Adult Kidney Research Articles

Safety and efficacy of one and two booster doses of SARS-CoV-2 mRNA vaccines in kidney transplant recipients: A randomized clinical trial.

Kidney transplant recipients are at risk for a severe course of COVID-19 with a high mortality rate. A considerable number of patients remains without a satisfactory serological response after the baseline and adjuvant SARS-CoV-2 vaccination schedule. In this prospective, randomized study, we evaluated the efficacy and safety of one and two booster doses of mRNA vaccines (either mRNA-1273 or BNT162b2) in 125 COVID-19 naive, adult kidney transplant recipients who showed an insufficient humoral response (SARS-CoV-2 IgG <10 AU/ml) to the previous 2-dose vaccination schedule. The primary outcome was the difference in the rate of a positive antibody response (SARS-CoV-2 IgG ≥10 AU/ml) between one and two booster doses at 1 month after the final booster dose. A positive humoral response was observed in 36 (62%) patients receiving two booster doses and in 28 (44%) patients receiving one booster dose (odds ratio [OR], 2.10, 95% confidence interval [CI], 1.02-4.34, p = .043). Moreover, median SARS-CoV-2 IgG levels were higher with two booster doses (p = .009). The number of patients with positive virus neutralizing antibody (VNA) levels was numerically higher with two booster doses compared to one booster dose, but without statistical significance (66%vs. 50%, p = .084). There was no significant difference in positive seroconversions rate and antibody levels between mRNA-1273 and BNT162b2. A higher number of kidney transplant recipients achieved a positive antibody response after two booster doses compared to one booster dose.

Early outcomes of peritoneal dialysis in a middle-income country: A retrospective cohort study of a large dialysis network in Colombia.

The first year of dialysis is critical given the significant risk for complications following dialysis initiation. We analysed complications during the first year among incident peritoneal dialysis (PD) patients. This retrospective cohort study comprised adult kidney failure patients starting PD in Baxter Renal Care Services in Colombia, receiving their first PD catheter between 1 January 2017 and 31 December 2020 and were followed up for up to 1 year. We analysed incidence, causes and factors associated with complications using logistic regression and transfer to haemodialysis (HD) using the Fine-Gray regression model. Among 4743 patients receiving their first PD catheter: 4628 (97.6%) of catheter implantations were successful; 377 (7.9%) patients experienced early complications. The incidence rate of complications during the year was 0.51 events per patient-year (95% CI: 0.48-0.54). Age, obesity and urgent start were associated with higher probability of complications after catheter implantation. The cumulative incidence of transfer to HD within 1 year of PD initiation was 10.1% [95% CI: 9.2-11.1%]. The hazard function for transfer to HD showed an accelerating pattern during the first month followed by progressive decrease during the first year. In this large population of incident PD patients, there is a high primary catheter placement success rate. Urgent start, age ≥65 years, obesity, centre size ≥150 PD patients and diabetes were risk factors associated with early complications. The follow-up of the cohort from day 1 of PD treatment showed that the risk for transfer to HD was higher during the first month.

Kidney Donation After Circulatory Death Using Thoracoabdominal Normothermic Regional Perfusion: The Largest Report of the United States Experience.

Thoracoabdominal normothermic regional perfusion (TA-NRP) has been increasingly used for donation after circulatory death (DCD) procurements in the United States. We present the largest report of outcomes of kidney transplants performed using DCD donor grafts perfused with TA-NRP. Adult DCD kidney transplants between 2020 and 2022 in the United Network for Organ Sharing database were included. Donors with ≥50 min between asystole and aortic cross-clamp time in which the heart was also transplanted were considered TA-NRP donors. All other donors were considered direct recovery donors. Multivariable regressions were used to assess delayed graft function, as well as posttransplant survival and all-cause graft failure at 30, 90, and 180 d. A propensity-matched analysis of cohorts matched on donor Kidney Donor Profile Index was performed. Of the 16 140 total DCD kidney transplants performed during the study period, 306 (1.9%) used TA-NRP. TA-NRP donors were younger ( P < 0.001) and had lower Kidney Donor Profile Index ( P < 0.001) compared with direct recovery donors. Recipients receiving grafts recovered using TA-NRP were younger ( P < 0.001) and more likely to be blood group O ( P < 0.001). Transplants using TA-NRP had lower likelihood of delayed graft function (adjusted odds ratio 0.22 [95% confidence interval, 0.15-0.31], P < 0.001) but similar 180-d survival ( P = 0.8) and all-cause graft failure ( P = 0.3) as transplants using direct recovery grafts. These inferences were unchanged on propensity-matched analysis. Our results demonstrate that kidney transplants using TA-NRP DCD allografts have positive short-term mortality and graft survival outcomes, with significantly decreased rates of delayed graft function compared with direct recovery DCD grafts.

