Molecular biomarker candidates of acute kidney injury in zero-hour renal transplant needle biopsies

Assessing Biomarkers of Porcine Kidneys under Normothermic Machine Perfusion-Can We Gain Insight into a Marginal Organ?

To identify potentially transplantable organs in a pool of marginal kidneys, 33 porcine slaughterhouse kidneys were perfused for 4 h with whole blood. During the normothermic perfusion, plasma, urine, and tissue samples were taken. Several biomarkers for tubule injury, endothelial activation, and inflammatory response were evaluated for a potential correlation with macroscopic appearance, histology, and filtration activity. Generally, biomarker levels increased during perfusion. TLR-4, EDN-1, and NGAL were not associated with any classification. In contrast, a steeper increase in NAG and IL-6 in plasma correlated with a poor macroscopic appearance at 4 h, indicating a higher inflammatory response in the kidneys with worse macroscopy early on, potentially due to more damage at the tubules. Although long-term effects on the graft could not be assessed in this setting, early observation under machine perfusion with whole blood was feasible. It allowed the assessment of kidneys under conditions comparable to reperfusion. This setting could give surgeons further insight into the quality of marginal kidneys and an opportunity to pre-treat them.

Five-gene signature predicts acute kidney injury in early kidney transplant patients

Patients with acute kidney injury (AKI) show high morbidity and mortality, and a lack of effective biomarkers increases difficulty in its early detection. Weighted gene co-expression network analysis (WGCNA) detected a total of 22 gene modules and 6 miRNA modules, of which 4 gene modules and 3 miRNA modules were phenotypically co-related. Functional analysis revealed that these modules were related to different molecular pathways, which mainly involved PI3K-Akt signaling pathway and ECM-receptor interaction. The brown modules related to transplantation mainly involved immune-related pathways. Finally, five genes with the highest AUC were used to establish a diagnosis and prediction model of AKI. The model showed a high area under curve (AUC) in the training set and validation set, and their prediction accuracy for AKI was as high as 100%. Similarly, the prediction accuracy of AKI after 24 h in the 0 h transplant sample was 100%. This study may provide new features for the diagnosis and prediction of AKI after kidney transplantation, and facilitate the diagnosis and drug development of AKI in kidney transplant patients.

The mRNA landscape profiling reveals potential biomarkers associated with acute kidney injury AKI after kidney transplantation

Background

This study aims to identify potential biomarkers associated with acute kidney injury (AKI) post kidney transplantation.

Material and Methods

Two mRNA expression profiles from Gene Expression Omnibus repertory were downloaded, including 20 delayed graft function (DGF) and 68 immediate graft function (IGF) samples. Differentially expressed genes (DEGs) were identified between DGF and IGF group. The Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analysis of DEGs were performed. Then, a protein-protein interaction analysis was performed to extract hub genes. The key genes were searched by literature retrieval and cross-validated based on the training dataset. An external dataset was used to validate the expression levels of key genes. Receiver operating characteristic curve analyses were performed to evaluate diagnostic performance of key genes for AKI.

Results

A total of 330 DEGs were identified between DGF and IGF samples, including 179 up-regulated and 151 down-regulated genes. Of these, OLIG3, EBF3 and ETV1 were transcription factor genes. Moreover, LEP, EIF4A3, WDR3, MC4R, PPP2CB, DDX21 and GPT served as hub genes in PPI network. EBF3 was significantly up-regulated in validation GSE139061 dataset, which was consistently with our initial gene differential expression analysis. Finally, we found that LEP had a great diagnostic value for AKI (AUC = 0.740).

Conclusion

EBF3 may be associated with the development of AKI following kidney transplantation. Furthermore, LEP had a good diagnostic value for AKI. These findings provide deeper insights into the diagnosis and management of AKI post renal transplantation.

