Features Of Chronic Allograft Nephropathy Research Articles

SDF‑1/CXCR4 induces epithelial‑mesenchymal transition through activation of the Wnt/β‑catenin signaling pathway in rat chronic allograft nephropathy.

Epithelial-mesenchymal transition (EMT) has been demonstrated to serve a crucial role in the progression of interstitial fibrosis, which is one of the principal pathological features of chronic allograft nephropathy (CAN). However, to the best of our knowledge, the mechanisms of EMT in CAN have not been investigated. In the present study, the effect of stromal cell-derived factor 1 (SDF-1) and the Wnt signaling pathway on the progression of EMT following kidney transplantation was investigated. The CAN model was established using Fisher 344 and Lewis rats, treated with low-dose cyclosporine with or without AMD3100. CAN was confirmed by the pathological alterations and chronic allograft damage index scoring, and EMT was confirmed by western blotting and reverse transcription-quantitative polymerase chain reaction. In the AMD3100 group, there were lower expression levels of α-SMA and higher expression levels of E-cadherin, which indicated that CAN and EMT were ameliorated by AMD3100. The kidney tissue was analyzed using an mRNA + long noncoding (lnc)RNA microarray. A total of 506 mRNAs and 404 lncRNAs were demonstrated to be significantly differentially expressed between the two groups, which revealed the involvement of SDF-1/CXC chemokine receptor 4 (CXCR4) and the Wnt pathway. SDF-1 was demonstrated to induce EMT in vitro through the upregulation of α-SMA, downregulation of E-cadherin and the wound healing assay, and in the rat renal tubular epithelial cells via the nuclear accumulation of β-catenin, which were all inhibited by either AMD3100 or DKK-1. CXXC finger protein 5 (CXXC5), a negative regulator of the Wnt pathway, was downregulated following treatment with SDF-1, which was inhibited by AMD3100 but not by DKK-1. Thus, CXXC5 may be a regulator downstream of SDF-1/CXCR4 in EMT. In conclusion, SDF-1/CXCR4 induces EMT of renal tubular epithelial cells with the involvement of the Wnt pathway, which may be a novel mechanism and therapeutic target in kidney allograft fibrosis of rats.

Experimental rat models of chronic allograft nephropathy: a review.

Chronic allograft nephropathy (CAN) is the leading cause of late allograft loss after renal transplantation (RT), which continues to remain an unresolved problem. A rat model of CAN was first described in 1969 by White et al. Although the rat model of RT can be technically challenging, it is attractive because the pathogenesis of CAN is similar to that following human RT and the pathological features of CAN develop within months as compared with years in human RT. The rat model of RT is considered as a useful investigational tool in the field of experimental transplantation research. We have reviewed the literature on studies of rat RT reporting the donor and recipient strain combinations that have investigated resultant survival and histological outcomes. Several different combinations of inbred and outbred rat combinations have been reported to investigate the multiple aspects of transplantation, including acute rejection, cellular and humoral rejection mechanisms and their treatments, CAN, and potential targets for its prevention.

Mesenchymal Stem Cell Therapy Prevents Interstitial Fibrosis and Tubular Atrophy in a Rat Kidney Allograft Model

In solid organ transplantation, mesenchymal stem cell (MSC) therapy is strongly emerging among other cell therapies due to the positive results obtained in vitro and in vivo as an immunomodulatory agent and their potential regenerative role. We aimed at testing whether a single dose of MSCs, injected at 11 weeks after kidney transplantation for the prevention of chronic mechanisms, enhanced regeneration and provided protection against the inflammatory and fibrotic processes that finally lead to the characteristic features of chronic allograft nephropathy (CAN). Either bone marrow mononuclear cells (BMCs) injection or no-therapy (NT) were used as control treatments. A rat kidney transplantation model of CAN with 2.5 h of cold ischemia was used, and functional, histological, and molecular parameters were assessed at 12 and 24 weeks after transplantation. MSC and BMC cell therapy preserves renal function at 24 weeks and abrogates proteinuria, which is typical of this model (NT24w: 68.9 ± 26.5 mg/24 h, MSC24w: 16.6 ± 2.3 mg/24 h, BMC24w: 24.1 ± 5.3 mg/24 h, P<0.03). Only MSC-treated animals showed a reduction in interstitial fibrosis and tubular atrophy (NT24w: 2.3 ± 0.29, MSC24w: 0.4 ± 0.2, P<0.03), less T cells (NT: 39.6 ± 9.5, MSC: 8.1 ± 0.9, P<0.03) and macrophages (NT: 20.9 ± 4.7, MSC: 5.9 ± 1.7, P<0.05) infiltrating the parenchyma and lowered expression of inflammatory cytokines while increasing the expression of anti-inflammatory factors. MSCs appear to serve as a protection from injury development rather than regenerate the damaged tissue, as no differences were observed in Ki67 expression, and kidney injury molecule-1, Clusterin, NGAL, and hepatocyte growth factor expression were only up-regulated in nontreated animals. Considering the results, a single delayed MSC injection is effective for the long-term protection of kidney allografts.

