MicroRNAs in AKI and Kidney Transplantation

MicroRNAs are epigenetic regulators of gene expression at the posttranscriptional level. They are involved in intercellular communication and crosstalk between different organs. As key regulators of homeostasis, their dysregulation underlies several morbidities including kidney disease. Moreover, their remarkable stability in plasma and urine makes them attractive biomarkers. Beyond biomarker studies, clinical microRNA research in nephrology in recent decades has focused on the discovery of specific microRNA signatures and the identification of novel targets for therapy and/or disease prevention. However, much of this research has produced equivocal results and there is a need for standardization and confirmation in prospective trials. This review aims to provide an overview of general concepts and available clinical evidence in both the pathophysiology and biomarker fields for the role of microRNA in AKI and kidney transplantation.

Histological characteristics of Acute Tubular Injury during Delayed Graft Function predict renal function after renal transplantation

Acute Tubular Injury (ATI) is the leading cause of Delayed Graft Function (DGF) after renal transplantation (RTX). Biopsies taken 1 week after RTX often show extensive tubular damage, which in most cases resolves due to the high regenerative capacity of the kidney. Not much is known about the relation between histological parameters of renal damage and regeneration immediately after RTX and renal outcome in patients with DGF. We retrospectively evaluated 94 patients with DGF due to ATI only. Biopsies were scored for morphological characteristics of renal damage (edema, casts, vacuolization, and dilatation) by three independent blinded observers. The regenerative potential was quantified by tubular cells expressing markers of proliferation (Ki67) and dedifferentiation (CD133). Parameters were related to renal function after recovery (CKD-EPI 3, 6, and 12 months posttransplantation). Quantification of morphological characteristics was reproducible among observers (Kendall's W ≥ 0.56). In a linear mixed model, edema and casts significantly associated with eGFR within the first year independently of clinical characteristics. Combined with donor age, edema and casts outperformed the Nyberg score, a well-validated clinical score to predict eGFR within the first year after transplantation (R2  = 0.29 vs. R2  = 0.14). Although the number of Ki67+ cells correlated to the extent of acute damage, neither CD133 nor Ki67 correlated with renal functional recovery. In conclusion, the morphological characteristics of ATI immediately after RTX correlate with graft function after DGF. Despite the crucial role of regeneration in recovery after ATI, we did not find a correlation between dedifferentiation marker CD133 or proliferation marker Ki67 and renal recovery after DGF.

Outcomes and challenges of a kidney transplant programme at Groote Schuur Hospital, Cape Town: A South African perspective

Introduction

Access to dialysis and transplantation in the developing world remains limited. Therefore, optimising renal allograft survival is essential. This study aimed to evaluate clinical outcomes and identify poor prognostic factors in the renal transplant programme at Groote Schuur Hospital [GSH], Cape Town.     

Method

Data were collected on all patients who underwent a kidney transplant at GSH from 1st July 2010 to the 30 June 2015. Analyses were performed to assess baseline characteristics, graft and patient survival, as well as predictors of poor outcome.    

Results

198 patients were transplanted. The mean age was 38 +/- 10.5 years, 127 (64.1%) were male, and 86 (43.4%) were of African ethnicity. Deceased donor organs were used for 130 (66.7%) patients and living donors for 65 (33.3%). There were > 5 HLA mismatches in 58.9% of transplants. Sepsis was the commonest cause of death and delayed graft function [DGF] occurred in 41 (21.4%) recipients. Patient survival was 90.4% at 1 year and 83.1% at 5 years. Graft survival was 89.4% at 1 year and 80.0% at 5 years. DGF (HR 2.83 (1.12–7.19), p value = 0.028) and recipient age > 40 years (HR 3.12 (1.26–7.77), p value = 0.014) were predictors of death.

Conclusion

Despite the high infectious burden, stratified immunosuppression and limited tissue typing this study reports encouraging results from a resource constrained transplant programme in South Africa. Renal transplantation is critical to improve access to treatment of end stage kidney disease where access to dialysis is limited.

Use of a Targeted Urine Proteome Assay (TUPA) to identify protein biomarkers of delayed recovery after kidney transplant

PURPOSE

Development of delayed graft function (DGF) following kidney transplant is associated with poor outcomes. An ability to rapidly identify patients with DGF versus those with immediate graft function (IGF) may facilitate the treatment of DGF and the research needed to improve prognosis. The purpose of this study was to use a Targeted Urine Proteome Assay to identify protein biomarkers of delayed recovery from kidney transplant.

EXPERIMENTAL DESIGN

Potential biomarkers were identified using the Targeted Urine Proteome (MRM) Assay to interrogate the relative DGF/IGF levels of expression of 167 proteins in urine taken 12-18 h after kidney implantation from 21 DGF, 15 SGF (slow graft function), and 16 IGF patients. An iterative Random Forest analysis approach evaluated the relative importance of each biomarker, which was then used to identify an optimum biomarker panel that provided the maximum sensitivity and specificity with the least number of biomarkers.

