Tacrolimus Exposure and Evolution of Renal Allograft Histology in the First Year After Transplantation

Tacrolimus has a narrow therapeutic window and is characterized by a large inter-individual variability in bioavailability. The impact of tacrolimus exposure on subclinical evolution of graft histology has not been studied in renal recipients. This analysis included 239 protocol biopsies (obtained at implantation, 3 and 12 months) of 120 consecutive kidney recipients treated with tacrolimus, mycophenolate mofetil (MMF) and corticosteroids. Biopsies were scored according to the Banff 2001 criteria and a chronicity score was calculated. Prospective pharmacokinetic data were included in the analysis (5544 tacrolimus predose blood concentrations and tacrolimus AUC(0-12) at 3 and 12 months). Higher donor age and higher number of human leukocyte antigen-DR (HLA-DR) mismatches were independent predictors of subclinical acute rejection at 3 months, present in 8.7% of patients. The number of HLA-DR mismatches was independently associated with biopsy-proven clinical acute rejection. Biopsy-proven acute rejection episodes and low mean tacrolimus exposure were independently associated with higher increase in chronicity scores between 3 and 12 months after transplantation. This observational study suggests that rejection phenomena and immune-mediated mechanisms remain important in the early progression of chronic allograft pathology. Tacrolimus doses or systemic exposure were not associated with lesions of calcineurin inhibitor nephrotoxicity, suggesting that other factors determine susceptibility to tacrolimus nephrotoxicity.     

Acute Oxalate Nephropathy Causing Late Renal Transplant Dysfunction Due to Enteric Hyperoxaluria

Calcium oxalate (CaOx) deposition in the renal allograft is an under recognized and important cause of acute tubular injury and early allograft dysfunction.
We present a case of late transplant dysfunction due to acute oxalate nephropathy. The patient presented with diarrhea and deteriorating graft function, and a diagnosis of enteric hyperoxaluria secondary to pancreatic insufficiency was made. This had occurred, as the patient had been noncompliant with his pancreatic enzyme replacement therapy. Treatment to reduce his circulating oxalate load was initiated, including twice-daily hemodialysis, low fat and oxalate diet and appropriate administration of pancreatic enzyme supplements. Graft function subsequently recovered.
The possibility of fat malabsorption leading to enteric hyperoxaluria should be considered in renal graft recipients presenting with loose stools and graft dysfunction.     

The Utility of 1- and 3-Month Protocol Biopsies on Renal Allograft Function: A Randomized Controlled Study

Identification of pathological events in the renal allograft using protocol biopsies at predetermined time intervals may yield useful information and improve outcomes. We examined the influence of decisions taken on the basis of 1- and 3-month protocol biopsies findings on 1-year renal allograft function in a prospective randomized study. Out of 102 living-donor allograft recipients, 52 were randomized to undergo protocol biopsies and 50 controls had only indicated biopsies. All acute rejection (AR) episodes (clinical and subclinical) were treated. Calcineurin inhibitor (CNI) dose adjustments were made on clinical judgment. Baseline recipient and donor characteristics, immunosuppressive drug usage, HLA matches and 2-h cyclosporine levels were similar in both groups. At 1 and 3 months, protocol biopsies revealed borderline (BL) changes in 11.5% and 14% patients, AR in 17.3% and 12% and chronic allograft nephropathy (CAN) in 3.8% and 10%. The incidence of clinically evident AR episodes was similar in the two groups, but biopsy group had lower serum creatinine at 6 months (p = 0.0003) and 1 year (p < 0.0001). The renal functions were similar in those with normal histology and BL changes. Protocol biopsies are helpful in detecting subclinical histological changes in the graft and improving short-term renal allograft function.     

