Urinary beta-2 microglobulin increases whereas TIMP-2 and IGFBP7 decline after unilateral nephrectomy in healthy kidney donors.

Early kidney injury may be detected by urinary markers, such as beta-2 microglobulin (B2M), tissue inhibitor of metalloproteinases-2 (TIMP-2), insulin-like growth factor-binding protein 7 (IGFBP7), kidney injury molecule-1 (KIM-1) and/or neutrophil gelatinase-associated lipocalin (NGAL). Of these biomarkers information on pathophysiology and reference ranges in both healthy and diseased populations are scarce. Differences in urinary levels of B2M, TIMP-2, IGFBP7, KIM-1 and NGAL were compared 24 h before and after nephrectomy in 38 living kidney donors from the REnal Protection Against Ischaemia-Reperfusion in transplantation study. Linear regression was used to assess the relation between baseline biomarker concentration and kidney function 1 year after nephrectomy. Median levels of urinary creatinine and creatinine standardized B2M, TIMP-2, IGFBP7, KIM-1, NGAL, and albumin 24 h before nephrectomy in donors were 9.4 mmol/L, 14 µg/mmol, 16 pmol/mmol, 99 pmol/mmol, 63 ng/mmol, 1390 ng/mmol and 0.7 mg/mmol, with median differences 24 h after nephrectomy of - 0.9, + 1906, - 7.1, - 38.3, - 6.9, + 2378 and + 1.2, respectively. The change of donor eGFR after 12 months per SD increment at baseline of B2M, TIMP-2, IGFBP7, KIM-1 and NGAL was: - 1.1, - 2.3, - 0.7, - 1.6 and - 2.8, respectively. Urinary TIMP-2 and IGFBP7 excretion halved after nephrectomy, similar to urinary creatinine, suggesting these markers predominantly reflect glomerular filtration. B2M and NGAL excretion increased significantly, similar to albumin, indicating decreased proximal tubular reabsorption following nephrectomy. KIM-1 did not change considerably after nephrectomy. Even though none of these biomarkers showed a strong relation with long-term donor eGFR, these results provide valuable insight into the pathophysiology of these urinary biomarkers.

A Role for Genetic Modifiers in Tubulointerstitial Kidney Diseases.

With the increased availability of genomic sequencing technologies, the molecular bases for kidney diseases such as nephronophthisis and mitochondrially inherited and autosomal-dominant tubulointerstitial kidney diseases (ADTKD) has become increasingly apparent. These tubulointerstitial kidney diseases (TKD) are monogenic diseases of the tubulointerstitium and result in interstitial fibrosis and tubular atrophy (IF/TA). However, monogenic inheritance alone does not adequately explain the highly variable onset of kidney failure and extra-renal manifestations. Phenotypes vary considerably between individuals harbouring the same pathogenic variant in the same putative monogenic gene, even within families sharing common environmental factors. While the extreme end of the disease spectrum may have dramatic syndromic manifestations typically diagnosed in childhood, many patients present a more subtle phenotype with little to differentiate them from many other common forms of non-proteinuric chronic kidney disease (CKD). This review summarises the expanding repertoire of genes underpinning TKD and their known phenotypic manifestations. Furthermore, we collate the growing evidence for a role of modifier genes and discuss the extent to which these data bridge the historical gap between apparently rare monogenic TKD and polygenic non-proteinuric CKD (excluding polycystic kidney disease).

Risk of Aneurysm Rupture (ROAR) study: protocol for a long-term, longitudinal, UK multicentre study of unruptured intracranial aneurysms.

