Unique changes in interstitial extracellular matrix composition are associated with rejection and cyclosporine toxicity in human renal allograft biopsies

Alternative splicing of CEACAM1 by hypoxia-inducible factor-1α enhances tolerance to hepatic ischemia in mice and humans

Although alternative splicing (AS) drives transcriptional responses and cellular adaptation to environmental stresses, its contributions in organ transplantation have not been appreciated. We have shown that carcinoembryonic antigen-related cell adhesion molecule (Ceacam1; CD66a), a transmembrane biliary glycoprotein expressed in epithelial, endothelial, and immune cells, determines donor liver transplant quality. Here, we studied how AS of Ceacam1 affects ischemia-reperfusion injury (IRI) in mouse and human livers. We found that the short cytoplasmic isoform Ceacam1-S increased during early acute and late resolution phases of warm IRI injury in mice. Transfection of Ceacam1-deficient mouse hepatocytes with adenoviral Ceacam1-S mitigated hypoxia-induced loss of cellular adhesion by repressing the Ask1/p-p38 cell death pathway. Nucleic acid-blocking morpholinos, designed to selectively induce Ceacam1-S, protected hepatocyte cultures against temperature-induced stress in vitro. Luciferase and chromatin immunoprecipitation assays identified direct binding of hypoxia-inducible factor-1α (Hif-1α) to the mouse polypyrimidine tract binding protein 1 (Ptbp1) promoter region. Dimethyloxalylglycine protected mouse livers from warm IR stress and hepatocellular damage by inhibiting prolyl hydroxylase domain-containing protein 1 and promoting AS of Ceacam1-S. Last, analysis of 46 human donor liver grafts revealed that CEACAM1-S positively correlated with pretransplant HIF1A expression. This also correlated with better transplant outcomes, including reduced TIMP1, total bilirubin, proinflammatory MCP1, CXCL10 cytokines, immune activation markers IL17A, and incidence of delayed complications from biliary anastomosis. This translational study identified mouse Hif-1α-controlled AS of Ceacam1, through transcriptional regulation of Ptbp1 promoter region, as a functional underpinning of hepatoprotection against IR stress and tissue damage in liver transplantation.

Artificial intelligence and algorithmic computational pathology: an introduction with renal allograft examples

Whole slide imaging, which is an important technique in the field of digital pathology, has recently been the subject of increased interest and avenues for utilisation, and with more widespread whole slide image (WSI) utilisation, there will also be increased interest in and implementation of image analysis (IA) techniques. IA includes artificial intelligence (AI) and targeted or hypothesis-driven algorithms. In the overall pathology field, the number of citations related to these topics has increased in recent years. Renal pathology is one anatomical pathology subspecialty that has utilised WSIs and IA algorithms; it can be argued that renal transplant pathology could be particularly suited for whole slide imaging and IA, as renal transplant pathology is frequently classified by use of the semiquantitative Banff classification of renal allograft pathology. Hypothesis-driven/targeted algorithms have been used in the past for the assessment of a variety of features in the kidney (e.g. interstitial fibrosis, tubular atrophy, inflammation); in recent years, the amount of research has particularly increased in the area of AI/machine learning for the identification of glomeruli, for histological segmentation, and for other applications. Deep learning is the form of machine learning that is most often used for such AI approaches to the 'big data' of pathology WSIs, and deep learning methods such as artificial neural networks (ANNs)/convolutional neural networks (CNNs) are utilised. Unsupervised and supervised AI algorithms can be employed to accomplish image or semantic classification. In this review, AI and other IA algorithms applied to WSIs are discussed, and examples from renal pathology are covered, with an emphasis on renal transplant pathology.

Chronic allograft nephropathy or interstitial fibrosis and tubular atrophy: what is in a name?

PURPOSE OF REVIEW

Chronic allograft nephropathy has fallen into disfavor as a morphologic term to describe parenchymal scarring in the renal allograft, with a recommendation that this be replaced by the more descriptive term 'interstitial fibrosis and tubular atrophy'. However, neither term addresses the underlying cause of the scarring. This review focuses on whether all interstitial fibrosis and tubular atrophy in the renal allograft has the same implications for long-term graft survival, and whether there are specific features of interstitial fibrosis and tubular atrophy that can be used to identify its underlying cause.

RECENT FINDINGS

Results from a number of studies indicate that interstitial fibrosis and tubular atrophy, when associated with interstitial inflammation, is a strong predictor of graft loss, much more so than interstitial fibrosis and tubular atrophy alone. Most notably, findings from the multicenter Long-Term Deterioration of Kidney Allograft Function study, designed to identify the causes of late allograft dysfunction, showed interstitial inflammation in the areas of interstitial fibrosis and tubular atrophy (i-IF/TA) was predictive of reduced time to graft failure, even after adjustment for serum creatinine. In addition, the presence of i-IF/TA correlates with increased acute kidney injury gene transcripts. However, neither interstitial fibrosis and tubular atrophy nor i-IF/TA is associated with any specific cause of chronic graft injury.

SUMMARY

Although (i-IF/TA), especially when widespread, is clearly associated with reduced renal allograft survival and molecular markers of active graft injury and repair, there is presently no reliable way, using either morphology alone, immunohistochemistry, or molecular techniques, to differentiate i-IF/TA (or interstitial fibrosis and tubular atrophy alone) resulting from different causes.

Banff fibrosis study: multicenter visual assessment and computerized analysis of interstitial fibrosis in kidney biopsies

Increasing interstitial fibrosis (IF) in native and kidney transplant biopsies is associated with functional decline and serves as a clinical trial end point. A Banff 2009 Conference survey revealed a range in IF assessment practices. Observers from multiple centers were asked to assess 30 renal biopsies with a range of IF and quantitate IF using two approaches on trichrome, Periodic acid-Schiff (PAS) and computer-assisted quantification of collagen III immunohistochemistry (C-IHC) slides, as well as assessing percent of cortical tubular atrophy% (TA%) and Banff total cortical inflammation score (ti-score). C-IHC using whole slide scans was performed. C-IHC assessment showed a higher correlation with organ function (r = -0.48) than did visual assessments (r = -0.32--0.42); computerized and visual C-IHC assessment also correlated (r = 0.64-0.66). Visual assessment of trichrome and C-IHC showed better correlations with organ function and C-IHC, than PAS, TA% and ti-score. However, visual assessment of IF, independent of approach, was variable among observers, and differences in correlations with organ function were not statistically significant among C-IHC image analysis and visual assessment methods. C-IHC image analysis correlated among three centers (r > 0.90, p < 0.0001, between all centers). Given the difficulty of visual IF assessment standardization, C-IHC image could potentially accomplish standardized IF assessment in multicenter settings.

