Chronic Allograft Injury Research Articles

Chronic Allograft Injury.

With the incremental improvements in long-term kidney transplant survival, there is renewed focus on what causes failure of the transplanted allograft. Over the past decade, our understanding of the injuries that lead to loss of graft function over time has evolved. Chronic allograft injury includes both immune-mediated and nonimmune-mediated injuries, which may involve the organ donor, the recipient, or both. The targets of injury include the kidney tubular epithelium, the endothelium, and the glomerulus. As a response to injury, there are the expected tissue remodeling and repair processes. However, if inflammation persists, which is not uncommon in the transplant setting, the resulting maladaptive response is matrix deposition and/or fibrosis. This ultimately leads to declining graft function and, finally, failure. With our advancing knowledge of the multiple etiologies and mechanisms, enhanced by more recent cohort studies in humans, there is an opportunity to identify those at greater risk to initiate new strategies to ameliorate the process. Although the most recent studies focus on immune-mediated injuries, there is a critical need to identify both markers of injury and mechanisms of injury. In this review, we highlight the findings of recent studies, highlight the potential therapeutic targets, and identify the continued unmet need for understanding the mechanisms of late graft failure.

Noninvasive Assessment of the Alloimmune Response in Kidney Transplantation.

Transplantation remains the optimal mode of kidney replacement therapy, but unfortunately long-term graft survival after 1year remains suboptimal. The main mechanism of chronic allograft injury is alloimmune, and current clinical monitoring of kidney transplants includes measuring serum creatinine, proteinuria, and immunosuppressive drug levels. The most important biomarker routinely monitored is human leukocyte antigen (HLA) donor-specific antibodies (DSAs) with the frequency based on underlying immunologic risk. HLA-DSA should be measured if there is graft dysfunction, immunosuppression minimization, or nonadherence. Antibody strength is semiquantitatively estimated as mean fluorescence intensity, with titration studies for equivocal cases and for following response to treatment. Determination of invitro C1q or C3d positivity or HLA-DSA IgG subclass analysis remains of uncertain significance, but we do not recommend these for routine use. Current evidence does not support routine monitoring of non-HLA antibodies except anti-angiotensin II type 1 receptor antibodies when the phenotype is appropriate. The monitoring of both donor-derived cell-free DNA in blood or gene expression profiling of serum and/or urine may detect subclinical rejection, although mainly as a supplement and not as a replacement for biopsy. The optimal frequency and cost-effectiveness of using these noninvasive assays remain to be determined. We review the available literature and make recommendations.

Renal allograft rejection with thrombotic microangiopathy associated with a Kidd blood group system alloantibody

Abstract Introduction/Objective The Kidd blood group antigens are urea transporters found on the surface of red blood cells, renal tubular epithelial cells, and endothelial cells in the renal medulla and vasa recta. While controversial, some reports have described an association between Kidd antigen donor/recipient mismatches and kidney transplant rejection when recipients possess or form anti-Kidd alloantibodies. To date, none of these reports have described development of a thrombotic microangiopathy (TMA) in the renal graft associated with these antibodies. We describe a case of fulminant renal transplant rejection associated with TMA in a patient with anti-Jk(a) alloantibodies who received a deceased-donor kidney transplant (DDKT). Methods/Case Report A 64-year-old woman with end-stage renal disease secondary to AL amyloidosis caused by plasma cell neoplasm received a DDKT associated with delayed graft function. No pre- or post-transplant donor specific antibodies (DSA) were detected, the flow crossmatch testing was negative, and a pre-operative type and screen identified anti-Jk(a) alloantibodies. On post-transplant day 5, her creatinine remained elevated at 6 mg/dL (ref range: 0.4–1.3 mg/dL) with an acute drop in platelets and undetectable haptoglobin. Allograft biopsy showed a combination of TMA with some additional evidence of acute cellular rejection. Tacrolimus was stopped to rule out drug-induced TMA, and the workup showed negative Shiga toxin, normal ADAMTS13 activity, negative atypical HUS genetic testing, and negative antiphospholipid syndrome testing. Genotyping of the donor kidney was positive for the Jk(a) antigen. Eculizumab, IVIG, and a trial of 8 sessions of therapeutic plasma exchange (TPE) were administered. Her creatinine improved (1.93–2.05 mg/dL), indicating a significant antibody-mediated etiology to her delayed graft function. About one month later, her creatinine worsened, and she received another trial of TPE with IVIG and eculizumab. Despite a mild decrease in her creatinine, repeat biopsies showed acute cellular rejection, persistent TMA, and chronic allograft injury. No DSAs were ever detected. Her creatinine never recovered, and she is now dialysis-dependent. Results (if a Case Study enter NA) NA Conclusion We speculate that anti-Jk(a) antibodies interacting with a Jk(a)-positive donor kidney account for graft TMA. This case underscores the potential importance of matching Kidd antigens in kidney transplantation.

