Predictors of renal allograft histologic damage progression

Arteriolar hyalinization at 0-hour biopsy predicts long-term graft function in deceased kidney transplantation

OBJECTIVES

Regarding the relationship between donor kidney quality and renal graft function after deceased kidney transplantation (KTx) following donation after cardiac death (DCD), the evaluation timing varies depending on the study. Evaluation of histology and changes in long-term renal graft function is limited.

METHODS

A retrospective single-center study included 71 recipients who underwent 0-hour biopsy for KTx from DCD. The recipients were divided into two groups to evaluate factors related to renal graft function (study1). The two groups were categorized as stable graft function and poor graft function with the change of estimated glomerular filtration rate (eGFR) after KTx. The recipients were then divided into four groups to assess whether the factors identified in study1 were related to the change in long-term renal graft function (study2). They were categorized as follows: Improved, Stable, Deteriorated, and Primary non-function with the change of eGFR after KTx.

RESULTS

In study1, donor age ≥ 50 years (29.5% vs. 65.2%; p = 0.09), banff arteriolar hyalinosis (ah) score (0.66 ± 0.78 vs. 1.2 ± 1.0; p = 0.018), and presence of glomerulosclerosis (43.2% vs. 76.2%; p = 0.017) were significant risk factors for poor long-term graft function. When the recipients were divided into four groups, the severity of ah correlated well with changes in long-term renal function.

CONCLUSIONS

We can predict the shift in long-term renal graft function after KTx from DCD according to the severity of ah by 0-hour biopsy.

Performance of Scores Predicting Adverse Outcomes in Procurement Kidney Biopsies From Deceased Donors With Organs of Lower-Than-Average Quality

Several scores have been devised for providing a prognosis of outcomes after kidney transplantation. This study is a comprehensive test of these scores in a cohort of deceased donors with kidneys of lower-than-average quality and procurement biopsies. In total, 15 scores were tested on a retrospective cohort consisting of 221 donors, 223 procurement biopsies, and 223 recipient records for performance on delayed graft function, graft function, or death-censored graft loss. The best-performing score for DGF was the purely clinical Chapal score (AUC 0.709), followed by the Irish score (AUC 0.684); for graft function, the Nyberg score; and for transplant loss, the Snoeijs score (AUC 0.630) and the Leuven scores (AUCs 0.637 and 0.620). The only score with an acceptable performance was the Chapal score. Its disadvantage is that knowledge of the cold ischemia time is required, which is not known at allocation. None of the other scores performed acceptably. The scores fared better in discarded kidneys than in transplanted kidneys. Our study shows an unmet need for practical prognostic scores useful at the time of a decision about discarding or accepting deceased donor kidneys of lower-than-average quality in the Eurotransplant consortium.

Impact of Time-Zero Biopsy on the Outcome of Transplanted Kidneys

BACKGROUND

A low supply of donated organs led to the expansion of criteria for kidney transplantation (KT), and the impact on late glomerular function rates (eGFR) is still uncertain. This study aimed to correlate the histologic findings at time-zero biopsy (TzB) with the final eGFR, to identify criteria that could help achieve a more thorough preimplantation evaluation of the organ.

METHODS

Records from 395 adult deceased KTs were reviewed. TzBs were analyzed considering histologic criteria by compartment (vascular, interstitial, tubular, and inflammatory) and correlated with the eGFR after 1 year.

RESULTS

Among donors, 56.9% were men (mean age 39 years), with the main causes of death being brain trauma (44.2%) and stroke (46.0%). Histologic analysis of TzB revealed 6.0% of glomerulosclerosis; 18.8% presenting vascular alterations; interstitial fibrosis in 54.6%; tubular changes in 76.9%, and nonspecific inflammatory infiltrate in 2.3%. Linear regression analysis showed that the main histologic findings that had impact in the eGFR were interstitial fibrosis (P = .000), followed by tubular alterations (P = .036) and glomerulosclerosis (P = .008).

CONCLUSIONS

Histologic variables like interstitial fibrosis and tubular alterations show the most significant negative correlation with final eGFR. The effect of glomerulosclerosis may not be as important as formerly suggested in the literature.

Histological and clinical evaluation of marginal donor kidneys before transplantation: Which is best?

Organ shortage represents one of the major limitations to the development of kidney transplantation. To increase the donor pool and to answer the ever increasing kidney request, physicians are recurring to marginal kidneys as kidneys from older donors, from hypertensive or diabetic donors and from non-heart beating donors. These kidneys are known to have frequently a worse outcome in the recipients. To date major problem is to evaluate such kidneys in order to use or to discard them before transplantation. The use of such kidneys create other relevant question as whether to use them as single or dual transplant and to allocate them fairly according transplant programs. The pre-transplant histological evaluation, the clinical evaluation of the donor or both the criteria joined has been used and according the time each criterion prevailed over the others. Aim of this review has been to examine the advantages and the drawbacks of any criterion and how they have changed with time. To date any criterion has several limitations and several authors have argued for the development of new guidelines in the field of the kidney evaluation for transplantation. Several authors argue that the use of omic technologies should improve the organ evaluation and studies are ongoing to evaluate these technologies either in the donor urine or in the biopsies taken before transplantation.

