Combined heart and liver transplantation in a patient supported by left ventricular assist device (LVAD) with propionic acidemia.

Propionic acidemia (PA) is a rare inherited metabolic disease due to inborn errors of metabolism. PA results in the accumulation of abnormal organic acid metabolites in multiple systems, mainly the central nervous system and the heart. Cardiac complications include dilated cardiomyopathy (DCM) and carry a 40-50% increased mortality risk. Liver transplantation (LT) is required in PA patients when medical treatment fails and may prevent or slow down the cardiomyopathy progression. However, severe heart disease may be a serious contraindication to LT. We present a complicated case of a PA patient, supported with a Left Ventricular Assist Device, who underwent a heart and Liver transplant. PA patients are at increased risk for metabolic acidosis during surgery, with increased anion gap and hyperammonemia. A strict multi-disciplinary approach is needed to prevent and treat metabolic decompensation. The patient had a successful heart and liver transplant after a strict treatment protocol in the pre, intra, and post-operative periods. His case highlights the complexity of PA patients and the increased risk for metabolic decompensation during surgery and provides an insight into how to manage such complicated patients.

A Consortium for Analytic Standardization in Immunohistochemistry.

CONTEXT.­: The authors announce the launch of the Consortium for Analytic Standardization in Immunohistochemistry, funded with a grant from the National Cancer Institute. As with other laboratory testing, analytic standards are important for many different stakeholders: commercial vendors of instruments and reagents, biopharmaceutical firms, pathologists, scientists, clinical laboratories, external quality assurance organizations, and regulatory bodies. Analytic standards are customarily central to assay development, validation, and method transfer into routine assays and are critical quality assurance tools. OBJECTIVE.­: To improve immunohistochemistry (IHC) test accuracy and reproducibility by integrating analytic standards into routine practice. To accomplish this mission, the consortium has 2 mandates: (1) to experimentally determine analytic sensitivity thresholds (lower and upper limits of detection) for selected IHC assays, and (2) to inform IHC stakeholders of what analytic standards are, why they are important, and how and for what purpose they are used. The consortium will then publish the data and offer analytic sensitivity recommendations where appropriate. These mandates will be conducted in collaboration and coordination with clinical laboratories, external quality assurance programs, and pathology organizations. DATA SOURCES.­: Literature review and published external quality assurance data. CONCLUSIONS.­: Integration of analytic standards is expected to (1) harmonize and standardize IHC assays; (2) improve IHC test accuracy and reproducibility, both within and between laboratories; and (3) dramatically simplify and improve methodology transfer for new IHC protocols from published literature or clinical trials to clinical IHC laboratories.

Portal Hypertension, Nodular Regenerative Hyperplasia of the Liver, and Obstructive Portal Venopathy due to Metastatic Breast Cancer.

Nodular regenerative hyperplasia (NRH) of the liver is associated with noncirrhotic portal hypertension, rheumatologic and hematologic disorders, administration of certain drugs, and other underlying conditions. This report describes a 64-year-old man with clinically presumed cirrhosis who presented to our institution with coffee-ground emesis, esophageal varices, ascites, and encephalopathy. Eleven years earlier he had been treated for breast cancer with mastectomy and chemo-radiotherapy. He died suddenly, and the autopsy showed no evidence of cirrhosis but instead demonstrated NRH with extensive emboli of recurrent breast carcinoma within the portal vein and its intrahepatic branches. Neoplastic occlusion of the portal vein as a cause of presinusoidal noncirrhotic portal hypertension has not previously been reported for metastatic breast carcinoma. This case highlights the importance of obstructive portal venopathy in the pathogenesis of NRH as well as the diagnostic difficulties that may be encountered in determining the cause of portal hypertension.

Epicardial border zone overexpression of skeletal muscle sodium channel SkM1 normalizes activation, preserves conduction, and suppresses ventricular arrhythmia: an in silico, in vivo, in vitro study.

