Association of Serum Activin Levels with Allograft Outcomes in Patients with Kidney Transplant: Results from the KNOW-KT.

INTRODUCTION: Serum activin A has been reported to contribute to vascular calcification and kidney fibrosis in chronic kidney disease. We aimed to investigate whether higher serum activin levels were associated with poor allograft outcomes in patients with kidney transplantation (KT). METHODS: A total of 860 KT patients from KNOW-KT (Korean Cohort Study for Outcome in Patients with Kidney Transplantation) were analyzed. We measured serum activin levels pre-KT and 1 year after KT. The primary outcome was the composite of a ≥50% decline in estimated glomerular filtration rate and graft failure. Multivariable cause-specific hazard model was used to analyze association of 1-year activin levels with the primary outcome. The secondary outcome was coronary artery calcification score (CACS) at 5 years after KT. RESULTS: During the median follow-up of 6.7 years, the primary outcome occurred in 109 (12.7%) patients. The serum activin levels at 1 year were significantly lower than those at pre-KT (488.2 ± 247.3 vs. 704.0 ± 349.6). When patients were grouped based on the median activin level at 1 year, the high-activin group had a 1.91-fold higher risk (95% CI, 1.25-2.91) for the primary outcome compared to the low-activin group. A one-standard deviation increase in activin levels as a continuous variable was associated with a 1.36-fold higher risk (95% CI, 1.16-1.60) for the primary outcome. Moreover, high activin levels were significantly associated with 1.56-fold higher CACS (95% CI, 1.12-2.18). CONCLUSION: Post-transplant activin levels were independently associated with allograft functions as well as coronary artery calcification in KT patients.

Alteration of γδ T cell subsets in non-human primates transplanted with GGTA1 gene-deficient porcine blood vessels.

BACKGROUND: αGal-deficient xenografts are protected from hyperacute rejection during xenotransplantation but are still rejected more rapidly than allografts. Despite studies showing the roles of non-Gal antibodies and αß T cells in xenograft rejection, the involvement of γδ T cells in xenograft rejection has been limitedly investigated. METHODS: Six male cynomolgus monkeys were transplanted with porcine vessel xenografts from wild-type (n = 3) or GGTA1 knockout (n = 3) pigs. We measured the proportions and T cell receptor (TCR) repertoires of blood γδ T cells before and after xenotransplant. Grafted porcine vessel-infiltrating immune cells were visualized at the end of experiments. RESULTS: Blood γδ T cells expanded and infiltrated into the graft vessel adventitia following xenotransplantation of α-Gal-deficient pig blood vessels. Pre- and post-transplant analysis of γδ TCR repertoire revealed a transition in δ chain usage post-transplantation, with the expansion of several clonotypes of δ1, δ3, or δ7 chains. Furthermore, the distinctions between pre- and post-transplant δ chain usages were more prominent than those observed for γ chain usages. CONCLUSION: γδ TCR repertoire was significantly altered by xenotransplantation, suggesting the role of γδ T cells in sustained xenoreactive immune responses.

Impact of Blood Pressure on Allograft Function and Survival in Kidney Transplant Recipients.

The optimal target blood pressure for kidney transplant (KT) patients remains unclear. We included 808 KT patients from the KNOW-KT as a discovery set, and 1,294 KT patients from the KOTRY as a validation set. The main exposures were baseline systolic blood pressure (SBP) at 1 year after KT and time-varying SBP. Patients were classified into five groups: SBP <110; 110-119; 120-129; 130-139; and ≥140 mmHg. SBP trajectories were classified into decreasing, stable, and increasing groups. Primary outcome was composite kidney outcome of ≥50% decrease in eGFR or death-censored graft loss. Compared with the 110-119 mmHg group, both the lowest (adjusted hazard ratio [aHR], 2.43) and the highest SBP (aHR, 2.25) were associated with a higher risk of composite kidney outcome. In time-varying model, also the lowest (aHR, 3.02) and the highest SBP (aHR, 3.60) were associated with a higher risk. In the trajectory model, an increasing SBP trajectory was associated with a higher risk than a stable SBP trajectory (aHR, 2.26). This associations were consistent in the validation set. In conclusion, SBP ≥140 mmHg and an increasing SBP trajectory were associated with a higher risk of allograft dysfunction and failure in KT patients.