Delineating the Picture of Renal Graft Injury in 2011

To the Editor: We read with great interest this recent article entitled ‘The histology of Solitary Renal Allograft at 1 and 5 Years After Transplantation’ (1Stegall MD Park WD Larson TS et al.The histology of solitary renal allografts at 1 and 5 years after transplantation.Am J Transplant. 2011; 11: 698-707Abstract Full Text Full Text PDF PubMed Scopus (114) Google Scholar) published in AJT. In this paper, the authors show a dramatic reduction in renal allograft scarring lesions in the 5 years posttransplant, with moderate to severe fibrosis of 13% and 17% at 1 year and 5 years after transplantation, respectively, as compared to the results previously obtained by other groups (2Nankivell BJ Borrows RJ Fung CL O’Connell PJ Allen RD Chapman JR The natural history of chronic allograft nephropathy.N Engl J Med. 2003; 349: 2326-2333Crossref PubMed Scopus (1668) Google Scholar, 3Tantravahi J Womer KL Kaplan B Why hasn’t eliminating acute rejection improved graft survival?.Annu Rev Med. 2007; 58: 369-385Crossref PubMed Scopus (75) Google Scholar, 4Schwarz A Mengel M Gwinner W et al.Risk factors for chronic allograft nephropathy after renal transplantation: A protocol biopsy study.Kidney Int. 2005; 67: 341-348Abstract Full Text Full Text PDF PubMed Scopus (168) Google Scholar) including ours (5Legendre C Thervet E Skhiri H et al.Histologic features of chronic allograft nephropathy revealed by protocol biopsies in kidney transplant recipients.Transplantation. 1998; 65: 1506-1509Crossref PubMed Scopus (148) Google Scholar). Based on these findings, the authors suggest a ‘revised concept of histologic injury in which moderate-to-severe fibrosis and hyalinosis may be avoided in the majority of renal allografts in the first 5 years after transplantation’. We believe that this study, using a substantial number of protocol biopsies is relevant and improves our understanding of chronic allograft damage progression (2Nankivell BJ Borrows RJ Fung CL O’Connell PJ Allen RD Chapman JR The natural history of chronic allograft nephropathy.N Engl J Med. 2003; 349: 2326-2333Crossref PubMed Scopus (1668) Google Scholar), but should be interpreted with caution. In particular, the applicability of these results in nonselected populations of kidney transplant recipients (KTR) may not be valid since the study focuses on a highly selected population of stable KTR, mostly living donors, with low immunological risk and transplanted with a mean donor age of 41 years [below the average value obtained in Europe (6Agence de la Biomedecine Annual Report. Available at: http://www.agence-biomedecine.fr. Accessed April 2011.Google Scholar)]. Importantly, some methodological issues seem to be problematic: (i) first, the authors exclude from the analysis 219 patients who either lost function or were lost to follow-up before 5 years (flow chart, Figure 1). In a further analysis (supplementary Table 4), they claim that these groups of patients present similar chronicity Banff levels at 1 year (with the exception of cg) as compared to the 518 patients who reached 5 years. Of note, this analysis has been performed on only 107 of the 219 patients (49%) who did not reach 5 years, which may represent a bias in the group comparison. (ii) Second, the multivariate model may present potential weakness: the authors use in their model the variable ‘any complications’ mixing immunological with nonimmunological factors and containing variables that may not be independent [e.g., acute rejection and delayed graft function (2Nankivell BJ Borrows RJ Fung CL O’Connell PJ Allen RD Chapman JR The natural history of chronic allograft nephropathy.N Engl J Med. 2003; 349: 2326-2333Crossref PubMed Scopus (1668) Google Scholar) table 5]. Moreover, transplant glomerulopathy (cg) is used twice in the multivariate model: cg is part of the variable ‘1–5 years any complications’ and is also used in the 1 year chronicity score, which is methodologically not optimal. Finally, we believe, that the authors convincingly demonstrate the concept that stable kidneys with low immunological risk and from living donors reaching 5 years posttransplant have low chronicity scores, which is relevant information, but addresses only one part of the question. The next step would be to extend such analysis to large data sets of protocol biopsies of nonselected population of kidney recipients and importantly including the patients at risk that lose their kidney before 5 years. Such analysis would permit to assess the ‘overall’ picture of graft injury in 2011 and importantly the respective impacts represented by specific diseases such as ABMR, TCMR, disease recurrence in the process that contributes to chronic-allograft-damage represented by cv, cg, IFTA and ah lesions. The authors of this manuscript have no conflicts of interest to disclose as described by the American Journal of Transplantation.

