A 2018 Reference Guide to the Banff Classification of Renal Allograft Pathology

Evaluating the efficacy of basiliximab versus no induction in low-immunological-risk kidney transplant recipients: a propensity score matched analysis

BACKGROUND

The optimal use of induction therapy in low-immunological-risk kidney transplant recipients (KTRs) remains uncertain. While Basiliximab (BSX) is widely utilized, its comparative outcomes with no induction therapy require further evaluation.

METHOD

This single-center retrospective cohort study included 182 low-immunological-risk KTRs who underwent transplantation between January 2022 and March 2023. Patients were assigned to either no induction (n = 41) or BSX induction (n = 141) groups. Propensity score matching (PSM) minimized selection bias and controlled for confounding factors. Primary outcomes included the incidence of first acute rejection (AR) within 12 months, while secondary outcomes encompassed graft function, infection rates, and adverse events.

RESULT

After 12 months, the cumulative AR incidence was comparable between groups (p = 0.46). The no induction group demonstrated superior renal function, with consistently higher estimated glomerular filtration rates (eGFR) at early postoperative intervals. Additionally, this group exhibited reduced infection-related hospitalizations (respiratory infections: 7.32 vs. 29.1%, p = 0.008) and hematological complications (thrombocytopenia: 0.00% vs. 12.8%, p = 0.014). Mortality and graft loss rates were similar between groups.

CONCLUSION

In low-immunological-risk KTRs, no induction therapy achieves comparable AR prevention and renal function outcomes to BSX while reducing infection and hematological complications. These findings challenge the necessity of universal induction therapy in this population and support a personalized approach to immunosuppression protocols.

A novel histologic index for polyomavirus nephropathy in comparison with the Banff scoring system: Clinical validation, prognostic implication, and correlation with plasma viral load

BK Polyomavirus nephropathy (PVN) with definitive diagnosis on biopsy, presents incidentally or with varying degrees of graft dysfunction. Banff working group on PVN has proposed a novel scoring system in renal biopsies, to identify patients with higher risk of graft failure. In this study, we attempted to validate the Banff scoring system at index biopsies and correlate with a novel index score, plasma BK-virus load and graft outcome. 48 patients with index biopsies of PVN diagnosed from 2019 to 2022, with simultaneous plasma BKV-virus loads and SV-40 stains were chosen. Biopsies were scored for Banff PVN Class and by novel PVN index. Inter-observer reproducibility was tested between 3 renal pathologists for all parameters and findings were correlated with graft outcome, in a median follow-up of 42 months. Banff PVN classes 2 and 3 and novel index 3 were associated with higher percentage of graft failure and persistent viremia. The novel index score showed a stronger and consistent temporal association with plasma BK-virus levels. Kappa scores revealed a 68 % agreement for Banff PVN class scoring. Our study highlights the prognostic utility of Banff PVN scheme and novel PVN index in correlation with plasma BKV viremia and graft outcome.

Follicular regulatory T cells restrain kidney allograft rejection in mice by suppressing alloreactive B cells

Pathogenic antibodies produced by alloreactive B cells mediate antibody-mediated rejection after kidney transplantation, but the mechanisms remain poorly understood. Follicular regulatory T (Tfr) cells modulate follicular helper T cell-mediated B cell responses, but the functions of Tfr in controlling alloreactive antibody are unknown. Here we study the developmental signals and functions of Tfr cells in mouse allogeneic kidney transplantation models, and show that costimulatory blockade alters the development of Tfr cells disproportionately by decreasing germinal center (GC)-like Tfr cells but increasing follicular-like Tfr cells. Functionally, global Tfr cell deletion results in accelerated graft rejection and increases in donor-specific B cells in both draining lymph nodes and kidney allografts. Mechanistically, Tfr cell deletion increases GC B cell expression of pro-inflammatory cytokines such as IL-15, while neutralization of IL-15 compensates for the loss of Tfr cells and prolongs the survival of mice receiving kidney transplants. Together our preclinical mouse data demonstrate how Tfr restrains kidney allograft rejection by limiting alloreactive B cell responses.

Additional Diagnoses Other Than Rejection in the Kidney Allograft Biopsy: Pitfalls for Biopsy-based Transcript Diagnostics

Background

Biopsy-based transcripts associated with antibody-mediated rejection (AMR) hold promise as substitutes for C4d positivity. However, their utility in cases with additional diagnoses other than rejection remains inadequately studied.

Methods

In our comprehensive analysis of 326 kidney allograft biopsies, assessed by histology and the Molecular Microscope Diagnostic System, we identified 68 cases characterized by additional pathologies, including pyelonephritis (n = 15), BK nephropathy (n = 20), acute interstitial nephritis (n = 5), and glomerular diseases (n = 28).

Results

Among cases with pyelonephritis, 7 of 15 cases (46%) showed a rejection-like signal, 4 above (16%) and 3 (20%) below diagnostic thresholds. Notably, the T cell-mediated rejection (TCMR) archetype score R2 (median, 0.13; interquartile range [IQR], 0.04-0.34) predominantly contributed to this observation. In BK nephropathy, 13 of 20 cases (65%) showed a rejection-like signal, 10 (50%) above and 3 (15%) below diagnostic thresholds. Elevated TCMR R2 (median, 0.07; IQR, 0.00-0.41) and all AMR archetype scores R4-6 (median, 0.23; IQR, 0.07-0.53) were driving factors. Among cases with acute interstitial nephritis, 3 of 5 cases (60%) showed TCMR-like signal with elevated R2 scores (median, 0.13; IQR, 0.00-0.54). Conversely, only 5 of 28 cases (18%) showed a rejection-like signal in glomerular disease cases, whereas 57% displayed all AMR archetype scores of ≥0.30.

Conclusions

Additional pathologies can affect the Molecular Microscope Diagnostic System output, giving a molecular rejection-like signal. The prevalence of rejection-like signals below diagnostic thresholds is noteworthy, warranting caution and prompting further investigation.

Impact of anti-HLA antibodies screening techniques on waiting time on the waiting list and kidney transplant outcomes

BACKGROUND

Differences in sensitivity and specificity between the techniques used for the detection of anti-HLA antibodies before kidney transplantation (KT) can lead to contradictory results that influence patients' management. Our aim is to analyse whether the technique used, based on complement-mediated-cytotoxicity (CDC) or on microsphere fluorimetry (xMAP), conditions the waiting time until transplantation and its results.

METHODS

We performed a retrospective cohort study of the KT performed in our centre from 2006 to 2018 whose pre-transplant anti-HLA specificity determination and definition of prohibited antigens was performed by CDC (2006-2011) or by xMAP (2012-2018). Living donor KT recipients were excluded. The influence of each technique on the time on the waiting list and on the outcome of kidney transplantation was analysed, using as indicators the initial function of the graft, the rate of humoral rejection and graft survival.

RESULTS

During the period of the study, 622 patients were included (264 were studied by CDC and 358 by xMAP). Recipient and donor age was higher in the xMAP group (p < 0.001). Additionally, most sensitised patients were in the xMAP group (p < 0.001). However, they received a KT earlier. There were no differences in the rate of acute humoral rejection between groups. Nevertheless, graft survival was better in the xMAP group.

CONCLUSIONS

The introduction of the xMAP technique in our centre has meant an improvement in terms of accessibility to transplantation and the initial management of the patient. However, it does not ameliorate the indicators of graft rejection.

Limitations of biopsy-based transcript diagnostics to detect T-cell-mediated allograft rejection

BACKGROUND

Isolated tubulitis, borderline changes and isolated arteritis suspicious for histologic T-cell-mediated rejection (hTCMR) remain findings of uncertain significance. Although the Molecular Microscope Diagnostics System (MMDx) has not been trained on those lesions, it was suggested that MMDx might reclassify a subgroup to molecular TCMR (mTCMR).

METHODS

In this single-center cohort of 326 consecutive, unselected kidney allograft biopsies assessed by histology and MMDx, we analyzed 249 cases with isolated tubulitis (i0, t1-3, v0; n = 101), borderline changes (according to Banff 2022, v0; n = 9), isolated arteritis (no borderline, v1; n = 37), no inflammation (i0, t0, v0; n = 67) and a positive control cohort (hTCMR, n = 27; mixed histologic rejection, n = 8; both according to Banff 2022; total n = 35). The first three groups were summarized as TCMR-suspicion (n = 147). Subcategorization included the presence and absence of microvascular inflammation (MVI); g+ptc ptc ≥2. Molecular rejection rates and differentiation were investigated.

RESULTS

Molecular rejection rates were 37/147 cases (25.2%; 32 with MVI) in TCMR-suspicion, 6/67 (9%; 4 with MVI) in no inflammation and 30/35 (85.7%; 19 with MVI) in the positive control cohort. Molecular antibody-mediated rejection (mAMR) was present in 39/73 (53.4%) of cases. The presence of donor-specific antibodies at the time of the biopsy was high (127/249, 51%). Only 3 mAMR/TCMR and 0 pure mTCMR cases were detected in TCMR-suspicion and no inflammation, compared with 12 mAMR/TCMR and 10 mTCMR cases in the positive control cohort (P < .001). Even though the TCMR-specific molecular (Classifier) score differentiated between TCMR-suspicion and no inflammation (P = 0.005), rejection phenotype scores (R2 and R3) did not (P = .157 and .121).

CONCLUSIONS

MMDx did not identify pure mTCMR among isolated tubulitis, borderline changes or isolated arteritis, likely due to low sensitivity for TCMR lesions. However, it identified mAMR or mAMR/TCMR, especially in cases with MVI. Subthreshold findings remain to be further studied.

Impact of Immunosuppressive Drug Concentrations on Microvascular Inflammation, Negative Donor-Specific Antibodies, and C4d-Negative Status in Kidney Transplant Recipients

INTRODUCTION

This study investigated the impact of immunosuppressive drug concentrations on microvascular inflammation (MVI) in kidney transplant recipients with negative donor-specific antibodies (DSA) against human leukocyte antigen (HLA) and negative C4d deposition in peritubular capillaries.