A comparative analysis of clinical outcomes between conversion to mTOR inhibitor and calcineurin inhibitor reduction in managing BK viremia among kidney transplant patients.

BK virus-associated nephropathy (BKVAN) exerts a substantial impact on allograft survival, however, the absence of robust clinical evidence regarding treatment protocols adds to the complexity of managing this condition. This study aimed to compare the two treatment approaches. The study population consisted of patients who underwent kidney transplantation between January 2016 and June 2020 at two tertiary hospitals in Korea. Patients diagnosed with BK viremia were evaluated based on their initial viral load and the treatment methods. The 'Reduction group' involved dose reduction of tacrolimus while the 'Conversion group' included tacrolimus discontinuation and conversion to sirolimus. A total of 175 patients with an initial viral load (iVL) ≥ 3 on the log10 scale were evaluated within two iVL intervals (3-4 and 4-5). In the iVL 4-5 interval, the Reduction group showed potential effectiveness in terms of viral clearance without statistically significant differences. However, within the iVL 3-4 interval, the Reduction group demonstrated superior viral clearance and a lower incidence of biopsy-proven acute rejection (BPAR) than the Conversion group. The renal function over 12 months after BKV diagnosis showed no statistically significant difference. Reducing tacrolimus compared to converting to mTORi would be a more appropriate treatment approach for BK viral clearance in kidney transplantation. Further research is warranted in a large cohort of patients.

A Novel Pre-Clinical Modeling of Massive Hemorrhagic Shock in Non-Human Primate: A Safe and Reproducible Method (Macaca fascicularis).

BACKGROUND: Although non-human primates are the closest animals to humans to simulate physiological and metabolic responses, there is a paucity of primate hemorrhagic shock models that are standardized and reproducible. Herein, we describe a model that is a clinical replica of extreme class IV hemorrhagic shock with a step-by-step description of the procedure in cynomolgus macaque monkeys. METHODS: The physiological changes that occurred during the process were evaluated using hemodynamic parameters, echocardiogram, and laboratory values. Five female monkeys were subjected to trauma laparotomy, followed by cannulation of the abdominal aorta to achieve graded hemorrhage. A central line was placed in the right internal jugular vein, which was subsequently used for laboratory sampling and volume resuscitation. The withdrawal of blood was ceased when a predefined cardiac endpoint with cardiac arrhythmia or bradycardia was reached. The animals were then immediately resuscitated with transfusion. The primary cardiac endpoint was consistently reached in all 5 animals during the fourth hemorrhage when more than 70% of the estimated total blood volume was lost. RESULTS: No mortality occurred during the process. The blood pressure, cardiac output measured from an echocardiogram, and hemoglobin correlated well with increasing loss of circulating volume, whereas the pulse pressure variation did not. The echocardiogram was also a useful predictor for urgent volume replacement. CONCLUSION: This model offers a safe and reproducible surgical hemorrhagic model in non-human primates and simulates clinical practice. This could provide a useful platform on which further studies can be carried out to address unanswered questions in trauma management.

The effect of hydroxyethyl starch as a cryopreservation agent during freezing of mouse pancreatic islets.

