Treg tissue stability depends on lymphotoxin beta-receptor- and adenosine-receptor-driven lymphatic endothelial cell responses

Regulatory T cell (Treg) lymphatic migration is required for resolving inflammation and prolonging allograft survival. Focusing on Treg interactions with lymphatic endothelial cells (LECs), we dissect mechanisms and functional consequences of Treg transendothelial migration (TEM). Using three genetic mouse models of pancreatic islet transplantation, we show that Treg lymphotoxin (LT) αβ and LEC LTβ receptor (LTβR) signaling are required for efficient Treg migration and suppressive function to prolong allograft survival. Inhibition of LT signaling increases Treg conversion to Foxp3loCD25lo exTregs. In a transwell-based model of TEM across polarized LECs, non-migrated Tregs become exTregs. Such conversion is regulated by LTβR nuclear factor κB (NF-κB) signaling in LECs, which increases interleukin-6 (IL-6) production and drives exTreg conversion. Migrating Tregs are ectonucleotidase CD39hi and resist exTreg conversion in an adenosine-receptor-2A-dependent fashion. Human Tregs migrating across human LECs behave similarly. These molecular interactions can be targeted for therapeutic manipulation of immunity and suppression.

Clinically adjudicated deceased donor acute kidney injury and graft outcomes

BACKGROUND

Acute kidney injury (AKI) in deceased donors is not associated with graft failure (GF). We hypothesize that hemodynamic AKI (hAKI) comprises the majority of donor AKI and may explain this lack of association.

METHODS

In this ancillary analysis of the Deceased Donor Study, 428 donors with available charts were selected to identify those with and without AKI. AKI cases were classified as hAKI, intrinsic (iAKI), or mixed (mAKI) based on majority adjudication by three nephrologists. We evaluated the associations between AKI phenotypes and delayed graft function (DGF), 1-year eGFR and GF. We also evaluated differences in urine biomarkers among AKI phenotypes.

RESULTS

Of the 291 (68%) donors with AKI, 106 (36%) were adjudicated as hAKI, 84 (29%) as iAKI and 101 (35%) as mAKI. Of the 856 potential kidneys, 669 were transplanted with 32% developing DGF and 5% experiencing GF. Median 1-year eGFR was 53 (IQR: 41-70) ml/min/1.73m2. Compared to non-AKI, donors with iAKI had higher odds DGF [aOR (95%CI); 4.83 (2.29, 10.22)] and had lower 1-year eGFR [adjusted B coefficient (95% CI): -11 (-19, -3) mL/min/1.73 m2]. hAKI and mAKI were not associated with DGF or 1-year eGFR. Rates of GF were not different among AKI phenotypes and non-AKI. Urine biomarkers such as NGAL, LFABP, MCP-1, YKL-40, cystatin-C and albumin were higher in iAKI.

CONCLUSION

iAKI was associated with higher DGF and lower 1-year eGFR but not with GF. Clinically phenotyped donor AKI is biologically different based on biomarkers and may help inform decisions regarding organ utilization.

Characterization of Leptin Receptor+ Stromal Cells in Lymph Node

Lymph node (LN)-resident stromal cells play an essential role in the proper functioning of LNs. The stromal compartment of the LN undergoes significant compensatory changes to produce a milieu amenable for regulation of the immune response. We have identified a distinct population of leptin receptor-expressing (LepR+) stromal cells, located in the vicinity of the high endothelial venules (HEVs) and lymphatics. These LepR+ stromal cells expressed markers for fibroblastic reticular cells (FRCs), but they lacked markers for follicular dendritic cells (FDCs) and marginal reticular cells (MRCs). Leptin signaling deficiency led to heightened inflammatory responses within the LNs of db/db mice, leakiness of HEVs, and lymphatic fragmentation. Leptin signaling through the JAK/STAT pathway supported LN stromal cell survival and promoted the anti-inflammatory properties of these cells. Conditional knockout of the LepR+ stromal cells in LNs resulted in HEV and extracellular matrix (ECM) abnormalities. Treatment of ob/ob mice with an agonist leptin fusion protein restored the microarchitecture of LNs, reduced intra-LN inflammatory responses, and corrected metabolic abnormalities. Future studies are needed to study the importance of LN stomal cell dysfunction to the pathogenesis of inflammatory responses in type 2 diabetes (T2D) in humans.

