Expression of circulating micro-RNAs in patients before and after AAA repair
Authors:   , Tan Xinji 
Published: April 2024

Abdominal aortic aneurysm (AAA) is the most common type of aortic aneurysm, which is defined as a dilation of the abdominal aorta over 3.0 cm or more. Surgical repair is the golden standard for the treatment of AAA, in which open surgical repair (OSR) and endovascular aneurysm repair (EVAR) are the main approaches. Technically speaking, the lesion segment of aueurysm is completely replaced by a graft during OSR, while in EVAR, the lesion is insulated by a stentgraft. EVAR is a less invasive treatment than OSR and shows a lower early mortality rate, although the long-term advantages of EVAR over OSR remain inconclusive. Endoleak, especially the type II endoleak (T2EL), is a common complication after EVAR. According to research, 16-28% of the patients develop a T2EL after EVAR, and it accounts for nearly three in four of all types of endoleaks. Around 30-50% of the T2EL resolved spontaneously during the follow-up, however, it still causes a secondary intervention in many patients. Therefore, it is critical to monitor endoleaks after repair. Patent aortic branches in the stent-overlapped area and vasa vasorum have been identified as potential sources of blood flow in T2EL. However, the mechanisms of biological changes or remodeling of the aneurysm sac after the repair are still not clear, but they have been considered to play an important role in the development of endoleaks. Unfortunately, it is impossible to obtain a tissue sample of the aortic wall in patients who underwent EVAR. MicroRNAs (miRNAs) are a class of small single-stranded non-coding RNAs that inhibit the expression of target message RNA (mRNA). miR-29b/29c, miR-155, and miR-15a are miRNAs associated with regulating extracellular matrix (ECM) components, inflammation, and proliferation, respectively. All four miRNAs have been identified as biomarkers of AAA, not only in aneurysm tissue but also extracellular as circulating miRNAs. However, it is still unknown whether they can reflect the biological changes after AAA repair. Thus, we conducted a prospective study to investigate the changes in expression of circulating miR-29b, miR-29c, miR-155, and miR-15a before (T0), 3 days (T1), and 3 months (T2) after AAA repair. A total of 39 patients were recruited for this study, 17 of whom were repaired by OSR and 22 of whom were repaired by EVAR. Four patients failed the T2 follow-up due to the Covid-19 pandemic. No significant changes were found in the expression of miR-29b, miR-29c, miR-155, and miR-15a. There were also no obvious differences between OSR and EVAR. However, the T1 expression of miR-15a was significantly lower in patients without endoleak after EVAR than in those who developed endoleak after EVAR and those who were repaired by OSR. Unfortunately, these differences did not persist to the T2 follow-up, and no other differences were found among these patients. In summary, miR-15a is a miRNA that significantly changes in AAA patients. This study demonstrates that the expression of circulating miR-15a is lower in patients without endoleak three days after EVAR, compared to those who had endoleak after EVAR and those who underwent OSR. The results suggest that miR-15a might be involved in the early aortic remodeling after EVAR as an indicator of endoleak.