Can protocol biopsy better inform our choices in renal transplantation?

Early and late assessment of renal allograft dysfunction using intravoxel incoherent motion (IVIM) and diffusion-weighted imaging (DWI): a prospective study

PURPOSE

To evaluate the ability of the Intravoxel Incoherent Motion (IVIM) and monoexponentially ADC in renal allograft function in the early and late phases of transplantation, and to predict their effectiveness in discrimination of the graft pathology.

METHODS

This is a prospective study included participants scanned with quantitative diffusion and perfusion sequences on a 3-T MR scanner (Philips, Ingenia); the ADC and IVIM parameters; were calculated. Correlations and regression analysis with the eGFR, transplantation periods, and pathology were assessed.

RESULTS

This study included 105 renal allograft recipients (85 males, and 20 females with mean age = 32.4 ± 11.9 years and age range = 22-61 years). There was a significant positive correlation between the whole parameters of the ADC and IVIM with eGFR however, the cortical parameters showed higher significant correlation coefficients (p < 0.001). Regression analysis revealed the most significant model can predict eGFR groups included cortical pseudo diffusion (D*) and cortical ADC (p < 0.001). In graft dysfunction eGFR was 61.5 ml/min and normal graft was 64 ml/min. This model demonstrates a high performance of an AUC 96% [0.93-0.97]. In the late transplantation, there is a higher correlation with D* compared to ADC, p-values = 0.001.

CONCLUSION

IVIM and ADC Values are significant biomarkers for renal allograft function assessment, cortical ADC, and D* had the highest performance even in situations with mild impairment that is not affect the eGFR yet as cases of proteinuria with normal eGFR. Furthermore, D* is superior to ADC in the late assessment of the renal transplant.

US payer budget impact of a microarray assay with machine learning to evaluate kidney transplant rejection in for-cause biopsies

AIM

This study evaluates the economic impact to US commercial payers of MMDx-Kidney used in conjunction with histologic evaluation of for-cause kidney transplant biopsies.

MATERIALS AND METHODS

An Excel-based model was developed to assess the cost impact of histology plus MMDx-Kidney versus histology alone for the evaluation of potential rejection in kidney transplant patients who receive a for-cause biopsy. Different model time periods were assessed, ranging from 1 to 5 years post-biopsy. A targeted literature review was used to identify parameter estimates, validated by two external clinicians with expertise in managing kidney transplant rejection. A sensitivity analysis was conducted to evaluate the relative impact of key clinical and cost parameters. In particular, the model identified the magnitude of MMDx-Kidney's impact on graft failure from rejection that would be required for MMDx-Kidney to be cost-neutral.

RESULTS

By more accurately characterizing rejection, MMDx-Kidney is estimated to increase antirejection treatment costs by $1,126 per test. Nevertheless, a break-even analysis shows that the costs of MMDx-Kidney and anti-rejection medication, as well as the costs associated with an increase in the number of patients with functioning transplants, may be offset by reductions in costs associated with graft failure (i.e. costs of hospitalizations, dialysis, and repeat transplants) over 5 years, assuming MMDx-Kidney reduces annual graft failure from rejection by at least 5%. For the base case, with a 25% relative reduction in annual rate of graft failures from rejection, MMDx-Kidney increases overall costs incurred in the first year of the model but starts generating savings by the second year of the model.

CONCLUSIONS

Compared with histologic evaluation of for-cause kidney transplant biopsies alone, the use of MMDx-Kidney in conjunction with histologic evaluation improves the diagnoses of graft dysfunction and may have the potential to generate overall savings from reductions in rejection-related graft failure.

