Urinary Mitochondrial DNA as biomarker in Living Donor Kidney Transplantation

aIschemia–reperfusion injury (IRI) is a key contributor to graft dysfunction in kidney transplantation. Cell-free mitochondrial DNA (mtDNA) is increasingly recognized as a damage-associated molecular pattern (DAMP) and biomarker in IRI, but its prognostic role in living donor kidney transplantation (LDKT) remains unclear. Methods: This post hoc analysis of the VAPOR-1 study evaluated urinary mtDNA (UmtDNA) in 57 LDKT recipients. MtDNA levels (ND1, ND6, and D-loop) were measured at five early timepoints post-transplantation using qPCR. Associations between early UmtDNA and long-term graft function, defined by estimated glomerular filtration rate (eGFR) at 1, 12, and 24 months, were analyzed. Results: Higher UmtDNA levels in the first urine after reperfusion were significantly associated with improved eGFR at 12 months and a positive change in eGFR between month 1 and 24. These associations were not attributable to urine creatinine levels or mitochondrial copy number. Conclusions: In this LDKT cohort, elevated early UmtDNA may reflect a well-functioning graft capable of clearing systemic mtDNA rather than ongoing tubular injury. These findings suggest that the biological interpretation of mtDNA as a biomarker is context-dependent and call for careful reconsideration of its role in early transplant monitoring.

缺血再灌注损伤（Ischemia–reperfusion injury, IRI）是肾移植术后移植物功能障碍的核心诱因。无细胞线粒体DNA（cell-free mitochondrial DNA, mtDNA）作为损伤相关分子模式（damage-associated molecular pattern, DAMP）与生物标志物，在IRI中的作用日益得到学界认可，但其在活体供肾移植（living donor kidney transplantation, LDKT）中的预后价值仍不明确。方法：本研究针对VAPOR-1研究开展事后分析，纳入57名活体供肾移植受者，对其尿线粒体DNA（urinary mtDNA, UmtDNA）进行检测。于移植术后早期5个时间节点，采用实时定量聚合酶链式反应（qPCR）检测mtDNA水平（靶序列涵盖ND1、ND6及D-loop区域）。分析早期UmtDNA水平与移植物长期功能的关联，后者以术后1、12及24个月的估算肾小球滤过率（estimated glomerular filtration rate, eGFR）进行定义。结果：再灌注后首次尿液标本中的高UmtDNA水平，与术后12个月的更佳eGFR以及术后1个月至24个月间eGFR的正向变化呈显著相关。上述关联不受尿肌酐水平或线粒体拷贝数的影响。结论：在本LDKT队列中，早期升高的UmtDNA或可反映移植物功能良好、能够清除全身性mtDNA，而非提示持续存在的肾小管损伤。本研究结果表明，mtDNA作为生物标志物的生物学解读需结合具体情境，同时呼吁学界审慎重新考量其在移植术后早期监测中的作用。