Sourabh Chand

Meta-Analysis of Calcineurin-Inhibitor-Sparing Regimens in Kidney Transplantation

Calcineurin-inhibitor-sparing strategies in kidney transplantation may spare patients the adverse effects of these drugs, but the efficacy of these strategies is unknown. Here, we conduct a meta-analysis to assess outcomes associated with reducing calcineurin inhibitor exposure from the time of transplantation. We search Medline, Embase, and Cochrane Register of Controlled Trials for randomized controlled trials published between 1966 and 2010 that compared de novo calcineurin-inhibitor-sparing regimens to calcineurin-inhibitor-based regimens. In this analysis, we include 56 studies comprising data from 11337 renal transplant recipients. Use of the contemporary agents belatacept or tofacitinib, in combination with mycophenolate, decreased the odds of overall graft failure (OR 0.61; 95% CI 0.39-0.96; P = 0.03). Similarly, minimization of calcineurin inhibitors in combination with various induction and adjunctive agents reduces the odds of graft failure (OR 0.73; 95% CI 0.58-0.92; P = 0.009). Conversely, the use of inhibitors of mammalian target of rapamycin (mTOR), in combination with mycophenolate, increases the odds of graft failure (OR 1.43; 95% CI 1.08-1.90; P = 0.01). Calcineurin-inhibitor-sparing strategies are associated with less delayed graft function (OR 0.89; 95% CI 0.80-0.98; P = 0.02), improved graft function, and less new-onset diabetes. The more contemporary protocols did not seem to increase rates of acute rejection. In conclusion, this meta-analysis suggests that reducing exposure to calcineurin inhibitors immediately after kidney transplantation may improve clinical outcomes.

Biology of the renal pericyte

Pericytes are cells of mesenchymal origin that are intimately involved in the development and stabilization of vascular networks. Novel studies of their role in inflammation have identified that pericytes are not only major contributors to the activated matrix depositing myofibroblast populations seen in progressive renal fibrosis but perhaps even more importantly, the detachment of renal pericytes from the vasculature contributes to the microvasculature rarefaction and subsequent hypoxia associated with chronic kidney disease. In this review, our current understanding of the functioning of renal pericytes will be considered and set in the context of the wider literature that is currently available on this neglected population of cells.

Assessing and comparing rival definitions of delayed renal allograft function for predicting subsequent graft failure.

Background. The traditional definition of delayed graft function (DGF) rests on dialysis requirement during the first postoperative week. Subsequently, a more objective and “functional” definition of DGF (fDGF) has been proposed as an alternative to this dialysis-based definition of DGF (dDGF) and defined as a failure of the serum creatinine to decrease by at least 10% daily on 3 successive days during the first week posttransplantation, irrespective of dialysis requirement. However, an association between fDGF and long-term graft failure has not been fully established, and it is unknown whether fDGF is a better marker of subsequent outcomes than dDGF. Methods. We studied 750 adult deceased donor kidney transplant recipients (1996–2006) and analyzed the association between these two DGF definitions and long-term graft outcome. Results. Univariable associations with death-censored graft failure were seen for both dDGF and fDGF (hazard ratio [HR] 1.59; 95% confidence interval [CI] 1.16–2.18; P=0.004 and HR 1.72; 95% CI 1.26–2.36; P=0.001, respectively). On bivariable analysis (dDGF vs. fDGF), dDGF lost significance, whereas the effect of fDGF persisted (HR 1.52; 95%CI 1.03–2.25; P=0.04). This was also the case in a multivariable model, where fDGF but not dDGF was significantly associated with graft failure (HR 1.47; 95%CI 1.06–2.03; P=0.02). Results were similar for overall graft failure. Conclusions. This study confirms the utility of fDGF as an early marker of subsequent inferior allograft outcomes, suggesting superiority over the traditional (often subjective) dialysis-based definition. Wider adoption of the fDGF definition should be considered, both as a risk-stratification tool in clinical practice and a clinical trial endpoint.

Cytomegalovirus-Associated CD4(+) CD28(null) Cells in NKG2D-Dependent Glomerular Endothelial Injury and Kidney Allograft Dysfunction.

