Quantitation of allograft fibrosis and chronic allograft nephropathy

Image Analysis Pipeline for Renal Allograft Evaluation and Fibrosis Quantification

INTRODUCTION

Digital pathology improves the standardization and reproducibility of kidney biopsy specimen assessment. We developed a pipeline allowing the analysis of many images without requiring human preprocessing and illustrate its use with a simple algorithm for quantification of interstitial fibrosis on a large dataset of kidney allograft biopsy specimens.

METHODS

Masson trichrome-stained images from kidney allograft biopsy specimens were used to train and validate a glomeruli detection algorithm using a VGG19 convolutional neural network and an automatic cortical region of interest (ROI) selection algorithm including cortical regions containing all predicted glomeruli. A positive-pixel count algorithm was used to quantify interstitial fibrosis on the ROIs and the association between automatic fibrosis and pathologist evaluation, estimated glomerular filtration rate (GFR) and allograft survival was assessed.

RESULTS

The glomeruli detection (F1 score of 0.87) and ROIs selection (F1 score 0.83 [SD 0.13]) algorithms displayed high accuracy. The correlation between the automatic fibrosis quantification on manually and automatically selected ROIs was high (r = 1.00 [0.99-1.00]). Automatic fibrosis quantification was only moderately correlated with pathologists' assessment and was not significantly associated with eGFR or allograft survival.

CONCLUSION

This pipeline can automatically and accurately detect glomeruli and select cortical ROIs that can easily be used to develop, validate, and apply image analysis algorithms.

Artificial intelligence and algorithmic computational pathology: an introduction with renal allograft examples

Whole slide imaging, which is an important technique in the field of digital pathology, has recently been the subject of increased interest and avenues for utilisation, and with more widespread whole slide image (WSI) utilisation, there will also be increased interest in and implementation of image analysis (IA) techniques. IA includes artificial intelligence (AI) and targeted or hypothesis-driven algorithms. In the overall pathology field, the number of citations related to these topics has increased in recent years. Renal pathology is one anatomical pathology subspecialty that has utilised WSIs and IA algorithms; it can be argued that renal transplant pathology could be particularly suited for whole slide imaging and IA, as renal transplant pathology is frequently classified by use of the semiquantitative Banff classification of renal allograft pathology. Hypothesis-driven/targeted algorithms have been used in the past for the assessment of a variety of features in the kidney (e.g. interstitial fibrosis, tubular atrophy, inflammation); in recent years, the amount of research has particularly increased in the area of AI/machine learning for the identification of glomeruli, for histological segmentation, and for other applications. Deep learning is the form of machine learning that is most often used for such AI approaches to the 'big data' of pathology WSIs, and deep learning methods such as artificial neural networks (ANNs)/convolutional neural networks (CNNs) are utilised. Unsupervised and supervised AI algorithms can be employed to accomplish image or semantic classification. In this review, AI and other IA algorithms applied to WSIs are discussed, and examples from renal pathology are covered, with an emphasis on renal transplant pathology.

Magnetization Transfer Imaging Is Unaffected by Decreases in Renal Perfusion in Swine

OBJECTIVES

Multiparametric renal magnetic resonance imaging (MRI), including diffusion-weighted imaging, magnetic resonance elastography, and magnetization transfer imaging (MTI), is valuable in the noninvasive assessment of renal fibrosis. However, hemodynamic changes in diseased kidneys may impede their ability to measure renal fibrosis. Because MTI assesses directly tissue content of macromolecules, we test the hypothesis that MTI would be insensitive to renal hemodynamic changes in swine kidneys with acute graded ischemia.

MATERIALS AND METHODS

Seven domestic pigs underwent placement of an inflatable silicone cuff around the right renal artery to induce graded renal ischemia. Multiparametric MRI was performed at baseline, 50%, 75%, and 100% renal artery stenosis as well as reperfusion. Measurements included regional perfusion, R2*, apparent diffusion coefficient (ADC), stiffness, and magnetization transfer ratio (MTR) using arterial spin-labeled MRI, blood oxygenation-dependent MRI, diffusion-weighted imaging, magnetic resonance elastography, and MTI, respectively. Histology was performed to rule out renal fibrosis.

RESULTS

During graded ischemia, decreases in renal perfusion were accompanied with elevated R2*, decreased ADC, and stiffness, whereas no statistically significant changes were observed in the MTR. No fibrosis was detected by histology. After release of the obstruction, renal perfusion showed only partial recovery, associated with return of kidney R2*, ADC, and stiffness to baseline levels, whereas cortical MTR decreased slightly.

CONCLUSIONS

Renal MTI is insensitive to decreases in renal perfusion and may offer reliable assessment of renal structural changes.

Noninvasive assessment of renal fibrosis by magnetic resonance imaging and ultrasound techniques

Renal fibrosis is a useful biomarker for diagnosis and guidance of therapeutic interventions of chronic kidney disease (CKD), a worldwide disease that affects more than 10% of the population and is one of the major causes of death. Currently, tissue biopsy is the gold standard for assessment of renal fibrosis. However, it is invasive, and prone to sampling error and observer variability, and may also result in complications. Recent advances in diagnostic imaging techniques, including magnetic resonance imaging (MRI) and ultrasonography, have shown promise for noninvasive assessment of renal fibrosis. These imaging techniques measure renal fibrosis by evaluating its impacts on the functional, mechanical, and molecular properties of the kidney, such as water mobility by diffusion MRI, tissue hypoxia by blood oxygenation level dependent MRI, renal stiffness by MR and ultrasound elastography, and macromolecule content by magnetization transfer imaging. Other MR techniques, such as T₁/T₂ mapping and susceptibility-weighted imaging have also been explored for measuring renal fibrosis. Promising findings have been reported in both preclinical and clinical studies using these techniques. Nevertheless, limited specificity, sensitivity, and practicality in these techniques may hinder their immediate application in clinical routine. In this review, we will introduce methodologies of these techniques, outline their applications in fibrosis imaging, and discuss their limitations and pitfalls.

