Chronic Allograft Injury Research Articles

Renal Allograft Macrophage Infiltration in Antibody-Mediated Renal Allograft Rejection

Abstract Introduction/Objective Macrophages are involved in the pathogenesis and contribute to acute and chronic renal allograft injury. We evaluated CD163+ (M2) macrophage graft tissue infiltration and its correlation with clinical and histological prognostic factors. Urinary soluble CD163, circulating total, and monocyte-derived microparticles (MMPs) in plasma were also estimated and correlated with tissue M2 macrophage infiltration. Methods/Case Report The study included forty-five renal allograft recipients with for-cause graft biopsy, with Antibody-mediated Rejection (ABMR) (n=30) or no evidence of rejection (NER) (n=15), from Jan 2021-Dec 2023, along with fifteen age-matched healthy controls (HC). On immunohistochemistry, CD163 positive cells were counted in glomeruli and tubulointerstitium. Urinary sCD163 was done by ELISA. Flow cytometry quantified plasma MPs (AnnexinV+) and MMPs (CD14+/ AnnexinV+). Results (if a Case Study enter NA) The mean age of renal allograft recipients was 35±9yrs (all males). Mean s.creatinine in ABMR and NER was 3±2.6 and 2±0.5 mg/dl, respectively. ABMR had significantly more glomerular (16.2±13.7/10 glomeruli) and tubulointerstitial (183±108/10hpf) M2 macrophage (CD163+) cell infiltration than NER (4.8±4.7/10 glomeruli; 133.5±108/10hpf). Urinary sCD163 in ABMR was also significantly raised (0.89±0.63ng/ml) than in NER. It was not detectable in HC. Plasma MMPs were elevated in ABMR [25% of total MPs (1.62x104)] as compared to NER [8.2 % of total MPs (1.4x104)] and HC [7.8% of total MPs (1.2x104)]. In ABMR, the glomerular CD163+ cells correlated with urinary sCD163 levels (r=0.350, p=0.050) and circulating MMPs (r=0.526, p=0.002). Conclusion We found that in renal allograft recipients with ABMR, there is significantly higher graft biopsy glomerular CD163+ (M2) macrophage infiltration and elevated urinary sCD163 levels as compared to NER. The plasma circulating MMPs were also elevated in ABMR. Our findings suggest that monocyte activation plays a significant role in the pathogenesis and injury in ABMR. Non-invasive markers of monocyte activation can distinguish ABMR from NER in allograft recipients presenting with allograft dysfunction.

The Angiotensin Type 1 Receptor: A Drug Target to Reduce the Risk of Organ Transplant Rejection

: Allograft rejection is one of the main problems that must be overcome. Evidence suggests a role of the local renin-angiotensin system (RAS) in the progress of chronic allograft injury. Angiotensin II, generated by the renin-angiotensin system, is well-known as a major regulator molecule to control the blood pressure and fluid system. Evidence suggests that this bioactive molecule and its receptor increase the risk of tissue injuries and organ transplant rejection through different molecular mechanisms such as activation of innate and cellular immunity, upregulation of inflammatory pathways, and accumulation of extracellular matrix by expression pro-fibrotic molecules like transforming growth factor β (TGF-β) to increase the risk of fibrosis. Based on these findings, AT1R antagonists might have therapeutic potential to prevent the risk of tissue injuries and allograft rejection by regulating immune response, inflammation pathway, and fibrogenesis to improve organ functions.

Using MRI Texture Analysis Machine Learning Models to Assess Graft Interstitial Fibrosis and Tubular Atrophy in Patients with Transplanted Kidneys