Kidney-Draining Lymph Node Fibrosis Following Unilateral Ureteral Obstruction

Although the primary organ has been the subject of intense investigation in the field of organ fibrosis over the past several decades, the presence of lymph node fibrosis due to persistent activation of the immune response in its partner organ remains largely unknown. Previously, we demonstrated that activation of the immune response following ischemia-reperfusion injury (IRI) and crescentic glomerulonephritis (CGN) in the kidney was associated with extracellular matrix (ECM) production by fibroblastic reticular cells (FRCs) of the kidney-draining lymph node (KLN). Here, we sought to determine whether FRCs in the KLN become similarly fibrogenic following unilateral ureteral obstruction (UUO) of the kidney. We subjected 6-8-week-old C57BL/6J mice to UUO for 2, 7, and 14 days. We examined the microarchitecture of the kidney and KLN by immunofluorescence staining at each timepoint, and we quantified immune cell populations in the KLN by flow cytometry. The contralateral kidney unaffected by UUO and its partner KLN were used as controls. We found through immunofluorescence staining that FRCs increased production of ECM fibers and remodeled the microarchitecture of the UUO KLN, contributing to fibrosis that mirrored the changes in the kidney. We also observed by flow cytometry that the populations of CD11b+ antigen-presenting cells, CD11c+ dendritic cells, and activated CD4+ and CD8+ T cells were significantly higher in the UUO KLN than the KLN draining the unaffected contralateral kidney. Expression of the TGFβ/TGFβR signaling pathway was upregulated and colocalized with FRCs in the UUO KLNs, suggesting a possible mechanism behind the fibrosis. Both release of ureteral ligation at 2 days following UUO and depletion of FRCs at the time of injury onset halted the progression of fibrosis in both the kidney and the KLN. These findings for the first time highlight the association between fibrosis both in the kidney and the KLN during UUO, and they lay the groundwork for future studies that will investigate more deeply the mechanisms behind the connection between FRCs and KLN fibrosis.

Validation and clinical outcome in assessing donor-derived cell-free DNA monitoring insights of kidney allografts with longitudinal surveillance (ADMIRAL) study

The use of routine monitoring of donor-derived cell-free DNA (dd-cfDNA) after kidney transplant may allow clinicians to identify subclinical allograft injury and intervene prior to development of clinically evident graft injury. To evaluate this, data from 1092 kidney transplant recipients monitored for dd-cfDNA over a three year period was analyzed to assess the association of dd-cfDNA with histologic evidence of allograft rejection. Elevation of dd-cfDNA (0.5% or more) was significantly correlated with clinical and subclinical allograft rejection. dd-cfDNA values of 0.5% or more were associated with a nearly three-fold increase in risk development of de novo donor specific antibodies (hazard ratio 2.71) and were determined to be elevated a median of 91 days (inter quartile range of 30-125 days) ahead of donor specific antibody identification. Persistently elevated dd-cfDNA (more than one result above the 0.5% threshold) predicted over a 25% decline in the estimated glomerular filtration rate over three years (hazard ratio 1.97). Therefore, routine monitoring of dd-cfDNA allowed early identification of clinically important graft injury. Biomarker monitoring complemented histology and traditional laboratory surveillance strategies as a prognostic marker and risk-stratification tool post-transplant. Thus, persistently low dd-cfDNA levels may accurately identify allograft quiescence, or absence of injury, paving the way for personalization of immunosuppression trials.

Chronic rejection as a persisting phantom menace in organ transplantation: a new hope in the microbiota?

PURPOSE OF REVIEW

The microbiota plays an important role in health and disease. During organ transplantation, perturbations in microbiota influence transplant outcome. We review recent advances in characterizing microbiota and studies on regulation of intestinal epithelial barrier function and mucosal and systemic immunity by microbiota and their metabolites. We discuss implications of these interactions on transplant outcomes.

RECENT FINDINGS

Metagenomic approaches have helped the research community identify beneficial and harmful organisms. Microbiota regulates intestinal epithelial functions. Signals released by epithelial cells or microbiota trigger pro-inflammatory or anti-inflammatory effects on innate and adaptive immune cells, influencing the structure and function of the immune system. Assessment and manipulation of microbiota can be used for biomarkers for diagnosis, prognosis, and therapy.

SUMMARY

The bidirectional dialogue between the microbiota and immune system is a major influence on immunity. It can be targeted for biomarkers or therapy. Recent studies highlight a close association of transplant outcomes with microbiota, suggesting exciting potential avenues for management of host physiology and organ transplantation.

Clinical Validation of an Immune Quiescence Gene Expression Signature in Kidney Transplantation

Background

Despite advances in immune suppression, kidney allograft rejection and other injuries remain a significant clinical concern, particularly with regards to long-term allograft survival. Evaluation of immune activity can provide information about rejection status and help guide interventions to extend allograft life. Here, we describe the validation of a blood gene expression classifier developed to differentiate immune quiescence from both T cell-mediated rejection (TCMR) and antibody-mediated rejection (ABMR).

