Milk exosomes loaded with atorvastatin suppress fibroblast activation and extracellular matrix remodeling via the TGF-β/SMAD pathway in ligamentum flavum hypertrophy.

INTRODUCTION

Ligamentum flavum hypertrophy (LFH) is the main pathophysiological mechanism of spinal stenosis. Milk exosomes (mExo), has emerged as a promising candidate for drug delivery. In this study, we propose the construction of an effective atorvastatin (Ato) delivery system and investigate its therapeutic potential role in LFH.

METHODS

In this study, we initially employed bioinformatics analysis and human ligamentum flavum (LF) tissue to investigate the molecular biological changes that occur in LFH. Subsequently, mExo was extracted and milk exosomes loaded with atorvastatin (Ato@mExo) was prepared. Finally, the effects of Ato, mExo, and Ato@mExo on the pathogenesis of LFH were investigated by in vivo and in vitro experiments.

RESULTS

Consequently, we observed that levels of Fibronectin, Collagen III, Collagen I, TGF-β1, and α-SMA levels were significantly increased in LFH samples and observed a dysregulation of the ratio of collagen fibers to elastic fibers. The results of transmission electron microscope (TEM) and nanoparticle tracking analysis (NTA) demonstrated the effective preparation of mExo and Ato@mExo. Subsequent results demonstrated that Ato, mExo, and Ato@mExo effectively suppressed the expression of TGF-β1-induced fibrosis-associated proteins, including Fibronectin, Collagen III, Collagen I, and α-SMA, in human LF cells. Mechanistic studies have revealed that Ato, mExo, and Ato@mExo all inhibit fibrosis in LF cells by blocking the TGF-β1-SMAD2/3 signaling pathway. Furthermore, Ato, mExo, and Ato@mExo ameliorate mechanical stress-induced LFH in vivo. A notable finding was the superior inhibitory effect of Ato@mExo on LFH, as evidenced by both in vivo and in vitro experiments.

CONCLUSIONS

The findings of this study indicate that Ato, mExo, and Ato@mExo alleviate LFH by inhibiting the TGF-β1-SMAD2/3 signaling pathway. It is noteworthy that Ato@mExo exhibits a more significant inhibitory effect. Accordingly, these findings imply that Ato@mExo has the potential to serve as a promising candidate for early prevention and treatment of LFH.