The Evolution of Redo Liver Transplantation Over 35 Years: Analysis of 654 Consecutive Adult Liver Retransplants at a Single Center.

OBJECTIVE: To examine liver retransplantation (ReLT) over 35 years at a single center. BACKGROUND: Despite the durability of liver transplantation (LT), graft failure affects up to 40% of LT recipients. METHODS: All adult ReLTs from 1984 to 2021 were analyzed. Comparisons were made between ReLTs in the pre versus post-model for end-stage liver disease (MELD) eras and between ReLTs and primary-LTs in the modern era. Multivariate analysis was used for prognostic modeling. RESULTS: Six hundred fifty-four ReLTs were performed in 590 recipients. There were 372 pre-MELD ReLTs and 282 post-MELD ReLTs. Of the ReLT recipients, 89% had one previous LT, whereas 11% had ≥2. Primary nonfunction was the most common indication in the pre-MELD era (33%) versus recurrent disease (24%) in the post-MELD era. Post-MELD ReLT recipients were older (53 vs 48, P = 0.001), had higher MELD scores (35 vs 31, P = 0.01), and had more comorbidities. However, post-MELD ReLT patients had superior 1, 5, and 10-year survival compared with pre-MELD ReLT (75%, 60%, and 43% vs 53%, 43%, and 35%, respectively, P < 0.001) and lower in-hospital mortality and rejection rates. Notably, in the post-MELD era, the MELD score did not affect survival. We identified the following risk factors for early mortality (≤12 months after ReLT): coronary artery disease, obesity, ventilatory support, older recipient age, and longer pre-ReLT hospital stay. CONCLUSIONS: This represents the largest single-center ReLT report to date. Despite the increased acuity and complexity of ReLT patients, post-MELD era outcomes have improved. With careful patient selection, these results support the efficacy and survival benefit of ReLT in an acuity-based allocation environment.

Absence of recipient C3aR1 signaling limits expansion and differentiation of alloreactive CD8+ T cell immunity and prolongs murine cardiac allograft survival.

Activation, differentiation, and expansion of alloreactive CD8+ T cells, the dominant effectors that mediate murine heart allograft rejection, requires allorecognition, costimulation, and cytokine-initiated signals. While previous work showed that alloreactive CD4+ T cell immunity entails immune cell-produced and locally activated complement, whether and how C3a receptor 1 (C3aR1) signaling impacts transplant outcomes and the mechanisms linking C3aR1 to alloreactive CD8+ T cell activation/expansion remain unclear. Herein we show that recipient C3aR1 deficiency or pharmacological C3aR1 blockade synergizes with tacrolimus to significantly prolong allograft survival versus tacrolimus-treated controls (median survival time 21 vs. 14 days, P < .05). Recipient C3aR1-deficiency reduced the frequencies of posttransplant, donor-reactive CD8+ T cells twofold. Reciprocal adoptive transfers of naive WT or C3ar1-/- CD8+ T cells into syngeneic WT or C3ar1-/- allograft recipients showed that T cell-expressed C3aR1 induces CD8+ T proliferation, mTOR activation and transcription factor T-bet expression. Host C3aR1 indirectly facilitates alloreactive CD8+ T cell proliferation/expansion by amplifying antigen presenting cell costimulatory molecule expression and innate cytokine production. In addition to expanding mechanistic insight, our findings identify C3aR1 as a testable therapeutic target for future studies aimed at improving human transplant outcomes.

Hypo-vascular hepatocellular carcinoma and liver transplantation: Morphological characteristics and implications on outcomes.

BACKGROUND: The clinical importance of hypovascular liver lesions in cirrhotic patients awaiting liver transplantation (LT) has not been fully investigated. The objective of this study was to characterize the clinicopathologic features and management of these tumors and to assess their impact on post-LT outcomes. METHODS: We performed a retrospective review of cirrhotic patients with lesions suspicious for hypovascular hepatocellular carcinoma (HCC) who underwent LT at a single institution from 2011- 2017. RESULTS: We identified 22 pre-LT patients with radiologic diagnosis of a lesion(s) suspicious for hypovascular HCC. There were 28 hypovascular lesions within the 22 patient cohort; 9 lesions (32%) converted to hypervascular HCC before LT and 19 lesions remained hypovascular at LT. 88% of hypovascular lesions were HCC on explant pathology. Compared to patients with hyper-vascular HCC lesions, hypovascular HCC lesions underwent less preoperative tumor ablation (58% vs 89%; P < .01). Hypovascular HCC were more likely to be well-differentiated (67% vs 11%; P < .01), but there were no differences in the microvascular invasion, tumor recurrence, or survival post-LT. CONCLUSIONS: Hypovascular HCC has similar clinical outcomes and needs for transplantation as hypervascular HCC. The high prevalence of HCC within suspicious hypovascular lesions supports a similar monitoring and locoregional therapy strategy as for hypervascular HCC.