The KUPNetViz: a biological network viewer for multiple -omics datasets in kidney diseases

Background

Constant technological advances have allowed scientists in biology to migrate from conventional single-omics to multi-omics experimental approaches, challenging bioinformatics to bridge this multi-tiered information. Ongoing research in renal biology is no exception. The results of large-scale and/or high throughput experiments, presenting a wealth of information on kidney disease are scattered across the web. To tackle this problem, we recently presented the KUPKB, a multi-omics data repository for renal diseases.

Results

In this article, we describe KUPNetViz, a biological graph exploration tool allowing the exploration of KUPKB data through the visualization of biomolecule interactions. KUPNetViz enables the integration of multi-layered experimental data over different species, renal locations and renal diseases to protein-protein interaction networks and allows association with biological functions, biochemical pathways and other functional elements such as miRNAs. KUPNetViz focuses on the simplicity of its usage and the clarity of resulting networks by reducing and/or automating advanced functionalities present in other biological network visualization packages. In addition, it allows the extrapolation of biomolecule interactions across different species, leading to the formulations of new plausible hypotheses, adequate experiment design and to the suggestion of novel biological mechanisms. We demonstrate the value of KUPNetViz by two usage examples: the integration of calreticulin as a key player in a larger interaction network in renal graft rejection and the novel observation of the strong association of interleukin-6 with polycystic kidney disease.

Conclusions

The KUPNetViz is an interactive and flexible biological network visualization and exploration tool. It provides renal biologists with biological network snapshots of the complex integrated data of the KUPKB allowing the formulation of new hypotheses in a user friendly manner.

Donor age and ABCB1 1199G>A genetic polymorphism are independent factors affecting long-term renal function after kidney transplantation

BACKGROUND

In renal tubular cells, cytochrome P4503A enzyme and adenosine triphosphate-binding cassette transporter activities result in intracellular drug or metabolite exposure variability, depending on genetic polymorphisms. Our aim was to establish whether long-term renal function is affected by genetic polymorphisms in biotransformation enzymes and drug transporters of the donor after kidney transplantation.

MATERIALS AND METHODS

The study was conducted in a selected cohort of 97 kidney recipients. Genotyping of donors was performed on renal biopsy samples obtained before transplantation. Serum creatinine levels and Cockcroft-Gault estimated glomerular filtration rate were considered 1 y after transplantation and at the last follow-up.

RESULTS

Long-term function was significantly better in recipients of an organ from donors carrying the ABCB1 1199A mutated allele (median and range creatinine values were 1.1 mg/dL [0.8-1.5mg/dL] in case of at least one ABCB1 1199A allele versus 1.5 mg/dL [0.7-3.7 mg/dL] for homozygous carriers of wild-type allele, P < 0.01). ABCB1 1199G>A polymorphism and donor age had an independent impact on both serum creatinine and estimated glomerular filtration rate. Unlike donor age, the mutated ABCB1 1199A allele was found to have a protective effect on renal function.

CONCLUSIONS

Donor age and ABCB1 1199G>A polymorphism affect long-term renal function after transplantation. Analysis of genetic factors offers a promising approach to calcineurin inhibitor toxicity risk assessment.

Renal interstitial fibrosis: mechanisms and evaluation

PURPOSE OF REVIEW

Tubulointerstitial injury in the kidney is complex, involving a number of independent and overlapping cellular and molecular pathways, with renal interstitial fibrosis and tubular atrophy (IFTA) as the final common pathway. Furthermore, there are multiple ways to assess IFTA.

RECENT FINDINGS

Cells involved include tubular epithelial cells, fibroblasts, fibrocytes, myofibroblasts, monocyte/macrophages, and mast cells with complex and still incompletely characterized cell-molecular interactions. Molecular mediators involved are numerous and involve pathways such as transforming growth factor (TGF)-β, bone morphogenic protein (BMP), platelet-derived growth factor (PDGF), and hepatocyte growth factor (HGF). Recent genomic approaches have shed insight into some of these cellular and molecular pathways. Pathologic evaluation of IFTA is central in assessing the severity of chronic disease; however, there are a variety of methods used to assess IFTA. Most assessment of IFTA relies on pathologist assessment of special stains such as trichrome, Sirius Red, and collagen III immunohistochemistry. Visual pathologist assessment can be prone to intra and interobserver variability, but some methods employ computerized morphometery, without a clear consensus as to the best method.

SUMMARY

IFTA results from on orchestration of cell types and molecular pathways. Opinions vary on the optimal qualitative and quantitative assessment of IFTA.

Laminin alpha4-null mutant mice develop chronic kidney disease with persistent overexpression of platelet-derived growth factor

Each extracellular matrix compartment in the kidney has a unique composition, with regional specificity in the expression of various laminin isoforms. Although null mutations in the majority of laminin chains lead to specific developmental abnormalities in the kidney, Lama4-/- mice have progressive glomerular and tubulointerstitial fibrosis. These mice have a significant increase in expression of platelet-derived growth factor (PDGF)-BB, PDGF-DD, and PDGF receptor beta in association with immature glomerular and peritubular capillaries. In addition, mesangial cell exposure to alpha4-containing laminins, but not other isoforms, results in down-regulation of PDGF receptor mRNA and protein, suggesting a direct effect of LN411/LN421 on vessel maturation. Given the known role of overexpression of PDGF-BB and PDGF-DD on glomerular and tubulointerstitial fibrosis, these data suggest that failure of laminin alpha4-mediated down-regulation of PDGF activity contributes to the progressive renal lesions in this animal model. Given the recent demonstration that individuals with laminin alpha4 mutations develop cardiomyopathy, these findings may be relevant to kidney disease in humans.