Subclinical Rejection and Immunosuppression in Pediatric Kidney Transplant Recipients : Single Centre Study

Background: By the time of histological confirmation of rejection is achieved, renal scarring may for treatment as a realistic option . This study aims to study the subclinical pathological graft data and to evaluate the histopathological impact of different immunosuppression protocols in pediatric renal transplant recipients. Methods: This is a case series that included twenty living donor renal transplant recipients. All included cases received the classic triple immunotherapy for at least one month post-transplantation [Steroids, calconurine inhibitors (CNI), and mycofenlolic mofetile (MMF)]. Based on their immunological risk stratification; included cases were divided into 2 groups: group (A) continued on CNI based triple therapy protocol; group (B) shifted to evirolimus /low dose CNI protocol. Surveillance biopsies were done for all cases at one and four month post-transplantation. Results: One and four month biopsies revealed subclinical rejection (including borderline changes) in 4 (20%) cases and 6 (30%) cases respectively. The number of patients received tacrolimus/MMF therapy significantly increased (p=0.02) while that of patients on everloimus/low dose CNI significantly decreased (p=0.014) due to drug modifications based on four month surveillance biopsy data. Conclusion: Subclinical rejection is not uncommon in pediatric renal graft recipients which makes surveillance biopsy might be of help. Early usage of evirolimus/low CNI protocol is associated with higher rejection rate than triple therapy.

Deep sequencing of DNA from urine of kidney allograft recipients to estimate donor/recipient-specific DNA fractions

Kidney transplantation is the treatment of choice for patients with end-stage kidney failure, but transplanted allograft could be affected by viral and bacterial infections and by immune rejection. The standard test for the diagnosis of acute pathologies in kidney transplants is kidney biopsy. However, noninvasive tests would be desirable. Various methods using different techniques have been developed by the transplantation community. But these methods require improvements. We present here a cost-effective method for kidney rejection diagnosis that estimates donor/recipient-specific DNA fraction in recipient urine by sequencing urinary cell DNA. We hypothesized that in the no-pathology stage, the largest tissue types present in recipient urine are donor kidney cells, and in case of rejection, a larger number of recipient immune cells would be observed. Extensive in-silico simulation was used to tune the sequencing parameters: number of variants and depth of coverage. Sequencing of DNA mixture from 2 healthy individuals showed the method is highly predictive (maximum error < 0.04). We then demonstrated the insignificant impact of familial relationship and ethnicity using an in-house and public database. Lastly, we performed deep DNA sequencing of urinary cell pellets from 32 biopsy-matched samples representing two pathology groups: acute rejection (AR, 11 samples) and acute tubular injury (ATI, 12 samples) and 9 samples with no pathology. We found a significant association between the donor/recipient-specific DNA fraction in the two pathology groups compared to no pathology (P = 0.0064 for AR and P = 0.026 for ATI). We conclude that deep DNA sequencing of urinary cells from kidney allograft recipients offers a noninvasive means of diagnosing acute pathologies in the human kidney allograft.

Immunological risk stratification and tailored minimisation of immunosuppression in renal transplant recipients

Background

The efficacy and safety of minimisation of immunosuppression including early steroid withdrawal in kidney transplant recipients treated with Basiliximab induction remains unclear.

Methods

This retrospective cohort study reports the outcomes from 298 consecutive renal transplants performed since 1st July 2010–June 2013 treated with Basiliximab induction and early steroid withdrawal in low immunological risk patients using a simple immunological risk stratification and 3-month protocol biopsy to optimise therapy. The cohort comprised 225 low-risk patients (first transplant or HLA antibody calculated reaction frequency (CRF ≤50% with no donor specific HLA antibodies) who underwent basiliximab induction, steroid withdrawal on day 7 and maintenance with tacrolimus and mycophenolate mofetil (MMF), and 73 high-risk patients who received tacrolimus, MMF and prednisolone for the first 3 months followed by long term maintenance immunosuppression with tacrolimus and prednisolone. High-risk patients not undergoing 3-month protocol biopsy were continued on triple immunosuppression.

Results

Steroid withdrawal could be safely achieved in low immunological risk recipients with IL2 receptor antibody induction. The incidence of biopsy-proven acute rejection was 15.1% in the low-risk and 13.9% in the high-risk group (including sub-clinical rejection detected at protocol biopsy). One- year graft survival was 93.3% and patient survival 98.5% in the low-risk group, and 97.3 and 100% respectively in the high-risk group. Graft function was similar in each group at 1 year (mean eGFR 61.2 ± 23.4 mL/min low-risk and 64.6 ± 19.2 mL/min high-risk).

