Predictors of renal transplant histology at three months

Comparison of Low Versus High Tacrolimus Levels in Kidney Transplantation: Assessment of Efficacy by Protocol Biopsies

BACKGROUND

The use of calcineurin inhibitors is generally guided by drug blood levels. However, those levels are chosen based on clinical experience, lacking adequate titration studies.

METHODS

In these analyses, we compared clinical and histologic endpoints in two groups of kidney transplant recipients: in the first (HiTAC, January 2000 to June 2002, n=245) tacrolimus levels were significantly higher than in the second (LoTAC, July 2002 to September 2004, n=330). This change in drug levels (15% reduction) was made in an attempt to reduce the incidence of polyoma virus nephropathy (PVAN). Other immunosuppressive medications were unchanged during these two time periods.

RESULTS

The recipient and donor demographics were not statistically different between the two groups. Compared to HiTAC, at one year posttransplant LoTAC had: 1) lower incidence of PVAN (10.5% vs. 2.5%, P<0.0001); 2) lower fasting glucose levels; 3) higher iothalamate glomerular filtration rate (52+/-19 vs. 59+/-17 ml/min/m, P<0.0001); and 4) on protocol one-year biopsies, lower incidence and severity of interstitial fibrosis (67% vs. 45%, P=0.003) and tubular atrophy (82% vs., 66%, P=0.01). The incidence and severity of acute rejection episodes was similar between both groups (7.8% versus 7.6%).

CONCLUSIONS

Modest reductions in tacrolimus exposure early posttransplant are associated with significant beneficial effects for the patient and the allograft without an increased immunologic risk.

Chronic cardiac transplant arteriopathy in mice: relationship of alloantibody, C4d deposition and neointimal fibrosis

Murine heterotopic cardiac allografts were used to reveal some of the fundamental interrelationships between donor-specific alloantibodies (DSA), chronic transplant arteriopathy (CTA) and capillary C4d deposition. B10.BR recipients of B10.A hearts developed transient DSA and C4d deposition that peaked on day 7 and became undetectable at day 56 while CTA developed progressively. Male cardiac grafts in female recipients showed similar degrees of CTA at day 56 but never developed DSA or C4d deposition, indicating that T cell-mediated mechanisms are sufficient to produce CTA. Passive transfer of monoclonal IgG2a anti-H-2K(k) into B6.RAG1 KO recipients of B10.BR hearts over 14-28 days led to progressive CTA. If treatment was stopped on day 14, lesions showed little progression and had no C4d deposition or detectable DSA on day 42. If treatment was stopped on day 28 when the lesions were fully developed, no regression occurred over the next 28 days, even though C4d deposition and circulating antibody became undetectable. Therefore, a minimum threshold of antibody exposure is needed to cause CTA. Once the CTA develops, C4d may become negative after DSA disappears. Thus, serial samples are needed in clinical studies to ascertain the relevance of alloantibody to the lesions of chronic graft rejection.

The aetiology and pathogenesis of chronic allograft nephropathy

Renal transplantation is the ultimate form of renal replacement therapy, and is the treatment of choice for many patients with end-stage renal failure. The advent of calcineurin inhibitor based immunosuppression resulted in the 1-year renal allograft failure rate dropping from around 50% twenty years ago to less than 10% in more recent times. Despite a massive improvement in renal allograft survival in the first year following transplantation 10-year graft survival can be as low as 50%. Chronic allograft nephropathy (CAN) is recognised as the main cause of renal allograft failure following the first year after transplantation. The diagnosis of CAN can only be made histologically. Typically biopsy specimens in grafts with CAN demonstrate an overall fibrotic appearance effecting the vascular endothelium, renal tubules, interstitium, and glomerulus. The risk factors for CAN are divided into alloimmune and alloimmune independent. Alloimmune dependent factors include acute cellular rejection, severity of rejection, subclinical rejection and HLA mismatch. Alloimmune independent factors such as delayed graft function, donor age, Cytomegalovirus infection, donor/recipient co-morbidity and of course calcineurin inhibitor toxicity are important in the development of CAN. The pathogenesis of CAN is complex, multifactorial, and unfortunately incompletely understood. There are a number of pivotal steps in the initiation and propagation of the fibrosis seen in biopsy specimens from kidneys with CAN. Endothelial activation in response to one or more of the aforementioned risk factors stimulates leukocyte activation and recruitment. Recruited leukocytes subsequently infiltrate through the endothelium and induce key effector cells to secrete excessive and abnormal extracellular matrix (ECM). Enhanced deposition of ECM is a histological hallmark of CAN. This paper aims to present a concise yet accurate and up-to-date review of the literature concerning the aetiological factors and pathological processes which are present in the generation of CAN.

Assessment of renal graft function depending on pre-transplant morphology

BACKGROUND

Histopathological assessment of kidney prior to transplantation is a part of the comprehensive information gathered on the transplanted organ. In our study we monitor the influence of individual morphological findings (glomeruli, arteries, arterioles, interstitium, tubules) and degree of histopathological changes in the kidney function after transplantation.

METHODS

From 1994 to 1997, 117 cadaveric kidneys were histopathologically examined and subsequently transplanted. Biopsy in a form of wedge excision was obtained during the organ procurement after in situ kidney perfusion and its removal from donor's body. Evaluated were glomerulosclerosis, intimal fibrosis of arteries, arteriolar hyalinization, interstitial fibrosis and tubular changes (vacuolar dystrophy of tubular epithelium, desquamation of tubular epithelium, brush border of proximal tubules, tubular dilatation, haemoglobin cylinders in distal tubules). Kidney recipients were monitored both for immediate function of transplanted organ and long-term kidney function for a period of five years following.

RESULTS

In our group of patients, no unambiguously negative influence of histopathological change in individual morphologies was found either in the immediate or in the long-term function of the transplanted kidney.

CONCLUSION

It is possible to transplant kidneys and attain satisfactory results even with these types of histopathological changes: glomerulosclerosis greater or equal to 20 %, mild degree of arterial lesion, moderate arteriolar lesions, moderate lesions of interstitial fibrosis and tubular lesions. The degree of arterial lesions, arteriolar lesions and the degree of interstitial fibrosis closely correlate to the donor's age, hypertension and nontraumatic cerebrovascular accident as the cause of death. Same outcomes were also confirmed with glomerulosclerosis, with the exception of the influence of the donor's age.

