Early Single Center Experience with an Ex Vivo Organ Care System in Pediatric Heart Transplantation.

Pediatric heart transplantation (HTx) faces challenges such as limited donor availability and the need for complex reconstructions, particularly in patients with congenital anomalies. Ex vivo perfusion offers a promising approach to minimize graft ischemic time and potentially expand the donor pool. We report our single-center experience using the TransMedics Organ Care System (OCS) for ex vivo perfusion in pediatric HTx. From 2020-2024, eight pediatric patients received OCS-perfused donor hearts. Median recipient age was 13 years (range 9-18), and median weight was 58.8 kg (33.2-127.8). Indications for HTx included dilated cardiomyopathy (n=4), hypertrophic cardiomyopathy (n=1), graft vasculopathy (n=1), and Fontan failure (n=2). Median OCS time was 273 minutes (195-328), and recipient ischemic time was 85 minutes (64-139). Post-transplant, all patients had normal LV function at discharge. Over a median follow-up of 11.9 months, there were no deaths. These findings suggest that ex vivo perfusion is a valuable technique in pediatric HTx.

Aberrant right subclavian artery intervention can provide relief of dysphagia.

BACKGROUND: An aberrant right subclavian artery represents the most common aortic arch vascular anomaly. Conventional wisdom states that these anomalies do not result in dysphagia, but rather serve as "red herrings". Clearly, in the vast majority of cases, this holds true. Nonetheless, one should never say never. METHODS: Herein, we present a cohort of four children with debilitating dysphagia resulting from an aberrant right subclavian artery. Subclavian reimplantation via a right posterolateral thoracotomy was performed successfully in all cases. RESULTS: Dysphagia resolved postoperatively, and all patients were able to advance to a normal diet. They were able to gain appropriate weight postoperatively and continue to do well at most recent clinical follow-up. CONCLUSIONS: This case series suggests that aberrant right subclavian artery anatomy should be considered a potential aetiology of dysphagia, albeit rarely. Surgical intervention for select patients can provide dramatic resolution of symptoms.

Surgical Protocol for Partial Heart Transplantation in Growing Piglets.

Partial heart transplantation is a new approach to deliver growing heart valve implants. Partial heart transplants differ from heart transplants because only the part of the heart containing the necessary heart valve is transplanted. This allows partial heart transplants to grow, similar to the valves in heart transplants. However, the transplant biology of partial heart transplantation remains unexplored. This is a critical barrier to progress of the field. Without knowledge about the specific transplant biology of partial heart transplantation, children with partial heart transplants are empirically treated like children with heart transplants because the valves in heart transplants are known to grow. In order to progress the field, an animal model for partial heart transplantation is necessary. Here, we contribute our surgical protocol for partial heart transplantation in growing piglets. All aspects of partial heart transplantation, including the donor procedure, the recipient procedure, and recipient perioperative care are described in detail. There are important nuances in the conduct of virtually all aspects of open heart surgery that differs in piglets from humans. Our surgical protocol, which is based on our experience with 34 piglets, will allow other investigators to leverage our experience to seek fundamental knowledge about the nature of partial heart transplants. This is significant because the partial heart transplant model in piglets is complex and very resource intensive.

Survival after partial heart transplantation in a piglet model.

Partial heart transplantation (PHT) is a novel surgical approach that involves transplantation of only the part of the heart containing a valve. The rationale for this approach is to deliver growing heart valve implants that reduce the need for future re-operations in children. However, prior to clinical application of this approach, it was important to assess it in a preclinical model. To investigate PHT short-term outcomes and safety, we performed PHT in a piglet model. Yorkshire piglets (n = 14) were used for PHT of the pulmonary valve. Donor and recipient pairs were matched based on blood types. The piglets underwent PHT at an average age of 44 days (range 34-53). Post-operatively, the piglets were monitored for a period of two months. Of the 7 recipient piglets, one mortality occurred secondary to anesthesia complications while undergoing a routine echocardiogram on post-operative day 19. All piglets had appropriate weight gain and laboratory findings throughout the post-operative period indicating a general state of good health and rehabilitation after undergoing PHT. We conclude that PHT has good short-term survival in the swine model. PHT appears to be safe for clinical application.