Causes of late transplant failure in cyclosporine-treated kidney allograft recipients

BACKGROUND

There is little information about very long-term outcomes of kidney allograft recipients exposed to calcineurin inhibitors.

METHODS

In this single-centre retrospective study with 20-year follow-up, we analyzed data from 644 patients who underwent primary renal transplantation between 1983 and 1993. Participants were treated with a cyclosporine-based immunosuppressive scheme and had allograft function at 1 year.

RESULTS

After 20 years, 15.2% patients died, 39.7% experienced allograft loss, 26.8% were alive with a functioning transplant, and 18.2% were lost to follow-up. Cardiovascular disease (30.8%), malignancy (26.6%) and infection (17.0%) were the main causes of death. Age, new-onset proteinuria > 1 g/day, major acute cardiovascular event (MACE), and malignancy were independent predictors of mortality at time-dependent multivariate analysis. Chronic rejection (63.3%), recurrent glomerulonephritis (14.0%), and nonspecific interstitial fibrosis/tubular atrophy (13.2%) were the leading cause of allograft loss. Basal disease, hepatitis C, difference between 1 year and nadir serum creatinine, new-onset proteinuria > 1 g/day, and MACE were independent predictors of transplant failure. Among patients with 20-year allograft function, we recorded the following complications: hypertension (85%), malignancy (13%), diabetes (9%), and cardiovascular disease (9%). Median serum creatinine and proteinuria were 1.4 mg/dL and 0.6 g/day, respectively.

CONCLUSIONS

Prolonged use of cyclosporine may expose to several dose-related adverse events and may contribute to the development of allograft dysfunction but it does not necessarily cause relentless, progressive transplant failure if patients are carefully and consistently monitored during the follow-up.

Regulated necrosis in kidney ischemia-reperfusion injury

Ischemia-reperfusion injury (IRI) is the outcome of an inflammatory process that is triggered when an organ undergoes a transient reduction or cessation of blood flow, followed by re-establishment of perfusion. In the clinical setting, IRI contributes to significant acute kidney injury, patient morbidity and mortality, and adverse outcomes in transplantation. Tubular cell death by necrosis and apoptosis is a central feature of renal IRI. Recent research has challenged traditional views of cell death by identifying new pathways in which cells die in a regulated manner but with the morphologic features of necrosis. This regulated necrosis (RN) takes several forms, with necroptosis and ferroptosis being the best described. The precise mechanisms and relationships between the RN pathways in renal IRI are currently the subject of active research. The common endpoint of RN is cell membrane rupture, resulting in the release of cytosolic components with subsequent inflammation and activation of the immune system. We review the evidence and mechanisms of RN in the kidney following renal IRI, and discuss the use of small molecule inhibitors and genetically modified mice to better understand this process and guide potentially novel therapeutic interventions.

Zero-Time Renal Transplant Biopsies: A Comprehensive Review

Zero-time kidney biopsies, obtained at time of transplantation, are performed in many transplant centers worldwide. Decisions on kidney discard, kidney allocation, and choice of peritransplant and posttransplant treatment are sometimes based on the histological information obtained from these biopsies. This comprehensive review evaluates the practical considerations of performing zero-time biopsies, the predictive performance of zero-time histology and composite histological scores, and the clinical utility of these biopsies. The predictive performance of individual histological lesions and of composite scores for posttransplant outcome is at best moderate. No single histological lesion or composite score is sufficiently robust to be included in algorithms for kidney discard. Dual kidney transplantation has been based on histological assessment of zero-time biopsies and improves outcome in individual patients, but the waitlist effects of this strategy remain obscure. Zero-time biopsies are valuable for clinical and translational research purposes, providing insight in risk factors for posttransplant events, and as baseline for comparison with posttransplant histology. The molecular phenotype of zero-time biopsies yields novel therapeutic targets for improvement of donor selection, peritransplant management and kidney preservation. It remains however highly unclear whether the molecular expression variation in zero-time biopsies could become a better predictor for posttransplant outcome than donor/recipient baseline demographic factors.

Expression of decoy receptor 3 in kidneys is associated with allograft survival after kidney transplant rejection

Decoy receptor 3 (DcR3) expression in kidneys has been shown to predict progression of chronic kidney disease. We prospectively investigated a cohort comprising 96 renal transplant recipients (RTRs) undergoing graft kidney biopsies. Computer-assisted quantitative immunohistochemical staining value of DcR3 in renal tubular epithelial cells (RTECs) was used to determine the predictive role of DcR3 in kidney disease progression. The primary end point was doubling of serum creatinine and/or graft failure. A multivariate Cox proportional hazards model was used to assess the risk of DcR3 expression in rejected kidney grafts toward the renal end point. In total, RTRs with kidney allograft rejection were evaluated and the median follow-up was 30.9 months. The greater expression of DcR3 immunoreactivity in RTECs was correlated with a higher rate of the histopathological concordance of acute T cell-mediated rejection. Compared with 65 non-progressors, 31 progressors had higher DcR3 expression (HDE) regardless of the traditional risk factors. Cox regression analysis showed HDE was significantly associated with the risk of renal end point with a hazard ratio of 3.19 (95% confidence interval, 1.40 to 7.27; P = 0.006) after adjusting for other variables. In repetitive biopsies, HDE in tissue showed rapid kidney disease progression due to persistent inflammation.