STGNNks: Identifying cell types in spatial transcriptomics data based on graph neural network, denoising auto-encoder, and [formula omitted]-sums clustering

Background:Spatial transcriptomics technologies fully utilize spatial location information, tissue morphological features, and transcriptional profiles. Integrating these data can greatly advance our understanding about cell biology in the morphological background. Methods:We developed an innovative spatial clustering method called STGNNks by combining graph neural network, denoising auto-encoder, and k-sums clustering. First, spatial resolved transcriptomics data are preprocessed and a hybrid adjacency matrix is constructed. Next, gene expressions and spatial context are integrated to learn spots’ embedding features by a deep graph infomax-based graph convolutional network. Third, the learned features are mapped to a low-dimensional space through a zero-inflated negative binomial (ZINB)-based denoising auto-encoder. Fourth, a k-sums clustering algorithm is developed to identify spatial domains by combining k-means clustering and the ratio-cut clustering algorithms. Finally, it implements spatial trajectory inference, spatially variable gene identification, and differentially expressed gene detection based on the pseudo-space-time method on six 10x Genomics Visium datasets. Results:We compared our proposed STGNNks method with five other spatial clustering methods, CCST, Seurat, stLearn, Scanpy and SEDR. For the first time, four internal indicators in the area of machine learning, that is, silhouette coefficient, the Davies-Bouldin index, the Caliniski-Harabasz index, and the S_Dbw index, were used to measure the clustering performance of STGNNks with CCST, Seurat, stLearn, Scanpy and SEDR on five spatial transcriptomics datasets without labels (i.e., Adult Mouse Brain (FFPE), Adult Mouse Kidney (FFPE), Human Breast Cancer (Block A Section 2), Human Breast Cancer (FFPE), and Human Lymph Node). And two external indicators including adjusted Rand index (ARI) and normalized mutual information (NMI) were applied to evaluate the performance of the above six methods on Human Breast Cancer (Block A Section 1) with real labels. The comparison experiments elucidated that STGNNks obtained the smallest Davies-Bouldin and S_Dbw values and the largest Silhouette Coefficient, Caliniski-Harabasz, ARI and NMI, significantly outperforming the above five spatial transcriptomics analysis algorithms. Furthermore, we detected the top six spatially variable genes and the top five differentially expressed genes in each cluster on the above five unlabeled datasets. And the pseudo-space-time tree plot with hierarchical layout demonstrated a flow of Human Breast Cancer (Block A Section 1) progress in three clades branching from three invasive ductal carcinoma regions to multiple ductal carcinoma in situ sub-clusters. Conclusion:We anticipate that STGNNks can efficiently improve spatial transcriptomics data analysis and further boost the diagnosis and therapy of related diseases. The codes are publicly available at https://github.com/plhhnu/STGNNks.

Altered expression, but small contribution, of the histone demethylase KDM6A in obstructive uropathy in mice.

Epigenetic processes have emerged as important modulators of kidney health and disease. Here, we studied the role of KDM6A (a histone demethylase that escapes X-chromosome inactivation) in kidney tubule epithelial cells. We initially observed an increase in tubule cell Kdm6a mRNA in male mice with unilateral ureteral obstruction (UUO). However, tubule cell knockout of KDM6A had relatively minor consequences, characterized by a small reduction in apoptosis, increase in inflammation and downregulation of the peroxisome proliferator-activated receptor (PPAR) signaling pathway. In proximal tubule lineage HK-2 cells, KDM6A knockdown decreased PPARγ coactivator-1α (PGC-1α) protein levels and mRNA levels of the encoding gene, PPARGC1A. Tubule cell Kdm6a mRNA levels were approximately 2-fold higher in female mice than in male mice, both under sham and UUO conditions. However, kidney fibrosis after UUO was similar in both sexes. The findings demonstrate Kdm6a to be a dynamically regulated gene in the kidney tubule, varying in expression levels by sex and in response to injury. Despite the context-dependent variation in Kdm6a expression, knockout of tubule cell KDM6A has subtle (albeit non-negligible) effects in the adult kidney, at least in males.

Abstract 099: Akr1b7 CreERT2 Mice, A New Time And Renin Cell-specific Cre Inducible Model