Differential monocyte STAT6 activation and CD4 +CD25 +Foxp3 + T cells in kidney operational tolerance transplanted individuals

In organ transplantation, the immunosuppression withdrawal leads, in most cases, to rejection. Nonetheless, a special group of patients maintain stable graft function after complete withdrawal of immunosuppression, achieving a state called “operational tolerance.” The study of such patients may be important to understand the mechanisms involved in human transplantation tolerance. We compared the profile of CD4 +CD25 +Foxp3 + T cells and the signaling pathways IL-6/STAT3 (signal transducers and activators of transcription) and IL-4/STAT6 in peripheral blood mononuclear cells of four kidney transplant groups: (i) operational tolerance (OT), (ii) chronic allograft nephropathy (CR), (iii) stable graft function under standard immunosuppression (Sta), (iv) stable graft function under low immunosuppression, and (v) healthy individuals. Both CR and Sta displayed lower numbers and percentages of CD4 +CD25 +Foxp3 + T cells compared with all other groups ( p < 0.05). The OT patients displayed a reduced activation of the IL-4/STAT6 pathway in monocytes, compared with all other groups ( p < 0.05). The lower numbers of CD4 +CD25 +Foxp3 + T cells observed in CR individuals may be a feature of chronic allograft nephropathy. The differential OT signaling profile, with reduced phosphorylation of STAT6, in monocytes' region, suggests that some altered function of STAT6 signaling may be important for the operational tolerance state.

Protective Effects of FR167653 on Chronic Allograft Nephropathy by Inhibiting p38 MAPK in Rats

Background Chronic allograft nephropathy (CAN) remains a challenge for transplant clinicians. Some novel intervention strategies may shed new light on its treatment. Methods An orthotopic kidney transplant model in Fisher-to-Lewis rats was used with administration of cyclosporine alone or in combination with FR167653 (30 mg/kg/d subcuntaneously) to recipients. We analyzed renal function and urinary protein excretion. Animals were sacrificed at 30 weeks posttransplantation for histological and immunohistochemical studies. Results Renal function among vehicle-treated rats deteriorated progressively with substantial proteinuria compared with FR167653-treated rats. FR167653 administration significantly prevented the morphlogical features of CAN and prolonged rat survivals. p38 mitogen-activated protein kinase (MAPK) expression was markedly reduced by FR167653 treatment. Meanwhile, transforming growth factor-β1 and monocyte chemotactic protein-1 expression were significantly down-regulated among FR167653-treated hosts. Conclusion p38 MAPK phosphorylation correlated with CAN progression and inhibition of p38 MAPK by FR167653 may provide a potent novel therapeutic target for its prevention.