Objective: Interstitial fibrosis/tubular atrophy (IFTA) is a common, irreversible, and progressive form of chronic kidney allograft injury, and it is considered a critical predictor of kidney allograft outcomes. The extent of IFTA is estimated through a graft biopsy, while a non-invasive test is lacking. The aim of this study was to evaluate the feasibility and accuracy of an MRI radiomic-based machine learning (ML) algorithm to estimate the degree of IFTA in a cohort of transplanted patients. Approach: Patients who underwent MRI and renal biopsy within a 6-month interval from 1 January 2012 to 1 March 2021 were included. Stable MRI sequences were selected, and renal parenchyma, renal cortex and medulla were segmented. After image filtering and pre-processing, we computed radiomic features that were subsequently selected through a LASSO algorithm for their highest correlation with the outcome and lowest intercorrelation. Selected features and relevant patients’ clinical data were used to produce ML algorithms using 70% of the study cases for feature selection, model training and validation with a 10-fold cross-validation, and 30% for model testing. Performances were evaluated using AUC with 95% confidence interval. Main results: A total of 70 coupled tests (63 patients, 35.4% females, mean age 52.2 years) were included and subdivided into a wider cohort of 50 for training and a smaller cohort of 20 for testing. For IFTA ≥ 25%, the AUCs in test cohort were 0.60, 0.59, and 0.54 for radiomic features only, clinical variables only, and a combined radiomic–clinical model, respectively. For IFTA ≥ 50%, the AUCs in training cohort were 0.89, 0.84, and 0.96, and in the test cohort, they were 0.82, 0.83, and 0.86, for radiomic features only, clinical variables only, and the combined radiomic–clinical model, respectively. Significance: An ML-based MRI radiomic algorithm showed promising discrimination capacity for IFTA > 50%, especially when combined with clinical variables. These results need to be confirmed in larger cohorts.

Role of Shear Wave Elastography for Assessment of Renal-Allograft Fibrosis and its Correlation With Histopathology.

To investigate whether shear wave elastography (SWE) can accurately identify interstitial fibrosis and tubular atrophy (IFTA) in chronic renal allograft injury (CRAI) and whether it can differentiate between different grades of IFTA. Prospective observational study on renal transplant recipients who presented with CRAI. Patient selection was done on the basis of clinical presentation, serum creatinine, and eGFR levels. Biopsy and SWE were performed and SWE values were correlated with histopathological findings according to Banff schema. Receiver operating characteristic (ROC) was also analyzed to assess the diagnostic efficacy of SWE. Sxity-one patients were evaluated. Ten patients had no IFTA, 33 patients had mild IFTA, 16 patients had moderate IFTA, and 2 patients had severe IFTA. Mean parenchymal stiffness values in no IFTA, mild IFTA, moderate IFTA and severe IFTA were 39.86 ± 2.17 kPa (3.64 ± 0.09 m/s), 41.59 ± 3.36 kPa (3.71 ± 0.15 m/s), 47.59 ± 3.34 kPa (3.98 ± 0.14 m/s), and 53.83 ± 1.41 kPa (4.25 ± 0.03 m/s), respectively. SWE values of parenchymal stiffness reached statistical significance to differentiate between mild, moderate, and severe IFTA. ROC analysis revealed cut-off values of 45.09 kPa (3.89 m/s) to differentiate between mild IFTA and moderate IFTA, 52.06 kPa (4.18 m/s) to differentiate between moderate IFTA and severe IFTA with acceptable sensitivity and specificity. SWE is a non-invasive and cost-effective imaging tool to evaluate the disease status of renal allografts affected by CRAI. Thus, it can be of paramount importance if added to the regular follow-up imaging protocol of renal allograft along with grayscale and Doppler imaging.

The effect of primary renal disease upon outcomes after renal transplant.

This study investigated whether nature of primary renal disease affects clinical outcomes after renal transplantation at a single center in the United Kingdom. This was a retrospective cohort study of 961 renal transplant recipientsfollowed up at a large renal center from 2000 to 2020. Separation of diseases responsible for end-stage kidney disease included glomerulonephritis, diabetic kidney disease, hypertensive nephropathy, autosomal dominant polycystic kidney disease, unknown cause, other causes and chronic pyelonephritis. Outcome data included graft loss, cardiovascular events, malignancy, post-transplant diabetes mellitus and death, analyzed according to primary disease type. The mean age at transplantation was 47.3 years. During a mean follow-up of 7.6 years, 18% of the overall cohort died corresponding to an annualised mortality rate of 2.3%. Death with a functioning graft occurredat a rate of 2.1% per annum, with the highest incidence observed in in patients with diabetic kidney disease (4.1%/year). Post-transplant cardiovascular events occurred in 21% of recipients(2.8% per year), again highest in recipients with diabetic kidney disease (5.1%/year) and hypertensive nephropathy (4.5%/year). Post-transplant diabetes mellitus manifested in 19% of the cohort at an annualized rate of2.1% while cancer incidence stood at 9% with an annualized rate of 1.1% . Graft loss occurred in 6.8% of recipients at the rate of1.2% per year with chronic allograft injury, acute rejection and recurrent glomerulonephritis being the predominant causative factors. Median + IQR dialysis-free survival of the whole cohort was 16.2 (9.9 ->20) years, being shortest for diabetic kidney disease (11.0 years) and greatest for autosomal dominant polycystic kidney disease (18.2 years) .The collective mean decline in eGFR over time was -1.14ml/min/year. Recipients with Pre-transplant diabetic kidney disease exhibited the fastest rate of decline(-2.1ml/min/year) a statistically significant difference in comparison to the other native kidney diseases with Autosomal dominant polycystic kidney disease exhibiting the lowest rate of decline(-0.05ml/min/year) CONCLUSION: Primary renal disease can influence the outcome after renal transplantation, with patients with prior diabetic kidney disease having the poorest outcome in terms of dialysis-free survival and loss of transplant function. Autosomal polycystic kidney disease, other cause and unknown cause had the best outcomes compared to other primary renal disease groups.