Emerging data suggest that expansion of a circulating population of atypical, cytotoxic CD4+ T cells lacking costimulatory CD28 (CD4+CD28null cells) is associated with latent cytomegalovirus (CMV) infection. The purpose of the current study was to increase the understanding of the relevance of these cells in 100 unselected kidney transplant recipients followed prospectively for a median of 54 months. Multicolor flow cytometry of peripheral blood mononuclear cells before transplantation and serially posttransplantation was undertaken. CD4+CD28null cells were found predominantly in CMV‐seropositive patients and expanded in the posttransplantation period. These cells were predominantly effector‐memory phenotype and expressed markers of endothelial homing (CX3CR1) and cytotoxicity (NKG2D and perforin). Isolated CD4+CD27−CD28null cells proliferated in response to peripheral blood mononuclear cells previously exposed to CMV‐derived (but not HLA‐derived) antigens and following such priming incubation with glomerular endothelium resulted in signs of endothelial damage and apoptosis (release of fractalkine and von Willebrand factor; increased caspase 3 expression). This effect was mitigated by NKG2D‐blocking antibody. Increased CD4+CD28null cell frequencies were associated with delayed graft function and lower estimated glomerular filtration rate at end follow‐up. This study suggests an important role for this atypical cytotoxic CD4+CD28null cell subset in kidney transplantation and points to strategies that may minimize the impact on clinical outcomes.

Genetic polymorphisms and kidney transplant outcomes

Purpose of reviewGene polymorphism studies are growing at a quasiexponential rate and aim to improve immediate and long-term outcomes in renal transplantation. This review highlights recent evidence and potential future directions for genetic research studies. Recent findingsStudies are largely based on immunity, inflammation and pharmacogenetics, investigating mostly ‘surrogate’ outcomes with sometimes conflicting results. However, the last 12 months has also heralded the emergence of important genome-wide association studies on transplantation, more robust replicated multicentre analyses of candidate gene variants, meta-analyses, and an increasing interest in copy number variation and donor genetics. SummaryThese studies set the scene for further investigation, aiming to understand pathways of disease and biomarkers of risk, and are leading to a greater understanding of the biology of transplantation. Future studies will require focus on donor : recipient and gene : environment interactions, and an integrated approach of ‘transplantomics’ to evaluate long-term outcomes in multinational collaborations.

The Spectrum of Renal Allograft Failure

Background Causes of “true” late kidney allograft failure remain unclear as study selection bias and limited follow-up risk incomplete representation of the spectrum. Methods We evaluated all unselected graft failures from 2008–2014 (n = 171; 0–36 years post-transplantation) by contemporary classification of indication biopsies “proximate” to failure, DSA assessment, clinical and biochemical data. Results The spectrum of graft failure changed markedly depending on the timing of allograft failure. Failures within the first year were most commonly attributed to technical failure, acute rejection (with T-cell mediated rejection [TCMR] dominating antibody-mediated rejection [ABMR]). Failures beyond a year were increasingly dominated by ABMR and ‘interstitial fibrosis with tubular atrophy’ without rejection, infection or recurrent disease (“IFTA”). Cases of IFTA associated with inflammation in non-scarred areas (compared with no inflammation or inflammation solely within scarred regions) were more commonly associated with episodes of prior rejection, late rejection and nonadherence, pointing to an alloimmune aetiology. Nonadherence and late rejection were common in ABMR and TCMR, particularly Acute Active ABMR. Acute Active ABMR and nonadherence were associated with younger age, faster functional decline, and less hyalinosis on biopsy. Chronic and Chronic Active ABMR were more commonly associated with Class II DSA. C1q-binding DSA, detected in 33% of ABMR episodes, were associated with shorter time to graft failure. Most non-biopsied patients were DSA-negative (16/21; 76.1%). Finally, twelve losses to recurrent disease were seen (16%). Conclusion This data from an unselected population identifies IFTA alongside ABMR as a very important cause of true late graft failure, with nonadherence-associated TCMR as a phenomenon in some patients. It highlights clinical and immunological characteristics of ABMR subgroups, and should inform clinical practice and individualised patient care.

Endothelial Nitric Oxide Synthase Single Nucleotide Polymorphism and Left Ventricular Function in Early Chronic Kidney Disease

Background Chronic kidney disease (CKD) is associated with accelerated cardiovascular disease and heart failure. Endothelial nitric oxide synthase (eNOS) Glu298Asp single nucleotide polymorphism (SNP) genotype has been associated with a worse phenotype amongst patients with established heart failure and in patients with progression of their renal disease. The association of a cardiac functional difference in non-dialysis CKD patients with no known previous heart failure, and eNOS gene variant is investigated. Methods 140 non-dialysis CKD patients, who had cardiac magnetic resonance (CMR) imaging and tissue doppler echocardiography as part of two clinical trials, were genotyped for eNOS Glu298Asp SNP retrospectively. Results The median estimated glomerular filtration rate (eGFR) was 50mls/min and left ventricular ejection fraction (LVEF) was 74% with no overt diastolic dysfunction in this cohort. There were significant differences in LVEF across eNOS genotypes with GG genotype being associated with a worse LVEF compared to other genotypes (LVEF: GG 71%, TG 76%, TT 73%, p = 0.006). After multivariate analysis, (adjusting for age, eGFR, baseline mean arterial pressure, contemporary CMR heart rate, total cholesterol, high sensitive C-reactive protein, body mass index and gender) GG genotype was associated with a worse LVEF, and increased LV end-diastolic and systolic index (p = 0.004, 0.049 and 0.009 respectively). Conclusions eNOS Glu298Asp rs1799983 polymorphism in CKD patients is associated with relevant sub-clinical cardiac remodelling as detected by CMR. This gene variant may therefore represent an important genetic biomarker, and possibly highlight pathways for intervention, in these patients who are at particular risk of worsening cardiac disease as their renal dysfunction progresses.

