Melatonin Regulates the Proliferation of Liaoning Cashmere Goat Skin Fibroblasts via the lncRNA16913.1-chi-miR-195-5p-FZD6 Axis

Liaoning cashmere goat is a unique Chinese cashmere breed, and skin fibroblast proliferation determines hair follicle development and cashmere quality. Melatonin regulates cutaneous cell activity, and lncRNAs function as ceRNA to sponge miRNAs and modulate target genes. Whether melatonin controls fibroblast proliferation through an lncRNA-miRNA-mRNA cascade remains unclear. This study explored how melatonin mediates the LncRNA16913.1-chi-miR-195-5p-FZD6 axis to regulate cashmere goat skin fibroblast proliferation. We constructed gain-of-function and loss-of-function models of LncRNA16913.1 and chi-miR-195-5p. Immunohistochemistry located FZD6 in hair follicles; RT-qPCR, Western blot, CCK-8, EdU and flow cytometry detected gene expression and cell phenotypes. Bioinformatic prediction, dual-luciferase assay, fluorescence in situ hybridization, RNA pull-down and rescue tests verified molecular binding relationships. Melatonin upregulated LncRNA16913.1 and FZD6, yet downregulated chi-miR-195-5p, with FZD6 mainly distributed in hair follicle inner and outer root sheaths. Inhibiting chi-miR-195-5p boosted fibroblast proliferation, restrained apoptosis and accelerated the cell cycle. chi-miR-195-5p directly suppressed FZD6, while cytoplasmic LncRNA16913.1 sequestered this miRNA to recover FZD6 expression. Silencing LncRNA16913.1 eliminated melatonin-mediated FZD6 upregulation. In short, melatonin increased LncRNA16913.1, which sequestered chi-miR-195-5p to release FZD6 and facilitate fibro-blast proliferation. Combined dual-luciferase, bidirectional rescue and cellular phenotypic assays collectively verified the fact that FZD6 acts as the functional downstream target of chi-miR-195-5p to mediate fibroblast proliferation in vitro.