Semilunar valve growth and function 10 years after infant heart transplantation: Predicting long-term outcomes of partial heart transplants.

INTRODUCTION: Partial heart transplants are a new type of pediatric transplant that replace defective heart valves with the parts of matched donor hearts containing the necessary valves. Short-term outcomes of partial heart transplants are excellent, but long-term outcomes are unknown. In order to predict the long-term outcomes of partial heart transplants, we evaluated long-term growth and function of semilunar heart valves transplanted in infancy as part of a heart transplant. METHODS: All children who underwent infant heart transplantation at a single center from 1997 to 2014 were included in this study. Children in whom echocardiograms after heart transplantation and after 10 years were not available for review were excluded. The echocardiograms were reviewed by two authors to analyze semilunar valve annulus diameters, Z-scores, peak valve gradients, and valve regurgitation. Statistical difference was determined using two-tailed, paired sample t-tests with Bonferroni correction for multiple comparisons. RESULTS: Data from 15 patients were analyzed. The aortic valve annulus averaged 1.3 cm (range 0.7-1.8 cm) immediately after transplantation and grew to an average of 1.7 cm (range 1.4-2.3 cm) after 10 years (p < .001). After 10 years, the aortic valve peak gradient avereraged 5.1 mmHg (range 2.1-15.5 mmHg) and none of the valves had more than trivial regurgitation. The pulmonary valve annulus averaged 1.5 cm (range 1.1-2.5 cm) immediately after transplantation and grew to an average of 2.1 cm (range 1.0-2.9 cm) after 10 years (p < .001). After 10 years, the pulmonary valve peak gradient averaged 4.3 mmHg (range 1.1-13.8 mmHg), and 7% of valves had moderate regurgitation. DISCUSSION: Semilunar heart valves transplanted in infancy as part of a heart transplant demonstrate statistically significant growth and excellent function after 10 years. This predicts excellent long-term outcomes of partial heart transplants.

Comparing Survival After Resection, Ablation, and Radiation in Small Intrahepatic Cholangiocarcinoma.

BACKGROUND: Hepatectomy is the cornerstone of curative-intent treatment for intrahepatic cholangiocarcinoma (ICC). However, in patients unable to be resected, data comparing efficacy of alternatives including thermal ablation and radiation therapy (RT) remain limited. Herein, we compared survival between resection and other liver-directed therapies for small ICC within a national cancer registry. PATIENTS AND METHODS: Patients with clinical stage I-III ICC < 3 cm diagnosed 2010-2018 who underwent resection, ablation, or RT were identified in the National Cancer Database. Overall survival (OS) was compared using Kaplan-Meier and multivariable Cox proportional hazards methods. RESULTS: Of 545 patients, 297 (54.5%) underwent resection, 114 (20.9%) ablation, and 134 (24.6%) RT. Median OS was similar between resection and ablation [50.5 months, 95% confidence interval (CI) 37.5-73.9; 39.5 months, 95% CI 28.7-58.4, p = 0.14], both exceeding that of RT (20.9 months, 95% CI 14.1-28.3). RT patients had high rates of stage III disease (10.4% RT vs. 1.8% ablation vs. 11.8% resection, p < 0.001), but the lowest rates of chemotherapy utilization (9.0% RT vs. 15.8% ablation vs. 38.7% resection, p < 0.001). In multivariable analysis, resection and ablation were associated with reduced mortality compared with RT [hazard ratio (HR) 0.44, 95% CI 0.33-0.58 and HR 0.53, 95% CI 0.38-0.75, p < 0.001, respectively]. CONCLUSION: Resection and ablation were associated with improved survival in patients with ICC < 3 cm compared with RT. Acknowledging confounders, anatomic constraints of ablation, limitations of available data, and need for prospective study, these results favor ablation in small ICC where resection is not feasible.

Colorectal Cancer Liver Metastases: Multimodal Therapy.

Despite a steady decline in incidence and mortality rates, colorectal cancer (CRC) remains the second most common cancer diagnosis in women and the third most common in men worldwide. Notably, the liver is recognized as the most common site of CRC metastasis, and metastases to the liver remain the primary driver of disease-specific mortality for patients with CRC. Although hepatic resection is the backbone of curative-intent treatment, management of CRLM has become increasingly multimodal during the last decade and includes the use of downstaging chemotherapy, ablation techniques, and locoregional therapy, each of which are reviewed herein.