HCK induces macrophage activation to promote renal inflammation and fibrosis via suppression of autophagy

Renal inflammation and fibrosis are the common pathways leading to progressive chronic kidney disease (CKD). We previously identified hematopoietic cell kinase (HCK) as upregulated in human chronic allograft injury promoting kidney fibrosis; however, the cellular source and molecular mechanisms are unclear. Here, using immunostaining and single cell sequencing data, we show that HCK expression is highly enriched in pro-inflammatory macrophages in diseased kidneys. HCK-knockout (KO) or HCK-inhibitor decreases macrophage M1-like pro-inflammatory polarization, proliferation, and migration in RAW264.7 cells and bone marrow-derived macrophages (BMDM). We identify an interaction between HCK and ATG2A and CBL, two autophagy-related proteins, inhibiting autophagy flux in macrophages. In vivo, both global or myeloid cell specific HCK-KO attenuates renal inflammation and fibrosis with reduces macrophage numbers, pro-inflammatory polarization and migration into unilateral ureteral obstruction (UUO) kidneys and unilateral ischemia reperfusion injury (IRI) models. Finally, we developed a selective boron containing HCK inhibitor which can reduce macrophage pro-inflammatory activity, proliferation, and migration in vitro, and attenuate kidney fibrosis in the UUO mice. The current study elucidates mechanisms downstream of HCK regulating macrophage activation and polarization via autophagy in CKD and identifies that selective HCK inhibitors could be potentially developed as a new therapy for renal fibrosis.

Amelioration of Fibrotic Remodeling of Human 3-Dimensional Full-Thickness Skin by Transglutamase 2 Inhibition.

Fibrotic tissues are characterized by excessive crosslinking between extracellular matrix (ECM) proteins, rendering them more resistant to degradation. Although increased crosslinking of ECM is thought to play an important role for progression of tissue fibrosis, enhanced ECM crosslinking has not yet been targeted therapeutically in systemic sclerosis (SSc). Here, we investigated the role of transglutaminase 2 (TG2), a central crosslinking enzyme, in the activation of SSc fibroblasts. We assessed TG2 expression and activity using TG2 staining, Western blotting, and TG2 activity assays. We inhibited TG2 in fibroblasts cultured under standard 2-dimensional conditions and in a 3-dimensional full-thickness equivalent skin model using monoclonal inhibitory anti-TG2 antibodies. TG2 expression was increased in the skin of patients with SSc compared with healthy controls, with levels particularly high in patients with SSc-associated interstitial lung disease. TG2 expression and TG2 activity were also increased in SSc dermal fibroblasts. Moreover, the levels of circulating TG2 in the plasma samples from SSc patients were increased versus samples from healthy controls. Anti-TG2 antibodies did not show consistent antifibrotic effects across different fibroblast cell lines under 2-dimensional culture conditions; however, anti-TG2 antibodies effectively reduced transforming growth factor β-induced dermal thickening, myofibroblast differentiation, and collagen accumulation in the 3-dimensional full-thickness model of human skin. We provide the first evidence, to our knowledge, that inhibition of TG2 might be a potential antifibrotic approach in SSc. Our findings have translational potential as anti-TG2 antibodies are currently evaluated in a phase II clinical trial in chronic allograft injury and would thus be available for clinical studies in SSc (ClinicalTrials.gov identifier: NCT04335578).