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.

Donor derived cell free DNA% is elevated with pathogens that are risk factors for acute and chronic lung allograft injury

Acute and chronic forms of lung allograft injury are associated with specific respiratory pathogens. Donor-derived cell free DNA (ddcfDNA) has been shown to be elevated with acute lung allograft injury and predictive of long-term outcomes. We examined the %ddcfDNA values at times of microbial isolation from bronchoalveolar lavage (BAL). Two hundred and six BAL samples from 51 Lung Transplant Recipients (LTRs) with concurrently available plasma %ddcfDNA were analyzed along with microbiology and histopathology. Microbial species were grouped into bacterial, fungal, and viral and "higher risk" and "lower risk" cohorts based on historical association with downstream allograft dysfunction. Analyses were performed to determine pathogen category association with %ddcfDNA, independent of inter-subject variability. Presence of microbial isolates in BAL was not associated with elevated %ddcfDNA compared to samples without isolates. However, "higher risk" bacterial and viral microbes showed greater %ddcfDNA values than lower risk species (1.19% vs. 0.65%, p < 0.01), independent of inter-subject variability. Histopathologic abnormalities concurrent with pathogen isolation were associated with higher %ddcfDNA compared to isolation episodes with normal histopathology (medians 1.23% and 0.66%, p=0.05). Assessments showed no evidence of correlation between histopathology or bronchoscopy indication and presence of higher risk vs. lower risk pathogens. %ddcfDNA is higher among cases of microbial isolation with concurrent abnormal histopathology and with isolation of higher risk pathogens known to increase risk of allograft dysfunction. Future studies should assess if %ddcfDNA can be used to stratify pathogens for risk of CLAD and identify pathogen associated injury prior to histopathology.

FC 120MAGNETIC RESONANCE IMAGING TEXTURE ANALYSIS PREDICTS INTERSTITIAL FIBROSIS / TUBULAR ATROPHY IN TRANSPLANTED KIDNEYS: A SINGLE CENTER CROSS-SECTIONAL STUDY