Gene targeting in renin cells has relied on either non-inducible Cre lines that can introduce developmental effects of gene deletion or BAC transgene-based inducible lines that may be prone to spurious and/or ectopic gene expression. To circumvent these problems, we generated an inducible mouse in which CreERT2 is under the control of the Akr1b7 locus. Akr1b7 , an established marker of renin cells, is co-expressed with renin under different developmental, physiological, and pathological conditions. To study the pattern of Cre expression, we generated Akr1b7 CreERT2/+ ; R26R mTmG/+ mice in which Cre -expressing cells are labeled with GFP upon tamoxifen (Tmx) administration. At E18.5 and P5, GFP was found in Juxtaglomerular (JG) cells, along the arterioles, and in the glomerular mesangium. In adult kidneys, GFP expression was present mainly in JG cells. We did not observe any GFP + cells in vehicle-treated mice, indicating that Cre expression is tightly regulated in this model. In mice given 0.5 g/L captopril in the drinking water and a low-NaCl (0.1%) diet to induce recruitment of renin cells, GFP expression extended along the afferent arterioles and in the mesangium. To study the response to Ren1 deletion in JG cells in the mice, we generated Akr1b7 CreERT2/+ ;Ren1 cFl/- ;R26R mTmG/+ ( Ren1 c cKO) mice. Compared to control mice, Ren1 c cKO mice exhibited a marked reduction in Ren1+ cells by immunostaining and a 80.1% reduction of Ren1 mRNA levels by RT-qPCR (0.19 ± 0.04 vs 0.92 ± 0.26, p= 0.0003). Plasma renin levels were significantly decreased in Ren1 c cKO versus control mice (12,5 ± 7,0 ng/ml vs 53,7 ± 27,9 ng/ml, p= 0.003). In addition, Ren1 c cKO mice had lower mean arterial pressures (68.91 ± 5.27 mmHg vs 82.74 ± 2.63 mmHg, p= 0.0001). When subjected to a low NaCl diet + captopril, Ren1 c cKO mice were able to recruit renin GFP+ cells along arterioles, mesangial cells, and large kidney arteries, suggesting that Ren1 expression in JG cells is dispensable for recruitment. More importantly, the cells can be monitored/tracked by the expression of GFP even when they are unable to express renin.In summary, Akr1b7 CreERT2 mice constitute a suitable model for the spatial and temporal control of gene expression in renin cells and the tracking of cells even when they are not expressing renin.

Prediction models for the recipients' ideal perioperative estimated glomerular filtration rates for predicting graft survival after adult living-donor kidney transplantation.

The impact of the perioperative estimated glomerular filtration rate (eGFR) on graft survival in kidney transplant recipients is yet to be evaluated. In this study, we developed prediction models for the ideal perioperative eGFRs in recipients. We evaluated the impact of perioperative predicted ideal and actual eGFRs on graft survival by including 1,174 consecutive adult patients who underwent living-donor kidney transplantation (LDKT) between January 2008 and December 2020. Prediction models for the ideal perioperative eGFR were developed for 676 recipients who were randomly assigned to the training and validation sets (ratio: 7:3). The prediction models for the ideal best eGFR within 3 weeks and those at 1, 2, and 3 weeks after LDKT in 474 recipients were developed using 10-fold validation and stepwise multiple regression model analyzes. The developed prediction models were validated in 202 recipients. Finally, the impact of perioperative predicted ideal eGFRs/actual eGFRs on graft survival was investigated using Fine-Gray regression analysis. The correlation coefficients of the predicted ideal best eGFR within 3 weeks and the predicted ideal eGFRs at 1, 2, and 3 weeks after LDKT were 0.651, 0.600, 0.598, and 0.617, respectively. Multivariate analyzes for graft loss demonstrated significant differences in the predicted ideal best eGFR/actual best eGFR within 3 weeks and the predicted ideal eGFRs/actual eGFRs at 1, 2, and 3 weeks after LDKT. The predicted ideal best eGFR/actual best eGFR within 3 weeks and the predicted ideal eGFRs/actual eGFRs at 1, 2, and 3 weeks after LDKT were independent prognostic factors for graft loss. Therefore, the perioperative predicted ideal eGFR/actual eGFR may be useful for predicting graft survival after adult LDKT.

Dynamic Changes of Regulatory T Cells/CD4⁺ T Cells in Peripheral Blood of Adult Kidney Transplant Recipients: A Comparison of Pediatric and Adult Kidney Donors.

BACKGROUND Inducing transplantation tolerance and monitoring the recipient's immune status to improve allograft survival remains the main goal for kidney transplantation (KTx). MATERIAL AND METHODS A total of 53 renal transplantation patients and 20 healthy individuals were assigned to the post-transplantation and healthy groups, respectively; 10 recipients with stable renal function for 2 years after kidney transplantation were assigned to Group C. Eleven kidney transplantation recipients were hospitalized due to lung infection. Flow cytometry was used to measure levels of Tregs/CD4⁺ T cells. RESULTS The Tregs/CD4⁺ T cells ratio reached homeostasis 6 months after KTx, with no significant difference between Group D (healthy control group) and pre-surgery or Group C (2 years after KTx group). The pediatric donor group and the adult donor group reached immune homeostasis 3 months after the operation. Immune homeostasis is maintaining a balance between immune tolerance and immunogenicity. There was no significant difference in graft function between the pediatric and adult donor groups before surgery, 1 day after surgery, 1 week after surgery, 2 weeks after surgery, and 1 month after surgery; however, graft function was significantly better in the pediatric donor group compared with the adult donor group at 3 mouths (eGFR: 51.7 (40.4-66.2) vs 73.0 (55.7-90.2), P=0.008<0.05) and 6 months (eGFR: 52.2 (37.5-62.8) vs 80.5 (64.1-90.4), P<0.001) after surgery. Pediatric donor kidneys reached immune homeostasis 3 months after surgery, with better graft function at this time compared with adult donor kidneys. The proportion of Tregs/CD4⁺ T cells in recipients with a pulmonary infection after KTx was lower than in those with infection recovery. CONCLUSIONS Expanding the use of pediatric kidneys should be further explored by the transplantation community. The proportion of Tregs/CD4⁺ T cells in recipients with a pulmonary infection after KTx was lower than in those with infection recovery.