Pathologic Study of Supernumerary Orbital Band in Type I Duane Syndrome

Background/Aims

Accessory orbital bands are relatively rare and very few reports detail histopathology. Cases in the literature describe the composition of the bands as muscular and/or fibrous. The composition of the supernumerary band lying deep in the medial rectus muscle in a patient with type I Duane syndrome was investigated.

Methods

Histochemical stains were used in conjunction with polarized light for differentiating compressed collagen from muscle. Immunohistochemistry was used for verification of the presence of muscle.

Results

Compressed collagen appeared red using Masson trichrome staining. Collagen was positively identified by illumination with polarized light on several stains including the underutilized Sirius red dye.

Conclusions

The findings of dense collagen fibers in the fibrotic band with focal striated muscle correlated with the restrictive strabismus. In concert with other cases in the literature, it is proposed that the fibrous bands are generally associated with restrictive strabismus. Bands that are muscular may or may not be associated with strabismus. Special techniques are needed to positively identify compressed collagen.

Phosphocalcic Markers and Calcification Propensity for Assessment of Interstitial Fibrosis and Vascular Lesions in Kidney Allograft Recipients

Renal interstitial fibrosis and arterial lesions predict loss of function in chronic kidney disease. Noninvasive estimation of interstitial fibrosis and vascular lesions is currently not available. The aim of the study was to determine whether phosphocalcic markers are associated with, and can predict, renal chronic histological changes. We included 129 kidney allograft recipients with an available transplant biopsy in a retrospective study. We analyzed the associations and predictive values of phosphocalcic markers and serum calcification propensity (T50) for chronic histological changes (interstitial fibrosis and vascular lesions). PTH, T50 and vitamin D levels were independently associated to interstitial fibrosis. PTH elevation was associated with increasing interstitial fibrosis severity (r = 0.29, p = 0.001), while T50 and vitamin D were protective (r = -0.20, p = 0.025 and r = -0.23, p = 0.009 respectively). On the contrary, fibroblast growth factor 23 (FGF23) and Klotho correlated only modestly with interstitial fibrosis (p = 0.045) whereas calcium and phosphate did not. PTH, vitamin D and T50 were predictors of extensive fibrosis (AUC: 0.73, 0.72 and 0.68 respectively), but did not add to renal function prediction. PTH, FGF23 and T50 were modestly predictive of low fibrosis (AUC: 0.63, 0.63 and 0.61) but did not add to renal function prediction. T50 decreased with increasing arterial lesions (r = -0.21, p = 0.038). The discriminative performance of T50 in predicting significant vascular lesions was modest (AUC 0.61). In summary, we demonstrated that PTH, vitamin D and T50 are associated to interstitial fibrosis and vascular lesions in kidney allograft recipients independently of renal function. Despite these associations, mineral metabolism indices do not show superiority or additive value to fibrosis prediction by eGFR and proteinuria in kidney allograft recipients, except for vascular lesions where T50 could be of relevance.

Defining nephrotic syndrome from an integrative genomics perspective

Nephrotic syndrome (NS) is a clinical condition with a high degree of morbidity and mortality, caused by failure of the glomerular filtration barrier, resulting in massive proteinuria. Our current diagnostic, prognostic and therapeutic decisions in NS are largely based upon clinical or histological patterns such as "focal segmental glomerulosclerosis" or "steroid sensitive". Yet these descriptive classifications lack the precision to explain the physiologic origins and clinical heterogeneity observed in this syndrome. A more precise definition of NS is required to identify mechanisms of disease and capture various clinical trajectories. An integrative genomics approach to NS applies bioinformatics and computational methods to comprehensive experimental, molecular and clinical data for holistic disease definition. A unique aspect is analysis of data together to discover NS-associated molecules, pathways, and networks. Integrating multidimensional datasets from the outset highlights how molecular lesions impact the entire individual. Data sets integrated range from genetic variation to gene expression, to histologic changes, to progression of chronic kidney disease (CKD). This review will introduce the tenets of integrative genomics and suggest how it can increase our understanding of NS from molecular and pathophysiological perspectives. A diverse group of genome-scale experiments are presented that have sought to define molecular signatures of NS. Finally, the Nephrotic Syndrome Study Network (NEPTUNE) will be introduced as an international, prospective cohort study of patients with NS that utilizes an integrated systems genomics approach from the outset. A major NEPTUNE goal is to achieve comprehensive disease definition from a genomics perspective and identify shared molecular drivers of disease.

Autologous bone marrow derived mesenchymal stromal cell therapy in combination with everolimus to preserve renal structure and function in renal transplant recipients

Background

Kidney transplantation has improved survival and quality of life for patients with end-stage renal disease. Despite excellent short-term results due to better and more potent immunosuppressive drugs, long-term survival of transplanted kidneys has not improved accordingly in the last decades. Consequently there is a strong interest in immunosuppressive regimens that maintain efficacy for the prevention of rejection, whilst preserving renal structure and function. In this respect the infusion of mesenchymal stromal cells (MSCs) may be an interesting immune suppressive strategy. MSCs have immune suppressive properties and actively contribute to tissue repair. In experimental animal studies the combination of mammalian target of rapamycin (mTOR) inhibitor and MSCs was shown to attenuate allo immune responses and to promote allograft tolerance. The current study will test the hypothesis that MSC treatment, in combination with the mTOR inhibitor everolimus, facilitates tacrolimus withdrawal, reduces fibrosis and decreases the incidence of opportunistic infections compared to standard tacrolimus dose.