Chronic allograft nephropathy: current concepts and future directions

The paradigm that chronic rejection causes all progressive late allograft failure has been replaced by a hypothesis of cumulative damage, where a series of time-dependent immune and nonimmune mechanisms injure the kidney and lead to chronic interstitial fibrosis and tubular atrophy, representing a final common pathway of injury and its consequent fibrotic healing response. Allograft damage is common, progressive, time-dependent, clinically important and modified by immunosuppression. Early after transplantation, tubulointerstitial damage is predominantly related to ischemia reperfusion injury, acute tubular necrosis, acute and subclinical rejection and/or calcineurin inhibitor nephrotoxicity, superimposed on preexisting donor disease. Later, cellular inflammation lessens and is replaced by microvascular and glomerular injury from calcineurin inhibitor nephrotoxicity, hypertension, immune-mediated fibrointimal vascular hyperplasia, transplant glomerulopathy and capillary injury, polyoma virus and/or recurrent glomerulonephritis. Additional mechanisms of injury include internal architectural disruption of the kidney, cortical ischemia, persistent chronic inflammation, replicative senescence, cytokine excess and fibrosis induced by epithelial-to-mesenchymal transition. Current understanding of the etiology, pathophysiology and evolution of pathological changes are detailed. An approach to histological assessment of the individual failing graft are presented and a series of postulates are defined for future studies of chronic allograft nephropathy.

Longitudinal analysis of chronic allograft nephropathy: clinicopathologic correlations

BACKGROUND

Loss of the allograft from chronic allograft nephropathy and death of the patient from vascular, malignant, or infective disease are the major problems in renal transplantation today. Protocol biopsy of the long-term kidney has provided new data with which to develop strategies for prevention and treatment of chronic allograft nephropathy.

METHODS

Two series of long-term protocol biopsies are reviewed. In the first, renal biopsies were obtained at time 0, and at 3 months and 12 months, and the recipients of the renal allografts were followed up for up to 15 years. In the second, the kidneys of recipients of simultaneous pancreas kidney transplants were biopsied annually for 10 years, and the results correlated with clinical events.

RESULTS

Chronic allograft nephropathy is caused by acute and chronic immune-mediated damage, as well as by chronic calcineurin inhibitor nephrotoxicity. Both immune and nonimmune mechanisms exacerbate pre-existing donor disease and ischemia-reperfusion injury. Established interstitial fibrosis and arteriolar hyalinosis lead to progressive glomerular sclerosis and eventual loss of the graft.

CONCLUSION

Protocol biopsies have shown that clinical parameters of renal function underestimate the severity of chronic graft damage. Strategies for preventing or treating chronic renal allograft dysfunction and subsequent graft loss must better control rejection and simultaneously avoid nephrotoxicity.

La reprise retardée de fonction : une complication fréquente, non résolue, en transplantation rénale

Delayed graft function (DGF) is a frequent and well-known complication of renal transplantation, which occurs in 30% of cadaver kidney allografts. It has an economic cost that is the result of prolonged patient hospitalization and the need for hemodialysis sessions; it also increases the risk of acute allograft rejection and may affect long-term graft survival. Lots of risk factors were identified, like donor hemodynamic compromise or prolonged cold ischemia time; however, incidence of DGF remains high due to the frequent use of marginal donors due to organ shortage. Recent advances in the pathophysiology of DGF point the importance of the ischemia-reperfusion injury mechanisms and some therapeutics that may reduce them are under investigation, like the use of new solutions to improve organ preservation and the use of some antioxidant and anti-inflammatory drugs.

Protocol Transplant Biopsies: Are They Really Needed?

Studies suggest that surveillance or protocol biopsies that are performed during the first year after kidney transplantation may be clinically useful in identifying early acute rejection or chronic allograft nephropathy at a point when they may be amenable to treatment. Although the benefit of this approach has yet to be evaluated in large, multicenter, prospective trials, numerous studies suggest that implementation of protocol biopsies may improve long-term graft function. In particular, a number of reports suggest that detection of chronic allograft nephropathy in early protocol biopsies is predictive of subsequent graft function and loss and that early treatment may have a dramatic effect on the outcome of the graft. Protocol biopsies also have the potential to be of great value in high-risk patients, such as those with delayed graft function, by allowing for early intervention for acute rejection. Furthermore, the procedure seems to be relatively straightforward and safe. Nevertheless, paucity of data has meant that clear proof of a benefit of early treatment of subclinical rejection and chronic allograft nephropathy detected by protocol biopsy is lacking. Moreover, the optimal timing of protocol biopsies and reliable methods to quantify the histologic changes observed in biopsy specimens have yet to be determined. This review discusses the pros and cons of protocol biopsies and considers the place of this procedure in the routine treatment of kidney transplant patients.

Predicting subsequent decline in kidney allograft function from early surveillance biopsies

Identifying factors that are predictive of allograft loss might be an important step toward prolonging kidney allograft survival. In this study we sought to determine the association between histologic changes on 1-year surveillance biopsies, changes in graft function and survival. This analysis included 292 adults, recipients of kidneys from living donors (69%) or deceased donors (31%), transplanted between 1998 and 2001 and followed up for 46 +/- 14 months. The primary end point was death-censored graft loss or a >50% reduction in GFR beyond 1 year. One-year biopsies were classified as: (i) Normal (N = 87, 30%), (ii) inflammation (N = 6, 2%), (iii) fibrosis (N = 131, 45%), (iv) fibrosis and inflammation (N = 53, 18%) and (v) transplant glomerulopathy (N = 15, 5%). By multivariate Cox analysis, survival related to biopsy classification (HR = 4.2, p = 0.001), graft function (HR = 0.97, p = 0.001) and HLA mismatches (HR = 1.003, p = 0.004). Using normal histology as a reference, fibrosis and inflammation (HR = 8.5, p < 0.0001) and glomerulopathy (HR = 10, p < 0.0001) related to poorer survival but mild fibrosis alone did not. Importantly, the degree of inflammation associated with fibrosis generally did not qualify for the diagnosis of borderline rejection. In conclusion, inflammation and glomerulopathy 1 year post-transplant predict loss of graft function and graft failure independently of function and other variables.