The Effect of the SystemCHANGETM Intervention on Systems Thinking in a Randomized Controlled Trial of Adult Kidney Transplant Recipients: A Secondary Data Analysis

Objective: The SystemCHANGE™ intervention is an approach that harnesses patients′ recurring personal systems of established routines of daily living, environments, and important others as reliable ′personalized system solutions′ to support habitual medication-taking and improve medication adherence. In a secondary data analysis, we (1) analyzed the association between the longitudinal trajectories of systems thinking and medication adherence, and (2) examined the extent that demographic characteristics and the SystemCHANGE™ intervention influenced these trajectories. Methods: Participants were ≥ 18 years of age who had received a kidney???only transplant, self???administered at least one prescribed immunosuppressive medication twice daily, had a functioning kidney transplant, were not in the hospital, and had no diagnosis that would immediately shorten the lifespan. We conducted a single???blinded (participants), 2???arm randomized controlled trial (RCT). An intervention group received the 6-month SystemCHANGETM intervention, and the attention-control group received the 6-month education intervention. Systems thinking was measured using the Systems Thinking Scale (adapted for patients). Results: The parallel process growth curve model with time-invariant predictors suggested that participants with higher levels of systems thinking at baseline demonstrated greater gains in systems thinking over time (r=0.407). White participants exhibited greater baseline levels of systems thinking than African-American participants (d=0.76). Participants assigned to the SystemCHANGE™ group maintained their medication adherence rates over time, whereas control counterparts demonstrated significantly different, declining trajectories of medication adherence (d=−0.41). Conclusion: We found shared co-variance between systems thinking and medication adherence and the SystemCHANGE™ intervention. The SystemCHANGE™ intervention was efficacious in improving and sustaining medication adherence in adult kidney transplant recipients.

Ethnic differences in kidney function in childhood: the Born in Bradford Cohort Renal Study

Background: Endstage kidney failure rates are higher in South Asians than in White Europeans. Low birth weight is associated with adult chronic kidney disease and is more common in South Asians. Foetal kidney size was smaller in South Asians in the Born in Bradford (BiB) birth cohort. As part of BiB follow up, we aimed to investigate if there were ethnic differences in kidney function and blood pressure in early childhood and whether this was different by foetal kidney size. Methods: Serum creatinine, cystatin C, urea, and urinary albumin to creatinine ratio (ACR), protein to creatinine ratio (PCR) and retinol binding protein (RBP) were analysed in blood and urine samples from those who participated in the BiB follow-up at 7-11 years. Ethnicity was categorised by parental self-report as White European and South Asian. Estimated glomerular filtration rate (eGFR) was calculated using Schwartz, and cystatin C Zappitelli and Filler equations. Linear regression was used to examine the association between ethnicity and eGFR, PCR and blood pressure. Results: 1591 children provided blood (n=1403) or urine (n=625) samples. Mean eGFR was 92 ml/min/1.73m2 (standard deviation (SD) 9) using Schwartz (n=1156) and 94 (SD 11) using Zappitelli (n=1257). CKD prevalence was rare (1 with eGFR &lt;60 ml/min/1.73m2, 14 (2.4%) had raised ACR (&gt;2.5 mg/mmol in boys/3.5 mg/mmol in girls). Diastolic blood pressure was higher in South Asian children (difference 2.04 mmHg, 95% CI 0.99 to 3.10) but was not significant in adjusted analysis. There was no evidence of association in adjusted models between ethnicity and any eGFR or urinary measure at this age. Conclusions: There was no evidence of significant ethnic differences in kidney function at pre-pubertal age despite differences in kidney volume at birth. Longitudinal follow-up is required to track ethnic patterns in kidney function and blood pressure as children develop through puberty.

Characterization of the Cellular Origin and Oncogenic Mechanisms of Chromophobe Renal Cell Carcinoma (ChRCC) and Renal Oncocytic Neoplasms