Assessment of Organ Quality in Kidney Transplantation by Molecular Analysis and Why It May Not Have Been Achieved, Yet

Donor organ shortage, growing waiting lists and substantial organ discard rates are key problems in transplantation. The critical importance of organ quality in determining long-term function is becoming increasingly clear. However, organ quality is difficult to predict. The lack of good measures of organ quality is a serious challenge in terms of acceptance and allocation of an organ. The underlying review summarizes currently available methods used to assess donor organ quality such as histopathology, clinical scores and machine perfusion characteristics with special focus on molecular analyses of kidney quality. The majority of studies testing molecular markers of organ quality focused on identifying organs at risk for delayed graft function, yet without prediction of long-term graft outcome. Recently, interest has emerged in looking for molecular markers associated with biological age to predict organ quality. However, molecular gene sets have not entered the clinical routine or impacted discard rates so far. The current review critically discusses the potential reasons why clinically applicable molecular quality assessment using early kidney biopsies might not have been achieved yet. Besides a critical analysis of the inherent limitations of surrogate markers used for organ quality, i.e., delayed graft function, the intrinsic methodological limitations of studies assessing organ quality will be discussed. These comprise the multitude of unpredictable hits as well as lack of markers of nephron mass, functional reserve and regenerative capacity.

LncRNA XIST serves as a ceRNA to regulate the expression of ASF1A, BRWD1M, and PFKFB2 in kidney transplant acute kidney injury via sponging hsa-miR-212-3p and hsa-miR-122-5p

We aimed to identify potential mechanism associated with acute kidney injury (AKI) after kidney transplantation. The dataset GSE53771, which contained 18 zero-hour (ZERO group) and 18 selected post-transplant (POST group) biopsy samples from 18 kidney allografts (8 AKI and 10 controls) was downloaded from GEO database. Differentially expressed miRNAs (DEMIs) were screened using limma package, and bidirectional hierarchical clustering of the DEMIs was performed using the pheatmap package. Target genes of DEMIs were predicted by miRWalk 2.0, miRNA-target genes networks were presented using Cytoscape, protein-protein interaction (PPI) networks were constructed by STRING (version:10.0) database, and competing endogenous RNAs (ceRNA) regulating network were constructed using Cytoscape. In ZERO and POST groups, a total of 4 and 24 differentially expressed miRNAs were obtained in AKI samples compared with control, respectively. Specifically, 71 lncRNAs were obtained to interact with five miRNAs (hsa-miR-215-5p, hsa-miR-192-5p, hsa-miR-422a, hsa-miR-212-3p and hsa-miR-122-5p). Histone chaperone ASF1A (ASF1A) and bromodomain and WD repeat-containing protein 1(BRWD1) were targeted by hsa-miR-212-3p in PPI network. In ceRNA network, lncRNA XIST could interact with four miRNAs (hsa-miR-212-3p, hsa-miR-122-5p, hsa-miR-215-5p, and hsa-miR-192-5p). LncRNA XIST might serve as a ceRNA to sponge hsa-miR-212-3p to regulate the development of AKI via altering the expression of ASF1A/BRWD1. Furthermore, lncRNA XIST could also interact with hsa-miR-122-5p to modulate the expression of PFKFB2 in thyroid hormone signaling pathway and AMPK signaling pathway. LncRNA XIST can serve as a ceRNA to sponge hsa-miR-212-3p and hsa-miR-122-5p to regulate AKI progression via modulating the expression of ASF1A, BRWD1, and PFKFB2.[Figure: see text].

HAVCR1 Affects the MEK/ERK Pathway in Gastric Adenocarcinomas and Influences Tumor Progression and Patient Outcome

The hepatitis A virus cellular receptor 1 (HAVCR1) gene as a sensitive and specific biomarker has been reported in various diseases. Especially, HAVCR1 overexpression promotes the development and progression of several human cancers. Hence, we aimed to detect the effects of HAVCR1 on gastric adenocarcinoma (GAC). We first determined the expression of HAVCR1 in GAC tissues compared with normal gastric tissues based on the Cancer Genome Atlas (TCGA) database using bioinformatics analysis methods. Then, we assessed the biological function of HAVCR1 in GAC cells using quantitative real-time reverse transcription-PCR (qRT-PCR), western blot, cell counting kit-8- (CCK-) 8, colony formation assay, wound healing assay, and transwell assay. Our results showed that HAVCR1 expression was upregulated in GAC tissues and positively associated with poor survival. Loss-of-function analyses indicated that knockdown of HAVCR1 inhibited the proliferation, colony formation, migration, and invasion of GAC cells. Furthermore, reduction of HAVCR1 in GAC cells can decrease the expression of phosphorylated MEK/ERK. These findings suggested that HAVCR1 may represent a potential biomarker for GAC prognosis, as well as a novel therapeutic target for GAC treatment.