Methods/design

70 renal allograft recipients, 18–75 years old, will be included in this Phase II, open label, randomized, non-blinded, prospective, single centre clinical study. Patients in the MSC treated group will receive two doses of autologous bone marrow derived MSCs IV (target 1,5x10⁶, Range 1-2x10⁶ million MSCs per/kg body weight), 7 days apart, 6 and 7 weeks transplantation in combination with everolimus and prednisolone. At the time of the second MSC infusion tacrolimus will be reduced to 50% and completely withdrawn 1 week later. Patients in the control group will receive everolimus, prednisolone and standard dose tacrolimus. The primary end point is to compare fibrosis by quantitative Sirius Red scoring of MSC treated and untreated groups at 6 months compared to 4 weeks post-transplant. Secondary end points include: composite end point efficacy failure (Biopsy Proven Acute Rejection, graft loss or death); renal function and proteinuria; opportunistic infections; immune monitoring and “subclinical” cardiovascular disease groups by assessing echocardiography in the different treatment groups.

Discussion

This study will provide information whether MSCs in combination with everolimus can be used for tacrolimus withdrawal, and whether this strategy leads to preservation of renal structure and function in renal recipients.

Trial registration

NCT02057965.

What is the best way to measure renal fibrosis?: A pathologist's perspective

Interstitial fibrosis is a hallmark structural correlate of progressive and chronic kidney disease. There remain many uncertainties about how to best measure interstitial fibrosis both in research settings and in evaluations of renal biopsies performed for management of individual patients. Areas of uncertainty include determination of the composition of the matrix in a fibrotic parenchyma, the definition of how the interstitium is involved by fibrosing injuries, the choice of histologic stains for evaluation of renal fibrosis, and the reproducibility and robustness of measures currently employed by pathologists, both with and without the assistance of computerized imaging and assessments. In this review, we address some of these issues while citing the key studies that illustrate these difficulties. We point to future approaches that may allow a more accurate and meaningful assessment of renal interstitial fibrosis.

Banff fibrosis study: multicenter visual assessment and computerized analysis of interstitial fibrosis in kidney biopsies

Increasing interstitial fibrosis (IF) in native and kidney transplant biopsies is associated with functional decline and serves as a clinical trial end point. A Banff 2009 Conference survey revealed a range in IF assessment practices. Observers from multiple centers were asked to assess 30 renal biopsies with a range of IF and quantitate IF using two approaches on trichrome, Periodic acid-Schiff (PAS) and computer-assisted quantification of collagen III immunohistochemistry (C-IHC) slides, as well as assessing percent of cortical tubular atrophy% (TA%) and Banff total cortical inflammation score (ti-score). C-IHC using whole slide scans was performed. C-IHC assessment showed a higher correlation with organ function (r = -0.48) than did visual assessments (r = -0.32--0.42); computerized and visual C-IHC assessment also correlated (r = 0.64-0.66). Visual assessment of trichrome and C-IHC showed better correlations with organ function and C-IHC, than PAS, TA% and ti-score. However, visual assessment of IF, independent of approach, was variable among observers, and differences in correlations with organ function were not statistically significant among C-IHC image analysis and visual assessment methods. C-IHC image analysis correlated among three centers (r > 0.90, p < 0.0001, between all centers). Given the difficulty of visual IF assessment standardization, C-IHC image could potentially accomplish standardized IF assessment in multicenter settings.

Short-term prognosis of living-donor kidney transplantation from hypertensive donors with high-normal albuminuria

BACKGROUND

High-normal albuminuria (HNA) is an independent predictor of cardiovascular risk in the general population. Although hypertensive donor (HTD) candidates with HNA were considered acceptable donors by the Amsterdam Forum 2004, the transplant prognosis of HTDs with HNA has not been determined. Therefore, we investigated the transplant prognosis of HTDs with HNA.

METHODS

We retrospectively analyzed 52 adult living-donor kidney transplants performed at Kagawa University Hospital. HNA was defined as albuminuria of 15 to 30 mg/g Cr. Changes in kidney function of donors and recipients were assessed up to 2 years after transplantation.

RESULTS

Overall, 38 donors were normotensive and 14 were hypertensive. Nine of 14 HTDs exhibited HNA before donation. More HTDs with HNA had arteriosclerotic vasculopathy or glomerulosclerosis than did normotensive donors (NTDs). Hypertension and the degree of albuminuria did not affect the donors' posttransplantation kidney function. The risk of discompensatory changes in kidney function after donation was significantly higher in HTDs with HNA than in NTDs (odds ratio, 10.5; 95% confidence interval, 1.51-72.9; P=0.02). In multivariate analysis, the coexistence of hypertension and HNA was not significantly associated with discompensatory changes after donation (adjusted odds ratio, 6.04; 95% confidence interval, 0.19-192; P=0.31). Recipients of HTDs with HNA had similar allograft survival rates but lower allograft function compared with recipients of NTDs.

CONCLUSIONS

Although further studies are needed to confirm our results, the short-term prognosis of living-donor kidney transplantation was similar between HTDs with HNA and NTDs.

Renal interstitial fibrosis: mechanisms and evaluation

PURPOSE OF REVIEW

Tubulointerstitial injury in the kidney is complex, involving a number of independent and overlapping cellular and molecular pathways, with renal interstitial fibrosis and tubular atrophy (IFTA) as the final common pathway. Furthermore, there are multiple ways to assess IFTA.

