Extracorporeal Mass Exchange Technology Platform for Temporary Liver Support: A Clinical Feasibility Study on a Device and the Cell Source Primary Human Liver Cells

Clinical feasibility phase-I study data are discussed on the use and the safety of a modular mass exchanger for temporary extracorporeal treatment of liver failure; and the use of the cell source primary human liver cells isolated from discarded transplant organs as a metabolic module in this mass exchanger. This technology platform can be compared with the mass exchange functions of a human placenta before giving birth. The "maternal blood side" can be used with various sources/modules of metabolic support including artificial (e.g. absorber) or biological elements (e.g. cells), separated by membrane compartments. These keep the source of metabolic support from contact with the patient, including the immune cells, while allowing exchange of soluble or protein-bound plasma components for therapy. Each of the multiple independent membrane compartments are bundled towards the in/outlets but interwoven to form a decentralized multi-compartment mass exchanger within an effector module compartment. The use of liver cells as a metabolic module in this compartment results in its function as a bioreactor. A combination with further modules outside of the mass exchanger was demonstrated through a continuous SPAD for detoxification. Nine patients (5 m, 4 f) with a median age of 43 years (range 11-55 years) were treated with a total of 11 metabolic modules in 12 sessions, with overall treatment times ranging from 11 to 216 hours. Patients suffered from acute-on-chronic liver failure (AoCLF, n=3), acute liver failure (ALF, n=3) and primary non-function graft after liver transplantation (PNF, n=3). Treatment resulted in a one-year survival of 78%. The results showed a significant decrease in thrombocytes and fibrinogen. No severe adverse effects were found. One patient (AoCLF) recovered without transplantation and remained alive for the one-year follow-up. Six patients (3 ALF, 2 PNF, and 1 AoCLF) were successfully bridged to transplantation, and two (1 AoCLF, 1 PNF) died within ten days after termination of therapy. Total and conjugated bilirubin, ammonia, urea and creatinine were significantly reduced by the end of therapy, compared to baseline. The MELD score decreased significantly, whereas no significant improvements were observed in APACHE-II, APACHE-III, SOFA and Child-Pugh scores. Conclusion: The mass exchanger technology platform, the Core Module used with primary human liver cells as Metabolic Module, proved to be clinically feasible and safe. Further clinical studies are required to prove the efficacy of such therapies. However, the clinical impact of using human liver cells as a Metabolic Module is limited and a reliable, biocompatible and effective metabolic source is in need.

Abstract 17015: PGC-1alpha/Arhgap6 Axis Mediates Diabetic Vascular Dysfunction Through Diminution of Endothelial Glycolytic Flux

Introduction: Aberrant angiogenesis in diabetes (DM) is caused by failure of local endothelial cells (ECs) to properly undergo VEGF-driven migration, and leads to a high propensity to develop critical limb ischemia. We recently showed that type 1 and 2 DM induce PGC-1α in ECs, which in turn strongly blocks EC migration and angiogenesis. Despite this therapeutic potential, PGC-1α may not be “druggable” due to the diverse distribution and functions in non-vascular tissues. Thus, understanding EC PGC-1α effectors is critical, which may involve bioenergetics since PGC-1α broadly induces mitochondrial OxPhos. Although ECs show high rate of glycolytic flux and synthesis of lactate, a burgeoning angiogenic mediator, this is blunted in DM via mechanisms still ill-defined. We hypothesized that a novel PGC-1α target in DM mediates blunted EC glycolysis and migration. Methods and Results: By leveraging NRF1/2-binding defective PGC-1α, we show that PGC-1α blocks glycolysis, through PPARgamma-driven Notch induction independent of mitochondrial activation, which fully accounts for PGC-1α inhibition of EC migration in DM. mRNA microarray identified ARHGAP6, a Rho-GAP and actin cytoskeletal modulator, as a DM-inducible main effector of PGC-1α axis to inhibit EC lactate synthesis and migration. Data suggest the causal role for ARHGAP6 in the reduced migration and glycolysis (Seahorse XF analyzer) of STZ-induced DM mouse ECs. Impaired migration of DM ECs and ECs overexpressing PPARgamma or ARHGAP6 was associated with decreased activity of Rac1 and rescued by addition of lactate. Reduced GTP-Rac1 in ECs overexpressing PGC-1α was restored by knockdown of ARHGAP6. Positive feedback loop between Rac1 and LDHA was demonstrated, suggesting a cytoskeletal-metabolic module to mediate EC migration and dysfunction. Conclusions: PGC-1α/ ARHGAP6 inhibition of EC glycolysis and lactate synthesis is a key mechanism of impaired EC migration in DM angiopathy. Our data provide important insights into the mechanistic link between EC actin cytoskeleton and bioenergetics mediated by ARHGAP6, and opportunities to restore diminished glycolysis in DM ECs by targeting PGC-1α axis component ARHGAP6 to develop safe and efficacious therapeutic since it is dispensable for health.

