Current Status of Renal Xenotransplantation and Next Steps.

Renal transplantation is the preferred treatment of ESKD, but the shortage of suitable donor kidneys from the cadaver pool means that many patients with ESKD will not receive a kidney transplant. Xenotransplantation has long represented a solution to the kidney shortage, but the occurrence of antibody-mediated rejection has precluded its clinical development. Developments in somatic cell nuclear transfer in pigs and gene editing tools have led to the creation of new donor pigs with greatly improved crossmatches to patients. In addition, improvements in preclinical kidney xenotransplant survival using new anti-CD40/CD154-based immunosuppression have pushed xenotransplantation to the point where it is reasonable to consider initiating a clinical trial to evaluate this potential therapy in patients.

Anti-C5 Antibody Tesidolumab Reduces Early Antibody-mediated Rejection and Prolongs Survival in Renal Xenotransplantation.

OBJECTIVE: Pig-to-primate renal xenotransplantation is plagued by early antibody-mediated graft loss which precludes clinical application of renal xenotransplantation. We evaluated whether temporary complement inhibition with anti-C5 antibody Tesidolumab could minimize the impact of early antibody-mediated rejection in rhesus monkeys receiving pig kidneys receiving costimulatory blockade-based immunosuppression. METHODS: Double (Gal and Sda) and triple xenoantigen (Gal, Sda, and SLA I) pigs were created using CRISPR/Cas. Kidneys from DKO and TKO pigs were transplanted into rhesus monkeys that had the least reactive crossmatches. Recipients received anti-C5 antibody weekly for 70 days, and T cell depletion, anti-CD154, mycophenolic acid, and steroids as baseline immunosuppression (n = 7). Control recipients did not receive anti-C5 therapy (n = 10). RESULTS: Temporary anti-C5 therapy reduced early graft loss secondary to antibody-mediated rejection and improved graft survival (P < 0.01). Deleting class I MHC (SLA I) in donor pigs did not ameliorate early antibody-mediated rejection (table). Anti-C5 therapy did not allow for the use of tacrolimus instead of anti-CD154 (table), prolonging survival to a maximum of 62 days. CONCLUSION: Inhibition of the C5 complement subunit prolongs renal xenotransplant survival in a pig to non-human primate model.

Long-term survival of pig-to-rhesus macaque renal xenografts is dependent on CD4 T cell depletion.

The shortage of available organs remains the greatest barrier to expanding access to transplant. Despite advances in genetic editing and immunosuppression, survival in experimental models of kidney xenotransplant has generally been limited to <100 days. We found that pretransplant selection of recipients with low titers of anti-pig antibodies significantly improved survival in a pig-to-rhesus macaque kidney transplant model (6 days vs median survival time 235 days). Immunosuppression included transient pan-T cell depletion and an anti-CD154-based maintenance regimen. Selective depletion of CD4+ T cells but not CD8+ T cells resulted in long-term survival (median survival time >400 days vs 6 days). These studies suggested that CD4+ T cells may have a more prominent role in xenograft rejection compared with CD8+ T cells. Although animals that received selective depletion of CD8+ T cells showed signs of early cellular rejection (marked CD4+ infiltrates), animals receiving selective CD4+ depletion exhibited normal biopsy results until late, when signs of chronic antibody rejection were present. In vitro study results suggested that rhesus CD4+ T cells required the presence of SLA class II to mount an effective proliferative response. The combination of low pretransplant anti-pig antibody and CD4 depletion resulted in consistent, long-term xenograft survival.

Lysophospholipid variants in hepatocellular carcinoma.