Conclusions

Immunosuppression regimen comprising basiliximab induction, tacrolimus, MMF and prednisolone with early steroid withdrawal in low risk patients and MMF withdrawal in high risk patients following a normal 3-month protocol biopsy is effective in limiting acute rejection episodes and produces excellent rates of patient survival, graft function and complications.

Detecting impaired function of renal allografts at the early stage after transplantation using intravoxel incoherent motion imaging

Background

Detecting renal allografts with impaired function early after renal transplantation and timely intervention are important to ensure a successful outcome.

Purpose

To detect impaired function of renal allografts at the early stage after renal transplantation using intravoxel incoherent motion imaging (IVIM).

Material and Methods

Forty-six recipients with good allograft function and 32 recipients with impaired function were included in this study. All participants were scanned with IVIM using 11 b-values on a 3-T magnetic resonance (MR) scanner; the apparent diffusion coefficient (ADC), ADC of slow diffusion (ADCslow), pseudo-diffusion (ADCfast), and perfusion fraction (f) values were calculated using a full bi-exponential model. Correlations between estimated glomerular filtration rate (eGFR) and the IVIM parameters were assessed by using Spearman correlation analysis. Receiver operating characteristics were used to assess the diagnostic utilities for detecting allografts with impaired function.

Results

The ADC, ADCslow, ADCfast, and f values of the renal cortex and the ADC and ADCslow values of the renal medulla were significantly higher in allografts with good function compared to those with impaired function (all P < 0.05). There was a significant corticomedullary difference in ADCslow, ADC, and f in all allografts. ADCfast values were higher in the cortex than in the medulla for allografts with good function but no differences were seen in allografts with impaired function ( P > 0.05). Combined use of all cortical IVIM parameters has higher efficacy in detecting renal allograft dysfunction than any single parameter (sensitivity = 90.62%; specificity = 78.26%).

Conclusion

IVIM technique may be useful for detecting renal allograft dysfunction, especially combined use of cortical parameters.

Evaluating Renal Transplant Status Using Viscoelastic Response (VisR) Ultrasound

Chronic kidney disease is most desirably and cost-effectively treated by renal transplantation, but graft survival is a major challenge. Although irreversible graft damage can be averted by timely treatment, intervention is delayed when early graft dysfunction goes undetected by standard clinical metrics. A more sensitive and specific parameter for delineating graft health could be the viscoelastic properties of the renal parenchyma, which are interrogated non-invasively by Viscoelastic Response (VisR) ultrasound, a new acoustic radiation force (ARF)-based imaging method. Assessing the performance of VisR imaging in delineating histologically confirmed renal transplant pathologies in vivo is the purpose of the study described here. VisR imaging was performed in patients with (n = 19) and without (n = 25) clinical indication for renal allograft biopsy. The median values of VisR outcome metrics (τ, relative elasticity [RE] and relative viscosity [RV]) were calculated in five regions of interest that were manually delineated in the parenchyma (outer, center and inner) and in the pelvis (outer and inner). The ratios of a given VisR metric for all possible region-of-interest combinations were calculated, and the corresponding ratios were statistically compared between biopsied patients subdivided by diagnostic categories versus non-biopsied, control allografts using the two-sample Wilcoxon test (p <0.05). Although τ ratios non-specifically differentiated allografts with vascular disease, tubular/interstitial scarring, chronic allograft nephropathy and glomerulonephritis from non-biopsied control allografts, RE distinguished only allografts with vascular disease and tubular/interstitial scarring, and RV distinguished only vascular disease. These results suggest that allografts with scarring and vascular disease can be identified using non-invasive VisR RE and RV metrics.

An integrated view of immune monitoring in vascularized composite allotransplantation

PURPOSE OF REVIEW

Vascularized composite allotransplantation (VCA) has several immunological peculiarities that imply a specific immune monitoring. Here, we provide an integrated view of current procedures of immune monitoring in VCA and potential complementary approaches learned from organ transplantation.