CONCLUSIONS AND CLINICAL RELEVANCE

Four proteins were identified that together distinguished DGF with a sensitivity of 77.4%, specificity of 82.6%, and AUC of 0.891. This panel represents an important step toward identifying DGF at an early stage so that more effective treatments can be developed to improve long-term graft outcomes.

Identification of Molecular Markers of Delayed Graft Function Based on the Regulation of Biological Ageing

Introduction

Delayed graft function is a prevalent clinical problem in renal transplantation for which there is no objective system to predict occurrence in advance. It can result in a significant increase in the necessity for hospitalisation post-transplant and is a significant risk factor for other post-transplant complications.

Methodology

The importance of microRNAs (miRNAs), a specific subclass of small RNA, have been clearly demonstrated to influence many pathways in health and disease. To investigate the influence of miRNAs on renal allograft performance post-transplant, the expression of a panel of miRNAs in pre-transplant renal biopsies was measured using qPCR. Expression was then related to clinical parameters and outcomes in two independent renal transplant cohorts.

Results

Here we demonstrate, in two independent cohorts of pre-implantation human renal allograft biopsies, that a novel pre-transplant renal performance scoring system (GRPSS), can determine the occurrence of DGF with a high sensitivity (>90%) and specificity (>60%) for donor allografts pre-transplant, using just three senescence associated microRNAs combined with donor age and type of organ donation.

Conclusion

These results demonstrate a relationship between pre-transplant microRNA expression levels, cellular biological ageing pathways and clinical outcomes for renal transplantation. They provide for a simple, rapid quantitative molecular pre-transplant assay to determine post-transplant allograft function and scope for future intervention. Furthermore, these results demonstrate the involvement of senescence pathways in ischaemic injury during the organ transplantation process and an indication of accelerated bio-ageing as a consequence of both warm and cold ischaemia.

Oxidative stress in kidney transplant biopsies

OBJECTIVES

Kidney allograft biopsies are performed after kidney transplant to determine graft dysfunction. We aimed to define and measure the oxidative stress occurring in these biopsies and compared these biopsies with donor pretransplant biopsies.

MATERIALS AND METHODS

The biopsy procedure was done according to the unit protocol. A core of tissue was taken for research purposes only when it was safe enough to proceed for an extra core. Common indications for biopsy were acute or chronic graft dysfunction, delayed graft function, acute cellular rejection, and calcineurin toxicity. There were 17 pretransplant biopsies taken from deceased-donor kidneys. Biopsy specimens were snap frozen immediately in liquid nitrogen and stored at -70 °C. Samples were processed for Western blot and tested for markers of oxidative stress.

RESULTS

There were 61 biopsies analyzed. Oxidative stress enzymes were evaluated by Western blot including catalase, manganese superoxide dismutase, copper zinc superoxide dismutase, thioredoxin reductase, and thioredoxin. Upregulation of most antioxidant enzymes was observed in pretransplant biopsies. Increased expression of manganese superoxide dismutase was observed in donor kidneys and kidneys with acute cellular rejection and calcineurin toxicity. Copper zinc superoxide dismutase and catalase were elevated in donor and acute cellular rejection biopsies. Thioredoxin was elevated in donor biopsies and thioredoxin reductases were elevated in donor biopsies and biopsies with acute cellular rejection and calcineurin toxicity.

CONCLUSIONS

The kidney allograft biopsies showed that oxidative stress levels were elevated during allograft dysfunction in all biopsies regardless of diagnosis, but not significantly. The levels also were elevated in pretransplant biopsies. The study showed that oxidative stress is involved in various acute injuries occurring within the allograft.

Tetrahydrobiopterin ameliorates hepatic ischemia-reperfusion Injury by coupling with eNOS in mice

BACKGROUND

In the liver, eNOS appears to have a central role in protecting against ischemia/reperfusion (I/R) injury. We hypothesized that tetrahydrobiopterin (BH4) would protect livers subjected to I/R injury by coupling with eNOS.

METHODS

Chinese Kun Ming (KM) mice were subjected to 60 min of 70% hepatic ischemia 30 min after the administration of BH4 or saline. After reperfusion, survival was evaluated. The histologic appearance and ALT, BH4, nitrite/nitrate, 8-isoprostane, and eNOS protein expression levels were measured.

