Expanding the Horizons of Pre-Transplant Renal Vascular Assessment Using Ex Vivo Perfusion

Recently, immense efforts have focused on improving the preservation of (sub)optimal donor organs by means of ex vivo perfusion, which enables the opportunity for organ reconditioning and viability assessment. However, there is still no biomarker that correlates with renal viability. Therefore, it is essential to explore new techniques for pre-transplant assessment of organ quality to guarantee successful long-term transplantation outcomes. The renal vascular compartment has received little attention in machine perfusion studies. In vivo, proper renal vascular and endothelial function is essential for maintaining homeostasis and long-term graft survival. In an ex vivo setting, little is known about vascular viability and its implications for an organ's suitability for transplant. Seeing that endothelial damage is the first step in a cascade of disruptions and maintaining homeostasis is crucial for positive post-transplant outcomes, further research is key to clarifying the (patho)physiology of the renal vasculature during machine perfusion. In this review, we aim to summarize key aspects of renal vascular physiology, describe the role of the renal vasculature in pathophysiological settings, and explain how ex vivo perfusion plays a role in either unveiling or targeting such processes. Additionally, we discuss potentially new vascular assessment tools during ex vivo renal perfusion.

Novel oxygenation technique for hypothermic machine perfusion of liver grafts: Validation in porcine Donation after Cardiac Death (DCD) liver model

BACKGROUND

Hypothermic oxygenated machine perfusion improves outcomes in Liver Transplantation, but application is limited as O₂ is supplied by a stationary circuit. A novel technique of O₂ "pre-charge" in a portable pump would broaden use and further mitigate ischemia damage from organ transport.

METHODS

Porcine DCD livers were randomized to static cold storage (SCS, n = 8) or hypothermic machine perfusion (HMP). HMP was stratified into HMP-O₂ (n = 5), non-O₂ open to air HMP-RA (n = 5), and non-O₂ with sealed lids or no air HMP-NA (n = 5). HMP-O₂ was "pre-charged" using 100% O₂ delivered at 10 L/min over 15 min. Perfusate and tissue O₂ tension (pO₂), liver biopsies, and fluid chemistries were analyzed.

RESULTS

"Pre-charge" achieves sustained tissue and perfusate pO₂ vs others. HMP-O₂ results in decreased markers of hepatocyte injury: ALT (p < 0.05) and LDH (p < 0.05), lower expression of CRP and higher expression of SOD1 vs SCS. This suggests decreased inflammation and improved ROS scavenging.

CONCLUSIONS

"Pre-charge" is an effective technique, which allows portability and transport without an O₂ source and improves graft parameters.

Exploring the role of short-course cyclosporin a therapy in preventing homograft valve calcification after transplantation

This study was designed to explore the role of short-course cyclosporin A therapy in preventing calcification. Homograft valves heterotopically allografted onto abdominal aorta from SD to Wistar rats. The expression of CD25, CD40L, CD71, calcium content and morphological change were observed. In control group, expression of immune indices got maximal at early stage postoperatively, and then gradually declined, remained at low level 12 weeks afterwards. In test group with Cyclosporin A, the expression of immune indices were lower than that of control group at 2-4 weeks postoperatively, but no significant difference was found 8 weeks afterwards. The calcification began from 4 weeks postoperatively, increased gradually and reached highest level at 12 weeks. In test group calcium content was much lower from 4 to 16 weeks postoperatively. It is concluded that cyclosporine A treatment can prevent calcification of homograft valves because it inhibited immune response at early stage after transplantation.