Abstract Background ChRCC is a rare form of kidney cancer and presents with a poor prognosis in the metastatic setting, with limited response to immune checkpoint inhibitors (ICI) and targeted therapy. While previous studies suggested that ChRCC originates from intercalated cells of the kidney, its exact cellular origin has not been clearly defined. We therefore investigated the cellular origin of ChRCC and renal oncocytic neoplasms at single-cell resolution. Methods ChRCC, renal oncocytoma (RO) and low-grade oncocytic tumor (LOT) samples with matched normal kidney specimens were analyzed using single-cell RNA sequencing (scRNA-seq). Epithelial cells from normal samples were clustered and annotated into the distinct known cellular types found in the adult healthy human kidney. A logistic regression model (Young M.D. et al., Science, 2018) was trained on the normal epithelial clusters, using a comprehensive set of 74 marker genes (features). Subsequently, the model was tested on tumor clusters from ChRCC, RO and LOT to investigate their cellular origin through the identification of the highest predicted probabilities of similarity between normal epithelial cellular types and tumor cells. Differential gene expression and pathway analyses between ChRCC and its cell of origin were then conducted to investigate mechanisms of oncogenesis. Results Following quality-control, 46,817 cells from 5 tumors (ChRCC: n=3, RO: n=1 and LOT: n=1) and 4 normal samples were isolated for scRNA-seq analysis. Among normal samples, 784 epithelial cells were clustered and annotated into the following cellular entities: proximal tubule (PT), loop of Henle – distal tubule (LOH-DT), principal cells (PC), α-intercalated cells (ICA) and β-intercalated cells (ICB). Across all ChRCC and oncocytic tumors, 7,573 tumor cells were identified, among which 7,425 corresponded to ChRCC. For ChRCC, RO, and LOT neoplasms, the highest predicted probability of similarity was consistently identified with ICA cells (ranging from 0.60 to 0.80). This finding was validated using an external and previously published (Zhang Y. et al., Proc Natl Acad Sci USA, 2021) scRNA-seq dataset from a patient with ChRCC (n=2,853 cells). Additionally, evaluation of previously defined ChRCC-specific markers (i.e. FOXI1, RHCG, KIT, CLCNKA, and CLCNKB) in scRNA-seq data of normal kidney epithelial cells consistently showed the highest expression in ICA cells. Differential gene expression between ChRCC and ICA cells revealed a significant downregulation of MHC class I genes (i.e. HLA-A , HLA-B, and HLA-C) and HSP70 (family A) genes (i.e. HSPA1A, HSPA1B, HSPA6, and HSPA8) in ChRCC. Differential pathway analysis between ChRCC and ICA cells showed a significant enrichment of the ferroptosis, glutathione metabolism, mTOR signaling and IL-15 pathways in ChRCC. Conclusions Renal oncocytic tumors, including ChRCC, appear to originate from the α-intercalated cells of the normal human kidney. As compared to α-intercalated cells, ChRCC downregulates MHC class I genes, which may be associated with its poor response to immunotherapy. Further, the selective downregulation of HSP70 genes may in part explain ChRCC’s increased sensitivity to ferroptosis. CDMRP DOD Funding: yes

Spatial proteomics enables identification of prognostic biomarkers in papillary renal cell carcinoma

Abstract Background Papillary renal cell carcinoma (PRCC) is the second most common adult kidney cancer histology, constituting 15-20% of cases. While some patients may have indolent PRCC tumors that grow slowly, other tumors rapidly metastasize. Some PRCC tumors respond to immune checkpoint inhibitors. Thus, understanding the immune tumor microenvironment and how it correlates with patient outcomes in this relatively rare disease is a critical need. Spatial interrogation of patient samples has the potential to offer novel insights into the tumor-immune axis and provide avenues for enhanced diagnosis and treatment. Addressing questions of spatial arrangement within tumors has remained a technical and biological challenge, but emerging spatial biology technologies provide molecular data at single cell resolution. We hypothesized that the spatial interaction of immune, stromal and tumor cells would be prognostic for PRCC patients. Methods A tissue microarray was assembled from an archive of ~100 patients presenting with PRCC. This dataset was assayed with PhenoCycler/CODEX (Akoya Biosciences) using a 31-antibody panel with immune- and cancer-related proteins. We have developed methodology and novel algorithms to perform signal normalization, cell segmentation, and cell typing. We computed neighborhoods for each of 2.5 million cells and performed network analysis to identify spatial clusters. This method allowed us to identify clusters consistently present across multiple TMA spots from the same patient and across multiple patients. Results Using spatial neighborhood analysis, we have identified diverse spatial clusters of potential clinical relevance, including five distinct M2 macrophage spatial clusters. We have described one of the clusters as being physically associated with helper T cells, which is visualized on a PRCC spot and shows co-occurence of M2-macrophages (CD163) and helper T cells (CD4). This pattern was replicated in additional TMA spots from the same patient. In contrast, other clusters of M2-macrophages (M2-M2 spatial cluster and M2-M1 macrophages) are visualized to show vastly different cellular neighborhoods. Clinical associations show that the patients with presence of the M2-T helper cluster have a poor cancer-associated survival (p=0.005). In comparison, the total proportion of M2 macrophages is not associated with survival (p=0.4), highlighting the importance of characterizing spatial interactions beyond cell type quantitation. Conclusions In summary, we highlight the utility of spatial biology to explain the heterogeneity in patients’ tumors and to uncover novel correlates of clinical phenotypes, establishing a platform for future discovery in this field and the identification of additional spatial correlates of patient outcome and clinical response. CDMRP DOD Funding: yes

Adult survivors of childhood-onset steroid-dependent and steroid-resistant nephrotic syndrome treated with cyclosporine: a long-term single-center experience.