Abstract Background and Aims Interstitial fibrosis / tubular atrophy (IFTA) is a common, irreversible and progressive form of chronic allograft injury, and it is considered a critical predictor of kidney allograft outcomes. Inflammation, both microvascular and interstitial, is on the contrary regarded as a reversible form of graft injury. Since treatments for rejection and other causes of graft dysfunction bear substantial toxicity and could have limited efficacy, the extent of irreversible graft scarring is a crucial information for the clinician, to evaluate risks and benefits of specific therapies. The diagnosis of kidney graft pathology is acquired through graft biopsy, which is an invasive procedure and can be subjected to sampling bias. Magnetic resonance imaging (MRI), especially with functional techniques, has emerged as a possibility for non-invasive estimation of tissue fibrosis; nevertheless, functional MRI is not widely available. Texture analysis MRI (TA-MRI) is a radiomic technique that provides a quantitative assessment of tissue heterogeneity from standard MRI images, generating features that can be fitted into a machine-learning model to assess their ability to predict clinical or histological parameters. Method Single-center cross-sectional observational cohort study enrolling kidney transplant recipients who underwent graft biopsy and graft MRI imaging within 6 months from biopsy, both on clinical indication, at the “Azienda Ospedaliero-Universitaria di Modena”, Italy. The study was approved by the local Ethical Committee (AOU0010167/20). The primary outcome was to identify the best TA-MRI features subset for estimation of IFTA &amp;gt; 50% in graft biopsy. Secondary outcomes were estimation of: IFTA &amp;gt; 25%, presence of total inflammation (ti) and microvascular inflammation (glomerulitis + peritubular capillaritis [g+ptc]). Graft biopsy was reported according to Banff 2017 system. Radiomic analysis was performed on axial T2 pre-contrast and T1 fat-suppressed post-contrast sequences. The whole renal parenchyma (PAR) was segmented and labelled on T2 and T1, renal cortex (COR) only on T2. After imaging preprocessing, PyRadiomics was used to extract radiomic features. After removal of shape features, 93 features were included and reduced using LASSO regression to produce radiomic signatures. These were introduced in Machine Learning (ML) models to test the association with outcomes. Results are reported as AUC and a value of sensitivity and specificity. Results Sixty patients were included in the study, and 67 graft biopsy – graft MRI pairs were available for analysis. Demographic and clinical characteristics of enrolled patients are depicted in table 1; histological diagnosis and main Banff histological parameters from graft biopsies in table 2. Among ML models, three showed an acceptable performance. T2 COR “firstorder_minimum/firstorder_range/glrlm_run_entropy” for IFTA&amp;gt;50% (AUC=0.77, sensitivity=73%, specificity=71%), T1 PAR “firstorder_energy” for IFTA&amp;gt;25% (AUC=0.71, sensitivity=74%, specificity=51%), T1 PAR “firstorder_energy/gldm_small_dependence_low_gray_level_emphasis” for g+ptc &amp;gt;0 (AUC=0.74, sensitivity= 78%, specificity=68%); see figures 1–3. No acceptable prediction was detected for ti &amp;gt;0. Conclusion Our study shows that TA-MRI feature signatures can predict the degree of IFTA in graft biopsies, with an acceptable diagnostic performance. These results suggest to further investigating TA-MRI from standard MRI sequences as potential tool to assess graft chronic parenchymal injury. Moreover, since graft biopsy results can be jeopardized by limited sample size, we hypothesize that evaluation of IFTA through TA-MRI could provide more comprehensive information regarding the whole parenchyma. To test this hypothesis, we are currently evaluating the association of TA-MRI radiomic features and baseline eGFR and eGFR variation over time.

Curcumin Blunts IL-6 Dependent Endothelial-to-Mesenchymal Transition to Alleviate Renal Allograft Fibrosis Through Autophagy Activation.

Fibrosis contributes to graft loss in chronic renal allograft injury. Endothelial‐to‐mesenchymal transition (EndMT) plays an important role in the development of fibrosis following kidney transplantation. Autophagy plays an important role in the homeostasis of diverse cell types including endothelial cells. Here we demonstrate that inhibition of autophagy by treatment with 3-methyladenine (3-MA) or by silencing autophagy-related (ATG)5 promoted interleukin (IL)-6–dependent EndMT in human umbilical vein endothelial cells (HUVECs) and human renal glomerular endothelial cells (HRGECs), and autophagy inactivation was associated with EndMT in patients with chronic allograft dysfunction. IL-6 level was significantly higher in the culture medium of HUVECs transfected with ATG5 siRNA or treated with 3-MA compared to the respective control groups. IL-6 application induced EndMT in HUVECs and HRGECs, whereas antibody-mediated neutralization of IL-6 suppressed EndMT induced by ATG5 silencing. The protective role of curcumin (Cur) against allograft fibrosis was confirmed in a rat kidney transplantation model of F344 donors to Lewis recipients. Curcumin—a natural polyphenol compound with known antifibrotic effects in various tissues—alleviated IL-6–induced EndMT and promoted autophagy in the allografted organ and in HUVECs. This is the first demonstration of the role of autophagy in renal allograft fibrosis; our findings indicate that curcumin can alleviate chronic renal allograft injury by suppressing IL-6–dependent EndMT via activation of autophagy.

IL-21 Receptor Blockade Shifts the Follicular T Cell Balance and Reduces De Novo Donor-Specific Antibody Generation.