Association of treatment with 15-deoxyspergualin and BK virus nephropathy in kidney allograft recipients

OBJECTIVE: BK virus nephropathy (BKVN) has been proposed as an important cause of allograft dysfunction and loss in kidney allograft recipient over the last decade. Intense immunosuppression and tubular injury have been shown to promote the replication of polyomavirus. 15-deoxyspergualin (DSG), an effective immunosuppressive agent, is used as a rescue drug for acute rejection in clinical renal transplantation in Japan. To determine whether DSG is a risk factor for BKVN and outline the relationship among BKVN, DSG, and other risk factors, we analyzed 88 patients who received living-related renal transplantation between January 1999 and April 2003. METHODS: A total of 114 biopsy specimens from 88 living-related kidney transplantation recipients (performed between January 1999 to April 2003) were retrospectively analyzed. Patients received immunosuppression therapy based on calcineurin inhibitors and corticosteroid [tacrolimus (TAC) 33 and cyclosporin (CyA) 55]. Additionally, mycophenolate mofeteil (MMF) was used in 21 patients; DSG was used in seven patients; and anti-CD3 monoclonal antibody was used in 16 patients. We analyzed the degree of donor/recipient human leucocyte antigen (HLA) compatibility assessed by the number of HLA-A, -B, and -DR-mismatched antigens in 88 patients. The diagnosis of BKVN was made by the light microscopic examination and a positive immunohistochemical staining of anti-40 antibody in biopsy specimens. Patients were divided into two groups of group A (mild histological change) and group B (moderate or severe histological change) to determine the risk factors in different histological staging. The clinical course of two typical patients in different histological stage is described briefly to outline the risk factors of BKVN. RESULTS: We identified seven cases of BKVN (8.0%) from 88 transplanted patients. Significantly higher incidence of combination regimen consisting of TAC and MMF in BKVN group was noticed compared with non-BKVN group (57.1% vs. 9.9%; p = 0.003). BKVN was associated with a significantly higher incidence of DSG administration compared with non-BKVN group (57.1% vs. 3.7%; p 相似文献   

Quantification of BK Viral Load in Asymptomatic Renal Allograft Recipients

Introduction: Polyoma BK virus (BKV) has recently been identified to cause renal allograft dysfunction, which manifests as polyomavirus-associated nephropathy (PVAN). However, the presence and level of BKV DNA in renal allograft patients with good and stable renal function have remained undetermined. Methods: In this prospective study, serum samples were collected from a total of 45 renal allograft recipients with serum creatinine <155 μmol/L. In 17 patients, whose duration of transplantation was under 2 years, samples were collected at 3–4-month intervals for up to 2 years after transplantation. BK viral load was quantified using quantitative polymerase chain reaction (Q-PCR). Results: The BK viral load in asymptomatic renal allograft recipients was independent of the duration of transplantation and did not correlate with allograft function. The mean (± SD) level of viremia was 552.80 ± 1931.00 genome copies/mL, with 92.9% of patients having low levels of viremia corresponding to <1 × 10³ copies/mL. In contrast, patients with proven PVAN had levels in the range of 10⁶ copies/mL. Conclusions: The prevailing BK viral load in asymptomatic renal allograft patients is quantifiably low. Our findings may guide optimal immunosuppressive modulation in PVAN cases, where judicious manipulation of immunosuppression is required without inciting allograft rejection.     

Glomerular Enlargement Assessed by Paired Donor and Early Protocol Renal Allograft Biopsies

The aim of the study was to evaluate the evolution of glomerular volume 4 months after transplantation. Mean glomerular volume (Vg) was estimated according to the Weibel and Gomez method in a donor and a protocol biopsy done at 139 +/- 58 d in 41 stable grafts. Biopsies were also evaluated according to the Banff schema. Vg increased after transplantation from 4.1 +/- 1.4 to 5.1 +/- 2.4 x 10(6) micro3 (p=0.02). In patients with chronic allograft nephropathy in the protocol biopsy (n=14), the Vg enlargement was -0.3 +/-x 10(6) micro3 while in patients without chronic allograft nephropathy (n=27), glomerular enlargement was 1.6 +/- 2.1 x 10(6) micro3 (p=0.01). There was a negative association between glomerular volume in the donor biopsy and glomerular enlargement after transplantation (R=- 0.34, p=0.03). Multivariate regression analysis confirmed that Vg in the donor biopsy and chronic allograft nephropathy in the protocol biopsy were independent predictors of glomerular enlargement after transplantation (R=0.48, p=0.01). Moreover, Vg in the protocol biopsy correlated with creatinine clearance at the time of biopsy (R=0.38, p=0.01). Glomeruli enlarge after transplantation and glomerular volume after 4 months correlates with creatinine clearance, suggesting that glomerular enlargement is a necessary condition for renal adaptation to the recipient. Glomerular enlargement is impaired in patients with chronic allograft nephropathy.     

