STAT5/VCAN/PI3K signaling pathway promotes fibroblast activation and lung fibrosis

Rationale

Pulmonary fibrosis (PF) is a progressive and debilitating disease characterized by the excessive deposition of extracellular matrix (ECM) components. The activation of fibroblasts and the production of large amounts of ECM are important factors in the development of PF. This study aimed to elucidate the role and mechanism of versican (VCAN) in promoting PF and to identify therapeutic targets for PF.

Methods

A mouse lung fibrosis model was constructed by tracheal instillation of bleomycin or ray-induced fibrosis in mice, and the expression level of VCAN was evaluated. The cellular localization of VCAN was determined using tissue immunofluorescence and the extraction of primary mouse cells. Using mice with specific VCAN knockout in fibroblasts, we analyzed the effects of VCAN on the degree of lung fibrosis and fibroblast activation via immunohistochemistry and immunofluorescence. Primary mouse fibroblasts were extracted, and human/mouse-derived fibroblast cell lines were used to assess the effect of the VCAN/PI3K pathway on fibroblast activation and its specific mechanism through immunofluorescence, Transwell, scratch, and western blotting assays. STAT5/VCAN signaling was investigated using protein blotting, chromatin immunoprecipitation, luciferase reporter gene analysis, and real-time quantitative polymerase chain reaction. Further, the pathogenesis of PF was evaluated in vivo in mice treated with a VCAN-specific knockdown virus or PI3K inhibitors.

Results

VCAN expression was significantly elevated in the fibroblasts of mice with PF. After the specific knockout of VCAN in fibroblasts, the activation level of lung fibroblasts and the level of lung fibrosis were significantly decreased in PF mice. Mechanistically, STAT5 acted as a transcription factor that promoted VCAN expression upon bleomycin induction. High VCAN expression promoted fibroblast activation through the PI3K pathway, and suppressing VCAN using an specific knockdown adeno-associated virus or the PI3K inhibitors significantly alleviated lung fibrosis in PF mice.

Conclusion

STAT5 is a transcription factor that enhances VCAN expression; VCAN promotes fibroblast activation through the PI3K signaling pathway in response to the transcription factor STAT5, thereby promoting lung fibrosis. The STAT5/VCAN/PI3K signaling pathway may serve as a potential target for lung fibrosis treatment.