Identification of clinical and histopathologic risk factors for diminished renal function 2 years posttransplant

Ischemia-reperfusion injury in renal transplantation is independent of the immunologic background

BACKGROUND

Adhesion molecule expression is important to early transplant failure. However, whether or not adhesion molecule-facilitated inflammation is antigen-dependent is unknown. We tested this hypothesis.

METHODS

Rat renal grafts were four-hours cold-preserved in University of Wisconsin (UW) solution, transplanted to syngeneic or allogeneic recipients, and harvested after 2, 6, 12, 24, and 48 hours and after 1 week. The first allogeneic group receive no immunosuppression; two additional groups received either low (1.5 mg/kg) or standard (5 mg/kg) cyclosporine A (CsA). Renal function and morphology were determined; frozen sections were immunostained for P-selectin, L-selectin, intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), platelet endothelial cell adhesion molecule-1 (PECAM-1), leukocyte function associated molecule-1 (LFA-1), very late antigen-4 (VLA-4), as well as for neutrophils and monocytes.

RESULTS

Selectins increased rapidly at 2 hours and quickly decreased by 12 hours. While P-selectin was expressed on vasculature, L-selectin was found on inflammatory cells. Neutrophil influx and that of LFA-1-positive cells occurred early, peaked between 12 and 24 hours, and paralleled the maximal impairment in renal function. ICAM-1 and PECAM-1 showed similar kinetics and a diffuse distribution. VCAM-1 increased more slowly after 12 hours, peaked at 24 hours, and was localized predominantly on the endothelium of elastic vessels. Between 24 hours and 1 week, all grafts progressively developed dense VLA-4-positive monocytic infiltrates adjacent to vessels expressing VCAM-1. Functional, morphological, and immunohistochemical parameters did not differ between isografts and allografts at one week. However, by day 10, allografts showed severe vascular and cellular rejection, while injury in isografts resolved. Immunosuppression with CsA did not reverse the inflammation induced by ischemia-reperfusion injury.

CONCLUSIONS

The early inflammation after ischemia-reperfusion injury is largely independent of the immunologic background. We suggest that initial injury prevention should receive the highest priority.

Fibrous intimal thickening at implantation as a risk factor for the outcome of cadaveric renal allografts

BACKGROUND

During the past decade, the donor age of cadaveric renal allografts steadily increased. Because cerebrovascular injury is the main cause of death in this donor population, an increased prevalence of atherosclerotic lesions in the retrieved grafts could be anticipated. In a prospective study, we investigated the predictive value of morphologic lesions at implantation for the functional and morphologic outcome of cadaveric renal allografts at 1 1/2 years.

METHODS

In 50 consecutive adult recipients of a cadaveric renal allograft, under cyclosporine-based regimen, implantation biopsies and subsequent protocol biopsies at 18 months were performed, and morphometrically analyzed for the extent of glomerulosclerosis, interstitial fibrosis, and atherosclerosis. Risk factors were assessed at implantation and during the subsequent observation period of 18 months. Endpoints for this study were: the 24-hr creatinine clearance (normalized for body surface area) and the fractional interstitial volume at 1 1/2 years.

RESULTS

In multivariate analysis, fibrous intimal thickening at implantation (FIT) was the main determinant of the functional and morphologic outcome at 1 1/2 years. FIT represented a relative risk of 4.55 for interstitial fibrosis (95% CI=1.855-11.138), and 1.89 for impaired renal function (95% CI=1.185-3.007) at 1 1/2 years. FIT adversely affected fractional interstitial volume at 1 1/2 years (34.3 vs. 27.7%, P=0.004), as well as renal function (54 vs. 68 ml/min/1.73 m2, P=0.028).

CONCLUSIONS

Fibrous intimal thickening at implantation is a determinant risk factor for the functional and morphologic outcome of cadaveric renal allografts at 1 1/2 years.

Ischemic acute renal failure: long-term histology of cell and matrix changes in the rat

BACKGROUND

The cellular infiltration and matrix accumulation accompanying acute renal ischemia and reperfusion have been frequently noted but poorly defined. The long-term consequences of ischemia may irreversibly damage the kidney.

METHODS

Female Sprague-Dawley rats (200 g) underwent unilateral nephrectomy. After five days, the left renal pedicle was occluded for 45 minutes. Animals were sacrificed at 0, 1, 2, 4, 8, 16, 32, 64, and 180 days postischemia (N = 6). Immunohistochemistry for monocytes/macrophages (Mo/Mphi, ED-1), myofibroblasts [alpha-smooth muscle actin (alpha-SMA)], collagen III and IV, matrix metalloproteinase-2 (MMP-2) and proliferating cell nuclear antigen (PCNA) and terminal dUTP nick end labeling (TUNEL) were performed.

