Strategies to optimize kidney recovery and preservation in transplantation: specific aspects in pediatric transplantation

Tannic Acid Improves Renal Function Recovery after Renal Warm Ischemia-Reperfusion in a Rat Model

Background and purpose: Ischemia–reperfusion injury is encountered in numerous processes such as cardiovascular diseases or kidney transplantation; however, the latter involves cold ischemia, different from the warm ischemia found in vascular surgery by arterial clamping. The nature and the intensity of the processes induced by ischemia types are different, hence the therapeutic strategy should be adapted. Herein, we investigated the protective role of tannic acid, a natural polyphenol in a rat model reproducing both renal warm ischemia and kidney allotransplantation. The follow-up was done after 1 week. Experimental approach: To characterize the effect of tannic acid, an in vitro model of endothelial cells subjected to hypoxia–reoxygenation was used. Key results: Tannic acid statistically improved recovery after warm ischemia but not after cold ischemia. In kidneys biopsies, 3 h after warm ischemia–reperfusion, oxidative stress development was limited by tannic acid and the production of reactive oxygen species was inhibited, potentially through Nuclear Factor erythroid-2-Related factor 2 (NRF2) activation. In vitro, tannic acid and its derivatives limited cytotoxicity and the generation of reactive oxygen species. Molecular dynamics simulations showed that tannic acid efficiently interacts with biological membranes, allowing efficient lipid oxidation inhibition. Tannic acid also promoted endothelial cell migration and proliferation during hypoxia. Conclusions: Tannic acid was able to improve renal recovery after renal warm ischemia with an antioxidant effect putatively extended by the production of its derivatives in the body and promoted cell regeneration during hypoxia. This suggests that the mechanisms induced by warm and cold ischemia are different and require specific therapeutic strategies.

Non-immunologic allograft loss in pediatric kidney transplant recipients

Non-immunologic risk factors are a major obstacle to realizing long-term improvements in kidney allograft survival. A standardized approach to assess donor quality has recently been introduced with the new kidney allocation system in the USA. Delayed graft function and surgical complications are important risk factors for both short- and long-term graft loss. Disease recurrence in the allograft remains a major cause of graft loss in those who fail to respond to therapy. Complications of over immunosuppression including opportunistic infections and malignancy continue to limit graft survival. Alternative immunosuppression strategies are under investigation to limit calcineurin inhibitor toxicity. Finally, recent studies have confirmed long-standing observations of the significant negative impact of a high-risk age window in late adolescence and young adulthood on long-term allograft survival.

[Toward a customized preservation for each kidney graft?]

The increased number of patients in waiting list for renal transplantation requires the establishment of recommendations regarding graft preservation techniques. The preservation method impacts graft function and survival particularly in case of extended criteria donors. Based on our experience, the aim of this review is to establish a decisional diagram to draw graft management to 5years in relation to donor type and graft quality. Novel biomarkers are necessary to evaluate graft quality. Nuclear magnetic resonance or transcriptomic analyses are promising. Thus, good quality organs will be preserved in static condition associated to hypothermia; while grafts from extended criteria donors need to be assessed early during dynamic perfusion through an evaluation of perfusion solution to discriminate: good organs, with acceptable risks without perfusion conditions modifications; tolerable risk grafts for which it will be recommended to use a supplementation of perfusion solution with oxygen or pharmacologic additives such as mitochondrion protectors or oxygen carriers; and elevated risks graft which will not be used. This diagram based on experimental data needs to be assessed in clinical trials but highlights the crucial role of kidney graft quality assessment for its management and placed dynamic perfusion preservation as the protocol of choice for extended criteria donors.

[Skin and tissue bank: Operational model for the recovery and preservation of tissues and skin allografts]

Tissue storage is a medical process that is in the regulation and homogenisation phase in the scientific world. The international standards require the need to ensure safety and efficacy of human allografts such as skin and other tissues. The activities of skin and tissues banks currently involve their recovery, processing, storage and distribution, which are positively correlated with technological and scientific advances present in current biomedical sciences. A description is presented of the operational model of Skin and Tissue Bank at INR as successful case for procurement, recovery and preservation of skin and tissues for therapeutic uses, with high safety and biological quality. The essential and standard guidelines are presented as keystones for a tissue recovery program based on scientific evidence, and within an ethical and legal framework, as well as to propose a model for complete overview of the donation of tissues and organ programs in Mexico. Finally, it concludes with essential proposals for improving the efficacy of transplantation of organs and tissue programs.

Short term ex vivo storage of kidneys cause progressive nuclear ploidy changes of renal tubular epitheliocytes

In renal transplantation, there has been considerable success, mainly in term of post-transplant graft function. However, upon closer scrutiny, it is known that severe dysfunction, including persistence of renal failure is seen after transplantation. The major condition that potentially cause significant lesion may be hypothesized to be related to the hypothermic approach to storage. To systematically examine these issues, we stored mammalian (sheep) kidneys in UWS at 4 °C for four different time points (0, 1, 3 and 6 hours). We obtained renal histological sections and examined tubular architecture as well as nuclear characteristics of tubular epitheliocytes. The results of our preliminary investigations suggest that there are temporal changes of tubular epitheliocytes, as well as genomic changes. These changes were also seen in tissues stored at room temperature. Our observations suggest the need for additional studies for redesigning of improvised storage solutions. Pilot studies using Celsior also revealed similar kind of nuclear changes, suggesting that storage conditions are contributory, including perfusion versus static conditions. The results may explain persistence of tubular injury several days after orthotopic transplantation, and may potentially be contributory to delayed graft function (DGF).