RESULTS

The 1-wk survival rate was 66.67% in the BH4 group and 33.33% in the saline group. The serum ALT values in the BH4 group 1, 3, 6, 12, and 24 h after reperfusion were significantly lower than those of the saline group. A histologic examination of the liver revealed only a small necrotic area in the BH4 group as opposed to massive necrosis in the saline group. The percentage values of the hepatic necrotic area 24 h after reperfusion were significantly less for the BH4 group than for the saline group. The nitrite/nitrate levels in the liver tissue were significantly increased by ~2-fold in the BH4 group compared with the saline group. The free radical indicator 8-isoprostane was reduced approximately 50% in the BH4 group compared with the saline group. Western blotting showed that the level of eNOS protein between the groups was not significantly different.

CONCLUSIONS

BH4 significantly improved the survival rate by reducing liver failure. This was supported by the histologic findings, and the mechanism was explored. According to the results, we suggest that BH4 prevents liver damage from I/R injury by attenuating reactive oxygen species and increasing NO synthesis, and might provide a novel and promising therapeutic option for preventing I/R injury.

[Vitamin D in the treatment of cardiorenal syndrome in patients with chronic nephropathy]

AIM

To determine place of vitamin D in prevention and treatment of cardiorenal syndrome (CRS) and chronic allograft nephropathy (CAN) in the aspect of myocardial and renal reparation.

METHODS AND MATERIAL

In Russia and the Netherlands we included in a randomized placebo controlled study 120 vitamin D deficient [25(OH) vitamin D<40 mol/l] recipients of asystolic and cadaveric donors. Patients were divided in 4 groups: paricalcitol (2-4 g/day) group (n=28), calcitriol (1-6 g/day orally) group (n=28), diet (1200-1800 IU/day of vitamin D with multivitamins and from foodstuffs) group (n=26), placebo with diet control group (n=27).

RESULTS

After 180 days degree of CAN according to the Banff classification was 1.24 and 1.22 in paricalcitol and calcitriol groups, respectively, compared with 1.43 and 1.68 in diet and placebo groups, respectively (p<0.05). Glomerular filtration rate (GFR) changed from 46.7 to 84.4, 81.4, 76.8, and 54.5 ml/min/1.73 m3 in paricalcitol, calcitriol, diet and placebo groups, respectively. Fluorescence activated cell scanning (FACS) analysis allowed to detect quantitative induction of SP+ cells amounting 7.4, 2.9 and 1.2%; 7.2, 2.7; and 1.1%; 6.1, 2.9 and 1.2%; 9.3, 1.3 and 0.7% of peripheral blood progenitors, renal epithelial cells, and cardiomyocytes in paricalcitol, calcitriol, diet and placebo groups, respectively. Levels of CD133, CD34, CD73, and CD105 were significantly elevated in patients of paricalcitol (median 161, range 0-834 copies), calcitriol (163, 0-721), and diet (119, 0-401) groups, compared with the placebo group (0,0-41), p<0.01. Level of nuclear vitamin D receptor (VDR) protein in renal tissue homogenizate and myocardium achieved 584, 599, 478, and 333 mole VRD/mg and 801, 715, 654, and 389 Φmole VRD/mg of protein in paricalcitol, calcitriol, diet and placebo groups, respectively (p<0.01). Circulating progenitor stem cells demonstrated comparatively high level of VDR expression--529, 526, 401, and 211 mole VRD/mg in CD133, CD34 cells; 432, 414, 303, and 290 mole VRD/mg in CD73, CD105 cells; 549, 558, 442, and 302 φmole VRD/mg in SP+ cells in paricalcitol, calcitriol, diet and placebo groups, respectively (p<0.05). Hypercalcemia was detected in 4(14%) patients in calcitriol group (p<0.001). Under influence of antihypertensive therapy arterial pressure decreased after transplantation from 180/101 to 143/87, 141/94, 147,102, and 165/101 mm Hg in paricalcitol, calcitriol, diet and placebo groups, respectively (p<0.01). NYHA heart failure functional class changed from 2.3 to 1.8, 1.9, 1.9, and 2.5 in paricalcitol, calcitriol, diet and placebo groups, respectively (p<0.01). In 6 months after transplantation average CCS scores were 533 (0-998), 611 (0-1712), 524 (122-1278) and 990 (120-1800) cells in paricalcitol, calcitriol, diet and placebo groups, respectively (p<0.05).

CONCLUSIONS

Vitamin D is an effective mean of prevention and treatment of CRS and CAN, stimulator of reparation of renal and myocardial tissues. Optimal for wide clinical practice is the use of active vitamin D analog paricalcitol (2-4 g/day) as well as special diet with multivitamins (up to 1800 IU of cholecalciferol).

[The state of lipid peroxidation and antioxidant defense system in recipients of renal allotransplant]

The peroxidal oxidation of lipids (POL) and antioxidant defense (AOD) system state in the patients blood before renal transplantation performing and on the fourth day after it were studied, depending on kind of familial or potential agonal with beating (DBH) or nonbeating (DNBH) heart donor applied and the presence of complications--delayed renal autotransplant (RAT) function and acute reaction of rejection (ARR). In chronic renal insufficiency, RAT transplantation from cadaver, DNBH and ARR the POL processes intensification and AOD system activity lowering were noted.