Methods

A five-gene classifier (DCAF12, MARCH8, FLT3, IL1R2, and PDCD1) was developed on 56 peripheral blood samples and validated on two sample sets independent of the training cohort. The primary validation set comprised 98 quiescence samples and 18 rejection samples: seven TCMR, ten ABMR, and one mixed rejection. The second validation set included eight quiescence and 11 rejection samples: seven TCMR, two ABMR, and two mixed rejection. AlloSure donor-derived cell-free DNA (dd-cfDNA) was also evaluated.

Results

AlloMap Kidney classifier scores in the primary validation set differed significantly between quiescence (median, 9.49; IQR, 7.68-11.53) and rejection (median, 13.09; IQR, 11.25-15.28), with P<0.001. In the second validation set, the cohorts were statistically different (P=0.03) and the medians were similar to the primary validation set. The AUC for discriminating rejection from quiescence was 0.786 for the primary validation and 0.800 for the second validation. AlloMap Kidney results were not significantly correlated with AlloSure, although both were elevated in rejection. The ability to discriminate rejection from quiescence was improved when AlloSure and AlloMap Kidney were used together (AUC, 0.894).

Conclusion

Validation of AlloMap Kidney demonstrated the ability to differentiate between rejection and immune quiescence using a range of scores. The diagnostic performance suggests that assessment of the mechanisms of immunologic activity is complementary to allograft injury information derived from AlloSure dd-cfDNA. Together, these biomarkers offer a more comprehensive assessment of allograft health and immune quiescence.

Life-years lost due to cancer among solid organ transplant recipients in the United States, 1987 to 2014

BACKGROUND

Solid organ transplant recipients have an elevated risk of cancer. Quantifying the life-years lost (LYL) due to cancer provides a complementary view of the burden of cancer distinct from other metrics and may identify subgroups of transplant recipients who are most affected.

METHODS

Linked transplant and cancer registry data were used to identify incident cancers and deaths among solid organ transplant recipients in the United States (1987-2014). Data on LYL due to cancer within 10 years posttransplant were derived using mean survival estimates from Cox models.

RESULTS

Among 221,962 transplant recipients, 13,074 (5.9%) developed cancer within 10 years of transplantation. During this period, the mean LYL due to cancer were 0.16 years per transplant recipient and 2.7 years per cancer case. Cancer was responsible for a loss of 1.9% of the total life-years expected in the absence of cancer in this population. Lung recipients had the highest proportion of total LYL due to cancer (0.45%) followed by heart recipients (0.29%). LYL due to cancer increased with age, from 0.5% among those aged birth to 34 years at transplant to 3.2% among those aged 50 years and older. Among recipients overall, lung cancer was the largest contributor, accounting for 24% of all LYL due to cancer, and non-Hodgkin lymphoma had the next highest contribution (15%).

CONCLUSIONS

Transplant recipients have a shortened lifespan after developing cancer. Lung cancer and non-Hodgkin lymphoma contribute strongly to LYL due to cancer within the first 10 years after transplant, highlighting opportunities to reduce cancer mortality through prevention and screening.

Mechanisms of exTreg induction

CD4+ CD25+ Foxp3+ Tregs play an important role in the maintenance of the immune system by regulating immune responses and resolving inflammation. Tregs exert their function by suppressing other immune cells and mediating peripheral self-tolerance. Under homeostatic conditions, Tregs are stable T-cell populations. However, under inflammatory environments, Tregs are converted to CD4+ CD25low Foxp3low cells. These cells are termed "exTreg" or "exFoxp3" cells. The molecular mechanism of Treg transition to exTregs remains incompletely understood. Uncertainties might be explained by a lack of consensus of biological markers to define Treg subsets in general and exTregs in particular. In this review, we summarize known markers of Tregs and factors responsible for exTreg generation including cytokines, signaling pathways, transcription factors, and epigenetic mechanisms. We also identify studies demonstrating the presence of exTregs in various diseases and sources of exTregs. Understanding the biology of Treg transition to exTregs will help in designing Treg-based therapeutic approaches.