#5790 IMPAIRED FATTY ACID METABOLISM PERPETUATES LIPOTOXICITY ALONG THE TRANSITION TO CHRONIC KIDNEY INJURY

Abstract Background and Aims Understanding the cell-intrinsic mechanisms contributing to the maintenance of a dysfunctional cellular state in chronic kidney disease (CKD) and identifying therapeutic targets are research priorities in renal medicine. A key contributor to chronic kidney histological damage is acute kidney injury, especially ischemia-reperfusion injury (IRI). Persistent cell-extrinsic perturbations generated upon IRI, for example hypoxia, impair the energetic metabolism of Proximal Tubular Cells (PTC) participating in the process of transition from acute to chronic kidney injury. Here, we propose to investigate the PTC intrinsic factors involved in the perpetuation of an impaired cellular state which contribute to CKD progression Method We combined single nucleus transcriptomic, metabolomic and lipidomic approaches in experimental models and patient cohorts to investigate the molecular bases of the progression to chronic kidney allograft injury initiated by IRI. Results The urinary metabolome of kidney transplant recipients with chronic allograft injury and who experienced severe IRI was significantly enriched with long chain fatty acids (FA). We identified a renal FA-related gene signature with low levels of Cpt2 and Acsm5 and high levels of Acsl4 and Acsm5 associated with IRI, transition to chronic injury, and established CKD in mouse models and kidney transplant recipients. The findings were consistent with the presence of Cpt2-, Acsl4+, Acsl5+, Acsm5- PTC failing to recover from IRI as identified by single nucleus RNA sequencing. In vitro experiments indicated that endoplasmic reticulum (ER) stress contributes to CPT2 repression, which, in turn, promotes lipids accumulation, drives profibrogenic epithelial phenotypic changes, and activates the unfolded protein response. Conclusion ER stress through CPT2 inhibition and lipid accumulation, engages an auto-amplification loop leading to lipotoxicity and self-sustained cellular stress. Thus, IRI imprints a persistent FA metabolism disturbance in the proximal tubule sustaining the progression to chronic kidney allograft injury.

#5095 THE CURIOUS CASE OF GAS IN THE GRAFT KIDNEY

Abstract Background and Aims Emphysematous pyelonephritis (EPN) denotes a severe infection of renal parenchyma resulting in necrosis and gas accumulation in the renal and perirenal tissue. Risk factors for urinary tract infections in renal transplant recipients include advanced age, female gender, reflux nephropathy prior to transplantation, diabetes mellitus, deceased donor kidney, kidney–pancreas transplant, retransplantation, antibody induction for immunosuppression, urinary bladder catheterisation, history of allograft rejection with subsequent escalation of immunosuppressive therapy and use of ureteral stents. There are no definite guidelines for management of EPN in renal allografts. If unstable and deteriorating, graft nephrectomy should be undertaken as soon as possible. Any delay in surgical intervention, be it percutaneous drainage or nephrectomy may result in death. Method A 25-year old male, diagnosed with IgA Nephropathy (IgAN) received a living donor renal transplant from his mother in 2013 after a dialysis vintage of 3 years. He received Basiliximab induction followed by maintenance immunosuppression with Tacrolimus, Mycophenolate mofetil and Prednisolone. He had no history of UTI in the immediate post-transplant period. His blood glucose levels were within normal limits and he had not had any urological intervention. In 2019, patient was diagnosed with IgAN recurrence as a cause of chronic renal allograft injury. His Creatinine at last follow up in July 2022 was 4.1 mg/dL. He presented in September 2022 with fever, chills, vomiting, pain in the right iliac fossa and inability to extend his right leg. At presentation, his BP was 86/60mmHg, with pyrexia and tachycardia. Ultrasonography revealed an ill-defined collection superomedial to the graft kidney with doubtful posterior extension and air foci. Non-contrast CT study revealed a large subcapsular collection, extending posteriorly into the right iliac fossa involving the right psoas major and inferiorly into the pelvis, with air foci and no evidence of any urinary tract obstruction suggestive of Acute Emphysematous pyelonephritis with ruptured abscess. He was started on broad-spectrum iv antibiotics- Meropenem and Levofloxacin. Immunosuppression was reduced. Laboratory investigations revealed total leucocyte count of 37,000 cells/mm3, Creatinine of 11 mg/dL, urine routine microscopy revealed field full of pus cells. Blood and urine cultures grew ESBL Escherichia coli. He was taken up for urgent urological intervention in the form of percutaneous drain insertion. Frank pus was aspirated and 200mL drained instantaneously, cultures of which demonstrated the same organism. Within 24 hours of pus drainage, patient became afebrile and had pain relief. He was given 3 weeks of culture-appropriate iv antibiotics, to continue another 3 weeks of oral Carbapenem. However, his graft dysfunction persisted, with no recovery and he became dialysis-dependent. Discussion EPN of the renal allograft is a rare occurrence. A study of EPN in renal transplant recipients by Alexander et al from 2012 revealed 18 out of 22 patients were diabetics, 9 necessitated graft nephrectomy and 7 required percutaneous drainage in addition to antibiotics4. Till date, up to 30 cases of graft EPN have been reported in English literature. The striking feature is that more than 90% of these cases were diabetic. Conclusion The complete pathogenesis of renal allograft EPN, especially in patients with no apparent traditionally described risk factors remains yet to be understood. A high degree of suspicion and early intervention may help to save the allograft.

