Chronic Kidney Allograft Rejection Research Articles

Natural Killer Cell Activity Is Increased in Chronic Active Antibody-Mediated Rejection (caABMR) of Human Kidney Allografts

Natural Killer Cell Activity Is Increased in Chronic Active Antibody-Mediated Rejection (caABMR) of Human Kidney Allografts

425.2: Recipient Myeloid Cell Myeloperoxidase Is Required for NK Cell Activation and Regulates Antibody-Mediated Acute VS. Chronic Kidney Allograft Rejection

425.2: Recipient Myeloid Cell Myeloperoxidase Is Required for NK Cell Activation and Regulates Antibody-Mediated Acute VS. Chronic Kidney Allograft Rejection

P8.054: Out of the Box. Immunosuppressive Therapy With Four Drugs As Rescue Therapy in Kidney Transplant Recipients With Chronic Allograft Rejection

Introduction: Persistent or repeated episodes of acute rejection (AR) may lead to chronic allograft damage. Antibody-mediated rejection (AMR); T-cell mediated rejection (TCMR) and mixed variants (MR) of chronic kidney allograft rejection (CR) are nowadays considered as the main causes of graft loss (GL). This encompasses from endothelial damage up to fibrosis challenging immunosuppressive therapy (IT) management. IT reinforcement with a four-drug scheme (4D) including m-TOR inhibitors, anticalcineurinics, mycophenolate and steroids, could be a good strategy in this scenario, nevertheless there is no consensus about it. We present our experience with 4D in kidney transplant recipients (KT) That presented with CR or recurrent episodes of AR. Objectives: To evaluate kidney graft function (KGF), incidence of rejection and safety of a 4D in KT with CR or recurrent episodes of AR. Methods: KT on treatment with 4D from 2008 to 2021 were included. KGF was evaluated by estimated glomerular filtration rate with CKD-EPI (eGFR) and urinary protein/creatinine ratio (PCR) at 3, 6 and 12 months. Kidney biopsies and panel reactive antibodies (PRA) by Luminex were performed before and after introduction of 4D. BK virus (BKV) incidence, infectious (IE) and neoplastic (NE) events were recorded during the follow up. Results: 16 KT (median age 45 ± 11 years) were treated with 4D during 52.8 (17-106) months. 43.8% of them were women, 50% were deceased KT. The median post transplant time was 108 (60-129) months. Reasons for 4D introduction were CR in 87.4% of the cases (MR 50%; TCMR 31.3%; AMR 6.3%) and in the remaining 12, 6%, recurrent or persistent acute TCMR. Median eGFR was 42 (27-66); 44 (31-62); 48 (33-60) and 48 (32-65) ml/min prior to IT change, at 3, 6 and 12 months respectively. At baseline, mean PCR was 179 (147-664) mg/g without significant changes during follow up. Biopsy proven AR was found in 37% of KT under 4D. No NE were registered. 43% of the patients presented a non major IE, and only one patient was BKV positive during follow up with 4D. There was one GL, one loss of follow up and one death due to sepsis with functioning graft. Conclusions: KT patients with CR or recurrent episodes of AR changed to 4D IT stabilized their renal function and proteinuria. The incidence of new biopsy proven AR was 37%, and no new DSA were found or serious adverse events reported during follow-up. 4D could be a good option to halt the progression of renal damage due to rejection in KT.

MicroRNAs in kidney injury and disease.