Impact of Cyclosporine Reduction With MMF: A Randomized Trial in Chronic Allograft Dysfunction. The ''Reference'' Study

Long-term use of calcineurine inhibitors (CNIs) may contribute to the development of chronic allograft dysfunction (CAD). We investigate the impact of the introduction of MMF combined with cyclosporine (CsA) 50% dose reduction. An open, randomized, controlled, multicenter, prospective study was conducted in 103 patients, receiving a CsA-based therapy with a serum creatinine between 1.7-3.4 mg/dL, more than 1 year after transplantation. They were randomized to receive MMF with half dose of CsA (MMF group) or to continue their maintenance CsA dose (control group). A total of 96 weeks after randomization, the evolution of renal function assessed by regression line analysis of 1/SeCr improved in the MMF group (positive slope) vs. the control group (negative slope), 4.2 x 10(-4) vs. -3.0 x 10(-4), respectively (p < 0.001). Concurrently, the absolute renal function improved significantly in the MMF group. No episode of biopsy-proven acute rejection occurred. One patient in each group lost his graft because of biopsy-proven chronic allograft nephropathy. There was a significant decrease of triglycerides level in the MMF group. Anemia and diarrhea were statistically more frequent in the MMF group. In CAD, the reduction of CsA in the presence of MMF results in significant improvement in renal function during a 2-year follow-up.     

Renal Allograft Histology at 10 Years After Transplantation in the Tacrolimus Era: Evidence of Pervasive Chronic Injury

Improving long‐term renal allograft survival remains an important unmet need. To assess the extent of histologic injury at 10 years after transplantation in functioning grafts, we studied 575 consecutive adult solitary renal transplants performed between 2002 and 2005: 77% from living donors and 81% maintained on tacrolimus‐based immunosuppression. Ten‐year graft survival was 59% and death‐censored graft survival was 74%. Surveillance allograft biopsies were assessed at implantation, 5 years, and 10 years from 145 patients who reached 10 years. At implantation, 5% of biopsies had major histologic abnormalities (chronic transplant glomerulopathy score > 0, other chronic Banff scores ≥ 2, global glomerulosclerosis > 20%, or mesangial sclerosis ≥ 2). This increased to 54% at 5 years and 82% at 10 years. Major lesions at 10 years included the following: arteriolar hyalinosis (66%), mesangial sclerosis (67%), and global glomerulosclerosis > 20% (43%), with 48% of grafts having more than one major lesion. Transplant glomerulopathy and moderate‐to‐severe interstitial fibrosis were uncommon (12% each). Major lesions were associated with increased proteinuria and decreased graft function. In patients with diabetes at baseline, 52% had diabetic nephropathy/mesangial sclerosis at 10 years. We conclude that almost all renal allografts sustain major histologic injury by 10 years after transplantation. Much damage appears nonimmunologic, suggesting that new approaches are needed to decrease late injury.     

Prospective, Pilot, Open-Label, Short-Term Study of Conversion to Leflunomide Reverses Chronic Renal Allograft Dysfunction

Leflunomide (LEF) is a synthetic isoxazole derivative with anti-inflammatory and antiviral properties, which has been reported to prevent acute rejection and delay progression of chronic allograft nephropathy (CAN) in animal models. We performed a pilot, crossover trial in 22 renal transplant recipients who were converted from azathioprine (AZA) or mycophenolate mofetil (MMF) to LEF in an effort to slow progression of renal dysfunction [deteriorating renal function (n = 5), cyclosporine (CyA) nephrotoxicity (n = 4) or biopsy-proven CAN (n = 13)]. Baseline maintenance immunosuppression consisted of CyA, AZA or MMF and prednisone. Six-month postconversion patient and graft survival was 100% and 91%, respectively. Mean serum creatinine 6months preconversion was 2.2 +/- 0.6mg/dL, at initiation was 3.0 +/- 1.1 mg/dL, and 6 months postconversion was 2.8 +/- 1.3 mg/dL. The rate of change in serum creatinine was 35 +/- 39%/6 months preconversion and -5 +/- 21%/6 months postconversion to LEF (p = 0.003). Two patients discontinued LEF for diarrhea and myalgia. No readmissions, increase in liver function tests, infections or acute rejection episodes occurred. Mean CyA levels did not change, 146 +/- 72 ng/ mL pre-LEF vs. 132 +/- 51 ng/mL post-LEF, p = NS. Conversion to LEF reversed progression of chronic renal allograft dysfunction with minimal toxicity.     