Donor-specific antibodies (DSAs) play a key role in chronic kidney allograft injury. Follicular T helper (Tfh) cells trigger the humoral alloimmune response and promote DSA generation, while T-follicular regulatory (Tfr) cells inhibit antibody production by suppressing Tfh and B cells. Interleukin (IL)-21 exerts a distinct effect on Tfh and Tfr. Here, we studied whether blocking IL-21R with anti-IL-21R monoclonal antibody (αIL-21R) changes the Tfh/Tfr balance and inhibits DSA generation. First, we investigated the impact of αIL-21R on CD4+ T cell proliferation and apoptosis. The results showed that αIL-21R did not have cytotoxic effects on CD4+ T cells. Next, we examined Tfh and regulatory T cells (Tregs) in an in vitro conditioned culture model. Naïve CD4+ T cells were isolated from 3-month-old C57BL/6 mice and cultured in Tfh differentiation inducing conditions in presence of αIL-21R or isotype IgG and differentiation was evaluated by CXCR5 expression, a key Tfh marker. αIL-21R significantly inhibited Tfh differentiation. In contrast, under Treg differentiation conditions, FOXP3 expression was inhibited by IL-21. Notably, αIL-21R rescued IL-21-inhibited Treg differentiation. For in vivo investigation, a fully mismatched skin transplantation model was utilized to trigger the humoral alloimmune response. Consistently, flow cytometry revealed a reduced Tfh/Tfr ratio in recipients treated with αIL-21R. Germinal center response was evaluated by flow cytometry and lectin histochemistry. We observed that αIL-21R significantly inhibited germinal center reaction. Most importantly, DSA levels after transplantation were significantly inhibited by αIL-21R at different time points. In summary, our results demonstrate that αIL-21R shifts the Tfh/Tfr balance toward DSA inhibition. Therefore, αIL-21R may be a useful therapeutic agent to prevent chronic antibody mediated rejection after organ transplantation.

Assessment of chronic allograft injury in renal transplantation using diffusional kurtosis imaging

BackgroundChronic allograft injury (CAI) is a significant reason for which many grafts were lost. The study was conducted to assess the usefulness of diffusional kurtosis imaging (DKI) technology in the non-invasive assessment of CAI.MethodsBetween February 2019 and October 2019, 110 renal allograft recipients were included to analyze relevant DKI parameters. According to estimated glomerular filtration rate (eGFR) (mL/min/ 1.73 m2) level, they were divided to 3 groups: group 1, eGFR ≥ 60 (n = 10); group 2, eGFR 30–60 (n = 69); group 3, eGFR < 30 (n = 31). We performed DKI on a clinical 3T magnetic resonance imaging system. We measured the area of interest to determine the mean kurtosis (MK), mean diffusivity (MD), and apparent diffusion coefficient (ADC) of the renal cortex and medulla. We performed a Pearson correlation analysis to determine the relationship between eGFR and the DKI parameters. We used the receiver operating characteristic curve to estimate the predicted values of DKI parameters in the CAI evaluation. We randomly selected five patients from group 2 for biopsy to confirm CAI.ResultsWith the increase of creatinine, ADC, and MD of the cortex and medulla decrease, MK of the cortex and medulla gradually increase. Among the three different eGFR groups, significant differences were found in cortical and medullary MK (P = 0.039, P < 0.001, P < 0.001, respectively). Cortical and medullary ADC and MD are negatively correlated with eGFR (r = − 0.49, − 0.44, − 0.57, − 0.57, respectively; P < 0.001), while cortical and medullary MK are positively correlated with eGFR (r = 0.42, 0.38; P < 0.001). When 0.491 was set as the cutoff value, MK's CAI assessment showed 87% sensitivity and 100% specificity. All five patients randomly selected for biopsy from the second group confirmed glomerulosclerosis and tubular atrophy/interstitial fibrosis.ConclusionThe DKI technique is related to eGFR as allograft injury progresses and is expected to become a potential non-invasive method for evaluating CAI.

Impact of Subclinical Borderline Inflammation on Kidney Transplant Outcomes.