MicroRNAs (miRNAs) are small non-coding RNAs that regulate gene expression by degrading or repressing the translation of their target messenger RNAs. As miRNAs are critical regulators of cellular homeostasis, their dysregulation is a crucial component of cell and organ injury. A substantial body of evidence indicates that miRNAs are involved in the pathophysiology of acute kidney injury (AKI), chronic kidney disease and allograft damage. Different subsets of miRNAs are dysregulated during AKI, chronic kidney disease and allograft rejection, which could reflect differences in the physiopathology of these conditions. miRNAs that have been investigated in AKI include miR-21, which has an anti-apoptotic role, and miR-214 and miR-668, which regulate mitochondrial dynamics. Various miRNAs are downregulated in diabetic kidney disease, including the miR-30 family and miR-146a, which protect against inflammation and fibrosis. Other miRNAs such as miR-193 and miR-92a induce podocyte dedifferentiation in glomerulonephritis. In transplantation, miRNAs have been implicated in allograft rejection and injury. Further work is needed to identify and validate miRNAs as biomarkers of graft function and of kidney disease development and progression. Use of combinations of miRNAs together with other molecular markers could potentially improve diagnostic or predictive power and facilitate clinical translation. In addition, targeting specific miRNAs at different stages of disease could be a promising therapeutic strategy.

Evaluation of Clazakizumab (Anti–Interleukin-6) in Patients With Treatment-Resistant Chronic Active Antibody-Mediated Rejection of Kidney Allografts

IntroductionInterleukin-6 (IL-6) is an important mediator of inflammation and activation of T cells, B cells, and plasma cells. Excessive IL-6 production is linked to human diseases characterized by unregulated antibody production, including alloimmunity, where persistence of donor-specific antibodies (DSAs), chronic active antibody-mediated rejection (cAMR), and graft loss are noted. Here, we report our experience investigating clazakizumab, a novel IL-6 inhibitor, in treating human leukocyte antigen (HLA)-sensitized patients with cAMR.MethodsBetween February 2018 and January 2019, 10 adults with biopsy-proven cAMR were enrolled in a phase 2, single-center, open-label study. Patients received clazakizumab 25 mg subcutaneously (s.c.) monthly for 12 months, with a 6-month protocol biopsy. Primary end points included patient survival, graft survival, estimated glomerular filtration rate (eGFR), and safety. Secondary end points assessed immune markers (DSAs, IgG, T-regulatory [Treg] cells). At 12 months, stable patients entered a long-term extension (LTE).ResultsLTE patients received clazakizumab for >2.5 years. Mean eGFRs showed significant declines from −24 months to study initiation (0 months) (52.8 ± 14.6 to 38.11 ± 12.23 ml/min per 1.73 m2, P = 0.03). However, after initiation of clazakizumab, eGFR stabilized at (41.6 ± 14.2 and 38.1 ± 20.3 ml/min per 1.73 m2, at 12 and 24 months, respectively). Banff 2017 analysis of pre- and post-treatment biopsies showed reductions in g+ptc and C4d scores. DSA reductions were seen in most patients. Adverse events (AEs) were minimal, and 2 graft losses occurred, both in patients who discontinued clazakizumab therapy at 6 months and 12 months after study initiation.ConclusionIn this small cohort of patients with cAMR, clazakizumab treatment showed a trend toward stabilization of eGFR and reductions in DSA and graft inflammation. No significant safety issues were observed. A randomized, placebo-controlled clinical trial (IMAGINE) of clazakizumab in cAMR treatment is underway (NCT03744910).

Recipient myeloperoxidase-producing cells regulate antibody-mediated acute versus chronic kidney allograft rejection.

Antibody-mediated rejection (ABMR) continues to be a major problem undermining the success of kidney transplantation. Acute ABMR of kidney grafts is characterized by neutrophil and monocyte margination in the tubular capillaries and by graft transcripts indicating NK cell activation, but the myeloid cell mechanisms required for acute ABMR have remained unclear. Dysregulated donor-specific antibody (DSA) responses with high antibody titers are induced in B6.CCR5–/– mice transplanted with complete MHC-mismatched A/J kidneys and are required for rejection of the grafts. This study tested the role of recipient myeloid cell production of myeloperoxidase (MPO) in the cellular and molecular components of acute ABMR. Despite induction of equivalent DSA titers, B6.CCR5–/– recipients rejected A/J kidneys between days 18 and 25, with acute ABMR, whereas B6.CCR5–/–MPO–/– recipients rejected the grafts between days 46 and 54, with histopathological features of chronic graft injury. On day 15, myeloid cells infiltrating grafts from B6.CCR5–/– and B6.CCR5–/–MPO–/– recipients expressed marked phenotypic and functional transcript differences that correlated with the development of acute versus chronic allograft injury, respectively. Near the time of peak DSA titers, activation of NK cells to proliferate and express CD107a was decreased within allografts in B6.CCR5–/–MPO–/– recipients. Despite high titers of DSA, depletion of neutrophils reproduced the inhibition of NK cell activation and decreased macrophage infiltration but increased monocytes producing MPO. Overall, recipient myeloid cells producing MPO regulate graft-infiltrating monocyte/macrophage function and NK cell activation that are required for DSA-mediated acute kidney allograft injury, and their absence switches DSA-mediated acute pathology and graft outcomes to chronic ABMR.