Lymph node fibroblastic reticular cells steer immune responses

Lymph nodes (LNs), where immune responses are initiated, are organized into distinctive compartments by fibroblastic reticular cells (FRCs). FRCs imprint immune responses by supporting LN architecture, recruiting immune cells, coordinating immune cell crosstalk, and presenting antigens. Recent high-resolution transcriptional and histological analyses have enriched our knowledge of LN FRC genetic and spatial heterogeneities. Here, we summarize updated anatomic, phenotypic, and functional identities of FRC subsets, delve into topological and transcriptional remodeling of FRCs in inflammation, and illustrate the crosstalk between FRCs and immune cells. Discussing FRC functions in immunity and tolerance, we highlight state-of-the-art FRC-based therapeutic approaches for maintaining physiological homeostasis, steering protective immunity, inducing transplantation tolerance, and treating diverse immune-related diseases.

Association between dd-cfDNA levels, de novo donor specific antibodies, and eGFR decline: An analysis of the DART cohort

BACKGROUND

Donor-derived cell-free DNA (dd-cfDNA) is a marker of allograft injury in transplant recipients; however, the relationship between dd-cfDNA and other clinical parameters associated with adverse allograft outcomes is not well-characterized.

METHODS

We performed a retrospective analysis of kidney transplant recipients from the DART cohort (ClinicalTrials.gov Identifier: NCT02424227) to evaluate the associations between eGFR decline, de novo donor-specific antibodies (dnDSA), and dd-cfDNA.

RESULTS

Both elevated dd-cfDNA (≥1%) and dd-cfDNA variability (≥.34%) in the first post-transplant year were associated with decline in eGFR ≥25% in the second year (21.4% vs. 4.1%, P = .005; 25% vs. 3.6%, P = .002, respectively). Compared to samples from DSA negative patients, samples from patients with concurrent de novo HLA DSAs had higher dd-cfDNA levels (P < .0001).

DISCUSSION

Abnormalities in dd-cfDNA levels are associated with clinical parameters commonly used as surrogate endpoints for adverse allograft outcomes, raising the possibility that molecular injury as characterized by dd-cfDNA could help identify patients at risk of these outcomes.

Post-transplant Diabetes Mellitus in Kidney Transplant Recipients: A Multicenter Study

Background

De novo post-transplant diabetes mellitus (PTDM) is a common complication after kidney transplant (KT). Most recent studies are single center with various approaches to outcome ascertainment.

Methods

In a multicenter longitudinal cohort of 632 nondiabetic adult kidney recipients transplanted in 2010-2013, we ascertained outcomes through detailed chart review at 13 centers. We hypothesized that donor characteristics, such as sex, HCV infection, and kidney donor profile index (KDPI), and recipient characteristics, such as age, race, BMI, and increased HLA mismatches, would affect the development of PTDM among KT recipients. We defined PTDM as hemoglobin A1c ≥6.5%, pharmacological treatment for diabetes, or documentation of diabetes in electronic medical records. We assessed PTDM risk factors and evaluated for an independent time-updated association between PTDM and graft failure using regression.

Results

Mean recipient age was 52±14 years, 59% were male, 49% were Black. Cumulative PTDM incidence 5 years post-KT was 29% (186). Independent baseline PTDM risk factors included older recipient age (P<0.001) and higher BMI (P=0.006). PTDM was not associated with all-cause graft failure (adjusted hazard ratio (aHR), 1.10; 95% CI, 0.78 to 1.55), death-censored graft failure (aHR, 0.85; 95% CI, 0.53 to 1.37), or death (aHR, 1.31; 95% CI, 0.84 to 2.05) at median follow-up of 6 (interquartile range, 4.0-6.9) years post-KT. Induction and maintenance immunosuppression were not different between patients who did and did not develop PTDM.

Conclusions

PTDM occurred commonly, and higher baseline BMI was associated with PTDM. PTDM was not associated with graft failure or mortality during the 6-year follow-up, perhaps due to the short follow-up time.

Deceased-Donor Acute Kidney Injury and BK Polyomavirus in Kidney Transplant Recipients

BACKGROUND AND OBJECTIVES

BK polyomavirus (BKV) infection commonly complicates kidney transplantation, contributing to morbidity and allograft failure. The virus is often donor-derived and influenced by ischemia-reperfusion processes and disruption of structural allograft integrity. We hypothesized that deceased-donor AKI associates with BKV infection in recipients.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We studied 1025 kidney recipients from 801 deceased donors transplanted between 2010 and 2013, at 13 academic centers. We fitted Cox proportional-hazards models for BKV DNAemia (detectable in recipient blood by clinical PCR testing) within 1 year post-transplantation, adjusting for donor AKI and other donor- and recipient-related factors. We validated findings from this prospective cohort with analyses for graft failure attributed to BKV within the Organ Procurement and Transplantation Network (OPTN) database.