Chronic renal allograft dysfunction

The major causes of renal transplant loss are death from vascular, malignant or infectious disease, and loss of the allograft from chronic renal dysfunction associated with the development of graft fibrosis and glomerulosclerosis. Chronic allograft nephropathy (CAN) is the histologic description of the fibrosis, vascular and glomerular damage occurring in renal allografts. Clinical programs rely on monitoring change in serum creatinine for identification of patients at risk of CAN, but this change occurs late in the course of the disease, and underestimates the severity of pathologic change. CAN has several causes: ischemia-reperfusion injury, ineffectively or untreated clinical and subclinical rejection, and superimposed calcineurin inhibitor nephrotoxicity, exacerbating pre-existing donor disease. Once established, interstitial fibrosis and arteriolar hyalinosis lead to progressive glomerulosclerosis over the subsequent years. There have been a number of approaches to treatment aimed at reducing the impact of CAN, mostly centered around avoidance of calcineurin inhibitors through their elimination in all, or just selected, patients. These immunosuppression strategies combine corticosteroids with azathioprine or mycophenolate mofetil, and/or sirolimus and everolimus. Late identification of CAN in individual patients has meant that strategies for intervening to prevent chronic renal allograft dysfunction and subsequent graft loss tend to be "too little and far too late."

Risk factors for chronic allograft nephropathy after renal transplantation: a protocol biopsy study

BACKGROUND

Chronic allograft nephropathy (CAN) leads to chronic allograft dysfunction and loss. Regular renal transplant biopsies may be useful to find risk factors for CAN.

METHODS

We carried out 688 protocol biopsies in 258 patients at 6, 12, and 26 weeks after renal transplantation. Patients with signs of CAN in the biopsy 3 (N= 70, CAN group), and those without (N= 120, non-CAN group), were compared.

RESULTS

Chronic tubulointerstitial changes increased from biopsy 1 to 3 (5% vs. 37%, P < 0.0001). Fifty-six of 190 patients had acute rejection within 6 months (30%), 33 of which were found in protocol biopsies (17%). On univariate analysis, the CAN group had CAN more often at biopsy 2 than the non-CAN group (23% vs. 4%, P < 0.0001), had a lower calculated creatinine clearance at biopsy 1 and 2 (49.4 +/- 25.8 vs. 57 +/- 20.2 mL/min, P= 0.01; 47.3 +/- 21.2 vs. 57.9 +/- 19.5 mL/min, P= 0.001, respectively), had a living donor less often than a brain dead donor (7% vs. 18%, P= 0.045), had a longer cold ischemia time (17.4 +/- 7 vs. 14.9 +/- 8.1 hours, P= 0.04), and had arterionephrosclerosis more often (24% vs. 12%, P= 0.02). On multivariate analysis, the differences in CAN at biopsy 2 (P= 0.001) and lower GFR at biopsy 2 (P= 0.002) were confirmed; in addition, nephrocalcinosis (P= 0.006) and acute rejection (P= 0.046) were found to occur more often.

CONCLUSION

Chronic tubulointerstitial changes develop early after renal transplantation and are associated with reduced kidney function. Risk factors for CAN are arterionephrosclerosis (donor-related), nephrocalcinosis (related to preexisting hyperparathyroidism), a long cold-ischemia time (ischemia-perfusion-related), and acute rejection. Renal functional decline precedes morphologic changes of CAN, expressed as tubular atrophy and interstitial fibrosis.

Kidney allograft fibrosis and atrophy early after living donor transplantation

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

Terminal Complement Components Mediate Release of von Willebrand Factor and Adhesion of Platelets in Arteries of Allografts

BACKGROUND

Both humoral and cellular immune responses can cause arterial injury in organ transplants, but the manifestations of these different inflammatory mechanisms have not been dissected fully. The present study was designed to define the effects of the terminal complement components on arterial injury in vivo.

METHODS

The authors have developed congenic rat strains with a C6 deficiency. The absence of C6 terminates the cascade of complement after C5 cleavage and prevents the assembly of the membrane attack complex. Hearts were transplanted from PVG.1A (RT1) rats to major histocompatibility complex-incompatible C6-deficient (C6-) or C6-sufficient (C6+) PVG.1U (RT1) rats.

RESULTS

PVG.1A (C6-) cardiac grafts were rejected acutely (6-7 days) by untreated PVG.1U (C6+) recipients but survived significantly longer in PVG.1U (C6-) recipients (8 to >30 days). Arteries of cardiac allografts in C6+ recipients demonstrated extensive endothelial injury evidenced by release of von Willebrand factor (vWF) and accompanied by platelet aggregation. In contrast, vWF was retained in Weibel-Palade storage granules of arterial endothelial cells in cardiac allografts that were rejected by C6- recipients. In the absence of C6, intimal alterations were limited to lifting of endothelial cells from supporting stroma by infiltrating mononuclear cells, duplicating the clinical lesion described as endotheliitis or intimal arteritis. Delaying graft rejection with a short course of cyclosporine did not decrease vWF release and platelet aggregation in PVG.1U (C6+) recipients.

CONCLUSIONS

Mononuclear cell infiltration of the arterial intima occurs in the absence of C6, but C6 deficiency limits the release of vWF from arterial endothelial cells.

Predictors of renal allograft histologic damage progression

The objective of this study was to analyze factors that are involved in the progression of renal allograft damage in the first 6 mo after transplantation. Donor and 6-mo protocol biopsies of 83 patients who received a renal transplant were classified using the Chronic Allograft Damage Index (CADI). Histologic changes were compared and correlated to clinical parameters at transplantation, at 6 mo, and annually over 2 yr. All CADI components increased significantly in the 6-mo posttransplantation period, except chronic vascular changes and the percentage of glomerulosclerosis. Total cholesterol and LDL- cholesterol at the time of biopsy correlated positively with mesangial matrix increase, and HDL cholesterol correlated negatively with vascular intima increase. High BP at biopsy was associated with tubular atrophy. Diastolic BP at biopsy correlated with 6-mo CADI (CADI-6). Patients with diastolic BP > or =85 mmHg at biopsy had a higher difference between CADI score in protocol biopsies and CADI score in donor biopsies (DeltaCADI) and higher creatinine at 1 and 2 yr. CADI in donor biopsies (CADI-0) >1 was more frequently found in older (odds ratio [OR], 1.07; 95% confidence interval [CI], 1.01 to 1.14) and nontraumatic dead donors (OR, 3.89; 95% CI, 1.13 to 13.33). CADI-6 >3 was more frequently found in those with CADI-0 >1 (OR, 3.82; 95% CI, 1.19 to 12.21), older donors (OR, 1.05; 95% CI, 1.01 to 1.10), and number of AB mismatches (OR, 2.36; 95% CI, 1.09 to 5.10). CADI-0, CADI-6, and DeltaCADI correlated significantly with serum creatinine at hospital discharge, at 6 mo, and at 2 yr. DeltaCADI was affected by initial percentage of glomerulosclerosis (OR, 1.10; 95% CI, 1.02 to 1.19) and creatinine at hospital discharge (OR, 1.01; 95% CI, 1.00 to 1.02). Donor-related as well as nonimmunologic factors, such as hypertension and dyslipidemia, are associated with increased risk for renal allograft damage progression.