RECENT FINDINGS

Cells involved include tubular epithelial cells, fibroblasts, fibrocytes, myofibroblasts, monocyte/macrophages, and mast cells with complex and still incompletely characterized cell-molecular interactions. Molecular mediators involved are numerous and involve pathways such as transforming growth factor (TGF)-β, bone morphogenic protein (BMP), platelet-derived growth factor (PDGF), and hepatocyte growth factor (HGF). Recent genomic approaches have shed insight into some of these cellular and molecular pathways. Pathologic evaluation of IFTA is central in assessing the severity of chronic disease; however, there are a variety of methods used to assess IFTA. Most assessment of IFTA relies on pathologist assessment of special stains such as trichrome, Sirius Red, and collagen III immunohistochemistry. Visual pathologist assessment can be prone to intra and interobserver variability, but some methods employ computerized morphometery, without a clear consensus as to the best method.

SUMMARY

IFTA results from on orchestration of cell types and molecular pathways. Opinions vary on the optimal qualitative and quantitative assessment of IFTA.

Morphometric and visual evaluation of fibrosis in renal biopsies

Interstitial fibrosis is an outcome measure of increasing importance in clinical trials of both renal transplantation and native disease, but data on the comparative advantages of fibrosis measurement methods are limited. We compared four morphometric techniques and contrasted these with two visual fibrosis-scoring methods on trichrome-stained slides. Two morphometric methods included whole-slide digital images: collagen III immunohistochemistry and a new technique using trichrome and periodic acid-Schiff subtraction morphometry; the other two methods included Sirius Red with and without polarization on multiple digital fields. We evaluated 10 serial sections from 15 renal biopsies with a range of fibrosis extent and diagnoses on duplicate sections with each method on separate days. Three pathologists performed visual scoring on whole-slide images. Visual and morphometric techniques had good to excellent interassay reproducibility (R(2) = 0.62 to 0.96) and interobserver reproducibility (R(2) = 0.75 to 0.99, all P < 0.001). Morphometry showed less variation between observers than visual assessment (mean of 1% to 5% versus 11% to 13%). Collagen III, Sirius Red unpolarized, and visual scores had the strongest correlations (R(2) = 0.78 to 0.89), the greatest dynamic range, and the best correlation with estimated GFR (R(2) = 0.38 to 0.50, P < 0.01 to 0.001). Considering efficiency, reproducibility, and functional correlation, two current techniques stand out as potentially the best for clinical trials: collagen III morphometry and visual assessment of trichrome-stained slides.

Enhanced resolution of interstitial fibrosis in pediatric renal allograft biopsies using image analysis of trichrome stain

The Banff classification is ill suited to detect subtle histologic progression in renal allografts. We present image analysis methodology to precisely quantify IF in pediatric renal allograft biopsies routinely stained with MT. The mean area %IF was determined in 105 pediatric renal allograft biopsies. Associations between %IF or Banff ci scores and estimated GFR were determined using GEE modeling. Logistic regression was used to estimate IF progression. Percent IF (mean ± s.d.) was 6.83% ± 3.94, 10.39 ± 5.23%, and 20.53 ± 8.74 in patients with ci0, ci1, and ci2, respectively. The difference in %IF between biopsies with ci0, ci1, and ci2 was not proportionately incremental: compared to ci2, ci0 had 67% less IF (p < 0.0001), while ci1 had 48% less IF (p < 0.0001). AR had no impact on the precision of %IF measurements. Each 0.5% decrement in %IF was associated with a 1 mL/min per 1.73 m² increase in GFR (p < 0.004). Histologic progression was demonstrated by increasing %IF values (p < 0.0001) and could be estimated by IF = 2.61 × (months) + 6.43. This readily adaptable methodology may be used for the longitudinal assessment of IF in pediatric protocol renal allograft biopsies.

Collagenofibrotic glomerulopathy: three case reports in Brazil

Background

We are reporting the first Collagenofibrotic Glomerulopathy (CG) in South America. So, this collagen type III glomerulopathy is not limited to Japan but may be found throughout the world.

Case Reports

We describe three patients that presented some factors in common, such as sex, age and the presence of non-nephrotic proteinuria associated with microscopic hematuria. The findings with the immunofluorescence microscopy, of immunoglobulins, and components of the complement were usually negative. The picrosyrius staining showed the presence of reddish material in the mesangium, when it was seen under standard microscopy; however, when it was seen with birefringence, it became greenish under polarized light, showed the collagen found in this area of the glomerulus. The identification of CG was made through electronic microscopic scanning, and curved and disorganized fibers were found.

Conclusion

These cases are the first from South America to be reported, and they are about an idiopathic renal disease that is not related to any specific races or locations. The reports contribute to a better understanding of this disease, which although not so prevalent, should be considered as an importantly differential diagnostic of cases of proteinuria.

High urinary excretion of kidney injury molecule-1 is an independent predictor of graft loss in renal transplant recipients

BACKGROUND

Chronic transplant dysfunction is characterized by renal function decline and proteinuria. Kidney injury molecule (KIM)-1, a transmembrane tubular protein with unknown function, is undetectable in normal kidneys, but markedly induced after injury. Urinary KIM-1 excretion has been quantified as biomarker of renal damage. We prospectively studied whether urinary KIM-1 predicts graft loss, independent of renal function and proteinuria.

METHODS

Renal transplant recipients (n=145) visiting our outpatient clinic between August 2001 and July 2003 collected 24-hour urine samples for assessment of baseline urinary KIM-1 excretion (microsphere-based Luminex technology), and were followed for graft loss.

RESULTS

Recipients participated at a median (interquartile range) of 6.0 (2.5-12.0) years posttransplant in baseline measurements. Follow-up beyond baseline was 4.0 (3.2-4.5) years. Urinary KIM-1 excretion was 0.72 (0.42-1.37) ng per 24 hours. Occurrence of graft loss increased over tertiles of KIM-1 excretion: 3 (6.3%), 11 (22.4%), and 17 cases (35.4%; P=0.001), respectively. High KIM-1 excretion was associated with proteinuria, low creatinine clearance, and high donor age (all P<0.01). In multivariate Cox regression analyses, prediction of graft loss by KIM-1 appeared independent of creatinine clearance, proteinuria, and donor age. Hazard ratios (95% CI) for the second and third tertile of KIM-1 excretion were 3.6 (0.9-13.5) and 5.1 (1.5-17.8) in the final model.

