Microbial signatures in chronic thromboembolic pulmonary hypertension thrombi: Insights from metagenomic profiling of fresh and organized thrombi

Objective: Many studies have reported microbial signatures in thrombi at major vascular sites, such as the coronary artery and the middle cerebral artery, which are critical for maintaining proper blood flow and oxygenation. Chronic thromboembolic pulmonary hypertension (CTEPH) is a condition involving non-resolving thrombosis that has not been fully studied. This study explored the microbial taxonomy and functional profiles of both fresh and organized thrombi associated with CTEPH to investigate the role of microbiota in thrombus nonresolving. Methods: In this study, 12 CTEPH fresh thrombi and 12 organized thrombi were collected from 14 patients with CTEPH. Metagenomic sequencing was employed to explore the genomic information of all microorganisms in the thrombus samples. Results: Our data demonstrated a diverse range of microorganisms in CTEPH thrombi, whether fresh or organized. Notably, a considerable proportion (54.7 %) of sequencing data could not be classified into the relative microbial taxa, highlighting the complexity and novelty of the thrombus ecosystem. Although there were no significant differences in microbial community structure between the two groups, the abundance of dominant microbial species varied. Leuconostoc sp. DORA 2, Staphylococcus aureus, and Aliidongia dinghuensis were common dominant species in CTEPH thrombus. Organized thrombus significantly increased the relative abundance of Staphylococcus aureus, which was confirmed to effectively distinguish between organized and fresh thrombi by LeFSe analysis and random forest analysis. Functional annotation using both the KEGG and eggNOG databases revealed that organized thrombi exhibit stronger metabolic functions, particularly in amino acid metabolism. Conclusions: Our findings suggest that microbial composition and function may play an important role in thrombus organization. Targeting inflammation to prevent thrombosis presents promising opportunities for further research in this area.