Quantification of Interstitial Fibrosis by Image Analysis on Routine Renal Biopsy 1 Year After Transplantation in Patients Managed by C 2 Monitoring of Cyclosporine Microemulsion

Background Renal interstitial fibrosis (IF), the main histopathologic feature of chronic allograft nephropathy (CAN), may be an important surrogate endpoint for patient follow-up. IF is currently assessed by semiquantitative analysis, but automatic color image analysis may be a more reliable, reproducible method to evaluate IF. We performed a retrospective analysis to calculate IF on routine renal biopsies 1 year after transplantation. Methods Data were obtained from MO2ART, a prospective multicenter trial in which the cyclosporine microemulsion dose was adjusted based on C 2 levels. We included 26 patients in whom routine renal biopsy at 1 year was available from two centers. For each biopsy, a section was analyzed by a program of color segmentation image that automatically extracted green-colored areas characteristic of IF. Results were expressed as percent IF and grade namely grade I, <25%; grade II, 25% to 50%; and grade III, >50%. The results were compared according to clinical and biological data. Results The 26 patients had a mean IF score of 0.35 ± 0.04. We observed 34.6% CAN grade I; 46.1%, grade II; and 19.2%, grade III. Serum creatinine at 3 years was greater in the higher grade of automated IF by repeated ANOVA. Conclusion Automatic quantification of IF on routine biopsy at 1 year after transplantation was predictive of renal outcome. This technique may provide an interesting tool for the early diagnosis of CAN after renal transplantation.

Protective Effects of Atorvastatin on Chronic Allograft Nephropathy in Rats

Chronic allograft nephropathy (CAN) is the leading cause of late kidney allograft loss. Recent studies have suggested that atorvastatin (ATO) may interact with the acute inflammatory process in the renal interstitium and suppress the proliferation of mesangial cells. We hypothesized that ATO could also inhibit the chronic inflammatory process and prevent the progression of CAN. Fisher (F344) kidneys were orthotopically transplanted into Lewis rat recipients. Lewis-to-Lewis rat kidney transplantation was served as the syngeneic control (Syn group). Allograft recipients were randomized and treated with cyclosporine A alone (Allo group) or in combination with ATO (15 or 30 mg/kg/d intrgastric, respectively, the low dose treatment group/high dose treatment group [LT/HT] groups). Renal function and the urine protein excretion were analyzed. Animals were sacrificed 20 weeks posttransplantation for histological and immunohistochemical studies, as well as analysis of mRNA levels of cytokines and chemokines. Renal function progressively deteriorated and substantial proteinuria developed in the Allo group compared with the Syn group. ATO-treated rats had significantly higher creatinine clearance rate and less amount of proteinuria. Histological examination revealed obvious features of CAN in the Allo group, whereas LT/HT groups demonstrated minimal glomerulosclerosis, interstitial fibrosis, intimal thickening, and tubular atrophy. The numbers of infiltrating mononuclear cells (ED1+, CD8+, and CD68+) decreased markedly, and the intragraft expression of transforming growth factor beta1 (TGF-beta1) and collagen III were also significantly attenuated in the LT/HT groups, as compared with the Allo group. The mRNA levels of proinflammatory cytokines (interleukin-2, interferon-gamma, interleukin-10), chemokines (RANTES, MCP-1), and profibrotic genes (TGF-beta1, collagen III) were significantly down-regulated in ATO-treated rats. Atorvastatin showed excellent favorable effects on blocking renal inflammation and fibrosis, and thus, efficiently inhibited the development and progression of CAN, which might improve the long-term survival rate of renal allografts.

HGF gene therapy attenuates renal allograft scarring by preventing the profibrotic inflammatory-induced mechanisms