Surveillance biopsies permit early detection of subclinical inflammation before clinical dysfunction, but the impact of detecting early subclinical phenotypes remains unclear. We conducted a single-center retrospective cohort study of 441 consecutive kidney transplant recipients between 2015 and 2018 with surveillance biopsies at 6 months post-transplant. We tested the hypothesis that early subclinical inflammation (subclinical borderline changes, T cell-mediated rejection, or microvascular injury) is associated with increased incidence of a composite endpoint including acute rejection and allograft failure. Using contemporaneous Banff criteria, we detected subclinical inflammation in 31%, with the majority (75%) having a subclinical borderline phenotype (at least minimal inflammation with mild tubulitis [>i0t1]). Overall, subclinical inflammation was independently associated with the composite endpoint (adjusted hazard ratio, 2.88; 1.11-7.51; P = 0.03). The subgroup with subclinical borderline inflammation, predominantly those meeting the Banff 2019 i1t1 threshold, was independently associated with 5-fold increased hazard for the composite endpoint (P = 0.02). Those with concurrent subclinical inflammation and subclinical chronic allograft injury had worse outcomes. The effect of treating subclinical inflammation was difficult to ascertain in small heterogeneous subgroups. Subclinical acute and chronic inflammation are common at 6 months post-transplant in kidney recipients with stable allograft function. The subclinical borderline phenotype with both tubulitis and interstitial inflammation was independently associated with poor long-term outcomes. Further studies are needed to elucidate the role of surveillance biopsies for management of allograft inflammation in kidney transplantation.

Profiling the liver graft.

Achieving operational tolerance remains a priority in liver transplantation. Although several biomarkers of tolerance and rejection have been identified, few have been reproducible and validated across centers, and therefore have yet to reach clinical practice. Here we summarize findings from prior seminal studies and review current developments in profiling the liver allograft. Substantial efforts and progress have been made in the recent years towards the discovery of reliable biomarkers that can predict and guide successful immunosuppression withdrawal. Recent studies have also investigated the transcriptomic signatures underlying not only acute rejection but also subclinical inflammation and chronic allograft injury. As new genomic and sequencing technologies continue to develop, clinical trials are underway to validate biomarkers of tolerance, as well as better understand the mechanisms of both acute and subclinical rejection, with the goal of maximizing allograft survival. Altogether, this will hopefully enable the implementation of immunosuppression withdrawal protocols into clinical practice and make operational tolerance reliably attainable in the near future.

Up-regulation of CD163 expression in subpopulations of blood monocytes after kidney allograft transplantation.

M2 macrophages expressing CD163 are known to suppress immune responses but have been also found in biopsies of patients with chronic kidney allograft injury associated with interstitial fibrosis. The aim of our study was to evaluate the expression of CD163 in blood monocytes, precursors of tissue macrophages, in kidney allograft recipients with uncomplicated outcome (n=94) compared with those developing acute rejection (n=44). Blood samples were collected before the transplantation and at 1 week, 1 month and 1 year. The expression of CD163 increased during the first week after the transplantation not only in classical (CD14+CD16-) but also in intermediate (CD14+CD16+) and nonclassical (CD14lowCD16+) monocytes in all patients regardless of their rejection status. In patients developing acute rejection, higher pre-transplant expression of CD163 on blood monocytes was found. In vitro experiments confirmed strong induction of membrane CD163 on monocytes together with CD206 (an alternative marker of M2 macrophages) in response to IL-10. We assume from our data that dramatic upregulation of CD163 by peripheral blood monocytes may have a pathophysiological role in early phases after kidney allograft transplantation and high pre-transplant expression of CD163 on blood monocytes might be involved in events leading to acute rejection.