RECENT FINDINGS

Because the skin is highly immunogenic and is the main target of the alloimmune response, immune monitoring in VCA essentially relies on visual inspection and pathological examination of for-causes and protocol skin biopsies. Light microscopical and immunohistochemical analyses enable us to identify skin lesions that are characteristic, but not specific, of allograft rejection. Complementary approaches of immunological assessment may assist in reinforcing the diagnosis of rejection and preventing over-immunosuppression or under-immunosuppression. Such approaches can inform either on the patient's global immune status or more specifically on the B-cell-mediated or T-cell-mediated immune responses against donor antigens.

SUMMARY

Strategies that integrate both the current 'gold standards' of monitoring in VCA and a complementary multilayer immunological assessment are likely to provide the highest precision for the personalized determination of the recipients' immunological status. The objective is a tailored adaptation of immunosuppressive treatment.

Quantification of kidney fibrosis using ultrasonic shear wave elastography: experimental study with a rabbit model

OBJECTIVES

The purpose of this study was to evaluate the feasibility of ultrasonic shear wave elastography for quantification of renal fibrosis in an experimental rabbit model.

METHODS

Thirty-eight kidneys of 19 rabbits were studied and categorized into 3 groups: group I, ureter obstruction (n = 9); group II, renal vein occlusion (n = 10); and group III, normal control (n = 19). Before surgery, we measured stiffness at the renal cortex using shear wave elastography and evaluated the sonographic findings, including size, echogenicity, and resistive index. We repeated the same sonographic examinations weekly until the fourth week. The degree of histologically quantified fibrosis and the measured stiffness values were statistically compared.

RESULTS

There was no significant difference in the mean stiffness values for the renal cortex in the 3 groups before surgery (8.95 kPa in group I, 9.06 kPa in group II, and 9.74 kPa in group III; P > .05). However, the mean stiffness in each group on the last sonographic examination was significantly different (10.91 kPa in group I, 13.92 kPa in group II, and 9.77 kPa in group III; P = .003). Pathologically, the degree of fibrosis was also significantly different (3.62% in group I, 11.70% in group II, and 0.70% in group III; P< .001). The fibrosis degree and stiffness were positively correlated (ρ = 0.568; P = 0.01).

CONCLUSIONS

Tissue stiffness measured by ultrasonic shear wave elastography was positively correlated with histopathologic renal fibrosis. Ultrasonic shear wave elastography may be used as a noninvasive tool for predicting renal fibrosis.

Sterile leukocyturia is associated with interstitial fibrosis and tubular atrophy in kidney allograft protocol biopsies

Kidney allograft interstitial fibrosis and tubular atrophy (IF/TA) is associated with a poorer renal function and outcome. In the current clinical practice, an early diagnosis can only be provided by invasive tests. We aimed to investigate the association of sterile leukocyturia with Banff criteria histological findings in kidney allograft protocol biopsies. We studied 348 allograft biopsies from two different European countries performed at 8.5 + 3.5 months after transplantation. In these cases, the presence of sterile leukocyturia (Leuc+, n = 70) or no leukocyturia (Leuc-, n = 278) was analyzed and related to Banff elementary lesions. Only IF/TA was significantly different between Leuc+ and Leuc- groups. IF/TA was present in 85.7% of Leuc+ and 27.7% of Leuc- patients (p < 0.001). IF/TA patients had higher serum creatinine and presence of proteinuria (p < 0.05). Independent predictors of IF/TA were donor age, donor male sex, serum creatinine and Leuc+ (hazard ratio 18.2; 95% confidence interval, 8.1-40.7). The positive predictive value of leukocyturia for predicting IF/TA was 85.7% whereas the negative predictive value was 72.3%. These studies suggest that leukocyturia is a noninvasive and low-cost test to identify IF/TA. An early diagnosis may allow timely interventional measures directed to minimize its impact and improve graft outcome.