METHODS

We analyzed data from 268 living kidney transplant recipients at the Department of Urology, University of Osaka, Japan. Patients received immunosuppressive therapy comprising extended-release tacrolimus, mycophenolate mofetil (MMF), and/or everolimus, with or without steroids. Graft biopsies were routinely performed at 3, 12, 36 and 60 months post-surgery.

RESULTS

No significant differences were observed between the MVI+DSA-C4d- and MVI-DSAC4d groups regarding graft survival rates (95.5% vs. 96.6%, p = 0.772) or patient survival rates (95.7% vs. 95.9%, p = 0.735). Lower tacrolimus and everolimus concentrations were significantly associated with an increased risk of MVI+DSA-C4d- (tacrolimus: OR, 0.169; 95% CI, 0.055-0.515; p = 0.002; everolimus: OR, 0.386; 95% CI, 0.171-0.874; p = 0.022). In contrast, MPA concentration was not significantly associated with MVI+DSA-C4d- (OR, 0.994; 95% CI, 0.554-1.780; p = 0.984). Steroid discontinuation did not significantly impact the risk of MVI+DSA-C4d- (OR, 1.980; 95% CI, 0.318-12.000; p = 0.470).

CONCLUSION

Lower trough levels of tacrolimus and everolimus correlated with a higher incidence of antibody-independent MVI, supporting the need for tailored immunosuppressive regimens in kidney transplantation.

Immune responses in rodent whole eye transplantation: elucidation and preliminary investigations into rejection diagnosis and monitoring

Background

Whole Eye Transplantation (WET) offers potential for vision restoration but is hindered by the complex challenge of immune rejection. Understanding and closely monitoring these immunological responses is crucial for advancing WET. This study delves into the timeline and nature of immune responses in a rodent model of WET without immunosuppression, aiming to elucidate a detailed picture of the immune landscape post-transplantation and establish innovative diagnostic and monitoring methods.

Methods

We employed a multi-faceted approach to analyze immune responses post-WET, including assessments of gross changes in corneal transparency, thickness, and skin condition. Histopathological examinations of both ocular and surrounding skin tissues provided insights into cellular changes, complemented by ocular RT-qPCR for molecular analysis. Serological analysis was employed to quantify cytokines, chemokines, and donor-specific antibodies, aiming to identify potential biomarkers correlating with WET rejection and to validate the presence of antibody-mediated rejection. These methodologies collectively contribute to the development of non-invasive diagnostic and monitoring strategies for WET.

Results

Our study revealed a rapid and acute immune response following WET, characterized by an early innate immune response dominated by complement involvement, and infiltration of neutrophils and monocytes by post-operative day (POD) 2. This was succeeded by an acute T-cell-mediated immune reaction, predominantly involving T helper 1 (Th1) cells and cytotoxic T lymphocytes (CTLs). The presence of donor specific antibody (DSA) and indications of pyroptosis in the early phases of rejection were observed. Notably, the early elevation of serum CXCL10 by POD4, coupled with ocular CD3+ cell infiltration, emerged as a potential early biomarker for WET rejection. Additionally, corneal transparency grading proved effective as a non-invasive monitoring tool.

Conclusion

This study offers a first-time comprehensive exploration of immune responses in WET, unveiling rapid and complex rejection mechanisms. The identification of early biomarkers and the development of non-invasive monitoring techniques significantly advance our understanding of WET rejection. Additionally, these findings establish an essential baseline for future research in this evolving field.

Acute kidney injury in paediatric kidney transplant recipients

Acute kidney injury (AKI) in paediatric kidney transplant recipients is common. Infection including urinary tract infection (UTI) and rejection are the most common causes in children. Surgical complications often cause AKI early post-transplant, whereas BK polyomavirus nephropathy rarely occurs in the first month post-transplant. Understanding kidney physiology helps to appreciate the sensitivity of the allograft to AKI, more so than native kidneys. Although the cause of AKI is often multi-factorial, there may be an underlying process that is treatable. Eliciting the aetiology, in this regard, is of paramount importance. Pre-renal and post-renal causes of allograft dysfunction are important to distinguish from intrinsic kidney disease. Clinical information and examination of fluid balance, urine dipstick testing, blood tests, bladder and kidney transplant ultrasound, and kidney transplant biopsy remain vital assessment tools in narrowing the differential diagnosis. A careful prescribed and recreational drug history is always warranted as many drugs including supplements are nephrotoxic. Additional causes such as allograft rejection, recurrent disease, and calcineurin inhibitor toxicity need to be considered in cases of allograft dysfunction, which would not affect the native kidneys. Early detection and assessment of AKI is crucial in promoting recovery. Significant progress has been made in specific pathologies over the last 20 years, which has improved kidney allograft survival rates considerably. Research into identifying AKI biomarkers to assist early diagnosis, before the serum creatinine rises, is ongoing.

Stem cells prevent long-term deterioration of renal function after renal artery revascularization in a renovascular hypertension model in rats

Partial stenosis of the renal artery causes renovascular hypertension (RVH) and is accompanied by chronic renal ischemia, resulting in irreversible kidney damage. Revascularization constitutes the most efficient therapy for normalizing blood pressure (BP) and has significant benefits for renal function; however, the tissue damage caused by chronic hypoxia is not fully reversed. Mesenchymal stem cells (MSCs) have produced discrete results in minimizing RVH and renal tissue and functional improvements since the obstruction persists. This study aimed to evaluate the effects of administration of MSCs in combination with renal artery revascularization in rats subjected to RVH. The following groups were evaluated: control (SHAM), hypertensive (2K-1C), hypertensive treated with MSCs (MSC), hypertensive subjected to revascularization (REV), and hypertensive subjected to revascularization and treatment with MSCs (REV + MSC). The animals were followed up for 10 weeks. The animals in the MSC group received cell infusions at the 3rd, 5th, 7th and 9th weeks. In the REV and REV + MSC groups, the clip was removed by the 6th week (revascularization), and in the REV + MSC group, MSCs infusion was performed at the 6th and 8th weeks. Tail systolic blood pressure (SBP) was measured weekly, and histological parameters and renal function were evaluated at the end of the protocol. The clipped animals developed RVH, deterioration of total renal function (50% decrease in creatinine clearance), and significant proteinuria (15x increase). Treatment with MSCs had no detectable beneficial effects on kidney function or SBP. REV resulted in normalization of BP and a significant but partial reduction in proteinuria (80% vs. 2K-1C), but areas with renal fibrosis persisted. The combination of the two treatments was effective at normalizing all renal parameters as well as reversing proteinuria, reducing the number of ischemic glomeruli and atrophic tubules, indicating an improvement of the renal parenchyma. The results suggest that therapy with MSCs associated with revascularization can potentially help in the full recovery of renal function in the long term in patients with RVH.

Open-label randomised clinical trial investigating whether robot-assisted kidney transplantation can reduce surgical complications compared to open kidney transplantation (ORAKTx): study protocol for a randomised clinical trial

BACKGROUND

Kidney transplantation is the ultimate treatment for end-stage kidney disease. Function of the kidney graft is not only dependent on medical factors but also on a complication-free surgical procedure. In the event of major surgical complications, the kidney graft is potentially lost and the patient will return to the waiting list which may be long. To optimise peri-operative care and reduce complications, robot-assisted kidney transplantation (RAKT) has been introduced as an alternative to open kidney transplantation (OKT), but to our knowledge, no randomised clinical trials (RCT) have compared RAKT to OKT. In this study, we will explore whether robot-assisted surgery can reduce 30-day surgical complications compared to open surgery in kidney transplantation.

METHODS

This is a single-site, open-label, randomised clinical trial comparing RAKT to OKT. Participants are adult recipients of kidney transplantation recruited from Copenhagen University Hospital - Rigshospitalet, Denmark. The study plans to include 106 participants who will be randomised in a 1:1 manner between OKT and RAKT. Primary outcomes are vascular- and major surgical complications at 30 days post-operatively. Participants will be followed for 2 years to evaluate secondary outcomes including recovery, late complications and kidney graft function. This is designed as a superiority trial and planned analyses will follow intention-to-treat principles.

DISCUSSION

Studies indicate RAKT can reduce several surgical complications, but the lack of RCTs limits the extrapolation of these results to justify replacing an open approach with a robot-assisted one. Ultimately, the introduction of new surgical techniques should be as vigorously tested as any other new treatments. However, reducing surgical complications that compromise graft viability could lead to improved patient care and survival.

TRIAL REGISTRATION

The trial was prospectively registered with ClinicalTrials.gov on February 15th, 2023, with the identifier NCT05730257.

Expanding the Scope of Microvascular Inflammation: Unveiling Its Presence Beyond Antibody-Mediated Rejection Into T-Cell Mediated Contexts

Microvascular inflammation (MVI) in kidney transplant biopsies is mainly associated with antibody-mediated rejection (AMR), sparking debate within the Banff Classification of Renal Allograft Pathology regarding its exclusivity. This study reviewed the literature on MVI in T cell-mediated rejection (TCMR) and analyzed MVI in our transplant population. We searched English publications in MEDLINE, Embase, Web of Science, Cochrane, and Google Scholar until June 2024, focusing on glomerulitis (g), peritubular capillaritis (ptc), or MVI in kidney transplant biopsies classified as TCMR. Additionally, we examined g, ptc, and MVI in 69 patients with AMR, TCMR, and no rejection. Our search yielded 541 citations, with 10 studies included, covering 810 TCMR and 156 AMR biopsies. The studies showed g, ptc, and MVI were present in TCMR but were less prevalent and severe than in AMR. In our cohort, AMR had significantly higher g, ptc, and MVI scores compared to aTCMR and ATN, however, aTCMR also displayed MVI. These findings confirm that MVI occurs in aTCMR and should not be exclusively linked to AMR. These findings highlight the need to further explore MVI's significance in TCMR and investigate the inflammatory composition. This could refine the Banff Classification, improving Classification accuracy of kidney transplant pathology assessments.