Islet transplantation is the most effective treatment strategy for type 1 diabetes. Long-term storage at ultralow temperatures can be used to prepare sufficient islets of good quality for transplantation. For freezing islets, dimethyl sulfoxide (DMSO) is a commonly used penetrating cryoprotective agent (CPA). However, the toxicity of DMSO is a major obstacle to cell cryopreservation. Hydroxyethyl starch (HES) has been proposed as an alternative CPA. To investigate the effects of two types of nonpermeating CPA, we compared 4 % HES 130 and HES 200 to 10 % DMSO in terms of mouse islet yield, viability, and glucose-stimulated insulin secretion (GSIS). After one day of culture, islets were cryopreserved in each solution. After three days of cryopreservation, islet recovery was significantly higher in the HES 130 and HES 200 groups than in the DMSO group. Islet viability in the HES 200 group was also significantly higher than that in the DMSO group on Day 1 and Day 3. Stimulation indices determined by GSIS were higher in the HES 130 and 200 groups than in the DMSO group on Day 3. After three days of cryopreservation, HES 130 and HES 200 both reduced the expression of apoptosis- and necrosis-associated proteins and promoted the survival of islets. In conclusion, the use of HES as a CPA improved the survival and insulin secretion of cryopreserved islets compared with the use of a conventional CPA.

Preoperative Intrathecal Morphine is Associated With Reduced Postoperative Pain, Agitation, and Delirium In Living Donor Kidney Transplantation Recipients.

BACKGROUND: Postoperative delirium after organ transplantation can lead to increased length of hospital stay and mortality. Because pain is an important risk factor for delirium, perioperative analgesia with intrathecal morphine (ITM) may mitigate postoperative delirium development. We evaluated if ITM reduces postoperative delirium incidence in living donor kidney transplant (LDKT) recipients. METHODS: Two hundred ninety-six patients who received LDKT between 2014 and 2018 at our hospital were retrospectively analyzed. Recipients who received preoperative ITM (ITM group) were compared with those who did not (control group). The primary outcome was postoperative delirium based on the Confusion Assessment Method for Intensive Care Unit results during the first 4 postoperative days. RESULTS: Delirium occurred in 2.6% (4/154) and 7.0% (10/142) of the ITM and control groups, respectively. Multivariable analysis showed age (odds ratio [OR]: 1.07, 95% CI: 1.01-1.14; P = .031), recent smoking (OR: 7.87, 95% CI: 1.43-43.31; P = .018), preoperative psychotropics (OR: 23.01, 95% CI: 3.22-164.66; P = .002) were risk factors, whereas ITM was a protective factor (OR: 0.23, 95% CI: 0.06-0.89; P = .033). CONCLUSIONS: Preoperative ITM showed an independent association with reduced post-LDKT delirium. Further studies and the development of regional analgesia for delirium prevention may enhance the postoperative recovery of transplant recipients.

Monitoring Porcine Cytomegalovirus in Both Donors and Recipients is Crucial for Recipient's Survival in Pig-to-Cynomolgus Xenotransplantation.

BACKGROUND: Xenotransplantation, particularly when involving pig donors, presents challenges related to the transmission of porcine cytomegalovirus (pCMV) and its potential impact on recipient outcomes. This study aimed to investigate the relationship between pCMV positivity in both donors and recipients and the survival time of cynomolgus monkey recipients after xenogeneic kidney transplantation. METHODS: We conducted 20 cynomolgus xenotransplants using 18 transgenic pigs. On the surgery day, donor pig blood was sampled, and DNA was extracted from serum and peripheral blood mononuclear cells. Recipient DNA extraction followed the same protocol from pre-transplantation to post-transplantation. Porcine cytomegalovirus detection used real-time polymerase chain reaction (real-time PCR) with the ViroReal kit, achieving a sensitivity of 50 copies/reaction. A Ct value of 37.0 was the pCMV positivity threshold. RESULTS: Of 20 cynomolgus recipients, when donors tested negative for pCMV, recipients also showed negative results in 9 cases. In 4 cases where donors were negative, recipients tested positive. All 5 cases with pCMV-positive donors resulted in positive assessments for recipients. Detection of donor pCMV correlated with shorter recipient survival. Continuous recipient positivity during observation correlated with shorter survival, whereas transient detection showed no significant change in survival rates. However, donor pig phenotypes and transplantation protocols did not significantly impact survival. CONCLUSION: The detection of pCMV in both donors and recipients plays a crucial role in xenotransplantation outcomes. These findings suggest the importance of monitoring and managing pCMV in xenotransplantation to enhance long-term outcomes.