The urine microRNA profile may help monitor post-transplant renal graft function

Noninvasive, cost-effective biomarkers that allow accurate monitoring of graft function are needed in kidney transplantation. Since microRNAs (miRNAs) have emerged as promising disease biomarkers, we sought to establish an miRNA signature in urinary cell pellets comparing kidney transplant patients diagnosed with chronic allograft dysfunction (CAD) with interstitial fibrosis and tubular atrophy and those recipients with normal graft function. Overall, we evaluated 191 samples from 125 deceased donor primary kidney transplant recipients in the discovery, initial validation, and the longitudinal validation studies for noninvasive monitoring of graft function. Of 1733 mature miRNAs studied using microarrays, 22 were found to be differentially expressed between groups. Ontology and pathway analyses showed inflammation as the principal biological function associated with these miRNAs. Twelve selected miRNAs were longitudinally evaluated in urine samples of an independent set of 66 patients, at two time points after kidney transplant. A subset of these miRNAs was found to be differentially expressed between groups early after kidney transplant before histological allograft injury was evident. Thus, a panel of urine miRNAs was identified as potential biomarkers for monitoring graft function and anticipating progression to CAD in kidney transplant patients.

A rapid noninvasive assay for the detection of renal transplant injury

BACKGROUND

The copy number of donor-derived cell-free DNA (dd-cfDNA) in blood correlates with acute rejection (AR) in heart transplantation. We analyzed urinary dd-cfDNA as a surrogate marker of kidney transplant injury.

METHODS

Sixty-three biopsy-matched urine samples (41 stable and 22 allograft injury) were analyzed from female recipients of male donors for chromosome Y (donor)-specific dd-cfDNA. All biopsies were semiquantitatively scored by a single pathologist. Standard statistical measures of correlation and significance were used.

RESULTS

There was baseline scatter for urinary dd-cfDNA/μg urine creatinine across different patients, even at the time of stable graft (STA) function (undetected to 12.26 copies). The mean urinary dd-cfDNA in AR (20.5 ± 13.9) was significantly greater compared with STA (2.4 ± 3.3; P<0.0001) or those with chronic allograft injury (CAI; 2.4 ± 2.4; P=0.001) but no different from BK virus nephropathy (BKVN; 20.3±15.7; P=0.98). In AR and BKVN, the intrapatient drift was highly significant versus STA or CAI patients (10.3 ± 7.4 in AR; 12.3 ± 8.4 in BKVN vs. -0.5 ± 3.5 in STA and 2.3 ± 2.6 in CAI; P<0.05). Urinary dd-cfDNA correlated with protein/creatinine ratio (r=0.48; P<0.014) and calculated glomerular filtration rate (r=-0.52; P<0.007) but was most sensitive for acute allograft injury (area under the curve=0.80; P<0.0006; 95% confidence interval, 0.67-0.93).

CONCLUSION

Urinary dd-cfDNA after renal transplantation has patient specific thresholds, reflecting the apoptotic injury load of the donor organ. Serial monitoring of urinary dd-cfDNA can be a surrogate sensitive biomarker of acute injury in the donor organ but lacks the specificity to distinguish between AR and BKVN injury.

Protocol biopsies in pediatric renal transplant recipients on cyclosporine versus tacrolimus-based immunosuppression

BACKGROUND

Protocol biopsies can detect subclinical rejection and early signs of calcineurin inhibitor-induced nephrotoxicity.

METHODS

In a prospective study, protocol biopsies 3 and 12 months after transplant in transplanted children from two centers were studied. One center used cyclosporine (CsA)-based immunosuppression and the other center used tacrolimus. Patients were on CsA (n = 26, group 1) or on tacrolimus (n = 10, group 2). Patients received basiliximab induction, mycophenolate mofetil, and prednisone.

RESULTS

In patients on CsA, 26 kidney biopsies were performed during the 6 months after transplantation. Eighteen protocol biopsies were performed at 3 months post transplant; 13 were normal and five showed rejection (two borderline and three Banff II rejections). Eight biopsies were motivated by an increase of serum creatinine; four were normal and four revealed signs of acute rejection (two borderline and two Banff II). Twelve protocol biopsies were performed after 12 months; all were normal. For patients on tacrolimus (n = 10), ten protocol transplant biopsies were performed at 3 months post-transplant; none showed signs of rejection. No biopsy was performed for an increase of serum creatinine. There were no differences in patient age, number of human leukocyteantigen (HLA) incompatibilities, or other patient characteristics.

CONCLUSIONS

Patients on tacrolimus had less acute rejection episodes detected on protocol biopsies 3 months after transplant. Protocol biopsies seem to play an important role in the detection of subclinical rejection in patients on CsA.