BTLA+CD200+ B cells dictate the divergent immune landscape and immunotherapeutic resistance in metastatic vs. primary pancreatic cancer.

Response to cancer immunotherapy in primary versus metastatic disease has not been well-studied. We found primary pancreatic ductal adenocarcinoma (PDA) is responsive to diverse immunotherapies whereas liver metastases are resistant. We discovered divergent immune landscapes in each compartment. Compared to primary tumor, liver metastases in both mice and humans are infiltrated by highly anergic T cells and MHCIIloIL10+ macrophages that are unable to present tumor-antigen. Moreover, a distinctive population of CD24+CD44-CD40- B cells dominate liver metastases. These B cells are recruited to the metastatic milieu by Muc1hiIL18hi tumor cells, which are enriched >10-fold in liver metastases. Recruited B cells drive macrophage-mediated adaptive immune-tolerance via CD200 and BTLA. Depleting B cells or targeting CD200/BTLA enhanced macrophage and T-cell immunogenicity and enabled immunotherapeutic efficacy of liver metastases. Our data detail the mechanistic underpinnings for compartment-specific immunotherapy-responsiveness and suggest that primary PDA models are poor surrogates for evaluating immunity in advanced disease.

Intrahepatic microbes govern liver immunity by programming NKT cells.

The gut microbiome shapes local and systemic immunity. The liver is presumed to be a protected sterile site. As such, a hepatic microbiome has not been examined. Here, we showed a liver microbiome in mice and humans that is distinct from that of the gut and is enriched in Proteobacteria. It undergoes dynamic alterations with age and is influenced by the environment and host physiology. Fecal microbial transfer experiments revealed that the liver microbiome is populated from the gut in a highly selective manner. Hepatic immunity is dependent on the microbiome, specifically the bacteroidetes species. Targeting bacteroidetes with oral antibiotics reduced hepatic immune cells by approximately 90%, prevented antigen-presenting cell (APC) maturation, and mitigated adaptive immunity. Mechanistically, our findings are consistent with presentation of bacteroidetes-derived glycosphingolipids to NKT cells promoting CCL5 signaling, which drives hepatic leukocyte expansion and activation, among other possible host-microbe interactions. Collectively, we reveal a microbial/glycosphingolipid/NKT/CCL5 axis that underlies hepatic immunity.

Targeting Piezo1 unleashes innate immunity against cancer and infectious disease.

Piezo1 is a mechanosensitive ion channel that has gained recognition for its role in regulating diverse physiological processes. However, the influence of Piezo1 in inflammatory disease, including infection and tumor immunity, is not well studied. We postulated that Piezo1 links physical forces to immune regulation in myeloid cells. We found signal transduction via Piezo1 in myeloid cells and established this channel as the primary sensor of mechanical stress in these cells. Global inhibition of Piezo1 with a peptide inhibitor was protective against both cancer and septic shock and resulted in a diminution in suppressive myeloid cells. Moreover, deletion of Piezo1 in myeloid cells protected against cancer and increased survival in polymicrobial sepsis. Mechanistically, we show that mechanical stimulation promotes Piezo1-dependent myeloid cell expansion by suppressing the retinoblastoma gene Rb1 We further show that Piezo1-mediated silencing of Rb1 is regulated via up-regulation of histone deacetylase 2. Collectively, our work uncovers Piezo1 as a targetable immune checkpoint that drives immunosuppressive myelopoiesis in cancer and infectious disease.

Regulatory T Cells Keep Pancreatic Cancer at Bay.

Although CD4+ FOXP3+ T regulatory (Treg) cells are well-known mediators of immunologic tolerance, their influences in the tumor microenviroment are incompletely understood. Writing in this issue of Cancer Discovery, Zhang and colleagues demonstrate that in pancreatic cancer, Treg cells promote the differentiation of tumor-restraining myofibroblastic cancer-associated fibroblasts, challenging the existing notion that Treg cells enable tumor progression.See related article by Zhang et al., p. 422.

