Patient-specific induced pluripotent stem-cell models for long-QT syndrome

BACKGROUND

Long-QT syndromes are heritable diseases associated with prolongation of the QT interval on an electrocardiogram and a high risk of sudden cardiac death due to ventricular tachyarrhythmia. In long-QT syndrome type 1, mutations occur in the KCNQ1 gene, which encodes the repolarizing potassium channel mediating the delayed rectifier I(Ks) current.

METHODS

We screened a family affected by long-QT syndrome type 1 and identified an autosomal dominant missense mutation (R190Q) in the KCNQ1 gene. We obtained dermal fibroblasts from two family members and two healthy controls and infected them with retroviral vectors encoding the human transcription factors OCT3/4, SOX2, KLF4, and c-MYC to generate pluripotent stem cells. With the use of a specific protocol, these cells were then directed to differentiate into cardiac myocytes.

RESULTS

Induced pluripotent stem cells maintained the disease genotype of long-QT syndrome type 1 and generated functional myocytes. Individual cells showed a “ventricular,” “atrial,” or “nodal” phenotype, as evidenced by the expression of cell-type–specific markers and as seen in recordings of the action potentials in single cells. The duration of the action potential was markedly prolonged in “ventricular” and “atrial” cells derived from patients with long-QT syndrome type 1, as compared with cells from control subjects. Further characterization of the role of the R190Q–KCNQ1 mutation in the pathogenesis of long-QT syndrome type 1 revealed a dominant negative trafficking defect associated with a 70 to 80% reduction in I(Ks) current and altered channel activation and deactivation properties. Moreover, we showed that myocytes derived from patients with long-QT syndrome type 1 had an increased susceptibility to catecholamine-induced tachyarrhythmia and that beta-blockade attenuated this phenotype.

CONCLUSIONS

We generated patient-specific pluripotent stem cells from members of a family affected by long-QT syndrome type 1 and induced them to differentiate into functional cardiac myocytes. The patient-derived cells recapitulated the electrophysiological features of the disorder. (Funded by the European Research Council and others.)

Comparison of experimental microvascular end-to-end anastomosis via VCS-Clips versus conventional suture technique in an animal model

In this experimental study on 96 CD rats, microvascular end-to-end anastomoses created via suture or alternatively by means of a VCS-Clip-Application-System, were compared. The aorta abdominalis of the animals, with a diameter of 1.5 +/- 0.2 mm, was experimentally dissected, and the free ends of the vessel then anastomosed. The results were evaluated using sonography, microangiography, histologic examination, and vascular imprints. Postoperative examination was carried out after 1, 3, 7, 14, or 30 days. Major advantages of the VCS-Clip technique over suturing were that it was easy to learn, significantly faster to perform (execution of anastomosis 10.9 +/- 2.6 min versus 19.4 +/- 5.0 min), and produced significantly more favorable histologic results in terms of less inflammatory response, foreign body reaction, necrosis of the tunica media, hyperplasia of the intima, and thrombosis of the vessel lumen. The main disadvantage of the clip technique was a significantly higher rate of stenoses (15.8 +/- 6.0 versus 4.1 +/- 6.6 percent).

[Two surgical case reports showing atypical heparin-induced thrombocytopenia]

Heparin-induced thrombocytopenia (HIT) represents a serious side effect caused by an atypical immune response to platelet factor 4 leading to platelet activation and thrombin formation. These patients are at high risk of thromboembolism, with a rapid drop in platelet count between days 5 and 14 after the initiation of heparin treatment. In single cases, especially after major surgery, platelet count reduction might be absent or hidden by preceding thrombocytosis. Different clinical manifestations of HIT include unspecific skin reactions with potential necrosis at the site of heparin injection, mostly after the application of unfractionated heparin but also with low molecular weight heparin. In heparin-induced skin necrosis, administration of unfractionated or low molecular weight heparin is contraindicated and heparin therapy should be stopped immediately. Instead, an alternative anticoagulant in the form of a direct thrombin inhibitor such as argatroban, and respectively lepirudin, or danaparoid sodium must be administered. Due to frequent misinterpretations of heparin-induced unspecific skin reactions, especially in the absence of thrombocytopenia, we present two case reports which should increase the awareness of HIT's various clinical pictures.

[Neovascularization of pre-formed tissue flaps in relation to arteriovenous blood flow of the implanted vascular pedicle. Experimental study in the rabbit]

In 45 Chinchilla-Bastard rabbits, a skeletonised arterio-venous pedicle was implanted on the subsurface of a 15 x 8 cm abdominal skinflap to create a neovascularised axial prefabricated flap. In order to evaluate the potency of neovascularisation in relation to the blood flow of the pedicle, we compared minimal blood flow by distal ligation (model 1) with maximal blood flow by distal microvascular arteriovenous shunt anastomoses (model 2) of the implanted vascular pedicle. The results show that 8 and 12 days after pedicle implantation, tissue flap perfusion in model 2 is significantly earlier and better in comparison to model 1.