BACKGROUND: The U.S. incidence of hepatocellular carcinoma (HCC) is increasing and is linked to hepatitis C (HepC) infection, alcohol toxicity, and obesity. This manuscript examines lysophosphatidic acid (LPA) variant biosynthesis as a biomarker and potential therapeutic target for HCC. METHODS: Serum LPA variant levels were determined in patients with HepC ± HCC, alcoholic cirrhosis ± HCC, or nonalcoholic steatohepatitis ± HCC by mass spectroscopy. To clarify the relationship between cancer and LPA variant profiles, LPA variants were evaluated in HepC + HCC patients before and after liver transplantation. Moreover, LPA variant modification of gene expression was also determined in vitro by real-time polymerase chain reaction. RESULTS: In patients diagnosed with HCC, 18:2 LPA biosynthesis was decreased, whereas 20:4 LPA biosynthesis and 20:4 LPA:18:2 LPA ratio were increased. Three days after liver transplantation, serum LPA levels and 18:2 LPA:20:4 LPA ratio were significantly reduced in patients with cancer. The 20:4 LPA selectively stimulated LPA receptor and tumor necrosis factor α expression in Hep3B cells, whereas 18:2 LPA did not. CONCLUSIONS: Serum LPA variant profiles are unique in patients with HCC allowing for the stratification of patients. Moreover, LPA variants impart individual mitogenic properties associated with tumorigenesis that may provide a potential therapeutic target. We envision that LPA profiling may accelerate diagnosis, help stratify patients at high risk of developing cancer, and provide potential targets for chemoprevention.

Staphylococcus epidermidis colonization is highly clonal across US cardiac centers.

BACKGROUND: Little is known about the clonality of Staphylococcus epidermidis in the United States, although it is the predominant pathogen in infections involving prosthetic materials, including ventricular assist devices (VADs). METHODS: Seventy-five VAD recipients at 4 geographically diverse US cardiac centers were prospectively followed up to 1 year of VAD support. The anterior nares, sternum, and (future) driveline exit site were cultured for S. epidermidis before VAD insertion and at 7 times after surgery. Infection isolates were also collected. Isolates were typed by pulsed-field gel electrophoresis. A subset underwent susceptibility testing and staphylococcal chromosomal cassette mec and multilocus sequence typing. RESULTS: A total of 1559 cultures yielded 565 S. epidermidis isolates; 254 of 548 typed isolates (46%) belonged to 1 of 7 clonal types as defined by pulsed-field gel electrophoresis. These clones were identified in up to 27 people distributed across all 4 cardiac centers. They caused 3 of 6 VAD-related infections. Disseminated clones were more antibiotic resistant than were less prevalent isolates (eg, 79% vs 54% methicillin resistant; P = .0021). CONCLUSIONS: This study revealed that healthcare-associated S. epidermidis infection is remarkably clonal. We describe S. epidermidis clones that are highly resistant to antibiotics distributed across US cardiac centers. These clones may have determinants that enhance transmissibility, persistence, or invasiveness. Clinical Trials Registration. NCT01471795.

Outcomes of a multicenter trial of the Levitronix CentriMag ventricular assist system for short-term circulatory support.

OBJECTIVE: The Levitronix CentriMag (Levitronix LLC, Waltham, Mass) ventricular assist system is designed for temporary left, right, or biventricular support. Advantages include ease of use, excellent reliability, and low thrombosis risk,. which may allow wider application of short-term support and improved outcomes in patients with cardiogenic shock. This multi-institutional study evaluated safety, effectiveness, and outcomes of the CentriMag in patients with cardiogenic shock. METHODS: Thirty-eight patients were supported at 7 centers. Patients included 12 after cardiotomy, 14 after myocardial infarction, and 12 with right ventricular failure after implantable left ventricular assist device placement. Devices were implanted in left (n = 8), right (n = 12), or biventricular (n = 18) configuration. Support was continued until recovery, transplantation, or implantation of long-term ventricular assist device. RESULTS: Mean support duration for the entire cohort (n = 38) was 13 days (1-60 days), with 47% of patients (18/38) surviving 30 days after device removal. Mean CentriMag biventricular support (n = 18) duration was 15 days (1-60 days), with 44% (8/18) surviving at 30 days. Mean CentriMag right ventricular support with a commercially available left ventricular assist device (n = 12) duration was 14 days (1-29 days), with 58% (7/12) surviving at 30 days. Complications included bleeding (21%), infection (5%), respiratory failure (3%), hemolysis (5%), and neurologic dysfunction (11%). There were no CentriMag or pump failures. CONCLUSIONS: In this preliminary study, the CentriMag provided short-term support for patients with cardiogenic shock with a low incidence of device-related complications and no device failures.

