Intimal Arteritis and Microvascular Inflammation Are Associated With Inferior Kidney Graft Outcome, Regardless of Donor-Specific Antibodies

Background: The prognostic role of intimal arteritis of kidney allografts in donor-specific antibody negative (DSA–) antibody-mediated rejection (ABMR) remains unclear.Methods: Seventy-two out of 881 patients who had undergone kidney transplantation from 2014 to 2017 exhibited intimal arteritis in biopsies performed during the first 12 months. In 26 DSA negative cases, the intimal arteritis was accompanied by tubulointerstitial inflammation as part of T cell-mediated vascular rejection (TCMRV, N = 26); intimal arteritis along with microvascular inflammation occurred in 29 DSA negative (ABMRV/DSA–) and 19 DSA positive cases (ABMRV, DSA+, N = 17). In 60 (83%) patients with intimal arteritis, the surveillance biopsies after antirejection therapy were performed. Hundred and two patients with non-vascular ABMR with DSA (ABMR/DSA+, N = 55) and without DSA (ABMR/DSA–, N = 47) served as controls. Time to transplant glomerulopathy (TG) and graft failure were the study endpoints.Results: Transplant glomerulopathy -free survival at 36 months was 100% in TCMRV, 85% in ABMR/DSA–, 65% in ABMRV/DSA-, 54% in ABMR/DSA+ and 31% in ABMRV/DSA+ (log rank p < 0.001). Death-censored graft survival at 36 months was 98% in ABMR/DSA-, 96% in TCMRV, 86% in ABMRV/DSA–, 79% in ABMR/DSA+, and 64% in ABMRV/DSA+ group (log rank p = 0.001). In surveillance biopsies, the resolution of rejection was found in 19 (90%) TCMRV, 14 (58%) ABMRV/DSA–, and only 4 (27%) ABMRV/DSA+ patients (p = 0.006). In the multivariable model, intimal arteritis as part of ABMR represented a significant risk for TG development (HR 2.1, 95% CI 1.2–3.8; p = 0.012) regardless of DSA status but not for graft failure at 36 months.Conclusions: Intimal arteritis as part of ABMR represented a risk for early development of TG regardless of the presence or absence of DSA. Intimal arteritis in DSA positive ABMR represented the high-risk phenotype.

Impact of Tacrolimus Daily Dose Limitation in Renal Transplant Recipients Expressing CYP3A5: A Retrospective Study

The pharmacokinetic variability of tacrolimus can be partly explained by CYP3A5 activity. Our objective was to evaluate a tacrolimus sparing policy on renal graft outcome according to CYP3A5 6986A>G genetic polymorphism. This retrospective study included 1114 recipients with a median follow-up of 6.3 years. Genotyping of the 6986A>G allelic variant corresponding to CYP3A5*3 was systematically performed. One year after transplantation, tacrolimus blood trough concentration (C0) target range was 5–7 ng/mL. However, daily dose was capped to 0.10 mg/kg/day regardless of the CYP3A5 genotype. A total 208 CYP3A5*1/- patients were included. Despite a higher daily dose, CYP3A5*1/- recipients exhibited lower C0 during follow-up (p < 0.01). Multivariate analysis did not show any significant influence of CYP3A5*1/- genotype (HR = 0.70, 0.46–1.07, p = 0.10) on patient-graft survival. Glomerular Filtration Rate (GFR) decline was significantly lower for the CYP3A5*1/- group (p = 0.02). The CYP3A5*1/- genotype did not significantly impact the risk of biopsy-proven acute rejection (BPAR) (HR = 1.01, 0.68–1.49, p = 0.97) despite significantly lower C0. Based on our experience, a strategy of tacrolimus capping is associated with a better GFR evolution in CYP3A5*1/- recipients without any significant increase of BPAR incidence. Our study raised some issues about specific therapeutic tacrolimus C0 targets for CYP3A5*1/- patients and suggests to set up randomized control studies in this specific population.

Perfusate metabolomics content and tubular transporters expression during kidney graft preservation by hypothermic machine perfusion

BackgroundIschemia-related injury during the pre-implantation period impacts kidney graft outcome. Evaluating these lesions by a non-invasive approach before transplantation could help to understand the mechanisms of graft injury and identify potential biomarkers predictive of graft outcomes. This study aims to determine metabolomic content of graft perfusion fluids and its dependence on preservation time and to explore whether tubular transporters are possibly involved in the metabolomics variations observed.MethodsKidneys were stored on hypothermic perfusion machines. We evaluated the metabolomic profiles of perfusion fluids (n=35) using Liquid Chromatography coupled with tandem Mass Spectrometry and studied the transcriptional expression of tubular transporters on pre-implantation biopsies (n=26). We used univariate and multivariate analyses to assess the impact of perfusion time on these parameters and their relationship with graft outcome.ResultsSeventy-two metabolites were found in preservation fluids at the end of perfusion, of which 40% were already present in the native conservation solution. We observed an increase of 23 metabolites with longer perfusion time and a decrease for 8. The predictive model for time-dependent variation of metabolomics content showed good performance (R2= 76%, Q2= 54%, accuracy= 41%, permutations test significant). Perfusion time had no effect on the mRNA expression of transporters. We found no correlation between metabolomics and transporters expression. Neither the metabolomics profile nor the transporters expression were predictive of graft outcome.ConclusionOur results open the way for further studies, focusing on both intra- and extra-tissue metabolome, to investigate whether transporter alterations can explain the variations observed in pre-implantation period.