CONCLUSIONS

Urinary excretion of KIM-1 is an independent predictor of long-term graft loss and therefore a promising new biomarker in early prediction of graft loss.

Safety and efficacy of steroid withdrawal two days after kidney transplantation: analysis of results at three years

BACKGROUND

Chronic steroid therapy in spite of myriad side effects is widely used in kidney transplantation. This prospective controlled study evaluated safety and efficacy of steroid withdrawal at 2 days in kidney recipients monitored by surveillance biopsy.

METHODS

In all, 300 kidney recipients were studied; 150 in second-day steroid withdrawal group and 150 in steroid treated group (control group). Immunosuppression was basiliximab induction and maintenance was a calcineurin inhibitor and mycophenolate mofetil or sirolimus. Biopsy-proven acute rejection (BPAR) was treated by methylpredisolone. Surveillance biopsies were completed to evaluate subclinical acute rejection (SCAR) and chronic allograft nephropathy (CAN). Primary end point was acute rejection. Three-year patient and graft survival, new onset diabetes mellitus (NODM), serum creatinine and creatinine clearance were evaluated.

RESULTS

Acute rejection was diagnosed in 14% in control group and 16% in steroid withdrawal group. Three-year patient and graft survival was 89% and 79% in control and 91% and 78% in steroid withdrawal group. Serum creatinine and creatinine clearance was 1.9+/-0.8 and 59+/-11 in control group and 1.8+/-0.9 mg/dl and 61+/-10 mls/minute in steroid withdrawal group. Incidence of SCAR and progression of CAN were comparable in the 2 groups. At 3-years NODM was diagnosed in 21% in control group and 4% in steroid withdrawal group (P<0.01).

CONCLUSIONS

Two-day steroid withdrawal in kidney transplant recipients did not affect BPAR, SCAR, CAN, graft function and patient and graft survival compared to control group up to 3 years. NODM was significantly less in steroid withdrawal group. Two-day steroid withdrawal is safe and beneficial in kidney transplant recipients.

No difference in degree of interstitial Sirius red-stained area in serial biopsies from area under concentration-over-time curves-guided cyclosporine versus tacrolimus-treated renal transplant recipients at one year

Interstitial fibrosis is the main characteristic of chronic allograft nephropathy and long-term graft failure. Cyclosporin (CsA) is thought to be more fibrogenic than tacrolimus. In a prospective, randomized, multicenter trial using a calcineurin-sparing regimen, renal interstitial volume was compared in CsA- and tacrolimus-treated renal transplant recipients by image analysis of Sirius red (SR)-stained cortical areas in protocol biopsies obtained at 6 mo (n = 94) and 12 mo (n = 97) after transplantation. Immunosuppression consisted of CsA or tacrolimus, CD25 mAb, mycophenolate mofetil, and prednisolone. CsA therapy increased the 6-mo risk for subclinical rejection. The prevalence of subclinical rejection was 38.8% in the CsA-treated and 15.2% in the tacrolimus-treated patient group (P = 0.012). Strikingly, no difference in the degree of interstitial SR-stained area was detectable between the two treatment groups. In particular, previous subclinical rejection episodes did not influence the degree of interstitial volume. Also, no difference in GFR occurred at 1 yr, when the mean GFR mounted 63 ml/min. No significant differences in the degree of interstitial SR-stained area could be observed at 6 and 12 mo between CsA- and tacrolimus-treated renal transplant recipients. Although CsA-treated patients developed significantly more subclinical rejections at 6 mo, this did not influence the degree of SR staining or the change in renal function at 1 yr.

Comparison of Steroid Avoidance in Tacrolimus/Mycophenolate Mofetil and Tacrolimus/Sirolimus Combination in Kidney Transplantation Monitored by Surveillance Biopsy

BACKGROUND

Chronic steroid therapy in kidney transplantation has myriad side effects and steroid avoidance has become feasible. This prospective study compared the safety and efficacy of steroid avoidance in tacrolimus (TAC)/mycophenolate mofetil (MMF) and TAC/sirolimus (SRL) combinations in kidney transplantation.

METHODS

In all, 150 kidney recipients were analyzed: 75 each in TAC/MMF and TAC/SRL groups. The primary endpoint was acute rejection. Surveillance biopsies were completed to analyze subclinical acute rejection (SCAR) and chronic allograft nephropathy (CAN). Acute rejection and SCAR were treated by methylprednisolone. Two-year patient and graft survival, renal function, and adverse effects were monitored.

RESULTS

Acute rejection was seen in 12% of TAC/MMF and 8% of TAC/SRL patients. Two-year actuarial patient survival was 95% and 97%, and graft survival 90% and 90% in TAC/MMF and TAC/SRL groups, respectively. Surveillance biopsy showed cumulative incidence of SCAR was 27 % in TAC/MMF and 16 % in TAC/SRL groups at 2 years (P = 0.04). Overall, 33% of recipients in TAC/MMF and 20% in TAC/SRL received methylprednisolone for acute rejection/SCAR. Moderate/severe CAN was 10% in TAC/SRL group and 22% in TAC/MMF group(P = 0.06). New-onset diabetes mellitus (NODM) was 4% each in both groups. All recipients remain free of maintenance steroid therapy.

CONCLUSIONS

Steroid avoidance in tacrolimus-based immunosuppression with MMF or SRL provides equivalent 2-year patient and graft survival with a low incidence of acute rejection and NODM. SCAR and CAN are lower in TAC/SRL compared to TAC/MMF group. The impact of decreased SCAR and CAN in TAC/SRL group on longer-term graft survival and function is to be evaluated.