BACKGROUND: In depolarized myocardial infarct epicardial border zones, the cardiac sodium channel (SCN5A) is largely inactivated, contributing to low action potential upstroke velocity (V(max)), slow conduction, and reentry. We hypothesized that a fast inward current such as the skeletal muscle sodium channel (SkM1) operating more effectively at depolarized membrane potentials might restore fast conduction in epicardial border zones and be antiarrhythmic. METHODS AND RESULTS: Computer simulations were done with a modified Hund-Rudy model. Canine myocardial infarcts were created by coronary ligation. Adenovirus expressing SkM1 and green fluorescent protein or green fluorescent protein alone (sham) was injected into epicardial border zones. After 5 to 7 days, dogs were studied with epicardial mapping, programmed premature stimulation in vivo, and cellular electrophysiology in vitro. Infarct size was determined, and tissues were immunostained for SkM1 and green fluorescent protein. In the computational model, modest SkM1 expression preserved fast conduction at potentials as positive as -60 mV; overexpression of SCN5A did not. In vivo epicardial border zone electrograms were broad and fragmented in shams (31.5 +/- 2.3 ms) and narrower in SkM1 (22.6 +/- 2.8 ms; P=0.03). Premature stimulation induced ventricular tachyarrhythmia/fibrillation >60 seconds in 6 of 8 shams versus 2 of 12 SkM1 (P=0.02). Microelectrode studies of epicardial border zones from SkM1 showed membrane potentials equal to that of shams and V(max) greater than that of shams as membrane potential depolarized (P<0.01). Infarct sizes were similar (sham, 30 +/- 2.8%; SkM1, 30 +/- 2.6%; P=0.86). SkM1 expression in injected epicardium was confirmed immunohistochemically. CONCLUSIONS: SkM1 increases V(max) of depolarized myocardium and reduces the incidence of inducible sustained ventricular tachyarrhythmia/fibrillation in canine infarcts. Gene therapy to normalize activation by increasing V(max) at depolarized potentials may be a promising antiarrhythmic strategy.

Xenografted adult human mesenchymal stem cells provide a platform for sustained biological pacemaker function in canine heart.

BACKGROUND: Biological pacemaking has been performed with viral vectors, human embryonic stem cells, and adult human mesenchymal stem cells (hMSCs) as delivery systems. Only with human embryonic stem cells are data available regarding stability for >2 to 3 weeks, and here, immunosuppression has been used to facilitate survival of xenografts. The purpose of the present study was to determine whether hMSCs provide stable impulse initiation over 6 weeks without the use of immunosuppression, the "dose" of hMSCs that ensures function over this period, and the catecholamine responsiveness of hMSC-packaged pacemakers. METHODS AND RESULTS: A full-length mHCN2 cDNA subcloned in a pIRES2-EGFP vector was electroporated into hMSCs. Transfection efficiency was estimated by GFP expression. I(HCN2) was measured with patch clamp, and cells were administered into the left ventricular anterior wall of adult dogs in complete heart block and with backup electronic pacemakers. Studies encompassed 6 weeks. I(HCN2) for all cells was 32.1+/-1.3 pA/pF (mean+/-SE) at -150 mV. Pacemaker function in intact dogs required 10 to 12 days to fully stabilize and persisted consistently through day 42 in dogs receiving > or =700,000 hMSCs (approximately 40% of which carried current). Rhythms were catecholamine responsive. Tissues from animals killed at 42 days manifested neither apoptosis nor humoral or cellular rejection. CONCLUSIONS: hMSCs provide a means for administering catecholamine-responsive biological pacemakers that function stably for 6 weeks and manifest no cellular or humoral rejection at that time. Cell doses >700,000 are sufficient for pacemaking when administered to left ventricular myocardium.

Effects of inhibition of poly(adenosine diphosphate-ribose) synthase on acute cardiac allograft rejection.