Benefit-Risk Assessment of Sirolimus in Renal Transplantation

Sirolimus (rapamycin) is a macrocyclic lactone isolated from a strain of Streptomyces hygroscopicus that inhibits the mammalian target of rapamycin (mTOR)-mediated signal-transduction pathways, resulting in the arrest of cell cycle of various cell types, including T- and B-lymphocytes. Sirolimus has been demonstrated to prolong graft survival in various animal models of transplantation, ranging from rodents to primates for both heterotopic, as well as orthotopic organ grafting, bone marrow transplantation and islet cell grafting. In human clinical renal transplantation, sirolimus in combination with ciclosporin (cyclosporine) efficiently reduces the incidence of acute allograft rejection. Because of the synergistic effect of sirolimus on ciclosporin-induced nephrotoxicity, a prolonged combination of the two drugs inevitably leads to progressive irreversible renal allograft damage. Early elimination of calcineurin inhibitor therapy or complete avoidance of the latter by using sirolimus therapy is the optimal strategy for this drug. Prospective randomised phase II and III clinical studies have confirmed this approach, at least for recipients with a low to moderate immunological risk. For patients with a high immunological risk or recipients exposed to delayed graft function, sirolimus might not constitute the best therapeutic choice--despite its ability to enable calcineurin inhibitor sparing in the latter situation--because of its anti-proliferative effects on recovering renal tubular cells. Whether lower doses of sirolimus or a combination with a reduced dose of tacrolimus would be advantageous in these high risk situations remains to be determined. Clinically relevant adverse effects of sirolimus that require a specific therapeutic response or can potentially influence short- and long-term patient morbidity and mortality as well as graft survival include hypercholesterolaemia, hypertriglyceridaemia, infectious and non-infectious pneumonia, anaemia, lymphocele formation and impaired wound healing. These drug-related adverse effects are important determinants in the choice of a tailor-made immunosuppressive drug regimen that complies with the individual patient risk profile. Equally important in the latter decision is the lack of severe intrinsic nephrotoxicity associated with sirolimus and its advantageous effects on arterial hypertension, post-transplantation diabetes mellitus and esthetic changes induced by calcineurin inhibitors. Mild and transient thrombocytopenia, leukopenia, gastrointestinal adverse effects and mucosal ulcerations are all minor complications of sirolimus therapy that have less impact on the decision for choosing this drug as the basis for tailor-made immunosuppressive therapy. It is clear that sirolimus has gained a proper place in the present-day immunosuppressive armament used in renal transplantation and will contribute to the development of a tailor-made immunosuppressive therapy aimed at fulfilling the requirements outlined by the individual patient profile.

Evolution and Pathophysiology of Renal-Transplant Glomerulosclerosis

BACKGROUND

Glomerulosclerosis (GS) is characteristic of chronic allograft nephropathy and graft failure; however, its natural history and pathophysiology are poorly defined.

METHODS

We evaluated 959 prospective protocol kidney-transplant biopsies from 120 recipients taken regularly up to 10 years after transplantation for evidence of glomerular injury.

RESULTS

GS exhibited a nonlinear triphasic time course. An intense but limited peak of damage in the first month was associated with cold ischemia (P<0.05) and calcineurin nephrotoxicity (P<0.001). GS then occurred as a late consequence of earlier immune-mediated tubular damage (9.3+/-6.6%, P<0.01 vs. no damage), suggesting delayed sclerosis of atubular glomeruli. Subsequent progressive GS occurred beyond 4 years, associated with increasing arteriolar hyalinosis from calcineurin inhibitor nephrotoxicity (r=0.33, P<0.001). From 5 years after transplantation, 32.4+/-22.2% of glomeruli were globally sclerosed, and segmental GS and periglomerular fibrosis increased by 4.0+/-9.3% and 8.4+/-14.2% per year, respectively. Severe arteriolar hyalinosis resulted in greater GS on sequential biopsies (P<0.001), consistent with vascular narrowing causing glomerular ischemia. Chronic glomerulopathy scores were relatively mild. Glomerular loss was patchy, with a high coefficient of variation of 633%. Isotopic glomerular filtration rate correlated best with Banff chronic interstitial fibrosis (r=-0.30, P<0.001) and chronic glomerulopathy scores (r=-0.23, P<0.001) rather than the percentage of sclerosed glomeruli (r=-0.12, P<0.05). Renal function gradually fell with time, and the hyperfiltration index increased from 1.14+/-0.42 at 3 months to 1.83+/-1.40 by 7 to 10 years after transplantation.

CONCLUSIONS

In summary, GS is a time-dependent response to glomerular injury from early ischemia, immune-mediated tubular loss, and late calcineurin nephrotoxicity.

Natural History, Risk Factors, and Impact of Subclinical Rejection in Kidney Transplantation

BACKGROUND

Subclinical rejection (SCR) is defined as histologically proven acute rejection in the absence of immediate functional deterioration.

METHODS

We evaluated the impact of SCR in 961 prospective protocol kidney biopsies from diabetic recipients of a kidney-pancreas transplant (n=119) and one kidney transplant alone taken regularly up to 10 years after transplantation.

RESULTS

SCR was present in 60.8%, 45.7%, 25.8%, and 17.7% of biopsies at 1, 3, 12, and greater than 12 months after transplantation. Banff scores for acute interstitial inflammation and tubulitis declined exponentially with time. SCR was predicted by prior acute cellular rejection and type of immunosuppressive therapy (P<0.05-0.001). Tacrolimus reduced interstitial infiltration (P<0.001), whereas mycophenolate reduced tubulitis (P<0.05), and the combination effectively eliminated SCR (P<0.001). Persistent SCR of less than 2 years duration on sequential biopsies occurred in 29.2% of patients and was associated with prior acute interstitial rejection (P<0.001) and requirement for antilymphocyte therapy (P<0.05). It resolved by 0.49 +/- 0.33 years and resulted in higher grades of chronic allograft nephropathy (CAN, P<0.05). True chronic rejection, defined as persistent SCR of 2 years or more duration and implying continuous immunologic activation was found in only 5.8% of patients. The presence of SCR increased chronic interstitial fibrosis, tubular atrophy, and CAN scores on subsequent biopsies (P<0.05-0.001). SCR preceded and was correlated with CAN (P<0.001) on sequential analysis.