Post-Transplant Anti-HLA Class II Antibodies as Risk Factor for Late Kidney Allograft Failure

The purpose of this study was to prospectively analyze the relationship between the post-transplant anti-HLA class I and/or class II panel reactive antibodies and graft failure due to chronic allograft nephropathy (CAN). We studied 512 first kidney recipients transplanted at a single center, with a graft functioning for at least 3 years. A single blood sample was collected from each patient for antibody evaluation. The median posttransplant time after blood collection was 4.4 years and did not differ between patients with (n = 91) or without anti-HLA antibodies (n = 421). Female gender, pregnancies and blood transfusions were associated with the presence of anti-HLA class I antibodies. Graft function deterioration was associated with anti-HLA class II antibodies. Multivariate analysis showed independent association for creatinine levels (RR = 7.5), acute rejection (RR = 2.6), recipient male gender (RR = 3.6) and anti-HLA class II antibodies (RR = 2.9) and CAN-associated graft loss. In conclusion, the presence of anti-HLA class II antibodies conferred a risk for graft loss before a decline in renal function and increased the risk of graft failure in patients who already had a decline in graft function. Thus, anti-HLA class II antibody monitoring is a useful tool for the management of long-term kidney recipients.     

Kidney Allograft Fibrosis and Atrophy Early After Living Donor Transplantation

Kidney allograft failure is most often caused by chronic allograft nephropathy, a process of interstitial fibrosis (GIF) and tubular atrophy (TA). We assessed the pathology of living donor (LD) grafts compared to deceased donor (DD). Included are 321 recipients (245 LD; 76 DD) with protocol biopsies the first 2 years of transplant. In LD, GIF was present in 7%, 31%, 61% and 71% of grafts at 0, 4, 12 and 24 months. TA progressed in parallel to GIF. Compared to LD, more DD grafts had GIF at time 0 (29%, p = 0.002); thereafter the incidence of GIF was similar. In LD, GIF was associated with lower glomerular filtration rate (GFR)(1 year) (no GIF, 62 +/- 16; GIF, 49 +/- 15 mL/min/m(2) iothalamate clearance, p = 0.001) and reduced graft survival (HR = 2.2, p = 0.009). GIF in LD related to acute rejection (HR = 2.6, p = 0.01), polyoma nephropathy (OR = 4.4, p = 0.02) and lower levels of GFR 3 weeks post-transplant (HR = 0.961; p = 0.03, multivariate). However, GIF also developed in 53% of recipients lacking these covariates. Thus, GIF/TA develops in the majority of LD grafts, it is often mild but is associated with reduced function and survival. GIF frequently develops in the absence of risk factors. Lower GFR post-transplant identify patients at highest risk of GIF.     

Therapeutic Targets in the Treatment of Allograft Fibrosis

The dramatic improvements in short-term graft survival and acute rejection rates could only have been dreamed of 20 years ago. Late graft loss following kidney transplantation is now the critical issue of this decade. Frequently, graft loss is associated with the development of tubular atrophy and interstitial fibrosis within the kidney (i.e. chronic allograft nephropathy; CAN). Major treatment strategies in this disorder are non-specific and the focus of intervention has been on limiting injurious events. Following graft injury is a fibrogenesis phase featuring both proliferative and infiltrative responses mediated by chemokines, cytokines and growth factors. In particular, TGFβ has been strongly implicated in the pathogenesis of chronic injury and epithelial-mesenchymal transformation (EMT) may be part of this process. The cascade of events results in matrix accumulation, due to either increased production and/or reduced degradation of matrix. Recent investigations into the pathogenesis of tissue fibrosis have suggested a number of new strategies to ameliorate matrix synthesis. While the majority of therapies have focused on TGFβ, this may not be an ideal maneuver in transplant settings and alternative targets identified in other fibrotic diseases will be discussed. Attacking graft fibrosis should be a new focus in organ transplantation.     