Avoidance of chronic steroid therapy in african american kidney transplant recipients monitored by surveillance biopsy: 1-year results

African American (AA) kidney recipients receive chronic steroid therapy to improve outcomes, despite their high susceptibility to side effects, particularly diabetes and hypertension. This study evaluated the safety and efficacy of avoidance of chronic steroid therapy in AA compared to non-AA kidney recipients. Two hundred and six kidney recipients were studied; 103 AA recipients versus 103 non-AA recipients. Induction was basiliximab and maintenance was a calcineurin inhibitor plus mycophenolate mofetil or sirolimus. Surveillance biopsies were preformed at 1, 6 and 12 months to assess subclinical acute rejection (SCAR) and chronic allograft nephropathy (CAN). Biopsy-proven acute rejection (AR) and SCAR were treated by methylprednisolone. The primary end point was AR. Secondary end points were graft function, 1-year patient and graft survival. AR was observed in 16% of AA and 13% of non-AA recipients. SCAR at 1 month was significantly higher in the AA group (p=0.04). One-year actual patient and graft survival in the AA group was 96% and 88% and in the non-AA group 97% and 89%, respectively. Avoidance of chronic steroid therapy directed by surveillance biopsies provides equivalent AR, CAN and 1-year patient and graft survival in AA versus non-AA recipients and a 5% incidence of new onset diabetes mellitus. All recipients remain free of chronic steroid therapy. Longer-term follow-up is ongoing.

Estimation of damaged tubular epithelium in renal allografts by determination of vimentin expression

BACKGROUND

Various invasive and non-invasive methods have been investigated for their prognostic value in predicting the outcome of renal allografts. In the present study, vimentin expression in tubular epithelial cells (TEC) was determined by the immunohistochemical examination of biopsy specimens and the prognostic value of this method was assessed.

METHODS

Ninety-two renal transplant recipients were recruited for the present study. Protocol biopsy of the renal graft was performed 1, 3 and 5 years after transplantation in each case. All biopsy specimens were treated with conventional stains and immunostained with an antivimentin antibody. The correlation between vimentin expression and glomerular filtration rate (GFR) and the association between vimentin expression and histopathological findings were determined.

RESULTS

Vimentin was localized in TEC adjacent to interstitial lesions with lymphocyte infiltration and also in TEC with tubulitis or in atrophic tubules. Vimentin positivity significantly correlated with GFR and both vimentin positivity and GFR were significantly associated with the extent of chronic allograft nephropathy, but not with acute rejection. Additionally, vimentin expression and GFR 3 and 5 years after transplantation were higher in cases where graft loss occurred between 5 and 7 years after transplantation compared with graft survival cases.

CONCLUSIONS

These results suggest that immunohistochemistry using antivimentin antibodies on protocol biopsy specimens is useful for the detection of injured TEC and as a predictor of allograft outcome.

Comparison of renal allograft fibrosis after transplantation from heart-beating and non-heart-beating donors

Background

Renal transplants from non-heart-beating donors (NHBDs) yield acceptable function and allograft survival rates in the medium term. However, the long-term results are less certain and there is a paucity of information relating to the development of chronic allograft nephropathy. The aim of this study was to compare allograft fibrosis in kidneys transplanted from NHBDs and conventional heart-beating donors (HBDs).

Methods

A series of 37 NHBD and 75 HBD renal transplants were studied. Protocol renal transplant biopsies were performed at 6 and 12 months after transplantation. Biopsy sections were stained with Sirius red to demonstrate interstitial extracellular matrix. Renal allograft fibrosis was quantified using a computerized image analysis system.

Results

The mean first warm ischaemia time for kidneys from NHBDs was 24 min. A significant delay in graft function occurred in eight of 75 recipients in the HBD group and 31 of 37 in the NHBD group (P &lt; 0·001). There were no significant differences in the level of allograft fibrosis between the two groups at any time point.

Conclusion

Despite high rates of delayed graft function secondary to a prolonged warm ischaemia time, NHBD kidneys do not appear to be more susceptible to the development of renal allograft fibrosis. This study supports the growing body of evidence that kidneys from NHBDs are an acceptable alternative to those from HBDs.

Delta analysis of posttransplantation tubulointerstitial damage

BACKGROUND

Chronic interstitial fibrosis (CIF) is an adverse prognostic feature of chronic allograft nephropathy.

METHODS

We evaluated the evolution, onset, potential causes, and outcomes of tubulointerstitial damage using 959 protocol kidney biopsy specimens obtained regularly until 10 years after transplantation. Specimens were scored by the Banff schema and analyzed for time-specific change or "delta damage" from sequential biopsy-pairs (n=839).

RESULTS

Substantial CIF occurred within 1 year after transplantation, comprising 67.6% of the total burden accumulated during the study period. The maximal intensity of CIF formation occurred within the first 3 months, as a result of acute tubular necrosis and acute and subclinical rejection (all P<0.05), where fibrosis rates exceeded loss from tubular atrophy. By 1 year, diminished CIF formation was accompanied by declining low-level subclinical inflammation (P<0.001) and increasingly prevalent calcineurin inhibitor nephrotoxicity (P<0.01). Banff CIF correlated with tubular atrophy (r=0.82, P<0.001), with tubulointerstitial damage showing a cumulative and irreversible pattern. Mononuclear cell infiltration within areas of tubulointerstitial damage correlated with CIF (r=0.49, P<0.001), tubular atrophy (r=0.43, P<0.001), and Banff i scores (r=0.34, P<0.001) and, most importantly, heralded histologic progression (P<0.001). CIF formation preceded and correlated with glomerulosclerosis (r=0.40, P<0.001), although isotopic glomerular filtration rates underestimated the severity of tubular damage. Cyclosporine (vs. tacrolimus, P<0.001) increased delta CIF, and mycophenolate was protective (vs. azathioprine, P<0.001), independent of their immunosuppressive and nephrotoxic properties when assessed by multivariate analysis of biopsy-pairs (n=849).