Inflammatory processes and tissue scarring are characteristic features of chronic allograft nephropathy. Hepatocyte growth factor (HGF) has beneficial effects on renal fibrosis and it also ameliorates renal interstitial inflammation as it has been recently described. Contrarily to protein administration, intramuscular gene electrotransfer allows sustained release of HGF. So, here we hypothesized that gene therapy with human HGF would diminish the characteristic scarring of chronic allograft nephropathy either by antagonizing tissue fibrosis mechanisms or by reducing inflammation. Lewis rats transplanted with cold preserved Fischer kidneys received vehicle (NoHGF) or intramuscular plasmid DNA encoding HGF plus electroporation either before transplantation (IniHGF, early post-transplant cytoprotection of tubular cells) or 8/10 weeks after transplantation (DelHGF, delayed prevention of chronic mechanisms). Serum creatinine and proteinuria were measured every 4 weeks for 24 weeks. Grafts at 12 or 24 weeks were evaluated for glomerulosclerosis, fibrosis inflammatory cells and mediators, cell regeneration and tubulo-interstitial damage. Nontreated animals developed renal insufficiency, progressive proteinuria and fibrosis among other characteristic histological features of chronic allograft nephropathy. Treatment with human HGF, especially when delayed until the onset of fibrogenic mechanisms, reduced renal failure and mortality, diminished tubule-interstitial damage, induced cell regeneration, decreased inflammation, NF-kappaB activation, and profibrotic markers at 12 weeks and prevented late interstitial fibrosis and glomerulosclerosis. The effectiveness of HGF-gene therapy in the prevention of renal allograft scarring is related with the halt of profibrotic inflammatory-induced mechanisms.

Chronic rejection of human kidney allografts

Human chronic rejection is an uncommon feature of chronic allograft nephropathy, the major cause of late graft loss in kidney transplantation. Chronic rejection is a complex process, mediated, at least in part, by immunological mechanisms. T cells with donor, tissue or pathogen specificities that react with donor cells damage the graft tissue in synergy with antibodies. The cellular and humoral components of the immune system may be preformed or appear at both early and late time points following kidney transplantation. Both slowly contribute to the development of vasculopathy, glomerulopathy, tubular atrophy and tissue fibrosis, as observed in chronic rejection biopsies. Characterization of the blood transcriptome of patients prone to develop chronic rejection is an objective that may soon be achieved. However, despite increasing knowledge of the pathogenesis of late allograft failure and advances in the identification of patients at high risk, chronic rejection remains poorly responsive to immunosuppressive treatment, reinforcing the implication of both immune and nonimmune causes. Efforts aimed at diminishing the incidence of risk factors, such as acute rejection episodes, transplantation injury and human leukocyte antigen mismatching, and at controlling inflammation and scar processes, are thus important in chronic rejection prevention and control.

TGF-β1 mRNA upregulation influences chronic renal allograft dysfunction

Acute rejection (AR) is a dominant risk factor for developing chronic allograft nephropathy (CAN) after kidney transplantation. CAN is characterized by progressive interstitial fibrosis. It has been associated with increased transforming growth factor (TGF)-beta1 expression, however, kinetic studies are absent. We investigated whether intragraft TGF-beta1 expression in various causes of early graft dysfunction may influence late renal allograft dysfunction. A total of 174 human renal biopsies were quantified for TGF-beta1 mRNA expression using real-time reverse transcriptase-polymerase chain reaction. Expression levels were correlated with the Banff histopathological grades, TGF-beta1 immunohistology, and clinical follow-up. TGF-beta1 was most markedly upregulated in AR, CAN, and acute tubular necrosis - delayed graft function compared to non-rejecting controls (P < 0.001). TGF-beta1 expression was heightened in borderline changes (P < 0.01), recurrence of glomerulonephritis, and cyclosporine toxicity (P < 0.05). There was no correlation between intragraft TGF-beta1 expression during AR and short-term outcome of a rejection episode. TGF-beta1 gene overexpression during CAN has been shown to be associated with the increased risk for renal allograft dysfunction 18 months after biopsy (odds ratios 9.9 vs 3.2, respectively). Intragraft TGF-beta1 mRNA expression is significantly upregulated in both AR and CAN. Thus, our results support the hypothesis that TGF-beta1 might play a key role in chronic allograft dysfunction.