Although evidence has confirmed that cyclosporine (CS) is efficacious against childhood-onset steroid-dependent and steroid-resistant nephrotic syndrome (SD/SRNS), some patients may continue to relapse during adulthood. However, predictive factors for adult active disease and kidney complications, such as chronic kidney disease (CKD) and hypertension, in this cohort remain unknown. We conducted a retrospective study on the long-term outcomes of 81 young adults with childhood-onset SD/SRNS treated with CS. The primary endpoint was the probability of active disease into adulthood. The secondary endpoint was the probability of developing kidney complications. At the last follow-up (median age, 23.2 years; median disease duration, 15.8 years), 44 adult patients (54%) continued to have active disease, whereas 16 patients developed CKD or hypertension, respectively. The proportion of patients developing kidney complications was similar between the active disease and long-term remission groups. Young age at NS onset and history of relapse during the initial CS (median, 31 months) were independent predictive factors for active disease. Acute kidney injury at NS onset, focal segmental glomerulosclerosis, and irreversible CS nephrotoxicity were identified as risk factors for the development of CKD, whereas older age was identified as a risk factor for the development of CKD and hypertension. More than 50% of adult survivors treated with CS continued to have active disease, and each 20% developed CKD or hypertension. A long-term follow-up is necessary for patients with SD/SRNS to identify the development of kidney complications later in adulthood that can be attributed to prior disease and CS treatment in childhood, irrespective of disease activity. A higher resolution version of the Graphical abstract is available as Supplementary information.

Risk for graft loss in pediatric and young adult kidney transplant recipients due to recurrent IgA nephropathy

IgA nephropathy (IgAN) is associated with a risk for posttransplant recurrence. Data are limited regarding graft loss attributable to recurrence of IgAN among pediatric and young adult kidney transplant (KT) recipients. This was a retrospective cohort study of patients aged 0 to 25 years from the Scientific Registry of Transplant Recipients who received a primary KT for IgAN. Patients with history of KT attributable to renal dysplasia were comparators. Outcomes included the incidence of graft loss attributable to IgAN recurrence, association with donor type, and posttransplant corticosteroid use. In total, 5475 transplant recipients were included, with 1915 patients with IgAN and 3560 patients with renal dysplasia. In a multivariable Cox proportional hazards model, IgAN was associated with higher risk of graft loss (adjusted hazard ratio [aHR], 1.35; 95% CI, 1.21-1.50; P < .001) compared with dysplasia. Graft loss was attributed to recurrent disease in 5.4% of patients with IgAN. In a multivariable competing risks analysis, patients with IgAN receiving a parental living-donor kidney were more likely to report graft loss from recurrent disease compared with patients with a nonparental living donor (aHR, 0.52; 95% CI, 0.31-0.91; P = .02). Posttransplant prednisone use was not associated with improved graft survival (P = .2). These data challenge existing paradigms in posttransplant management of patients with IgAN.

Pregnancy after deceased donor vs living donor kidney transplant: associated obstetric and graft outcomes

Outside of pregnancy, recipients of a deceased donor kidney transplant experience worse graft and overall survival compared with recipients of a living donor kidney transplant. In pregnancy, it is unknown whether the type of donor graft modifies either graft health in the peripartum period or pregnancy outcomes. This study aimed to define characteristics and outcomes in pregnancy based on donor type in kidney transplant recipients. This was a retrospective cohort study of adult kidney transplant recipients who received their graft between 2000 and 2019 with a subsequent pregnancy enrolled in the Transplant Pregnancy Registry International. The primary outcome was graft loss within 2 years of delivery. The secondary outcomes included severe maternal morbidity and neonatal composite morbidity. Univariate, multivariable logistic regression, and Cox proportional-hazards models were constructed for statistical analysis, with recipients of a living unrelated donor as the referent. Overall, 638 pregnant patients after kidney transplant had pregnancy outcomes that met our inclusion criteria. Of these patients, 168 (26.3%) received a graft from a deceased donor, 310 (48.6%) received a graft from a living related donor, and 160 (25.1%) received a graft from a living unrelated donor. Recipients of a deceased donor were more likely to be nulliparous, have an unplanned pregnancy, and self-identify as non-White. Moreover, recipients of a deceased donor were more likely to experience urinary tract infections (deceased donor: 21.8%; living related donor: 10.1%; living unrelated donor: 20.6%; P=.018). Severe maternal morbidity (deceased donor: 3.4%; living related donor: 2.8%; living unrelated donor: 7.2%) and neonatal composite morbidity (deceased donor: 8.4%; living related donor: 17.1%; living unrelated donor: 14.4%) did not differ by donor type. Deceased donor transplant was associated with graft loss within 2 years of delivery (deceased donor: 6.7%; living related donor: 3.7%; living unrelated donor: 1.3%; adjusted odds ratio, 7.52; 95% confidence interval, 1.53-60.8) and long-term graft loss from transplant (adjusted hazard ratio, 2.08; 95% confidence interval, 1.10-3.95). Although our study demonstrated an association between deceased donor transplant and graft loss after pregnancy, it did not provide evidence that pregnancy itself causes graft loss. Recipients of a deceased donor kidney transplant should not be discouraged from pursuing pregnancy based on their donor type, but these patients should undergo preconception counseling with a discussion of their individualized obstetrical and graft risks, close intrapartum monitoring for infection and hypertensive disease, and continued surveillance for at least 2 years after delivery with a multidisciplinary obstetrics and transplant team.