Caveolin-1 Single Nucleotide Polymorphism in Antineutrophil Cytoplasmic Antibody Associated Vasculitis

Objective Immunosuppression is cornerstone treatment of antineutrophil cytoplasmic antibody associated vasculitis (AAV) but is later complicated by infection, cancer, cardiovascular and chronic kidney disease. Caveolin-1 is an essential structural protein for small cell membrane invaginations known as caveolae. Its functional role has been associated with these complications. For the first time, caveolin-1 (CAV1) gene variation is studied in AAV. Methods CAV1 single nucleotide polymorphism rs4730751 was analysed in genomic DNA from 187 white patients with AAV from Birmingham, United Kingdom. The primary outcome measure was the composite endpoint of time to all-cause mortality or renal replacement therapy. Secondary endpoints included time to all-cause mortality, death from sepsis or vascular disease, cancer and renal replacement therapy. Validation of results was sought from 589 white AAV patients, from two European cohorts. Results The primary outcome occurred in 41.7% of Birmingham patients. In a multivariate model, non-CC genotype variation at the studied single nucleotide polymorphism was associated with increased risk from: the primary outcome measure [HR 1.86; 95% CI: 1.14-3.04; p=0.013], all-cause mortality [HR:1.83; 95% CI: 1.02-3.27; p=0.042], death from infection [HR:3.71; 95% CI: 1.28-10.77; p=0.016], death from vascular disease [HR:3.13; 95% CI: 1.07-9.10; p=0.037], and cancer [HR:5.55; 95% CI: 1.59-19.31; p=0.007]. In the validation cohort, the primary outcome rate was far lower (10.4%); no association between genotype and the studied endpoints was evident. Conclusions The presence of a CC genotype in Birmingham is associated with protection from adverse outcomes of immunosuppression treated AAV. Lack of replication in the European cohort may have resulted from low clinical event rates. These findings are worthy of further study in larger cohorts.

β Cell Glucotoxic-Associated Single Nucleotide Polymorphisms in Impaired Glucose Tolerance and New-Onset Diabetes After Transplantation