RESULTS

Kidney weights of postischemic animals were increased at all time points (postischemic to controls, 1.47 +/- 0.21 to 0.94 +/- 0.12 g at day 8; 1.49 +/- 0.20 to 1.27 +/- 0.13 g at day 64; and 1.86 +/- 0.1 to 1. 24 +/- 0.2 g at day 180). Serum creatinine values increased to 0.42 +/- 0.10 mmol/L at day 2 but returned to control levels by day 8 (0. 05 mmol/L). Glomerular collagen IV was decreased from 2 to 16 days postischemia, which was accompanied by an increase in MMP-2. The fractional area of the interstitium was greatest at day 8 (19.55 +/- 0.91% compared with day 0 at 8.08 +/- 0.27%), with a second increase observed at day 180 (16.61 +/- 0.70%). Interstitial Mo/Mphi increased postischemia from days 2 through 8 (8.84 +/- 2.12 to 133. 32 +/- 14.04 per 0.91 mm2) and then decreased. Myofibroblasts proliferated locally (PCNA double labeling was demonstrated), and increased numbers were found from days 2 through 16 (maximal at day 8, 26.96 +/- 3.04%, compared with day 0, 0.88 +/- 0.11%). In the postischemic groups, collagen IV increased to day 8 (20.84 +/- 1. 30%), but then decreased to below control values at day 64 (2.22 +/- 0.15%) before returning to normal by day 180. Interstitial collagen III increased to 8 days (0.45 +/- 0.07% to 2.55 +/- 0.36%) and then decreased to control levels by day 32, but showed a marked increase to approximately 6% at days 64 and 180. Cellular proliferation (PCNA) was maximal at days 2 and 4 (affecting tubule cells and myofibroblasts but not macrophages). Apoptosis was maximal at day 8 (in both interstitial and tubule cells) in the postischemic groups.

CONCLUSION

Marked changes in the accumulation of Mo/Mphi, MF, and collagen IV were found in this model of ischemic acute renal failure. The reversibility of functional and structural changes is in marked contrast to that found in progressive disease. The increases observed for collagen III at 64 and 180 days postischemia suggest that in the long term, however, further chronic structural changes may be observed.

Protocol renal allograft biopsies and the design of clinical trials aimed to prevent or treat chronic allograft nephropathy

BACKGROUND

The minimum sample size to perform a clinical trial aimed to modify the natural history of chronic allograft nephropathy (CAN) is very large. Since the presence of chronic tubulointerstitial damage in renal protocol biopsy specimens is an independent predictor of late outcome, we evaluated whether protocol biopsies could facilitate the design of trials aimed to prevent or treat CAN.

METHODS

Two hundred eighty-two protocol biopsy specimens were obtained 3 months after transplantation in 280 patients with serum creatinine levels <300 micromol/L, proteinuria <1000 mg/day, and stable function. The specimens were evaluated according to the Banff criteria.

RESULTS

Graft survival depended on the presence of CAN and renal transplant vasculopathy (RTV). Thus, biopsy specimens were classified as: (a) no CAN (n=174); (b) CAN without RTV (n=87); and (c) CAN with RTV (n=21). Graft survival at 10 years was 95%, 82%, and 41%, respectively (P=0.001). Total serum cholesterol before transplantation was 4.5+/-1.1, 4.6+/-1.1, and 5.3+/-1.6 mmol/L, respectively (P=0.009) and it was the only predictor of RTV. Power analysis (beta=20%, alpha=5%) was done to evaluate whether protocol biopsies can facilitate the design of clinical trials aimed either to prevent or treat CAN. We showed that the most feasible approach would be to use the presence of CAN as the primary efficacy end point in a prevention trial. To demonstrate a 50% reduction in the incidence of CAN at 3 months, 570 patients would be required.

CONCLUSIONS

Protocol biopsies may allow a reduction of sample size and especially the time of follow-up in a trial aimed to prevent CAN.

Impact of acute rejection on development of chronic rejection in pediatric renal transplant recipients

For pediatric kidney transplant recipients, chronic rejection has become the predominant cause of graft loss. This article reviews risk factors for chronic rejection and what can be done to lower the risk of chronic rejection for future transplant recipients.

Impact of the Banff '97 classification for histological diagnosis of rejection on clinical outcome and renal function parameters after kidney transplantation

BACKGROUND

Data on a systematic correlation of specific pathomorphologic lesions in renal allograft biopsy specimens with clinical outcome parameters are crucial to determine the relevance of kidney biopsy findings after transplantation for graft prognosis. Specific histologic lesions of the revised Banff '97 classification were correlated with clinical follow-up data.

METHODS

The analysis was done on a series of 48 consecutive renal allograft biopsy specimens. Logistic regression was used to compare for response to rejection treatment dependent on histologic grading. Cox regression was applied to analyze the impact of the histologic findings on graft failure during ongoing follow-up.

