Deciphering the role of extrachromosomal circular DNA in adipose stem cells from old and young donors

Background: The functional impairment of adipose stem cells (ASCs) during aging limits their clinical transformation. Studies have shown that extrachromosomal circular DNAs (eccDNAs) are associated with tumor progression and cell aging, but the roles of eccDNAs in ASCs remain unknown.Method: We conducted Circle sequencing (Circle-seq) to identify eccDNAs in ASCs isolated from young and old donors. The differentially expressed eccDNAs were calculated, annotated and validated via polymerase chain reaction.Results: Thousands of eccDNAs were identified and comprehensively characterized. Most of them were GC-rich, < 1000 base pairs in size, and were enriched on chromosome 19 and 17 with a high density of Alu elements and genes, 2 kb upstream/downstream of genes and satellites. In total, 3025 eccDNAs were differentially expressed among the two ASC groups. Conjoint analysis of the Circle-seq results and previous RNA-seq results revealed that 73 eccDNAs and 55 genes exhibited the same differential expression between the two groups. KEGG and GO analyses revealed that genes encoding differentially expressed eccDNAs were enriched for cell adhesion, cellular senescence and TGF-beta receptor signaling pathway. We also found that aged ASCs exhibited loss of eccDNAs, including CAMK2G ((chr10: 75577899-75578176)), TRABD2B ((chr1: 48305638-48307008)) and TRABD2B ((chr1: 48305425)(-48307091)).Conclusion: In this study, we elucidated the first eccDNA profile relating to ASCs and demonstrated that three eccDNAs are lost in aged ASCs, which may be potential biomarkers of stem cell aging and valuable targets for stem cell rejuvenation.