Systemic sclerosis (SSc) is a life-threatening autoimmune connective tissue disease characterized by progressive and often irreversible fibrosis affecting the skin and multiple internal organs. While transforming growth factor-beta (TGF-β) signaling has been established as the master regulator of fibrogenesis in SSc, the upstream molecular mechanisms that perpetuate and amplify this pathway remain incompletely understood. Current therapeutic options for SSc-associated fibrosis are limited, with most interventions showing only modest efficacy. This study investigated stathmin-2 (STMN2), a microtubule-regulating protein not previously implicated in fibrotic diseases, as a potential critical driver of SSc skin fibrosis.

Differentially expressed genes (DEGs) and weighted gene co-expression network analysis (WGCNA) were integrated across two SSc skin transcriptomic datasets (GSE58095 and GSE181549) to identify fibrosis-associated hub genes. STMN2 expression was validated in an independent cohort (GSE95065), clinical SSc skin biopsies, and single-cell RNA-sequencing data (GSE138669). Functional studies using lentiviral overexpression and knockdown in BJ human dermal fibroblasts evaluated the effects of STMN2 on proliferation, migration, and expression of fibrotic markers (COL-I, COL-III, fibronectin). Mechanistic involvement of TGF-β/Smad signaling was assessed by quantification of Smad2/3 and phosphorylated Smad2/3, with pharmacological inhibition using SB431542. A bleomycin-induced mouse model with AAV-mediated Stmn2 knockdown was used for in vivo validation.

STMN2 was significantly upregulated in SSc skin and positively correlated with mRSS and profibrotic gene expression. Single-cell analysis localized STMN2 predominantly to fibroblasts. STMN2 overexpression enhanced fibroblast proliferation, migration, and ECM production, whereas knockdown attenuated these responses. Mechanistically, STMN2 increased Smad2/3 phosphorylation, and SB431542 abolished STMN2-driven profibrotic effects. In vivo, AAV-mediated Stmn2 silencing significantly attenuated bleomycin-induced dermal thickening, collagen deposition, and fibrotic marker expression.

STMN2 functions as a critical fibroblast-intrinsic amplifier of TGF-β/Smad signaling, promoting profibrotic phenotypes and ECM accumulation. The strong correlation with disease severity and potent antifibrotic effects upon knockdown position STMN2 as a promising therapeutic target for SSc-associated fibrosis.