RESULTS

Severity of acute rejection was statistically associated with unresponsiveness to antirejection treatment (odds ratio 2.39, 95% confidence interval 1.13-5.03) and predicted an increased risk of graft failure (hazard ratio 2.16, 95% confidence interval 1.48-3.14). Intimal arteritis (hazard ratio 1.85, 95% confidence interval 1.40-2.45) was the only determinate of a poor survival prognosis. Mean serum creatinine level and the need for antihypertensive drugs were significantly higher in the Banff I-III graded groups after 1 and 2 years of follow-up, whereas patients with borderline rejection were not significantly different from the control group.

CONCLUSION

We confirmed a significant association between the revised Banff '97 classification and graft outcome. Intimal arteritis was the only significant predictor of a poor survival probability. The distinction of borderline rejection and Banff grade I rejection seems to be important from a prognostic point of view.

Increased levels of GALbeta1-4GLCNACalpha2-6 sialyltransferase pretransplant predict delayed graft function in kidney transplant recipients

BACKGROUND

Galbeta1-4GlcNAcalpha2-6 sialyltransferase (ST6GalI) is an acute phase reactant whose release from cells can be induced by proinflammatory cytokines. Because patients with chronic renal failure have high circulating levels of proinflammatory cytokines, we hypothesized that patients on the renal transplant waiting list would have high circulating levels of ST6GalI, which might adversely affect post-transplant events.

METHODS

Levels of ST6GalI were measured in the serum of 70 patients immediately before renal transplant; these were correlated with posttransplant events, such as delayed graft function and rejection.

RESULTS

The mean serum level of ST6GalI was significantly higher in the patients (3162+/-97 U) than in 19 controls (2569 +/- 125 U; P<0.003). Patients who required dialysis posttransplant for treatment of delayed graft function (n=20) had significantly higher levels of ST6GalI pretransplant (3735+/-228 U) than patients (n=50) who did not require dialysis (2933+/-83 U; P<0.0001). In a multivariate analysis the ST6GalI level and cold ischemic time were found to be independent risk factors for the development of delayed graft function.

CONCLUSIONS

ST6GalI levels are high in renal failure patients awaiting a renal transplant and may be a risk factor for the development of delayed graft function. The assessment and perhaps modulation of a potential transplant recipient's ST6GalI systemic level may be beneficial.

Telomere shortening in kidneys with age

The histology and function of the kidney deteriorates with age and age-related diseases, but the mechanisms involved in renal aging are not known. In vitro studies suggest that telomere shortening is important in replicative senescence, and is accelerated by stresses that increase replication. This study explored the relationship between age and telomere length in surgical samples from 24 human kidneys, which were either histologically normal (17) or displayed histologic abnormalities (7). Telomere loss was assessed by two independent methods: Southern blotting of terminal restriction fragments (TRF) and slot blotting using telomere-specific probes. The results of these methods correlated with each other. The mean TRF length determined by Southern blotting in cortex was about 12 kb pairs (kbp) in infancy and was shorter in older kidneys. The slope of the regression line was about 0.029 kbp (0.24%, P = 0.023) per year. Telomere DNA loss in cortex by the slot blot method was 0.25% per year (P = 0.011). By both methods, the telomere loss in medulla was not significant and was less than in cortex. Comparisons of TRF length from 20 paired samples from cortex and medulla showed that TRF was greater in cortex than medulla, with the differences being greater in young kidneys and lessening with age due to telomere loss in cortex. These findings indicate that telomeres shorten in an age-dependent manner in the kidney, either due to developmental factors or aging, particularly in renal cortex.

Renal allograft rejection with normal renal function in simultaneous kidney/pancreas recipients: does dissynchronous rejection really exist?

BACKGROUND

Between July 1, 1994 and December 1, 1998, 147 simultaneous kidney/pancreas transplantations were performed at our center. Of 95 patients who experienced at least one acute renal allograft rejection episode after transplantation, 7 (7.4%) developed rejection in the presence of stable and normal or near-normal renal function.

METHODS

The indication for renal allograft biopsy was a rising serum lipase, i.e., suspected pancreatic rejection. All seven patients were treated with steroids and augmentation of the tacrolimus dose, with a fall in the serum lipase and no change in the serum creatinine.

RESULTS

The serum creatinine levels just before, at the time of, 1 week after the biopsy, and at most recent follow-up were 1.4+/-0.4, 1.3+/-0.3, 1.2+/-0.2, and 1.2+/-0.2 mg/dl. The serum lipase levels just before, at the time of, 1 week after the biopsy, and at most recent follow-up were 1022+/-1157 mg/dl, 874+/-996 mg/dl, 243+/-260 mg/dl, and 94+/-75 mg/dl. The tacrolimus dosages and levels at the time of the biopsy and 1 week later were 14.9+/-5.0 mg/day and 15.0+/-4.0 ng/ml, and 16.4+/-6.3 mg/day and 15.1+/-6.8 ng/ml.