Introducing robot-assisted kidney transplantation in a high-volume centre in Denmark: a pilot and feasibility study

Robot-assisted kidney transplantation (RAKT) may reduce surgical complications compared to open kidney transplantation (OKT), but no randomised trials have explored this to date. The aim of the present study is to explore the feasibility of introducing RAKT at our institution, making it available in deceased donor transplantation and evaluate early surgical outcomes prior to performing a randomised trial comparing RAKT to OKT. RAKT was performed at Department of Urology, Copenhagen University Hospital, Rigshospitalet, Denmark. The patients were included from June 2022 until May 2023. The data were collected through the national electronic health records. The data include recipient, donor and intraoperative characteristics, postoperative complications within 90 days graded according to Clavien-Dindo classification and days alive and out of hospital (DAOH). The functional outcomes include eGFR, plasma creatinine, delayed graft function, and rejection episodes. Sixteen RAKTs were performed. Fourteen cases were transplantations with living donors and two cases were with deceased donors. There were no major intra-operative adverse events and no conversions. The median operative time was 223 min and median blood loss 150 ml. The median length of stay was 7 days and median DAOH was 82. Seven complications occurred in five patients at 90 days postoperatively; however, there were no major surgical complications. This study comprehensively assesses patient morbidity following RAKT in a small cohort with results indicating favourable outcomes. This supported our clinical assumption of reduced complications for a randomised trial comparing OKT and RAKT (the ORAKTx trial) which has been initiated (NCT identifier 05730257).

M1 and M2 Macrophage Polarization Correlates with Activity and Chronicity Indices in Lupus Nephritis

Background: Lupus nephritis (LN) is a severe manifestation of systemic lupus erythematosus (SLE), characterized by inflammation and immune dysregulation in the kidneys. The role of macrophage polarization in LN progression remains underexplored. Objective: This study examined the association between tubulointerstitial M1/M2 macrophage subpopulations and LN indices of activity and chronicity. Materials and Methods: We retrospectively reviewed 160 renal biopsy specimens in patients with LN (ISN/RPS classes II-V) from the database of the Department of Anatomical Pathology, the Faculty of Medicine Vajira Hospital, Navamindradhiraj University (2012-2021). Additional immunohistochemical analysis included CD68, iNOS, CD206, CD163, and evaluation of infiltration with M1 (iNOS+), M2a (CD206+), and M2c macrophages (CD163+). Moreover, clinical information at the time of the renal biopsy, including age, sex, and laboratory findings, was obtained from the electronic medical records. The data were correlated with the macrophage infiltration using the Spearman test. Results: Lupus nephritis biopsies with ISN/RPS class II-V were included (class II: 3 cases (2%), III: 30 cases (19%), III + V: 16 cases (10%), IV: 73 cases (46%), IV + V: 18 cases (11%), and V: 20 cases (12%)). In addition, the mean age of SLE patients at the time of biopsy was 33 years (range: 19-47 years). Most patients were females (n = 141; 88%). The population of CD68+ macrophages was related to serum creatinine (p < 0.001; rs = 0.34). We detected predominantly M2 macrophages across all LN classes, but M1 macrophages demonstrated significant correlations with the activity index (p < 0.001; rs = 0.43). Conversely, M2a and M2c subpopulations were strongly associated with the chronicity index (M2a: p < 0.001, rs = 0.48; M2c: p = 0.024, rs = 0.18). Total macrophages correlated with both indices (activity: p < 0.001, rs = 0.44; chronicity: p < 0.001, rs = 0.42). Conclusions: In lupus nephritis, the predominant population of macrophages is M2. Correlations were noted between the subpopulations of M1 and M2c macrophages and the activity and chronicity indices, respectively. In addition, macrophage populations correlated with disease progression, but the significance of this association in disease progression remains uncertain.

Only IF/TA in the Histological Evaluation of Post-Reperfusion Baseline Biopsies Correlates With Kidney Transplant Outcome

Here, we retrospectively evaluated the informational yield of 338 post-reperfusion kidney transplant biopsies (including 95 living donations) assessed according to BANFF for the histological characteristics interstitial fibrosis and tubular atrophy (IF/TA), glomerulosclerosis, arteriosclerosis, and acute tubular injury (ATI). Associations with delayed graft function (DGF) and death-censored graft survival were explored through Cox-regression analyses. The maximum follow-up time was 11.4 years, with DGF observed in 108 (32%) cases. After deceased donation there was no association between DGF and histologic parameters. Univariable Cox-regression unveiled an association of IF/TA and glomerulosclerosis with long-term death-censored graft survival (HR per 10% increase: IF/TA 1.63; 95% CI 1.17-2.28; p = 0.003; glomerulosclerosis 1.19; 95% CI 1.01-1.39; p = 0.031). In multivariable Cox regression analyses, adjusted for recognized clinical risk variables like expanded criteria donor-status, donor age, history of diabetes, and HLA-mismatches, only IF/TA maintained association over the total observation period in deceased donations and in the total cohort. Arteriosclerosis and ATI were not associated with clinical outcome after deceased donation. Especially ATI did not affect delayed graft function if only deceased donations were considered. Our data underlines the role of organ quality for transplant outcome prior to acute lesions such as ATI during the transplantation process.

CD154 blockade effectively controls antibody-mediated rejection in highly sensitized nonhuman primate kidney transplant recipients

Current desensitization and maintenance immunosuppression regimens for kidney transplantation in sensitized individuals show limited ability to control the posttransplant humoral response, resulting in high rates of antibody-mediated rejection (ABMR) and graft failure. Here, we showed that anti-CD154 monoclonal antibody (mAb)-based immunosuppression more effectively controlled allograft rejection and humoral rebound in a highly sensitized nonhuman primate kidney transplantation model compared with tacrolimus-based standard-of-care (SOC) immunosuppression. Desensitization with an anti-CD154 mAb (5C8) and a proteasome inhibitor led to decreased donor-specific antibodies (DSAs) and disruption of lymph node germinal centers with reduction of proliferating, memory, and class-switched B cells as well as T follicular helper cells. After transplant, the nonhuman primates maintained on 5C8-based immunosuppression had significantly better survival compared with those maintained on SOC immunosuppression (135.2 days versus 32.8 days, P = 0.013). The 5C8-treated group demonstrated better suppression of DSAs after transplant, more robust suppression of B cell populations, and better induction of regulatory T cells. Fewer infectious and welfare complications, including viral reactivation and weight loss, were also observed with 5C8-based immunosuppression compared with SOC immunosuppression. Therefore, anti-CD154 mAbs may improve kidney transplant outcomes through better control of posttransplant immune responses. The superior efficacy of anti-CD154 mAb-based immunosuppression over tacrolimus-based SOC seen in this highly sensitized NHP transplant model suggests that anti-CD154 mAbs could potentially be used to desensitize and treat highly sensitized patients receiving kidney transplantation.

Radiologic evaluation of the kidney transplant donor and recipient

The kidney is the most common solid organ transplant globally and rates continue to climb, driven by the increasing prevalence of end stage renal disease (ESRD). Compounded by advancements in surgical techniques and immunosuppression leading to longer graft survival, radiologists evermore commonly evaluate kidney transplant patients and candidates, underscoring their role along the transplant process. Multiphase computed tomography (CT) with multiplanar and 3D reformatting is the primary method for evaluating renal donor candidates, detailing renal size, vascular/collecting system anatomy, and identifying significant pathologies such as renal vascular diseases and nephrolithiasis. Ultrasound is the preferred initial postoperative imaging modality for graft evaluation due to its low cost, accessibility, noninvasiveness, and lack of radiation. CT and magnetic resonance imaging (MRI) may be useful adjunctive imaging techniques in diagnosing transplant pathology when ultrasound alone is not diagnostic. Kidney transplant complications are categorized by an approximate timeline framework, aiding in differential diagnosis based on onset, duration, and severity and include perinephric fluid collections, graft compression, iatrogenic injuries, vascular compromise, graft rejection, and neoplastic processes. This review discusses imaging strategies and important findings along the transplant timeline, from donor assessment to long-term recipient complications.

Probable antibody-mediated rejection in kidney transplantation is a rare and challenging phenotype to define: Findings from a single-center study

The Banff 2022 consensus introduced probable antibody-mediated rejection (AMR), characterized by mild AMR histologic features and human leukocyte antigen (HLA) donor-specific antibody (DSA) positivity. In a single-center observational cohort study of 1891 kidney transplant recipients transplanted between 2004 and 2021, 566 kidney biopsies were performed in 178 individual HLA-DSA-positive transplants. Evaluated at time of the first HLA-DSA-positive biopsy of each transplant (N = 178), 84 of the 178 (47.2%) of first biopsies were scored as no AMR, 22 of the 178 (12.4%) as probable AMR, and 72 of the 178 (40.4%) as AMR. The majority (77.3%) of probable AMR cases were first diagnosed in indication biopsies. Probable AMR was associated with lower estimated glomerular filtration rate (mL/min/1.73m2) than no AMR (20.2 [8.3-32.3] vs 40.1 [25.4-53.3]; P = .001). The one-year risk of (repeat) AMR was similar for probable AMR and AMR (subdistribution hazard ratio (sHR), 0.99; 0.42-2.31; P = .97) and higher than after no AMR (sHR, 3.05; 1.07-8.73; P = .04). Probable AMR had a higher five-year risk of transplant glomerulopathy vs no AMR (sHR, 4.29; 0.92-19.98; P = 06), similar to AMR (sHR, 1.74; 0.43-7.04; P = .44). No significant differences in five-year risk of graft failure emerged between probable AMR and AMR (sHR, 1.14; 0.36-3.58; P = .82) or no AMR (sHR, 2.46; 0.78-7.74; P = .12). Probable AMR is a rare phenotype, however, sharing significant similarities with AMR in this single-center study. Future studies are needed to validate reproducible diagnostic criteria and associated clinical outcomes to allow for defining best management of this potentially relevant phenotype.