Sucrose ingestion induces rapid AMPA receptor trafficking.

The mechanisms by which natural rewards such as sugar affect synaptic transmission and behavior are largely unexplored. Here, we investigate regulation of nucleus accumbens synapses by sucrose intake. Previous studies have shown that AMPA receptor (AMPAR) trafficking is a major mechanism for regulating synaptic strength, and that in vitro, trafficking of AMPARs containing the GluA1 subunit takes place by a two-step mechanism involving extrasynaptic and then synaptic receptor transport. We report that in rat, repeated daily ingestion of a 25% sucrose solution transiently elevated spontaneous locomotion and potentiated accumbens core synapses through incorporation of Ca(2+)-permeable AMPA receptors (CPARs), which are GluA1-containing, GluA2-lacking AMPARs. Electrophysiological, biochemical, and quantitative electron microscopy studies revealed that sucrose training (7 d) induced a stable (>24 h) intraspinous GluA1 population, and that in these rats a single sucrose stimulus rapidly (5 min) but transiently (<24 h) elevated GluA1 at extrasynaptic sites. CPARs and dopamine D1 receptors were required in vivo for elevated locomotion after sucrose ingestion. Significantly, a 7 d protocol of daily ingestion of a 3% solution of saccharin, a noncaloric sweetener, induced synaptic GluA1 similarly to 25% sucrose ingestion. These findings identify multistep GluA1 trafficking, previously described in vitro, as a mechanism for acute regulation of synaptic transmission in vivo by a natural orosensory reward. Trafficking is stimulated by a chemosensory pathway that is not dependent on the caloric value of sucrose.

Endogenous erythropoietin has immunoregulatory functions that limit the expression of autoimmune kidney disease in mice.

Background: Administration of recombinant erythropoietin (EPO), a kidney-produced hormone with erythropoietic functions, has been shown to have multiple immunoregulatory effects in mice and humans, but whether physiological levels of EPO regulate immune function in vivo has not been previously evaluated. Methods: We generated mice in which we could downregulate EPO production using a doxycycline (DOX)-inducible, EPO-specific silencing RNA (shEPOrtTAPOS), and we crossed them with B6.MRL-Faslpr/J mice that develop spontaneous lupus. We treated these B6.MRL/lpr shEPOrtTAPOS with DOX and serially measured anti-dsDNA antibodies, analyzed immune subsets by flow cytometry, and evaluated clinical signs of disease activity over 6 months of age in B6.MRL/lpr shEPOrtTAPOS and in congenic shEPOrtTANEG controls. Results: In B6.MRL/lpr mice, Epo downregulation augmented anti-dsDNA autoantibody levels and increased disease severity and percentages of germinal center B cells compared with controls. It also increased intracellular levels of IL-6 and MCP-1 in macrophages. Discussion: Our data in a murine model of lupus document that endogenous EPO reduces T- and B-cell activation and autoantibody production, supporting the conclusion that EPO physiologically acts as a counterregulatory mechanism to control immune homeostasis.

Linking erythropoietin to Treg-dependent allograft survival through myeloid cells.

Erythropoietin (EPO) has multiple nonerythropoietic functions, including immune modulation, but EPO's effects in transplantation remain incompletely understood. We tested the mechanisms linking EPO administration to prolongation of murine heterotopic heart transplantation using WT and conditional EPO receptor-knockout (EPOR-knockout) mice as recipients. In WT controls, peritransplant administration of EPO synergized with CTLA4-Ig to prolong allograft survival (P < 0.001), reduce frequencies of donor-reactive effector CD8+ T cells in the spleen (P < 0.001) and in the graft (P < 0.05), and increase frequencies and total numbers of donor-reactive Tregs (P < 0.01 for each) versus CTLA4-Ig alone. Studies performed in conditional EPOR-knockout recipients showed that each of these differences required EPOR expression in myeloid cells but not in T cells. Analysis of mRNA isolated from spleen monocytes showed that EPO/EPOR ligation upregulated macrophage-expressed, antiinflammatory, regulatory, and pro-efferocytosis genes and downregulated selected proinflammatory genes. Taken together, the data support the conclusion that EPO promotes Treg-dependent murine cardiac allograft survival by crucially altering the phenotype and function of macrophages. Coupled with our previous documentation that EPO promotes Treg expansion in humans, the data support the need for testing the addition of EPO to costimulatory blockade-containing immunosuppression regimens in an effort to prolong human transplant survival.

T cell-derived tumor necrosis factor induces cytotoxicity by activating RIPK1-dependent target cell death.