CONCLUSIONS

These findings suggest that, in patients undergoing simultaneous kidney/pancreas transplantation, the entity of dissynchronous pancreatic allograft rejection without renal allograft rejection may not really exist. These data also make an additional fundamental point that acute rejection may occur in patients with normal and stable renal function.

Does subclinical rejection contribute to chronic rejection in renal transplant patients?

Renal allograft biopsies have traditionally been performed in the setting of acute graft dysfunction. However, several groups have performed graft biopsies at times of stable graft function, and more recently, after treatment of rejection episodes. Surprisingly, unequivocal histologic criteria for acute rejection have been demonstrated in a high proportion of these protocol biopsies. The Winnipeg Transplant Group has documented the high prevalence of clinically silent inflammatory infiltrates in early protocol biopsies, and demonstrated their inflammatory and cytotoxic potential by immunohistochemical and molecular biological techniques. Furthermore, in a randomized trial, our group has demonstrated that subclinical rejection, if untreated, is associated with the development of early chronic pathology and late graft dysfunction. In this overview, we will summarize the early data on subclinical allograft inflammation, present the experience of the Winnipeg Transplant Group, and discuss the possible implications of subclinical rejection on the development of chronic rejection.

Quantitation of allograft fibrosis and chronic allograft nephropathy

Despite improvements in the prevention and treatment of acute renal allograft rejection, the long-term survival of renal transplants has not increased. Immunologic and non-immunologic factors contribute to the gradual deterioration of graft function and to the histologic lesion characterized by vascular and interstitial fibrosis ('chronic rejection'). Quantitation of this process has been attempted using various invasive and non-invasive methods. These methods, performed at different times post-transplant, are reviewed in this article. In particular, pathology scoring systems and the potential of using computerized image analysis of biopsy material are discussed.

Inhibition of NFkappaB activation with antioxidants is correlated with reduced cytokine transcription in PTC

We recently reported that inhibition of the transcription factor nuclear factor-kappaB (NFkappaB) with pyrrolidinedithiocarbamate (PDTC) reduced interstitial monocyte infiltration in rats with proteinuric tubulointerstitial disease, whereas N-acetylcysteine (NAC) was not effective. Here we investigate the effects of antioxidants (PDTC, NAC, and quercetin) on NFkappaB activation and cytokine transcription in primary cultured rat proximal tubular epithelial cells (PTC) stimulated with lipopolysaccharide. Antioxidant-mediated inhibition of NFkappaB activation (PDTC, 20-100 microM; NAC, 100 mM; and quercetin, 50 microM) diminished the induction of both pro- [interleukin (IL)-1beta, tumor necrosis factor-alpha, monocyte chemoattractant protein-1, macrophage inflammatory protein (MIP)-1alpha, and MIP-2] and anti-inflammatory (IL-10, transforming growth factor-beta1) cytokine transcription in PTC (RT-PCR analysis). PDTC and quercetin did not affect PTC viability, but NAC (100 mM) caused a threefold increase in lactate dehydrogenase leakage (P < 0.001). We conclude that NAC is unable to suppress NFkappaB activation in PTC at subtoxic and physiologically relevant concentrations. Furthermore, antioxidant-mediated inhibition of NFkappaB is correlated with the nonselective reduction of cytokine transcription in activated tubular cells. These data might explain the protective effects of PDTC-mediated NFkappaB inhibition in tubulointerstitial disease in vivo.

Decreased acute rejection in kidney transplant recipients is associated with decreased chronic rejection

OBJECTIVE

To determine whether a recent decrease in the rate of acute rejection after kidney transplantation was associated with a decrease in the rate of chronic rejection.

SUMMARY BACKGROUND DATA

Single-institution and multicenter retrospective analyses have identified acute rejection episodes as the major risk factor for chronic rejection after kidney transplantation. However, to date, no study has shown that a decrease in the rate of acute rejection leads to a decrease in the rate of chronic rejection.

METHODS

The authors studied patient populations who underwent transplants at a single center during two eras (1984-1987 and 1991-1994) to determine the rate of biopsy-proven acute rejection, the rate of biopsy-proven chronic rejection, and the graft half-life.

RESULTS

Recipients who underwent transplantation in era 2 had a decreased rate of biopsy-proven acute rejection compared with era 1 (p < 0.05). This decrease was associated with a decreased rate of biopsy-proven chronic rejection for both cadaver (p = 0.0001) and living donor (p = 0.08) recipients. A trend was observed toward increased graft half-life in era 2 (p = NS).