Outcomes of kidney transplantation in patients with lysinuric protein intolerance

Background

Lysinuric protein intolerance (LPI) is a metabolic disorder that leads to dysfunctional intestinal absorption and kidney clearance of cationic amino acids. Chronic kidney disease develops in many LPI patients and leads to end-stage kidney disease in at least 10% of patients. Since data on kidney transplants in LPI patients are limited, we analysed the outcomes of LPI patients after transplantation in Finland.

Methods

This retrospective cohort study includes all Finnish LPI patients who have received a kidney transplant. The data were collected from the Finnish Transplant Registry and electronic medical records from 2005 through May 2023 or patient death. The plasma amino acid profile was analysed before and after transplantation.

Results

Eight LPI patients (75% female, mean age at transplant 41.9 years) received a kidney allograft and two of the patients received a second transplant. Nine transplants were from deceased donors and one was from a living donor. Acute rejection occurred after four transplantations (two T-cell mediated and two antibody mediated). One patient died 6 months after transplantation due to alveolar proteinosis. Apart from lower citrulline and higher lysine concentrations, plasma amino acid levels showed no changes after transplantation. The 1-, 5- and 10-year graft survivals were 80%, 68.6% and 51.4%, and patient survivals were 88%, 86% and 50%, respectively.

Conclusions

Kidney transplantation is feasible in patients with LPI, although the acute rejection rate seems high and severe complications such as pulmonary alveolar proteinosis may occur. Transplantation led to changes in plasma citrulline and lysine concentrations.

The Interplay Between Human Leukocyte Antigen Antibody Profile and COVID-19 Vaccination in Waitlisted Renal Transplant Patients

CONTEXT.—

Mass COVID-19 vaccination is mandated in vulnerable populations in our renal transplant waitlist cohort. However, the anti-human leukocyte antigen (anti-HLA) profile after COVID-19 vaccination is controversial, and the side effects are yet to be discerned.

OBJECTIVE.—

To evaluate the status of HLA antibodies in waitlisted renal transplant patients before and 3 weeks after each vaccination and if comorbidities are associated with the HLA antibody profile.

DESIGN.—

A total of 59 waitlisted kidney transplant patients were included in this study. The anti-HLA antibodies were analyzed before and 6 months after their last COVID-19 vaccination. The mean fluorescence intensity change in the anti-HLA antibody levels was used to classify patients into 3 groups: high inducers, low inducers, and noninducers.

RESULTS.—

There were significant HLA antibody profile changes after COVID-19 vaccination, showing 21 antibodies generated against HLA class I antigens and 7 against HLA class II antigens to their baseline. Compared with the noninducers, the high and low inducers showed a higher prevalence of COVID-19 infection, COVID-19 vaccine type, and background hypertension history.

CONCLUSIONS.—

Our data suggest that COVID-19 vaccination propagates anti-HLA class I and II antibodies for waitlisted renal transplant patients. The clinical significance of these antibodies needs further study. Furthermore, comorbidities, such as history of COVID-19 infection and hypertension, supplemented this effect. Anti-HLA antibody monitoring may be warranted in COVID-19 vaccinated, waitlisted renal transplant patients with a history of COVID-19 infection and/or hypertension.

Bowman capsule rupture in children with myeloperoxidase-antineutrophil cytoplasmic antibody-associated glomerulonephritis predicts poor renal survival

BACKGROUND

Recent developments indicated that Bowman capsule rupture (BCR) is observed in antineutrophil cytoplasmic antibody (ANCA)-associated glomerulonephritis (AAGN). We aimed to explore the relationship between BCR and clinical manifestations, pathological changes, and prognosis in children with myeloperoxidase (MPO)-AAGN.

METHODS

A total of 56 children with MPO-AAGN were divided into BCR (+) and BCR (-) groups according to the status of Bowman's capsule.

RESULTS

After retrospective analysis of the data, 24 children (42.9%) were found to have BCR. The results showed that BCR positively correlated with intrarenal immune cell infiltrates, obsolescence and crescents in glomeruli, tubulointerstitial inflammation, tubulitis, and tubular atrophy negatively correlated with normal glomeruli and immunoglobulin G deposition in the kidney. The clinical features and kidney pathological changes were more severe in the BCR (+) group than BCR (-) group, and the renal survival rate was significantly poorer in the BCR (+) group than BCR (-) group (χ2 = 5.45, p = 0.02). Moreover, estimated glomerular filtration rate (≤15 mL/ min/1.73 m2), BCR and ANCA renal risk score (ARRS) were independent risk factors for the development of end-stage kidney disease (ESKD) in children with MPO-AAGN. After combining BCR with the Berden classification and ARRS, our data suggested that the Berden classification + BCR and ARRS + BCR showed better predictive values for ESKD than those of the Berden classification and ARRS, respectively.

CONCLUSION

BCR is an important pathological lesion that correlates with severe clinical manifestations, pathological changes, and poor prognosis in children with MPO-AAGN.

Tissue-based Gene Expression Diagnosis of Mild and Moderate T-cell-mediated Rejection to Guide Therapy in Kidney Transplants

BACKGROUND

Mild histologic lesions of tubulo-interstitial inflammation could represent a "response-to-wounding" rather than allorecognition. Tissue gene expression may complement histopathology for T-cell-mediated rejection (TCMR) diagnostics.

METHODS

We report on the incorporation of tissue gene expression testing using a Molecular Microscope Diagnostic System into the management of kidney transplant biopsies with suspected TCMR. Patients (N = 209) were divided into 3 groups based upon diagnosis and TCMR therapy (with high-dose steroids and/or anti-thymocyte globulin): Group 1: Untreated histologic TCMR with molecular quiescence (H+M-); Group 2: Treated histologic and molecular TCMR (H+M+); and Group 3: Controls, with no histologic or molecular (H-M-) rejection.

RESULTS

At biopsy, estimated glomerular filtration rate was worse (P = 0.006) in H+M+ (N = 35; 33 ± 22 mL/min/1.73 m2) and H+M- (N = 30; 40 ± 18 mL/min/1.73 m2) groups; compared with H-M- (N = 144; 47 ± 24 mL/min/1.73 m2) group. In H+M- biopsies, mean molecular acute kidney injury scores (0.33 versus 0.10; P = 0.03) were higher than in H-M-; while molecular TCMR was lower compared with H+M+ (0.04 versus 0.54; P < 0.001). At 12 m postbiopsy estimated glomerular filtration rate remained low (P < 0.001) in H+M+ (38 ± 22 mL/min/1.73 m2) but improved in untreated H+M- (44 ± 22 mL/min/1.73 m2) and H-M- (50 ± 23 mL/min/1.73 m2) groups. At a mean follow-up of 2.1 ± 1.2 y post-index biopsy, death-censored graft survival was lower in H+M+ (74%) than in H+M- (90%) and H-M- (92%; P = 0.001). H+M+ cases had numerically higher rejection on follow-up biopsy (20%) than H+M- (7%) (P = 0.12) and de novo donor-specific antibody formation (H+M+ 24%; H+M- 10%; P = 0.13).

CONCLUSIONS

In this large single-center study, biopsies with untreated histological TCMR and molecular quiescence had comparable clinical outcomes to cases with no rejection, whereas those with histologic and tissue gene expression confirmed TCMR had inferior outcomes.

Vascular injury in glomerulopathies: the role of the endothelium

In glomerulopathies, endothelial dysfunction and the presence of histological vascular lesions such as thrombotic microangiopathy, arteriolar hyalinosis, and arteriosclerosis are related to a severe clinical course and worse renal prognosis. The endothelial cell, which naturally has anti-inflammatory and anti-thrombotic regulatory mechanisms, is particularly susceptible to damage caused by various etiologies and can become dysfunctional due to direct/indirect injury or a deficiency of protective factors. In addition, endothelial regulation and protection involve participation of the complement system, factors related to angiogenesis, the renin-angiotensin system (RAS), endothelin, the glycocalyx, the coagulation cascade, interaction between these pathways, interactions between glomerular structures (the endothelium, mesangium, podocyte, and basement membrane) and interstitial structures (tubules, arterioles and small vessels). Dysregulation of those components is also associated with the progression of renal fibrosis, since endothelial cell damage promotes endothelial-to-mesenchymal transition. Although the potential mechanisms of vascular injury have been widely described in diabetic kidney disease, hypertensive nephrosclerosis, and hemolytic uremic syndrome, they require further elucidation in other glomerulopathies. A better understanding of the pathogenesis of vascular injury in patients with glomerular diseases could contribute to the development of specific treatments for such injury.

Effect of multiorgan abdominal ischemic preconditioning on experimental kidney transplantation

PURPOSE

To mitigate ischemia-reperfusion injury (IRI) triggered in solid organ transplant procedures, we aimed to evaluate the effects of multi-organ abdominal ischemic preconditioning (MAIP) in the context of renal IRI.

METHODS

An experimental kidney transplant model was conducted. Rats were divided into three groups: an intervention free basal group from which physiological data was collected; a control group (CT), which consisted of transplanted animals without MAIP; and a treated group, in which a MAIP protocol was implemented in the donor during the procurement of the left kidney, monitoring the recipient for 24 hours.

RESULTS

Urea, creatinine, and lactate dehydrogenase, as well as histopathological analysis (Banff: CT 1,66 ± 0,57 vs. basal 0, and MAIP 1), showed a clear trend in favor of MAIP group. Similar results were observed for tumor necrosis factor-α, interleukin-6 and CXCL10, as well as indicators of oxidative stress, with statistically significant levels for CXCL10 [0,295 ± 0,0074 arbitrary units (AU) CT and 0,0057 ± 0,0065 AU MAIP] and TBARS (2,93 ± 0,08 nmol/μg CT; and 2,49 ± 0,23 nmol/μg MAIP; p 0.05).

CONCLUSION

The findings indicated that the MAIP exerts a protective influence on the transplanted kidneys, functioning as an IRI-protective strategy and enhancing the parameters associated with renal graft functionality.