Emerging paradigms of new-onset diabetes after transplantation (NODAT) have focused on pathways and risk factors (e.g., posttransplant hyperglycemia and immunosuppressive agents) to its pathogenesis with the aim of identifying those at risk and developing preventative strategies (1). Identification of potential NODATassociated single nucleotide polymorphisms (SNPs) has increased our knowledge base of these pathways (2, 3). In particular, a recent genome-wide association study of 26 NODAT patients (and 230 controls), with subsequent de novo SNP genotyping in 57 NODAT patients (and 383 controls), discovered eight SNPs associated with pancreatic A-cell apoptosis (4). This Belfast cohort was limited to white, nondiabetic adult recipients who had received a cadaveric renal transplant between 1986 and 2005. New-onset diabetes after transplantation was defined as a new requirement for oral hypoglycemics or insulin after transplantation until August 2012. However, evidence is now emerging to identify abnormal glucose metabolism post transplantation by means of biochemical analyses including the oral glucose tolerance test (OGTT) (5, 6). We sought to examine the association of the identified eight SNPs in an independent cohort using biochemical diagnoses of impairedglucosetolerance(IGT)andNODAT. From 2009 to 2012, 112 patients were prospectively followed up over a 12-month period in a single-center adult tertiary center. To exclude preexisting diabetes, patients underwent glucose testing (minimum 8 hr fasting) immediately before transplantation and excluded if 6.1 mmol/L or higher or HbA1c of 6.5% or higher. In addition, live donor recipients underwent OGTTs within a week of transplantation. Oral glucose tolerance tests were then performed at 7 days, and then 3 months and 12 months for all renal transplants if fasting glucose was less than 7.0 mmol/L, to confirm the presence or persistence of posttransplant hyperglycemia. Impaired glucose tolerance was diagnosed if 2-hr OGTT glucose was 7.8 to 11 mmol/L. New-onset diabetes after transplantation was diagnosed if fasting glucose was 7 mmol/L or higher or 2-hr OGTT was 11.1 mmol/L or higher from day 7 onward, or HbA1c was 6.5% or higher from 3 months onward. Exclusion criteria of pretransplant diabetes and non-white ethnicity resulted in 68 patients being tested for the eight candidate SNPs (rs10484821, rs11580170, rs1836882, rs198372, rs2020902, rs2861484, rs4394754, rs7533125); genotyping was performed using Sequenom iPLEX and Taqman technologies. Event analyses using binary logistic regression was used adjusting for age, sex, baseline body mass index (BMI), and change in BMI over 12 months from transplantation. All patients had a homogenous immunosuppression regimen over the 12 months consisting of CD25 monoclonal antibody induction and maintenance tacrolimus, mycophenolic acid, and prednisolone. The cohort was aged 45 years (T15), 2.81 (T1.41) human leukocyte antigen mismatch, were 59% men, and 73% live donor recipients. Either IGT or NODAT occurred in over half the study population, with median time of onset 7 days and 18 days, respectively, after transplantation (IGT, 18/68 patients; NODAT, 18/68 patients). Significant differences were seen in the BMI change over 12 months for those who developed IGT (P=0.007) and NODAT (P=0.002) compared to those who did not. The NODAT group were also significantly older compared to those without NODAT (54 vs. 41 years; P=0.002). One candidate SNP that was found to be associated with posttransplant hyperglycemia in both cohorts was rs198372 for gene NPPA. Rs198372 genotype GG (vs. non-GG) was protective for IGT-onset on univariate (P=0.015) and multivariate analysis (OR, 0.21 [0.05Y 0.88]; P=0.033) in the adjusted model. No other SNPs demonstrated statistical significance for association with NODAT or IGT, although the power to detect an effect size of 1.5 was on average 10.2% across the tested SNPs and therefore (as expected) the possibility of a type II error certainly exists. NPPA encodes natriuretic peptides that inhibit cytokine and leptin production that are associated with inflammation and insulin resistance in human adipose tissue. Indeed, the Birmingham cohort who developed IGT exhibited an average increase in BMI of 2.3 kg/m at 1 year after transplantation, consistent with leptin level or weight gain known association (7). Elevated leptin levels increase interleukin-1A promoting Acell apoptosis in pancreatic islets and free fatty acids inducing apoptosis by caspase activation (4). McCaughan et al. (4) reported a 9.6% NODAT incidence over 12 years follow-up (57 patients with a median onset of 100 months), whereas in Birmingham at only 12 months, over 25% (18 patients) developed IGT and the same number had NODAT. This may reflect differences between the cohorts (for instance, all patients in Birmingham received maintenance CNI therapy compared with 75% in Belfast). However, it also highlights the importance of the use of detailed OGTT data in unmasking posttransplant glucose abnormalities. Also, this in turn may influence the genotype-phenotype relationship. This study supports further replication of the initial Belfast findings in regard to rs198372 as a candidate SNP for identifying patients at risk for developing posttransplant hyperglycemia and a potential biochemical pathway for manipulation.

Caveolin-1 single-nucleotide polymorphism and arterial stiffness in non-dialysis chronic kidney disease

BACKGROUND Arteriosclerosis is an independent predictor of increased cardiovascular mortality in chronic kidney disease (CKD). Histologically it is characterized by hypertrophy and fibrosis of the arterial media wall leading to increased arterial stiffness and end-organ damage. Caveolin-1 acts as an intracellular signalling pathway chaperone in human fibrotic and vascular diseases. The purpose of this study was to assess the association between caveolin-1 (CAV1) single-nucleotide polymorphism (SNP) rs4730751 and arterial stiffness as measured by arterial pulse wave velocity (PWV) in an early-stage CKD cohort and in a cohort with more severe CKD. METHODS Two prospectively maintained patient cohorts with non-dialysis CKD were studied: 144 patients in the Chronic Renal Impairment in Birmingham (CRIB) cohort and 147 patients in the Renal Impairment in Secondary Care (RIISC) cohort, with matched exclusion criteria and DNA sampling availability. At entry to each cohort database, each patients initial arterial PWV was measured, as well as their anthropomorphic and biochemical data. CAV1 rs4730751 SNP genotyping was performed using Taqman technology. RESULTS The CAV1 rs4730751 SNP CC genotype was associated with lower arterial PWV in both CRIB early stage CKD patients [8.1 versus 8.6 m/s; coefficient -0.780 (-1.412, -0.149); P = 0.016] and RIISC more advanced stage CKD patients [8.7 versus 9.4 m/s; coefficient -0.695 (-1.288, -0.102); P = 0.022]; these relationships held following adjustment for other important confounders. CONCLUSIONS This replicated study suggests potential utility of the studied CAV1 SNP as a genetic biomarker in CKD and a role for CAV1 in the development of arteriosclerosis in this setting. Further studies are warranted to further explore the basic science driving these clinical observations.