Mycophenolate Mofetil Is Associated with Altered Expression of Chronic Renal Transplant Histology

Mycophenolate mofetil (MMF) reduces acute rejection in controlled trials of kidney transplantation and is associated with better registry graft survival. Recent experimental studies have demonstrated additional antifibrotic properties of MMF, however, human histological data are lacking. We evaluated sequential prospective protocol kidney biopsies from two historical cohorts treated with cyclosporine (CSA)-based triple therapy including prednisolone and either MMF (n = 25) or azathioprine (AZA, n = 25). Biopsies (n = 360) were taken from euglycemic kidney-pancreas transplant recipients. Histology was independently assessed by the Banff schema and electron microscopic morphometry. MMF reduced acute rejection and OKT3 use (p < 0.05) compared with AZA. MMF therapy was associated with limited chronic interstitial fibrosis, striped fibrosis and periglomerular fibrosis (p < 0.05-0.001), mesangial matrix accumulation (p < 0.01), chronic glomerulopathy scores (p < 0.05) and glomerulosclerosis (p < 0.05). MMF was associated with delayed expression of CSA nephrotoxicity, reduced arteriolar hyalinosis, striped fibrosis and tubular microcalcification (p < 0.05-0.001). The beneficial effects of MMF remained in recipients without acute rejection. Retrospective analysis shows that MMF therapy was associated with substantially reduced fibrosis in the glomerular, microvascular and interstitial compartments, and a delayed expression of CSA nephrotoxicity. These outcomes may be due to a limitation of immune-mediated injury and suggest a direct effect of reduced fibrogenesis.     

Renal Allograft Protection with Angiotensin II Type 1 Receptor Antagonists

The renal benefits of agents inhibiting the renin-angiotensin-aldosterone system in renal transplant recipients, i.e. preventing the development of chronic graft nephropathy, are supposed but not finally proven. In a double-blind, placebo-controlled, cross-over study, we evaluated the influence of losartan on surrogate markers of tubular injury, urine excretion of transforming growth factor beta-1 (TGF-beta1) and amino-terminal propeptide of type III procollagen (PIIINP) in 16 patients after transplantation. The patients received randomly either losartan (50-100 mg daily) or the beta-blocker carvedilol (12.5-25 mg) for 8 weeks, allowing a placebo washout between treatments. The target office through blood pressure (BP) was below 130/85 mmHg. The BP did not differ in the treatment periods. Losartan significantly decreased N-acetyl-beta-d-glucosaminidase and alfa-1 microglobulin excretion relative to placebo and carvedilol. Urine excretion of TGF-beta1 and PIIINP was significantly lower after losartan. In conclusion, losartan reduces urine excretion of proteins associated with tubular damage and graft fibrosis.     

Subclinical Inflammation and Chronic Renal Allograft Injury in a Randomized Trial on Steroid Avoidance in Pediatric Kidney Transplantation

Steroid avoidance is safe and effective in children receiving kidney transplants in terms of graft function and survival, but the effects on allograft histology are unknown. In this multicenter trial, 130 pediatric renal transplant recipients were randomized to steroid‐free (SF; n = 60) or steroid‐based (SB; n = 70) immunosuppression, and underwent renal allograft biopsies at the time of graft dysfunction and per protocol at implantation and 6, 12 and 24 months after transplantation. Clinical follow‐up was 3 years posttransplant. Subclinical acute rejection was present in 10.6% SF versus 11.3% SB biopsies at 6 months (p = 0.91), 0% SF versus 4.3% SB biopsies at 1 year (p = 0.21) and 0% versus 4.8% at 2 years (p = 0.20). Clinical acute rejection was present in 13.3% SF and 11.4% SB patients by 1 year (p = 0.74) and in 16.7% SF and 17.1% SB patients by 3 years (p = 0.94) after transplantation. The cumulative incidence of antibody‐mediated rejection was 6.7% in SF and 2.9% in SB by 3 years after transplantation (p = 0.30). There was a significant increase in chronic histological damage over time (p < 0.001), without difference between SF and SB patients. Smaller recipient size and higher donor age were the main risk factors for chronic histological injury in posttransplant biopsies.     