Abstract PR008: The SLC1A1/EAAT3 dicarboxylic amino acid transporter: An actionable, HIF-independent, hub that links epigenetic dysregulation to nucleotide metabolism in kidney cancer

Abstract Significance: The clear cell renal cell carcinomas (ccRCCs), which harbor the hallmark inactivation of the von Hippel Lindau tumor suppressor protein (pVHL), represent the majority of adult kidney cancers. Although, early stage/localized ccRCC is effectively managed by surgery and surveillance, therapeutic options for advanced stage disease are limited, highlighting the unmet need for novel therapies. Chromatin dysregulation is routinely observed in ccRCC and our previous work identified a distinct histone modification signature associated with pVHL-deficient ccRCCs, versus the pVHL-proficient chromophobe and papillary sub-types, which included elevated levels of bulk Histone H3 K27 acetylation (H3K27ac). H3K27ac marks transcriptionally activated regions in the genome. We hypothesized that, as in other biological contexts, H3K27ac accumulation in pVHL-deficient ccRCCs drives the expression of key oncogenes. Here, we functionally probed this dysregulated epigenetic program to identify actionable targets in kidney cancer. Experimental Approach and Results: We identified genes marked by elevated H3K27ac (ChIP-Seq) and higher expression (RNA-Seq), specifically in pVHL-deficient cells and prioritized the top 100 genes that encoded druggable products. Using a library representing these ORFs, we did an in vivo ‘sufficiency’ screen, to identify candidates whose expression promoted tumor growth in otherwise poorly tumorigenic pVHL-proficient cells. Our screen (and downstream validation studies) identified SLC1A1, which encodes an Asp/Glu transporter named EAAT3, as an oncogenic driver in ccRCC. Results: SLC1A1 expression was elevated in pVHL-deficient cells – but in a HIF-independent manner. Inactivation of SLC1A1 (using CRISPR/Cas9) led to fitness defects in a panel of ccRCC cell lines, along with a notable depletion of nucleotide biosynthesis precursors, likely because of the importance of the Asp carbon skeleton in this pathway. Consistent with this, esterified-Asp rescued the fitness defects associated with SLC1A1 loss. Moreover, SLC1A1 upregulation (high Asp/Glu) diminished dependency on Glutaminase; whereas, SLC1A1 loss (low Asp/Glu) increased Glutaminase dependency and promoted sensitivity to Glutaminase blockade. Finally, using clinical cohorts and cell-based studies, we found that SLC1A1 can impact its own transcriptional expression, but also the expression of certain other metabolic transporters involved in Asp/Glu metabolism (e.g. SLC22A11) and nucleotide metabolism (e.g SLC28A1). We speculate, these transcriptional alterations are driven by the conversion of Glu into a-ketoglutarate, a key cofactor for KDMs. Our ongoing studies are addressing the mechanistic basis of this transcriptional regulation and exploring the feasibility of pharmacologically targeting SLC1A1 in ccRCC. Altogether, we show that ccRCCs hijack nutrient reabsorption mechanisms (e.g. SLC1A1) to drive oncogenic programs. SLC1A1 thus links epigenetic dysregulation to a HIF-independent metabolic program regulating nucleotide biosynthesis/uptake. Citation Format: Abhishek A. Chakraborty. The SLC1A1/EAAT3 dicarboxylic amino acid transporter: An actionable, HIF-independent, hub that links epigenetic dysregulation to nucleotide metabolism in kidney cancer [abstract]. In: Proceedings of the AACR Special Conference: Advances in Kidney Cancer Research; 2023 Jun 24-27; Austin, Texas. Philadelphia (PA): AACR; Cancer Res 2023;83(16 Suppl):Abstract nr PR008.

Basigin is released in extracellular vesicles derived from the renal tubular epithelium in response to albuminuria.

