Tubular Cell Senescence in the Donated Kidney Predicts Allograft Function, but Not Donor Remnant Kidney Function, in Living Donor Kidney Transplantation

Extracellular vesicles derived from patients with antibody-mediated rejection induce tubular senescence and endothelial to mesenchymal transition in renal cells

Extracellular vesicles (EV) are emerging mediators in several diseases. However, their role in the pathophysiology of antibody-mediated allograft rejection (AMR) has been poorly investigated. Here, we investigated the role of EV isolated from AMR patients in inducing tubular senescence and endothelial to mesenchymal transition (EndMT) and analyzed their miRNA expression profile. By multiplex bead flow cytometry, we characterized the immunophenotype of plasma AMR-derived EV and found a prevalent platelet and endothelial cell origin. In vitro, AMR-derived EV induced tubular senescence by upregulating SA-β Gal and CDKN1A mRNA. Furthermore, AMR-derived EV induced EndMT. The occurrence of tubular senescence and EndMT was confirmed by analysis of renal biopsies from the same AMR patients. Moreover, AMR-derived EV induced C3 gene upregulation and CFH downregulation in tubular epithelial cells, with C4d deposition on endothelial cells. Interestingly, RNase-mediated digestion of EV cargo completely abrogated tubular senescence and EndMT. By microarray analysis, miR-604, miR-515-3p, miR-let-7d-5p, and miR-590-3p were significantly upregulated in EV from AMR group compared with transplant controls, whereas miR-24-3p and miR-29a-3p were downregulated. Therefore, EV-associated miRNA could act as active player in AMR pathogenesis, unraveling potential mechanisms of accelerated graft senescence, complement activation and early fibrosis that might lead to new therapeutic intervention.

Marine n-3 Polyunsaturated Fatty Acids and Cellular Senescence Markers in Incident Kidney Transplant Recipients: The Omega-3 Fatty Acids in Renal Transplantation (ORENTRA) Randomized Clinical Trial

Rationale & Objective

Deterioration of kidney graft function is associated with accelerated cellular senescence. Marine n-3 polyunsaturated fatty acids (PUFAs) have favorable properties that may counteract cellular senescence development and damage caused by the senescence-associated secretory phenotype (SASP) secretome. Our objective was to investigate the potential effects of marine n-3 PUFA supplementation on the SASP secretome in kidney transplant recipients.

Study Design

Exploratory substudy of the Omega-3 Fatty Acids in Renal Transplantation trial.

Setting & Participants

Adult kidney transplant recipients with a functional kidney graft (defined as having an estimated glomerular filtration rate of >30 mL/min/1.73 m²) 8 weeks after engraftment were included in this study conducted in Norway.

Analytical Approach

The intervention consisted of 2.6 g of a marine n-3 PUFA or olive oil (placebo) daily for 44 weeks. The outcome was a predefined panel of SASP components in the plasma and urine.

Results

A total of 132 patients were enrolled in the Omega-3 Fatty Acids in Renal Transplantation trial, and 66 patients were allocated to receive either the study drug or placebo. The intervention with the marine n-3 PUFA was associated with reduced plasma levels of granulocyte colony-stimulating factor, interleukin 1α, macrophage inflammatory protein 1α, matrix metalloproteinase (MMP)-1, and MMP-13 compared with the intervention in the control group.

Limitations

Post hoc analysis.

Conclusions

The results suggest that marine n-3 PUFA supplementation has mitigating effects on the plasma SASP components granulocyte colony-stimulating factor, interleukin 1α, macrophage inflammatory protein 1α, MMP-1, and MMP-13 in kidney transplant recipients. Future studies with kidney transplant recipients in maintenance phase, combined with an evaluation of cellular senescence markers in kidney transplant biopsies, are needed to further elucidate the potential antisenescent effect of marine n-3 PUFAs. This trial is registered as NCT01744067.

Senescent cell turnover slows with age providing an explanation for the Gompertz law

A causal factor in mammalian aging is the accumulation of senescent cells (SnCs). SnCs cause chronic inflammation, and removing SnCs decelerates aging in mice. Despite their importance, turnover rates of SnCs are unknown, and their connection to aging dynamics is unclear. Here we use longitudinal SnC measurements and induction experiments to show that SnCs turn over rapidly in young mice, with a half-life of days, but slow their own removal rate to a half-life of weeks in old mice. This leads to a critical-slowing-down that generates persistent SnC fluctuations. We further demonstrate that a mathematical model, in which death occurs when fluctuating SnCs cross a threshold, quantitatively recapitulates the Gompertz law of mortality in mice and humans. The model can go beyond SnCs to explain the effects of lifespan-modulating interventions in Drosophila and C. elegans, including scaling of survival-curves and rapid effects of dietary shifts on mortality.

One of the underlying causes of aging is the accumulation of senescent cells, but their turnover rates and dynamics during ageing are unknown. Here the authors measure and model senescent cell production and removal and explore implications for mortality.

Post-transplant immunoglobulin A deposition and nephropathy in allografts

Post-transplant immunoglobulin A (IgA) nephropathy (IgAN) in the allograft is the major cause of allograft loss. Using a protocol biopsy, latent mesangial IgA deposition (IgAD) can be detected in the allograft. Latent IgAD is distinguished from IgAN by the absence of urinary abnormalities, although IgA is observed in the mesangium. However, the pathophysiology and most appropriate treatment strategy for latent mesangial IgAD in the allograft remain to be fully determined. Importantly, it is unknown whether all cases of post-transplant asymptomatic IgAD progress to symptomatic IgAN; indeed, IgA deposits disappear in some cases. The differences in allograft prognosis between asymptomatic IgAD and IgAN have also not been determined. Non-invasive methods of diagnosis of IgAD in the allograft using serological and pathological biomarkers are being developed. Possible serum biomarkers include serum galactose-deficient IgA1 (Gd-IgA1), Gd-IgA1-specific IgG and Gd-IgA1-specific IgA, and its immune complexes. Immunofluorescence analysis using Gd-IgA1 monoclonal antibody may provide a pathological biomarker. These serological and pathological biomarkers may be suitable for the characterization of the stage of IgAD. However, there is insufficient information regarding whether serological and pathological biomarkers can predict the progression of asymptomatic IgAD to symptomatic IgAN. We propose that the pathogenesis of IgAN can be defined through the clinical study of IgAD in the allograft using protocol biopsies conducted by nephrologists involved in clinical kidney transplantation.

Summary of the 2018 ISN Frontiers Meeting: Kidney Disease and Cardiovascular Disease

International Society of Nephrology (ISN) Frontiers meetings build on the success of the ISN Nexus and Forefronts series by bringing together basic scientists, clinicians, and practitioners in a unique setting. This new event was organized to make more innovative science available to a global audience by removing regional barriers in accessing the latest knowledge. The first ISN Frontiers meeting was organized in partnership between the Japanese Society of Nephrology and the Japanese Society for Dialysis Therapy, which was held in Tokyo in February 2018. The meeting focused on the topic “Kidney Disease & Cardiovascular Disease,” which covered a broad range of scientific and clinical fields, including nephrology, cardiovascular diseases, dialysis, transplantation, chronic kidney disease (CKD)–mineral bone disease (MBD), diabetes, pediatric nephrology, nutrition, pharmacology, and nursing. A total of 1584 active physicians and scientists from 64 countries attended the meeting, and a number of leading physician scientists from different and related disciplines of clinical and basic research described and reviewed recent discoveries. This report summarizes the main highlights of the meeting lectures.