2-Step Scores with optional nephropathology for the prediction of adverse outcomes for brain-dead donor kidneys in Eurotransplant

BACKGROUND

The decision to accept or discard the increasingly rare and marginal brain-dead donor kidneys in Eurotransplant (ET) countries has to be made without solid evidence. Thus, we developed and validated flexible clinicopathological scores called 2-Step Scores for the prognosis of delayed graft function (DGF) and 1-year death-censored transplant loss (1y-tl) reflecting the current practice of six ET countries including Croatia and Belgium.

METHODS

The training set was n = 620 for DGF and n = 711 for 1y-tl, with validation sets n = 158 and n = 162, respectively. In Step 1, stepwise logistic regression models including only clinical predictors were used to estimate the risks. In Step 2, risk estimates were updated for statistically relevant intermediate risk percentiles with nephropathology.

RESULTS

Step 1 revealed an increased risk of DGF with increased cold ischaemia time (CIT), donor and recipient body mass index, dialysis vintage, number of HLA-DR mismatches or recipient cytomegalovirus immunoglobulin G positivity. On the training and validation set, c-statistics were 0.672 and 0.704, respectively. At a range between 18% and 36%, accuracy of DGF-prognostication improved with nephropathology including number of glomeruli and Banff cv (updated overall c-statistics of 0.696 and 0.701, respectively). Risk of 1y-tl increased in recipients with CIT, sum of HLA-A, -B, -DR mismatches, and donor age. On training and validation sets, c-statistics were 0.700 and 0.769, respectively. Accuracy of 1y-tl prediction improved (c-statistics = 0.706 and 0.765) with Banff ct. Overall, calibration was good on the training, but moderate on the validation set; discrimination was at least as good as established scores when applied to the validation set.

CONCLUSION

Our flexible 2-Step Scores with optional inclusion of time-consuming and often unavailable nephropathology should yield good results for clinical practice in ET, and may be superior to established scores. Our scores are adaptable to donation after cardiac death and perfusion pump use.

Hydroxyproline in Urine Microvesicles as a Biomarker of Fibrosis in the Renal Transplant Patient

Background/Objectives: Interstitial fibrosis/tubular atrophy in kidney transplantation is an unspecific lesion induced by immune and non-immune factors, which determines the progression of chronic kidney disease. Hydroxyproline is an imino acid that is part of the molecule of collagen. The aim of this study was to assess hydroxyproline in urine microvesicles as a marker of fibrosis in the renal transplant patient. Patients and Methods: An observational cross-sectional study was conducted on 46 renal transplant patients who had undergone renal biopsy with diagnostic intention, as well as 19 healthy controls. Clinical, histological, and laboratory variables were collected at the time of marker determination and renal function was analyzed 2 years later. Hydroxyproline was measured in urine microvesicles. Results: Renal transplant patients showed a higher microvesicular concentration of hydroxyproline compared to the control group, with the following medians (interquartile range (IQR)): 28.024 (5.53) ng/mL vs. 2.51 (1.16) ng/mL, p < 0.001. In the transplanted patients, patients in whom biopsy showed some score of total cortical parenchymal inflammation (ti) displayed a significantly higher concentration of hydroxyproline in urine microvesicles than those patients who did not score for cortical parenchymal inflammation (29.91 ± 2.797 ng/mL vs. 22.72 ± 8.697 ng/mL, p = 0.034). No significant correlation was observed between urinary markers and serum creatinine, calcium, and parathyroid hormone (PTH). Conclusions: The concentration of hydroxyproline in urinary microvesicles increased in renal transplant patients relative to healthy controls. Hydroxyproline in urinary microvesicles is a marker of chronic renal inflammation in transplanted patients, and further studies are required to confirm this finding in other pathologies, as well as the association with fibrosis and the evolution of renal function.

Development of a spontaneous model of renal interstitial fibrosis in NOD/SCID mice: Aging-induced pathogenesis

Renal interstitial fibrosis, a condition prevalent in aging humans and animals, is closely linked to the eventual development of renal failure. Establishing an animal model that exactly replicates the pathogenesis of renal interstitial fibrosis induced by natural aging in humans is crucial for advancing mechanistic studies and testing antifibrotic therapies. Implanted allogeneic or xenogeneic cells are cleared by the immune system when stem cell therapy is applied in nonimmunodeficient animal fibrosis models, affecting the effect of the intervention and making it difficult to demonstrate the survival, proliferation, differentiation, or secretion of the delivered autologous human-derived cells. This study effectively developed a model of spontaneous renal interstitial fibrosis linked to natural aging in 43-week-old NOD/SCID mice. Compared with those of 12- and 32-week-old mice, the kidneys of the model mice exhibited prominent fibrosis characteristics, accompanied by numerous fibrous septa and collagen deposition, increased COL1A1 expression, and decreased MMP9 expression. SA-β-gal activity and P21 gene expression levels increased, confirming renal cell senescence in the model mice. Additionally, an increase in α-SMA staining indicated an increase in epithelial-mesenchymal transition. More importantly, we observed TGF-β-SMAD3 pathway activation, mitochondrial dysfunction, decreased antioxidant capacity, oxidative stress, and an enhanced inflammatory response in the model group, consistent with renal interstitial fibrosis in elderly individuals. In this comprehensive investigation, we successfully developed a spontaneous mouse model of renal interstitial fibrosis and revealed the molecular pathways contributing to increased susceptibility to kidney injury and renal fibrosis in elderly individuals.

Deciphering the Complexity of the Immune Cell Landscape in Kidney Allograft Rejection

While the Banff classification dichotomizes kidney allograft rejection based on the localization of the cells in the different compartments of the cortical kidney tissue [schematically interstitium for T cell mediated rejection (TCMR) and glomerular and peritubular capillaries for antibody-mediated rejection (AMR)], there is a growing evidences that subtyping the immune cells can help refine prognosis prediction and treatment tailoring, based on a better understanding of the pathophysiology of kidney allograft rejection. In the last few years, multiplex IF techniques and automatic counting systems as well as transcriptomics studies (bulk, single-cell and spatial techniques) have provided invaluable clues to further decipher the complex puzzle of rejection. In this review, we aim to better describe the inflammatory infiltrates that occur during the course of kidney transplant rejection (active AMR, chronic active AMR and acute and chronic active TCMR). We also discuss minor components of the inflammatory response (mastocytes, eosinophils, neutrophils, follicular dendritic cells). We conclude by discussing whether the over simplistic dichotomy between AMR and TCMR, currently used in clinical routine, remains relevant given the great diversity of immune actors involved in rejections.

Impact of renal allograft histopathological findings on transplant patient outcomes and graft survival: A retrospective single-center study

INTRODUCTION

This study aimed to evaluate the reasons for kidney transplant dysfunction by analyzing allograft biopsy findings. We also compared clinical outcomes and graft survival rates in patients with and without de novo donor-specific antibodies (DSA).

METHODS

This retrospective observational cohort study included 79 patients who underwent kidney allograft biopsy. The patients were divided into two groups based on the presence of anti-human leukocyte antigens (HLA) DSA antibodies. Laboratory evaluations included HLA-DSA and serum creatinine levels. The immunosuppressive therapy protocols were as follows: patients with single-antigen bead-measured sensitization (panel reactive antibody >50 %) received induction therapy, and all patients received triple therapy with tacrolimus or cyclosporine, prednisone, and mycophenolate sodium.

RESULTS

Acute antibody-mediated rejection (AMR) occurred in 20.2 % of patients, whereas acute T-cell-mediated rejection (TCMR) was observed in 14 %. Interstitial fibrosis and tubular atrophy were observed in 53.8 % and 69.2 % of patients with de novo DSA, respectively, compared with 15.2 % and 87.9 % in the non-DSA group. Calcineurin inhibitors induced nephrotoxicity in 11.4 %, relapse of the underlying disease in 13.9 %, and infection in 7.6 % of biopsies. Differences in serum creatinine levels were observed between the de novo DSA and non-DSA groups from the third (p = 0.039), fifth (p = 0.028), and seventh years of follow-up (p = 0.012). The graft survival rate was lower in patients with de novo DSA than in those without (p = 0.036).

CONCLUSIONS

TCMR and AMR were the most common findings. The occurrence of AMR significantly impacted renal function and graft survival, and patients with de novo anti-HLA antibodies had poorer outcomes.

Validation of histopathological chronicity scores in native kidney biopsies using light microscopy and digital morphometry for predicting renal outcome

Quantitative assessment of chronicity changes in native kidney biopsies offer valuable insights in to disease prognosis, despite the strength of qualitative information. Yet, standardization and reproducibility remain challenging. The present study aims to assess and compare the prognostic utility and reproducibility of two chronicity scoring systems based on light microscopy and whole slide imaging with morphometry and also to evaluate the prognostic utility of structural measurements: cortical non-sclerotic glomerular (NSG) density and NSG area/volume. We designed a retrospective longitudinal study involving 101 adult and paediatric patients who underwent native kidney biopsies. Chronicity scoring was performed using two semi-quantitative methods: Method 1 (method proposed in PMID: 28314581) and Method 2 (method proposed in PMID: 32516862), under light microscopy as well as on whole-slide scanned images, and assessed for prognostic utility. Kidney-Failure-Risk-Equation (KFRE) was employed in combination with chronicity-scoring-methods and assessed for predictive capability. Interobserver reproducibility for the two chronicity methods was studied among three renal pathologists. Structural measurements were performed on whole-slide- scanned-images. Both the chronicity scoring methods significantly predicted decline in estimated glomerular filtration rate (eGFR) and persistent need for renal replacement therapy in follow-up. Method 1 combined with KFRE, outperformed Method 2 in predicting renal survival. Method 2 however showed higher interobserver reproducibility. Combined KFRE plus histopathological scoring methods showed better predictive accuracy. The study validates the precision of chronicity scoring using whole slide scanned images. The morphometric structural measurements showed significant correlations with follow-up eGFR, thereby providing supplementary prognostic information.