CONCLUSION

CIF was a result of early ischemia-reperfusion injury, acute, subacute or persistent interstitial inflammation occurring in a time-dependent manner and was considerably modified by immunosuppressive therapy.

Correlation of quantitative digital image analysis with the glomerular filtration rate in chronic allograft nephropathy

Chronic allograft nephropathy (CAN) is characterized by progressive renal functional loss and histologic abnormalities of one or more tissue compartments. In this study, correlations between histologic abnormalities and graft function [glomerular filtration rate (GFR, measured by iothalamate clearance), serum creatinine (SCr) and urinary protein (UPr)] were investigated using biopsies from 49 patients with newly diagnosed CAN. Extent of tubulointerstitial fibrosis (%TIF), as assessed by a semi-quantitative score, correlated significantly with GFR, SCr and UPr. The close correlation between %TIF and GFR suggested that quantitative measurement of %TIF may predict functional consequences of CAN. Calculation of %TIF by computerized digital analysis was performed using four strategies: (a) quantitation of blue material in Masson's trichrome (MT)-stained sections, (b) quantitation of red material in Sirius Red-stained sections (SR-nonpolarized), (c) quantitation of birefringent material in Sirius Red stained-sections examined under polarized light (SR-polarized) and (d) quantification of brown material in sections stained by immunoperoxidase for alpha-smooth muscle actin. Only the SR-nonpolarized score correlated significantly with GFR at the time of biopsy-diagnosis of CAN. We conclude that digital analysis strategies demonstrate variable accuracy in quantifying %TIF. Validation of the SR-nonpolarized strategy against histologic scoring and GFR supports the application of this technique to longitudinal studies of CAN.

Current status of kidney transplant: update 2003

Pediatric transplantation has seen remarkable advances over the past two decades with reduced morbidity and mortality, reduced rejection rates, and improved long-term patient and allograft survival. Infants currently have short-term patient and allograft survival rates better than any other age group; short-term allograft survival rates in CD recipients are equal to those in LD recipients. With decreased rejection, long-term allograft survival is improving dramatically. Transplantation allows for much reduced risks and improved metabolic status, growth and development, and more normal social interactions. The future of transplantation continues to be exciting, with opportunities for reduced immunosuppressive medications and their side effects, and the elusive goal of transplantation tolerance seems within reach.

The impact of cyclosporine dose reduction with or without the addition of rapamycin on functional, molecular, and histological markers of chronic allograft nephropathy

BACKGROUND

Overexposure to cyclosporine is a risk factor for chronic allograft nephropathy (CAN) and dose reduction has been advocated. The purpose of this study was to determine the impact of adding the non-nephrotoxic immunosuppressant, rapamycin, after cyclosporine dose reduction in renal-allograft recipients with CAN.

METHODS

Thirty-one patients with biopsy-confirmed CAN were prospectively randomized to receive a 40% cyclosporine dose reduction with (rapamycin, n=16) or without (control, n=15) the addition of rapamycin 2 mg/day. Renal function and side-effect parameters were assessed. Patients had renal allograft biopsies taken at recruitment and after 6 months. Glomeruli were isolated from these and underwent total mRNA extraction followed by RT-PCR-ELISA to assess transforming growth factor-beta1, collagen III, TIMP-1, TIMP-2, and matrix metalloproteinase-2 expression. Samples were also stained with Sirius red and the percentage interstitial volume fraction quantified by computerized histomorphometric analysis. Data are presented as mean (+/-SD).

RESULTS

Patient characteristics and cyclosporine trough levels after dose reduction (rapamycin 68 [+/-21] vs. control 56 [+/-19] ng/mL, P=NS) were similar in both groups. Rapamycin patients had a significant fall in Cr-51 radioisotope glomerular filtration rate (31.6 [+/-8.9] to 27.3 [+/-8.6] mL/min, P<0.01) that was not significant in controls (29.5 [+/-10.4] to 27.0 [+/-8.0] mL/min, P=NS). Transforming growth factor-beta1 expression fell over time in control but remained constant in rapamycin patients. Conversely collagen III expression increased over the 6-month follow-up in rapamycin patients but not in controls. Both had comparable increases in TIMP-1 and matrix metalloproteinase-2 but only rapamycin patients developed a significant increase in TIMP-2. Sirius red-stained interstitial volume fraction fell over the study in controls (15.3-11.2%, P=0.06) but not in rapamycin patients (16.2-16.3%, P=NS).

CONCLUSION

Rapamycin (2 mg/day) did not improve functional, molecular, or histological outcome in patients with CAN after cyclosporine dose reduction. Further studies involving larger numbers of patients are necessary to confirm these findings.

Effects of the combination of rapamycin with tacrolimus or cyclosporin on experimental intimal hyperplasia

BACKGROUND

Allograft vasculopathy remains the leading cause of late allograft failure following transplantation and can be inhibited by the antiproliferative drug rapamycin. This study assessed the efficacy of combining rapamycin therapy with calcineurin inhibition.

METHODS

Male Sprague-Dawley rats received rapamycin 0.05 mg/kg daily and either tacrolimus 0.1 mg/kg or cyclosporin 5 mg/kg daily, and findings were compared with those in an untreated control group. Animals underwent left common carotid artery balloon angioplasty; the artery was explanted after 2 weeks. Morphometric analysis was performed on transverse sections and the intima : media ratio was calculated. Profibrotic gene expression was measured with competitive reverse transcriptase-polymerase chain reaction at 14 and 28 days. Proliferation was determined with proliferating cell nuclear antigen at 14 and 28 days. Extracellular matrix deposition was quantified with Sirius red.