The Donor Kidney Biopsy and Its Implications in Predicting Graft Outcomes: A Systematic Review

Despite a growing organ shortage in the United States, many deceased donor kidneys removed for transplantation are discarded. Kidney biopsy findings often play a role in these discards, although it is not clear whether biopsies reliably inform acceptance decisions. Therefore, we carried out a systematic review of the medical literature on the utility of both procurement and implantation biopsies for predicting posttransplant outcomes. Between January 1, 1994 and July 1, 2014, 47 studies were published in the English language literature that examined the association between pretransplant donor biopsy findings from 50 or more donors (with more than half being from deceased donors) and either posttransplant graft failure, delayed graft function, or graft function. In general, study quality was poor. All were retrospective or did not indicate if they were prospective. Results were heterogeneous, with authors as often as not concluding that biopsy results did not predict posttransplant outcomes. The percent glomerular sclerosis was most often examined, and failed to predict graft failure in 7 of 14 studies. Of 15 semiquantitative scoring systems proposed, none consistently predicted posttransplant outcomes across studies. Routine use of biopsies to help determine whether or not to transplant a kidney should be reexamined.

Update on ischemia-reperfusion injury in kidney transplantation: Pathogenesis and treatment

Ischemia/reperfusion injury is an unavoidable relevant consequence after kidney transplantation and influences short term as well as long-term graft outcome. Clinically ischemia/reperfusion injury is associated with delayed graft function, graft rejection, chronic rejection and chronic graft dysfunction. Ischemia/reperfusion affects many regulatory systems at the cellular level as well as in the renal tissue that result in a distinct inflammatory reaction of the kidney graft. Underlying factors of ischemia reperfusion include energy metabolism, cellular changes of the mitochondria and cellular membranes, initiation of different forms of cell death-like apoptosis and necrosis together with a recently discovered mixed form termed necroptosis. Chemokines and cytokines together with other factors promote the inflammatory response leading to activation of the innate immune system as well as the adaptive immune system. If the inflammatory reaction continues within the graft tissue, a progressive interstitial fibrosis develops that impacts long-term graft outcome. It is of particular importance in kidney transplantation to understand the underlying mechanisms and effects of ischemia/reperfusion on the graft as this knowledge also opens strategies to prevent or treat ischemia/reperfusion injury after transplantation in order to improve graft outcome.

The effect of ischemia/reperfusion on the kidney graft

PURPOSE OF REVIEW

Ischemia/reperfusion injury is an unavoidable companion after kidney transplantation and influences short-term as well as long-term graft outcome. Clinically ischemia/reperfusion injury is associated with delayed graft function, graft rejection, and chronic graft dysfunction. Ischemia/reperfusion affects many regulatory systems at the cellular level as well as in the renal tissue that eventually result in a distinct inflammatory reaction of the kidney graft.

RECENT FINDINGS

Underlying factors include energy metabolism, cellular changes of the mitochondria and cellular membranes, initiation of different forms of cell death-like apoptosis and necrosis together with a recently discovered mixed form termed necroptosis. Chemokines and cytokines together with other factors promote the inflammatory response leading to activation of the innate immune system as well as the adaptive immune system. If the inflammatory reaction continues within the graft tissue, a progressive interstitial fibrosis develops that impacts long-term graft outcome.

SUMMARY

It is of particular importance in kidney transplantation to understand the underlying mechanisms and effects of ischemia/reperfusion on the graft as this knowledge also opens strategies to prevent or treat ischemia/reperfusion injury after transplantation in order to improve graft outcome.

Factors affecting eGFR 5-year post-deceased donor renal transplant: analysis and predictive model

AIM

Long-term survival of renal allografts has improved over the last 20 years. However, less is known about current expectations for long-term allograft function as determined by estimated glomerular filtration rate (eGFR). The aim of this study was to investigate factors which affect graft function at 5 years' post-renal transplantation. The statistically significant factors were then used to construct a predictive model for expected eGFR at five years' post-transplant.

METHODS

We retrospectively reviewed all adult patients who received a renal transplant in the Republic of Ireland between 1990 and 2004. Data collected included era of transplantation (1990-1994, 1995-1999, 2000-2004), donor and recipient age and gender, number of human leucocyte antigen mismatches, cold ischemia time (CIT), number of prior renal transplants, immunosuppressive regimen used and acute rejection episodes. Estimated GFR was calculated at 5 years after transplantation from patient data using the Modified Diet in Renal Disease (MDRD) equation. Consecutive sampling was used to divide the study population into two equal unbiased groups of 489 patients. The first group (derivation cohort) was used to construct a predictive model for eGFR five years' post-transplantation, the second (validation cohort) to test this model.

RESULTS

Nine hundred and seventy eight patients were analyzed. The median age at transplantation was 43 years (range 18-78) and 620 (63.4%) were male. One hundred and seventy five patients (17.9%) had received a prior renal transplant. Improved eGFR at five years' post-transplantation was associated with tacrolimus-based combination immunosuppression, younger donor age, male recipient, absence of cytomegalovirus disease and absence of acute rejection episodes as independently significant factors (p < 0.05). The predictive model developed using these factors showed good correlation between predicted and actual median eGFR at five years. The model explained 20% of eGFR variability. The validation model findings were consistent with the derivation model (21% variability of eGFR explained by model using same covariates on new data).