Positive heparin-platelet factor 4 antibody complex and cardiac surgical outcomes.

BACKGROUND: Given the large number of patients undergoing cardiac operations annually, it is important to identify populations at high risk for adverse outcomes. This observational study was conducted to determine the incidence of preoperative heparin-platelet factor 4 (HPF4) antibodies and to assess the associated risk of postoperative adverse outcomes in a nonselected cardiac surgery patient population. METHODS: Between March 2002 and December 2004, 1114 (92%) of 1209 patients undergoing cardiac surgery with heparin were tested in an unselected manner for HPF4 antibodies. Main outcome measures were HPF4 antibody seropositivity and fatal and nonfatal adverse clinical outcomes after cardiac surgery. RESULTS: Of those screened, 60 (5.4%) of 1114 had positive HPF4 antibodies preoperatively. These patients had longer mean postoperative length of stay (14.0 days versus 9.8 days, p = 0.05), a higher incidence of prolonged (> or = 96 hours) mechanical ventilation (20.3% versus 9.2%, p = 0.02), acute limb ischemia (5.1% versus 0.9%, p = 0.03), renal complications including dialysis (20.3% versus 10.5%, p = 0.03), and gastrointestinal complications (15.3% versus 5.9%, p = 0.01). Stepwise logistic regression analysis showed positive HPF4 antibody status to be an independent predictor for adverse outcome and was associated with a higher risk for renal complications, including dialysis (adjusted odds ratio 2.2; 95% confidence interval, 1.1 to 4.3), than was diabetes. CONCLUSIONS: In this large patient series, the presence of HPF4 antibodies before surgical heparin administration was an independent and clinically significant risk factor for postoperative adverse events after cardiac surgery. An optimal preoperative cardiac surgery risk profile should include HPF4 antibody status.

Evolution of a pheochromocytoma.

OBJECTIVE: To present a case that demonstrates the evolution of a pheochromocytoma over a several-year period and to emphasize the importance of a thorough work-up for pheochromocytoma in patients with neurofibromatosis type 1 (NF1) and hypertension. METHODS: We review the long-term clinical, biochemical, and imaging findings in a man with a complex medical history of hypertension, NF1, and cardiomyopathy. RESULTS: A 44-year-old man, with a well-documented history of headaches, hypertension, and NF1, was referred for evaluation of a right adrenal enlargement. He had developed cardiomyopathy and undergone an evaluation for cardiac transplantation. Initial computed tomography revealed subtle asymmetry in the upper right adrenal gland. Biochemical studies for pheochromocytoma yielded equivocal findings, with a 1.5-fold elevation in the urinary norepinephrine and near-normal urinary metanephrine level. Because 131I-metaiodobenzylguanidine imaging showed no tracer uptake in the area of the right adrenal gland, the patient was thought not to have a pheochromocytoma. The patient eventually underwent cardiac transplantation and did well. On reassessment 3 1/2 years later, he was found to have a larger right adrenal mass. The second endocrine evaluation demonstrated substantial elevation in the urinary metanephrine level, and the patient underwent laparoscopic right adrenalectomy to remove the tumor (3.5 by 3.0 by 2.5 cm), which proved to be a pheochromocytoma. CONCLUSION: This case shows that a pheochromocytoma can be difficult to diagnose and can evolve to become a large, biochemically active tumor. It is imperative that patients with an adrenal tumor undergo periodic reevaluation to ensure that the tumor remains stable in size. If the tumor enlarges, further biochemical testing is warranted.

Comparison of Novacor and HeartMate vented electric left ventricular assist devices in a single institution.

