Intravenous injection of BMSCs modulate tsRNA expression and ameliorate lung remodeling in COPD mice.

Background: Chronic obstructive pulmonary disease (COPD) is characterized by lung remodeling induced by chronic inflammation, presenting challenges for effective treatment. Mesenchymal stem cells (MSCs) and their extracellular vesicles (EVs) have shown promise in mitigating inflammation and tissue repairing in various diseases, including COPD. However, the optimal therapeutic pathways for different stages of COPD remain unclear. Transfer RNA-derived small RNAs (tsRNAs) are emerging as key regulators of cellular processes. However, their role in COPD and MSC therapy remains poorly understood.

Methods: This study explored the optimal administration routes and efficacy of bone marrow mesenchymal stem cells (BMSCs) and their extracellular vesicles (BMSC-EVs) in treating inflammatory or emphysematous COPD stages in mouse models. Male C57BL/6 mice were exposed to cigarette smoke daily for 6 or 16 weeks, with intraperitoneal CSE injections every 10 days, to model different stages of COPD. Mice were then treated with tracheal or intravenous injections of BMSCs or BMSC-EVs. PKH26 fluorescent dye labeled BMSCs and BMSC-EVs for pulmonary distribution observation. Lung tissue inflammation, apoptosis, EMT, and collagen deposition were assessed using HE staining, TUNEL assay, immunohistochemistry, and Sirius Red staining. Gene and tsRNA expression in lung tissues were analyzed by high-throughput sequencing. Differentially expressed tsRNAs (DE-tsRNAs) were validated by RT-qPCR. Statistical analysis was performed using GraphPad Prism 9.0. Data are presented as mean ± standard deviation (SD).

Results: In 16-week COPD mice characterized by emphysema, tracheal administration of BMSC-EVs showed more significant lung distribution and inhibition of emphysematous pathology. In 6-week COPD mice characterized by inflammation, intravenous injection of BMSCs led to significant pulmonary homing, significantly reduced lung inflammation, apoptosis, EMT, and collagen deposition (P < 0.05). High-throughput sequencing indicated BMSC treatment downregulated genes related to these processes while upregulating mitochondrial function genes. Co-expression networks of DE-tsRNAs and target genes suggested potential roles in COPD. RT-qPCR confirmed significant differential expression of two DE-tsRNAs during COPD progression and BMSC treatment (P < 0.05).

Conclusions: Our study provides insights into selecting MSC and MSC-EV administration routes for different COPD stages. High-throughput sequencing supports BMSCs' inhibitory effects on lung remodeling and identifies the first tsRNA expression profile in a COPD model, warranting further investigation.