Donor myeloid derived suppressor cells (MDSCs) prolong allogeneic cardiac graft survival through programming of recipient myeloid cells in vivo

Solid organ transplantation is a lifesaving therapy for patients with end-organ disease. Current immunosuppression protocols are not designed to target antigen-specific alloimmunity and are uncapable of preventing chronic allograft injury. As myeloid-derived suppressor cells (MDSCs) are potent immunoregulatory cells, we tested whether donor-derived MDSCs can protect heart transplant allografts in an antigen-specific manner. C57BL/6 (H2Kb, I-Ab) recipients pre-treated with BALB/c MDSCs were transplanted with either donor-type (BALB/c, H2Kd, I-Ad) or third-party (C3H, H2Kk, I-Ak) cardiac grafts. Spleens and allografts from C57BL/6 recipients were harvested for immune phenotyping, transcriptomic profiling and functional assays. Single injection of donor-derived MDSCs significantly prolonged the fully MHC mismatched allogeneic cardiac graft survival in a donor-specific fashion. Transcriptomic analysis of allografts harvested from donor-derived MDSCs treated recipients showed down-regulated proinflammatory cytokines. Immune phenotyping showed that the donor MDSCs administration suppressed effector T cells in recipients. Interestingly, significant increase in recipient endogenous CD11b+Gr1+ MDSC population was observed in the group treated with donor-derived MDSCs compared to the control groups. Depletion of this endogenous MDSCs with anti-Gr1 antibody reversed donor MDSCs-mediated allograft protection. Furthermore, we observed that the allogeneic mixed lymphocytes reaction was suppressed in the presence of CD11b+Gr1+ MDSCs in a donor-specific manner. Donor-derived MDSCs prolong cardiac allograft survival in a donor-specific manner via induction of recipient’s endogenous MDSCs.

Understanding, predicting and achieving liver transplant tolerance: from bench to bedside.

In the past 40 years, liver transplantation has evolved from a high-risk procedure to one that offers high success rates for reversal of liver dysfunction and excellent patient and graft survival. The liver is the most tolerogenic of transplanted organs; indeed, immunosuppressive therapy can be completely withdrawn without rejection of the graft in carefully selected, stable long-term liver recipients. However, in other recipients, chronic allograft injury, late graft failure and the adverse effects of anti-rejection therapy remain important obstacles to improved success. The liver has a unique composition of parenchymal and immune cells that regulate innate and adaptive immunity and that can promote antigen-specific tolerance. Although the mechanisms underlying liver transplant tolerance are not well understood, important insights have been gained into how the local microenvironment, hepatic immune cells and specific molecular pathways can promote donor-specific tolerance. These insights provide a basis for the identification of potential clinical biomarkers that might correlate with tolerance or rejection and for the development of novel therapeutic targets. Innovative approaches aimed at promoting immunosuppressive drug minimization or withdrawal include the adoptive transfer of donor-derived or recipient-derived regulatory immune cells to promote liver transplant tolerance. In this Review, we summarize and discuss these developments and their implications for liver transplantation.

Inflammation in areas of fibrosis: The DeKAF prospective cohort.

Inflammation in areas of fibrosis (i-IFTA) in posttransplant biopsy specimens has been associated with decreased death-censored graft survival (DC-GS). Additionally, an i-IFTA score≥2 is part of the diagnostic criteria for chronic active TCMR (CA TCMR). We examined the impact of i-IFTA and t-IFTA (tubulitis in areas of atrophy) in the first biopsy for cause after 90days posttransplant (n=598); mean (SD) 1.7±1.4years posttransplant. I-IFTA, present in 196 biopsy specimens, was strongly correlated with t-IFTA, and Banff i. Of the 196, 37 (18.9%) had a previous acute rejection episode; 96 (49%) had concurrent i score=0. Unlike previous studies, i-IFTA=1 (vs 0) was associated with worse 3-year DC-GS: (i-IFTA=0, 81.7%, [95% CI 77.7 to 85.9%]); i-IFTA=1, 68.1%, [95% CI 59.7 to 77.6%]; i-IFTA=2, 56.1%, [95% CI 43.2 to 72.8%], i-IFTA=3, 48.5%, [95% CI 31.8 to 74.0%]). The association of i-IFTA with decreased DC-GS remained significant when adjusted for serum creatinine at the time of the biopsy, Banff i, ci and ct, C4d and DSA. T-IFTA was similarly associated with decreased DC-GS. Of these indication biopsies, those with i-IFTA≥2, without meeting other criteria for CA TCMR had similar postbiopsy DC-GS as those with CA TCMR. Those with i-IFTA=1 and t≥2, ti≥2 had postbiopsy DC-GS similar to CA TCMR. Biopsies with i-IFTA=1 had similar survival as CA TCMR when biopsy specimens also met Banff criteria for TCMR and/or AMR. Studies of i-IFTA and t-IFTA in additional cohorts, integrating analyses of Banff scores meeting criteria for other Banff diagnoses, are needed.