The Small RNA Repertoire of Small Extracellular Vesicles Isolated From Donor Kidney Preservation Fluid Provides a Source for Biomarker Discovery for Organ Quality and Posttransplantation Graft Function

Supplemental Digital Content is available in the text.

Delayed graft function (DGF) after kidney transplantation is negatively associated with long-term graft function and survival. Kidney function after transplantation depends on multiple factors, both donor- and recipient-associated. Prediction of posttransplantation graft function would allow timely intervention to optimize patient care and survival. Currently, graft-based predictions can be made based on histological and molecular analyses of 0-hour biopsy samples. However, such analyses are currently not implemented, as biopsy samples represent only a very small portion of the entire graft and are not routinely analyzed in all transplantation centers. Alternatives are thus required.

Proteins in Preservation Fluid as Predictors of Delayed Graft Function in Kidneys from Donors after Circulatory Death

BACKGROUND AND OBJECTIVES

Kidney transplantation is the preferred treatment for ESRD, and donor kidney shortage urges proper donor-recipient matching. Zero-hour biopsies provide predictive values for short- and long-term transplantation outcomes, but are invasive and may not reflect the entire organ. Alternative, more representative methods to predict transplantation outcome are required. We hypothesized that proteins accumulating in preservation fluid during cold ischemic storage can serve as biomarkers to predict post-transplantation graft function.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Levels of 158 proteins were measured in preservation fluids from kidneys donated after circulatory death (Maastricht category III) collected in two Dutch centers (University Medical Center Utrecht and Erasmus Medical Center Rotterdam) between 2013 and 2015. Five candidate biomarkers identified in a discovery set of eight kidneys with immediate function (IF) versus eight with delayed graft function (DGF) were subsequently analyzed in a verification set of 40 additional preservation fluids to establish a prediction model.

RESULTS

Variables tested for their contribution to a prediction model included five proteins (leptin, periostin, GM-CSF, plasminogen activator inhibitor-1, and osteopontin) and two clinical parameters (recipient body mass index [BMI] and dialysis duration) that distinguished between IF and DGF in the discovery set. Stepwise multivariable logistic regression provided a prediction model on the basis of leptin and GM-CSF. Receiver operating characteristic analysis showed an area under the curve (AUC) of 0.87, and addition of recipient BMI generated a model with an AUC of 0.89, outperforming the Kidney Donor Risk Index and the DGF risk calculator, showing AUCs of 0.55 and 0.59, respectively.

CONCLUSIONS

We demonstrate that donor kidney preservation fluid harbors biomarkers that, together with information on recipient BMI, predict short-term post-transplantation kidney function. Our approach is safe, easy, and performs better than current prediction algorithms, which are only on the basis of clinical parameters.

Hypoxia-Inducible Factor-1α Expression in Kidney Transplant Biopsy Specimens After Reperfusion Is Associated With Early Recovery of Graft Function After Cadaveric Kidney Transplantation

BACKGROUND

Ischemia/reperfusion injury during kidney transplantation (KTx) delays allograft recovery. Hypoxia-inducible factor-1α (HIF-1α) is the key regulator of the protective response to ischemia/reperfusion injury. We evaluated the impact of the HIF-1α signaling pathway on allograft recovery during cadaveric KTx.

METHODS

Between 1996 and 2015, 46 patients underwent cadaveric KTx. The expression levels of HIF-1α-related proteins, including phosphoinositide 3-kinase, phosphorylated (p)-Akt, p-mammalian target of rapamycin, p-Eukaryotic translation initiation factor 4E, p-S6 ribosomal protein, and HIF-1α, were immunohistochemically evaluated and semi-quantitatively scored in graft biopsy specimens after 1 hour of revascularization. Ten kidney biopsy specimens collected during donor nephrectomy for living KTx were used as controls. Delayed graft function (DGF) was defined as the need for dialysis within 1 week of KTx. We compared the staining scores of each protein and several clinical parameters between patients with and those without DGF.

RESULTS

Expression levels of all six proteins in specimens after revasculization were elevated compared with those in controls. Thirty-five patients had DGF. Expression levels of PI3K, p-AKT, p-mTOR, p-eIF4E, and HIF-1α were significantly higher in patients without DGF than in those with DGF. Univariate analysis identified expression levels of p-Akt, p-S6, and HIF-1α, in addition to donor type (heart beating/non-heart beating), cold ischemic time, and donor age as significant predictors of DGF. Of these, only expression levels of HIF-1α and donor type were independently associated with DGF in multivariate analysis.