RESULTS

The multicenter cohort mean kidney donor profile index was 49±27%, and 26% of donors had AKI. Mean recipient age was 54±13 years, and 25% developed BKV DNAemia. Donor AKI was associated with lower risk for BKV DNAemia (adjusted hazard ratio, 0.53; 95% confidence interval, 0.36 to 0.79). In the OPTN database, 22,537 (25%) patients received donor AKI kidneys, and 272 (0.3%) developed graft failure from BKV. The adjusted hazard ratio for the outcome with donor AKI was 0.7 (95% confidence interval, 0.52 to 0.95).

CONCLUSIONS

In a well-characterized, multicenter cohort, contrary to our hypothesis, deceased-donor AKI independently associated with lower risk for BKV DNAemia. Within the OPTN database, donor AKI was also associated with lower risk for graft failure attributed to BKV.

PODCAST

This article contains a podcast at https://www.asn-online.org/media/podcast/CJASN/2021_03_10_CJN18101120_final.mp3.

Discovering novel injury features in kidney transplant biopsies associated with TCMR and donor aging

We previously characterized the molecular changes in acute kidney injury (AKI) and chronic kidney disease (CKD) in kidney transplant biopsies, but parenchymal changes selective for specific types of injury could be missed by such analyses. The present study searched for injury changes beyond AKI and CKD related to specific scenarios, including correlations with donor age. We defined injury using previously defined gene sets and classifiers and used principal component analysis to discover new injury dimensions. As expected, Dimension 1 distinguished normal vs. injury, and Dimension 2 separated early AKI from late CKD, correlating with time posttransplant. However, Dimension 3 was novel, distinguishing a set of genes related to epithelial polarity (e.g., PARD3) that were increased in early AKI and decreased in T cell-mediated rejection (TCMR) but not in antibody-mediated rejection. Dimension 3 was increased in kidneys from older donors and was particularly important in survival of early kidneys. Thus high Dimension 3 scores emerge as a previously unknown element in the kidney response-to-injury that affects epithelial polarity genes and is increased in AKI but depressed in TCMR, indicating that in addition to general injury elements, certain injury elements are selective for specific pathologic mechanisms. (ClinicalTrials.gov NCT01299168).

Uromodulin to Osteopontin Ratio in Deceased Donor Urine Is Associated With Kidney Graft Outcomes

BACKGROUND

Deceased-donor kidneys experience extensive injury, activating adaptive and maladaptive pathways therefore impacting graft function. We evaluated urinary donor uromodulin (UMOD) and osteopontin (OPN) in recipient graft outcomes.

METHODS

Primary outcomes: all-cause graft failure (GF) and death-censored GF (dcGF). Secondary outcomes: delayed graft function (DGF) and 6-month estimated glomerular filtration rate (eGFR). We randomly divided our cohort of deceased donors and recipients into training and test datasets. We internally validated associations between donor urine UMOD and OPN at time of procurement, with our primary outcomes. The direction of association between biomarkers and GF contrasted. Subsequently, we evaluated UMOD:OPN ratio with all outcomes. To understand these mechanisms, we examined the effect of UMOD on expression of major histocompatibility complex II in mouse macrophages.

RESULTS

Doubling of UMOD increased dcGF risk (adjusted hazard ratio [aHR], 1.1; 95% confidence interval [CI], 1.02-1.2), whereas OPN decreased dcGF risk (aHR, 0.94; 95% CI, 0.88-1). UMOD:OPN ratio ≤3 strengthened the association, with reduced dcGF risk (aHR, 0.57; 0.41-0.80) with similar associations for GF, and in the test dataset. A ratio ≤3 was also associated with lower DGF (aOR, 0.73; 95% CI, 0.60-0.89) and higher 6-month eGFR (adjusted β coefficient, 3.19; 95% CI, 1.28-5.11). UMOD increased major histocompatibility complex II expression elucidating a possible mechanism behind UMOD's association with GF.

CONCLUSIONS

UMOD:OPN ratio ≤3 was protective, with lower risk of DGF, higher 6-month eGFR, and improved graft survival. This ratio may supplement existing strategies for evaluating kidney quality and allocation decisions regarding deceased-donor kidney transplantation.