Acute kidney disease in mice is associated with early cardiovascular dysfunction

Acute kidney injury (AKI) and chronic kidney disease (CKD) are major health concerns due to their increasing incidence and high mortality. They are interconnected syndromes; AKI without recovery evolves into acute kidney disease (AKD), which can indicate an AKI-to-CKD transition. Both AKI and CKD are associated with a risk of long-term cardiovascular complications, but whether vascular and cardiac dysfunctions can occur as early as the AKD period has not been studied extensively. In a mouse model of kidney injury (KI) with non-recovery, we performed vasoreactivity and echocardiography analyses on days 15 (D15) and 45 (D45) after KI. We determined the concentrations of two major gut-derived protein-bound uremic toxins known to induce cardiovascular toxicity-indoxyl sulfate (IS) and para-cresyl sulfate (PCS)-and the levels of inflammation and contraction markers on D7, D15, and D45. Mice with KI showed acute tubular and interstitial kidney lesions on D7 and D15 and chronic glomerulosclerosis on D45. They showed significant impairment of aorta relaxation and systolic-diastolic heart function, both on D15 and D45. Such dysfunction was associated with downregulation of the expression of two contractile proteins, αSMA and SERCA2a, with a more pronounced effect on D15 than on D45. KI was also followed by a rapid increase in IS and PCS serum concentrations and the expression induction of pro-inflammatory cytokines and endothelial adhesion molecules in serum and cardiovascular tissues. Therefore, these results highlight that AKD leads to early cardiac and vascular dysfunctions. How these dysfunctions could be managed to prevent cardiovascular events deserves further study.

Towards accurate and efficient diagnoses in nephropathology: An AI-based approach for assessing kidney transplant rejection

The Banff classification is useful for diagnosing renal transplant rejection. However, it has limitations due to subjectivity and varying concordance in physicians' assessments. Artificial intelligence (AI) can help standardize research, increase objectivity and accurately quantify morphological characteristics, improving reproducibility in clinical practice. This study aims to develop an AI-based solutions for diagnosing acute kidney transplant rejection by introducing automated evaluation of prognostic morphological patterns. The proposed approach aims to help accurately distinguish borderline changes from rejection. We trained a deep-learning model utilizing a fine-tuned Mask R-CNN architecture which achieved a mean Average Precision value of 0.74 for the segmentation of renal tissue structures. A strong positive nonlinear correlation was found between the measured infiltration areas and fibrosis, indicating the model's potential for assessing these parameters in kidney biopsies. The ROC analysis showed a high predictive ability for distinguishing between ci and i scores based on infiltration area and fibrosis area measurements. The AI model demonstrated high precision in predicting clinical scores which makes it a promising AI assisting tool for pathologists. The application of AI in nephropathology has a potential for advancements, including automated morphometric evaluation, 3D histological models and faster processing to enhance diagnostic accuracy and efficiency.

Determinants and impact of calcium oxalate crystal deposition on renal outcomes in acute kidney injury patients

OBJECTIVES

Calcium oxalate (CaOx) crystal deposition in acute kidney injury (AKI) patients is under recognized but impacts renal outcomes. This study investigates its determinants and effects.

METHODS

We studied 814 AKI patients with native kidney biopsies from 2011 to 2020, identifying CaOx crystal deposition severity (mild: <5, moderate: 5-10, severe: >10 crystals per section). We assessed factors like urinary oxalate, citrate, urate, electrolytes, pH, tubular calcification index, and SLC26A6 expression, comparing them with creatinine-matched AKI controls without oxalosis. We analyzed how these factors relate to CaOx severity and their impact on renal recovery (eGFR < 15 mL/min/1.73 m2 at 3-month follow-up).

RESULTS

CaOx crystal deposition was found in 3.9% of the AKI cohort (32 cases), with 72% due to nephrotoxic medication-induced tubulointerstitial nephritis. Diuretic use, higher urinary oxalate-to-citrate ratio induced by hypocitraturia, and tubular calcification index were significant contributors to moderate and/or severe CaOx deposition. Poor baseline renal function, low urinary chloride, high uric acid and urea nitrogen, tubular SLC26A6 overexpression, and glomerular sclerosis were also associated with moderate-to-severe CaOx deposition. Kidney recovery was delayed, with 43.8%, 31.2%, and 18.8% of patients having eGFR < 15 mL/min/1.73 m2 at 4, 12, and 24-week post-injury. Poor outcomes were linked to high urinary α1-microglobulin-to-creatinine (α1-MG/C) ratios and active tubular injury scores. Univariate analysis showed a strong link between this ratio and poor renal outcomes, independent of oxalosis severity.

CONCLUSIONS

In AKI, CaOx deposition is common despite declining GFR. Factors worsening tubular injury, not just oxalate-to-citrate ratios, are key to understanding impaired renal recovery.

Physician-Directed Mycophenolate Mofetil Dose Reduction After Kidney Transplantation: A Multicenter Real Word Experience

BACKGROUND

Mycophenolate mofetil (MMF) dose is commonly reduced after kidney transplantation (KT). This study examined MMF dosing in the first 5 years after KT to determine if a lower MMF dose impacted outcomes.

METHODS

We retrospectively studied 432 recipients who underwent KT between February 2012 and February 2015 in 3 centers. Induction was with IL-2 receptor blocker (23%) or depleting antibody (67%) and maintenance was with calcineurin inhibitor, MMF 1.5 to 2g/day and in 70% prednisone. MMF dose was reduced within the first post-KT year as clinically indicated or for elevated mycophenolic acid (MPA) levels. All 432 patients underwent 1-year protocol biopsy. Donor-specific antibodies (DSAs) were assessed at 1 year.

RESULTS

At 1 year, 219 KT recipients (51%) received standard MMF (> 1 g/day) and 213 (49%) received low MMF (≤ 1 gr/d). Low MMF was for clinical indication (49%) or elevated MPA level (51%). At 1 year, there was no difference in rejection rate, type and degree of rejection, degree of inflammation, or DSA formation between the low and standard MMF groups (P = not significant [NS]). The reason for MMF dose reduction did not impact outcome. By 5 years, 69% of the KT recipients were on ≤ 1 g/d MMF. The 5-year patient and death-censored graft survival were comparable between the low and standard MMF groups.

CONCLUSIONS

Almost 50% of KT recipients were on low dose MMF at 1 year and this percentage increased by 5 years. We did not observe a difference in outcomes between those on standard or low MMF dose regardless of the reason for dose reduction. Physician-directed MMF dose-reduction may be safe but randomized studies are needed to validate this finding.

Diverse regulated cell death patterns and immune traits in kidney allograft with fibrosis: a prediction of renal allograft failure based on machine learning, single-nucleus RNA sequencing and molecular docking

Objectives: Post-transplant allograft fibrosis remains a challenge in prolonging allograft survival. Regulated cell death has been widely implicated in various kidney diseases, including renal fibrosis. However, the role of different regulated cell death (RCD) pathways in post-transplant allograft fibrosis remains unclear.

Methods and Results: Microarray transcriptome profiling and single-nuclei sequencing data of post-transplant fibrotic and normal grafts were obtained and used to identify RCD-related differentially expressed genes. The enrichment activity of nine RCD modalities in tissue and cells was examined using single-sample gene set enrichment analysis, and their relations with immune infiltration in renal allograft samples were also assessed. Parenchymal and non-parenchymal cells displayed heterogeneity in RCD activation. Additionally, cell-cell communication analysis was also conducted in fibrotic samples. Subsequently, weighted gene co-expression network analysis and seven machine learning algorithms were employed to identify RCD-related hub genes for renal fibrosis. A 9-gene signature, termed RCD risk score (RCDI), was constructed using the least absolute shrinkage and selection operator and multivariate Cox regression algorithms. This signature showed robust accuracy in predicting 1-, 2-, and 3-year allograft survival status (area under the curve for 1-, 2-, and 3-year were 0.900, 0.877, 0.858, respectively). Immune infiltration analysis showed a strong correlation with RCDI and the nine model genes. Finally, molecular docking simulation suggested rapamycin, tacrolimus and mycophenolate mofetil exhibit strong interactions with core RCD-related receptors.

Conclusions: In summary, this study explored the activation of nine RCD pathways and their relationships with immune traits, identified potential RCD-related hub genes associated with renal fibrosis, and highlighted potential therapeutic targets for renal allograft fibrosis.

Current and emerging tools for simultaneous assessment of infection and rejection risk in transplantation

Infection and rejection are major complications that impact transplant longevity and recipient survival. Balancing their risks is a significant challenge for clinicians. Current strategies aimed at interrogating the degree of immune deficiency or activation and their attendant risks of infection and rejection are imprecise. These include immune (cell counts, function and subsets, immunoglobulin levels) and non-immune (drug levels, viral loads) markers. The shared risk factors between infection and rejection and the bidirectional and intricate relationship between both entities further complicate transplant recipient care and decision-making. Understanding the dynamic changes in the underlying net state of immunity and the overall risk of both complications in parallel is key to optimizing outcomes. The allograft biopsy is the current gold standard for the diagnosis of rejection but is associated with inherent risks that warrant careful consideration. Several biomarkers, in particular, donor derived cell-free-DNA and urinary chemokines (CXCL9 and CXCL10), show significant promise in improving subclinical and clinical rejection risk prediction, which may reduce the need for allograft biopsies in some situations. Integrating conventional and emerging risk assessment tools can help stratify the individual's short- and longer-term infection and rejection risks in parallel. Individuals identified as having a low risk of rejection may tolerate immunosuppression wean to reduce medication-related toxicity. Serial monitoring following immunosuppression reduction or escalation with minimally invasive tools can help mitigate infection and rejection risks and allow for timely diagnosis and treatment of these complications, ultimately improving allograft and patient outcomes.

Image-guided renal parenchymal biopsies- how we do it

This paper is a multi-institutional review of image-guided renal parenchymal biopsies. Among the topics covered are indications, preprocedural considerations, biopsy technique, complications, and postprocedural management. Both native kidney and transplant kidney biopsies are considered in this review.

