Fibroblast-directed melanocyte recruitment via Cxcl12-Cxcr4 cascade promotes post-inflammatory hyperpigmentation and skin barrier protection in zebrafish

Post-inflammatory hyperpigmentation (PIH), a prevalent dermatological condition, is classically attributed to melanocyte overactivation in situ. However, the precise triggers and physiological significance of melanocyte responses remain elusive. Using an acetic acid corrosion-induced zebrafish PIH model, here we demonstrate that melanocyte migration to the inflammatory site is a key pathogenic driver of hyperpigmentation. This migration is largely orchestrated by fibroblasts, but not macrophages or neutrophils, which secrete the chemokine cxcl12a upon injury, recruiting melanocytes via the cxcl12a-cxcr4a signaling axis. Beyond hyperpigmentation, we reveal that melanocytes function as a dual protective barrier against both UV-induced DNA damage and microbial invasion in response to acetic acid corrosion-induced injury. Our findings provide new insights into PIH pathogenesis and uncover the non-canonical barrier functions of melanocytes in skin inflammation and repair. In this experiment, we have conducted acetic acid corrosion in four trunk sites in 2 dpf embryos,cut the trunk region at 3 dpf, dissociated the embryos into single cell suspension and performed FACS sorting of dsRed positive fibroblasts. In each biological replicate, around 30 embryos were harvested and 500 fibroblsts were sorted into lysis buffer. Smartseq2 protocol was utilized for double strand cDNA library construction.

炎症后色素沉着（Post-inflammatory hyperpigmentation, PIH）是一种常见的皮肤病症，传统观点认为其源于原位黑素细胞的过度激活。然而，黑素细胞应答的确切触发因素及生理学意义仍未明确。本研究利用乙酸腐蚀诱导的斑马鱼炎症后色素沉着模型，证实黑素细胞向炎症部位迁移是色素沉着过度的关键致病驱动因素。该迁移过程主要由成纤维细胞调控，而非巨噬细胞或中性粒细胞：成纤维细胞在损伤时会分泌趋化因子cxcl12a，通过cxcl12a-cxcr4a信号轴招募黑素细胞。除介导色素沉着过度外，本研究还发现黑素细胞可作为双重保护屏障，在乙酸腐蚀诱导的皮肤损伤中抵御紫外线诱导的DNA损伤与微生物入侵。本研究结果为炎症后色素沉着的发病机制提供了新的见解，并揭示了黑素细胞在皮肤炎症与修复过程中的非经典屏障功能。本实验对受精后2天（2 dpf）的斑马鱼胚胎的四个躯干位点施加乙酸腐蚀处理，于受精后3天（3 dpf）时截取胚胎躯干区域，将胚胎解离为单细胞悬液，并通过荧光激活细胞分选（Fluorescence-activated cell sorting, FACS）分离dsRed阳性成纤维细胞。每个生物学重复约收集30枚胚胎，将500个分选得到的成纤维细胞置于裂解缓冲液中。本研究采用Smart-seq2流程构建双链cDNA文库。