How to Best Protect Kidneys for Transplantation-Mechanistic Target

Metabolic Characterization of Deceased Donor Kidneys Undergoing Hypothermic Machine Perfusion Before Transplantation Using 13C-enriched Glucose

Background

The provision of a metabolic substrate is one mechanism by which hypothermic machine perfusion (HMP) of kidneys provides clinical benefit. This study aimed to describe de novo metabolism in ex vivo human kidneys undergoing HMP before transplantation using 13C-labeled glucose as a metabolic tracer.

Methods

Cadaveric human kidneys were perfused with modified clinical-grade perfusion fluid (kidney perfusion solution [KPS-1], Organ Recovery Systems), in which glucose was uniformly enriched with the stable isotope 13C ([U-13C] glucose). The sampled perfusion fluid was analyzed using a blood gas analyzer, and metabolic profiling was performed using 1-dimensional and 2-dimensional nuclear magnetic resonance spectroscopy and mass spectrometry. Functional outcome measures included serum creatinine levels and the development of delayed graft function.

Results

Fourteen kidneys were perfused with the modified KPS-1 and successfully transplanted. The mean duration of HMP was 8.7 h. There was a sustained increase in the conversion of glucose into de novo glycolytic end products, such as lactate, in donor kidneys during HMP. There was no significant association between functional outcomes and metabolism during the HMP. De novo anaerobic metabolism was indicated by continuing lactate production, as indicated by increasing concentrations of universally 13C-labeled lactate ([U-13C] lactate) in perfusion fluid from all kidneys. This was more evident in donation after circulatory death donor kidneys.

Conclusions

Our study is the first to use [U-13C] glucose to describe the metabolism during HMP. The consequences of an initial warm ischemic insult on circulatory death in donor kidneys continue during the preservation period.

Oxygenation by Intravascular Photosynthesis Reduces Kidney Damage During ex Vivo Preservation

Several clinical issues are associated with reduced oxygen delivery to tissues due to impaired vascular perfusion; moreover, organs procured for transplantation are subjected to severe hypoxia during preservation. Consequently, alternative tissue oxygenation is an active field in biomedical research where several innovative approaches have been recently proposed. Among these, intravascular photosynthesis represents a promising approach as it relies on the intrinsic capacity of certain microorganisms to produce oxygen upon illumination. In this context, this work aims at the development of photosynthetic perfusable solutions that could be applied to preserve organs for transplantation purposes. Our findings demonstrate that a biocompatible physiological solution containing the photosynthetic microalgae Chlamydomonas reinhardtii can fulfill the metabolic oxygen demand of rat kidney slices in vitro. Furthermore, intravascular administration of this solution does not induce tissue damage in the rat kidneys. Moreover, kidney slices obtained from these algae-perfused organs exhibited significantly improved preservation after 24 h of incubation in hypoxia while exposed to light, resulting in reduced tissue damage and enhanced metabolic status. Overall, the results presented here contribute to the development of alternative strategies for tissue oxygenation, supporting the use of perfusable photosynthetic solutions for organ preservation in transplantation.

Global trends of delayed graft function in kidney transplantation from 2013 to 2023: a bibliometric analysis

Delayed graft function (DGF) is an early complication after kidney transplantation. The literature on DGF has experienced substantial growth. However, there is a lack of bibliometric analysis of DGF. This study aimed to analyze the scientific outputs of DGF and explore its hotspots from 2013 to 2023 by using CiteSpace and VOSviewer. The 2058 pieces of literature collected in the Web of Science Core Collection (WOSCC) from 1 January 2013 to 31 December 2023 were visually analyzed in terms of the annual number of publications, authors, countries, journals, literature co-citations, and keyword clustering by using CiteSpace and VOSviewer. We found that the number of papers published in the past ten years showed a trend of first increasing and then decreasing; 2021 was the year with the most posts. The largest number of papers was published by the University of California System, and the largest number of papers was published by the United States. The top five keyword frequency rankings are: 'delayed graft function', 'kidney transplantation', 'renal transplantation', 'survival', and 'recipients'. These emerging trends include 'brain death donors', 'blood absence re-injection injuries', 'tacrolimus', 'older donors and recipients', and 'artificial intelligence and DGF'. In summary, this study reveals the authors and institutions that could be cooperated with and discusses the research hotspots in the past ten years. It provides a reference and direction for future research and application of DGF.

Kidney/Aorta Ratio for Renal Morphometric Determination in Swine Subjected to Acute Kidney Injury Using an Optimized Surgical Model

This research aims to establish an experimental surgical model for access to the renal pedicle and kidney and to determine renal length measurement via the kidney/aorta ratio (K/AO) using ultrasound. Fifteen swine underwent ventral median celiotomy with a supraumbilical transverse incision to access the right and left renal pedicles and induce renal ischemia-reperfusion injury (IRR). The kidneys were evaluated using ultrasonography to standardize renal length, aortic diameter, and the K/AO. Assessment was performed at 2 time points: 1 h before and 24 h after the surgery to induce IRR. Blood and urine samples were collected to assess renal function. Histologic evaluation of kidney fragments was also conducted. The proposed abdominal cavity access method proved to be highly efficient for exposing the right and left renal pedicles and inducing IRR. Serum levels of urea, creatinine, calcium, and phosphorus, as well as levels of the urinary protein/urinary creatinine ratio and urinary GGT, did not show significant differences. Acute kidney injury was confirmed through histopathology. The mean lengths of the right and left kidneys were 82.63 and 87.64 mm, respectively. The values of the right and left K/AO were 9.81 and 10.38, respectively. There was no statistically significant difference in the K/AO ratio before and after IRR. The proposed surgical model allowed surgical intervention on the renal pedicles without intra- or postoperative complications. Furthermore, the K/AO could be measured through ultrasonography, establishing a reference for healthy animals.

Serum Glucocorticoid-Regulated Kinase-1 in Ischemia-Reperfusion Injury: Blessing or Curse

The family of serum-glucocorticoid-regulated kinase (SGK) consists of three paralogs, SGK-1, SGK-2, and SGK-3, with SGK-1 being the better studied. Indeed, recognition of the role of SGK-1 in regulation of cell survival and proliferation has led to introduction of a number of small-molecule inhibitors for some types of cancer. In addition, SGK-1 regulates major physiologic effects, such as renal solute transport, and contributes to the pathogenesis of non-neoplastic conditions involving major organs including the heart and the kidney. These observations raise the prospect for therapeutic modulation of SGK-1 to reduce the burden of such diseases as myocardial infarction and acute kidney injury. Following a brief description of the structure and function of SGK family of proteins, the present review is primarily focused on our current understanding of the role of SGK-1 in pathologies related to ischemia-reperfusion injury involving several organs (e.g., heart, kidney). The essential role of the mitochondrial permeability transition pore in cell death coupled with the pro-survival function of SGK-1 raise the prospect that its therapeutic modulation could beneficially impact conditions associated with ischemia-reperfusion injury. SIGNIFICANCE STATEMENT: Since the discovery of serum glucocorticoid-regulated kinase (SGK)-1, extensive research has unraveled its role in cancer biology and, thus, its therapeutic targeting. Increasingly, it is also becoming clear that SGK-1 is a major determinant of the outcome of ischemia-reperfusion injury to various organs. Thus, evaluation of existing information should help identify gaps in our current knowledge and also determine whether and how its therapeutic modulation could impact the outcome of ischemia-reperfusion injury.