Factors associated with kidney graft survival in pure antibody-mediated rejection at the time of indication biopsy: Importance of parenchymal injury but not disease activity

We studied the relative association of clinical, histologic, and molecular variables with risk of kidney transplant failure after an indication biopsy, both in all kidneys and in kidneys with pure antibody-mediated rejection (ABMR). From a prospective study of 1679 biopsies with histologic and molecular testing, we selected one random biopsy per patient (N = 1120), including 321 with pure molecular ABMR. Diagnoses were associated with actuarial survival differences but not good predictions. Therefore we concentrated on clinical (estimated GFR [eGFR], proteinuria, time posttransplant, donor-specific antibody [DSA]) and molecular and histologic features reflecting injury (acute kidney injury [AKI] and atrophy-fibrosis [chronic kidney disease (CKD)] and rejection. For all biopsies, univariate analysis found that failure was strongly associated with low eGFR, AKI, CKD, and glomerular deterioration, but not with rejection activity. In molecular ABMR, the findings were similar: Molecular and histologic activity and DSA were not important compared with injury. Survival in DSA-negative and DSA-positive molecular ABMR was similar. Multivariate survival analysis confirmed the dominance of molecular AKI, CKD, and eGFR. Thus, at indication biopsy, the dominant predictors of failure, both in all kidneys and in ABMR, were related to molecular AKI and CKD and to eGFR, not rejection activity, presumably because rejection confers risk via injury.

LTβR Signaling Controls Lymphatic Migration of Immune Cells

The pleiotropic functions of lymphotoxin (LT)β receptor (LTβR) signaling are linked to the control of secondary lymphoid organ development and structural maintenance, inflammatory or autoimmune disorders, and carcinogenesis. Recently, LTβR signaling in endothelial cells has been revealed to regulate immune cell migration. Signaling through LTβR is comprised of both the canonical and non-canonical-nuclear factor κB (NF-κB) pathways, which induce chemokines, cytokines, and cell adhesion molecules. Here, we focus on the novel functions of LTβR signaling in lymphatic endothelial cells for migration of regulatory T cells (Tregs), and specific targeting of LTβR signaling for potential therapeutics in transplantation and cancer patient survival.

G-CSF promotes alloregulatory function of MDSCs through a c-Kit dependent mechanism

Myeloid-derived suppressor cells (MDSC) are a heterogeneous population of immature myeloid cells that expand in inflammatory conditions including transplantation. MDSCs may be capable of controlling rejection. The critical mechanisms underlying MDSC mediated alloregulation remain unexplored. G-CSF potently stimulates MDSC expansion. We hypothesized that G-CSF-induced MDSCs use a novel mechanism to suppress T cell responses. G-CSF promoted expansion of MDSCs and enhanced their suppressive function against T cell proliferation. Gene expression analysis revealed MDSCs expanded with G-CSF upregulated immune-related genes, but downregulated proliferation-related genes when compared to naïve control MDSCs. The KIT oncogene, encoding the c-Kit (CD117) transmembrane tyrosine kinase receptor, was the most significantly increased in MDSCs expanded with G-CSF. c-Kit inhibition with both imatinib and monoclonal blocking antibody reduced expression of ARG-1, iNOS, PD-L1, and SAA3. Further, imatinib also reduced MDSC-mediated T cell suppression in vitro. Modulation of c-Kit activity may represent a therapeutic target for alloregulatory MDSCs.

Dynamic Response of Donor-Derived Cell-Free DNA Following Treatment of Acute Rejection in Kidney Allografts

Background

The quantification of rejection treatment efficacy has been insufficient using traditional markers due, in part, to the lagging response of serum creatinine and histologic alterations on biopsy specimens. Donor-derived cell-free DNA (dd-cfDNA) is a molecular marker of injury that may assess allograft injury after rejection.

Methods

Retrospective review of the DART study identified 70 patients who had a clinically indicated biopsy, simultaneous dd-cfDNA measurement, and at least one follow-up dd-cfDNA within 3 months post-treatment. Thirty-five patients had no biopsy-proven rejection and no rejection treatment (NR), 16 patients had no biopsy-proven rejection but did receive rejection treatment (CR), 9 patients had diagnosis of ABMR/mixed rejection on biopsy and received rejection treatment (ABMR), and 10 patients had diagnosis of TCMR and received rejection treatment (TCMR). The CR, ABMR, and TCMR groups combined to form a rejection (R) group.

Results

In the R group, median dd-cfDNA values at baseline and 1 month were 0.62% and 0.35% (n=21 pairs, p=0.34), and at baseline and 2-3 months were 0.77% and 0.21% (n=23 pairs, p=0.002). In TCMR, median dd-cfDNA values at baseline and 1 month were 1.13% and 0.37% (n=5 pairs, p=0.63), and at baseline and 2-3 months were 0.25% and 0.12% (n=9 pairs, p=0.004). In ABMR, median dd-cfDNA values at baseline and 1 month were 1.61% and 1.2 % (n=6 pairs, p>0.99), and at baseline and 2-3 months were 3.85% and 1.32% (n=6 pairs, p=0.09). In CR, median dd-cfDNA values at baseline and 1 month were 0.31% and 0.29% (n=10 pairs, p=0.38), and at baseline and 2-3 months were 0.38% and 0.17% (n=8 pairs, p=0.31). Lastly, in NR, median dd-cfDNA values at baseline and 1 month were 0.23% and 0.18% (n=21 pairs, p=0.10), and at baseline and 2-3 months were 0.33% and 0.17% (n=26 pairs, p=0.003). Changes in serum creatinine across 1 month and 2-3 months following rejection were similar.