Association of donor inflammation- and apoptosis-related genotypes and delayed allograft function after kidney transplantation

BACKGROUND

Delayed renal allograft survival (delayed graft function [DGF]) after deceased donor kidney transplantation is associated with an increased risk of allograft loss. Inflammatory response and apoptosis are associated with increased risk of DGF.

STUDY DESIGN

Cross-sectional study.

SETTING & PARTICIPANTS

We first recruited 616 recipients of kidneys from 512 deceased kidney donors, and donor DNA was genotyped. These recipients, who were included in a prospective cohort study of 9 transplant centers in the Delaware Valley region, had their DGF outcome obtained through medical record abstraction. We then identified the recipient (n = 349) of the contralateral deceased kidney donor, if not part of the cohort, through the US Renal Data System registry. The final cohort consisted of 965 recipients of deceased donor kidneys from 512 donors.

PREDICTORS

Donor single-nucleotide polymorphisms in genes for tumor necrosis factor alpha (TNF), transforming growth factor beta1 (TGFB1), interleukin 10 (IL10), p53 (TP53), and heme oxygenase 1 (HMOX1).

OUTCOMES

DGF, defined as the need for dialysis therapy in the first week posttransplantation. Secondary outcomes included acute rejection and estimated glomerular filtration rate.

MEASUREMENTS

Information for DGF, acute rejection, and estimated glomerular filtration rate for recipients in the Delaware Valley Cohort was obtained through medical record abstraction. For other recipients, information for DGF was obtained from United Network for Organ Sharing forms and Centers for Medicare & Medicaid Services claims in the US Renal Data System registry.

RESULTS

No association was detected between the TGFB1, IL10, TP53, and HMOX1 genes and DGF. The G allele of the TNF polymorphism rs3093662 was associated with DGF in an adjusted analysis (odds ratio, 1.85 compared with A allele; 95% confidence interval, 1.16 to 2.96; P = 0.01). However, this association did not achieve statistical significance after adjusting for multiple comparisons.

LIMITATIONS

Inadequate sample size for infrequent genotypes and multiple comparisons.

CONCLUSION

Because of the low frequency of donor single-nucleotide polymorphisms of interest, a larger sample size and replication are necessary to confirm these findings on the association of donor genotypes with DGF.

Changes in cytokine concentrations in graft renal vein during reperfusion in patients with and without delayed graft function

INTRODUCTION

The impairment of organ function derived from ischemia-reperfusion injury is still an important problem in solid organ transplantation. Cell alterations induced by ischemia prime the tissue for the subsequent damage that occurs during the reperfusion phase. Despite recent advances in immunosuppressive therapy, delayed graft function (DGF) remains an important problem after kidney transplantation. Different studies have related various clinical factors to DGF, such as donor age, recipient age, cold ischemia time, initial immunosuppressive regimens. The aim of present study was to examine the changes in cytokine concentrations in graft renal vein during the reperfusion in relation to the development of delayed graft function.

MATERIAL AND METHODS

The study included 17 recipients of cadaveric renal grafts (10 males, 7 females, mean age 49 +/- 7 years, cold ischemia time 25 +/- 3 h)--8 with DGF and 9 without DGF. Levels of IL-lbeta, IL-2, IL-4, IL-6, IL-8, IL-10, IFN-gamma, TNF-beta and TNF-alpha in renal graft vein plasma during 5 first min. of reperfusion were quantified by flow-cytometry.

RESULTS

The increased concentrations ofIL-6, TNF-alpha and IL-1beta were observed during reperfusion. However there were no statistically significant differences between patients with and without DGF.

Delayed functional maturation of neonatal porcine islets in recipients under strict glycemic control

BACKGROUND

The aim of this study was to compare the functional maturation of neonatal porcine islet (NPI) grafts exposed to long-term hyperglycemia with those implanted under euglycemic conditions.

METHODS

mice Neonatal porcine islets were transplanted under the left renal capsule of diabetic SCID mice (group H), or in diabetic SCID mice who were also implanted with 500 BALB/c islets under the right renal capsule (group N). On day 42, the right kidneys were removed in both groups.

RESULTS

No animals in group H achieved euglycemia within 3 weeks after transplantation. Thus, these mice were exposed to long-term hyperglycemia. Mice in group N became euglycemic immediately after transplantation, however after removal of BALB/c grafts on day 42 they exhibited significantly higher blood glucose levels than in group H and showed glucose intolerance after glucose administration. Cellular insulin content of NPI grafts harvested on day 58 or 72 was significantly lower in group N mice compared to group H.

CONCLUSIONS

These results suggest that tight control of glycemia reduces the functional maturation of NPI grafts.