CONCLUSIONS

Development of immunosuppressive protocols that decrease the rate of acute rejection should lower the rate of chronic rejection and improve long-term graft survival.

An evaluation of the Banff classification of early renal allograft biopsies and correlation with outcome

BACKGROUND

The Banff classification for assessment of renal allograft biopsies was introduced as a standardized international classification of renal allograft pathology and acute rejection. Subsequent debate and evaluation studies have attempted to develop and refine the classification. A recent alternative classification, known as the National Institutes of Health Collaborative Clinical Trials in Transplantation (NIH-CCTT) classification, proposed three distinct types of acute rejection. The 1997 Fourth Banff meeting appeared to move towards a consensus for describing transplant biopsies, which incorporated both approaches. Patients who received a renal allograft at the Oxford Transplant Centre were managed by a combination of protocol and clinically indicated biopsies. We have undertaken a retrospective analysis of the biopsies correlated with the clinical outcome to test the prognostic value of the original Banff (Banff 93-95) and NIH-CCTT classifications.

METHODS

Three hundred and eighty-two patients received renal allografts between May 1985 and December 1989, and were immunosuppressed using a standard protocol of cyclosporine, azathioprine and steroid. Adequate 5-year follow-up data were available on 351 patients, and of these, 293 had at least one satisfactory biopsy taken between days 2 and 35 after transplantation, the latter patients forming the study group. The D2-35 biopsies taken from these patients, which were not originally reported according to the Banff classification, were re-examined and classified according to the Banff 93-95 protocols. For each patient the biopsy found to be the most severely abnormal was selected, and the Banff and NIH-CCTT grading compared with the clinical outcome.

RESULTS

Seven hundred and forty-three biopsies taken from 293 patients between days 2 and 35 after transplantation were examined and the patients categorized on the basis of the 'worst' Banff grading as follows. Normal or non-rejection, 20%; borderline, 34%; acute rejection grade I (AR I), 18%; AR IIA, 6%; AR IIB, 14%; AR III, 1%; AR IIIC, 3%; widespread necrosis 3%. The clinical outcome for the last two groups combined was very poor with 18% of grafts functioning at 3 months and 6% at 5 years. The other groups with vascular rejection (AR IIB and AR III) had an intermediate outcome, graft survival being 78% at 3 months and 61% at 5 years. The remaining four groups (normal, borderline, cellular AR I and AR IIA) had the best outcome: graft survival 95% at 3 months and 78% at 5 years with virtually no difference between the four groups. Three forms of acute rejection, namely tubulo-interstitial, vascular and transmural vascular, were identified, but only the latter two categories were associated with a poor outcome.

CONCLUSIONS

The eight sub-categories of the Banff classification of renal allograft biopsies are associated with three different prognoses with respect to graft survival in the medium term. These three prognostic groups correspond to the three NIH-CCTT types. The data provide support for the consensus developed at Banff 97 separating tubulo-interstitial, vascular and transmural vascular rejection (types I, II and III acute rejection).

Living donor kidney transplants: a biopsy study 1 year after transplantation, compared with baseline changes and correlation to kidney function at 1 and 3 years

INTRODUCTION

Chronic changes in biopsies from long-term stable kidney allografts have been reported to correlate with graft prognosis. Morphological changes in baseline ('zero-hour') biopsies have been described as well, but their importance for long-term prognosis have been less clear. The aim of the present study was to evaluate biopsy changes from baseline to 1 year after transplantation in patients receiving kidneys from living donors, and to assess the possible prognostic implications of these findings.

METHODS

Light microscopical changes in 18 gauge full-core biopsies were scored semi-quantitatively in 33 patients 1 year after transplantation, and compared to baseline changes previously reported [1]. All cases were also examined with transmission electron microscopy. The semi-quantitative data from baseline and at 1 year were correlated with kidney function 1 and 3 years after transplantation. The reproducibility of baseline findings regarding arteriosclerosis and arteriolar hyalinosis was tested by comparison with biopsies 1 week after transplantation (n = 43).

RESULTS

We found a significant increase in mesangial glomerular sclerosis (P<0.001), interstitial fibrosis/tubular atrophy (if/ta) (P = 0.002), and mononuclear cell interstitial infiltration (P = 0.003) after 1 year, compared to baseline changes. There was an increase of arteriosclerosis (P = 0.028) and arteriolar hyalinosis (P = 0.006) when compared to biopsies taken 1 week after transplantation, but not when compared to the 'zero-hour' findings. Electron microscopy revealed one case of recurrent immune-complex glomerulonephritis and another case of recurrent light chain deposition kidney disease. Comparing 1-week vascular findings with baseline gave a low level of reproducibility, probably due to sampling error. Baseline biopsy findings could not predict long-term kidney function. In the 1-year biopsy, if/ta was significantly correlated with serum creatinine (P = 0.007) and glomerular filtration rate (GFR) (P<0.001) at 1 year, with serum creatinine at 3 years (P = 0.011), and with the first-year cumulative dose of methylprednisolone (P = 0.004). Serum creatinine at 1 year, however, was found to be the most accurate predictor of 3-year kidney function (P<0.001). Donor age was correlated to kidney function at 3 years (P = 0.013) but not at 1 year after transplantation.