TNF ligation of TNF receptor 1 (TNFR1) promotes either inflammation and cell survival by (a) inhibiting RIPK1's death-signaling function and activating NF-κB or (b) causing RIPK1 to associate with the death-inducing signaling complex to initiate apoptosis or necroptosis. The cellular source of TNF that results in RIPK1-dependent cell death remains unclear. To address this, we employed in vitro systems and murine models of T cell-dependent transplant or tumor rejection in which target cell susceptibility to RIPK1-dependent cell death could be genetically altered. We show that TNF released by T cells is necessary and sufficient to activate RIPK1-dependent cell death in target cells and thereby mediate target cell cytolysis independently of T cell frequency. Activation of the RIPK1-dependent cell death program in target cells by T cell-derived TNF accelerates murine cardiac allograft rejection and synergizes with anti-PD1 administration to destroy checkpoint blockade-resistant murine melanoma. Together, the findings uncover a distinct immunological role for TNF released by cytotoxic effector T cells following cognate interactions with their antigenic targets. Manipulating T cell TNF and/or target cell susceptibility to RIPK1-dependent cell death can be exploited to either mitigate or augment T cell-dependent destruction of allografts and malignancies to improve outcomes.

Complement and Transplantation: From New Mechanisms to Potential Biomarkers and Novel Treatment Strategies.

The complement system, traditionally considered a component of innate immunity, is now recognized as a crucial mediator of the adaptive immune response in solid organ transplantation. Preclinical and early human trials have demonstrated the importance of complement effector mechanisms in driving allograft injury during specific antigraft immune responses, including ischemia-reperfusion injury, T-cell-mediated rejection, and antibody-mediated rejection, as well as a potential role for complement-derived risk stratification biomarkers. These data support the need for further testing of complement inhibitors in solid organ transplant recipients.

EndoVascular Occlusion and Tumor Excision (EVOTE): a Hybrid Approach to Small-Bowel Neuroendocrine Tumors with Mesenteric Metastases.

BACKGROUND: Mesenteric metastases from small-bowel neuroendocrine tumors (SBNETs) present a surgical challenge due to encasement of mesenteric vessels. In this study, we evaluate the feasibility and safety of a new, hybrid surgical approach to these mesenteric masses, EndoVascular Occlusion and Tumor Excision (EVOTE). METHODS: From 2014 to 2018, 13 patients underwent the EVOTE procedure after being referred to our institution for primary SBNETs with "unresectable" mesenteric metastases. During stage 1 of the hybrid EVOTE procedure, angiographic evaluation of the mesenteric mass is performed. If adequate collateralization is demonstrated, the encased mesenteric vessel(s) is embolized. Mass excision is performed the following day during stage 2 of the EVOTE procedure. RESULTS: Preoperative embolization was successful in 86% of cases; 2 cases were aborted for persistent abdominal pain following occlusion testing. Complete surgical excision of the mesenteric mass was achieved in 86% of cases. The 30-day overall morbidity and mortality rate was 29% and 0%, respectively. There was one local recurrence at 31.8 months post-op; this patient underwent a repeat EVOTE procedure with successful complete excision. DISCUSSION: EVOTE represents a new technique that aids in preoperative planning and surgical resection of SBNETs with mesenteric metastases.

Erythropoietin inhibits SGK1-dependent TH17 induction and TH17-dependent kidney disease.

IL-17-producing CD4+ cells (TH17) are pathogenically linked to autoimmunity including to autoimmune kidney disease. Erythropoietin's (EPO) newly recognized immunoregulatory functions and its predominant intra-renal source suggested that EPO physiologically regulates TH17 differentiation, thereby serving as a barrier to the development of autoimmune kidney disease. Using in vitro studies of human and murine cells and in vivo models, we show that EPO ligation of its receptor (EPO-R) on CD4+ T cells directly inhibits TH17 generation and promotes trans-differentiation of TH17 into IL-17-FOXP3+CD4+ T cells. Mechanistically, EPO/EPO-R ligation abrogates upregulation of SGK1 gene expression and blocks p38 activity to prevent SGK1 phosphorylation, thereby inhibiting RORC-mediated transcription of IL-17 and IL-23 receptor genes. In a murine model of TH17-dependent aristolochic acid (ArA)-induced, interstitial kidney disease associated with reduced renal EPO production, we demonstrate that transgenic EPO overexpression or recombinant EPO (rEPO) administration limits TH17 formation and clinical/histological disease expression. EPO/EPO-R ligations on CD4+ T cells abrogate, while absence of T cell-expressed EPO-R augments, TH17 induction and clinical/histological expression of pristane-induced glomerulonephritis (associated with decreased intrarenal EPO). rEPO prevents spontaneous glomerulonephritis and TH17 generation in MRL-lpr mice. Together, our findings indicate that EPO physiologically and therapeutically modulate TH17 cells to limit expression of TH17-associated autoimmune kidney disease.

Simultaneous vs Staged Cardiac Intervention in High-Acuity Liver Transplant.

This cohort study examines mortality, survival, and other outcomes among adults who underwent combined cardiac surgery and liver transplant, coronary revascularization prior to liver transplant, or isolated liver transplant.