Qiyue Jiang,1,2 Fuao Ning,1,2 Qiyue Jia,1,2 Hongwei Wang,1,2 Wenming Xue,1,2 Jiaxin Wang,1,2 Yan Wang,1,2 Zhonghui Zhu,1,2 Lin Tian1,2 

1Department of Occupational and Environmental Health, School of Public Health, Capital Medical University, Beijing, 100069, People’s Republic of China; 2Beijing Key Laboratory of Environment and Aging, Capital Medical University, Beijing, 100069, People’s Republic of China

Correspondence: Lin Tian; Zhonghui Zhu, Department of Occupational and Environmental Health, School of Public Health, Capital Medical University, Beijing, 100069, People’s Republic of China, Email tian_lin@163.com; zhuzhonghui@163.com

Background: In clinical practice, due to the lack of typical symptoms and specific diagnostic biomarkers, silicotic patients often having already developed pulmonary fibrosis by the time of clinical diagnosis. Studies have demonstrated that human umbilical cord mesenchymal stem cell-derived extracellular vesicles (hucMSC-EVs) could moderate silicosis fibrosis, which may be related to the microRNAs (miRNAs) in hucMSC-EVs. While the full extent of their antifibrotic effects and the underlying mechanisms remain to be elucidated.
Methods: HucMSC-EVs were administered from day 28 to day 56 after silica exposure in mice, which in a therapeutic manner. In addition, the antifibrotic abilities of engineered hucMSC-EVs with varying levels of miR-148a-3p, a miRNA with antifibrotic properties, were evaluated. Heat shock protein 90 beta family member 1 (Hsp90b1) is reported to be a target of miR-148a-3p, the protein-protein interaction analysis was used to explore its regulated downstream factors in lung fibrosis. The underlying mechanisms were also investigated by using miR-148a-3p mimics and small interfering RNA (siRNA) targeting Hsp90b1 in vitro.
Results: HucMSC-EVs could reduce the histopathological changes and the levels of fibrotic proteins in the mouse lung tissues when administered in a therapeutic manner. Meanwhile, miR-148a-3p-overexpressed hucMSC-EVs intervention exhibited the enhanced anti-fibrotic effect compared with the negative control intervention group. In vitro, the elevated level of miR-148a-3p in hucMSC-EVs was shown to enhance hucMSC-EVs’ inhibition of fibroblast collagen hypersecretion, whereas a depressed level of miR-148a-3p in hucMSC-EVs partially counteracted the inhibitory effect. Moreover, the mechanistic investigations revealed that miR-148a-3p could blunt β-catenin signaling via targeting Hsp90b1 in fibroblasts.
Conclusion: This study demonstrated that hucMSC-EVs retain their antifibrotic properties in silicotic mice when administered in a therapeutic manner. Further, miR-148a-3p was confirmed to be an essential component within hucMSC-EVs, mediating their inhibition of silica-induced pulmonary fibrosis by reducing β-catenin signaling via targeting of Hsp90b1 in fibroblasts.
Plain Language Summary: Silicosis is a life-threatening occupational pulmonary fibrotic disease caused by silica inhalation, and there is currently a lack of targeted drugs for treating silicosis. Extracellular vesicles (EVs) are emerging as pivotal players in cell-free therapeutics due to their crucial role in intercellular communication and the efficient transport of bioactive molecules. In this study, the antifibrotic effects of human umbilical cord mesenchymal stem cell-derived EVs (hucMSC-EVs) on experimental silicosis were investigated. HucMSC-EVs were administered therapeutically, an approach that aligns more closely with the clinical situation of silicosis. In addition, the antifibrotic abilities of engineered hucMSC-EVs with varying levels of miR-148a-3p, a microRNA (miRNA) with antifibrotic properties, were evaluated. The underlying mechanisms that contribute to these therapeutic effects were also investigated. The results demonstrated that hucMSC-EVs retain their antifibrotic properties in silicotic mice when administered in a therapeutic manner. Further, miR-148a-3p was confirmed to be an essential component within hucMSC-EVs, mediating their inhibition of silica-induced pulmonary fibrosis by reducing β-catenin signaling via targeting of heat shock protein 90 beta family member 1 (Hsp90b1) in fibroblasts. These insights provide strong empirical support for hucMSC-EVs-based therapy as a novel treatment approach for silicosis and other lung fibrotic diseases.

Keywords: MiR-148a-3p, extracellular vesicles, pulmonary fibrosis, β-catenin, Hsp90b1, silica