New concepts in chronic antibody-mediated kidney allograft rejection: prevention and treatment.

Chronic antibody-mediated rejection (AMR) is a cardinal cause of transplant failure, with currently no proven effective prevention or treatment. The present review will focus on new therapeutic concepts currently under clinical evaluation. One interesting treatment approach may be interference with interleukin-6 (IL-6) signaling to modulate B-cell immunity and donor-specific antibody (DSA) production. Currently, a large phase III randomized controlled trial is underway to clarify the safety and efficacy of clazakizumab, a high-affinity anti-IL-6 antibody, in chronic AMR. A prevention/treatment strategy may be costimulation blockade using belatacept to interfere with germinal center responses and DSA formation. In a recent uncontrolled study, belatacept conversion was shown to stabilize renal function and dampen AMR activity. Moreover, preliminary clinical results suggest efficacy of CD38 antibodies to deplete plasma and natural killer cells to treat AMR, with anecdotal reports demonstrating at least transient resolution of active rejection. There are promising concepts on the horizon for the prevention and treatment of chronic AMR. The design of adequately powered placebo-controlled trials to clarify the safety and efficacy of such new therapies, however, remains a big challenge, and will rely on the definition of precise surrogate endpoints predicting long-term allograft survival. Mapping the natural history of AMR would greatly help the understanding of who would derive benefits from treatment.

Orosomucoid 1 is involved in the development of chronic allograft rejection after kidney transplantation.

Chronic allograft rejection is the most common cause of long-term allograft failure. One reason is that current diagnostics and therapeutics for chronic allograft rejection are very limited. We here show that enhanced NFκB signaling in kidney grafts contributes to chronic active antibody-mediated rejection (CAAMR), which is a major pathology of chronic kidney allograft rejections. Moreover, we found that urinary orosomucoid 1 (ORM1) is a candidate marker molecule and therapeutic target for CAAMR. Indeed, urinary ORM1 concentration was significantly higher in kidney transplant recipients pathologically diagnosed with CAAMR than in kidney transplant recipients with normal histology, calcineurin inhibitor toxicity, or interstitial fibrosis and tubular atrophy. Additionally, we found that kidney biopsy samples with CAAMR expressed more ORM1 and had higher NFκB and STAT3 activation in tubular cells than samples from non-CAAMR samples. Consistently, ORM1 production was induced after cytokine-mediated NFκB and STAT3 activation in primary kidney tubular cells. The loss- and gain-of-function of ORM1 suppressed and promoted NFκB activation, respectively. Finally, ORM1-enhanced NFκB-mediated inflammation development in vivo. These results suggest that an enhanced NFκB-dependent pathway following NFκB and STAT3 activation in the grafts is involved in the development of chronic allograft rejection after kidney transplantation and that ORM1 is a non-invasive candidate biomarker and possible therapeutic target for chronic kidney allograft rejection.