Performance of polymerase chain reaction techniques detecting perforin in the diagnosis of acute renal rejection: a meta-analysis

Background

Studies in the past have shown that perforin expression is up-regulated during acute renal rejection, which provided hopes for a non-invasive and reliable diagnostic method to identify acute rejection. However, a systematic assessment of the value of perforin as a diagnostic marker of acute renal rejection has not been performed. We conducted this meta-analysis to document the diagnostic performance of perforin mRNA detection and to identify potential variables that may affect the performance.

Methodology/Principal Findings

Relevant materials that reported the diagnostic performance of perforin mRNA detection in acute renal rejection patients were extracted from electronic databases. After careful evaluation of the studies included in this analysis, the numbers of true positive, true negative, false positive and false negative cases of acute renal rejection identified by perforin mRNA detection were gathered from each data set. The publication year, sample origin, mRNA quantification method and housekeeping gene were also extracted as potential confounding variables. Fourteen studies with a total of 501 renal transplant subjects were included in this meta-analysis. The overall performance of perforin mRNA detection was: pooled sensitivity, 0.83 (95% confidence interval: 0.78 to 0.88); pooled specificity, 0.86 (95% confidence interval: 0.82 to 0.90); diagnostic odds ratio, 28.79 (95% confidence interval: 16.26 to 50.97); and area under the summary receiver operating characteristic curves value, 0.9107±0.0174. The univariate analysis of potential variables showed some changes in the diagnostic performance, but none of the differences reached statistical significance.

Conclusions/Significance

Despite inter-study variability, the test performance of perforin mRNA detected by polymerase chain reaction was consistent under circumstances of methodological changes and demonstrated both sensitivity and specificity in detecting acute renal rejection. These results suggest a great diagnostic potential for perforin mRNA detection as a reliable marker of acute rejection in renal allograft recipients.

Derivation and validation of a cytokine-based assay to screen for acute rejection in renal transplant recipients

BACKGROUND AND OBJECTIVES

Acute rejection remains a problem in renal transplantation. This study sought to determine the utility of a noninvasive cytokine assay in screening of acute rejection.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

In this observational cross-sectional study, 64 patients from two centers were recruited upon admission for allograft biopsy to investigate acute graft dysfunction. Blood was collected before biopsy and assayed for a panel of 21 cytokines secreted by PBMCs. Patients were classified as acute rejectors or nonrejectors according to a classification rule derived from an initial set of 32 patients (training cohort) and subsequently validated in the remaining patients (validation cohort).

RESULTS

Although six cytokines (IL-1β, IL-6, TNF-α, IL-4, GM-CSF, and monocyte chemoattractant protein-1) distinguished acute rejectors in the training cohort, logistic regression modeling identified a single cytokine, IL-6, as the best predictor. In the validation cohort, IL-6 was consistently the most accurate cytokine (area under the receiver-operating characteristic curve, 0.85; P=0.006), whereas the application of a prespecified cutoff level, as determined from the training cohort, resulted in a sensitivity and specificity of 92% and 63%, respectively. Secondary analyses revealed a strong association between IL-6 levels and acute rejection after multivariate adjustment for clinical characteristics (P<0.001).

CONCLUSIONS

In this pilot study, the measurement of a single cytokine can exclude acute rejection with a sensitivity of 92% in renal transplant recipients presenting with acute graft dysfunction. Prospective studies are needed to determine the utility of this simple assay, particularly for low-risk or remote patients.

Monitoring and managing graft health in the kidney transplant recipient

Ongoing monitoring of kidney transplants is a widely accepted and practiced part of posttransplantation management. One reason to monitor is to evaluate whether the transplant is stable. The transplant community evaluates stability by checking kidney function. Despite problems with sensitivity and specificity, obtaining serial serum creatinine levels is the most common approach to assessing kidney function. Some programs supplement serial serum creatinine levels with surveillance kidney biopsies. Although not uniformly accepted as beneficial, surveillance biopsies are useful in select subsets of patients such as highly sensitized recipients. Recent biopsy studies shed light on which histopathology findings portend poor prognoses. The Long-Term Deterioration of Kidney Allograft Function Study (DeKAF) and similar studies that will prospectively evaluate therapeutic interventions should help the transplant community better define how to monitor and manage the kidney transplant optimally. In the meantime, Kidney Diseases: Improving Global Outcomes (KDIGO) provides an evidence-based approach toward monitoring and managing the kidney transplant.

