Reduction of ischemia/reperfusion injury in organ transplants by cytoprotective strategies:

Evolving Trends in Kidney Transplant Outcomes Among Older Adults: A Comparative Analysis Before and During the COVID-19 Pandemic

Background

Advancements in medical technology, healthcare delivery, and organ allocation resulted in improved patient/graft survival for older (age ≥65) kidney transplant (KT) recipients. However, the recent trends in these post-KT outcomes are uncertain in light of the mounting burden of cardiovascular disease, changing kidney allocation policies, heterogeneity in candidates' risk profile, and the coronavirus disease 2019 pandemic. Thus, we examined secular trends in post-KT outcomes among older and younger KT recipients over the last 3 decades.

Methods

We identified 73 078 older and 378 800 younger adult (aged 18-64) recipients using Scientific Registry of Transplant Recipients (1990-2022). KTs were grouped into 6 prepandemic eras and 1 postpandemic-onset era. Kaplan-Meier and Cox proportional hazards models were used to examine temporal trends in post-KT mortality and death-censored graft failure.

Results

From 1990 to 2022, a 19-fold increase in the proportion of older KT recipients was observed compared to a 2-fold increase in younger adults despite a slight decline in the absolute number of older recipients in 2020. The mortality risk for older recipients between 2015 and March 14, 2020, was 39% (adjusted hazard ratio [aHR] = 0.61, 95% confidence interval [CI], 0.50-0.75) lower compared to 1990-1994, whereas that for younger adults was 47% lower (aHR = 0.53, 95% CI, 0.48-0.59). However, mortality risk during the pandemic was 25% lower (aHR = 0.75, 95% CI, 0.61-0.93) in older adults and 37% lower in younger adults (aHR = 0.63, 95% CI, 0.56-0.70) relative to 1990-1994. For both populations, the risk of graft failure declined over time and was unaffected during the pandemic relative to the preceding period.

Conclusions

The steady improvements in 5-y mortality and graft survival were disrupted during the pandemic, particularly among older adults. Specifically, mortality among older adults reflected rates seen 20 y prior.

Ischemia reperfusion injury in kidney transplantation: A case report

RATIONALE

Kidney transplantation is considered the best treatment for patients with end stage renal disease. Ischemia- reperfusion injury (IRI) is an evitable event after deceased donor transplantation and influences short term and long term graft outcome. Few data on IRI's histology in the setting of kidney transplantation are available in the literature despite its frequency and its severity.

PATIENT CONCERNS

A 64-year-old patient was admitted for his 1st kidney transplantation. There were no pre-existing immunization. The surgery proceeded without complications; with cold ischemia estimated at 37 h 50 min and warm ischemia at 44 min. The immunosuppression protocol was as follows: induction by thymoglobulins, mycophelonate mofetil, corticosteroids. Few hours after transplantation, the patient remained anuric and the biological assessment highlighted in addition to renal failure, hyperlactatemia at 5 mmol/L and a high increase in lactate deshydrogenase (LDH) at 5239 U/L. An abdominopelvic angio-scanner was performed urgently to eliminate the hypothesis of thrombosis of the artery or vein of the graft. A kidney biopsy was performed the day after the transplant and revealed massive lesions of acute tubular necrosis including apoptosis, autophagy-associated cell death, and necrosis. Microvascular dysfunction with increased vascular permeability and endothelial cell inflammation were also present. Activation of coagulation is represented by thrombi in the lumens of the glomerular capillaries.

DIAGNOSIS

The diagnosis was ischemia reperfusion injury responsible for delayed graft function (DGF).

INTERVENTIONS

Immunosuppressive regimen was delayed use of calcineurin inhibitors, mycophenolate mofetil, and corticosteroids.

OUTCOMES

At 1 year post transplant, the patient has a renal autonomy with a graft function stable and physiological proteinuria.

LESSONS

The main clinical consequences of IRI in kidney transplant are DGF, acute and chronic graft rejection, and chronic graft dysfunction. Reducing IRI is one of the most relevant challenge in kidney transplantation.

Ischemic acute kidney injury and klotho in renal transplantation

Post-transplant ischemic acute kidney injury (AKI), secondary to ischemia reperfusion injury (IRI), is a major problem influencing on the short and long term graft and patient survival. Many molecular and cellular modifications are observed during IRI, for example, tissue damage result production of reactive oxygen species (ROS), cytokines, chemokines, and leukocytes recruitment which are activated by NF-κB (nuclear factor kappa B) signaling pathway. Therefore, inhibiting these processes can significantly protect renal parenchyma from tissue damage. Klotho protein, mainly produced in distal convoluted tubules (DCT), is an anti-senescence protein. There is increasing evidence to confirm a relationship between Klotho levels and renal allograft function. Many studies have also demonstrated that expression of the Klotho gene would be down regulated with IRI, so it will be used as an early biomarker for acute kidney injury after renal transplantation. Other studies suggest that Klotho may have a renoprotective effect for attenuating of kidney injury. In this review, we will discuss pathophysiology of IRI-induced acute kidney injury and its relation with klotho level in renal transplantation procedure.