CONCLUSIONS

Up-regulation of HIF-1α in allografts after reperfusion may be a predictor of early recovery after cadaveric KTx.

The influence of warm ischemia elimination on kidney injury during transplantation - clinical and molecular study

Kidney surface cooling was used during implantation to assess the effect of warm ischemia elimination on allograft function, histological changes and immune-related gene expression. 23 recipients were randomly assigned to a group operated on with kidney surface cooling during implantation (ice bag technique, IBT group), and the other 23 recipients receiving the contralateral kidney from the same donor were operated on with a standard technique. Three consecutive kidney core biopsies were obtained during the transplantation procedure: after organ recovery, after cold ischemia and after reperfusion. Gene expression levels were determined using low-density arrays (Format 32, TaqMan). The IBT group showed a significantly lower rate of detrimental events (delayed graft function and/or acute rejection, p = 0.015) as well as higher glomerular filtration rate on day 14 (p = 0.026). A greater decrease of MMP9 and LCN2 gene expression was seen in the IBT group during total ischemia (p = 0.003 and p = 0.018). Elimination of second warm ischemia reduced the number of detrimental events after kidney transplantation, and thus had influence on the short-term but not long-term allograft function. Surface cooling of the kidney during vascular anastomosis may reduce some detrimental effects of immune activation resulting from both brain death and ischemia-reperfusion injury.

Predicting delayed kidney graft function with gene expression in preimplantation biopsies and first-day posttransplant blood

The purpose of this study was to investigate possible markers for predicting delayed graft function (DGF). To this end we analyzed, in pre-implantation biopsies (PIB) and in first-day post-Tx peripheral blood mononuclear cells (PBMC), the expression of five genes (ACSL4, CUBN, DEFB1, FABP3, GK) through real-time TaqMan PCR assays. These genes were selected from a large scale gene expression study in PIB. DEFB1, FABP3 and GK expression levels in PIB were lower in cases with DGF and, in a multivariate analysis which included these genes and clinical variables, only FABP3 expression remained independently associated with DGF. FABP3 expression lower than -1.32 units of relative expression conferred an odds ratio for DGF of 41.1. Compared to the PBMC of recipients without DGF, recipients with prolonged DGF (pDGF) had lower ACSL4 and higher DEFB1 expression levels. In a multivariate analysis, including PBMC gene expression levels of ACSL4, DEFB1 and TLR4 (data from a previous study with the same patients) and clinical variables, only TLR4 remained independently associated with pDGF. In summary, this study revealed FABP3 expression in PIB as a marker for DGF and disclosed new genes possibly involved in the pathogenesis of DGF.

Transplant biopsy beyond light microscopy

Despite its long-standing status as the diagnostic "gold standard", the renal transplant biopsy is limited by a fundamental dependence on descriptive, empirically-derived consensus classification. The recent shift towards personalized medicine has resulted in an increased demand for precise, mechanism-based diagnoses, which is not fully met by the contemporary transplantation pathology standard of care. The expectation is that molecular techniques will provide novel pathogenetic insights that will allow for the identification of more accurate diagnostic, prognostic, and therapeutic targets. Here we review the current state of molecular renal transplantation pathology. Despite significant research activity and progress within the field, routine adoption of clinical molecular testing has not yet been achieved. The recent development of novel molecular platforms suitable for use with formalin-fixed paraffin-embedded tissue will offer potential solution for the major barriers to implementation. The recent incorporation of molecular diagnostic criteria into the 2013 Banff classification is a reflection of progress made and future directions in the area of molecular transplantation pathology. Transcripts related to endothelial injury and NK cell activation have consistently been shown to be associated with antibody-mediated rejection. Prospective multicenter validation and implementation of molecular diagnostics for major entities remains an unmet clinical need in transplantation. It is expected that an integrated system of transplantation pathology diagnosis comprising molecular, morphological, serological, and clinical variables will ultimately provide the greatest diagnostic precision.

Molecular nephropathology: ready for prime time?

