Bioinformatic analysis of potential biomarkers and mechanisms of immune infiltration in mitral regurgitation complicated by atrial fibrillation

Background: Mitral regurgitation (MR) is one of the most prevalent valvular diseases. Degenerated MR induced volume overload leads to left atrial enlargement and eventually, atrial fibrillation (AF). AF has a negative effect on patient prognosis despite recent advances in minimal invasive transcatheter devices for valve surgery. However, more effective strategies aimed at precisely treating from pathophysiology and genetic perspective are scarce. Methods: The gene expression datasets, GSE109744 and GSE79768, were obtained from the Gene Expression Omnibus database and analyzed to identify the differentially expressed genes (DEGs) in patients with mitral value prolapse (MVP) and AF. Subsequently, we predicted the extensive miRNA targets, and the protein-protein interaction (PPI) and miRNA-target gene regulatory networks were established. Functional enrichment analyses were performed for the DEGs. In addition, the co-expressed DEGs coupled with their predicted miRNAs and disease phenotypes involved in MVP and AF were assessed. Finally, the immune infiltration in both datasets was examined. Results: A total of 491 and 180 DEGs were identified in the mitral valve and left atrial specimens, respectively. From these, 11 integrated co-expressed DEGs were identified, namely, PRG4, GPR34, RELN, CA3, IL1B, EPHA3, CHGB, TCEAL2, B3GALT2, ASB11, and CRISPLD1. The enriched Gene Ontology terms and KEGG pathways associated with the DEGs were determined, and the top 10 hub genes and top 3 gene clusters were selected from the PPI network. A prediction of target miRNAs was performed based on the co-expressed DEGs. The enrichment of the co-expressed DEGs suggested that immune and inflammatory responses might be involved in the disease development through multiple immune related pathways, including the interaction of cytokines and chemokines. Notably, this result was consistent with the immune infiltration analysis since the proportions of naive B cells and memory B cells were significantly different in MVP and AF tissues compared to normal tissues. Conclusions: MR and AF are related, and 11 co-expressed DEGs were found to be significantly associated with MVP with AF, and indeed, these may represent novel biomarkers. Several immune cells were found to contribute to the process of MVP and AF via diverse mechanisms, in particular, antigen presenting cells.