Macrophage to Myofibroblast Transition in Diastolic Dysfunction Development

Heart failure is the top killer in the U.S and worldwide, often caused by hypertension, aging, or cardiac toxicity. Diastolic Dysfunction (DD), the often the first step of heart failure, occurs when the chambers of the heart are not able to expand during the filling phase. In addition, hypertension is the leading cause of DD. Though this is known, the progression of hypertension into DD remains poorly understood. Of note is the ability of M2 macrophages to differentiate into a myofibroblast-like phenotype, known as macrophage to myofibroblast transition (MMT). This transition has been observed in interstitial fibrosis in chronic renal allograft injury. The researchers noted that MMT account for 50% of the myofibroblast population. To our knowledge, the extent of fibrotic remodeling due to MMT in the heart has not been ardently investigated. Therefore, we aim to answer whether MMT plays a causal role in the progression of hypertension to DD and the pathogenesis of heart failure.Utilizing the uninephrectomized, DOCA-salt model, mice were subjected to this treatment and hypertension was induced. As a negative control, another group of mice received a uninephrectomy and the same salt in their drinking water, however, DOCA was not administered (Sham group). MMT prevalence, identified as CD68+ α-SMA+ expressions, was observed inside the hearts of DOCA and Sham mice. The hearts were isolated and homogenized via gentleMACS tissue Dissociator, the monocytes were purified via Percoll isolation, and flow cytometry was used to identify the population of CD68+ α-SMA+ expressing cells.As soon as 10 days post DOCA implantation, the DOCA group exhibited worsening diastolic function as it took longer for the pressure to change in the hearts of DOCA mice than in Sham (-dp/dt). These data were gathered via left ventricular (LV) catheter insertion. At a later time, utilizing a different cohort of mice preliminary data show an increase of monocyte (CD68+) and fibroblast (α-SMA+) double-positive expressing cells in the hearts of hypertensive mice.MMT has been observed in the hearts of hypertensive mice. This transition may exacerbate Diastolic Dysfunction. More research must be performed to investigate the wide variety of functions of macrophages (i.e., M1 to M2 ratio and transition, macrophage residence or infiltration, and macrophage stimulation of myofibroblasts), as well as the specific interactions between macrophages and cardiomyocytes, or other immune cells, that might mediate this transition. These data provide a preliminary, but interesting glimpse, into the role of macrophages in exacerbating Diastolic Dysfunction and mediating Heart Failure. NIH RO1-HL146713 and AHA 15BGIA25730047 (Shengyu Mu) This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

(1186) Donor Derived Cell Free Dna after Lung Transplantation: Marker for Acute and Chronic Lung Allograft Injury?

(1186) Donor Derived Cell Free Dna after Lung Transplantation: Marker for Acute and Chronic Lung Allograft Injury?

Diarrhea after kidney transplantation: A study of risk factors and outcomes.