Recurrent nephrotic syndrome after living‐related renal transplantation resistant to plasma exchange: report of two cases

We encountered two patients of recurrent nephrotic syndrome (NS) after renal transplantation that was resistant to plasma exchange (PEX). Case 1 was a 34-year-old man with a living-related renal transplant for type-I membranoproliferative glomerulonephritis (MPGN) related end-stage renal disease (ESRD). He developed overt proteinuria 7 months post-transplant and presented with NS 5 months later. Biopsy of the transplant kidney revealed recurrent type I MPGN, but no features of acute rejection (AR) or chronic allograft nephropathy (CAN). He was treated with cyclophosphamide (CP), oral prednisolone (40 mg/d), an anti-platelet agent, heparin sulfate, and PEX, but the nephrotic state persisted and renal function was deteriorated. He recommenced hemodialysis 3 yr and 9 months after renal transplant. Case 2 was a 47-year-old male who underwent living-related renal transplant for ESRD due to focal segmental glomerulosclerosis (FSGS). He presented with proteinuria shortly after renal transplantation. He also had frequent episodes of AR. Graft biopsy revealed recurrent FSGS. Treatment of pulse methylprednisolone and PEX was transiently effective, but NS relapsed shortly after PEX. Graft biopsy at our hospital showed features of CAN with moderate interstitial fibrosis and tubular atrophy, presence of intraglomerular foam cells but no segmental sclerosis. Treatment with 12 courses of low-density lipoprotein apheresis (LDL-A) reduced proteinuria from 9.6 to 2.0 g/d, and incomplete remission has been maintained for more than 1 yr after LDL-A with slowly progressive renal dysfunction. Despite recent therapeutic advances, including the use of immunosuppressants and PEX, treatment of recurrent disease remains difficult. The LDL-A might be useful in cases with recurrent FSGS resistant to PEX.

Heat Shock Protein 27 in Chronic Allograft Nephropathy: A Local Stress Response

Heat shock protein (HSP) 27 plays a cytoprotective role through its antioxidant, antiapoptotic, and actin-stabilizing properties during cell stress. The authors hypothesized that HSP27 is involved in chronic allograft nephropathy (CAN), a chronic state of inflammation and stress. The authors used the Fisher 344-to-Lewis model of CAN. Transplants were performed in 3-month-old recipient rats. HSP27 mRNA and protein levels were determined using semiquantitative polymerase chain reaction, microarray (stress-toxicity, GEArray) analyses, gene sequencing, immunoblotting, and immunohistochemical analyses at 10 days and 6 months posttransplant. P38 mitogen-activated protein kinase (MAPK), manganese (Mn) superoxide dismutase (SOD), copper-zinc (CuZn) SOD, FasL, Bax, hypoxia-inducible factor (HIF)-1alpha, and CD3 lymphocytes were studied in parallel as selective biomarkers of oxidative stress (OS), apoptosis, hypoxia, and graft-infiltrating immune cells. Six months after transplantation, kidney allografts displayed histologic and functional features of CAN, including tubular atrophy, interstitial fibrosis, glomerulosclerosis, and increased proteinuria and serum creatinine levels. HSP27 mRNA and protein levels in CAN were reduced by 50% and 85%, respectively (P=0.04). Immunohistochemical analyses revealed a "shift" in HSP27 from the medulla to the cortex in allografts with CAN. Bax, phosphorylated p38-MAPK, HIF-1alpha, and MnSOD followed a parallel relocation pattern. CD3 lymphocyte density and tubular FasL expression were also greater in the cortex of allografts with CAN. Time-course analyses revealed that most of these changes were present as early as 10 days posttransplant. The shift of HSP27 from the medulla to the cortex, combined with greater CD3, p38-MAPK, Bax, FasL, HIF-1alpha, and MnSOD immunoreactivity in this area of the kidney, likely represents an allograft-level response to CAN-related OS-hypoxia.

Capillary Deposition of Complement C4d and C3d in Pediatric Renal Allograft Biopsies