Re-Evaluating the Transplant Glomerulopathy Lesion-Beyond Donor-Specific Antibodies

There have been significant advances in short-term outcomes in renal transplantation. However, longer-term graft survival has improved only minimally. After the first post-transplant year, it has been estimated that chronic allograft damage is responsible for 5% of graft loss per year. Transplant glomerulopathy (TG), a unique morphologic lesion, is reported to accompany progressive chronic allograft dysfunction in many cases. While not constituting a specific etiologic diagnosis, TG is primarily considered as a histologic manifestation of ongoing allo-immune damage from donor-specific anti-HLA alloantibodies (DSA). In this review article, we re-evaluate the existing literature on TG, with particular emphasis on the role of non-HLA-antibodies and complement-mediated injury, cell-mediated immune mechanisms, and early podocyte stress in the pathogenesis of Transplant Glomerulopathy.

Challenges and opportunities in research on BK virus infection after renal transplantation

Renal transplantation is one of the primary approaches for curing end-stage kidney disease. With advancements in immunosuppressive agents, the short-term and long-term survival rates of transplanted kidneys have significantly improved. However, infections associated with potent immunosuppression have remained a persistent challenge. Among them, BK virus (BKV) reactivation following renal transplantation leading to BK virus-associated nephropathy (BKVAN) is a major cause of graft dysfunction. However, we still face significant challenges in understanding the pathogenesis, prevention, diagnosis, and treatment of BKVAN. These challenges include: 1. The mechanism of BKV reactivation under immunosuppressive conditions has not been well elucidated, leading to difficulties in breakthroughs in clinical research on prevention, diagnosis, and treatment. 2. Lack of proper identification of high-risk individuals, and effective personalized clinical management strategies. 3.Lack of early and sensitive diagnostic markers. 4. Lack of direct and effective treatment options due to the absence of specific antiviral drugs. The purpose of this review is to summarize the current status and cutting-edge advancements in BKV-related research, providing new methods and perspectives to address future research challenges.

Towards clinical translation of urinary vitronectin for non-invasive detection and monitoring of renal fibrosis in kidney transplant patients

BACKGROUND

Interstitial fibrosis and tubular atrophy (IFTA) is a critical factor in the prognosis of kidney health. Currently, IFTA quantitation in kidney biopsy samples is crucial for diagnosis and assessing disease severity, but the available non-invasive biomarkers are not satisfactory. Proteomic studies identified urinary vitronectin (VTN) as a potential biomarker for kidney fibrosis. As mass spectrometry techniques are not practical for use in clinical settings, we tested whether evaluation of urinary VTN levels through enzyme-linked immunosorbent assay (ELISA) can help monitor fibrotic changes in kidney transplant recipients and prove the clinical viability of the assay.

METHODS

A total of 58 kidney transplant (KTx) patients who underwent renal biopsy were included in the study. Patients were categorized into two groups referred as no fibrosis (0%) or with fibrosis (≥ 5%) based on their histological findings. In a subsequent/follow-up analysis, the time elapsed from transplantation was also considered. The urinary levels of VTN were measured using ELISA.

RESULTS

VTN (p = 0.0180) and VTN normalized by urinary creatinine levels (p = 0.0037), were significantly increased in patients with fibrotic grafts. When focusing on patients with long-term grafts (> 3 years from transplantation, n = 36), VTN exhibited superior potential in identifying fibrotic grafts compared to albuminuria (VTN p = 0.0040 vs. albuminuria p = 0.0132). Importantly, in this group, while albuminuria correctly identified 71% of fibrotic patients, the combination of VTN plus albuminuria correctly classified 89% of fibrotic grafts detected by renal biopsy.

CONCLUSIONS

VTN has emerged as a valid indicator of renal fibrosis. Of interest, urinary levels of VTN in combination with conventional clinical parameters (such as albuminuria) significantly improved the non-invasive detection of renal fibrosis in kidney transplant patients.

The Use of Machine Learning in the Diagnosis of Kidney Allograft Rejection: Current Knowledge and Applications

Kidney allograft rejection is one of the main limitations to long-term kidney transplant survival. The diagnostic gold standard for detecting rejection is a kidney biopsy, an invasive procedure that can often give imprecise results due to complex diagnostic criteria and high interobserver variability. In recent years, several additional diagnostic approaches to rejection have been investigated, some of them with the aid of machine learning (ML). In this review, we addressed studies that investigated the detection of kidney allograft rejection over the last decade using various ML algorithms. Various ML techniques were used in three main categories: (a) histopathologic assessment of kidney tissue with the aim to improve the diagnostic accuracy of a kidney biopsy, (b) assessment of gene expression in rejected kidney tissue or peripheral blood and the development of diagnostic classifiers based on these data, (c) radiologic assessment of kidney tissue using diffusion-weighted magnetic resonance imaging and the construction of a computer-aided diagnostic system. In histopathology, ML algorithms could serve as a support to the pathologist to avoid misclassifications and overcome interobserver variability. Diagnostic platforms based on biopsy-based transcripts serve as a supplement to a kidney biopsy, especially in cases where histopathologic diagnosis is inconclusive. ML models based on radiologic evaluation or gene signature in peripheral blood may be useful in cases where kidney biopsy is contraindicated in addition to other non-invasive biomarkers. The implementation of ML-based diagnostic methods is usually slow and undertaken with caution considering ethical and legal issues. In summary, the approach to the diagnosis of rejection should be individualized and based on all available diagnostic tools (including ML-based), leaving the responsibility for over- and under-treatment in the hands of the clinician.

Predicting prognostic factors in kidney transplantation using a machine learning approach to enhance outcome predictions: a retrospective cohort study

BACKGROUND

Accurate forecasting of clinical outcomes after kidney transplantation is essential for improving patient care and increasing the success rates of transplants. The authors' study employs advanced machine learning (ML) algorithms to identify crucial prognostic indicators for kidney transplantation. By analyzing complex datasets with ML models, the authors aim to enhance prediction accuracy and provide valuable insights to support clinical decision-making.

MATERIALS AND METHODS

Analyzing data from 4077 KT patients (June 1990-May 2015) at a single center, this research included 27 features encompassing recipient/donor traits and peri-transplant data. The dataset was divided into training (80%) and testing (20%) sets. Four ML models-eXtreme Gradient Boosting (XGBoost), Feedforward Neural Network, Logistic Regression, And Support Vector Machine-were trained on carefully selected features to predict the success of graft survival. Performance was assessed by precision, sensitivity, F1 score, area under the receiver operating characteristic (AUROC), and area under the precision-recall curve.

RESULTS

XGBoost emerged as the best model, with an AUROC of 0.828, identifying key survival predictors like T-cell flow crossmatch positivity, creatinine levels two years post-transplant and human leukocyte antigen mismatch. The study also examined the prognostic importance of histological features identified by the Banff criteria for renal biopsy, emphasizing the significance of intimal arteritis, interstitial inflammation, and chronic glomerulopathy.

CONCLUSION

The study developed ML models that pinpoint clinical factors crucial for KT graft survival, aiding clinicians in making informed post-transplant care decisions. Incorporating these findings with the Banff classification could improve renal pathology diagnosis and treatment, offering a data-driven approach to prioritizing pathology scores.

Glomerulitis in T cell-mediated renal allograft rejection and antibody-mediated rejection histology in the absence of donor-specific antibodies heralds a similar clinico-morphologic pattern of injury to an antibody-mediated rejection: A systematic review

The morphologic finding of transplant glomerulitis (g) forms important evidence of microvascular injury. Besides antibody-mediated rejection (ABMR), this morphological feature is also seen in acute cellular rejection (ACR) and vasculitis but not included in the grading criteria for cellular rejection. A systematic review was thus conducted to summarize the current evidence and shed light on the quantum of impetus to be given to this finding when encountered during evaluation of renal biopsies. Out of a total of 13 studies selected, 06 studies supported the histologic finding of glomerulitis in ACR and non-DSA ABMR morphologies with variable incidence ranging from 15 to 21%. Seven studies supported glomerulitis as an independent prognostic marker for graft outcome at 1 year post transplant with or without DSA with highest HR reported of 4.52 and lowest being 01. Reviewing the present literature revealed interesting insights into occurrence, nature, molecular expression, role in glomerular injury and long-term outcomes with glomerulitis. It is recommended to approach the treatment of such lesions with heightened caution, as there appear to be elevated rates of graft failure, delayed graft function and Transplant glomerulopathy.

Association of gut microbiota with allograft injury in kidney transplant recipients: a comparative profiling through 16S metagenomics and quantitative PCR

Introduction. The existence of a mutual relationship between gut microbiota and immune homeostasis highlights its importance in the context of kidney transplantation.Gap statement. The translational utility of gut microbiota as a biomarker for allograft injury has not been assessed before.Aim. In this study, we aimed to characterize the gut microbial diversity in kidney transplant recipients and investigate the alterations in the gut microbial composition in association with allograft injury such as histopathological graft rejection and calcineurin inhibitor toxicity. In addition, we compared the gut microbial quantitation using 16S metagenomics and quantitative PCR (qPCR) to assess its translational utility.Methodology. In this prospective longitudinal cohort study, we enrolled 38 kidney transplant recipients and collected serial faecal specimens (n=114), once before the induction therapy, and twice after transplant, during the first and third month. We characterized the gut microbial composition through 16S rRNA sequencing and qPCR from the DNA isolates of the samples. The recipients were clinically followed up for a median of 600 days post-transplant. Histopathological evidence of allograft rejection and calcineurin inhibitor toxicity were used for the correlational analysis with gut microbial diversity.Results. Significant differences in the gut microbial diversity were observed between the pre- and post-transplant samples. Pre-transplant gut microbiota revealed a higher relative abundance of phylum Bacteroidetes in the allograft rejection group, and a higher relative abundance of phylum Firmicutes was observed in the histopathological features of calcineurin inhibitor toxicity (hCNI toxicity) group. We found a high concordance between 16S metagenomics and qPCR outputs for assessing the gut microbial diversity. Furthermore, the receiver operating characteristic curve analysis has also proven that the pre-transplant levels of gut microbial dysbiosis, as a potential predictive biomarker for allograft injury.Conclusion. Our pilot study found a strong statistical association of gut microbial dysbiosis with kidney allograft injury, highlighting the potential of gut microbiota as a predictive biomarker and that qPCR serves as a more reliable and economic tool for assessing dysbiosis paving the way for its translational utility.