Immunoproteasome inhibition prevents chronic antibody-mediated allograft rejection in renal transplantation

Chronic antibody-mediated rejection is the major cause of fading allograft function and loss after renal transplantation. Currently, pharmacological agents for the suppression of chronic antibody-mediated rejection are lacking. Non-selective proteasome inhibitors suppress antibody-mediated allograft rejection. However, extensive adverse side effects of these inhibitors severely limit their application. In contrast, immunoproteasome inhibition is effective in preclinical models of autoimmune diseases and was applied over weeks without obvious adverse side effects. ONX 0914, an immunoproteasome subunit LMP7 (β5i)-selective inhibitor, impeded the chronic rejection of kidneys transplanted from Fischer to allogeneic Lewis rats. ONX 0914 inhibited immunoproteasome induction both inimmune organs and renal allografts. Selective immunoproteasome inhibition reduced the numbers of B and plasma cells, and suppressed donor-specific alloantibody production. The infiltration of T cells, B cells and macrophages as well as interferon-γ, interleukin-17, IgG and complement deposition were reduced in renal allografts of ONX 0914-treated recipients. Chronic nephropathy was ameliorated and renal allograft function preserved, enabling long-term survival of recipients. Thus, our studies define a critical role of the immunoproteasome in chronic kidney allograft rejection and suggest immunoproteasome inhibition as a promising therapeutic approach to suppress chronic antibody-mediated rejection.

What's Hot, What's New From the 2016 American Transplant Congress.

From June 11-15, 2016 the American Transplant Congress, the joint meeting of the American Society of Transplantation and the American Society of Transplant Surgeons, held its annual meeting in Boston, MA. The meeting, attended by 5200 registrants, included pre-meeting conferences, focused topic sessions, and hundreds of high-quality presentations from the transplant field. This meeting report highlights key findings from specific basic science, translational, and clinical research presentations deemed to have notable impact in thematic areas. In particular, there were a number of transformative studies indicating important advances in the understanding of alloimmunity, chronic rejection, tolerance, and organ-specific outcomes. Many of these results are discussed in the context of the published literature to showcase rapid advances in the transplant field.

Mechanisms of antibody-mediated acute and chronic rejection of kidney allografts.

Antibody-mediated rejection is responsible for up to half of acute rejection episodes in kidney transplant patients and more than half of late graft failures. Antibodies cause acute graft abnormalities that are distinct from T cell-mediated rejection and at later times posttransplant, a distinct pathologic lesion is associated with capillary basement membrane multilayering and glomerulopathy. Despite the importance of donor-reactive antibodies as the leading cause of kidney graft failure, mechanisms underlying antibody-mediated acute and chronic kidney graft injury are poorly understood. Here, we review recent insights provided from clinical studies as well as from animal models that may help to identify new targets for therapy. Studies of biopsies from kidney grafts in patients with donor-specific antibody versus those without have utilized analysis of pathologic lesions and gene expression to identify the distinct characteristics of antibody-mediated rejection. These analyses have indicated the presence of natural killer cells and their activation during antibody-mediated rejection. The impact of studies of antibody-mediated allograft injury in animal models have lagged behind these clinical studies, but have been useful in testing the activation of innate immune components within allografts in the presence of donor-specific antibodies. Most insights into processes of antibody-mediated rejection of kidney grafts have come from carefully designed clinical studies. However, several new mouse models of antibody-mediated kidney allograft rejection may replicate the abnormalities observed in clinical kidney grafts and may be useful in directly testing mechanisms that underlie acute and chronic antibody-mediated graft injury.

Potential hyperacute renal rejection due to non-hla antibody in a pediatric patient