Association of Serum Osteoprotegerin With Vascular Calcification, and Cardiovascular and Graft Outcomes in Kidney Transplant Patients: Results From the KNOW-KT.

BACKGROUND: Vascular calcification and stiffness contribute to increased cardiovascular morbidity in patients with chronic kidney disease. This study investigated associations between serum osteoprotegerin (OPG) levels and vascular calcification or stiffness to assess cardiovascular and graft outcomes in kidney transplant patients. METHODS: The KoreaN cohort study for Outcome in patients With Kidney Transplantation was a prospective multicenter cohort study. Serum OPG levels were measured at baseline and 3 y after transplantation in 1018 patients. Patients were classified into high and low OPG groups according to median serum OPG levels. The median follow-up duration was 93.5 mo. RESULTS: The mean age was 45.8 ±â€…11.7 y and 62.9% were men. Patients with high OPG had significantly higher coronary artery calcium scores, abdominal aortic calcification scores, and brachial-ankle pulse wave velocities than those with lower OPG; these parameters remained significant for 5 y after transplantation. The 3-y OPG levels were lower than baseline values ( P < 0.001) and were positively correlated ( r = 0.42, P < 0.001). Multivariate Cox regression analysis showed that high OPG levels were significantly associated with posttransplant cardiovascular events ( P = 0.008) and death-censored graft loss ( P = 0.004). Similar findings regarding posttransplant cardiovascular events ( P = 0.012) and death-censored graft loss ( P = 0.037) were noted in patients with high OPG at the 3-y follow-up. Mediation analyses revealed that coronary artery calcium scores, abdominal aortic calcification scores, and brachial-ankle pulse wave velocities could act as mediators between serum OPG levels and posttransplant cardiovascular events. CONCLUSIONS: Serum OPG concentration is associated with vascular calcification and stiffness and could be a significant risk factor for cardiovascular outcomes and graft loss in patients undergoing kidney transplantation.

Optimum tacrolimus trough levels for enhanced graft survival and safety in kidney transplantation: a retrospective multicenter real-world evidence study.

BACKGROUND: The current study aimed to determine the optimal tacrolimus trough levels for balancing graft survival and patient safety following kidney transplantation. MATERIALS AND METHODS: We conducted a retrospective cohort study involving 11,868 kidney transplant recipients from five medical centers. The association between tacrolimus exposures (periodic mean trough level, coefficient of variability, time in therapeutic range) and composite allograft outcome (de novo donor specific antibody, biopsy-proven rejection, kidney dysfunction, and graft failure), as well as safety outcomes (severe infection, cardiovascular events, malignancy, and mortality) were assessed. Data were sourced from Clinical Data Warehouses and analyzed using advanced statistical methods, including Cox marginal structural models with inverse probability treatment weighting. RESULTS: Tacrolimus levels of 5.0-7.9 ng/mL and 5.0-6.9 ng/mL during the 2-12 month and 12-72 month post-transplantation periods, respectively, were associated with reduced risks of composite allograft outcomes. During the first post-transplant year, the adjusted hazard ratios (aHR) for composite allograft outcomes were: 0.69 (95% CI 0.55-0.85, P<0.001) for 5.0-5.9 ng/mL; 0.81 (95% CI 0.67-0.98, P=0.033) for 6.0-6.9 ng/mL; and 0.73 (95% CI 0.60-0.89, P=0.002) for 7.0-7.9 ng/mL (compared to levels ≥8.0 ng/mL). For the 6-year composite outcomes, aHRs were 0.68 (95% CI 0.53-0.87, P=0.002) for 5.0-5.9 ng/mL and 0.65 (95% CI 0.50-0.85, P=0.001) for 6.0-6.9 ng/mL. These optimal ranges showed reduced rates of severe infection (6 y), malignancy (6 y), and mortality (1 y). CONCLUSION: This multicenter study provides robust evidence for optimal tacrolimus trough levels during the periods 2-12 and 12-72 months following kidney transplantation.