BACKGROUND: Nitric oxide synthase (NOS)-2 is expressed during acute cardiac allograft rejection in association with death of heart muscle cells. The nuclear enzyme poly(adenosine diphosphate [ADP]-ribose) synthase (PARS) is activated by agonists such as NO and peroxynitrite, which cause single-strand DNA breaks; PARS, in turn can promote both necrosis and apoptosis. To investigate the hypothesis that NO produced by NOS-2 in cardiomyocytes activates PARS and contributes to heart muscle cell death by apoptosis, experiments were performed using a heterotopic rat abdominal heart transplant model and cytokine-stimulated heart muscle cells in tissue culture. METHODS: Cardiac allografts were treated after transplantation with either the PARS inhibitor 5-aminoisoquinolinone at 3 mg/kg subcutaneously daily or with vehicle. Isolated purified adult rat cardiomyocytes incubated with cytokines to induce NOS-2 were treated in vitro with another PARS inhibitor, 3-aminobenzamide (3AB). RESULTS: PARS inhibition increased cardiac-allograft survival from 6 +/- 2 to 10 +/- 3 days (n=6, n=6, P<0.05). The inflammatory infiltrate, NOS-2-positive macrophages, myocyte apoptosis, and myocyte content of nitrotyrosine and poly(ADP-ribose) were significantly decreased in PARS inhibited allografts at day 5 posttransplantation. Similarly, apoptosis and PARS activity were diminished in cytokine-stimulated adult rat cardiomyocytes when either 3AB or L-NMMA were applied. CONCLUSIONS: The data indicate that PARS activation occurs during acute cardiac-allograft rejection and contributes significantly to the inflammatory response and to the death of cardiac muscle cells by apoptosis. They suggest that PARS inhibition combined with immunosuppression might enhance salvage of heart-muscle cells during acute cardiac-allograft rejection.

Metabolic and functional protection by selective inhibition of nitric oxide synthase 2 during ischemia-reperfusion in isolated perfused hearts.

BACKGROUND: Drugs that selectively block nitric oxide synthase (NOS) 2 enzyme activity by inhibiting dimerization of NOS2 monomers have recently been developed. METHODS AND RESULTS: To investigate whether selective inhibition of NOS2 is cardioprotective, rats were pretreated for 2 days with BBS2, an inhibitor of NOS2 dimerization, at 15 mg/kg SC. Isolated buffer-perfused hearts from treated (n=9) and control (n=7) hearts were subjected to 20 minutes of ischemia followed by 60 minutes of reperfusion. NOS2 protein was upregulated in all hearts at the end of ischemia and of reperfusion; NOS2 enzyme activity was 60% lower in hearts from the treated animals. In the treated hearts, the increase in end-diastolic pressure was significantly attenuated at the end of ischemia, and the return of developed pressure at reperfusion was greater (P<0.05). Creatine kinase release at reperfusion was lower in treated hearts than in controls (P=0.02). At the end of ischemia and of reperfusion, myocardial ATP levels were significantly higher in the treated hearts than in controls (P<0.05). In the treated hearts under ischemic conditions, lactate content was higher and the lactate/pyruvate ratio was lower than in controls (P<0.05); GAPDH activity was higher; and G-3-P and aldose reductase activity were lower. At reperfusion, in the treated hearts, there was less histological damage and less apoptosis of cardiac muscle cells. CONCLUSIONS: Pretreatment with BBS2, a selective inhibitor of NOS2, improves contractile performance, preserves myocardial ATP, and reduces damage and death of cardiac myocytes during ischemia and reperfusion of isolated buffer-perfused rat hearts.

Effects of selective inhibitors of nitric oxide synthase-2 dimerization on acute cardiac allograft rejection.

BACKGROUND: Nitric oxide synthase-2 (NOS2) is expressed during acute cardiac allograft rejection in association with myocardial inflammation, contractile dysfunction, and death of cardiomyocytes by necrosis and apoptosis. Recently, allosteric inhibitors of NOS2 monomer dimerization that block NOS2 activity have been developed. METHODS AND RESULTS: To investigate effects of selective NOS2 blockade, 15 mg/kg of BBS-1 or BBS-2 was administered twice daily subcutaneously to rats starting the day of heterotopic heart transplantation. Cardiac allograft survival was increased significantly, from 6.8 days in controls to 13.3 and to 14.2 days in NOS2-inhibited allografts. At day 5 after heart transplantation, synthesis of NOx was reduced by 53%. There were significantly fewer T lymphocytes and macrophages in the inflammatory infiltrate, as well as less edema and cardiomyocyte damage, and the International Society of Heart and Lung Transplantation score fell from 5 to 4 and 3.5. NOS2 and nitrotyrosine immunostaining and the mean numbers of apoptotic cells and of apoptotic cardiomyocytes were significantly diminished in the treated allografts. CONCLUSIONS: The data indicate that selective inhibition of NOS2 dimerization prolongs survival and reduces myocardial inflammation and cardiomyocyte damage in acute cardiac allograft rejection.