Peritubular capillary deposition of C4d (C4d(PTC)) is a marker of antibody-mediated alloresponse and is associated with poor graft survival in adults. C3d(PTC) has received less attention; its significance is unclear. To date no information has been gained in children. The prevalence of C4d(PTC) and C3d(PTC) in pediatric renal allograft biopsies (n=77, 31 cadaveric kidneys) was analyzed retrospectively. Associations with histology, donor-specific antibodies (DSAs), and outcome were investigated. The overall prevalence of C4d(PTC) and C3d(PTC) was 52% and 48%, respectively. C3d(PTC) was associated with C4d(PTC) (P<0.0001). Thirty-six percent of acute rejections were cellular, 28% were humoral, and 36% were combined cellular and humoral. C3d(PTC) was found in 57% of acute rejection biopsies. C4d(PTC), but not C3d(PTC), was associated with accumulation of polymorphonuclear cells in peritubular capillaries (P=0.02). Fifty-one percent of late biopsies (>6 months posttransplantation) had features of chronic allograft nephropathy: 50% were C4d(PTC_ positive, and 50% were C3d(PTC) positive. C4d(PTC) positive chronic allograft nephropathy biopsies had more transplant glomerulopathy (P=0.020) and mesangial matrix increase (P=0.026). C3d(PTC) tended to be associated with transplant glomerulopathy (P=0.06), but not with mesangial matrix increase. C4d(PTC) was correlated with DSA (P=0.011). Excluding early nonrejection graft losses, more grafts were lost in the C4d(PTC) positive group (P=0.019). C3d(PTC) was not associated with DSA or graft outcome. Our results support C4d(PTC) being a hallmark of humoral rejection in pediatric renal transplantation; its presence was associated with DSA and poorer immunologic graft outcome. In contrast, C3d(PTC), although highly associated with C4d(PTC), did not correlate with DSA or outcome.

POSTTRANSPLANT DE NOVO MEMBRANOUS NEPHROPATHY IN CHILDHOOD

Posttransplant proteinuria is a recognized, but relatively uncommon, presentation of renal transplant dysfunction. Significant proteinuria occurs in around 10–15% of renal transplant recipients. We present a case of de novo posttransplant membranous nephropathy in childhood complicating renal transplantation for severe congenital obstructive uropathy and review the pathology, pathogenesis, and clinical implications of this condition.In the majority of cases, the cause of posttransplant proteinuria is either related to chronic allograft nephropathy or recurrence of the glomerulonephritis for which transplantation was indicated. In a minority, however, de novo posttransplant membranous nephropathy (DNPMN) is identified on biopsy. The histopathological findings in some cases may either be similar to those of classical membranous nephropathy, or may be more subtle, showing focal segmental variation in severity, often in conjuction with the features of chronic allograft nephropathy. The use of ancillary techniques including immunohistochemistry and electron microscopy may be required to confirm the diagnosis. The presence of posttransplant de novo membranous nephropathy may be associated with an increased risk of graft loss.

Histological features with clinical impact in chronic allograft nephropathy: review of 66 cases

The histological features of chronic allograft nephropathy (CAN) are variable, since it is related to multiple donor and recipient factors. The main histological parameters in CAN are interstitial fibrosis, tubular atrophy, chronic vasculopathy and glomerulosclerosis. There have been many attempts to relate chronic deterioration of renal function with histologic features. Materials and methodsWe reviewed 66 kidney transplant patients (43 men/23 women) with renal failure 6 months after transplant. The clinical data included donor and recipient age, cold ischemia time, delayed graft function (DGF), creatinine clearance, proteinuria, HLA compatibility, CMV infection, cholesterol levels, diastolic and systolic blood pressure. Banff criteria were used to grade histological parameters. The relation between clinical and histological data were analyzed using chi square, Student t, Mann Whitney and Kruskal-Wallis tests as appropriate. The cumulative graft and patient survival rates were calculated by the Kaplan-Meier method. ResultsThe survival rate of patients with creatinine clearances >3 mg/dL at the time of the biopsy was worse than that of patients with creatinine <3 mg/dL (P = .001; log rank 20.1). We found an association between the grade of arteriosclerosis and the diastolic blood pressure (P = .017). The creatinine level was greater among patients with tabulitis than those without tubulitis (P = .06). In addition to our results we review the literature especially related to the histological feature of CAN in an attempt to detect histological findings predicitive of the long term outcome of kidney allografts.