Biotransformation enzymes and drug transporters pharmacogenetics in relation to immunosuppressive drugs: impact on pharmacokinetics and clinical outcome

Immunosuppressive drugs commonly used after organ transplantation to prevent acute rejection including tacrolimus, cyclosporine, sirolimus, and mycophenolic acid are characterized by a narrow therapeutic index and broad interindividual variability in their pharmacokinetics. Adequate immunosuppression aims to reach an optimal benefit-risk ratio. Therapeutic drug monitoring represents a crucial step in routine practice to maintain blood concentrations within the target window, because the bioavailability of these drugs depends on their absorption, distribution, biotransformation, and elimination. Single nucleotide polymorphisms (SNPs) in genes encoding biotransformation enzymes (CYP3A) and drug transporters (ABCB1) have opened up a promising way for the selection of individual dosages. The relationship of these SNPs with immunosuppressive drug pharmacokinetics was extensively studied after kidney, liver, heart, and lung transplantations. Patient susceptibility to nephrotoxicity in the long term was also reported in relation to some SNPs, which could allow effective assessment of individual risk and selection of treatment according to patient parameters. Further studies are needed to provide evidence that a genetic analysis combined with therapeutic drug monitoring has the potential to optimize drug use after transplantation.

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.

Posttransplantation chronic renal damage in nonrenal transplant recipients

BACKGROUND

The growing problem of relentless deterioration of renal function in patients who undergo transplantation of nonrenal solid organs is bound to have an increasingly important impact as it may not only worsen patient morbidity and mortality but also increase transplantation costs.

METHODS

We reviewed the literature in order to provide a sum of the most important data on the incidence, clinical picture, renal pathology pattern, damage mechanisms, and risk factors, along with strategies for prevention and treatment of chronic renal damage following nonrenal solid organ transplantation.

RESULTS

Literature data report that 10% to 80% of transplanted patients have some degree of renal dysfunction and that they share a common clinical picture characterized by relentless asymptomatic progression, frequent hypertension, mild urinary abnormalities, and pathology features of vascular, glomerular, tubular, and interstitial involvement. These changes are very similar to those reported for chronic nephrotoxicity from calcineurin inhibitors. The occurrence of end-stage renal disease (ESRD) requiring chronic dialysis has been reported in up to 20% of nonrenal transplant recipients. Although there are some organ-specific differences, a group of common risk factors has been recognized, including the use of calcineurin inhibitors as immunosuppressive agents, age, pretransplantation renal function, intraoperative/perioperative factors, concomitant use of other nephrotoxic drugs, infections, and posttransplantation acute renal failure.

CONCLUSION

Calcineurin inhibitor-induced nephrotoxicity is a growing problem and, as the age of recipients of nonrenal organs is increasing, this problem is destined to increase. It would therefore be advisable for nephrologists to share their experiences in immunomodulation with other specialties, so as to favor the cautious extension of calcineurin inhibitor-sparing protocols to the area of life-saving transplants.

The use of extracellular matrix probes and extracellular matrix-related probes for assessing diagnosis and prognosis in renal diseases

PURPOSE OF REVIEW

Scarring in the kidney results from excessive local synthesis and exogenous accumulation of extracellular matrix components. Once chronic damage is present in the biopsy, therapeutic intervention for the renal patient encounters severe limitations. It is therefore essential to determine clinical outcome preferably at a time point before the development of overt scarring. Clinical parameters and morphologic alterations in the biopsy are currently used as tools for the diagnosis of the renal disease entity and for assessment of the patient's prognosis. Expression levels of extracellular matrix and matrix-related components may serve as additive and even superior prognostic indicators to conventional parameters. We will elaborate on studies supporting this concept.

RECENT FINDINGS

Several investigators have shown in experimental models for renal disease that extracellular matrix probes and related probes reflect disease progression and predict outcome. In this review, we will provide an update on the most recent studies of human renal biopsies showing that expression of extracellular matrix components, regulators of matrix degradation, and cytokines affecting matrix deposition may be employed for discrimination of diagnostic groups and predicting prognosis.

SUMMARY

Molecular techniques are expected to be used more and more for diagnostic and prognostic purposes in nephrological practice to supplement the histopathological analysis of the renal biopsy. Assessment of expression of matrix molecules, matrix-regulating cytokines, and metalloproteinases in renal kidney biopsies is helpful to distinguish patients who are at risk of developing progressive renal failure from patients who are likely to recover from renal tissue injury by natural remodeling mechanisms.

Ochratoxin A-induced renal cortex fibrosis and epithelial-to-mesenchymal transition: molecular mechanisms of ochratoxin A-injury and potential effects of red wine

We characterized the effect of chronic ochratoxin A (OTA) on rat kidney cortex, analyzing collagen content and collagen turnover and the major markers of epithelial-to-mesenchymal transition (EMT), such as alpha-smooth muscle actin (alphaSMA), cadherins, and MMP-9. Because OTA nephrotoxicity is mediated by free radicals, we also investigated whether antioxidants in red wine provided protection for the kidney and attenuated OTA-induced EMT. Collagen content, determined by computerized analysis of Sirius red-stained kidney sections, increased in OTA, OTA-wine, and OTA-EtOH treated rats. In kidney cortex homogenates, COL-I and COL-III mRNA levels tended to rise in OTA treated rats, but were similar to CT after OTA-wine and OTA-EtOH administration. TIMP-1 gene expression was up-regulated in OTA, OTA-wine, and OTA-EtOH treated rats. LH2b mRNA/COL-I mRNA was significantly up-regulated in OTA-wine and OTA-EtOH treated rats, compared with CT and OTA alone. TGF-beta1 signaling tended to dominate after OTA, OTA-wine, and OTA-EtOH. MMP-1 protein levels were not affected. OTA induced proMMP-9 and alphaSMA overexpression, decreases of E-cadherin and N-cadherin, and DSC-2 up-regulation. OTA-wine caused a further, unexpected decrease of E- and N-cadherins and further up-regulation of OTA-induced DSC-2, while strongly reducing the OTA-induced increases of alphaSMA and proMMP-9. Posttranslational collagen modifications, such as decreased collagen degradation through MMP inhibition and increased collagen cross-links, seem to be key mechanisms leading to OTA-induced kidney cortex fibrosis. This mechanism was not affected by red wine in these conditions. Red wine seems to have some protective role against OTA-induced EMT, although without completely blocking the process and determining a condition in which abundant cells display an intermediate translational phenotype, but there are no alphaSMA or epithelial markers.

