Ex Situ Liver Splitting During Hypothermic Oxygenated Perfusion: Mechanistic Insights into Mitochondrial Injury and FMN-Based Viability Assessment

Background/Objectives: Hypothermic oxygenated perfusion (HOPE) improves graft preservation in whole liver transplantation, yet evidence supporting its use in split grafts for pediatric transplantation remains limited. Mitochondrial injury assessed during HOPE through spectroscopic measurement of flavin mononucleotide (FMN) has been associated with graft function in whole-organ transplantation. Here, we evaluate a human liver assessment pathway integrating mitochondrial viability testing with ex situ liver splitting during HOPE. Methods: Following standard procurement and transport, twelve discarded extended criteria human donor livers were evaluated for split feasibility and underwent HOPE (VitaSmart®). Donors were between 40 and 72 years with a BMI of 23.4–42.7 kg/m2 and 4–22 h of cold storage prior to HOPE. After two hours of portal-venous HOPE treatment, different split procedures were performed. Perfusates and tissues were analyzed for mitochondrial injury and inflammatory responses. Results: Four grafts met previously reported FMN thresholds for transplant suitability in whole-graft HOPE studies (FMN ≤ 0.02 μg/mL at 60 min). Livers with low FMN release demonstrated lower Complex I and II injury, greater ATP recovery, and reduced inflammatory signaling during HOPE. Conclusions: These findings indicate that mitochondrial injury during HOPE can be monitored during ex situ splitting and suggest that FMN-guided metabolic assessment may support graft evaluation within split liver transplantation pathways for pediatric recipients.