In the current era of precision medicine, the existing nephropathology paradigm of light microscopy, immunofluorescence, and electron microscopy will become increasingly insufficient. There will be an expectation to supplement these traditional diagnostic tools with patient-specific information related to a growing understanding of molecular pathophysiology. Next generation sequencing technologies are expected to play a key role in the future of nephropathology, but transcriptomics is poised to represent the first major foray into routine molecular testing. The introduction of molecular techniques into clinical nephropathology has been hindered in part by the reliance of existing platforms on fresh tissue samples. The NanoString gene expression system works with formalin-fixed paraffin-embedded tissue and thus represents a promising solution to this technical barrier that may finally allow for the translation of recent transcriptomics discoveries into the enhancement of patient care. Widespread adoption of this new diagnostic dimension will require ongoing multidisciplinary cooperation between pathologists and clinicians, including molecular testing consensus generation and rigorous multicenter validation.

Renalomics: Molecular Pathology in Kidney Biopsies

In this article, various omics technologies and their applications in renal pathology (native and transplant biopsies) are reviewed and discussed. Despite significant progress and novel insights derived from these applications, extensive adoption of molecular diagnostics in renal pathology has not been accomplished. Further validation of specific applications leading to increased diagnostic precision in a clinically relevant way is ongoing.

Investigation of apoptosis-related gene expression levels in preimplantation biopsies as predictors of delayed kidney graft function

BACKGROUND

The purpose of this study was to investigate the expression of the gene coding for the antiapoptotic molecule Bcl-2, the proapoptotic molecule Bax, and the apoptosis executor enzyme caspase-3 in preimplantation renal biopsies (PIB) as markers for delayed graft function.

METHODS

In this prospective single-center study, gene expression levels were evaluated using real-time TaqMan polymerase chain reaction in PIB of kidneys from 72 deceased donors (DDs) and 18 living donors (LDs).

RESULTS

CASP3 and BAX expression levels were higher, whereas those of BCL2 were lower, in DD than in LD PIB. In biopsies from DD, BCL2 levels were lower in cases with DGF, whereas no differences were observed concerning CASP3 and BAX. The BAX/BCL2 gene expression ratio greater than 2.29 associated with DGF with an odds ratio of 2.00. A multiple regression analysis including data of TLR4 expression in the first day posttransplant PB from a previous study of our group conducted in the same patients revealed a very strong association of the combination of BAX/BCL2 greater than 2.3 in PIB and TLR4 of 0.95 uRE or lesser in PB with the occurrence of DGF, with OR of 120 and positive and negative predictive values of 91% and 92%, respectively.

CONCLUSIONS

The power to predict DGF of the combination of high BAX/BCL2 expression in PIB and low TLR4 expression in the first day posttransplant peripheral blood observed in the present study is extremely high, in comparison to any other marker or combinations of markers so far published in the literature.

Assessment of donor biopsies

PURPOSE OF REVIEW

To provide an up-to-date overview about the assessment of donor biopsies and to discuss the current problems and chances of preimplantation biopsies for transplant allocation with a focus on the technical work up and the histological variables scored.

RECENT FINDINGS

Preimplantation biopsy results are the major reason for discarding procured extended donor criteria kidneys in the USA. There is neither a consensus on the work up, nor the reporting of preimplantation donor biopsies, nor the importance of the biopsy findings in the process of allocation. The best available data have been collected in the context of single vs. double kidney transplantation. A clinical risk factor score may help to define kidneys when a preimplantation biopsy is warranted. Punch biopsies using a skin punch device appear to be a reasonable alternative for surgeons fearing needle biopsies.

SUMMARY

Donor biopsies are very useful as zero-hour biopsies establishing baseline information for comparison with subsequent transplant biopsies. As none of the histological variables and scores provides perfect prediction, preimplantation biopsy results have to be interpreted in the context of all available donor and recipient information.

Lipocalin-2 as mediator of chemokine expression and granulocyte infiltration during ischemia and reperfusion