CONCLUSION

The predictive model we have developed shows good correlation between predicted and actual median eGFR at five years' post-transplant. Applications of this model include comparison of current and future therapy options such as new immunosuppressive regimens.

Biological pathways and potential targets for prevention and therapy of chronic allograft nephropathy

Renal transplantation (RT) is the best option for patients with end-stage renal disease, but the half-life is limited to a decade due to progressive deterioration of renal function and transplant failure from chronic allograft nephropathy (CAN), which is the leading cause of transplant loss. Extensive research has been done to understand the pathogenesis, the biological pathways of fibrogenesis, and potential therapeutic targets for the prevention and treatment of CAN. Despite the advancements in the immunosuppressive agents and patient care, CAN continues to remain an unresolved problem in renal transplantation. The aim of this paper is to undertake a comprehensive review of the literature on the pathogenesis, biological pathways of RT fibrogenesis, and potential therapeutic targets for the prevention and therapy of CAN.

The role of procurement biopsies in acceptance decisions for kidneys retrieved for transplant

BACKGROUND AND OBJECTIVES

There is a shortage of kidneys for transplant, and many patients on the deceased donor kidney transplant waiting list would likely benefit from kidneys that are currently being discarded. In the United States, the most common reason given for discarding kidneys retrieved for transplant is procurement biopsy results. This study aimed to compare biopsy results from discarded kidneys with discard attributed to biopsy findings, with biopsy results from comparable kidneys that were successfully transplanted.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

In this retrospective, observational, case-control study, biopsy reports were examined from 83 kidneys discarded in 2010 due to biopsy findings (cases), 83 contralateral transplanted kidneys from the same donor (contralateral controls), and 83 deceased donors randomly matched to cases by donor risk profile (randomly matched controls). A second procurement biopsy was obtained in 64 of 332 kidneys (19.3%).

RESULTS

The quality of biopsy reports was low, with amounts of tubular atrophy, interstitial inflammation, arteriolar hyalinosis, and acute tubular necrosis often not indicated; 69% were wedge biopsies and 94% used frozen tissue. The correlation between first and second procurement biopsies was poor; only 25% of the variability (R(2)) in glomerulosclerosis was explained by biopsies being from the same kidney. The percentages of glomerulosclerosis overlapped substantially between cases, contralateral controls, and randomly matched controls: 17.1%±15.3%, 9.0%±6.6%, and 5.0%±5.9%, respectively. Of all biopsy findings, only glomerulosclerosis>20% was independently correlated with discard (cases versus contralateral controls; odds ratio, 15.09; 95% confidence interval, 2.47 to 92.41; P=0.003), suggesting that only this biopsy result was used in acceptance decisions. One-year graft survival was 79.5% and 90.7% in contralateral and randomly matched controls, respectively, versus 91.6% among all deceased donor transplants in the Scientific Registry of Transplant Recipients.

CONCLUSIONS

Routine use of biopsies could lead to unnecessary kidney discards.

Acidosis and hyperkalemia caused by losartan and enalapril in pediatric kidney transplant recipients

OBJECTIVES

To evaluate the efficacy and safety of losartan and enalapril in pediatric kidney transplant recipients.

MATERIALS AND METHODS

A retrospective review was performed in 31 pediatric kidney transplant recipients who were treated with losartan (50 mg/d, oral) for 1 to 6 months because of mild hypertension and persistent proteinuria. All patients were treated concurrently with enalapril (5 or 10 mg daily, oral), and 12 patients (39%) also were treated with amlodipine (5 or 10 mg daily, oral). Demographic and clinical characteristics of the patients were reviewed.

RESULTS

Losartan use was associated with a significant decrease in mean systolic (before losartan was started, 123 ± 14 mm Hg; before losartan was stopped, 111 ± 10 mm Hg; P ≤ .001) and diastolic blood pressure (before losartan was started, 78 ± 11 mm Hg; before losartan was stopped, 69 ± 10 mm Hg; P ≤ .001) and urinary protein excretion (before losartan was started, 51 ± 45 mg/m2/h; before losartan was stopped, 28 ± 34 mg/m2/h; P ≤ .001). However, losartan therapy was associated with a significant mean increase in serum potassium level (before losartan was started, 4.0 ± 0.4 mmol/L; before losartan was stopped, 5.7 ± 0.5 mmol/L; P ≤ .001) and decrease in pH (before losartan was started, 7.35 ± 0.0; before losartan was stopped, 7.23 ± 0.0; P ≤ .001). Losartan was stopped because of hyperkalemia and acidosis earlier in patients who were on tacrolimus than cyclosporine immunosuppression (tacrolimus, 3 ± 1 mo; cyclosporine, 4.7 ± 0.8 mo; P ≤ .001).

CONCLUSIONS

Losartan and enalapril may be beneficial in pediatric kidney transplant recipients by decreasing blood pressure and proteinuria, with maintenance of stable graft function, but may be associated with serious adverse events including hyperkalemia and life-threatening acidosis.