CONCLUSION

Morphological changes in baseline biopsies of living donor kidneys tend to become more pronounced in well-functioning allografts during the first year after transplantation. In the 1 year biopsy, if/ta seems to be the most reliable variate for grading of chronic changes. However, 1-year serum creatinine predicted long-term kidney function more precisely than did the biopsy scores. Based on the results of the present study, a protocol 1-year biopsy does not seem warranted in the management of the graft recipient with a stable kidney function.

Transforming growth factor-beta levels in human allograft chronic fibrosis correlate with rate of decline in renal function

BACKGROUND

Long-term renal transplant function is limited primarily by a progressive scarring process loosely termed "chronic rejection, chronic allograft nephropathy, or allograft fibrosis." Although the etiology of transplant fibrosis is uncertain, several possible factors including chronic cyclosporin A (CsA) exposure may contribute to its pathogenesis. CsA stimulates renal fibrosis perhaps through the induction of the potent pro-sclerotic growth factor, transforming growth factor beta (TGFbeta). Previously, we demonstrated that, in human transplant biopsies, acute CsA toxicity but not acute tubular necrosis is associated with elevated levels of renal TGFbeta protein. We now examine whether long-term CsA treatment (>1 year) is associated with elevated levels of intra-allograft TGFbeta and whether heightened expression of TGFbeta is clinically significant.

METHODS

Using immunohistochemical techniques, we determined the relative level of expression of intrarenal TGFbeta protein in transplant biopsies. We studied biopsies obtained from 40 CsA-treated patients that were diagnosed as having chronic allograft fibrosis. Biopsies were scored as having minimal or high levels of TGFbeta.

RESULTS

Seventy-two percent of patients expressed high levels of intra-allograft TGFbeta. This group of patients lost renal function at an average rate of -19.5+/-17.3 ml/min/year. In contrast, patients with minimal or no TGFbeta expression experienced a decline of only -6.2+/-4.1 ml/min/year (P=0.01).

CONCLUSIONS

These results suggest that the majority of CsA-treated patients with biopsy proven chronic fibrosis have elevated levels of intra-graft TGFbeta that correlates with an increased rate of decline in renal function.

Effect of increasing baseline immunosuppression on the prevalence of clinical and subclinical rejection: a pilot study

This group has reported that treatment of subclinical rejection in the first 3 mo posttransplant with corticosteroids decreases late clinical rejections and improves graft function at 2 yr in renal transplant recipients. The current study was performed to determine whether an increase in baseline immunosuppression would decrease the prevalence of early subclinical rejections, as well as the incidence of early and late clinical rejections. Patients received mycophenolate mofetil (MMF) and Neoral cyclosporin A (CsA) posttransplant (n = 29), of which 17 underwent protocol biopsies at months 1, 2, 3, and 6 (Neoral + MMF Protocol Biopsy [Bx]), while 12 declined protocol biopsies (Neoral + MMF Control). These individuals were compared with 72 historical control patients treated with Sandimmune CsA and Imuran, of which 36 had undergone protocol biopsies at months 1, 2, 3, and 6 (Sandimmune + Azathioprine [AZA] Protocol Bx), and 36 had a protocol biopsy at month 6 (Sandimmune + AZA Control). Baseline immunosuppression with Neoral + MMF decreased the incidence of early clinical rejections (0 to 3 mo) and cumulative corticosteroid exposure, but had no impact on the prevalence of early subclinical rejection. Moreover, to maximally decrease the risk of developing late clinical rejections (months 7 to 12) in Neoral + MMF patients required that protocol biopsies be done and that subclinical rejection be treated. The paradoxical finding of recent clinical trials that a reduction in acute clinical rejection has not improved long-term graft outcome may be explained in part by the failure to control subclinical rejection.

Clinical rejection is distinguished from subclinical rejection by increased infiltration by a population of activated macrophages

It has been reported previously that one-third of protocol renal biopsies in asymptomatic, biochemically stable renal transplant recipients in the first 6 mo show unsuspected subclinical graft rejection (both infiltrate and tubulitis) and that subclinical rejection is a risk factor for chronic renal dysfunction. This study was performed to determine whether differences in phenotype or activation status of graft-infiltrating cells underlie these different manifestations of acute rejection. Biopsies with normal histology (n = 10), subclinical rejection (n = 13), and clinical rejection (n = 9) were studied using immunohistochemistry and computerized image analysis. Subclinical and clinical rejections had similar histologic Banff scores. Univariate analysis showed a trend for a higher infiltration with CD8+ (P = 0.053) and CD68+(P = 0.06) cells in clinical rejection. Of the activation markers studied (CD25, perforin, tumor necrosis factor-alpha), only allograft inflammatory factor-1+-activated macrophages were significantly (P = 0.014) increased in the infiltrate of clinical rejection biopsies. These data suggest that activated macrophages or their products are responsible for acute renal dysfunction associated with clinical rejection episodes.