Lipocalin-2 (Lcn2) expression contributes to ischemia and reperfusion injury (IRI) by enhancing pro-inflammatory responses. The aim of this work was to elucidate the regulation of Lcn2 during hypoxia and its effects on the expression of key chemokines and adhesion molecules. Lcn2 wt and Lcn2(-/-) mice were used in a heterotopic heart transplantation model. Quantitative RT-PCR was applied for chemokine gene expression analysis. Reporter gene studies were used to elucidate the regulation of the Lcn2 promoter by hypoxia. HIF-1β expression led to a 2.4-fold induction of the Lcn2 promoter. Apart from an earlier onset of granulocyte infiltration in the Lcn2 wt setting after 2 h of reperfusion compared with the Lcn2(-/-) setting (P < 0.013), exogenous application of recombinant Lcn2 revealed a trend toward increase of granulocyte infiltration. Analyzed chemokines were expressed significantly higher in the Lcn2 wt setting at 2 h of reperfusion (P ≤ 0.05). The number of apoptotic cells observed in Lcn2(-/-) grafts was significantly higher than in the Lcn2 wt setting. Our results indicate that Lcn2 affects granulocyte infiltration in the reperfused graft by modulating the expression of chemokines, their receptors and the apoptotic rate.

Development and validation of an LC-MS/MS assay for the quantification of the trans-methylation pathway intermediates S-adenosylmethionine and S-adenosylhomocysteine in human plasma

BACKGROUND

Although increased levels of S-adenosylmethionine (SAM) and S-adenosylhomocysteine (SAH) have been implicated as markers for renal and vascular dysfunction, until now there have been no studies investigating their association with clinical post-transplant events such as organ rejection and immunosuppressant nephrotoxicity.

METHODS

A newly developed and validated liquid chromatography-tandem mass spectrometry (LC-MS/MS) assay for the quantification of SAM and SAH in human EDTA plasma was used for a clinical proof-of-concept pilot study. Retrospective analysis was performed using samples from a longitudinal clinical study following de novo kidney transplant patients for the first year (n=16).

RESULTS

The ranges of reliable response were 8 to 1024 nmol/l for SAM and 16 to 1024 nmol/l for SAH. The inter-day accuracies were 96.7-103.9% and 97.9-99.3% for SAM and SAH, respectively. Inter-day imprecisions were 8.1-9.1% and 8.4-9.8%. The total assay run time was 5 min. SAM and SAH concentrations were significantly elevated in renal transplant patients preceding documented acute rejection and nephrotoxicity events when compared to healthy controls (n=8) as well as transplant patients void of allograft dysfunction (n=8).

CONCLUSION

The LC-MS/MS assay will provide the basis for further large-scale clinical studies to explore these thiol metabolites as molecular markers for the management of renal transplant patients.

Comparing molecular assessment of implantation biopsies with histologic and demographic risk assessment

We hypothesized that measurement of previously defined acute kidney injury-induced transcripts at the time of implantation would add a new dimension to existing methods based on donor factors, histology and recipient factors. We analyzed microarray results from implantation biopsies taken after reperfusion from 70 kidneys from 53 deceased donors. We used two definitions of early dysfunction: serum creatinine > 265 umol/L at day 7 posttransplant; and dialysis in the first week. The strongest correlate with early dysfunction was the mean expression of 30 injury transcripts. Older donor and recipient age were associated with early dysfunction, but histologic lesions were not. Prediction was best when the injury transcript expression was combined with donor or recipient age, particularly in standard criteria donors. In contrast, although extended criteria donor kidneys had a high risk of early dysfunction, no variables tested, including injury transcripts, predicted risk significantly, probably because these kidneys were allocated preferentially to old, high risk recipients. The injury transcripts did not predict late function, which was mainly associated with donor age. Thus, measurement of injury-induced transcripts at the time of implantation improves the prediction of early kidney dysfunction, but risk prediction may fail when old kidneys are transplanted into old recipients.

Chronic renal allograft damage after transplantation: what are the reasons, what can we do?

PURPOSE OF REVIEW

Chronic renal allograft damage is one of the main problems after kidney transplantation. This review enumerates causes, describes available therapeutic options, and discusses options of the future.

RECENT FINDINGS

Alloantigen-dependent and alloantigen-independent factors are responsible for allograft damage. Prevention of renal allograft damage starts with interventions that occur surrounding the explantation in cadaveric organs. These include the use of dopamine or machine perfusion systems.Followed by the critical phase of ischemia/reperfusion injury, the LCN2/lipocalin-2, HAVCR1, and p38 MAPK pathway are new players involved in that process. Innate immunity plays a part, too. Cold ischemia time is associated with genes of apoptosis. Nondonor-specific antibodies like antihuman leukocyte antibodies-Ia or angiotensin type 1 receptor may also play a role. Recent research indicates that genetic polymorphism like the Ficolin-2 Ala258Ser polymorphism and the mannose-binding lectin-2 polymorphism are involved in that process. New therapeutic options are rare and in the future. However, there is some evidence that drugs interfering with metalloproteinases, sexual hormones like dihydroandrosterone, and mesenchymal stem cell therapy may be of importance.

