Secreted phosphoprotein 1 promotes the activation of keloid fibroblasts via the CD44/TGF-β1/Smad pathway

Abstract

Keloids, characterized by pruritic and painful lesions, severely impact quality of life. Although Secreted Phosphoprotein 1 (SPP1) has been linked to fibrotic disorders, its role in keloid pathogenesis remains unclear. Bioinformatics analysis and Gene Expression Omnibus (GEO) datasets were utilized to identify key genes in keloid development. mRNA and protein expression levels were assessed using qRT-PCR and Western blot. Cellular proliferation was evaluated via CCK-8 and EdU assays, while cell motility was analyzed through scratch wound healing and migration/invasion assays. Mitochondrial network morphology was examined using MitoTracker staining. In vivo experiments were conducted using a mouse subcutaneous tumor model to validate the functional role of SPP1.SPP1 was identified as a critical gene in keloid fibrosis through bioinformatics and GEO dataset analysis. Human keloid fibroblasts (HKF) exhibited significantly higher SPP1 mRNA and protein expression compared to human skin fibroblasts (HSF). SPP1 inhibition reduced CD44 expression and suppressed HKF migration, invasion, proliferation, epithelial-mesenchymal transition (EMT), and the expression of TGF-β1, p-Smad2/3, Col1A1, and myofibroblast markers. Conversely, transfection of recombinant human SPP1 protein (rhSPP1) enhanced these cellular behaviors. CD44 inhibition attenuated the effects of rhSPP1 and downregulated TGF-β1 and p-Smad2/3 expression. In vivo, downregulation of SPP1 significantly reduced the volume and weight of subcutaneous tumors.SPP1 promotes HKF activity and fibrosis-related behaviors via the CD44/TGF-β1/Smad signaling axis and may inhibit apoptosis through the mitochondrial pathway. These findings highlight SPP1 as a potential therapeutic target for keloid treatment.