PD-L1 engagement on T cells promotes self-tolerance and suppression of neighboring macrophages and effector T cells in cancer.

Programmed cell death protein 1 (PD-1) ligation delimits immunogenic responses in T cells. However, the consequences of programmed cell death 1 ligand 1 (PD-L1) ligation in T cells are uncertain. We found that T cell expression of PD-L1 in cancer was regulated by tumor antigen and sterile inflammatory cues. PD-L1+ T cells exerted tumor-promoting tolerance via three distinct mechanisms: (1) binding of PD-L1 induced STAT3-dependent 'back-signaling' in CD4+ T cells, which prevented activation, reduced TH1-polarization and directed TH17-differentiation. PD-L1 signaling also induced an anergic T-bet-IFN-γ- phenotype in CD8+ T cells and was equally suppressive compared to PD-1 signaling; (2) PD-L1+ T cells restrained effector T cells via the canonical PD-L1-PD-1 axis and were sufficient to accelerate tumorigenesis, even in the absence of endogenous PD-L1; (3) PD-L1+ T cells engaged PD-1+ macrophages, inducing an alternative M2-like program, which had crippling effects on adaptive antitumor immunity. Collectively, we demonstrate that PD-L1+ T cells have diverse tolerogenic effects on tumor immunity.

γδ T Cells Promote Steatohepatitis by Orchestrating Innate and Adaptive Immune Programming.

BACKGROUND AND AIMS: The recruitment and activation of inflammatory cells in the liver delineates the transition from hepatic steatosis to steatohepatitis (SH). APPROACH AND RESULTS: We found that in SH, γδT cells are recruited to the liver by C-C chemokine receptor (CCR) 2, CCR5, and nucleotide-binding oligomerization domain-containing protein 2 signaling and are skewed toward an interleukin (IL)-17A+ phenotype in an inducible costimulator (ICOS)/ICOS ligand-dependent manner. γδT cells exhibit a distinct Vγ4+ , PD1+ , Ly6C+ CD44+ phenotype in SH. Moreover, γδT cells up-regulate both CD1d, which is necessary for lipid-based antigens presentation, and the free fatty acid receptor, CD36. γδT cells are stimulated to express IL-17A by palmitic acid and CD1d ligation. Deletion, depletion, and targeted interruption of γδT cell recruitment protects against diet-induced SH and accelerates disease resolution. CONCLUSIONS: We demonstrate that hepatic γδT cells exacerbate SH, independent of IL-17 expression, by mitigating conventional CD4+ T-cell expansion and modulating their inflammatory program by CD1d-dependent vascular endothelial growth factor expression.

The fungal mycobiome promotes pancreatic oncogenesis via activation of MBL.

Bacterial dysbiosis accompanies carcinogenesis in malignancies such as colon and liver cancer, and has recently been implicated in the pathogenesis of pancreatic ductal adenocarcinoma (PDA)1. However, the mycobiome has not been clearly implicated in tumorigenesis. Here we show that fungi migrate from the gut lumen to the pancreas, and that this is implicated in the pathogenesis of PDA. PDA tumours in humans and mouse models of this cancer displayed an increase in fungi of about 3,000-fold compared to normal pancreatic tissue. The composition of the mycobiome of PDA tumours was distinct from that of the gut or normal pancreas on the basis of alpha- and beta-diversity indices. Specifically, the fungal community that infiltrated PDA tumours was markedly enriched for Malassezia spp. in both mice and humans. Ablation of the mycobiome was protective against tumour growth in slowly progressive and invasive models of PDA, and repopulation with a Malassezia species-but not species in the genera Candida, Saccharomyces or Aspergillus-accelerated oncogenesis. We also discovered that ligation of mannose-binding lectin (MBL), which binds to glycans of the fungal wall to activate the complement cascade, was required for oncogenic progression, whereas deletion of MBL or C3 in the extratumoral compartment-or knockdown of C3aR in tumour cells-were both protective against tumour growth. In addition, reprogramming of the mycobiome did not alter the progression of PDA in Mbl- (also known as Mbl2) or C3-deficient mice. Collectively, our work shows that pathogenic fungi promote PDA by driving the complement cascade through the activation of MBL.