We compared the survival outcomes, left ventricular assist device (LVAD)-related hospitalization, stroke, infection, panel reactive antibody, and blood product use data among 13 Novacor and 51 HeartMate system recipients. Stroke was significantly higher in Novacor patients, as was blood product use at the time of heart transplantation, likely due to long-term anti-coagulation, while the LVAD-related hospitalization and infections did not differ between the 2 groups. A positive panel reactive antibody was seen more among the HeartMate patients, but did not have a significant clinical impact and may not represent a true allosensitization.

CTLA-4 is important in maintaining long-term survival of cardiac allografts.

INTRODUCTION: CTLA-4 is a negative regulatory molecule upregulated on activated T cells; however, its role in induction and maintenance of transplant tolerance is not well understood. METHODS: The characteristics and effects of a novel mouse anti-rat CTLA-4 antibody (Ab) (242B58) were examined using fluorescence-activated cell sorter, mixed lymphocyte reaction, enzyme-linked immunospot, signaling studies, and a rat model of cardiac transplant tolerance induced by administration of anti-CD28 Ab and cyclosporine. RESULTS: The anti-CTLA4 Ab was shown to bind to CTLA-4 but not prevent subsequent binding of B7 to CTLA-4. Binding to CTLA-4 did not result in phosphorylation of early cytoplasmic tyrosine kinases, suggesting that this is not a signaling Ab. However, its in vitro function was compatible with antagonization of the effects of CTLA-4, thereby increasing T-cell proliferation and interferon-gamma production in mixed lymphocyte reaction and enzyme-linked immunospot assays, respectively. Administration of 242B58 to animals treated with anti-CD28 Ab and cyclosporine either at the time of transplantation or various time-points up to 33 days posttransplantation did not result in immediate rejection, but rather caused a delayed severe acute allograft rejection at approximately 45 days posttransplant. CONCLUSIONS: Our results seem to be a reflection of the unique properties of the 242B58 Ab, which does not antagonize B7 binding to CTLA-4 and affect its ability to out-compete CD28 for B7 binding. It does, however, seem to interfere with CTLA-4 signaling, suggesting that competition for B7 may be important in induction of tolerance, but signaling through CTLA-4 is more important in maintaining a tolerant phenotype.

Left ventricular assist device performance with long-term circulatory support: lessons from the REMATCH trial.

BACKGROUND: Left ventricular assist device (LVAD) failure and malfunction rates are critical gauges for establishing LVADs as a long-term therapy for end-stage heart failure patients. These device performance measures, however, have been inadequately characterized in the bridge-to-transplantation literature. METHODS: REMATCH is a randomized trial that compares optimal medical management with LVAD implantation for patients with end-stage heart failure. An independent committee adjudicated patient outcomes. The primary endpoint--survival--was analyzed by intention to treat using the log-rank statistic. Frequency of event occurrence was analyzed by Poisson regression. The time to first event was analyzed by the product limit method. Device performance was disaggregated into confirmed malfunctions and system failures. The latter were events in which patients could not be rescued with backup circulatory support measures. RESULTS: The 1-year survival rate was 52% (95% confidence limit [CL]; 40%-63%) for LVAD patients versus 28% (95% CL; 17%-39%) for medical patients and the 2-year survival rate was 29% (95% CL; 19%-40%) for LVAD patients versus 13% (95% CL; 5%-22%) for medical patients. System failure was 0.13 per patient per year and the confirmed LVAD malfunction rate was 0.90. Freedom from device replacement was 87% at 1 year and 37% at 2 years. CONCLUSIONS: Despite the observed rates of device malfunction and replacement, LVAD implantation confers clinically significant improvement with regard to survival as compared with medical management. Device modifications and innovations for infection management exhibit great promise of improving device performance in the near future.

TECHNICAL CONSIDERATIONS IN CANNULATING THE ASCENDING AORTA.

A successfully used technique of aortic arch cannulation is reported. This cannula is inexpensive and can be made easily in the hospital. The position and advantages of the cannula are discussed.

LEFT MAIN CORONARY ARTERY OCCLUSION: SURGICAL MANAGEMENT.

Left main coronary occlusion is a rare lesion. A case that was successfully managed by coronary bypass surgery is presented. Occlusion of the left main coronary artery and management of left main coronary artery disease is discussed.