SUMMARY

Taken together, although the understanding of chronic rejection has improved, the available therapeutic options remain scarce.

The multifaceted roles of neutrophil gelatinase associated lipocalin (NGAL) in inflammation and cancer

Neutrophil gelatinase associated lipocalin (NGAL), also known as oncogene 24p3, uterocalin, siderocalin or lipocalin 2, is a 24kDa secreted glycoprotein originally purified from a culture of mouse kidney cells infected with simian virus 40 (SV-40). Subsequent investigations have revealed that it is a member of the lipocalin family of proteins that transport small, hydrophobic ligands. Since then, NGAL expression has been reported in several normal tissues where it serves to provide protection against bacterial infection and modulate oxidative stress. Its expression is also dysregulated in several benign and malignant diseases. Its small size, secreted nature and relative stability have led to it being investigated as a diagnostic and prognostic biomarker in numerous diseases including inflammation and cancer. Functional studies, conducted primarily on lipocalin 2 (Lcn2), the mouse homologue of human NGAL have revealed that Lcn2 has a strong affinity for iron complexed to both bacterial siderophores (iron-binding proteins) and certain human proteins like norepinephrine. By sequestering iron-laden siderophores, Lcn2 deprives bacteria of a vital nutrient and thus inhibits their growth (bacteriostatic effect). In malignant cells, its proposed functions range from inhibiting apoptosis (in thyroid cancer cells), invasion and angiogenesis (in pancreatic cancer) to increasing proliferation and metastasis (in breast and colon cancer). Ectopic expression of Lcn2 also promotes BCR-ABL induced chronic myelogenous leukemia in murine models. By transporting iron into and out of the cell, NGAL also regulates iron responsive genes. Further, it stabilizes the proteolytic enzyme matrix metalloprotease-9 (MMP-9) by forming a complex with it, and thereby prevents its autodegradation. The factors regulating NGAL expression are numerous and range from pro-inflammatory cytokines like interleukins, tumor necrosis factor-α and interferons to vitamins like retinoic acid. The purpose of this review article is to examine the expression, structure, regulation and biological role of NGAL and critically assess its potential as a novel diagnostic and prognostic marker in both benign and malignant human diseases.

Molecular phenotypes of acute kidney injury in kidney transplants

Little is known regarding the molecular phenotype of kidneys with AKI because biopsies are performed infrequently. However, all kidney transplants experience acute injury, making early kidney transplants an excellent model of acute injury, provided the absence of rejection, because donor kidneys should not have CKD, post-transplant biopsies occur relatively frequently, and follow-up is excellent typically. Here, we used histopathology and microarrays to compare indication biopsies from 26 transplants with acute injury with 11 pristine protocol biopsies of stable transplants. Kidneys with acute injury showed increased expression of 394 transcripts associated with the repair response to injury, including many epithelium-like injury molecules tissue, remodeling molecules, and inflammation molecules. Many other genes also predicted the phenotype, including the acute injury biomarkers HAVCR1 and IL18. Pathway analysis of the injury-repair transcripts revealed similarities to cancer, development, and cell movement. The injury-repair transcript score in kidneys with acute injury correlated with reduced graft function, future renal recovery, brain death, and need for dialysis, but not with future graft loss. In contrast, histologic features of acute tubular injury did not correlate with function or with the molecular changes. Thus, the transcripts associated with repair of injury suggest a massive coordinated response of the kidney parenchyma to acute injury, providing both an objective measure for assessing the severity of injury in kidney biopsies and validation for many biomarkers of AKI.

Identifying biomarkers as diagnostic tools in kidney transplantation

There is a critical need for biomarkers for early diagnosis, treatment response, and surrogate end point and outcome prediction in organ transplantation, leading to a tailored and individualized treatment. Genomic and proteomic platforms have provided multiple promising new biomarkers during the last few years. However, there is still no routine application of any of these markers in clinical transplantation. This article will discuss the existing gap between biomarker discovery and clinical application in the kidney transplant setting. Approaches to implementing biomarker monitoring into clinical practice will also be discussed.