Monitoring tolerance and rejection in organ transplant recipients

To avoid toxic side effects caused by permanent immunosuppressive treatment, research in transplantation focuses on new treatment strategies inducing tolerance or allowing drug weaning. Implementing drug minimization into clinical routine can be only safely achieved when guided by biomarkers reflecting the individual immune reactivity. We review recently described biomarkers and assays allowing identification of patients suitable for drug weaning or at risk of rejection. However, the majority of described biomarkers and assays have not been validated in prospective clinical trials. Thus, collaborative efforts are needed to design and perform prospective multicenter trials to validate the identified biomarkers across different laboratories.

Protocol biopsy of a transplanted kidney as a tool for monitoring adequacy of immunosuppressive therapy: 10 years of experience from a single transplant center

BACKGROUND

The aims of this prospective study were to determine the prevalence of clinically silent rejection changes and of nephrotoxicity of calcineurin inhibitors among repeated protocol biopsies of transplanted kidneys and to assess their impacts on chronic graft function and damage at the end of 1 year.

METHODS

We performed 424 protocol biopsies among 158 patients over the first year after transplantation. We monitored parameters of graft function and progression of chronic changes among subjects with clinically silent rejection or toxicity for comparison with a control cohort showing normal histological findings. The results of statistical tests were considered to be significant at a level of P < .05.

RESULTS

At 3 weeks, 3 months, and 12 months, there were normal histological findings among 30 (19%), 21 (14.8%), and 14 (11.3%) patients, respectively; subclinical rejection changes occurred in 49 (31%), 36 (25.4%), and 20 (16.2%) grafts, respectively. At the third week, histological signs of toxicity occurred in 33 (20.9%) patients with significant persistence despite reductions in calcineurin inhibitor doses. At the end of 1 year of follow-up, both subclinical and toxic changes produced similar increases in chronic changes as quantified by the Banff score and were significantly different from the control group (P < .05). Serum creatinine concentrations and glomerular filtration rates did not accurately reflect the degree of graft damage in the early posttransplantation period.

CONCLUSIONS

Subclinical rejection and toxic changes among a significant proportion of grafts are associated with progression of chronic changes already over the first year following transplantation. Hence they represent independent risk factors for the development of irreversible graft damage. Protocol biopsy seems to be an important method to monitor immunosuppressive therapy.

MicroRNA profiles in allograft tissues and paired urines associate with chronic allograft dysfunction with IF/TA

Despite the advances in immunosuppression, renal allograft attrition over time remains unabated due to chronic allograft dysfunction (CAD) with interstitial fibrosis (IF) and tubular atrophy (TA). We aimed to evaluate microRNA (miRNA) signatures in CAD with IF/TA and appraise correlation with paired urine samples and potential utility in prospective evaluation of graft function. MiRNA signatures were established between CAD with IF/TA versus normal allografts by microarray. Validation of the microarray results and prospective evaluation of urine samples was performed using real-time quantitative-PCR (RT-qPCR). Fifty-six miRNAs were identified in samples with CAD-IF/TA. Five miRNAs were selected for further validation based on array fold change, p-value and in silico predicted mRNA targets. We confirmed the differential expression of these five miRNAs by RT-qPCR using an independent set of samples. Differential expression was detected for miR-142-3p, miR-204, miR-107 and miR-211 (p < 0.001) and miR-32 (p < 0.05). Furthermore, differential expression of miR-142-3p (p < 0.01), miR-204 (p < 0.01) and miR-211 (p < 0.05) was also observed between patient groups in urine samples. A characteristic miRNA signature for IF/TA that correlates with paired urine samples was identified. These results support the potential use of miRNAs as noninvasive markers of IF/TA and for monitoring graft function.