Non-HLA antigen targets have been associated with hyperacute, acute, and chronic kidney allograft rejection. Although there is controversy regarding the predictive role of non-HLA antibodies (Abs) in transplant (Txp) outcome - there are cases that indicate causality between the presence of such Abs and graft loss. A 17 month old boy with end-stage kidney disease, secondary to kidney dysplasia, received a living donor Txp from his uncle in April 2014. The presence of HLA abs was tested in 5 sera samples prior to Txp with a PRA of 7% and 0% for class I and II respectively (flow PRA). Single antigen testing confirmed the absence of donor specific HLA Abs (DSA). Initial and final flow cross matches were negative, as expected. During the Txp surgery, it was noted that the kidney became firm, urine output was below expectation and the child became increasingly pressor-dependent. Subsequently, the patient had an episode of ventricular tachycardia and an exploratory laparotomy demonstrated that the Txp kidney became tense and enlarged, with thrombosis of the renal vein. The kidney was nephrectomized within 48 hours and the patient’s status improved significantly. To investigate a potential role for HLA DSA, we tested a 2 days post-Txp serum sample, confirming the absence of HLA-DSA. We also repeated Abs testing on the pre-Txp serum sample ruling out HLA-DSA as the cause of rejection. To assess potential causes for this apparently hyperacute Ab mediated rejection, pre-Txp (pre-14 days) and post-Txp (post-24 days) samples were sent out for AT1R Abs screening and donor specific endothelial cell crossmatch (XM-One). Retrospective testing of a pre- and post-Txp sera for AT1R antibody was out of range for pre-Txp sample and the post-Txp sample was positive ( > 30 Units/ml). The XM-One assay using endothelial precursors isolated from the donor as targets was strongly positive using a pre-Txp serum but negative using post-Txp serum. Approximately two month’s post-Txp, the patient developed HLA Abs, on top of the AT1R antibodies. In conclusion, this patient still requires a kidney Txp and the question is how to proceed – shall we consider only obtaining an organ from a living donor? This would allow for the necessary time to run XM-One and potentially inhibit AT1R pathway with an AT 1 receptor antagonist. What to do if no living donor becomes available?

Repeated Injections of IL-2 Break Renal Allograft Tolerance Induced via Mixed Hematopoietic Chimerism in Monkeys.

Tolerance of allografts achieved in mice via stable mixed hematopoietic chimerism relies essentially on continuous elimination of developing alloreactive T cells in the thymus (central deletion). Conversely, while only transient mixed chimerism is observed in nonhuman primates and patients, it is sufficient to ensure tolerance of kidney allografts. In this setting, it is likely that tolerance depends on peripheral regulatory mechanisms rather than thymic deletion. This implies that, in primates, upsetting the balance between inflammatory and regulatory alloimmunity could abolish tolerance and trigger the rejection of previously accepted renal allografts. In this study, six monkeys that were treated with a mixed chimerism protocol and had accepted a kidney allograft for periods of 1-10 years after withdrawal of immunosuppression received subcutaneous injections of IL-2 cytokine (0.6-3 × 10(6) IU/m(2) ). This resulted in rapid rejection of previously tolerated renal transplants and was associated with an expansion and reactivation of alloreactive pro-inflammatory memory T cells in the host's lymphoid organs and in the graft. This phenomenon was prevented by anti-CD8 antibody treatment. Finally, this process was reversible in that cessation of IL-2 administration aborted the rejection process and restored normal kidney graft function.

Transplantation: Molecular diagnosis of kidney transplant rejection.

Acute or chronic antibody-mediated rejection (ABMR) of kidney allografts is currently diagnosed by the presence of donor-specific alloantibodies and distinct pathological findings in biopsy samples. A new study highlights the potential of molecular diagnostics incorporated into standard criteria for acute ABMR to help identify patients at risk of graft loss.

TIPE2, a Novel Biomarker for Clinical Chronic Kidney Allograft Rejection

Tumor necrosis factor-a--induced protein 8-like 2 (TIPE2) has an essential role in immune homeostasis, yet the relationship between TIPE2 expression and allograft rejection has not been addressed. Dependent on clinical diagnosis, 96 kidney transplant recipients were divided into three groups, long-term survival group, acute rejection group (AR) and chronic rejection group (CR). Thirty-two healthy volunteers were used as a control group. The expression of TIPE2 in peripheral blood mononuclear cells (PBMC) and kidney biopsy samples was performed using reverse transcript-polymerase chain reaction, immunohistochemistry and immunofluorescence. The expression of TIPE2 in PBMC of CR group was significantly higher than that of the healthy control (P < 0.001), but TIPE2 expression in AR group was lower than that of control individuals (P < 0.05). The renal expression of TIPE2 in allograft tissue of CR was significantly lower and its expression in AR slightly lower than in normal kidneys. The positive correlation between TIPE2 expression in PBMCs and the CR of allo-kidney grafts indicates that detection of TIPE2 in the blood samples may be used as one of the diagnosis molecular markers in clinical monitoring kidney chronic rejection.

