid xenograft model. Mechanistically, DDR1 interacted with ARF6, which promoted the transport of DDR1 to plasma membrane and amplified collagen I-induced DDR1 signaling, then facilitated DDR1 binding to STAT3, leading to STAT3 phosphorylation. The combined inhibition of DDR1 and ARF6 synergistically inhibited keloid inflammation amplifier. CONCLUSIONS: Collectively, these findings reveal the molecular basis of collagen I-DDR1 signaling activating NFκB and STAT3 signaling and expose the role of ARF6-DDR1 axis in promoting keloid inflammation development, indicating that DDR1 and ARF6 may serve as innovative therapeutic targets in keloid.