Predictors of renal transplant histology at three months

BACKGROUND

The quality of a damaged kidney, the complexity of the surgery, and the events in the first weeks after transplantation, such as delayed graft function (DGF) and acute rejection, may influence its histological appearance and long-term survival. The aim of this study was to evaluate the importance of these factors in predicting renal allograft histology at 3 months.

METHODS

Prospective, protocol kidney biopsy specimens (n=112), obtained 3 months after transplantation, were scored for chronic damage by the Banff schema and evaluated by multivariate analysis against donor factors, implantation histology, prior recipient sensitization, ischemia, perioperative factors, and subsequent clinical events, such as DGF and acute rejection.

RESULTS

Adequate samples were obtained in 102 of 112 biopsies and classified as chronic Banff grade 0 (n=22), grade I (n=56), grade II (n=23), or grade III (n=1). Acute Banff scores were minimal. DGF occurred in 49% and was the strongest predictor of tubulointerstitial damage at 3 months. DGF correlated with acute tubular necrosis on the implantation biopsy specimen and with the number of acute rejection episodes; DGF also correlated with the Banff grades of chronic glomerulitis, chronic interstitial fibrosis, and tubular atrophy scores (P<0.05-0.001) in the 3-month biopsy specimen. By multivariate analysis, chronic tubular atrophy was independently predicted by the presence of vascular disease in the donor biopsy specimen, DGF, and vascular rejection occurring within the first 3 months (P<0.05-0.001). Chronic interstitial fibrosis was unrelated to fibrosis in the donor biopsy specimen but was independently predicted by DGF, donor age, and vascular rejection (P<0.05-0.001). Vascular disease in the donor biopsy specimen correlated with chronic intimal thickening (r=0.36, P<0.01) and arteriolar hyalinosis score (r=0.54, P<0.001) on the 3-month biopsy specimen. Banff chronic intimal vascular thickening was independently predicted by donor biopsy specimen vascular grade, prior vascular rejection episodes, and renal cold ischemia time (P<0.05-0.01). There were no correlates with the mean cyclosporine (CsA) dose, blood levels, diagnosis of CsA toxicity, or cellular rejection within the first 3 months.

CONCLUSIONS

This study has demonstrated that the quality of the donor organ at implantation was strongly predictive of subsequent renal histology in grafts functioning at 3 months. Vascular rejection and DGF had a significant long-term effect on graft damage, but cellular rejection and simple measures of CsA exposure did not.

The Banff 97 working classification of renal allograft pathology

BACKGROUND

Standardization of renal allograft biopsy interpretation is necessary to guide therapy and to establish an objective end point for clinical trials. This manuscript describes a classification, Banff 97, developed by investigators using the Banff Schema and the Collaborative Clinical Trials in Transplantation (CCTT) modification for diagnosis of renal allograft pathology.

METHODS

Banff 97 grew from an international consensus discussion begun at Banff and continued via the Internet. This schema developed from (a) analysis of data using the Banff classification, (b) publication of and experience with the CCTT modification, (c) international conferences, and (d) data from recent studies on impact of vasculitis on transplant outcome.

RESULTS

Semiquantitative lesion scoring continues to focus on tubulitis and arteritis but includes a minimum threshold for interstitial inflammation. Banff 97 defines "types" of acute/active rejection. Type I is tubulointerstitial rejection without arteritis. Type II is vascular rejection with intimal arteritis, and type III is severe rejection with transmural arterial changes. Biopsies with only mild inflammation are graded as "borderline/suspicious for rejection." Chronic/sclerosing allograft changes are graded based on severity of tubular atrophy and interstitial fibrosis. Antibody-mediated rejection, hyperacute or accelerated acute in presentation, is also categorized, as are other significant allograft findings.

CONCLUSIONS

The Banff 97 working classification refines earlier schemas and represents input from two classifications most widely used in clinical rejection trials and in clinical practice worldwide. Major changes include the following: rejection with vasculitis is separated from tubulointerstitial rejection; severe rejection requires transmural changes in arteries; "borderline" rejection can only be interpreted in a clinical context; antibody-mediated rejection is further defined, and lesion scoring focuses on most severely involved structures. Criteria for specimen adequacy have also been modified. Banff 97 represents a significant refinement of allograft assessment, developed via international consensus discussions.