Treatment of Allosensitized Patients Receiving Allogeneic Transplantation

Donor-specific anti-HLA antibodies (DSA) are a major cause of engraftment failure in patients receiving haploidentical stem cell transplantation (HaploSCT). Effective treatments are needed for these patients who often have no other donor options and/or are in need to proceed urgently to transplantation. We studied a multimodality treatment with alternate day plasma exchange, rituximab, intravenous gamma globulin (IvIg) and an irradiated donor buffy coat for patients with DSA at two institutions. Thirty-seven patients with a median age of 51 years were treated with this desensitization protocol. Treatment outcomes were compared with a control group of HaploSCT patients without DSA (N=345). Majority of patients in the DSA group were females (83.8% vs. 37.1% in controls, p&lt;0.001) and received stem cells from a child as donor (67.6% vs. 44.1%, p=0.002). Mean DSA level before and after desensitization was 10,198 and 5,937 MFI, respectively with mean differences of 4,030 MFI. Fourteen of 30 tested patients (46.7%) had C1q positivity while 8 of 29 tested patients (27.6%) remained positive after desensitization. In multivariable analysis, patients with initial DSA &gt;20,000 MFI and with persistent C1q+ after desensitization had a significantly lower engraftment rate, resulted in a significantly higher non-relapse mortality (NRM) and worse overall survival (OS) than controls whereas graft outcome and survivals of patients with initial DSA &lt;20,000 MFI and those with negative C1q after treatment were comparable with controls. In conclusion, treatment with plasma exchange, rituximab, IvIg and donor buffy coat is effective in promoting engraftment in patients with DSA up to 20,000 MFI.

Evaluation of antibodies directed against two GPCRs, anti-AT1R and anti-ETAR, on kidney transplant outcome: Own experience and review of the topic

Background: The role of an alloimmune response against non-self-antigens is established in organ transplantation. The main actors of this recognition are the HLA incompatibilities between donor and recipient, but may also involve reactivity against other alloantigens expressed on the allograft and result from an autoimmune response developed against self-antigens. Objective: Our study aimed to determine the presence of non-anti-HLA antibodies (anti-AT1R and anti-ETAR) in sera from patients with end-stage renal disease who underwent kidney transplantation in pre-and post-transplantation samples and study their influence on the development and evolution of acute humoral rejections and DSAs. Method: In this sense, antibodies (Abs) against two G protein-coupled receptors (GPCRs), angiotensin II type 1 receptor (AT1R) and endothelin-1 type A receptor (ETAR), have been detected in the sera of transplant recipients who experience allograft dysfunction, patients with coronary heart disease, marginal hypertension and refractory, vascular lesions, myocardial hypertrophy and chronic inflammatory diseases such as atherosclerosis or sclerosis. Results: In our own experience, kidney graft recipients were monitored for anti-ETAR, -AT1R, and -HLA Abs in pre-and post-transplant evolution, and anti-AT1R and/or -ETAR Abs were detected in 24% of recipients (22.4% with anti-AT1R Abs and 9.8% with anti-ETAR Abs). Due to acute humoral rejection, Graft loss was detected in 6.4% of patients with anti-GPCRs non-HLA Abs, and 3.2% had DSA anti-HLA Abs. In this research and review paper, we bring together our own experience, also how to function the anti-GPCRs autoAbs and how these Abs that activate GPCRs could influence graft outcome. Conclusion. Therefore, in conclusion, there is a high association of non-HLA anti-GPCRs Abs levels with reduced kidney function after transplantation, especially in the presence of DSA anti-HLA Abs. Although more studies are needed, anti-AT1R and anti-ETAR antibodies may be helpful biomarkers that allow the risk of graft loss to be assessed.

The MicroRNA Landscape of Acute Beta Cell Destruction in Type 1 Diabetic Recipients of Intraportal Islet Grafts

Ongoing beta cell death in type 1 diabetes (T1D) can be detected using biomarkers selectively discharged by dying beta cells into plasma. microRNA-375 (miR-375) ranks among the top biomarkers based on studies in animal models and human islet transplantation. Our objective was to identify additional microRNAs that are co-released with miR-375 proportionate to the amount of beta cell destruction. RT-PCR profiling of 733 microRNAs in a discovery cohort of T1D patients 1 h before/after islet transplantation indicated increased plasma levels of 22 microRNAs. Sub-selection for beta cell selectivity resulted in 15 microRNAs that were subjected to double-blinded multicenter analysis. This led to the identification of eight microRNAs that were consistently increased during early graft destruction: besides miR-375, these included miR-132/204/410/200a/429/125b, microRNAs with known function and enrichment in beta cells. Their potential clinical translation was investigated in a third independent cohort of 46 transplant patients by correlating post-transplant microRNA levels to C-peptide levels 2 months later. Only miR-375 and miR-132 had prognostic potential for graft outcome, and none of the newly identified microRNAs outperformed miR-375 in multiple regression. In conclusion, this study reveals multiple beta cell-enriched microRNAs that are co-released with miR-375 and can be used as complementary biomarkers of beta cell death.