Identifying biomarkers as diagnostic tools in kidney transplantation

There is a critical need for biomarkers for early diagnosis, treatment response, and surrogate end point and outcome prediction in organ transplantation, leading to a tailored and individualized treatment. Genomic and proteomic platforms have provided multiple promising new biomarkers during the last few years. However, there is still no routine application of any of these markers in clinical transplantation. This article will discuss the existing gap between biomarker discovery and clinical application in the kidney transplant setting. Approaches to implementing biomarker monitoring into clinical practice will also be discussed.

Renal interstitial fibrosis in children treated with FK506 for nephrotic syndrome

BACKGROUND

Steroid-dependent, steroid-resistant or frequently relapsing nephrotic syndrome carries a poor prognosis, including progression to renal failure. There are a number of studies confirming the efficacy of FK506 in steroid-resistant or steroid-dependent nephrotic syndrome. Although the use of this medication is becoming more common, we know very little about the potential nephrotoxicity when used in nephrotic syndrome.

METHOD

We retrospectively reviewed the characteristics and biopsy findings of 11 children with steroid-dependent or frequently relapsing nephrotic syndrome treated with FK506. Two sequential biopsies were evaluated for the change in interstitial fibrosis, measured by a quantitative stereological method, and the change in arteriolar hyaline thickening, tubular atrophy and interstitial fibrosis, graded according to Banff criteria.

RESULTS

There was an increase in interstitial fibrosis (P = 0.005), with a median absolute change in the per cent volume density between initial and follow-up biopsies of 1.8% [interquartile range (IQR) 3.9%]. Median percentage change in volume density of interstitial fibrosis, relative to volume density of interstitial fibrosis prior to initiating FK506, was 93% (IQR 138%). Banff scores for interstitial fibrosis and tubular atrophy also increased following tacrolimus therapy (P = 0.04 for both). Average FK506 trough level over the treatment period was significantly associated with change in fibrosis (Spearman's rho = 0.67 and P = 0.02).

CONCLUSIONS

This is some of the first histological data concerning tacrolimus nephrotoxicity in childhood nephrotic syndrome. Although the role of the natural progression of the underlying disease in the observed change is not definitively clear, the changes seen are in keeping with the known nephrotoxic effects of FK506 demonstrated in renal transplant. This increase is small when presented as a median change. However, there were a number of children who had a larger change in fibrosis. The factors predictive of interstitial fibrosis while on FK506 are not well defined; the findings from this study suggest that FK506 level may be a factor. Given the observations and limitations of the few published studies, there is an obvious need for further study in a large multicenter prospective trial.

Adding value to liver (and allograft) biopsy evaluation using a combination of multiplex quantum dot immunostaining, high-resolution whole-slide digital imaging, and automated image analysis

Various technologies including nucleic acid, protein, and metabolic array analyses of blood, liver tissue, and bile are emerging as powerful tools in the study of hepatic pathophysiology. The entire lexicon of liver disease, however, has been written using classical hematoxylin-eosin staining and light microscopic examination. The authors' goal is to develop new tools to enhance histopathologic examination of liver tissue that would enrich the information gained from liver biopsy analysis, enable quantitative analysis, and bridge the gap between various "-omics" tools and interpretation of routine liver biopsy results. This article describes the progress achieved during the past 2 years in developing multiplex quantum dot (nanoparticle) staining and combining it with high-resolution whole-slide imaging using a slide scanner equipped with filters to capture 9 distinct fluorescent signals for multiple antigens. The authors first focused on precise characterization of leukocyte subsets, but soon realized that the data generated were beyond the practical limits that could be properly evaluated, analyzed, and interpreted visually by a pathologist. Therefore, the authors collaborated with the open source FARSIGHT image analysis project (http://www.farsight-toolkit.org). FARSIGHT's goal is to develop and disseminate the next-generation toolkit of automated image analysis methods to enable quantification of molecular biomarkers on a cell-by-cell basis from multiparameter images. The resulting data can be used for histocytometric studies of the complex and dynamic tissue microenvironments that are of biomedical interest. The authors envisage that these tools will eventually be incorporated into the routine practice of surgical pathology and precipitate a revolution in the specialty.