Ischaemia-reperfusion injury: a major protagonist in kidney transplantation

Ischaemia-reperfusion injury (IRI) is a frequent event in kidney transplantation, particularly when the kidney comes from a deceased donor. The brain death is usually associated with generalized ischaemia due to a hyperactivity of the sympathetic system. In spite of this, most donors have profound hypotension and require administration of vasoconstrictor agents. Warm ischaemia after kidney vessels clamping and the cold ischaemia after refrigeration also reduce oxygen and nutrients supply to tissues. The reperfusion further aggravates the state of oxidation and inflammation created by ischaemia. IRI first attacks endothelial cells and tubular epithelial cells. The lesions may be so severe that they lead to acute kidney injury (AKI) and delayed graft function (DGF), which can impair the graft survival. The unfavourable impact of DGF is worse when DGF is associated with acute rejection. Another consequence of IRI is the activation of the innate immunity. Danger signals released by dying cells alarm Toll-like receptors that, through adapter molecules and a chain of kinases, transmit the signal to transcription factors which encode the genes regulating inflammatory cells and mediators. In the inflammatory environment, dendritic cells (DCs) intercept the antigen, migrate to lymph nodes and present the antigen to immunocompetent cells, so activating the adaptive immunity and favouring rejection. Attempts to prevent IRI include optimal management of donor and recipient. Calcium-channel blockers, l-arginine and N-acetylcysteine could obtain a small reduction in the incidence of post-transplant DGF. Fenoldopam, Atrial Natriuretic Peptide, Brain Natriuretic Peptide and Dopamine proved to be helpful in reducing the risk of AKI in experimental models, but there is no controlled evidence that these agents may be of benefit in preventing DGF in kidney transplant recipients. Other antioxidants have been successfully used in experimental models of AKI but only a few studies of poor quality have been made in clinical transplantation with a few of these agents and we still lack of unambiguous demonstration that pre-treatment with these antioxidants can attenuate the impact of IRI in kidney transplantation. Interference with the signals leading to activation of innate immunity, inactivation of complement or manipulation of DCs is a promising therapeutic option for the near future.

Antihypertensive pharmacotherapy and long-term outcomes in pediatric kidney transplantation

Hypertension (HTN) is common in pediatric recipients following kidney transplantation (KT). We retrospectively assessed the impact of HTN on long-term (>10-yr) outcomes in pediatric KT recipients (aged < 18 yr) at our center. Two hundred and ninety-three pediatric KT recipients (83% living donor [LD]) with graft survival (GS) for ≥5 yr were studied. HTN was defined by antihypertensive medication use at five yr post-KT. One hundred and sixty (55%) recipients did not have HTN, and 133 (45%) had HTN at five yr post-KT. There were no differences in actuarial patient survival between cohorts. Actuarial GS at 15 and 20 yr was 68% and 53% for recipients without HTN, and 53% and 33% for recipients with HTN (p = 0.006). Among LD recipients using one antihypertensive, GS at 15 yr was 100% for those using an angiotensin-converting enzyme inhibitor (ACEI) and 44% for those not using an ACEI (p = 0.04). Among these recipients, HTN treated with no ACEI was a significant risk factor for graft failure at >5 yr (hazard ratio [HR] = 2.5, p = 0.02), but HTN treated with an ACEI was not (HR = 0.6, p = 0.7). HTN at five yr post-KT is associated with poorer long-term GS in pediatric recipients, but ACEI therapy may enable better outcomes and should be studied further.

TGF-β1 Expression in Kidney Allograft Protocol Biopsies during Cyclosporine: a Therapy

Background

TGF-β1 expression has been described to increase along with time from transplantation and has also been linked to allograft dysfunction and toxic effects of cyclosporine. Our aim was to correlate intragraft TGF-β1 expression with cyclosporine exposure after kidney transplantation.

Methods

Altogether 53 kidney allograft protocol biopsies from 42 patients on a low-dose cyclosporine-based regimen obtained at 3, 6, and 12 months were classified according to Banff and the chronic allograft damage index (CADI). TGF-β1 expression in tubules, glomeruli, vessels, and inflammatory cells was semi-quantitatively scored and correlated with cyclosporine concentrations (C0 and C2), CADI, and graft function.

Results

TGF-β1 expression was mildly increased along time from transplantation, but the results were not statistically significant. TGF-β1 expression was neither related to CADI nor to the use of ACE inhibitors/ARB. TGF-β1 expression in the kidney was not correlated with C0 or C2 levels or kidney graft function during follow-up.

Conclusion

In protocol biopsies from patients on low-dose cyclosporine regimen, expression of TGB-β1 was not significantly increased along time since transplantation, and did not correlate with cyclosporine exposure. Our findings suggest that the toxic effects of low-dose cyclosporine on TGF-β expression may be milder than previously thought.

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.