INTRODUCTION: Unruptured intracranial aneurysms (UIA) are common in the adult population, but only a relatively small proportion will rupture. It is therefore essential to have accurate estimates of rupture risk to target treatment towards those who stand to benefit and avoid exposing patients to the risks of unnecessary treatment. The best available UIA natural history data are the PHASES study. However, this has never been validated and given the known heterogeneity in the populations, methods and biases of the constituent studies, there is a need to do so. There are also many potential predictors not considered in PHASES that require evaluation, and the estimated rupture risk is largely based on short-term follow-up (mostly 1 year). The aims of this study are to: (1) test the accuracy of PHASES in a UK population, (2) evaluate additional predictors of rupture and (3) assess long-term UIA rupture rates. METHODS AND ANALYSIS: The Risk of Aneurysm Rupture study is a longitudinal multicentre study that will identify patients with known UIA seen in neurosurgery units. Patients will have baseline demographics and aneurysm characteristics collected by their neurosurgery unit and then a single aggregated national cohort will be linked to databases of hospital admissions and deaths to identify all patients who may have subsequently suffered a subarachnoid haemorrhage. All matched admissions and deaths will be checked against medical records to confirm the diagnosis of aneurysmal subarachnoid haemorrhage. The target sample size is 20 000 patients. The primary outcome will be aneurysm rupture resulting in hospital admission or death. Cox regression models will be built to test each of the study's aims. ETHICS AND DISSEMINATION: Ethical approval has been given by South Central Hampshire A Research Ethics Committee (21SC0064) and Confidentiality Advisory Group support (21CAG0033) provided under Section 251 of the NHS Act 2006. The results will be disseminated in peer-reviewed journals. TRIAL REGISTRATION NUMBER: ISRCTN17658526.

Hemizygous loss of function mutations in CLCN5 causing end-stage kidney disease without Dent disease phenotype.

Dent disease type 1 is suspected in the presence of a complete phenotype of low molecular weight (LMW) proteinuria, hypercalciuria and at least one of the following: nephrocalcinosis, nephrolithiasis, haematuria, hypophosphatemia or chronic kidney disease (CKD). We present two brothers who presented with CKD alone. In the absence of typical clinical features, further assessment of LMW proteinuria and hypercalciuria was not undertaken. Whole-genome sequencing revealed hemizygous loss of function mutations in chloride voltage-gated channel 5 (CLCN5) consistent with Dent disease. Dent disease should, therefore, be considered in patients with an incomplete phenotype, including unexplained CKD alone.

Patients' and kidney care team's perspectives of treatment burden and capacity in older people with chronic kidney disease: a qualitative study.

OBJECTIVE: Chronic kidney disease (CKD) is often a multimorbid condition and progression to more severe disease is commonly associated with increased management requirements, including lifestyle change, more medication and greater clinician involvement. This study explored patients' and kidney care team's perspectives of the nature and extent of this workload (treatment burden) and factors that support capacity (the ability to manage health) for older individuals with CKD. DESIGN: Qualitative semistructured interview and focus group study. SETTING AND PARTICIPANTS: Adults (aged 60+) with predialysis CKD stages G3-5 (identified in two general practitioner surgeries and two renal clinics) and a multiprofessional secondary kidney care team in the UK. RESULTS: 29 individuals and 10 kidney team members were recruited. Treatment burden themes were: (1) understanding CKD, its treatment and consequences, (2) adhering to treatments and management and (3) interacting with others (eg, clinicians) in the management of CKD. Capacity themes were: (1) personal attributes (eg, optimism, pragmatism), (2) support network (family/friends, service providers), (3) financial capacity, environment (eg, geographical distance to unit) and life responsibilities (eg, caring for others). Patients reported poor provision of CKD information and lack of choice in treatment, whereas kidney care team members discussed health literacy issues. Patients reported having to withdraw from social activities and loss of employment due to CKD, which further impacted their capacity. CONCLUSION: Improved understanding of and measures to reduce the treatment burden (eg, clear information, simplified medication, joined up care, free parking) associated with CKD in individuals as well as assessment of their capacity and interventions to improve capacity (social care, psychological support) will likely improve patient experience and their engagement with kidney care services.

Early remote ischaemic preconditioning leads to sustained improvement in allograft function after live donor kidney transplantation: long-term outcomes in the REnal Protection Against Ischaemia-Reperfusion in transplantation (REPAIR) randomised trial.

