ACEMg-mediated hearing preservation in cochlear implant patients receiving different electrode lengths (PROHEARING): study protocol for a randomized controlled trial.

BACKGROUND: The indications for a cochlear implant (CI) have been extended to include patients with some residual hearing. Shorter and thinner atraumatic electrodes have been designed to preserve the residual hearing in the implanted ear. However, the insertion of the electrode array into the cochlea, with potential mechanical trauma and the presence of this foreign body inside the cochlea, may lead to free radical formation and reduced blood perfusion of the cochlea which can result in the loss of residual hearing. METHODS/DESIGN: In this single-center, randomized, placebo-controlled, double-blind phase II clinical trial the effect of free radical scavengers and a vasodilator on the residual hearing of 140 CI patients will be evaluated. The formulation is composed of ß-carotene (vitamin A), ascorbic acid (vitamin C), dl-α-tocopherol acetate (vitamin E) and the vasodilator magnesium (Mg), or ACEMg. Medication is administered twice daily per os for approximately 3 months. The primary measure is based upon the reduction in postoperative low-frequency air-conducted pure-tone thresholds compared to preoperative thresholds in ACEMg-treated patients compared to those of a placebo group. Additionally, the effect of different electrode lengths (20, 24 and 28 mm) is analyzed. Study visits are scheduled 2 days before surgery, at first fitting, which is the adjustment and start of stimulation via CI 4 weeks after surgery and 3, 6, 9 and 12 months after first fitting. The primary endpoint is the air-conduction hearing loss at 500 Hz 3 months after first fitting. Additionally, speech recognition tests, hearing aid benefit in the implanted ear and electrophysiological measurements of implant function are assessed. Since this is a blinded clinical trial and recruitment is still ongoing, data continue to accrue and we cannot yet analyze the outcome of the ACEMg treatment. DISCUSSION: There is an unfulfilled need for new strategies to preserve acoustic hearing in CI patients. This study will provide first-in-man data on ACEMg-mediated protection of residual hearing in CI patients. Performing all surgeries and patient follow-up at one study site improves consistency in diagnosis and therapy and less variability in surgery, audiological test techniques and fitting. This approach will allow investigation of the influence of ACEMg on residual hearing in CI patients. TRIAL REGISTRATION: The German Bundesinstitut für Arzneimittel und Medizinprodukte (BfArM) application number 4039192, was registered on 6 December 2013 with protocol amendment version 3.0 from 19 August 2014. EudraCT number: 2012-005002-22 .

Prevention of hyperacute xenograft rejection through direct thrombin inhibition with hirudin.

BACKGROUND: Hyperacute xenograft rejection (HXR) is characterized by complement activation and intravascular thrombosis. The pathogenesis of HXR is attributed to antibodies binding to α-Gal-epitopes on the endothelial cells (EC) of the xenograft, activating complement and thrombin-mediated coagulation mechanisms. Our aim was to evaluate the influence of thrombin inhibition upon HXR and tissue integrity in an ex-vivo working heart model. MATERIAL/METHODS: Eighteen isolated porcine hearts were perfused with human whole blood in a working heart model. The blood was treated with heparin (n=9) in group G-I and with heparin and additionally recombinant hirudin (0.012 mg/ml bolus, afterwards 4.5 µg/ml/h continuously) in group G-II (n=9). The experiments were terminated at end of cardiac output. Histological analysis was performed after the experiments. RESULTS: Working heart time of G-II was significantly longer (712.0±37.8 vs. 125.0±31.4 min, p<0.01). Heart weight increase in G-II was lower (0.05±0.01 vs. 0.30±0.06%/min, p<0.01). Stroke work index and specific coronary flow improved significantly in G-II after 120 minutes. Histological analysis revealed increased tissue damage and thrombosis phenomena in G-I. Moreover, immunohistochemistry showed increased C3 and C5b-C9 upon EC of G-I. CONCLUSIONS: Direct thrombin inhibition with Hirudin could be a successful strategy in primate xenotransplantation experiments to prevent tissue damage thus improving the graft survival.

Influence of hypothermia and cardioplegic solutions on expression of alpha-Gal epitope on porcine aortic endothelial cells.

OBJECTIVES: The Galalpha1-3Galbeta1-4GlcNAc-R is the major antigen on pig tissue bound by human xenoreactive natural antibodies in xenotransplant. We have investigated in vitro the influence of hypothermic storage with cardioplegic solutions on expression of Galalpha1-3Galbeta1-4GlcNAc-Rs and hyperacute xenograft rejection. MATERIALS AND METHODS: To analyze effects of hypothermia on the Galalpha1-3Galbeta1-4GlcNAc-Rs, cultured porcine aortic endothelial cells were exposed to a temperature of 4 degrees C for 1 hour, 4 hours, and 6 hours. Cell cultures of the control groups were incubated at the same time at 38 degrees C. To investigate the influence of cardioplegic solutions on the Galalpha1- 3Galbeta1-4GlcNAc-Rs, porcine aortic endothelial cells were exposed to 4 degrees C for 4 hours in the presence of University of Wisconsin solution or histidinetryptophan- ketoglutarate solution. Cells of the control groups were cooled at 4 degrees C for 4 hours without cardioplegic solution. After treatment, porcine aortic endothelial cells were submitted to fluorescence-activated cell sorter. RESULTS: Hypothermia of 4 degrees C showed no significant effect on the quantity of Galalpha1-3Galbeta1-4GlcNAc-Rs. However, the treatment of porcine aortic endothelial cells with University of Wisconsin solution resulted in a highly significant reduction of Galalpha1-3Galbeta1- 4GlcNAc-Rs by 50% (P = .006). Treatment of porcine aortic endothelial cells with histidine-tryptophanketoglutarate solution decreased Alpha-Gal quantity significantly by 32% (P = .011). CONCLUSIONS: Our data offer new perspectives in the prevention of hyperacute, humoral xenograft rejection by reducing the Galalpha1-3Galbeta1-4GlcNAc-Rs after exposure to different cardioplegic solutions.