Evidence for the alloimmune basis and prognostic significance of Borderline T cell-mediated rejection.

Prognostic biomarkers of T cell–mediated rejection (TCMR) have not been adequately studied in the modern era. We evaluated 803 renal transplant recipients and correlated HLA‐DR/DQ molecular mismatch alloimmune risk categories (low, intermediate, high) with the severity, frequency, and persistence of TCMR. Allograft survival was reduced in recipients with Banff Borderline (hazard ratio [HR] 2.4, P = .003) and Banff ≥ IA TCMR (HR 4.3, P < .0001) including a subset who never developed de novo donor‐specific antibodies (P = .002). HLA‐DR/DQ molecular mismatch alloimmune risk categories were multivariate correlates of Banff Borderline and Banff ≥ IA TCMR and correlated with the severity and frequency of rejection episodes. Recipient age, HLA‐DR/DQ molecular mismatch category, and cyclosporin vs tacrolimus immunosuppression were independent correlates of Banff Borderline and Banff ≥ IA TCMR. In the subset treated with tacrolimus (720/803) recipient age, HLA‐DR/DQ molecular mismatch category, and tacrolimus coefficient of variation were independent correlates of TCMR. The correlation of HLA‐DR/DQ molecular mismatch category with TCMR, including Borderline, provides evidence for their alloimmune basis. HLA‐DR/DQ molecular mismatch may represent a precise prognostic biomarker that can be applied to tailor immunosuppression or design clinical trials based on individual patient risk.

Kidney allograft fibrosis: what we learned from latest translational research studies.

To add new molecular and pathogenetic insights into the biological machinery associated to kidney allograft fibrosis is a major research target in nephrology and organ transplant translational medicine. Interstitial fibrosis associated to tubular atrophy (IF/TA) is, in fact, an inevitable and progressive process that occurs in almost every type of chronic allograft injury (particularly in grafts from expanded criteria donors) characterized by profound remodeling and excessive production/deposition of fibrillar extracellular matrix (ECM) with a great clinical impact. IF/TA is detectable in more than 50% of kidney allografts at 2 years. However, although well studied, the complete cellular/biological network associated with IF/TA is only partially evaluated. In the last few years, then, thanks to the introduction of new biomolecular technologies, inflammation in scarred/fibrotic parenchyma areas (recently acknowledged by the BANFF classification) has been recognized as a pivotal element able to accelerate the onset and development of the allograft chronic damage. Therefore, in this review, we focused on some new pathogenetic elements involved in graft fibrosis (including epithelial/endothelial to mesenchymal transition, oxidative stress, activation of Wnt and Hedgehog signaling pathways, fatty acids oxidation and cellular senescence) that, in our opinion, could become in future good candidates as potential biomarkers and therapeutic targets.

Single Nucleotide Polymorphisms of Ubiquitin-Related Genes were Associated with Allograft Fibrosis of Renal Transplant Fibrosis.