BACKGROUND: The REnal Protection Against Ischaemia-Reperfusion in transplantation (REPAIR) RCT examined whether remote ischaemic preconditioning (RIPC) improved renal function after living-donor kidney transplantation. The primary endpoint, glomerular filtration rate (GFR), quantified by iohexol at 12 months, suggested that RIPC may confer longer-term benefit. Here, we present yearly follow-up data of estimated GFR for up to 5 yr after transplantation. METHODS: In this double-blind, factorial RCT, we enrolled 406 adult live donor kidney transplant donor-recipient pairs in 15 European transplant centres. RIPC was performed before induction of anaesthesia. RIPC consisted of four 5 min inflations of a BP cuff on the upper arm to 40 mm Hg above systolic BP separated by 5 min periods of cuff deflation. For sham RIPC, cuff inflation to 40 mm Hg was undertaken. Pairs were randomised to sham RIPC, early RIPC only (immediately pre-surgery), late RIPC only (24 h pre-surgery), or dual RIPC (early and late RIPC). The pre-specified secondary outcome of estimated GFR (eGFR) was calculated from serum creatinine measurements, using the Chronic Kidney Disease Epidemiology Collaboration equation. Predefined safety outcomes were mortality and graft loss. RESULTS: There was a sustained improvement in eGFR after early RIPC, compared with control from 3 months to 5 yr (adjusted mean difference: 4.71 ml min-1 (1.73 m)-2 [95% confidence interval, CI: 1.54-7.89]; P=0.004). Mortality and graft loss were similar between groups (RIPC: 20/205 [9.8%] vs control 24/201 [11.9%]; hazard ratio: 0.79 [95% CI: 0.43-1.43]). CONCLUSIONS: RIPC safely improves long-term kidney function after living-donor renal transplantation when administered before induction of anaesthesia. CLINICAL TRIAL REGISTRATION: ISRCTN30083294.

Ischemic Conditioning in Kidney Transplantation.

Ischemia-reperfusion injury is a composite of the injury sustained during a period of reduced or absent blood flow to a tissue or organ and the additional insult sustained on reperfusion, which limits the amount of tissue that can be salvaged. Ischemia-reperfusion injury is the predominant insult during kidney transplantation, contributing to graft dysfunction, increased rates of acute rejection, and reduced rejection-free graft survival. In this review, we discuss the potential therapeutic benefits of a cost-effective and low-risk intervention, ischemic preconditioning, and its potential for improving kidney function following transplantation.

Clinical applications of remote ischaemic preconditioning in native and transplant acute kidney injury.

Ischaemia-reperfusion (IR) injury is a composite of the injury sustained during a period of reduced or absent blood flow to a tissue or organ and the additional insult sustained upon reperfusion that limits the amount of tissue that can be salvaged. IR injury plays a central role in both native and transplant acute kidney injury (AKI). Native AKI is associated with increased morbidity and mortality in hospital inpatients, and transplant AKI contributes to graft dysfunction, ultimately limiting graft longevity. In this review, we discuss the potential therapeutic benefits of a cost-effective and low-risk intervention, remote ischaemic preconditioning (RIPC), and its applicability in the prevention and reduction of AKI.

Characterisation of leukocytes in a human skin blister model of acute inflammation and resolution.

There is an increasing need to understand the leukocytes and soluble mediators that drive acute inflammation and bring about its resolution in humans. We therefore carried out an extensive characterisation of the cantharidin skin blister model in healthy male volunteers. A novel fluorescence staining protocol was designed and implemented, which facilitated the identification of cell populations by flow cytometry. We observed that at the onset phase, 24 h after blister formation, the predominant cells were CD16hi/CD66b+ PMNs followed by HLA-DR+/CD14+ monocytes/macrophages, CD11c+ and CD141+ dendritic cells as well as Siglec-8+ eosinophils. CD3+ T cells, CD19+ B cells and CD56+ NK cells were also present, but in comparatively fewer numbers. During resolution, 72 h following blister induction, numbers of PMNs declined whilst the numbers of monocyte/macrophages remain unchanged, though they upregulated expression of CD16 and CD163. In contrast, the overall numbers of dendritic cells and Siglec-8+ eosinophils increased. Post hoc analysis of these data revealed that of the inflammatory cytokines measured, TNF-α but not IL-1ß or IL-8 correlated with increased PMN numbers at the onset. Volunteers with the greatest PMN infiltration at onset displayed the fastest clearance rates for these cells at resolution. Collectively, these data provide insight into the cells that occupy acute resolving blister in humans, the soluble mediators that may control their influx as well as the phenotype of mononuclear phagocytes that predominate the resolution phase. Further use of this model will improve our understanding of the evolution and resolution of inflammation in humans, how defects in these over-lapping pathways may contribute to the variability in disease longevity/chronicity, and lends itself to the screen of putative anti-inflammatory or pro-resolution therapies.

Early changes in scores of chronic damage on transplant kidney protocol biopsies reflect donor characteristics, but not future graft function.