Szabó R, Orbán-Kálmándi R, Hodossy-Takács R, Szilvási A, Szalai Z, Nagy G, Antal-Szalmás P, Nemes B, Bagoly Z. Increased thrombin generation in kidney transplant recipients with donor-specific antibodies directed against human leukocyte antigens

Introduction

The development of de novo anti-HLA donor specific antibodies (DSAs) is associated with poor outcomes in kidney transplant recipients. It is surmised that an interaction between DSAs and the graft endothelium cause tissue injury, however, the exact underlying pathomechanism and optimal management of patients with DSAs remain undetermined.

Aims

We hypothesized that in kidney transplant recipients the presence of DSAs induce hemostasis alterations, including hypercoagulability, as assessed by the thrombin generation assay (TGA). Patients and methods. In this observational cohort study, 27 kidney transplant recipients with DSAs (DSA+ group) and 16 without DSAs (DSA- group) were enrolled. Venous blood samples were obtained, and besides routine laboratory tests, von Willebrand factor antigen (VWF), FVIII activity, soluble E selectin (sEsel), soluble P selectin (sPsel), TGA, clot lysis assay (CLA), complement levels (C3, C4) were measured. To correlate results with potential changes in DSA status over time, patients were followed and reassessed 6 ± 1.5 months later.

Results

VWF and sPsel did not differ between groups, but both parameters were increased in the majority of patients. Endogenous thrombin potential (ETP) was significantly higher in the DSA+ group as compared to DSA- patients (median:1666; IQR:1438-2012 vs. 1230; IQR:1097-1659 nM*min, p=0.0019). Follow-up measurements indicated that the observed hemostasis alterations were not transient. CLA parameters, C3 and C4 did not differ between DSA+ and DSA- groups. The extent of anti-HLA II DSA positivity correlated positively with ETP, while tacrolimus levels negatively correlated with ETP and VWF/FVIII levels.

Conclusions

In patients with anti-HLA class II DSAs, thrombin generation was significantly increased as compared to DSA- kidney transplant recipients, suggesting that the presence of antibodies is associated with hypercoagulability. Tacrolimus levels were negatively associated with TGA parameters. Hypercoagulability, associated with the presence of DSAs, may potentially contribute to the pathomechanism of antibody-mediated graft injury, warranting future prospective studies.

Pediatric kidney transplantation in Europe, a clinical snapshot pilot

Background

Pediatric kidney transplantations are rarely performed, and there is limited knowledge about the diversity in current clinical practices across Europe. This study aims to explore the utility of clinical snapshot studies in identifying these disparities, establishing a foundation for future snapshot studies and standardization efforts.

Methods

A pilot clinical snapshot study was conducted, with invitations extended to all 109 pediatric kidney transplant centres in Europe. Each participating centre provided pre-, peri-, and postoperative data concerning their most recent thirty transplantations. The primary outcomes encompassed the evaluation of disparities in donor-recipient selection, surgical techniques, post-operative drainage procedures, and immunosuppressive therapy protocols. Secondary outcomes involved the analysis of rejection rates, incidence of infections, and graft survival.

Results

The study involved 439 patients from fifteen centres (14%) in twelve countries, with varying transplant volumes (range 1-29 transplantations per year) and follow-up periods. Significant differences were found among centres in terms of donor types, cold and warm ischemia time, pre-emptive transplant rates, and kidney transplant drainage methods. The rate of living donors varied between 3% and 90% and the median duration of cold ischemia ranged was 770 min after deceased donation and 147 min after living donation. Basiliximab was the dominant induction therapy, yet steroid withdrawal varied widely. Infection, rejection, and graft survival rates also varied significantly between centres.

Conclusion

This study revealed substantial variation in clinical practices among European centres performing pediatric kidney transplantations. These findings could serve as a stimulus for international dialogue and collaboration.

Plasma exchange and intravenous immunoglobulin prolonged the survival of a porcine kidney xenograft in a sensitized, deceased human recipient

BACKGROUND

The primary limitation to kidney transplantation is organ shortage. Recent progress in gene editing and immunosuppressive regimens has made xenotransplantation with porcine organs a possibility. However, evidence in pig-to-human xenotransplantation remains scarce, and antibody-mediated rejection (AMR) is a major obstacle to clinical applications of xenotransplantation.

METHODS

We conducted a kidney xenotransplantation in a deceased human recipient using a porcine kidney with five gene edits (5GE) on March 25th, 2024 at Xijing Hospital, China. Clinical-grade immunosuppressive regimens were employed, and the observation period lasted 22 days. We collected and analyzed the xenograft function, ultrasound findings, sequential protocol biopsies, and immune surveillance of the recipient during the observation.

RESULTS

The combination of 5GE in the porcine kidney and clinical-grade immunosuppressive regimens prevented hyperacute rejection. The xenograft kidney underwent delayed graft function in the first week, but urine output increased later and the single xenograft kidney maintained electrolyte and pH homeostasis from postoperative day (POD) 12 to 19. We observed AMR at 24 h post-transplantation, due to the presence of pre-existing anti-porcine antibodies and cytotoxicity before transplantation; this AMR persisted throughout the observation period. Plasma exchange and intravenous immunoglobulin treatment mitigated the AMR. We observed activation of latent porcine cytomegalovirus toward the end of the study, which might have contributed to coagulation disorder in the recipient.

CONCLUSIONS

5GE and clinical-grade immunosuppressive regimens were sufficient to prevent hyperacute rejection during pig-to-human kidney xenotransplantation. Pre-existing anti-porcine antibodies predisposed the xenograft to AMR. Plasma exchange and intravenous immunoglobulin were safe and effective in the treatment of AMR after kidney xenotransplantation.

Prediction of allograft function in pre-transplant kidneys using sound touch elastography (STE): an ex vivo study

BACKGROUND

The purpose of the study was to evaluate renal quality and predict posttransplant graft function using ex vivo sound touch elastography (STE).

METHODS

In this prospective study, 106 donor kidneys underwent ex vivo STE examination and biopsy from March 2022 to August 2023. The mean stiffness of the superficial cortex (STEsc), deep cortex (STEdc), and medulla (STEme) was obtained and synthesized into one index (STE) through the factor analysis method. Additionally, 100 recipients were followed up for 6 months. A random forest algorithm was employed to explore significant predictive factors associated with the Remuzzi score and allograft function. The performance of parameters was evaluated by using the area under the receiver operating characteristic curve (AUC).

RESULTS

STE had AUC values of 0.803 for diagnosing low Remuzzi and 0.943 for diagnosing high Remuzzi. Meanwhile, STE had an AUC of 0.723 for diagnosing moderate to severe ATI. Random forest algorithm identified STE and Remuzzi score as significant predictors for 6-month renal function. The AUC for STE in predicting postoperative allograft function was 0.717, which was comparable with that of the Remuzzi score (AUC = 0.756). Nevertheless, the specificity of STE was significantly higher than that of Remuzzi (0.913 vs 0.652, p < 0.001). Given these promising results, donor kidneys can be transplanted directly without the need for biopsy when STE ≤ 11.741.

CONCLUSIONS

The assessment of kidney quality using ex vivo STE demonstrated significant predictive value for the Remuzzi score and allograft function, which could help avoid unnecessary biopsy.

CRITICAL RELEVANCE STATEMENT

Pre-transplant kidney quality measured with ex vivo STE can be used to assess donor kidney quality and avoid unnecessary biopsy.

KEY POINTS

STE has significant value for diagnosing low Remuzzi and high Remuzzi scores. STE achieved good performance in predicting posttransplant allograft function. Assessment of kidney quality using ex vivo STE could avoid unnecessary biopsies.

Early CYP3A5 Genotype-Based Adjustment of Tacrolimus Dosage Reduces Risk of De Novo Donor-Specific HLA Antibodies and Rejection among CYP3A5-Expressing Renal Transplant Patients

BACKGROUND/OBJECTIVES

Our previous retrospective single-center cohort study found, at 3-year follow-up, a trend toward low tacrolimus trough levels and an increased risk of de novo donor-specific anti-HLA antibodies (DSAs) and of antibody-mediated rejection (ABMR) in CYP3A5-expressing patients. Determining CYP3A5-expression status immediately after renal transplant would allow early genotype-based dosage adjustment of tacrolimus and might prevent the occurrence of de novo DSAs and ABMR, improving transplant outcome.

METHODS

160 renal allograft recipients who underwent renal transplant at the University Hospital Essen between May 2019 and May 2022 were genotyped for the CYP3A5 rs776746 polymorphism within the first two weeks after transplant, and genotype-based dose adjustment of tacrolimus was performed for the follow-up of 2 years.

RESULTS

CYP3A5 expression was detected in 33 (21%) of the 160 patients. Tacrolimus trough levels were similar in CYP3A5 expressers and nonexpressers over the entire 2-year follow-up period. However, we observed a trend toward slightly higher tacrolimus trough levels in CYP3A5 expressers, who, as expected, required tacrolimus dosages twice as high as did nonexpressers during follow-up. Calcineurin inhibitor (CNI) nephrotoxicity-free survival rates were comparable between CYP3A5 expressers and nonexpressers (p = 0.49). Rejection-free survival rates (p = 0.89), de novo anti-HLA antibody-free survival rates (p = 0.57) and de novo DSA-free survival rates (p = 0.61) did not differ between the two groups.

CONCLUSIONS

Early detection of CYP3A5-expression status and resultant genotype-based adjustment of tacrolimus dosage after renal transplant protected patients from transplant rejection and de novo DSA formation and was not associated with increased incidence of CNI toxicity among CYP3A5 expressers.