Update on ischemia-reperfusion injury in kidney transplantation: Pathogenesis and treatment

Ischemia/reperfusion injury is an unavoidable relevant consequence after kidney transplantation and influences short term as well as long-term graft outcome. Clinically ischemia/reperfusion injury is associated with delayed graft function, graft rejection, chronic rejection and chronic graft dysfunction. Ischemia/reperfusion affects many regulatory systems at the cellular level as well as in the renal tissue that result in a distinct inflammatory reaction of the kidney graft. Underlying factors of ischemia reperfusion include energy metabolism, cellular changes of the mitochondria and cellular membranes, initiation of different forms of cell death-like apoptosis and necrosis together with a recently discovered mixed form termed necroptosis. Chemokines and cytokines together with other factors promote the inflammatory response leading to activation of the innate immune system as well as the adaptive immune system. If the inflammatory reaction continues within the graft tissue, a progressive interstitial fibrosis develops that impacts long-term graft outcome. It is of particular importance in kidney transplantation to understand the underlying mechanisms and effects of ischemia/reperfusion on the graft as this knowledge also opens strategies to prevent or treat ischemia/reperfusion injury after transplantation in order to improve graft outcome.

Delivery of intercellular adhesion molecule-1 antisense oligonucleotides using a topical hydrogel tissue sealant in a murine partial nephrectomy/ischemia model

OBJECTIVES

Ischemia/reperfusion injury is a leading cause of renal damage which can be improved with antisense oligonucleotide gene therapy. We have shown that polyethylene glycol (PEG) hydrogel, which also functions as a tissue sealant, is an effective topical delivery vehicle for oligonucleotides in a murine partial nephrectomy model. The objective of this study was to use and evaluate this method against intercellular adhesion molecule-1 (ICAM-1) to prevent tissue damage.

METHODS

Sixty mice underwent left upper pole partial nephrectomy with 45 minutes of warm ischemia, randomized to treatment with 50 microg ICAM-1 antisense oligonucleotides embedded in PEG hydrogel, no therapy, or sham surgery. Kidneys were harvested at 24 hours and 3, 4, and 5 days. The specimens were evaluated by quantitative real-time polymerase chain reaction (qRT-PCR) for ICAM-1 messenger ribonucleic acid (mRNA), immunohistochemical staining for ICAM-1 protein, and standard histology.

RESULTS

At 24 hours, qRT-PCR and immunohistochemistry data showed a significant reduction in ICAM-1 mRNA and protein expression in the antisense group versus the ischemia group, but no difference at 3 to 5 days. Histologically there was reduced inflammation and necrosis in the cortex at 24 hours. The outer and inner medulla also showed improvement at 3 to 5 days in the antisense group as opposed to the ischemia group.

CONCLUSIONS

Topical PEG hydrogel delivery of antisense ICAM-1 oligonucleotides demonstrated decreased ICAM-1 mRNA expression, reduced ICAM-1 protein staining, and decreased cellular damage. The application of gene therapy through this novel topical delivery system holds potential for a highly specific, localized method of preventing tissue damage after ischemia/reperfusion injury.

The relationship between surgeon and basic scientist

Basic science research has always been the cornerstone of a solid academic career, even for surgeons. In the past, many cardiothoracic and cardiovascular surgeons have used the large animal laboratory to design surgical operations, refine extracorporeal circulation, improve myocardial protection or simply validate clinical concepts. Today, funding for large animal research has almost disappeared. The basic science areas of 'cellular, molecular, genomics or gene therapy' must be involved to be considered for national or even local funding. This endeavor requires a new generation of surgical scientists and perhaps even more importantly, a new environment for the performance of such research. Academic surgery does not exist without active and long-standing commitment to research. Clinical research focusing on patient outcome remains an important task of the academic surgeon but this paper will focus on the relationship between surgeons and basic scientists and shall concentrate primarily on translational research and its challenge now and in the future. The collaboration between basic scientist and clinician is more essential than ever, because the society still optimally rewards science that has potential clinical applicability [1]. Even within surgical departments, active support and very close contact with PhDs can be essential for the clinical faculty members to be productive, using cellular and molecular techniques. In cardiovascular medicine and biology, there is a great potential to prevent or treat diseases with these techniques. The potential to modify ischemia-reperfusion, inflammation, angiogenesis, restenosis, organ tolerance or cardiomyocyte transplantation to remodel ventricles will be accomplished by a better understanding of cardiovascular biology. Surgeons must plan for a speciality that may look quite different in the next future.