Contributions of Direct and Indirect Alloresponses to Chronic Rejection of Kidney Allografts in Nonhuman Primates

The relative contribution of direct and indirect allorecognition pathways to chronic rejection of allogeneic organ transplants in primates remains unclear. In this study, we evaluated T and B cell alloresponses in cynomolgus monkeys that had received combined kidney/bone marrow allografts and myeloablative immunosuppressive treatments. We measured donor-specific direct and indirect T cell responses and alloantibody production in monkeys (n = 5) that did not reject their transplant acutely but developed chronic humoral rejection (CHR) and in tolerant recipients (n = 4) that never displayed signs of CHR. All CHR recipients exhibited high levels of anti-donor Abs and mounted potent direct T cell alloresponses in vitro. Such direct alloreactivity could be detected for more than 1 y after transplantation. In contrast, only two of five monkeys with CHR had a detectable indirect alloresponse. No indirect alloresponse by T cells and no alloantibody responses were found in any of the tolerant monkeys. Only one of four tolerant monkeys displayed a direct T cell alloresponse. These observations indicate that direct T cell alloresponses can be sustained for prolonged periods posttransplantation and result in alloantibody production and chronic rejection of kidney transplants, even in the absence of detectable indirect alloreactivity.

Peritubular capillary basement membrane changes in chronic renal allograft rejection

Marked peritubular capillary basement membrane (PTCBM) multilayering, the ultrastructural feature of chronic antibody-mediated rejection (ABMR) of kidney allografts, was found to correspond histologically to PTCs with thickened BMs; such PTCs have been suggested as a novel histological marker of chronic rejection. We investigated whether scoring of PTCBM thickening can substitute the ultrastructural search for PTCBM multilayering. The thickening was graded in PAS- and Jones-stained sections in 110 biopsies from recipients with a late dysfunction, all examined ultrastructurally for transplant capillaropathy (≥3PTCs with ≥5BM layers). Grade 0 indicated no thickening. Grade 1 and grade 2 were assigned when the PTCBMs were as thick as or thicker than those of the non-atrophic tubules, and duplication/chain-like lamination of the PTCBM was noted in ≤3 or ≥4 high-power fields, respectively. The series was enrolled in subgroups of those with and those without histopathological lesions of chronic rejection. Fifty-six biopsies displayed lesions of chronic ABMR. Transplant capillaropathy was demonstrated in 40 biopsies. Grade 2 thickening furnished a substantial interobserver concordance rate (κ = 0.803) and correlated with the transplant capillaropathy. Jones staining performed somewhat better in scoring than PAS staining. Grade 2 thickening was verified in 35 biopsies involving chronic ABMR, and in one control biopsy (sensitivity 61.4%, specificity 0.98). Grade 1 thickening was not suggestive of chronic ABMR at all. In conclusion, grade 2 thickening can be regarded as the histopathological lesion of chronic ABMR; however, electron microscopy remains the gold standard in the assessment of PTCBM changes.

The role of HIF-1 in up-regulating MICA expression on human renal proximal tubular epithelial cells during hypoxia/reoxygenation