Oxidative Stress and Chronic Allograft Nephropathy

Oxidative stress defined as outbalanced generation of reactive oxygen species (ROS) than the existing antioxidative defense mechanisms plays an important role in tissue injury. Ischemia/reperfusion accompanied during organ transplantation is well- established oxidative stress-induced tissue injury. We hypothesized that oxidative stress may also play a role in the development and progression of chronic allograft nephropathy (CAN), since that ROS are major signaling molecules of growth factors and cytokines [platelet-derived growth factors, transforming growth factor-beta1(TGF-beta1)] upregulated in the kidney of CAN, that ROS in turn upregulate TGF-beta1, and that mycophenolic acid may inhibit features of CAN [proliferation and extracellular matrix (ECM) accumulation in vascular smooth muscle cells and glomerular mesangial cells] through inhibiting cellular ROS. Cellular ROS activate signal transduction cascade (protein kinase C, mitogen-activated protein kinases, and janus kinases) and transcription factors (nuclear factor-kappaB, activated protein-1, specificity protein 1, and signal transducers and activators of transcription) leading to regulation of genes and proteins involved in cellular proliferation, ECM remodeling, and apoptosis accompanied in CAN. This review is intended to provide an overview of oxidative stress in renal allograft nephropathy.

Capillary deposition of complement split product C4d in renal allografts is associated with basement membrane injury in peritubular and glomerular capillaries: a contribution of humoral immunity to chronic allograft rejection.

Endothelial deposition of the complement split product C4d is an established marker of antibody-mediated acute renal allograft rejection. A contribution of alloantibody-dependent immune reactions to chronic rejection is under discussion. In this study, the association of immunohistochemically detected endothelial C4d deposition in peritubular capillaries (PTC) with morphologic features of chronic renal allograft injury was investigated in a large study cohort. C4d deposits in PTC were detected in 73 (34%) of 213 late allograft biopsies performed in 213 patients more than 12 mo after transplantation (median, 4.9 yr) because of chronic allograft dysfunction. Endothelial C4d deposition was found to be associated with chronic transplant glomerulopathy (CG) (P < 0.0001), with basement membrane multilayering in PTC (P = 0.01), and with an accumulation of mononuclear inflammatory cells in PTC (P < 0,001). Furthermore, C4d deposits in PTC (in biopsies with normal glomerular morphology) were associated with development of CG in follow-up biopsies. Other morphologic features of chronic allograft nephropathy (with exception of tubular atrophy) were not associated with C4d deposits in PTC. Analyses of previous and follow-up biopsies revealed that C4d deposits may occur de novo and may also disappear at any time after transplantation. In conclusion, the data suggest that complement activation in renal microvasculature, indicating humoral alloreactivity, contributes to chronic rejection characterized by chronic transplant glomerulopathy and basement membrane multilayering in PTC.

The role of transforming growth factor beta in chronic renal allograft nephropathy.

The role of transforming growth factor beta in chronic renal allograft nephropathy.

Plasma cell-rich acute renal allograft rejection.

Acute renal allograft rejection is usually seen within the first 3 months posttransplant, and is characterized by an intense infiltrate of T cells. Some acute rejections, however, contain many plasma cells and/or appear late posttransplant. We have investigated 27 cases of intensely plasma cell-rich acute rejections (PCAR) from 1987 to 1997 and have compared them to 21 control cases (CAR) of typical acute rejection. Each group was divided into early (<6 months) and late (>6 months) subgroups. PCAR and CAR cases were matched for histological features of chronic allograft nephropathy. In all four groups, most cases had Banff '97 type IB and IIA acute rejection. A significantly greater number of PCAR cases experienced graft failure due to chronic allograft nephropathy or complications of acute rejection (P<0.05). There was no significant difference between PCAR and CAR in HLA matching, occurrence of posttransplant acute tubular necrosis, presence versus absence of previous allografts, number of previous or subsequent acute rejection episodes, Banff '97 sum scores for acute rejection, cyclosporine A or FK506 levels, or percent change from baseline creatinine at time of biopsy. Plasma cells in PCAR cases showed IgG predominance whereas those in CAR had comparable staining for IgG and IgA. Kappa and lambda light chain immunostaining of all PCAR cases revealed polyclonality. Three of 18 PCAR cases studied for the presence of Epstein-Barr virus RNA showed scattered positivity in 2-7% of lymphoid cells, although the remainder was negative. None of the PCAR cases developed post-transpland lymphoproliferative disorder. We conclude that PCAR can occur from 1 month to many years posttransplant, is associated with poor graft survival, and is not a manifestation of concomitant chronic allograft nephropathy or viral infection, including posttransplant lymphoproliferative disorder.