In vitro metabolism of cyclosporine A by human kidney CYP3A5

The objectives of this study were to characterize and compare the metabolic profile of cyclosporine A (CsA) catalyzed by CYP3A4, CYP3A5 and human kidney and liver microsomes, and to evaluate the impact of the CYP3A5 polymorphism on product formation from parent drug and its primary metabolites. Three primary CsA metabolites (AM1, AM9 and AM4N) were produced by heterologously expressed CYP3A4. In contrast, only AM9 was formed by CYP3A5. Substrate inhibition was observed for the formation of AM1 and AM9 by CYP3A4, and for the formation of AM9 by CYP3A5. Microsomes isolated from human kidney produced only AM9 and the rate of product formation (2 and 20 microM CsA) was positively associated with the detection of CYP3A5 protein and presence of the CYP3A5*1 allele in 4 of the 20 kidneys tested. A kinetic experiment with the most active CYP3A5*1-positive renal microsomal preparation yielded an apparent Km (15.5 microM) similar to that of CYP3A5 (11.3 microM). Ketoconazole (200 nM) inhibited renal AM9 formation by 22-55% over a CsA concentration range of 2-45 microM. Using liver microsomes paired with similar CYP3A4 content and different CYP3A5 genotypes, the formation of AM9 was two-fold higher in CYP3A5*1/*3 livers, compared to CYP3A5*3/*3 livers. AM19 and AM1c9, two of the major secondary metabolites of CsA, were produced by CsA, AM1 and AM1c when incubated with CYP3A4, CYP3A5, kidney microsomes from CYP3A5*1/*3 donors and all liver microsomes. Also, the formation of AM19 and AM1c9 was higher from incubations with liver and kidney microsomes with a CYP3A5*1/*3 genotype, compared to those with a CYP3A5*3/*3 genotype. Together, the data demonstrate that CYP3A5 may contribute to the formation of primary and secondary metabolites of CsA, particularly in kidneys carrying the wild-type CYP3A5*1 allele.

Differentiation between chronic rejection and chronic cyclosporine toxicity by analysis of renal cortical mRNA

BACKGROUND

In kidney transplantation, chronic allograft nephropathy (CAN) is the major cause of graft loss. Causes of CAN include chronic rejection and chronic cyclosporine A (CsA) nephrotoxicity. It is necessary to differentiate between these two entities in order to apply the appropriate therapeutic regimen for the individual patient, but this is hampered by the lack of discriminating functional and morphologic parameters. We investigated whether renal cortical mRNA levels for several matrix proteins can serve as discriminating parameters.

METHODS

Patients with chronic rejection (N= 19) and chronic CsA toxicity (N= 17) were selected by clinical and histologic criteria. Protocol biopsies without histologic abnormalities, taken at 6 months after transplantation from patients receiving CsA, were used as controls (N= 6). Total RNA was extracted from the renal biopsy tissue, and mRNA levels of transforming growth factor-beta (TGF-beta) and the extracellular matrix (ECM) molecules collagen Ialpha1, IIIalpha1, IValpha3, decorin, fibronectin, and laminin beta2 were measured by real-time polymerase chain reaction (PCR).

RESULTS

In both patient groups, the mean collagen IValpha3 and fibronectin mRNA levels were significantly elevated compared to those in controls, whereas only in CsA toxicity were the laminin beta2 and TGF-beta mRNA levels significantly increased. The increase of laminin beta2 and TGF-beta mRNA levels was significantly higher in the CsA toxicity group than in the chronic rejection group (P < 0.001 and P= 0.004, respectively). Receiver-operating characteristic (ROC) curve analysis showed that with a 15.6-fold increase in laminin beta2 mRNA expression as cut-off point, the presence of CsA toxicity could be predicted with an 87% sensitivity and an 88% specificity.

CONCLUSION

Renal laminin beta2 and TGF-beta mRNA levels can be used to differentiate between chronic rejection and chronic CsA toxicity in renal transplants. The method of mRNA quantification might be applicable as an additional diagnostic tool in clinical practice.

Cyclosporine-Induced renal dysfunction

The most practical way to assess and to quantitate the renal function in renal transplant patients is the Cockcroft-Gault equation or an equation used to estimate the glomerular filtration rate (GFR), derived from the Modification of Diet in Renal Disease study. Chronic cyclosporine (CsA) nephrotoxicity causes structural lesions in the kidney and an impairment in the GFR. Determining the composition of the interstitial collagens may be helpful to establish the diagnosis. CsA trough levels are a poor indicator of drug exposure; drug exposure should be quantitated using more accurate methods. Although routine biopsies often show histopathological evidence of structural damage, the excellent kidney graft half-life and the documentation that the creatinine clearance usually remains stable over years in CsA-treated renal transplant patients suggest that its use in kidney transplant patients does not inexorably lead to graft failure. Protocol biopsies show a high incidence of chronic structural CsA toxicity but transplant nephrectomies show that CsA nephrotoxicity as the sole cause of graft loss is extremely rare.

Strategies for ensuring effective surveillance in post-transplant patients: practical organization and clinical evaluation

Results of renal transplantation have improved steadily over the years. This article reviews the current status of patient and graft survival and discusses major causes of mortality and renal allograft failure. Review of recent literature demonstrates that the traditional enemies of transplantation, acute rejection and opportunistic infections are no longer major problems facing transplantation. Chronic graft nephropathy and death with functioning graft due to cardiovascular disease are the main challenges in the current era. An impact of an early graft thrombosis, recurrent renal disease and post-transplant malignancies are also reviewed. Chronic graft nephropathy is examined in a context of differences between two calcineurin inhibitors, cyclosporin microemulsion and tacrolimus. Strategies of post-transplant surveillance are suggested.

Mycophenolate mofetil-induced reversal of glomerular filtration loss in children with chronic allograft nephropathy

BACKGROUND

Mycophenolate mofetil (MMF) has been used for the treatment of chronic allograft nephropathy (CAN) in adults with inconsistent results, but data in children are rare. To evaluate its impact on advanced CAN, we studied changes in glomerular filtration rate (GFR) and the correlation of GFR changes to histology.