Progressive histological damage in renal allografts is associated with expression of innate and adaptive immunity genes

The degree of progressive chronic histological damage is associated with long-term renal allograft survival. In order to identify promising molecular targets for timely intervention, we examined renal allograft protocol and indication biopsies from 120 low-risk pediatric and adolescent recipients by whole-genome microarray expression profiling. In data-driven analysis, we found a highly regulated pattern of adaptive and innate immune gene expression that correlated with established or ongoing histological chronic injury, and also with development of future chronic histological damage, even in histologically pristine kidneys. Hence, histologically unrecognized immunological injury at a molecular level sets the stage for the development of chronic tissue injury, while the same molecular response is accentuated during established and worsening chronic allograft damage. Irrespective of the hypothesized immune or nonimmune trigger for chronic allograft injury, a highly orchestrated regulation of innate and adaptive immune responses was found in the graft at the molecular level. This occurred months before histologic lesions appear, and quantitatively below the diagnostic threshold of classic T-cell or antibody-mediated rejection. Thus, measurement of specific immune gene expression in protocol biopsies may be warranted to predict the development of subsequent chronic injury in histologically quiescent grafts and as a means to titrate immunosuppressive therapy.

Factors increasing quantitative interstitial fibrosis from 0 hr to 1 year in living kidney transplant patients receiving tacrolimus

BACKGROUND

This study investigated the increase in interstitial fibrosis (IF) from 0 hr to 1 month and 1 year posttransplantation in biopsy sections and assessed the risk of developing IF in 118 living kidney recipients.

METHODS

A quantitative analysis of IF was performed using computer-assisted imaging. The percent IF (%IF) in the cortical region at 0 hr was defined as the baseline, and the increases in %IF at 1 month and 1 year were calculated. Demographics, higher (regimen 1) and lower (regimen 2) target trough concentrations of tacrolimus, and the cytochrome P450 (CYP) 3A5 polymorphism were tested as risk factors.

RESULTS

The mean %IF at 0 hr, 1 month, and 1 year was 10.3%+/-4.2%, 15.0%+/-5.8%, and 19.0%+/-7.7%, respectively. %IF increased 1.7- and 2.2-fold from 0 hr to 1 month and 1 year posttransplantation, respectively. At 1 year, the increase was higher in patients with the CYP3A5*3/*3 genotype (nonexpressers), those treated with regimen 1, and those with a lower estimated glomerular filtration rate and higher body mass index. In a multivariate analysis, CYP3A5 nonexpression correlated with the development of IF (odds ratio 2.63, P=0.018). Tacrolimus blood levels in the early stage posttransplantation were higher in nonexpressers than CYP3A5 expressers in both regimens 1 and 2, despite therapeutic drug monitoring.

CONCLUSIONS

The higher concentrations of tacrolimus, especially in the nonexpressers treated with regimen 1, might influence the development of IF. This study suggested that a new regimen with lower and narrow target trough levels of tacrolimus or a dosing strategy based on the CYP3A5 genotype is needed to reduce the risk of developing IF.

De novo thrombotic microangiopathy in renal allograft biopsies-role of antibody-mediated rejection

The most common cause of thrombotic microangiopathy (TMA) in renal allografts is thought to be calcineurin inhibitor toxicity. Antibody-mediated rejection (AMR) can also cause TMA, but its true impact on de novo TMA is unknown. In a retrospective review of renal allograft biopsies from January 2003 to December 2008 at our institution, we determined the prevalence of TMA in patients with C4d positive (n = 243) and C4d negative (n = 715) biopsies. Over 90% of patients received cyclosporine in both groups. De novo TMA was seen in 59 (6.1%) patients; most of them (55%) with C4d positive biopsy. Among patients with C4d positive biopsies, 13.6% had TMA, as compared to only 3.6% patients with C4d negative biopsies (p < 0.0001). Incidence of graft loss between C4d positive and C4d negative TMA groups was not significantly different, but 70% of patients with C4d positive TMA who received plasmapheresis had slightly lower graft loss rate. In biopsies with AMR-associated TMA, glomerulitis and peritubular capillaritis were significantly more prominent. AMR is the most common cause of TMA in renal allografts in our patient population. It is important to recognize AMR-related TMA because plasmapheresis treatment may be beneficial.

Molecular pathways involved in loss of graft function in kidney transplant recipients

Interstitial fibrosis (IF) and tubular atrophy (TA) are integral parts of chronic allograft dysfunction and represent in the new classification a separate entity with or without the identification of a specific etiology. Loss of kidney graft function with IF/TA is one of the causes of most kidney allograft losses. Despite progress in immunosuppression, chronic allograft dysfunction remains the main clinical challenge for improving long-term graft survival. The sustained damage to the allograft does not represent a single entity but the summated effects of tissue injury from several pathogenic insults, as well as the kidney's healing response, modified by alloimmunity and immunosuppression. A major challenge in the future of kidney transplantation includes the study of chronic allograft dysfunction pathogenesis to identify early markers of disease progression, as well as potential therapeutics pathways.