Irrespective of the cause, albumin/proteinuria induces tubulointerstitial damage and accelerates the progression of kidney diseases. Our series of studies demonstrated that proteinuria, an independent prognostic factor for chronic kidney disease (CKD), is correlated with urinary basigin/CD147 (Bsg) levels. We examined the morphology and origin of Bsg in the tubular lumen through the effects of filtered glucose and protein solutes on the tubules. Diabetic kidney disease (DKD) patients (N = 50) were treated with spironolactone 25 mg for 4 weeks or by conservative treatment. The associations between urinary Bsg values and clinical indicators were examined. Primary-cultured proximal tubular epithelial cells (PTECs) from human adult kidneys were exposed to high glucose or bovine serum albumin (BSA). In patients with early phase DKD, urinary Bsg levels were closely correlated with proteinuria but not HbA1c. Full-length Bsg on extracellular vesicles (EVs) was investigated primarily in urine collected from DKD patients. EVs obtained from the urine of DKD patients included Bsg and SGLT2 proteins. Notably, spironolactone treatment concomitantly suppressed the release of Bsg-bearing EVs in correlation with decreased albuminuria. Exposure of PTECs to BSA (but not high glucose) enhanced the storage of supernatant Bsg in EVs despite the absence of exposure-specific changes in Bsg transcription. Proteinuria induces the release of Bsg-bearing EVs derived from PTECs into the tubular lumen.

ELABELA/APJ Axis Prevents Diabetic Glomerular Endothelial Injury by Regulating AMPK/NLRP3 Pathway

ELABELA (ELA), a recently discovered peptide, is highly expressed in adult kidneys and the endothelium system. It has been identified as a novel endogenous ligand for the apelin receptor (APJ). This study aims to investigate the role of ELA in diabetic glomerular endothelial pyroptosis and its underlying mechanism. Initially, a significant decrease in ELA mRNA levels was observed in the renal cortex of db/db mice and high glucose–treated glomerular endothelial cells (GECs). It was also found that ELA deficiency in ELA+/− mice significantly accelerated diabetic glomerular injury, as shown by exacerbated glomerular morphological damage, increased serum creatine and blood urea nitrogen, and elevated 24-h urinary albumin excretion. In addition, in vivo overexpression of ELA prevented diabetic glomerular injury, reduced von Willebrand factor expression, restored endothelial marker CD31 expression, and attenuated the production of adhesive molecules such as intercellular adhesion molecule-1 and vascular cell adhesion molecule-1. Furthermore, in vitro studies confirmed that treatment with ELA inhibited GEC injury by regulating the NOD-like receptor protein 3 (NLRP3) inflammasome, as indicated by blocking NLRP3 inflammasome formation, decreasing cleaved Caspase-1 production, and inhibiting interleukin-1β and interleukin-18 production. Moreover, in vitro experiments demonstrated that the protective effects of ELA in GECs during hyperglycemia were diminished by inhibiting adenosine monophosphate–activated protein kinase (AMPK) using Compound C or by APJ deficiency. Taken together, this study provides the first evidence that ELA treatment could prevent diabetic glomerular endothelial injury, which is partly mediated by the regulation of the AMPK/NLRP3 signaling pathway. Therefore, pharmacologically targeting ELA may serve as a novel therapeutic strategy for diabetic kidney disease.

Adhesion GPCR Gpr126 (Adgrg6) Expression Profiling in Zebrafish, Mouse, and Human Kidney.

Adhesion G protein-coupled receptors (aGPCRs) comprise the second-largest class of GPCRs, the most common target for approved pharmacological therapies. aGPCRs play an important role in development and disease and have recently been associated with the kidney. Several aGPCRs are expressed in the kidney and some aGPCRs are either required for kidney development or their expression level is altered in diseased kidneys. Yet, general aGPCR function and their physiological role in the kidney are poorly understood. Here, we characterize in detail Gpr126 (Adgrg6) expression based on RNAscope® technology in zebrafish, mice, and humans during kidney development in adults. Gpr126 expression is enriched in the epithelial linage during nephrogenesis and persists in the adult kidney in parietal epithelial cells, collecting ducts, and urothelium. Single-cell RNAseq analysis shows that gpr126 expression is detected in zebrafish in a distinct ionocyte sub-population. It is co-detected selectively with slc9a3.2, slc4a4a, and trpv6, known to be involved in apical acid secretion, buffering blood or intracellular pH, and to maintain high cytoplasmic Ca2+ concentration, respectively. Furthermore, gpr126-expressing cells were enriched in the expression of potassium transporter kcnj1a.1 and gcm2, which regulate the expression of a calcium sensor receptor. Notably, the expression patterns of Trpv6, Kcnj1a.1, and Gpr126 in mouse kidneys are highly similar. Collectively, our approach permits a detailed insight into the spatio-temporal expression of Gpr126 and provides a basis to elucidate a possible role of Gpr126 in kidney physiology.

Innervation of the developing kidney in vivo and in vitro.

Within the adult kidney, renal neurites can be observed alongside the arteries where they play a role in regulating blood flow. However, their role and localization during development has so far not been described in detail. In other tissues, such as the skin of developing limb buds, neurons play an important role during arterial differentiation. Here, we aim to investigate whether renal nerves could potentially carry out a similar role during arterial development in the mouse kidney. In order to do so, we used whole-mount immunofluorescence staining to identify whether the timing of neuronal innervation correlates with the recruitment of arterial smooth muscle cells. Our results show that neurites innervate the kidney between day 13.5 and 14.5 of development, arriving after the recruitment of smooth muscle actin-positive cells to the renal arteries.