[Problems in the reconstruction of bile flow in orthotopic liver transplantation]

In hepatic transplantation complications of the biliary drainage were frequently observed. Ischemia of the extrahepatic bile duct which occurs for anatomical reasons can cause necrosis of the bile duct. The reconstruction of biliary drainage by biliodigestive anastomosis results in ascending infections of the graft. Biliary sludge could obstruct the intra- or extrahepatic bile duct. Recently, operation methods are mainly applied in which the function of Oddi's sphincter is preserved, i.e. choledocho-choledochostomy or gallbladder conduit method. If it is not possible to perform these methods the Roux-y-jejunum loop is used. Finally, an immediate operative revision of the biliary drainage is indicated if its complication is diagnosed.

[Aspergillosis following liver transplantation as a hospital infection]

In the first four weeks after a liver transplantation, there was an invasive aspergillosis with a lethal course in three out of five patients who were treated postoperatively in the same room. The clinical symptoms were very different. One patient was asymptomatic, and the diagnosis could only be made by autopsy. In another patient, pulmonary symptoms, and in the third patient, cerebral symptoms were the most prominent. In the two latter patients, the infection was demonstrated in the sputum and by bronchoalveolar lavage. The disease course was fulminant in all patients, and therapy was without success. Owing to this high incidence, mycological investigations were carried out on the ward. A flower bench in the hall beside the ward was probably the main focus of distribution. To avoid such nosocomial infections, foci of aspergillus distribution should if possible be removed from the surroundings of patients with weakened immune resistance.

Successful treatment of hepatic coma by a new artificial liver device in the pig

In this study, we tested a new artificial liver device using liver pieces in 8-h hemoperfusion of comatous porcine blood and compared two alternative tissue preparations. Acute hepatic coma in the pigs was induced by complete devascularization of the liver. The animals were killed in stage IV coma (15-25 h after the operation), and 1 l blood was perfused over 200 g fresh or DMSO-preserved liver cubes. After the devascularization GOT, GPT, GLDH, AP, LDH, SDH, bilirubin, free fatty acid, and bile acid levels in serum increased progressively. Ammonia concentrations underwent a rapid increase in the first 9 h of coma development from 126.0 +/- 9.9 to 321.9 +/- 62.2 mumol/l. Most of the amino acids in serum were elevated and molar ratio of BCAA/AAA declined from 3.87 +/- 0.79 to 0.92 +/- 0.24. In the course of hemoperfusion ammonia was removed from the perfusate to 71% of the initial values using fresh and to 39% using preserved tissue. Correspondingly, there was an increase in urea concentrations. Amino acid metabolism was ameliorated during the perfusion; Fischer's quotient increased from 0.91 +/- 0.15 to 1.38 +/- 0.14 (fresh liver) and from 0.89 +/- 0.14 to 2.11 +/- 0.44 (preserved liver); neuroexcitatory amino acids Asp and Glu were markedly elevated. Energy charge of the liver cells increased and reached levels exceeding 0.5 in both experimental groups, a balanced energy metabolism was maintained and suggests active metabolization by the liver pieces. In comparison with fresh tissue, preserved liver cubes proved effective. We consider our artificial liver device capable of temporary hepatic support in acute necrosis of the liver and suppose that its efficiency can be potentiated by combining this system with other procedures.

Immune regulatory effect of hepatic factor associated with thymus alteration

This study was carried out to clarify the mechanism of the immune regulatory effect of factors which were liberated from the ischemic damaged liver. By occlusion of the hepatic vessels (hepatic artery and portal vein) for 40 min daily during 5 days to induce the ischemic damage of the liver, reduced thymus weight (50 +/- 5 mg; control, 274 +/- 23 mg) and cell count (0.7 +/- 0.3 X 10(7); control, 3.5 +/- 0.3 X 10(8] and complete differentiation of thymocytes were observed, i.e., helper cells reacting to monoclonal antibody W3/25 were 34 +/- 8% and suppressor/cytotoxic cells to OX-8, 49 +/- 5% (in control W3/25:89 +/- 1%, OX-8:89 +/- 1%). These quantitative and qualitative changes of thymocytes were correspondent to those of animals treated with 40 mg CsA/kg per day for 5 days; however, medication with 10 mg prednisolone/day 5 times could not induce any alteration of thymocyte subpopulation (W3/25:89 +/- 1%, OX-8:87 +/- 1%) although the weight and cell count decreased to 92 +/- 8 mg and 4.1 +/- 0.6 X 10(7), respectively. Furthermore, 5 days after liver allotransplantation (BDE to LEW), the weight and cell count of the thymus were extremely reduced (58 +/- 6 mg, 2.7 +/- 0.2 X 10(7], and thymocyte differentiation was observed (W3/25:56.6%, OX-8:61 +/- 11%). On the other hand, in heart transplantation the atrophy of the thymus was not so strong (105 +/- 28 mg, 1.3 +/- 0.6 X 10(8], and there was no change in the subpopulation (W3/25:89 +/- 2%, OX-8:88 +/- 1%).(ABSTRACT TRUNCATED AT 250 WORDS)