CONCLUSIONS

Histologic evidence of acute rejection in the absence of clinical suspicion resulted in significant tubulointerstitial damage to transplanted kidneys and contributed to CAN.

Subclinical rejection and borderline changes in early protocol biopsy specimens after renal transplantation

BACKGROUND

To determine the significance of early subclinical rejection, we reviewed protocol biopsies performed on days 7 and 28 during a 4-year period.

METHODS

The study was confined to patients (n=115) with stable graft function at the time of biopsy; 76 adequate biopsies at day 7 and 79 at day 28 were performed.

RESULTS

At day 7, 10 biopsy specimens (13%) showed acute rejection (AR) and 9 (12%) showed borderline changes. Eight of 10 patients with AR received immediate pulsed methylprednisolone (MP) and one untreated patient developed clinical rejection (CR) within 3 days. Four of nine patients whose biopsy specimens showed borderline changes received MP and three untreated patients developed CR within 3 days. At day 28, six biopsy specimens (8%) showed AR and 13 (16%) showed borderline changes. Three of six patients with AR received immediate pulsed MP and one untreated patient developed CR within 6 days. Ten of 13 patients with borderline changes had been treated for AR in the previous 3 weeks. Twelve patients with subclinical rejection or borderline changes at day 28 were never subsequently treated for rejection, and outcome at 6 years did not differ from those patients whose biopsy specimens showed no rejection.

CONCLUSIONS

Compared with some units, the incidence of subclinical rejection is low. The majority of untreated subclinical borderline changes and rejection at day 7 behaved as early clinical rejections and at day 28 as resolving clinical rejections. Untreated subclinical rejection or borderline change at day 28 was not an adverse prognostic factor for long-term outcome.

Preservation of renal function during maintenance therapy with cyclosporine

During the last 20 years the management of cyclosporine (CsA) has improved due to the introduction of microemulsion technology, C2 monitoring, and combination with other new immunosuppressants. All these modifications have reduced the incidence of biopsy-proven acute rejection episodes to approximately 10%. However despite the wide experience, there are unanswered questions regarding CsA monitoring after the first year. Available clinical and histological data suggest that the therapeutic range to avoid nephrotoxicity or underimmunosuppression during the maintenance period is rather narrow. Furthermore, the combination of CsA with new immunosuppressants may modify the target CsA levels. Although the utility of C2 levels during the first year has been well characterized, there are few data on its utility for maintenance therapy, particularly the therapeutic range for C2 levels in patients receiving different immunosuppressive combinations. Since serum creatinine does not precisely reflect the progression of chronic allograft nephropathy, the efficacy of C2 monitoring during the maintenance period must be assessed not only by means of evaluation of renal function, but also histologic assessment using protocol biopsies.

The natural history of chronic allograft nephropathy

BACKGROUND

With improved immunosuppression and early allograft survival, chronic allograft nephropathy has become the dominant cause of kidney-transplant failure.

METHODS

We evaluated the natural history of chronic allograft nephropathy in a prospective study of 120 recipients with type 1 diabetes, all but 1 of whom had received kidney-pancreas transplants. We obtained 961 kidney-transplant-biopsy specimens taken regularly from the time of transplantation to 10 years thereafter.

RESULTS

Two distinctive phases of injury were evident as chronic allograft nephropathy evolved. An initial phase of early tubulointerstitial damage from ischemic injury (P<0.05), prior severe rejection (P<0.01), and subclinical rejection (P<0.01) predicted mild disease by one year, which was present in 94.2 percent of patients. Early subclinical rejection was common (affecting 45.7 percent of biopsy specimens at three months), and the risk was increased by the occurrence of a prior episode of severe rejection and reduced by tacrolimus and mycophenolate therapy (both P<0.05) and gradually abated after one year. Both subclinical rejection and chronic rejection were associated with increased tubulointerstitial damage (P<0.01). Beyond one year, a later phase of chronic allograft nephropathy was characterized by microvascular and glomerular injury. Chronic rejection (defined as persistent subclinical rejection for two years or longer) was uncommon (5.8 percent). Progressive high-grade arteriolar hyalinosis with luminal narrowing, increasing glomerulosclerosis, and additional tubulointerstitial damage was accompanied by the use of calcineurin inhibitors. Nephrotoxicity, implicated in late ongoing injury, was almost universal at 10 years, even in grafts with excellent early histologic findings. By 10 years, severe chronic allograft nephropathy was present in 58.4 percent of patients, with sclerosis in 37.3 percent of glomeruli. Tubulointerstitial and glomerular damage, once established, was irreversible, resulting in declining renal function and graft failure.

CONCLUSIONS

Chronic allograft nephropathy represents cumulative and incremental damage to nephrons from time-dependent immunologic and nonimmunologic causes.

Heterogeneity in the evolution and mechanisms of the lesions of kidney allograft rejection in mice

The natural history and pathogenesis of the pathologic lesions that define rejection of kidney transplants have not been well characterized. We studied the evolution of the pathology of rejection in mouse kidney allografts, using four strain combinations across full major histocompatibility complex (MHC) plus nonMHC disparities, to permit more general conclusions. Interstitial infiltrate, MHC induction, and venulitis appeared by day 5, peaked at day 7-10, then stabilized or regressed by day 21. In contrast, tubulitis, arteritis, and glomerulitis were absent or mild at days 5 and 7, but progressed through day 21, indicating separate regulation and homeostatic control of these lesions. Edema, hemorrhage, and necrosis also increased through day 21. All lesions were T-dependent, failing to develop in T-cell-deficient hosts. Allografts into immunoglobulin-deficient hosts manifested typical infiltration, MHC induction, and tubulitis at days 7 and 21, indicating that these lesions are alloantibody-independent. However at day 21 kidneys rejecting in immunoglobulin-deficient hosts showed decreased edema, arteritis, venulitis, and necrosis. Thus the three groups of lesions are: T-cell-mediated interstitial infiltration, MHC induction, and venulitis, which develops rapidly then stabilizes; slower but progressive T-cell-mediated tubulitis and arteritis; and late antibody-mediated endothelial injury, which contributes to late edema, arteritis, and venulitis.