Increase of Oxygen Consumption during a Progressive Decrease of Ventilatory Support Is Lower in Patients Failing the Trial in Comparison with Those Who Succeed

Background The aim of this study was to test the hypothesis that, during weaning from mechanical ventilation, when the pressure support level is reduced, oxygen consumption increases more in patients unable to sustain the decrease in ventilatory assistance (weaning failure). Methods Patients judged eligible for weaning were enrolled. Starting from 20 cm H2O, pressure support was decreased in 4-cm H2O steps, lasting 10 min each, until 0 cm H2O; this level was kept for 1 h. The average oxygen consumption from the last 3 min of each step, along with other ventilatory variables, was measured by indirect calorimetry (M-CAiOVX "metabolic module," Engstrom Carestation; GE Healthcare, Madison, WI) and recorded. Patients were defined as belonging to the failure group if, at any moment, they developed signs of respiratory distress according to standard criteria, or to the success group otherwise. Results Twenty-eight patients were studied. In most patients, the minimum oxygen consumption was not recorded at the highest pressure support applied. Sixteen patients were able to complete the weaning trial successfully, whereas 12 failed it; the success group had a minimum oxygen consumption lower than failure group (mean +/- SD: 174 +/- 44 vs. 215 +/- 53 ml/min, P < 0.05). Moreover, although respiratory drive (assessed by P0.1) increased more in the failure group, this group had a lower increase in oxygen consumption, contradicting our hypothesis. Conclusions Patients failing a decremental pressure support trial, in comparison with those who succeed, had an higher baseline oxygen consumption and were not able to increase their oxygen consumption in response to an increased demand.

Laboratory Validation of the M-COVX Metabolic Module in Measurement of Oxygen Uptake

A practical method of breath-by-breath monitoring of metabolic gas exchange has previously been developed by GE Healthcare and can now be easily incorporated into existing anaesthetic and critical care monitoring (M-COVX). Previous research using this device has shown good accuracy and precision between the M-COVX measurements and a traditional measurement of gas uptake at the mouth and also against the reverse Fick method during cardiac surgery and critical care, but its accuracy in the paediatric situation and across a range of ventilatory settings awaits validation. We tested the M-COVX metabolic monitor in the laboratory comparing its measurement to a traditional Haldane transformation across a wide range of oxygen consumption values, from 50 ml/minute to just under 300 ml/minute, typical of those expected in anaesthetised adults and children. The M-COVX device showed acceptable accuracy with an overall mean bias of −3.3% (range −15.1 to +4.2%, P=0.21). Excellent linearity was found, by y=0.96x + 0.5 ml/minute, r=0.99. The device showed acceptable robustness to ventilatory changes examined, including changes in respiratory rate, I:E ratio, FiO2, up to 75% and simulated spontaneous breathing. However, any induced leak from around the simulated endotracheal tube caused a significant error in paediatric scenarios.