Development and validation of risk prediction model for post-donation renal function in living kidney donors.

This study aimed to create and validate a predictive model for renal function following live kidney donation, using pre-donation factors. Accurately predicting remaining renal function post live kidney donation is currently insufficient, necessitating an effective assessment tool. A multicenter retrospective study of 2318 live kidney donors from two independent centers (May 2007-December 2019) was conducted. The primary endpoint was the reduction in eGFR to below 60 mL/min/m2 6 months post-donation. The primary endpoint was achieved in 14.4% of the training cohort and 25.8% of the validation cohort. Sex, age, BMI, hypertension, preoperative eGFR, and remnant kidney proportion (RKP) measured by computerized tomography (CT) volumetry were found significant in the univariable analysis. These variables informed a scoring system based on multivariable analysis: sex (male: 1, female: 0), age at operation (< 30: 0, 30-39: 1, 40-59: 2, ≥ 60: 3), preoperative eGFR (≥ 100: 0, 90-99: 2, 80-89: 4, < 80: 5), and RKP (≥ 52%: 0, < 52%: 1). The total score ranged from 0 to 10. The model showed good discrimination for the primary endpoint in both cohorts. The prediction model provides a useful tool for estimating post-donation renal dysfunction risk, factoring in the side of the donated kidney. It offers potential enhancement to pre-donation evaluations.

Impact of Arterial Calcification on Cardiovascular and Renal Outcomes in Kidney Transplant Patients.

Introduction: Coronary artery calcification score (CACS) and abdominal aortic calcification score (AACS) are both well-established markers of vascular stiffness, and previous studies have shown that a higher CACS is a risk factor for chronic kidney disease (CKD) progression. However, the impact of pretransplant CACS and AACS on cardiovascular and renal outcomes in kidney transplant patients has not been established. Methods: We included 944 kidney transplant recipients from the KoreaN cohort study for Outcome in patients With Kidney Transplantation (KNOW-KT) cohort and categorized them into three groups (low, medium, and high) according to baseline CACS (0, 0 < and ≤100, >100) and AACS (0, 1-4, >4). The low (0), medium (0 < and ≤ 100), and high (>100) CACS groups each consisted of 462, 213, and 225 patients, respectively. Similarly, the low (0), medium (1-4), and high (>4) AACS groups included 638, 159, and 147 patients, respectively. The primary outcome was the occurrence of cardiovascular events. The secondary outcomes were all-cause mortality and composite kidney outcomes, which comprised of >50% decline in the estimated glomerular filtration rate and graft loss. Cox regression analysis was used to investigate the association between baseline CACS/AACS and outcomes. Results: The high CACS group (N = 462) faced a significantly higher risk for cardiovascular outcomes (adjusted hazard ratio [aHR], 5.97; 95% confidence interval [CI], 2.01-17.7) and all-cause mortality (aHR, 2.74; 95% CI, 1.27-5.92) compared to the low CACS group (N = 225). Similarly, the high AACS group (N = 638) had an elevated risk for cardiovascular outcomes (aHR, 2.38; 95% CI, 1.16-4.88). Furthermore, the addition of CACS to prediction models improved prediction indices for cardiovascular outcomes. However, the risk of renal outcomes did not differ among CACS or AACS groups. Conclusion: Pretransplant arterial calcification, characterized by high CACS or AACS, is an independent risk factor for cardiovascular outcomes and mortality in kidney transplant patients.

Arterial calcification, accumulation of calcium in the arterial walls, vascular stiffness, and loss of elasticity of blood vessels can contribute to the development of cardiovascular diseases. Patients with chronic kidney disease and those undergoing dialysis have a considerably increased risk of vascular calcification. Even after kidney transplantation when kidney function has been restored, the prevalence of vascular calcification and subsequent cardiovascular disease remains high. Coronary artery calcification score and abdominal aortic calcification score are both well-established markers of vascular calcification. However, the impact of pretransplant vascular calcification scores on cardiovascular and renal outcomes in kidney transplant patients has not been established. When we analyzed 944 Korean kidney transplant patients, both vascular calcification scores were significantly associated with cardiovascular outcomes after kidney transplantation, but were not associated with renal outcomes. We also demonstrated that the addition of coronary artery calcification scores led to a modest improvement in the prediction performance for kidney transplant outcomes. Our findings suggest a potential role of pretransplant screening of coronary calcification scores and aortic calcification scores in risk stratification for post-kidney transplant outcomes.