BackgroundHuman major histocompatibility complex class I-related chain A (MICA) plays a dual role in adaptive and innate immune responses. Increasing evidence demonstrates that MICA is closely correlated with acute and chronic kidney allograft rejection. Therefore, understanding the activation mechanisms of MICA is important in kidney transplantation. We previously demonstrated that ischemia/reperfusion injury (IRI) could up-regulate MICA expression on mouse kidney allografts. Since hypoxia-inducible factor-1 (HIF-1) is the master regulator of cellular adaptive responses to hypoxia during IRI, here we investigate whether HIF-1 could up-regulate MICA expression and its influence on NK cell cytotoxicity.ResultsWe find that HIF-1alpha plays an important role in up-regulating MICA expression, inducing IFNgamma secretion and NK cell cytotoxicity during hypoxia/reoxygenation. First, we generated a HIF-1alphaDELTAODD-expressing adenovirus to stably and functionally express HIF-1alpha in human renal proximal tubular epithelial (HK-2) cells under normoxia conditions. HIF-1alpha over-expression in HK-2 cells induces MICA expression and enhances NK cell cytotoxic activity towards cells that express HIF-1alpha. Second, we used a hypoxia/reoxygenation cell model to simulate IRI in vitro and found that the suppression of HIF-1alpha by RNAi induces down-regulation of MICA expression and inhibits NK cytotoxicity. In antibody blocking experiments, an anti-MICA mAb was able to down-regulate NK cell cytotoxic activity towards HK-2 cells that over-expressed HIF-1alpha. Moreover, when NK cells were co-cultured with the HK-2 cells expressing MICA, which was up-regulated by over-expression of HIF-1alpha, there was a significant increase in the secretion of IFNgamma. In the presence of the blocking MICA mAb, IFNgamma secretion was significantly decreased.ConclusionsThese results demonstrate that hypoxia/reoxygenation-promoted MICA expression on HK-2 cells is through a HIF-1 pathway. The increased IFNgamma secretion and enhanced NK cell cytotoxicity was mainly due to the surface expression of MICA induced by over-expression of HIF-1alpha. This study enhances our understanding of MICA activation mechanisms during kidney transplantation and provides insights into how IRI can influence transplant outcome. Moreover, these findings might be also important for developing strategies to reduce the effect of MICA in kidney transplant outcomes in the future.

Chronic Humoral Rejection of Human Kidney Allografts Is Associated with MMP-2 Accumulation in Podocytes and its Release in the Urine

Chronic humoral rejection (CHR) is an important cause of late graft failures following kidney transplantation. Overall, the pathophysiology of CHR is poorly understood. Matrix metalloproteinase-2 (MMP-2), a type IV collagenase, has been implicated in chronic kidney disease and allograft rejection in previous studies. We examined the presence of MMP-2 in allograft biopsies and in the urine of kidney transplant recipients with CHR. MMP-2 staining was detected by immunohistochemistry in podocytes for all CHR patients but less frequently in patients with other renal complications. Urinary MMP-2 levels were also significantly higher in CHR patients (median 4942 pg/mL, N = 27) compared to non-CHR patients (median 598 pg/mL, N = 65; p < 0.001). Elevated urinary MMP-2 correlated with higher levels of proteinuria in both CHR and non-CHR patients. Longitudinal analysis indicated that increase in urine MMP-2 coincided with initial diagnosis of CHR as documented by the biopsies. Using an enzymatic assay, we demonstrated that MMP-2 was present in its active form in the urine of patients with CHR. Overall, our findings associate MMP-2 with glomerular injury as well as interstitial fibrosis and tubular atrophy observed in patients with CHR.

The association between eNOS intron 4 VNTR polymorphism and delayed graft function of kidney allografts

Nitric oxide (NO) is a multifunctional agent which serves as a key signaling molecule in physiological processes such as host defense, neuronal communication, and the regulation of vascular tone. Different polymorphic variations have been identified in the human NOS3 (eNOS) gene.The aim of the present study was to examine the association between polymorphisms of the NOS3 gene (G894T substitution within exon 7 and intron 4 VNTR polymorphism) and the development of delayed graft function as well as acute and chronic rejection.One hundred eighty-seven recipients of first renal transplants were included in the study. There were no significant associations between these polymorphisms and acute and chronic kidney allograft rejection. The intron 4 polymorphism was associated with delayed graft function after transplantation. The results of this study suggest that patients with the a allele of the eNOS intron 4 VNTR polymorphism may be predisposed to delayed graft function.