METHODS

Thirty-six children (13.1+/-3.6 years) with a progressive decline in GFR of 16.9+/-12.4 mL/min per 1.73 m2/year and biopsy confirmed CAN 4.3+/-2.9 years after transplantation were studied. MMF was added to conventional immunosuppression (IS) consisting of cyclosporine (CsA) and prednisolone (n=26) or tacrolimus (n=1) or replaced azathioprine in triple IS (n=9). Alterations of GFR were correlated to histologic guidelines according to the Banff chronic score (BCS).

RESULTS

One year after conversion, 22 (61%) children showed a rise in GFR (7.5+/-6 mL/min per 1.73 m2), 8 (22%) remained stable, and 6 (17%) showed a further decline of GFR (7.4+/-2 mL/min per 1.73 m2). Mean CsA trough levels were 114 ng/mL before and 98 ng/mL 1 year after conversion. MMF side effects required dose reduction in 14 children. Children responding to MMF with increasing GFR showed a trend toward less fibrosis, less incidence of vasculopathy, and transplant glomerulopathy in the initial biopsy but had a similar incidence of borderline tubulitis compared with the other groups.

CONCLUSIONS

Cotreatment with MMF reversed the progressive loss of GFR in approximately two thirds of children with CAN for at least 1 year. Less chronicity signs in histology seem to indicate a more favorable response to treatment.

Association between ABCB1 (multidrug resistance transporter) genotype and post-liver transplantation renal dysfunction in patients receiving calcineurin inhibitors

OBJECTIVE

Renal dysfunction is a common and costly adverse outcome of long-term treatment with calcineurin inhibitors (CNIs). We conducted a retrospective, case-control study to test whether the risk of renal dysfunction in liver transplantation patients receiving CNIs is associated with the 2677G>T transversion in exon-21 of the gene (ABCB1) encoding P-glycoprotein. A total of 120 non-Hispanic white patients were evaluated.

RESULTS

The overall incidence of renal dysfunction by year 3 post-transplantation was 40%. The frequency of renal dysfunction was reduced among patients with an ABCB1 2677TT genotype, as compared to those with a 2677GG genotype. Subjects with a heterozygote genotype behaved phenotypically like the 2677GG group. Comparing those subjects with a 2677TT genotype to the combined group of subjects with a 2677GG, TG, AT, or AG genotype resulted in an odds ratio of 0.26 (0.09-0.77). When subjects were stratified by gender, the frequency of renal dysfunction was reduced among men with an ABCB1 2677TT genotype, relative to men with different genotypes. A similar odds ratio was obtained for women, but it did not achieve significance. When 18 subjects with an elevated SCr concentration just prior to surgery were excluded from the year 3 analysis, the association between the 2677TT genotype and chronic renal dysfunction in the remaining cohort was strengthened comparing genotype groups.

CONCLUSIONS

Based on these results, we conclude that homozygosity for the ABCB1 2677T (S893) allele is associated with reduced risk of chronic renal dysfunction among liver transplantation patients receiving an immunosuppressive regimen containing CNIs.

Computer-assisted quantification of fibrosis in chronic allograft nephropaty by picosirius red-staining: a new tool for predicting long-term graft function

BACKGROUND

Chronic allograft nephropathy (CAN) has become the predominant limiting factor for long-term transplant survival. A cardinal histomorphologic correlate for CAN is interstitial fibrosis. Currently, no method has been established in routine use that reliably quantifies the extent of interstitial fibrosis in renal grafts. We have used staining with picrosirius red followed by computerized image analysis to study the correlation between graft fibrosis and future development of glomerular filtration rate (GFR) in a group of children with advanced CAN.

METHODS

Renal biopsies were performed in 56 children (mean age, 13.7+/-3.6 years) after a mean period of 4.6+/-3.1 years after transplantation because of significant increases in serum creatinine. All biopsy specimens were stained with picrosirius red. The magnitude of fibrotic tissue was calculated by computerized image analysis. Linear regression analysis was performed correlating the intensity of graft fibrosis and the changes in the GFR at the time points of renal biopsy and 2 years later.

RESULTS

There was a significant positive correlation (r=0.62, P<0.001) between the picrosirius red-stained cortical fractional interstitial fibrosis volume (V(intFib)) and the decrease of GFR within 2 years postrenal biopsy. When V(intFib) was below 5%, 82% of the patients had an increase in GFR within 2 years. Ninety-three percent of the patients with greater than 10% of fibrosis experienced a worsening renal function after 2 years. When comparing patients with stable GFR with patients having a decrease in GFR, a highly significant difference in V(intFib) was found (P=0.008).

CONCLUSIONS

The quantitative measurement of fibrosis by picrosirius red staining appears to be a useful prognostic indicator for estimating long-term graft function in CAN and may provide an easy, fast, and inexpensive tool helpful for treatment decisions in patients developing CAN.

Early interstitial accumulation of collagen type I discriminates chronic rejection from chronic cyclosporine nephrotoxicity

Little is known regarding the composition of the interstitial extracellular matrix of kidney allografts with deteriorating function. Collagen I, III, and IV, the collagen IV alpha3 chain, and the laminin beta2 chain were investigated in biopsies of allografted kidneys with chronic cyclosporine A nephrotoxicity (CsAT) (n = 17), chronic rejection (CR) (n = 12), or chronic allograft nephropathy (CAN) (n = 19). alpha-Smooth muscle actin expression was also examined. Normal native kidneys were used as control samples (n = 11). Biopsy samples were studied with routine light microscopy and immunostaining. The mean interstitial fibrosis scores were significantly higher for the CR and CAN groups, compared with the chronic CsAT group. The cortical tubulointerstitial areas of the CR and CAN groups, but not the chronic CsAT group, contained more collagen I than did normal control samples. Differences were noted even in biopsies with mild fibrosis. Accumulation of collagen III, IV, and IV alpha3 was increased in all patient groups. Collagen III accumulation was greater in the CR and CAN groups than in the chronic CsAT group. Receiver-operating characteristic curve analysis demonstrated that collagen I staining had the best discriminatory value in differentiating CR from chronic CsAT, with a sensitivity of 63% and a specificity of 94% at a cutoff value of 19%. Laminin beta2 staining did not differentiate CR from CsAT. Increased alpha-smooth muscle actin staining did not differ among the three groups. It was concluded that, during chronic CsAT, collagen III and IV were preferentially accumulated in the tubulointerstitium. Early increases in the deposition of collagen I, with collagen III and IV, were more specific for CR. CR seems to elicit a more pronounced fibrotic response than does chronic CsAT.