BackgroundInterstitial fibrosis and tubular atrophy (IF/TA) have been recognized as crucial factors contributing to graft loss resulting from chronic renal allograft injuries. Recent studies have indicated a significant association between the progression of organ fibrosis and single nucleotide polymorphisms (SNPs) found on certain genes. Our research sought to understand these potential associations and detect the potential impact of SNPs on ubiquitin-related genes related to allograft fibrosis in kidney transplant recipients.Material/MethodsThere were 200 patients enrolled in this study, from which samples were extracted for total DNA. Targeted next-generation sequencing was used to detect SNPs on 9 genes (FBXL21, PIAS1/2, SUMO1/2/3/4, UBE2D1, and UBE2I). Minor allele frequency (MAF) and Hardy-Weinberg equilibrium (HWE) tests were used and followed by linkage disequilibrium analysis. General linear models (GLM) were used to identify significant confounding factors. Finally, multiple inheritance models and haplotype analyses were conducted to explore associations between SNPs and the degree of the severity of renal allograft fibrosis.ResultsIn total, 144 SNPs were identified in targeted sequencing. After filtering based on results from MAF and HWE tests, 15 tagger SNPs were selected for further analyses of associations. GLMs indicated that the administration of sirolimus significantly contributed to the degree of severity of allograft fibrosis (P=0.011). After adjusting for confounding factors and applying a Bonferroni correction, multiple inheritance model analyses indicated that the recessive model of rs644731 of the PIAS2 gene was significantly correlated with the occurrence of IF/TA (P=0.01). Furthermore, single-locus based analysis of rs644731 did not indicate that it had a positive influence on IF/TA in a degree-dependent manner. Finally, linkage disequilibrium analysis revealed 3 haplotypes all lacking significant correlation with respect to the IF/TA experimental cohort.ConclusionsWe are the first to reveal that mutations of rs644731 in the PIAS2 gene were significantly correlated with the progression of IF/TA in kidney transplant recipients.

Autotaxin Inhibitor Protects from Chronic Allograft Injury in Rat Kidney Allotransplantation

Background: Tissue fibrosis is the final common phase of chronic allograft injury, the leading cause of late graft loss in kidney transplantation. Preclinical evidence points to the involvement of lysophosphatidic acid (LPA), a bioactive phospholipid, in the development of renal fibrosis. Objectives: We assessed whether treatment with an orally available inhibitor of autotaxin (ATXi), the main LPA-producing enzyme, could slow the progression of chronic allograft injury in a fully major histocompatibility complex-mismatched rat kidney transplant model and compared its effects with those of the angiotensin-converting enzyme inhibitor lisinopril. Methods: Kidney allograft recipients were given ciclosporin for the first 15 postoperative days to prevent early acute rejection. Thereafter, they received either no treatment or ATXi or lisinopril and were followed for 180 days after transplantation. Results: Renal LPA levels were increased in allograft rats, providing the rationale for using ATXi in this model. Chronic treatment with ATXi or lisinopril limited progressive proteinuria and ameliorated tubulointerstitial fibrosis compared with allograft rats, although the effects were more robust under ATX inhibition. The administration of ATXi, but not lisinopril, attenuated systemic hypertension, reduced intragraft T cell infiltration, and eventually improved renal graft survival. Conclusions: In summary, ATXi had protective effects on indices of chronic allograft injury and could be of therapeutic add-on value in the kidney transplant setting. Notably, an ATX inhibitor is currently being investigated in 2 large phase 3 studies in idiopathic pulmonary fibrosis, underscoring the clinical relevance of our findings.

Cytomegalovirus prevention strategies and the risk of BK polyomavirus viremia and nephropathy.

Polyomavirus BK (BKV) is the cause of polyomavirus-associated nephropathy resulting in premature graft loss. There are limited data regarding the role of cytomegalovirus (CMV) infection and its prevention in developing BKV viremia and PVAN. In a prospective study, we analyzed 207 consecutive renal transplant recipients previously enrolled in 2 randomized trials evaluating different CMV prevention regimens with routine screening for BKV and CMV. Of these, 59 received valganciclovir and 100 valacyclovir prophylaxis; 48 patients were managed by preemptive therapy. At 3years, the incidence of BKV viremia and PVAN was 28% and 5%, respectively. CMV DNAemia developed in 55% and CMV disease in 6%. Both BKV viremia (42% vs 23% vs 21%, P=.006) and PVAN (12% vs 2% vs 2%, P=.011) were increased in patients treated with valganciclovir prophylaxis compared to valacyclovir and preemptive therapy. Using multivariate Cox proportional hazard regression, valganciclovir prophylaxis was independent predictor of BKV viremia (hazard ratio [HR]=2.38, P=.002) and PVAN (HR=4.73, P=.026). In contrast, the risk of subsequent BKV viremia was lower in patients with antecedent CMV DNAemia (HR=0.50, P=.018). These data suggest valganciclovir prophylaxis may be associated with increased risk of BKV viremia and PVAN. CMV DNAemia did not represent a risk for BKV.