Renal dysfunction and intragraft proMMP9 activity in renal transplant recipients with interstitial fibrosis and tubular atrophy

Chronic renal allograft injury is reflected by interstitial fibrosis and tubular atrophy (IF/TA) and by the accumulation of extracellular matrix (ECM). Metalloproteinases (MMPs) are renal physiologic regulators of ECM degradation. Changes in MMPs expression or activity may disturb ECM turnover leading to glomerular scarring and worsening renal function. Our goal was to investigate intragraft MMP2 and MMP9 activities and their correlation with renal dysfunction. Plasma MMP2 and MMP9 activities were analyzed as noninvasive markers of renal allograft deterioration. Transplanted patients were biopsied and histopathologically characterized as IF/TA+ or IF/TA?. Renal function was evaluated by serum creatinine, glomerular filtration rate (GFR) estimated by Modification of Diet in Renal Disease equation and urinary protein/creatinine ratio. Kidney and plasma MMP2 and MMP9 activities were analyzed by zymography. A significant renal dysfunction was observed in IF/TA+ patients. Intragraft proMMP9 showed a significant higher activity in IF/TA+ than in IF/TA? samples and was inversely correlated with the GFR. Intragraft proMMP2 activity tended to increase in IF/TA+ samples, although no statistic significance was reached. Circulating proMMP2 and proMMP9 activities did not show significant differences between groups. Our data provide evidence that correlates intragraft proMMP9 activity with the fibrotic changes and renal dysfunction observed in IF/TA.     

Surrogate Markers for Long-Term Renal Allograft Survival

Progressive improvement in kidney transplant survival rates and reduction in acute rejection rates have ironically restricted our ability to evaluate newer therapy. Current short-term endpoints such as acute rejection rates have reduced utility in predicting long-term survival. Long-term graft survival is an ideal endpoint, but is limited by longer follow-up requirements and the large cohort of patients required for such studies. Newer short-term surrogate markers should be identified and these markers should correlate with long-term graft failure. Hence, identification of short-term surrogate markers is critical to test newer immunosuppressive strategies over current therapies, and should also predict long-term transplant outcome. Potential surrogate markers are clinical parameters such as renal function, renal histological findings of fibrosis and immunological markers. Post-transplant renal function estimated by serum creatinine within 1 year has been shown to correlate with long-term survival. Alternative evaluation of renal function such as clearance studies and cystatin C, which are more accurate, could potentially be useful in clinical trials. Renal histological indices such as fibrosis measured as Chronic Allograft Disease Index score or Banff score correlate with long-term graft survival. Immunological markers such as antidonor antibodies, levels of blood and urine cytokines, real time PCR, ELISPOT and microarrays are attractive surrogates to consider. Measurement of morbidity and mortality after transplantation is critical to further enhance long-term survival. Thus, there are many potential surrogate markers and these individually or in combination with conventional endpoints should be implemented in clinical trials and validated in long-term studies.     

Subclinical Rejection Associated with Chronic Allograft Nephropathy in Protocol Biopsies as a Risk Factor for Late Graft Loss

Chronic allograft nephropathy (CAN) in protocol biopsies is associated with graft loss while the association between subclinical rejection (SCR) and outcome has yielded contradictory results. We analyze the predictive value of SCR and/or CAN in protocol biopsies on death-censored graft survival. Since 1988, a protocol biopsy was done during the first 6 months in stable grafts with serum creatinine <300 micromol/L and proteinuria <1 g/day. Biopsies were evaluated according to Banff criteria. Borderline changes and acute rejection were grouped as SCR. CAN was defined as presence of interstitial fibrosis and tubular atrophy. Mean follow-up was 91 +/- 46 months. Sufficient tissue was obtained in 435 transplants. Biopsies were classified as normal (n = 186), SCR (n = 74), CAN (n = 110) and SCR with CAN (n = 65). Presence of SCR with CAN was associated with old donors, percentage of panel reactive antibodies and presence of acute rejection before protocol biopsy. Cox regression analysis showed that SCR with CAN (relative risk [RR]: 1.86, 95% confidence interval [CI]: 1.11-3.12; p = 0.02) and hepatitis C virus (RR: 2.27, 95% CI: 1.38-3.75; p = 0.01) were independent predictors of graft survival. In protocol biopsies, the detrimental effect of interstitial fibrosis/tubular atrophy on long-term graft survival is modulated by SCR.