Conclusions

dd-cfDNA may be a useful dynamic biomarker to assess the health of the kidney allograft following rejection treatment.

Renal Function Improvement Following ANG-3777 Treatment in Patients at High Risk for Delayed Graft Function After Kidney Transplantation

BACKGROUND

Patients (20%-50%) undergoing renal transplantation experience acute kidney injury resulting in delayed graft function. ANG-3777 is an hepatocyte growth factor mimetic that binds to the c-MET receptor. In animal models, ANG-3777 decreases apoptosis, increases proliferation, and promotes organ repair and function.

METHODS

This was a randomized, double-blind, placebo-controlled, phase 2 trial of patients undergoing renal transplantation with <50 cc/h urine output for 8 consecutive hours over the first 24 hours posttransplantation, or creatinine reduction ratio <30% from pretransplantation to 24 hours posttransplantation. Subjects were randomized as 2:1 to 3, once-daily IV infusions of ANG-3777, 2 mg/kg (n = 19), or placebo (n = 9). Primary endpoint: time in days to achieve ≥1200 cc urine for 24 hours.

RESULTS

Patients treated with ANG-3777 were more likely to achieve the primary endpoint of 1200 cc urine for 24 hours by 28 days posttransplantation (83.3% versus 50% placebo; log-rank test: χ2 = 2.799, P = 0.09). Compared with placebo, patients in the ANG-3777 arm had larger increases in urine output; lower serum creatinine; greater reduction in C-reactive protein and neutrophil gelatinase-associated lipocalin; fewer dialysis sessions and shorter duration of dialysis; fewer hospital days; significantly less graft failure; and higher estimated glomerular filtration rate. Adverse events occurred in a similar percentage of subjects in both arms. Events per subject were twice as high in the placebo arm.

CONCLUSIONS

There was an efficacy signal for improved renal function in subjects treated with ANG-3777 relative to placebo, with a good safety profile.

Simultaneous targeting of primary tumor, draining lymph node, and distant metastases through high endothelial venule-targeted delivery

Cancer patients with malignant involvement of tumor-draining lymph nodes (TDLNs) and distant metastases have the poorest prognosis. A drug delivery platform that targets the primary tumor, TDLNs, and metastatic niches simultaneously, remains to be developed. Here, we generated a novel monoclonal antibody (MHA112) against peripheral node addressin (PNAd), a family of glycoproteins expressed on high endothelial venules (HEVs), which are present constitutively in the lymph nodes (LNs) and formed ectopically in the tumor stroma. MHA112 was endocytosed by PNAd-expressing cells, where it passed through the lysosomes. MHA112 conjugated antineoplastic drug Paclitaxel (Taxol) (MHA112-Taxol) delivered Taxol effectively to the HEV-containing tumors, TDLNs, and metastatic lesions. MHA112-Taxol treatment significantly reduced primary tumor size as well as metastatic lesions in a number of mouse and human tumor xenografts tested. These data, for the first time, indicate that human metastatic lesions contain HEVs and provide a platform that permits simultaneous targeted delivery of antineoplastic drugs to the three key sites of primary tumor, TDLNs, and metastases.

Contemporary incidence and risk factors of post transplant Erythrocytosis in deceased donor kidney transplantation

BACKGROUND

Post-Transplant erythrocytosis (PTE) has not been studied in large recent cohorts. In this study, we evaluated the incidence, risk factors, and outcome of PTE with current transplant practices using the present World Health Organization criteria to define erythrocytosis. We also tested the hypothesis that the risk of PTE is greater with higher-quality kidneys.

METHODS

We utilized the Deceased Donor Study which is an ongoing, multicenter, observational study of deceased donors and their kidney recipients that were transplanted between 2010 and 2013 across 13 centers. Eryrthocytosis is defined by hemoglobin> 16.5 g/dL in men and> 16 g/dL in women. Kidney quality is measured by Kidney Donor Profile Index (KDPI).