ECM homeostasis in renal diseases: a genomic approach

Chronic renal disease is in general histologically accompanied by a vast amount of scar tissue, ie glomerulosclerosis and interstitial fibrosis. Scarring results from excessive accumulation of extracellular matrix (ECM) components, a process driven by a plethora of cytokines and growth factors. Studies in experimental renal disease which target these regulators using gene therapy limit or prevent the development of scarring. This review focuses specifically on the role of transforming growth factor-beta, platelet-derived growth factor, connective tissue growth factor, hepatocyte growth factor, and epidermal growth factor. The results obtained in animal models hold promise for molecular intervention strategies in human renal disease. Microarray technology allows large-scale gene expression profiling in kidney tissue to identify common molecular pathways in a step towards discovery of new drug targets. Molecular techniques are expected to be used for diagnostic and prognostic purposes in nephrological practice to supplement renal biopsy. Several studies already show that molecular techniques might be of use in routine diagnostic practice. Improvement of diagnosis and prediction of outcome in renal patients might lead to more efficient and earlier therapeutic intervention.

Analysis of allograft biopsy specimens from long-term surviving patients with stable renal function: predictive value of long-term graft prognosis

Chronic allograft dysfunction is multi-factorial, and histology of long-term renal allograft shows variable findings. It is important to characterize the pathological features of graft kidneys with normal function to understand the natural course of transplants, which in turn would contribute to elucidate the causes of chronic allograft nephropathy (CAN). To address this issue, we performed 'non-episode' biopsies on well-functioning renal allografts, and evaluated the correlation between clinical outcome and histopathological findings. Patients who underwent a non-episode biopsy had a serum creatinine concentration less than 2.0 mg/dL, urinary protein of less than 500 mg/day and a stable clinical course. In total, 90 such biopsies were performed. Mean follow-up period after biopsy was 29 +/- 16 months. We evaluated the histopathological findings and clinical outcome on each finding. Moreover, we compared the findings in the patients on tacrolimus with those of patients taking cyclosporin. Twenty-three biopsy specimens were essentially normal. Graft dysfunction during the follow-up period was recognized more frequently in patients showing more than one pathological process than in those with isolated findings. Graft outcome was not associated with drug-induced nephropathy, but with acute rejection (P = 0.0193) and CAN (P = 0.0032). Patients found to have CAN-b had a worse outcome than those with CAN-a. CAN-b was less common in the tacrolimus group than in the cyclosporin group. Non-episode biopsy has a predictive value of the long-term outcome of a renal allograft. CAN is associated with graft dysfunction; neither is drug-induced nephropathy. Patients treated with tacrolimus had lower rates of CAN-b than did cyclosporin-treated subjects.

Modulation of matrix gelatinases and metalloproteinase-activating process in acute kidney rejection

Changes in matrix metalloproteinase (MMP) activities would contribute to the accumulation of extracellular matrix during acute kidney allograft rejection. MMP-2 and MMP-9 and other gelatinolytic activities were examined in the rejected graft and the urine of a rat model of acute kidney rejection (orthotopic allotransplantation from a Buffalo donor to a Wistar-Furth recipient) by either zymography or fluorescence assay. MMP-2, membrane type 1 (MT1)-MMP, and tissue inhibitor of metalloproteinase (TIMP)-2 were also examined by immunodetection. The proMMP-2 activity and protein level increased in the graft during rejection when compared with normal Buffalo kidney, whereas activated MMP-2 decreased. TIMP-2 protein levels were markedly decreased and MT1-MMP proteolytic fragments (44-40 kDa) were undetectable. This suggests an altered MT1-MMP-dependent processing of proMMP-2 into active MMP-2 due to a diminished TIMP-2 level in acute kidney rejection. In the urine the overall gelatinolytic activity decreased considerably, although activity associated with an as yet unidentified 78-kDa protein appeared 6 days after transplantation.

Renal fibrosis. Extracellular matrix microenvironment regulates migratory behavior of activated tubular epithelial cells

During progression of chronic renal disease, qualitative and quantitative changes in the composition of tubular basement membranes (TBMs) and interstitial matrix occur. Transforming growth factor (TGF)-beta(1)-mediated activation of tubular epithelial cells (TECs) is speculated to be a key contributor to the progression of tubulointerstitial fibrosis. To further understand the pathogenesis associated with renal fibrosis, we developed an in vitro Boyden chamber system using renal basement membranes that partially mimics in vivo conditions of TECs during health and disease. Direct stimulation of TECs with TGF-beta(1)/epithelial growth factor results in an increased migratory capacity across bovine TBM preparations. This is associated with increased matrix metalloproteinase (MMP) production, namely MMP-2 and MMP-9. Indirect chemotactic stimulation by TGF-beta(1)/EGF or collagen type I was insufficient in inducing migration of untreated TECs across bovine TBM preparation, suggesting that basement membrane integrity and composition play an important role in protecting TECs from interstitial fibrotic stimuli. Additionally, neutralization of MMPs by COL-3 inhibitor dramatically decreases the capacity of TGF-beta(1)-stimulated TECs to migrate through bovine TBM preparation. Collectively, these results demonstrate that basement membrane structure, integrity, and composition play an important role in determining interstitial influences on TECs and subsequent impact on potential aberrant cell-matrix interactions.

Prognostic value of plasminogen activator inhibitor type 1 mRNA in microdissected glomeruli from transplanted kidneys

BACKGROUND

Plasminogen activator inhibitor type 1 (PAI-1) exerts antifibrinolytic and profibrotic activities. Inside the glomerulus, PAI-1 is mainly synthesized by mesangial cells. We hypothesized that thrombin, via its receptor protease activated receptor type 1 (PAR-1), present on the membrane of glomerular cells, is an important mediator of PAI-1 synthesis.

METHODS

Using the technique of Peten et al., we microdissected the glomeruli of 23 kidney transplanted patients admitted in our department from 1993 to 1997, and we followed-up these patients for up to 5 years, with sometimes iterative renal biopsies. With this technique, we also microdissected the glomeruli of three patients who have had a nephrectomy for cancer (control patients). We investigated mRNA expression of the PAI-1, the thrombin receptor PAR-1, the alpha2 chain of type IV (alpha2 IV) collagen, and of a housekeeping gene (cyclophilin) by reverse transcription-polymerase chain reaction. The results were correlated with the renal function and the histological findings classified into acute rejection (9 biopsies), chronic rejection (22 biopsies), or normal (8 biopsies).

