TGF-β1 promotes collagen synthesis in systemic sclerosis via upregulating P4HA3.

OBJECTIVE: Systemic sclerosis (SSc) is a complex autoimmune disease resulting in fibrosis of skin and internal organs. Despite progress in treatment, SSc carries high mortality due to organ fibrosis. This study aimed to identify a potential antifibrotic therapeutic for the treatment of SSc. METHODS: SSc bioinformatics data (GSE181549 and GSE138669) were obtained from the public Gene Expression Omnibus (GEO) database. Subsequently, we conducted differential analysis, Protein-protein interaction (PPI) network construction, gene enrichment analysis to identify a key fibrotic gene, followed by verification. RESULTS: A total of 107 differentially expressed genes were identified through analysis between SSc patients and healthy controls. P4HA3 (α subunit of Collagen prolyl 4-hydroxylases, C-P4Hs) was identified by PPI network analysis. P4HA3 was the sole upregulated gene and positively correlated with the modified Rodnan skin score. PI3K/AKT signaling pathway was enriched by GSEA for single-gene to obtain P4HA3-related pathways. Single-cell analysis detected predominant TGF-β1 upregulation in immune cells, particularly in CD14 (+) CD16 (-) monocytes, and P4HA3 showed elevated expression in SFRP2 (high) fibroblasts. Immunohistochemistry indicated that P4HA3- and TGF-β1-positive cell numbers were elevated in the dermal layers of SSc patients. P4HA3 was also elevated in bleomycin-treated mice and TGF-β1-induced human fibroblasts. Inhibition of C-P4Hs ameliorated experimental fibrosis in bleomycin-treated mice and TGF-β1-induced human fibroblasts. Hydroxyproline levels were reduced following P4HA3 knockdown in human fibroblasts. CONCLUSION: Our results suggest that P4HA3 is upregulated by TGF-β1 secreted from immune cells to promote collagen synthesis in SSc. Inhibition of C-P4Hs is a potential therapeutic approach for SSc fibrosis.