The amount of irreversible injury on renal allograft biopsy predicts function, but little is known about the early evolution of this damage. In a single-center cohort, we examined the relationship between donor-, recipient-, and transplantation-associated factors and change in a morphometric index of chronic damage (ICD) between protocol biopsies performed at implantation and at 2-3 months. We then investigated whether early delta ICD predicted subsequent biochemical outcomes. We found little evidence to support differences between the study group, who had undergone serial biopsies, and a contemporaneous control group, who had not. In allografts with serial biopsies (n = 162), there was an increase in ICD between implantation (median: 2%, IQR:0-8) and 2-3 months post-transplant (median 8% IQR:4-15; p < 0.0001). Donation from younger or live donors was independently associated with smaller early post-transplant increases in ICD. There was no evidence for a difference in delta ICD between donation after cardiac death vs. donation after brain death, nor association with length of cold ischemia. After adjustment for GFR at the time of the second biopsy, delta ICD after three months did not predict allograft function at one yr. These findings suggest that graft damage develops shortly after transplantation and reflects donor factors, but does not predict future biochemical outcomes.

Clinical applications of remote ischemic preconditioning.

Ischemia-reperfusion injury is a composite of damage accumulated during reduced perfusion of an organ or tissue and the additional insult sustained during reperfusion. Such injury occurs in a wide variety of clinically important syndromes, such as ischemic heart disease and stroke, which are responsible for a high degree of morbidity and mortality worldwide. Basic research has identified a number of interventions that stimulate innate resistance of tissues to ischemia-reperfusion injury. Here, we summarise the experimental and clinical trial data underpinning one of these "conditioning" strategies, the phenomenon of remote ischemic preconditioning.

Does the choice of phosphate binder affect trace element levels in chronic kidney disease patients treated by regular haemodialysis?

BACKGROUND: Ion exchange resins have been reported to bind copper and zinc. As the phosphate binder sevelamer hydrochloride is an ion exchange resin, we audited trace element levels in our haemodialysis cohort to determine whether sevelamer prescription affected trace element levels compared with other phosphate binders. METHODS: Samples for zinc, copper and selenium were taken in special tubes and measured by atomic absorption spectroscopy or inductively coupled plasma-mass spectrometry from 211 patients attending an inner city university hospital main dialysis centre. RESULTS: Of the patients, 12.9% were prescribed oral or intravenous trace element supplementation. Of the remainder, 5.5% of patients had low plasma copper, 37.4% low zinc and 45.6% low selenium. There was no difference in copper (16.7 ± 0.2 vs 16.8 ± 0.4 µmol/L, respectively) and zinc (12.0 ± 0.3 vs 11.6 ± 0.2 µmol/L) comparing patients prescribed sevelamer compared with other phosphate binders. Despite a high prevalence of statin prescription, total cholesterol (3.42 ± 0.12 vs 3.89 ± 0.08, P < 0.01), LDL-cholesterol (1.46 ± 0.1 vs 2.00 ± 0.07, P < 0.01) and total cholesterol/HDL-cholesterol ratio (2.82 ± 0.15 vs 3.5216.7 ± 0.2 vs 16.8 ± 0.4 µmol/L, P < 0.01) were lower in the sevelamer group compared with those prescribed other phosphate binders. On logistic regression analysis, serum zinc levels were associated with serum albumin (F 20.36, ß 0.174, CL 0.086-0.265, P < 0.001) and dialysis vintage (F 8.1, ß 0.008, CL 0.002-0.013, P = 0.005), copper levels with log CRP (F 31.4, ß 3.04, CL 0-1.97, P < 0.001) and urine volume (F 5.1, ß - 0.01, CL - 0.002-0, P = 0.024), and selenium levels with serum albumin (F 23.2, ß 0.016, CL 0.02-0.1, P < 0.001) and race (F 31.4, ß 3.62, P = 0.032), with selenium levels being greater in non-Caucasoids (0.9 ± 0.02 vs 0.76 ± 0.02 µmol/L, P < 0.01). CONCLUSIONS: Trace element and micronutrient deficiencies were relatively common in this inner city population of outpatient haemodialysis patients. However, the prescription of different phosphate binders did not have an observable effect on serum copper and zinc levels, but those prescribed sevelamer did have lower lipid profiles compared with those prescribed other phosphate binders. Trace element concentrations were more associated with albumin, a marker of general nutritional status, with some differences according to ethnicity, most likely due to differences in dietary intake.