RESULTS

Of the 1123 recipients qualified to be in this study, PTE was observed at a median of 18 months in 75 (6.6%) recipients. Compared to recipients without PTE, those with PTE were younger [mean 48±11 vs 54±13 years, p < 0.001], more likely to have polycystic kidney disease [17% vs 6%, p < 0.001], have received kidneys from younger donors [36 ±13 vs 41±15 years], and be on RAAS inhibitors [35% vs 22%, p < 0.001]. Recipients with PTE were less likely to have received kidneys from donors with hypertension [16% vs 32%, p = 0.004], diabetes [1% vs 11%, p = 0.008], and cerebrovascular event (24% vs 36%, p = 0.036). Higher KDPI was associated with decreased PTE risk [HR 0.98 (95% CI: 0.97-0.99)]. Over 60 months of follow-up, only 17 (36%) recipients had sustained PTE. There was no association between PTE and graft failure or mortality, CONCLUSIONS: The incidence of PTE was low in our study and PTE resolved in majority of patients. Lower KDPI increases risk of PTE. The underutilization of RAAS inhibitors in PTE patients raises the possibility of under-recognition of this phenomenon and should be explored in future studies.

Is Prophylactic Drainage After Pancreas Transplant Associated With Reduced Reoperation Rate?

OBJECTIVES

Advances in surgery and perioperative care have contributed to improved outcomes after pancreas transplant. However, the development of peripancreatic infections carries a poor prognosis. It is not clear whether abdominal drainage is helpful in collection prevention.

MATERIALS AND METHODS

A retrospective review of adult consecutive pancreas transplants at a single institution between January 2017 and December 2018 was undertaken. Postoperative outcomes were compared between patients in whom prophylactic intraoperative drains were placed and patients with no drains.

RESULTS

We identified 83 patients who underwent pancreas transplant with a median age of 45 years; 54.2% were males, and median body mass index was 25.8. Thirty patients had 1 or 2 drains placed (36.1%). There was no difference in the readmission rate (70.0% vs 60.4%; P = .48), reoperation (20.0% vs 30.2%; P = .44), or percutaneous drainage of peripancreatic infections (20.0% vs 15.1%; P = .56) between patients with drains and no drains, respectively. However, prophylactic drainage was associated with a lower rate of reoperation for peripancreatic infections compared with those who were not drained (0.0% vs 13.2%; P < .05). No graft loss occurred in the drain group.

CONCLUSIONS

Prophylactic drainage after pancreas transplant may be helpful for reduction in the infection rate after reoperation. The risks of drain placement should be weighed against those of drain avoidance.

Regulatory T Cells Condition Lymphatic Endothelia for Enhanced Transendothelial Migration

Regulatory T cells (Tregs) express high levels of cell surface lymphotoxin alpha beta (LTα1β2) to activate the LT beta receptor (LTβR) on the lymphatic endothelial cells (LECs), modulating LEC adhesion molecules, intercellular junctions, and chemokines. We demonstrate a role for Tregs through this pathway to condition the permissiveness of lymphatic endothelia for transendothelial migration (TEM), thus gating leukocyte traffic. Human Tregs share the same property with murine Tregs. Activation of TLR2 on Tregs during inflammation specifically augments LTα1β2-LTβR signaling, which further enhances the permissiveness of LECs to facilitate TEM. The conditioning of endothelia may promote the resolution of inflammation by directing leukocytes out of tissues to lymphatic vessels and draining lymph nodes (dLNs). Thus, Tregs interact with lymphatic endothelia under homeostasis and inflammation and dictate endothelial permissiveness and gating mechanisms for subsequent leukocyte migration through endothelial barriers.

Survival benefit of renal transplantation in octogenarians

BACKGROUND

Elderly patients are the fastest growing population requiring renal replacement therapy. As previous studies have shown a survival benefit of kidney transplantation compared to dialysis for end-stage renal disease, we sought to evaluate if this survival benefit extends to octogenarians.

METHODS

This was a single-center retrospective cohort study of renal allograft recipients ≥80 years transplanted from 1999 to 2014 who were compared to patients listed during the same period that did not proceed to transplantation. A secondary matched group was selected from the UNOS transplant waitlist database. The primary outcome was patient survival. Secondary outcomes included graft survival and rejection incidence.

RESULTS

Thirty-three transplanted patients were compared to 71 patients waitlisted at our center and 66 patients from the UNOS database. Patients in the study group were transplanted 20.8 ± 16.1 months after listing. Patient survival was 87.8% at 6 months and 1 year and 71.4% at 3 years. Kidney transplantation was associated with a significant decrease in the risk of death after listing (HR: 0.22, CI: 0.11-0.45, P < .001).

CONCLUSION

With escalating life expectancy, kidney transplantation is a suitable treatment option in eligible octogenarians.