Risk Factors for Impaired Cellular or Humoral Immunity after Three Doses of SARS-CoV-2 Vaccine in Healthy and Immunocompromised Individuals.

Background: We aimed to identify the risk factors for impaired cellular and humoral immunity after three doses of the SARS-CoV-2 vaccine. Methods: Six months after the third vaccine dose, T-cell immunity was evaluated using interferon-gamma release assays (IGRAs) in 60 healthy and 139 immunocompromised (IC) individuals, including patients with hematologic malignancy (HM), solid malignancy (SM), rheumatic disease (RD), and kidney transplantation (KT). Neutralizing antibody titers were measured using the plaque reduction neutralization test (PRNT) and surrogate virus neutralization test (sVNT). Results: T-cell immunity results showed that the percentages of IGRA-positive results using wild-type/alpha spike protein (SP) and beta/gamma SP were 85% (51/60) and 75% (45/60), respectively, in healthy individuals and 45.6% (62/136) and 40.4% (55/136), respectively, in IC individuals. IC with SM or KT showed a high percentage of IGRA-negative results. The underlying disease poses a risk for impaired cellular immune response to wild-type SP. The risk was low when all doses were administered as mRNA vaccines. The risk factors for an impaired cellular immune response to beta/gamma SP were underlying disease and monocyte%. In the sVNT using wild-type SP, 12 of 191 (6.3%) individuals tested negative. In the PRNT of 46 random samples, 6 (13%) individuals tested negative for the wild-type virus, and 19 (41.3%) tested negative with omicrons. KT poses a risk for an impaired humoral immune response. Conclusions: Underlying disease poses a risk for impaired cellular immune response after the third dose of the SARS-CoV-2 vaccine; KT poses a risk for impaired humoral immune response, emphasizing the requirement of precautions in patients.

Prediction of very early subclinical rejection with machine learning in kidney transplantation.

Protocol biopsy is a reliable method for assessing allografts status after kidney transplantation (KT). However, due to the risk of complications, it is necessary to establish indications and selectively perform protocol biopsies by classifying the high-risk group for early subclinical rejection (SCR). Therefore, the purpose of this study is to analyze the incidence and risk factors of early SCR (within 2 weeks) and develop a prediction model using machine learning. Patients who underwent KT at Samsung Medical Center from January 2005 to December 2020 were investigated. The incidence of SCR was investigated and risk factors were analyzed. For the development of prediction model, machine learning methods (random forest, elastic net, extreme gradient boosting [XGB]) and logistic regression were used and the performance between the models was evaluated. The cohorts of 987 patients were reviewed and analyzed. The incidence of SCR was 14.6%. Borderline cellular rejection (BCR) was the most common type of rejection, accounting for 61.8% of cases. In the analysis of risk factors, recipient age (OR 0.98, p = 0.03), donor BMI (OR 1.07, p = 0.02), ABO incompatibility (OR 0.15, p < 0.001), HLA II mismatch (two [OR 6.44, p < 0.001]), and ATG induction (OR 0.41, p < 0.001) were associated with SCR in the multivariate analysis. The logistic regression prediction model (average AUC = 0.717) and the elastic net model (average AUC = 0.712) demonstrated good performance. HLA II mismatch and induction type were consistently identified as important variables in all models. The odds ratio analysis of the logistic prediction model revealed that HLA II mismatch (OR 6.77) was a risk factor for SCR, while ATG induction (OR 0.37) was a favorable factor. Early SCR was associated with HLA II mismatches and induction agent and prediction model using machine learning demonstrates the potential to predict SCR.