Diarrhea in kidney transplant recipients (KTRs) can be associated with significant morbidity. We evaluated 198 KTRs for a history of diarrhea post-kidney transplant at a tertiary care center in western India over 1 year. A protocol-based evaluation of diarrhea was done with respect to clinical features, diagnostic evaluation, associated acute allograft dysfunction, and its impact on long-term allograft function. Primary outcomes of interest were: chronic allograft injury (CAI) and the need for mycophenolate mofetil (MMF) withdrawal. We also assessed the effect of MMF withdrawal on the risk of the development of CAI. Eighty-five of 198 (42.5%) recipients experienced diarrhea and a total of 140 diarrheal episodes were evaluated. The mean age of these 85 recipients was 38 ± 12 years and 72 (84.7%) were males. 73 of 85 recipients were on MMF at the time of diarrhea and in 35 (48%) of them MMF withdrawal was needed for chronic and persistent symptoms. Diarrhea was attributed to infective etiologies in 90 of 140 (64.2%) cases. Among the microbiologically confirmed infective diarrheal episodes, giardia and cryptosporidium were the common pathogens in 11/28 (39%) and 6/28 (21.4%) episodes respectively. One hundred and twenty-eight episodes out of 140 (91.4%) episodes were complicated by acute allograft dysfunction. Forty-one of 85 recipients (48.2%) developed chronic allograft injury and 12 (14.1%) developed allograft rejection (acute and/or chronic). Probability of chronic allograft injury was higher in those with MMF withdrawal. Diarrhea post-kidney transplant adversely affects graft function, especially after MMF withdrawal.

Proteomic study on the lymphocytes from pregnant Wistar rat females treated with immunosuppressive regimen.

Kidney transplantation remains the therapeutic option for patients with end-stage kidney disease. Current immunosuppressive regimens are efficient in combating acute kidney rejection. However, insights into chronic kidney allograft injury remains limited. Simultaneously, pregnancy is more common after kidney transplantation than during dialysis treatment. Due to ethical issues, comprehensive studies on the impact of immunosuppressive regimens on pregnancy are challenging. The study aimed to investigate the proteomic status of lymphocytes obtained from pregnant female rats under immunosuppressive treatment. The experiment involved a group of 10 female, pregnant Wistar rats, five of which were treated with tacrolimus, mofetil mycophenolate, and glucocorticosteroids; five were used as control. The lymphocytes were obtained and analyzed with mass spectrometry. Measurements were processed by a database search in the ProteinPilot software with a cutoff of 1% false discovery rate. The outcomes were verified statistically by a t-test (p value < 0.05) regarding proteins up- and downregulation. A total of 2082 proteins were identified in all experiments. Eight hundred five proteins were quantified in an absolute manner in a data-independent acquisition-total protein approach analysis. Ninety-five proteins were recognized as present at different concentrations in analyzed groups and were annotated to intracellular pathways. The proteins involved in nonsense-mediated decay and L13a-mediated translational silencing of ceruloplasmin expression were recognized as downregulated. The set of proteins clinically identified as acute phase proteins was upregulated. Despite the blockade of adaptive cellular immunity, the lymphocytes in the analyzed group reveal sustained proinflammatory status with decreased ability to regulate translation. This potentially affects pregnancy and immunity.

Role of time from transplantation to biopsy in histologic ABMR: A single center report.

Allograft biopsies with lesions of Antibody-Mediated Rejection (ABMR) with Microvascular Inflammation (MVI) have shown heterogeneous etiologies and outcomes. To examine factors associated with outcomes in biopsies that meet histologic ABMR criteria, we retrospectively evaluated for-cause biopsies at our center between 2011 and 2017. We included biopsies that met the diagnosis of ABMR by histology, along with simultaneous evaluation for anti-Human Leukocyte Antigen (HLA) donor-specific antibodies (DSA). We evaluated death-censored graft loss (DCGL) and used a principal component analysis (PCA) approach to identify key predictors of outcomes. Out of the histologic ABMR cohort (n=118), 70 were DSA-positive ABMR, while 48 had no DSA. DSA(+)ABMR were younger and more often female recipients. DSA(+)ABMR occurred significantly later post-transplant than DSA(-)ABMR suggesting time-dependence. DSA(+)ABMR had higher inflammatory scores (i,t), chronicity scores (ci, ct) and tended to have higher MVI scores. Immunodominance of DQ-DSA in DSA(+)ABMR was associated with higher i+t scores. Clinical/histologic factors significantly associated with DCGL after biopsy were inputted into the PCA. Principal component-1 (PC-1), which contributed 34.8% of the variance, significantly correlated with time from transplantation to biopsy, ci/ct scores and DCGL. In the PCA analyses, i, t scores, DQ-DSA, and creatinine at biopsy retained significant correlations with GL-associated PCs. Time from transplantation to biopsy plays a major role in the prognosis of biopsies with histologic ABMR and MVI, likely due to ongoing chronic allograft injury over time.