RESULTS

A significant up-regulation of PAI-1 and alpha2 IV collagen mRNA was observed in acute rejection (P<0.05) when compared to normal kidneys. A positive correlation exists between alpha2 IV collagen mRNA level and the degree of cellular infiltration. A negative correlation was found between the level of mRNA of PAR-1 and the degree of vascular thrombosis (P=0.005) and glomerulosclerosis (P=0.04). A positive correlation was found between the degradation of renal function and the mRNA level of PAI-1 at the time of the renal biopsy (P<0.05).

CONCLUSIONS

These results suggest that glomerular PAI-1 mRNA may be predictive of the long-term renal graft function.

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.

Alteration of collagen IV in acutely deteriorated renal allografts

BACKGROUND

The changes in the basement membrane occurring in acutely deteriorated renal allografts (ADR) have not been extensively investigated. Our purpose is to elucidate the alteration of collagen IV, a main constituent of the basement membrane in ADR.

METHODS

Fifty biopsy specimens of ADR and 10 of chronic transplant nephropathy (CTN) were examined with two monoclonal antibodies specific for collagen IV. JK199 and JK132 are monoclonal antibodies that recognize triple helical collagen IV containing the alpha1 chain. JK199 recognizes all the basement membrane containing [alpha1 (IV)]2alpha2(IV), although JK132 reacts only with a limited portion of it. In the normal kidney, JK199 reacts with the mesangial matrix, the basement membrane of Bowman's capsule (BBM), and the tubular basement membrane, as well as with the glomelular basement membrane (GBM). JK132 reacts with the mesangial matrix, BBM, and the tubular basement membrane.

RESULTS

In ADR, increased intensity of JK199 was observed in GBM, the mesangial matrix, BBM, the tubular basement membrane, and the interstitium. Increased intensity of JK132 was observed in the mesangial matrix, BBM, and the tubular basement membrane, but was not remarkable in GBM or the interstitium. In contrast, biopsy specimens of CTN showed increased intensity of JK132 in GBM, the mesangial matrix, BBM, the tubular basement membrane and the interstitium.

CONCLUSION

These results suggest that collagen IV is up-regulated in ADR. Differential staining of collagen IV with JK199 and JK132 in GBM and the interstitium may contribute to diagnose CTN.

Soluble intercellular adhesion molecule-1 (sICAM-1) after kidney transplantation: the origin and role of urinary sICAM-1?

BACKGROUND

Intercellular adhesion molecule-1 (ICAM-1) binds to leukocyte adhesion receptors LFA-1 and MAC-1, and mediates leukocyte adhesion to target structures. During acute rejection there is increased expression of ICAM-1 in vascular and tubulointestial cells, and consequently accumulation of inflammatory leukocytes. Soluble ICAM-1 (sICAM-1) is released from ICAM-1 expressing cells and excreted into the surrounding fluid. Increased serum sICAM-1 levels are found in patients with acute rejections of various allografts, and high urinary levels in steroid resistant acute kidney allograft rejection.

METHODS

Urinary excretion of sICAM-1 was measured by EIA in 136 kidney allograft recipients during the first 1-6 post transplant weeks: 30 patients developed acute rejection, and 106 patients had stable graft function. The molecular weight, binding to hyaluronan, and the origin of urinary sICAM-1 were studied.

RESULTS

We show that urinary sICAM-1 circulates as a monomer with a molecular weight between 50 and 100 kD. It binds to immobilized, but not to circulating hyaluronan. About one week after transplantation the mean sICAM-1/creatinine ratio (306 ng/mmol) in transplanted patients was higher than in the healthy controls (167 ng/mmol, P<0.01), and remained basically unchanged during the follow-up in patients with stable graft function, whereas it increased in patients developing rejection, being about 2.5-fold above the initial level a few days before rejection (P<0.01). Urinary sICAM-1 did not correlate with the urinary albumin, whereas in patients developing rejection it correlated with urinary IL-2R (r=0.5146, P<0.001), a marker of lymphocyte activation. In the urinary sediment of rejecting patients ICAM-1 was demonstrated in the tubular epithelial cells, and in the macrophages.

CONCLUSIONS

Increased urinary excretion of sICAM-1 was demonstrated in kidney transplanted patients a few days before acute rejection. It seems to originate from activated macrophages and/or from the tubular epithelial cells. The fact that urinary sICAM-1 is not bound to hyaluronan or to leukocytes suggests that it is not able to compete with membrane-bound ICAM-1 for these bindings, but may do so for the binding of activated macrophages.

Effect of anti-transforming growth factor-beta antibodies in cyclosporine-induced renal dysfunction

BACKGROUND

Several experimental and clinical studies have implicated a role for transforming growth factor-beta (TGF-beta) in mediating the nephrotoxic effects of cyclosporine (CsA). To test this hypothesis, we administered neutralizing anti-TGF-beta antibodies (alpha-TGF-beta) in a well-described rat model of chronic CsA nephrotoxicity.

METHODS

We studied three groups (N = 9 per group) of adult, male Sprague-Dawley rats that received a low-salt diet (0.05% sodium). Normal controls were given vehicle subcutaneously and an alternate-day intraperitoneal injection of 3 mg of nonspecific mouse IgG (MIgG) for 28 days. The CsA group received 15 mg/kg/day of CsA subcutaneously and 3 mg of MIgG intraperitoneally on alternate days for 28 days. The CsA/alpha-TGF-beta group received CsA and alternate-day alpha-TGF-beta (3 mg) for 28 days. At the end of 28 days, creatinine clearance was measured by 24-hour urine collection. Histologic assessment was performed for tubulointerstitial damage and arteriolar hyalinosis. Northern analysis was performed for alpha 1(I) collagen and TGF-beta 1 gene expression, and quantitative reverse transcription-polymerase chain reaction was performed to measure levels of tissue inhibitor of metalloproteinase-1 (TIMP-1), TIMP-2, plasminogen activator inhibitor-1 (PAI-1), matrix metalloproteinase-2 (MMP-2), and MMP-9.