Immune-activation gene expression in clinically stable renal allograft biopsies: molecular evidence for subclinical rejection

BACKGROUND

A significant percentage of biopsies from stable, well-functioning renal allografts have histologic findings consistent with acute rejection or borderline rejection. The implication of this finding is not yet fully understood. We analyzed immune-activation gene transcripts in stable protocol biopsies to determine the extent of immunologic activity of graft-infiltrating cells in this setting. Histologic classification of the biopsies was based on the Banff criteria. To emphasize that the tissue samples were procured from grafts with no clinical evidence of impaired function, we interjected the term "subclinical" into the Banff terminology. This produced three histologic categories: normal, borderline subclinical rejection, and acute subclinical rejection.

METHODS

We used competitive template polymerase chain reaction techniques to quantify transcript amounts for the constant region of the T-cell receptor beta chain; the cytokines, tumor necrosis factor alpha, interleukin (IL)-1beta, transforming growth factor beta, interferon gamma, IL-2, IL-4, IL-10, and IL-15; and the cytotoxic T lymphocyte effector molecules, granzyme B, perforin, and Fas ligand.

RESULTS

We found that histologically normal biopsies were typically devoid of gene transcripts or had very low amounts. Conversely, biopsies with acute subclinical rejection by histologic examination had heightened amounts of transcripts for many of the genes assayed. Borderline subclinical rejection samples showed an intermediate amount of expression.

CONCLUSIONS

These results demonstrate that histologic features of rejection are often accompanied by enhanced expression of pro-inflammatory gene transcripts, despite the absence of clinically overt graft dysfunction. As this state of subclinical rejection could prove detrimental to long-term graft function, a role for surveillance biopsies of stable grafts with intent to treat subclinical rejection should be considered.

Protocol biopsies in renal transplantation: research tool or clinically useful?

Early protocol biopsies of stable, well functioning renal allografts reveal a high prevalence of clinically unsuspected acute and chronic pathology. It is becoming increasingly apparent that these histopathological findings are both pathogenic and predictive of long-term allograft outcome. Therefore, protocol biopsies may be required for optimal post-transplant surveillance until non-invasive methods to detect allograft inflammation are developed.

Cyclosporin nephrotoxicity: pathophysiology and comparison with FK-506

At the end of an era of almost exclusive use of cyclosporin A, there have been significant advances in the understanding of its immunosuppressive effects, whereas there is still uncertainty about the mechanisms underlying its nephrotoxicity. The recently introduced FK-506, in spite of its undeniable clinical advantages, has subsequently been proved to have rather similar nephrotoxicity. This paper reviews recent data on cyclosporin A and FK-506 nephrotoxicity, with emphasis on: first, the haemodynamic, functional and structural features; second, the potential mediators; and third, the relationship with some immunosuppressive mechanisms involved to give insights into the pathophysiology.

Matching for private or public HLA epitopes reduces acute rejection episodes and improves two-year renal allograft function

BACKGROUND

The current role of HLA matching in renal transplantation is controversial. Public HLA epitope matching has been suggested to be as advantageous as private HLA matching, with the added benefit of increasing recipients' access to well-matched grafts.

METHODS

In this single-center study of 105 renal transplant recipients, we examined the association of HLA matching with early (0-3 months) and late (4-6 months) rejection episodes (RE), as well as renal allograft function up to 2 years after transplant.

RESULTS

Poor HLA-DR, but not HLA-A or -B, matching was associated with early RE (0 DR matches, RE=2.7+/-0.19, 1 DR match, RE=2.37+/-0.18, vs. 2 DR matches, RE=1.5+/-0.38; P < 0.01). In contrast, poor HLA-B, but not HLA-A or -DR, matching was associated with late rejections (0 HLA-B matches, RE=1.1+/-0.51 vs. 1-2 HLA-B matches, RE=0.51+/-0.1; P < 0.004). HLA-B matching was also associated with a significantly lower serum creatinine (SCr) level at 24 months (0 HLA-B matches, SCr=178+/-20 micromol/L vs. SCr=132+/-6 micromol/L for 1-2 HLA-B matches; P < 0.025). Matching for 10 supertypic HLA-A and -B cross-reactive groups was associated with reduced late graft rejection (0-2 residue matches, RE=1.15+/-0.18 vs. RE=0.62+/-0.12 for 3 to 7 residue matches; P < 0.013) as well as a significantly lower SCr level at 24 months (0-2 residue matches, SCr=205+/-29 micromol/L vs SCr=131+/-6 micromol/L for 3 to 7 residue matches; P < 0.001) after transplantation.

CONCLUSIONS

HLA-DR matching was associated with a reduced frequency of early rejection episodes, whereas HLA-B or residue/cross-reactive group matching was associated with a reduced frequency of late rejection episodes and improved graft function at 2 years.