Impaired fatty acid metabolism perpetuates lipotoxicity along the transition to chronic kidney injury.

Energy metabolism failure in proximal tubule cells (PTCs) is a hallmark of chronic kidney injury. We combined transcriptomic, metabolomic, and lipidomic approaches in experimental models and patient cohorts to investigate the molecular basis of the progression to chronic kidney allograft injury initiated by ischemia/reperfusion injury (IRI). The urinary metabolome of kidney transplant recipients with chronic allograft injury and who experienced severe IRI was substantially enriched with long chain fatty acids (FAs). We identified a renal FA-related gene signature with low levels of carnitine palmitoyltransferase 2 (Cpt2) and acyl-CoA synthetase medium chain family member 5 (Acsm5) and high levels of acyl-CoA synthetase long chain family member 4 and 5 (Acsl4 and Acsl5) associated with IRI, transition to chronic injury, and established chronic kidney disease in mouse models and kidney transplant recipients. The findings were consistent with the presence of Cpt2-Acsl4+Acsl5+Acsm5- PTCs failing to recover from IRI as identified by single-nucleus RNA-Seq. In vitro experiments indicated that ER stress contributed to CPT2 repression, which, in turn, promoted lipids' accumulation, drove profibrogenic epithelial phenotypic changes, and activated the unfolded protein response. ER stress through CPT2 inhibition and lipid accumulation engaged an auto-amplification loop leading to lipotoxicity and self-sustained cellular stress. Thus, IRI imprints a persistent FA metabolism disturbance in the proximal tubule, sustaining the progression to chronic kidney allograft injury.

240.3: Detection of CMV Mediated Sub-Clinical Rejection by Urine Biomarkers

Methods: Research on early detection of Cytomegalovirus (CMV) mediated sub-clinical rejection (sAR) is in its nascence. This study explores the efficacy of urine-based biomarkers for sAR risk prognostication. Urine samples were serially collected (1 week- 2yrs) across 125 unique renal allograft recipients from UCSF and UCLA. These CMV+ (blood CMV-PCR) patients received valganciclovir therapy until CMV- for 3 consecutive months. Analysis: We computed a machine-learning based rejection prediction score incorporating urine cell-free DNA (cfDNA), methylated cfDNA, total protein, CXCL10, clusterin and creatinine. Rejection was determined between scores of 32-100; higher score associated with biopsy severity (Yang et al, STM 2021). In a cross-sectional analysis, Kruskal-Wallis test was performed on the urine-score distribution, to determine sAR during CMV+. Subsequently UCSF samples were analyzed longitudinally to establish the relationship between CMV and sAR; this was validated independently in UCLA samples. Results: Significant differences were observed in scores >32 between biopsy-confirmed AR vs. stable (p: 0.0034) and CMV vs. stable (p=0.003). Longitudinal analysis yielded 3 primary sAR patterns following CMV infection; (i)persistence of sAR leading to new development of chronic allograft injury; (ii)early sAR (score >32) followed by a further increase in score (>55) with biopsy confirmed cAR; (iii)sAR (>32) followed by recovery of injury with CMV resolution and a decline in score <32). Conclusions: We provide a urine-based method for detecting sAR at the time of CMV infection, and its potential clinical utility for titrating use of anti-viral therapy and recipient immunosuppression load.

Assessment of Renal Allograft Stiffness and Viscosity Using 2D SWE PLUS and Vi PLUS Measures-A Pilot Study.