Current status of kidney transplant: update 2003

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

The stability of the glomerular filtration rate after renal transplantation is improving

The 6-mo function and the stability of function posttransplantation in 429 cadaver renal transplants was investigated from 1990 to 2000. The 6-mo creatinine clearance (CrCl) and the rate of change of CrCl beyond 6 mo posttransplantation were calculated. The mean 6-mo CrCl was 64.6 +/- 1.1 ml/min and was stable between 1990 and 2000. The net slope of CrCl was -1.4 +/- 0.5 ml/min per yr. The slope has improved in recent years, such that the mean slopes in the period after 1997 are actually positive (+3.5 ml/min per yr). The slope of CrCl beyond 6 mo was not related to the actual value of the 6 mo CrCl, i.e., there was no accelerated loss of function at low CrCl levels. The 6-mo CrCl was independently determined by donor factors (age, gender), recipient factors (age, gender), and immune factors (rejection episodes, regraft status). The slope of the CrCl correlated independently with the transplant year, recipient gender, rejection episodes, diastolic BP, and the choice of immunosuppressive drugs. Cytomegalovirus infection and mismatch status and lipid levels and treatment were not independently associated with slope or 6-mo CrCl. Thus, the most striking change in the course of renal transplants over the past decade is the new stability of function, correlating with reduced rejection and probably due at least in part to the new immunosuppressive agents. Despite continued calcineurin inhibitor use, late improvement in function now occurs in many cadaver kidney transplants, suggesting a previously unappreciated capacity for functional adaptation.

Structural and functional correlations in stable renal allografts

BACKGROUND

Renal functional reserve (RFR) has been proposed as a surrogate marker of renal mass, but its significance in well-functioning renal transplants is controversial. Thus, we used early protocol biopsies to analyze structural and functional correlations in stable grafts.

METHODS

We studied 32 cyclosporine (CsA)-treated stable cadaveric transplants at 5 months. Biopsies were evaluated according to Banff criteria and histomorphometry. Inulin and p-aminohippurate clearances were used to calculate glomerular filtration rate (GFR) and effective renal plasma flow (ERPF). RFR after an amino acid infusion (RFR-AA) and after a combined amino acid and dopamine infusion (RFR-AA-DOPA) was evaluated.

RESULTS

Baseline GFR was 54 +/- 16 mL/min/1.73 m2, and ERPF was 219 +/- 55 mL/min/1.73 m2. RFR-AA was 9% +/- 13%, and RFR-AA-DOPA was 22% +/- 20%. RFR-AA correlated with CsA dose (R = 0.39; P = 0.02), whereas RFR-AA-DOPA correlated with CsA dose (R = 0.36; P = 0.04) and CsA levels (R = 0.40; P = 0.02). The only histological parameter associated with RFR was the presence of arteriolar hyalinosis (AH). Patients showing an AH score of 1 or greater (n = 7) had lower RFR-AA (0% +/- 9% versus 11% +/- 13%; P = 0.02) and lower RFR-AA-DOPA (9% +/- 17% versus 26% +/- 19%; P = 0.03). Multivariate analysis showed that an AH score of 1 or greater, but not CsA dose or levels, was associated with RFR-AA (R = 0.42; P = 0.01). RFR-AA-DOPA was associated with hyaline arteriolar damage (R = 0.43; P = 0.01), as well as CsA levels (R = 0.54; P = 0.006).

CONCLUSION

The presence of AH is the only histological parameter associated with impaired RFR in well-functioning grafts.

Optimizing the long-term outcome of renal transplants: opportunities created by sirolimus

This review focuses upon the sirolimus-based cyclosporine elimination studies and the light they shed on choice of the best long-term immunosuppressive strategy for managing the balance between prevention of loss of grafts from antigen specific immune responses or from chronic nephrotoxicity. The underlying strategy of both cyclosporine elimination studies was to treat patients with a uniform therapy for the first 3 months and then wean off the cyclosporine therapy in one cohort. The Phase II study was conducted in 246 recipients in 17 centers in the USA and Europe. Thus 97 patients were treated with full-dose cyclosporine, fixed-dose sirolimus and corticosteroids, and 100 patients received reduced-dose cyclosporine and trough concentration controlled sirolimus with corticosteroids until 3 months when the dose of cyclosporine was tapered progressively. The phase III study was undertaken in 525 patients in 57 centers in Australia, Canada and Europe with randomization for cyclosporine elimination undertaken at 3 months and implemented over the next 4-6 weeks. The primary outcome of renal function was better in the elimination arms of both studies and, in the phase III study, continued to improve for up to 2 years. Both studies demonstrated better renal function, equivalent patient and graft survival and no difference in acute rejection rates. These studies have shown that one of the successful strategies for improving the longer term graft survival rates includes the continuous use of sirolimus and steroids, without calcineurin inhibitors.

Late deterioration of organ transplants: a problem in injury and homeostasis

The late deterioration of allografts remains a problem despite improvements in short-term and long-term graft survival. The previous concept that late deterioration reflects a specific disease -- chronic rejection -- is being replaced. The new view is that many factors are involved in late deterioration, including the age and pretransplant condition of the organ, injury from brain death, injury from the transplant process, T cell-mediated and antibody-mediated rejection (in some cases reflecting poor compliance with immunosuppressive drugs) and post-transplant organ-specific stresses in the new environment, including drug toxicity, infectious agents, hypertension and lipids. Ultimately these stresses interact with the intrinsic limitations in repair and homeostasis in the tissues of the organ, producing characteristic syndromes. The most important recent advance has been the emergence of potent immunosuppressive drug combinations that have greatly reduced rejection.

Mechanism of T cell-mediated endothelial apoptosis

BACKGROUND

Cytotoxic T lymphocyte (CTL)-mediated destruction of allogeneic vascular endothelium is important in the pathogenesis of both acute and chronic allograft rejection. Despite the importance of this phenomenon, the effector mechanisms responsible for endothelial cell killing are not well defined, and conflicting conclusions have been reached based on variation in experimental methodology.