RESULTS

The combination of rapamycin and tacrolimus was associated with the greatest reduction in intimal thickening. Furthermore, treatment with rapamycin and tacrolimus significantly attenuated extracellular matrix deposition compared with rapamycin and cyclosporin (P < 0.02).

CONCLUSION

The effects of rapamycin in combination with tacrolimus were better than those observed with rapamycin and cyclosporin.

Microemulsion cyclosporin inhibits vascular remodelling and attenuates associated changes in profibrotic gene expression in an experimental model of allograft vasculopathy

BACKGROUND

Chronic allograft dysfunction (CAD), the leading cause of solid organ transplant failure, is characterized by histological evidence of extracellular matrix (ECM) accumulation (fibrosis). The aim of this study was to characterize the changes in fibrosis-associated gene expression in an experimental model of CAD and to measure the effect of the immunosuppressant cyclosporin on these changes.

METHODS

Lewis recipients of F344 rat thoracic to abdominal transplants were administered cyclosporin or no treatment. Vascular remodelling and ECM accumulation (picrosirius red) were measured using computerized histomorphometry. Fibrosis-associated gene expression was studied by semiquantitative reverse transcription-polymerase chain reaction.

RESULTS

Cyclosporin inhibited medial ECM accumulation and vascular remodelling in allografts. This was associated with an attenuation of the graft inflammatory infiltrate and a reduction in intragraft matrix metalloproteinase (MMP) 2 and MMP-9 messenger RNA (mRNA) levels. There was a significant negative correlation between neoadventitial ECM density and MMP-9 expression, as well as with vessel circumference. Neoadventitial ECM density was significantly higher in the cyclosporin-treated group than in animals with untreated allografts, as were mRNA levels of collagen 3 and tissue inhibitor of metalloproteinase 1.

CONCLUSION

The alloimmune injury itself may contribute directly to vascular remodelling and fibrosis in allograft vasculopathy. Cyclosporin attenuated this component of the pathophysiology of CAD effectively.

Early clinical experience with a novel rapamycin derivative

SDZ RAD (everolimus, Certican is a novel macrolide immunosuppressant that blocks growth factor-driven transduction signals in the T-cell response to alloantigen. After stimulation of the IL-2 receptor on the activated T-cell, SDZ RAD inhibits p70S6 kinase, acting at a later stage in the T-cell mediated response than do cyclosporine and other calcineurin inhibitors (CNIs). Unlike the CNIs, SDZ RAD is a proliferation signal inhibitor, blocking growth factor-driven proliferation of both hematopoietic and nonhematopoietic cells. These activities are complementary to those of cyclosporine and provide a rationale for the addition of SDZ RAD to cyclosporine-based immunosuppression, with the potential for minimizing CNI nephrotoxicity, reducing the incidence of acute rejection, and favoring long-term graft survival. Potential also exists for beneficial effects on other factors that may influence the development of chronic rejection. These factors include comorbid diseases such as hypertension, which may affect transplant vasculopathy, and opportunistic infection with cytomegalovirus (CMV) and other viruses, which may increase the risk of chronic rejection. The synergistic effect of SDZ RAD and cyclosporine has been confirmed in preclinical models, with graft survival being significantly prolonged in rat models of kidney and heart allotransplantation. Clinical experience with SDZ RAD in cyclosporine-based immunosuppression, including low-dose cyclosporine regimens, has also resulted in predictable and favorable clinical outcomes. Low rates of acute rejection, excellent rates of patient and graft survival, lower incidence of CMV infections, better cholesterol, triglyceride and creatinine profiles, and better renal function have been demonstrated with SDZ RAD and lower doses of cyclosporine (Neoral; Novartis) in recipients of renal transplants. These findings, combined with good tolerability rates and an acceptable side-effect profile, indicate that the synergistic profile of SDZ RAD in combination with nontoxic dosages of CNI's and IL2 inhibitors will further improve longterm results in renal transplantation.

Reliability of chronic allograft nephropathy diagnosis in sequential protocol biopsies

BACKGROUND

Chronic allograft nephropathy (CAN) progresses rapidly during the first few months and slowly thereafter. Although the presence of CAN in protocol renal biopsies is a predictor of outcome, the reliability of this diagnosis according to Banff criteria has not been characterized.

METHODS

Renal lesions were evaluated according to the Banff criteria in sequential protocol biopsies performed at 4 and 14 months in 310 biopsies obtained from 155 patients.

RESULTS

CAN progressed from 40 to 53% (P=0.001) while serum creatinine remained stable (146 +/- 44 vs. 147 +/- 48 micromol/L, P=NS). Graft survival in patients with and without CAN in the first biopsy was 74 versus 91% (P < 0.05), and in the second biopsy 75 versus 94% (P < 0.05). In 54 patients (35%) no CAN was present in both biopsies, 39 (25%) showed progression to CAN, 19 (12%) showed regression of CAN, and 43 (28%) showed CAN in both biopsies. Graft survival was: 100%, 81.6%, 82.6% and 69.4%, respectively (P < 0.01). Assuming that CAN does not regress and sampling error is normally distributed, we estimated that 25% of biopsies cannot be properly classified.

CONCLUSIONS

The increase in the incidence of CAN between the 4th and 14th month is lower than the proportion of misclassified biopsies. Thus, monitoring the progression of CAN by means of two sequential biopsies at 4 and 14 months is inaccurate. We suggest that progression of scarring be monitored by means of a donor and a protocol biopsy performed during the first year evaluated with a quantitative approach.