RESULTS

CsA-treated rats had significantly lower creatinine clearance as compared with normal controls (0.43 +/- 0.07 vs. 0.67 +/- 0.14 mL/min, P = 0.0002), increased interstitial damage and afferent arteriolar hyalinosis (P = 0.0001), and increased alpha1(I) collagen (4-fold) and TGF-beta 1 (2.5-fold) mRNA expression. CsA-treated rats also had significantly increased TIMP-1 (7.4-fold, P < 0.001), MMP-2, and PAI-1 (all approximately 2-fold, P < 0.02) and decreased MMP-9 (85% reduction, P < 0.001) as compared with controls. Treatment with alpha-TGF-beta in CsA-treated rats significantly prevented the reduction in creatinine clearance (0.58 +/- 0.03 mL/min, P = 0.009 vs. CsA alone), the increase in afferent arteriolar hyalinosis (P < 0.05 vs. CsA alone), normalized alpha 1(I) collagen mRNA levels, and attenuated CsA effects on TGF-beta1, TIMP-1, and MMP-9.

CONCLUSIONS

In this rat model of CsA-induced nephrotoxicity, renal insufficiency and characteristic histologic changes are associated with altered expression of matrix and matrix-regulating molecules. Based on our results with alpha-TGF-beta antibodies, many but not all of these nephrotoxic effects of CsA are mediated by TGF-beta.

Differential effects of cyclosporin and tacrolimus on the expression of fibrosis-associated genes in isolated glomeruli from renal transplants

BACKGROUND

Chronic allograft nephropathy is characterized by an excessive accumulation of extracellular matrix proteins leading to glomerular and interstitial fibrosis. The aim of this study was to determine the effects of two different immunosuppressive agents (cyclosporin and tacrolimus) on the expression of the genes controlling extracellular matrix deposition in renal transplant glomeruli.

METHODS

Fifty-one renal transplant recipients were randomized to receive immunosuppression with either microemulsion cyclosporin or tacrolimus. Isolated glomeruli were plucked from protocol transplant biopsies performed 1 week, 3 months and 6 months after transplantation. Expression of the genes for collagen IValpha2, collagen III, matrix metalloproteinase 2, tissue inhibitor of metalloproteinases (TIMP) 1 and TIMP-2, tenascin and transforming growth factor (TGF) beta1 was studied by quantitative reverse transcriptase-polymerase chain reaction.

RESULTS

The expression of messenger RNA (mRNA) for collagen III and TIMP-1 was significantly higher in patients receiving cyclosporin therapy than in those having tacrolimus (P < 0.01); this finding was accounted for by differences in the biopsy material at 1 week. A significant difference in collagen III, TIMP-1 and TIMP-2 mRNA expression was also detected between patients depending on the source of renal donor (cadaveric or living). There were no significant differences in the level of glomerular TGF-beta1.

CONCLUSION

The data provide new in vivo evidence that tacrolimus may exert a less fibrogenic influence on transplant glomeruli than cyclosporin.

Molecular changes in extracellular matrix turnover after renal ischaemia-reperfusion injury

BACKGROUND

Renal ischaemia-reperfusion (IR) injury is an inevitable consequence of transplantation and contributes to later graft fibrosis. This study aimed to elucidate the possible mechanisms by studying the expression of genes associated with extracellular matrix (ECM) turnover.

METHODS

Male Wistar rats underwent laparotomy, clamping of the right renal pedicle for 45 min, and left nephrectomy. Control animals underwent left nephrectomy only, or had no operation. Animals were killed at 8, 16 and 24 weeks and messenger RNA was extracted from renal tissue. Genes of interest were amplified and then quantified in an enzyme-linked immunosorbent assay system with levels expressed as a ratio to a known housekeeping gene (GAPDH).

RESULTS

Experimental animals developed progressive proteinuria from 16 weeks onwards. At 8 weeks after IR injury, gene levels of matrix metalloproteinase (MMP) 2, an ECM-degrading enzyme, were significantly increased. Levels then fell progressively. This was associated with increasing expression of tissue inhibitor of metalloproteinases (TIMP) 1, an inhibitor of MMP-2, and of transforming growth factor (TGF) beta, a profibrotic cytokine, by 24 weeks following injury.

CONCLUSION

These results suggest that, after an initial phase of increased ECM turnover following IR injury, the balance turns towards one of reduced degradation. This is likely to be an important mechanism in the subsequent development of fibrosis.

Renal basement membrane components

Renal basement membrane components. Basement membranes are specialized extracellular matrices found throughout the body. They surround all epithelia, endothelia, peripheral nerves, muscle cells, and fat cells. They play particularly important roles in the kidney, as demonstrated by the fact that defects in renal basement membranes are associated with kidney malfunction. The major components of all basement membranes are laminin, collagen IV, entactin/nidogen, and sulfated proteoglycans. Each of these describes a family of related proteins that assemble with each other in the extracellular space to form the basement membrane. Over the last few years, new basement membrane components that are expressed in the kidney have been discovered. Here, the major components and their localization in mature and developing renal basement membranes are described. In addition, the phenotypes of basement membrane component gene mutations, both naturally occurring and experimental, are discussed, as is the aberrant deposition of basement membrane proteins in the extracellular matrix in several renal diseases.

Quantitation of allograft fibrosis and chronic allograft nephropathy

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

Chronic allograft nephropathy: An update

Chronic allograft nephropathy is the most prevalent cause of renal transplant failure in the first post-transplant decade, but its pathogenesis has remained elusive. Clinically, it is characterized by a slow but variable loss of function, often in combination with proteinuria and hypertension. The histopathology is also not specific, but transplant glomerulopathy and multilayering of the peritubular capillaries are highly characteristic. Several risk factors have been identified, such as advanced donor age, delayed graft function, repeated acute rejection episodes, vascular rejection episodes, and rejections that occur late after transplantation. A common feature of chronic allograft nephropathy is that it develops in grafts that have undergone previous damage, although the mechanism(s) responsible for the progressive fibrosis and tissue remodeling has not yet been defined. Hypotheses to explain chronic allograft nephropathy include the immunolymphatic theory, the cytokine excess theory, the loss of supporting architecture theory, and the premature senescence theory. The most effective option to prevent chronic allograft nephropathy is to avoid graft injury from both immune and nonimmune mechanisms.