METHODS

We used a recently described method for isolating mouse vascular endothelium to evaluate endothelial cell lysis by CTLs. Endothelial cell destruction was assessed in vitro both by 51Cr release and DNA fragmentation using wild-type and lpr (Fas deficient) endothelium of C3H/HeJ (H2(k)) mice by MHC alloantigen-specific T cells of wild-type, gld (Fas ligand deficient), and perforin-deficient mice on a C57BL/6 (H2(b)) background.

RESULTS

Although maximal lysis of 56.6+/-0.8% was seen when using wild-type targets and effectors, only a moderate decrease in apoptosis to 37.6+/-4.0% was detected when the Fas/Fas ligand death receptor pathway was eliminated. This decrease in cytotoxicity occurred despite the preserved functional capacity of this pathway. Alternatively, a significant decrease in cytotoxicity to 17.4+/-4.7% was seen when the perforin/granzyme exocytosis pathway was eliminated.

CONCLUSIONS

These data indicate that CTLs destroy vascular endothelium primarily by the perforin/granzyme exocytosis pathway with only a minor contribution to apoptosis by the Fas/Fas ligand death receptor pathway. These data are critical for the proper interpretation of studies evaluating acute and chronic allograft rejection and for the design of rational strategies to ameliorate vascular injury concomitant to the rejection process.

The marginal kidney donor

In parallel with increased clinical demand, less than optimal or so-called marginal kidney grafts are being used for transplantation. In addition to donor age, it appears that several factors may impact negatively on the quality of the graft. Most importantly, a more precise definition of the term 'marginal graft' is needed. The present review analyzes potential risk factors, suggests scoring systems for a more precise definition, and discusses potential treatment options to improve the quality of marginal grafts.

Hypertension is an independent predictor of delayed graft function and worse renal function only in kidneys with chronic pathological lesions

BACKGROUND

Delayed graft function (DGF) has been identified as one of the principal correlates of poor graft survival in cadaveric renal transplantation. However, its risk factors and clinical predictors have been poorly elucidated.

METHODS

We analyzed the risk factors of DGF with a specific emphasis on the role of histological damage of donor kidney. Then, we also studied the impact of DGF, and donor factors affecting DGF, on kidney graft function over the first year after engraftment in 100 consecutive cadaveric renal transplant (Tx) recipients.

RESULTS

The organs displaying DGF (n=48) had a significantly higher degree of glomerular sclerosis and tubular atrophy (P<0.01), as well as of interstitial fibrosis and vascular damage (P<0.02) in time-zero biopsies. In patients who received an "ideal" organ for Tx (total histological score < or = 4), DGF showed a strong relationship with Deltaage D-R (70% increase of risk for donors 10 years older than recipients), and with the histological score (odds ratio 1.34). In contrast, donor hypertension was the most relevant variable independently associated with DGF (odds ratio 19.4) in patients receiving a suboptimal organ (histological score >4). Moreover, DGF and donor hypertension adversely affected graft function at 1 year, but only in Tx patients with a histological score >4 in time-zero biopsy. Of note, both patients with and those without DGF showed a very low incidence of biopsy-proven acute rejection (8.5 and 6.8%, respectively) and a rather short cold ischemia time (<16 hr).

CONCLUSION

Our findings suggest that the quality of the transplanted organ and the occurrence of DGF are strictly related to each other and can influence graft function through apparently nonimmune mechanisms. In addition, long-standing donor hypertension is a strong independent variable affecting both DGF and graft function of suboptimal cadaveric kidneys, at least up to 1 year.

Reliability of chronic allograft nephropathy diagnosis in sequential protocol biopsies

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Cyclosporin A-induced gingival overgrowth is unrelated to allograft function in renal transplant recipients

BACKGROUND

Severe gingival hyperplasia (GH) is one of the most frequent side-effects associated with the prescription of Cyclosporine-A (CsA).

AIM

This study statistically modeled the medical and dental risk factors for the development of GH following CsA administration to determine whether renal function post-transplantation was related to the incidence or extent of GH in 236 consecutive renal transplant patients.

METHOD

All patients were at least 6 months post-transplant and medicated with both traditional oral CsA (n=220 individuals) and the new microemulsion form CsA-Me (n=229 individuals). Patients had either received CsA alone (n=45 individuals) or cyclosporine and nifedipine (n=191 individuals). Gingival overgrowth was assessed and computerized data, available for all patients included; pre- and post-transplant medical history and post-transplant renal function, i.e., serum creatinine levels, documented rejection episodes and glomerular filtration rates (GFR). These data together with CsA serum levels and last-recorded dose of CsA, CsA-Me, nifedipine, azathioprine and prednisolone, were analysed by multivariate regression analysis using SPSS.

RESULTS

The extent and severity of hyperplasia was significantly correlated with the dosage and serum level of CsA at 3, 6 and 12 months post-transplantation; last recorded dosage, however (p<0.0001), was the most accurate predictor of hyperplasia. Gingivitis (p<0.0001) and plaque (p<0.002), were associated with hyperplasia. Duration of renal replacement therapy, age at transplantation, post-transplant interval serum creatinine levels and documented rejection episodes were unrelated with the extent and severity of GH. Of all the renal variables only the correlation of GFR with last recorded doses of CsA and CsA-Me, approached significance; this was then considered for inclusion in the model.

CONCLUSION

In a multiple regression analysis including GFR, however, only last CsA (and CsA-Me) doses and gingivitis score were selected for inclusion in the final model. These data demonstrate that inter-patient variation in the extent and severity of GH and renal function post-transplantation are unrelated and are mediated independently.

Serial protocol biopsies to quantify the progression of chronic transplant nephropathy in stable renal allografts

AIM

To evaluate the utility of intimal thickness and interstitial width as a primary efficacy variable in the design of clinical trials aimed to modify the natural history of chronic allograft nephropathy.

METHODS

A donor and a 4-month protocol biopsy were evaluated in 40 stable grafts according to the Banff schema. In 27 patients, a second protocol biopsy was done at 1 yr. Arterial intimal volume fraction (Vvintima/artery) and cortical interstitial volume fraction (Vvinterstitium/cortex) were estimated with a point counting technique.