Elastography is a useful noninvasive tool for the assessment of renal transplant recipients. 2D-shear wave elastography (SWE) PLUS and viscosity plane-wave ultrasound (Vi PLUS) have emerged as novel techniques that promise to offer improved renal stiffness and viscosity measures due to improved processing algorithms. Methods: We performed a cross-sectional study of 50 kidney transplanted patients (16 women, 34 men; mean age of 47.5 ± 12.5; mean estimated glomerular filtration rate (eGFR) estimated by Chronic Kidney Disease Epidemiology Collaboration formula: 52.19 ± 22.6 mL/min/1.73 m2; and a mean duration after transplant of 10.09 ± 5 years). For every patient, we obtained five valid measurements of renal stiffness (obtained from five different frames in the cortex of the renal graft), and also tissue viscosity, with a C6-1X convex transducer using the Ultra-Fast™ software available on the Aixplorer Mach 30 ultrasound system (Supersonic Imagine, Aix-en-Provence, France). The median values of elastographic and viscosity measures have been correlated with the patients’ demographic, biological, and clinical parameters. Results: We obtained a cut-off value of renal cortical stiffness of <27.3 kiloPascal(kPa) for detection of eGFR < 60 mL/min/1.73 m2 with 80% sensitivity and 85% specificity (AUC = 0.811, p < 0.0001), a cut-off value of <26.9 kPa for detection of eGFR < 45 mL/min/1.73 m2 with 82.6% sensitivity and 74% specificity (AUC = 0.789, p < 0.0001), and a cut-off value of <23 kPa for detection of eGFR < 30 mL/min/1.73 m2 with 88.8% sensitivity and 75.6% specificity (AUC = 0.852, p < 0.0001). We found a positive correlation coefficient between eGFR and the median measure of renal cortical stiffness (r = 0.5699, p < 0.0001), between eGFR the median measure of viscosity (r = 0.3335, p = 0.0180), between median depth of measures and renal cortical stiffness (r = −0.2795, p = 0.0493), and between median depth of measures and body mass index (BMI) (r = 0.6574, p < 0.0001). Our study showed good intra-operator agreement for both 2D SWE PLUS measures—with an intraclass correlation coefficient (ICC) of 0.9548 and a 95% CI of 0.9315 to 0.9719—and Vi PLUS, with an ICC of 0.8323 and a 95% CI of 0.7457 to 0.8959. The multivariate regression model showed that 2D SWE PLUS values were associated with eGFR, Vi PLUS, and depth of measures. Conclusions: Assessment of renal allograft stiffness and viscosity may prove to be an effective method for identifying patients with chronic allograft injury and could prove to be a low-cost approach to provide additional diagnostic information of kidney transplanted patients.

Bringing Clarity to the Murky Problem of Cardiac Allograft Vasculopathy

Although most published studies involving preclinical mouse models of cardiac allograft rejection tend to center on the issues of acute rejection and tolerance induction, arguably the more pressing need in the field of clinical transplantation is better understanding of chronic allograft injury. That is, chronic graft injury is a far greater current clinical problem than is early graft loss due to acute rejection. In heart transplantation, cardiac allograft vasculopathy (CAV) is a form of pronounced coronary artery disease that occurs over time after transplant1 and remains the major source of transplant loss and recipient mortality.

Prognostic and Diagnostic Value of Endocan in Kidney Diseases.

Endocan, previously called endothelial cell-specific molecule-1, is a soluble proteoglycan that is predominantly expressed in vascular endothelial cells of the lungs and kidneys. It is upregulated by proinflammatory cytokines and plays a critical role in inflammatory, proliferative, and neovascularization processes. The utility of endocan as a biomarker in a wide spectrum of diseases is being increasingly acknowledged. In this review, we summarize the current evidence concerning the role of endocan in kidney diseases, with emphasis on its prognostic and diagnostic value. It seems that the determination of plasma endocan levels may provide useful prognostic information in many types of renal failure such as chronic kidney disease, IgA nephropathy, and diabetic nephropathy. Endocan could additionally improve the early diagnostic evaluation of acute kidney disease, chronic renal allograft injury, and acute rejection after kidney transplantation, thus contributing to endothelial cell injury monitoring in a timely manner.

Role of Complement System in Kidney Transplantation: Stepping From Animal Models to Clinical Application.

Kidney transplantation is a life-saving strategy for patients with end-stage renal diseases. Despite the advances in surgical techniques and immunosuppressive agents, the long-term graft survival remains a challenge. Growing evidence has shown that the complement system, part of the innate immune response, is involved in kidney transplantation. Novel insights highlighted the role of the locally produced and intracellular complement components in the development of inflammation and the alloreactive response in the kidney allograft. In the current review, we provide the updated understanding of the complement system in kidney transplantation. We will discuss the involvement of the different complement components in kidney ischemia–reperfusion injury, delayed graft function, allograft rejection, and chronic allograft injury. We will also introduce the existing and upcoming attempts to improve allograft outcomes in animal models and in the clinical setting by targeting the complement system.