A phase III study of belatacept versus cyclosporine in kidney transplants from extended criteria donors (BENEFIT-EXT study)

Recipients of extended criteria donor (ECD) kidneys are at increased risk for graft dysfunction/loss, and may benefit from immunosuppression that avoids calcineurin inhibitor (CNI) nephrotoxicity. Belatacept, a selective costimulation blocker, may preserve renal function and improve long-term outcomes versus CNIs. BENEFIT-EXT (Belatacept Evaluation of Nephroprotection and Efficacy as First-line Immunosuppression Trial-EXTended criteria donors) is a 3-year, Phase III study that assessed a more (MI) or less intensive (LI) regimen of belatacept versus cyclosporine in adult ECD kidney transplant recipients. The co-primary endpoints at 12 months were composite patient/graft survival and a composite renal impairment endpoint. Patient/graft survival with belatacept was similar to cyclosporine (86% MI, 89% LI, 85% cyclosporine) at 12 months. Fewer belatacept patients reached the composite renal impairment endpoint versus cyclosporine (71% MI, 77% LI, 85% cyclosporine; p = 0.002 MI vs. cyclosporine; p = 0.06 LI vs. cyclosporine). The mean measured glomerular filtration rate was 4-7 mL/min higher on belatacept versus cyclosporine (p = 0.008 MI vs. cyclosporine; p = 0.1039 LI vs. cyclosporine), and the overall cardiovascular/metabolic profile was better on belatacept versus cyclosporine. The incidence of acute rejection was similar across groups (18% MI; 18% LI; 14% cyclosporine). Overall rates of infection and malignancy were similar between groups; however, more cases of posttransplant lymphoproliferative disorder (PTLD) occurred in the CNS on belatacept. ECD kidney transplant recipients treated with belatacept-based immunosuppression achieved similar patient/graft survival, better renal function, had an increased incidence of PTLD, and exhibited improvement in the cardiovascular/metabolic risk profile versus cyclosporine-treated patients.

A phase III study of belatacept-based immunosuppression regimens versus cyclosporine in renal transplant recipients (BENEFIT study)

Belatacept, a costimulation blocker, may preserve renal function and improve long-term outcomes versus calcineurin inhibitors in kidney transplantation. This Phase III study (Belatacept Evaluation of Nephroprotection and Efficacy as First-line Immunosuppression Trial) assessed a more intensive (MI) or less intensive (LI) regimen of belatacept versus cyclosporine in adults receiving a kidney transplant from living or standard criteria deceased donors. The co-primary endpoints at 12 months were patient/graft survival, a composite renal impairment endpoint (percent with a measured glomerular filtration rate (mGFR) <60 mL/min/1.73 m(2) at Month 12 or a decrease in mGFR > or =10 mL/min/1.73 m(2) Month 3-Month 12) and the incidence of acute rejection. At Month 12, both belatacept regimens had similar patient/graft survival versus cyclosporine (MI: 95%, LI: 97% and cyclosporine: 93%), and were associated with superior renal function as measured by the composite renal impairment endpoint (MI: 55%; LI: 54% and cyclosporine: 78%; p < or = 0.001 MI or LI versus cyclosporine) and by the mGFR (65, 63 and 50 mL/min for MI, LI and cyclosporine; p < or = 0.001 MI or LI versus cyclosporine). Belatacept patients experienced a higher incidence (MI: 22%, LI: 17% and cyclosporine: 7%) and grade of acute rejection episodes. Safety was generally similar between groups, but posttransplant lymphoproliferative disorder was more common in the belatacept groups. Belatacept was associated with superior renal function and similar patient/graft survival versus cyclosporine at 1 year posttransplant, despite a higher rate of early acute rejection.

Impact of glucose metabolism abnormalities on histopathological changes in kidney transplant protocol biopsies

The impact of post-transplant diabetes (PTDM) on kidney transplant histopathology has been poorly described. We examined the association of glucose metabolism abnormalities on the progression of histopathological changes in serial protocol biopsies. Helsinki University Hospital kidney transplant recipients during 2004-2006 were followed up. Patients with pre-existing diabetes or 2-h oral glucose tolerance test (OGTT) performed at 3 months, and protocol biopsies taken at 0 and 12 months were analyzed (n = 76). Diabetes was defined according to WHO/ADA. Histology was analyzed with chronic allograft damage index (CADI). Altogether 32 patients had pre-existing diabetes. In OGTT at 3 months, four showed PTDM, eight impaired glucose tolerance (IGT), two impaired fasting glucose, and 30 normal glucose tolerance. Patients with impaired glucose metabolism were older (P = 0.005), received grafts from older donors (P = 0.04), and had reduced renal function at 12 months (P = 0.003). In patients with IGT or PTDM, 2-h postload glucose values in OGTT correlated with CADI at 12 months (R = 0.84, P = 0.001) and with the change in CADI score between 0 and 12 months (R = 0.67, P = 0.025). Graft survival was reduced in patients with pre-existing diabetes (P = 0.01). Glucose abnormalities were associated with the progression of histopathological changes, especially in patients with already compromised kidneys, supporting the harmful role of PTDM to the kidney allograft.

CYP3A5 *1 allele associated with tacrolimus trough concentrations but not subclinical acute rejection or chronic allograft nephropathy in Japanese renal transplant recipients

PURPOSE

We assessed reported associations of CYP3A5 *1 allele with a delay in achieving target tacrolimus concentrations, and occurrence of biopsy-confirmed subclinical acute rejection (SAR) and chronic allograft nephropathy (CAN) in Japanese subjects.