RESULTS

Chronic Banff scores increased during follow-up, while acute scores reached its peak at 4 months. Vvintima/artery and Vvinterstitium/cortex significantly increased at 4 months, but not at 1 yr. Vvintima/artery at 4 months correlated with donor Vvintima/artery (r = 0.57, p < 0.001), histocompatibility (r = 0.38, p = 0.01) and serum cholesterol (r = 0.31, p = 0.047). Vvinterstitium/cortex at 4 months correlated with recipient body surface area (r = 0.44, p = 0.004) and delayed graft function (p = 0.016). Power calculations showed that Vvintima/artery and Vvinterstitium/cortex allow an important reduction in minimum sample size of a hypothetical trial aimed to prevent chronic allograft nephropathy.

CONCLUSIONS

Intimal thickening and interstitial widening progresses rapidly during the first 4 months after transplantation and slowly thereafter. These parameters can be considered as a primary efficacy variable in trials aimed to prevent chronic allograft nephropathy.

Long-term allograft surveillance: the role of protocol biopsies

The safety of the renal allograft biopsy and the standardization of allograft histopathology interpretation have renewed interest in the performance of protocol (surveillance) biopsies. Recent surveillance biopsy studies in the areas of pre-implantation and in the early and late post-transplant periods are discussed.

Recommendations for the outpatient surveillance of renal transplant recipients. American Society of Transplantation

Many complications after renal transplantation can be prevented if they are detected early. Guidelines have been developed for the prevention of diseases in the general population, but there are no comprehensive guidelines for the prevention of diseases and complications after renal transplantation. Therefore, the Clinical Practice Guidelines Committee of the American Society of Transplantation developed these guidelines to help physicians and other health care workers provide optimal care for renal transplant recipients. The guidelines are also intended to indirectly help patients receive the access to care that they need to ensure long-term allograft survival, by attempting to systematically define what that care encompasses. The guidelines are applicable to all adult and pediatric renal transplant recipients, and they cover the outpatient screening for and prevention of diseases and complications that commonly occur after renal transplantation. They do not cover the diagnosis and treatment of diseases and complications after they become manifest, and they do not cover the pretransplant evaluation of renal transplant candidates. The guidelines are comprehensive, but they do not pretend to cover every aspect of care. As much as possible, the guidelines are evidence-based, and each recommendation has been given a subjective grade to indicate the strength of evidence that supports the recommendation. It is hoped that these guidelines will provide a framework for additional discussion and research that will improve the care of renal transplant recipients.

Effect of histological damage on long-term kidney transplant outcome

BACKGROUND

Chronic renal allograft failure remains a major challenge to overcome. Factors such as donor quality, delayed graft function (DGF), acute rejection, and immunosuppression are known to affect long-term outcome, but their relationship to histological damage to graft outcome is unclear.

METHODS

Protocol kidney biopsies (n=112) obtained at 3 months after transplantation yielded 102 with adequate tissue. Histology was scored by the Banff schema, and compared with implantation biopsies (n=91), repeat 12-month histology (n=39), decline in serum creatinine and serial isotopic glomerular filtration rate, onset of chronic allograft nephropathy (CAN), and actuarial graft survival censored for death with a functioning graft.

RESULTS

At a median follow-up of 9.3 years, 20 patients had graft failure and 26 died with a functioning graft. Banff chronic nephropathy was present in 24% of 3-month biopsies, and was predicted by microvascular disease in the donor, cold ischemia, DGF, and acute vascular rejection (P<0.001). Acute glomerulitis at 3 months correlated with segmental glomerulosclerosis at 12 months, subsequent recurrent glomerulonephritis, and graft failure (P<0.01). Subclinical rejection at 3 months occurred in 29% of biopsies, correlated with prior acute rejection and HLA mismatch, and led to chronic histological damage by 12 months (r=0.25-0.67, P<0.05-0.001). Subclinical rejection, arteriolar hyalinosis, and tubulitis present at 3 months had resolved by 12 months. The 10-year survival rates for Banff chronic nephropathy were 90.4% for grade 0, 81.0% grade 1, and 57.9% for grades 2 or greater (P<0.01). Early tubulointerstitial damage at 3 months profoundly influenced graft survival beyond 10 years. CAN was predicted by kidney ischemia, 3-month chronic intimal vascular thickening, tubular injury, proteinuria, and late rejection. Chronic fibrointimal thickening of the small arteries and chronic interstitial fibrosis at 3 months independently predicted graft loss and decline in renal function (P<0.05-0.001).

CONCLUSIONS

Early transplant damage occurs in the tubulointerstitial compartment from preexisting donor kidney injury and discrete events such as vascular rejection and DGF. Subsequent chronic damage and graft failure reflect accumulated previous injury and chronic interstitial fibrosis, vascular impairment, subclinical rejection, and injury from late rejection. CAN may be conceptualized as the sequelae of incremental and cumulative damage to the transplanted kidney. The duration of graft survival is dependent and predicted by the quality of the transplanted donor kidney combined with the intensity, frequency, and irreversibility of these damaging insults.

Protocol biopsies in the management of renal allograft recipients

The safety of the renal allograft biopsy and the standardization of allograft histopathology interpretation have renewed interest in the protocol biopsy. Recent studies in the areas of 'marginal' donors, surveillance of acute rejection, molecular biology and chronic rejection are discussed.

Cytoprotection of human umbilical vein endothelial cells against apoptosis and CTL-mediated lysis provided by caspase-resistant Bcl-2 without alterations in growth or activation responses

Graft endothelial cells are primary targets of host CTL-mediated injury in acute allograft rejection. As an in vitro trial of gene therapy to reduce CTL-mediated endothelial injury, we stably transduced early passage HUVEC with a caspase-resistant mutant form (D34A) of the anti-apoptotic gene Bcl-2. Bcl-2 transductants were compared with HUVEC transduced in parallel with an enhanced green fluorescent protein (EGFP) gene. Both transduced HUVEC have equivalent growth rates in complete medium and both show contact inhibition of growth. However, compared with EGFP-transduced HUVEC, the Bcl-2-transduced cells are resistant to the apoptotic effects of serum and growth factor withdrawal and are also resistant to the induction of apoptosis by staurosporine or by ceramide, with or without TNF. Transduced Bcl-2 did not reduce TNF-mediated NF-kappaB activation or constitutive expression of class I MHC molecules. HUVEC expressing D34A Bcl-2 were significantly more resistant to lysis by either class I-restricted alloreactive or PHA-redirected CTL than were HUVEC expressing EGFP. We conclude that transduction of graft endothelial cells with D34A Bcl-2 is a possible approach for reducing allograft rejection.