METHODS

Forty-one renal allograft recipients were studied. The targeted tacrolimus trough concentrations were 20-25 ng/mL up to 2 weeks post-transplantation, 10-15 ng/mL up to 6 weeks, and 5-10 ng/mL thereafter. At 1 month and 1 year post-transplantation, allograft biopsies were performed.

RESULTS

The CYP3A5 *1/*1 + *1/*3 (expresser) and *3/*3 (nonexpresser) alleles were detected in 19 and 22 patients, respectively. Although the mean trough concentrations were lower in CYP3A5 expressers than nonexpressers for the first 3 weeks, no difference in frequency of SAR among CYP3A5 genotypes was found. The mean trough concentrations were lower from 8 to 12 months post-transplantation, and the frequency of CAN was lower in CYP3A5 expressers.

CONCLUSIONS

In contrast to the previous reports, the CYP3A5 *1 allele was not associated with the frequency of SAR or CAN, suggesting that further studies of different immunosuppressive strategies using tacrolimus are needed to confirm the adequate dosing and concentration of tacrolimus for each CYP3A5 genotype.

Association of cytokine polymorphisms with subclinical progressive chronic allograft nephropathy in Japanese renal transplant recipients: preliminary study

BACKGROUND

The present study calculated the risk of developing subclinical progressive chronic/sclerosing allograft nephropathy (CAN) under tacrolimus-based immunosuppression according to genetic polymorphisms of cytokines and growth factors, and clinical events including delayed graft function (DGF), acute rejection (AR) and cytomegalovirus (CMV) infection.

METHODS

The subjects were 50 recipients with stable graft function more than one year after renal transplantation. The criteria for subclinical progressive CAN were CAN grade 2 or 3 changes on Banff classification and stable serum creatinine (SCr) levels. Ten genetic polymorphisms were assessed.

RESULTS

Eleven patients (22.0%) developed progressive CAN. The mean ages and SCr levels of recipients with and without progressive CAN were 41.2 and 47.1 years, and 1.46 and 1.22 mg/dL, respectively. There were no significant differences in donor age, number of HLA mismatches, DGF or CMV infection. Although the rate of AR episode seemed to be greater in patients with subclinical progressive CAN, the difference did not reach significance (P = 0.093). The frequencies of the interleukin (IL)-2 T-330G TT genotype (P = 0.046) and IL-4 C-590T C allele (P = 0.092) were higher in patients with progressive CAN. In univariate analysis, the presence of IL-2 T-330G TT (OR 4.57, P = 0.044) was associated with CAN development.

CONCLUSION

The presence of IL-2 T-330G TT genotype may be a risk factor for CAN. Further studies with a large number of subjects and analyses of many cytokine polymorphisms would contribute to the ability to make prognostic determinations or tailor immunomodulatory regimens after renal transplantation.

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.

Timing and value of protocol biopsies in well-matched kidney transplant recipients – a clinical and histopathologic analysis

The role and timing of protocol biopsies after kidney transplantation are controversial. We changed our protocol biopsy policy and compared the predictive value of biopsies at different time-points. Protocol biopsies at 6 months (n = 45) were obtained during 2001-2004, and at 3 and 12 months from 2004 (n = 41). Donor biopsy was available from 70 patients. Histopathologic changes were described with chronic allograft damage index (CADI) and Banff 1997. Follow-up was for 18 months. Chronic allograft nephropathy (CAN) was present in 12%, 51%, and 34% and borderline or subclinical rejection in 9.8%, 8.9%, and 7.3% of patients at 3, 6, and 12 months. CAN at 6 and 12 months was associated with reduced graft function (P = 0.001). Semiquantitative CADI scores at all time-points significantly correlated with glomerular filtration rate (GFR) at 18 months. Strongest correlation existed with CADI at 12 months (P < 0.001). Change in CADI between 0-6 and 0-12 months, but not between 0-3 and 3-12 months, correlated with GFR at 18 months (P = 0.03, P = 0.01). Subclinical rejections were rare and chronic changes mild at 3 months. In our well-matched population, the predictive value of a biopsy at 3 months was inferior to biopsies at 6 or 12 months, both of which were effective in predicting long-term graft function.

Mechanisms of chronic allograft dysfunction

This review was designed to highlight new findings that have contributed to our knowledge of the pathogenesis of late graft dysfunction. Both immune and nonimmune causes contribute to its development. Specific contributors to late graft dysfunction have been recently recognized and are potential targets for new treatment options. The variables associated with late graft failure include donor age and tissue quality, brain death and other issues specific to the deceased donor, tissue injury secondary to organ preservation, alloimmune-mediated injury, and posttransplantation factors in the recipient, such as viral infections, hypertension, drug toxicity, and hyperlipidemia. One of the critical variables that is controllable is the total ischemic time; the longer the ischemic episode, the worse the long-term results of the transplant are. Another significant obstacle to long-term allograft survival is the MHC barrier. The roles of B cells and alloantibody as effectors of alloimmunity have been underestimated; emerging studies strongly suggest that previous sensitization and/or de novo donor-anti-human lymphocyte antigen (HLA) antibodies secondary to poor HLA matching portend a poor prognosis for allograft survival, even in the presence of chronic T-cell-specific immunosuppression.