Scaling-up of a HepaRG progenitor cell based bioartificial liver: optimization for clinical application and transport.

A new generation of bioartificial livers, based on differentiated proliferative hepatocyte sources, has been developed. Several practicable and regulatory demands have to be addressed before these can be clinically evaluated. We identified three main hurdles: (1) expansion and preservation of the biocomponent, (2) development of scaled-up culture conditions and (3) transport of the device to the bedside. In this study we address these three issues for the HepaRG-progenitor cell line-loaded AMC-Bioartificial Liver. (1) HepaRG cells were expanded in large quantities and then cryopreserved or loaded directly into bioreactors. After 3 weeks of culture, key hepatic functions (ammonia/lactate elimination, apolipoprotein A1 synthesis and cytochrome P450 3A4 activity) did not differ significantly between the two groups. (2) Bioartificial livers were scaled up from 9 ml to 540 ml priming volume, with preservation of normalized hepatic functionality. Quantification of amino acid consumption revealed rapid depletion of several amino acids. (3) Whole-device cryopreservation and cooled preservation induced significant loss of hepatic functionality, whereas simulated transport from culture-facility to the bedside in a clinical-grade transport unit with controlled temperature maintenance, medium perfusion and gas supply did not affect functionality. In addition, we assessed tumorigenicity of HepaRG cells in immune-incompetent mice and found no tumor formation of HepaRG cells (n = 12), while HeLa cells induced formation of carcinomas in eight out of 12 mice in 140 days.

Cell intrinsic modulation of Wnt signaling controls neuroblast migration in C. elegans.

Members of the Wnt family of secreted signaling proteins are key regulators of cell migration and axon guidance. In the nematode C. elegans, the migration of the QR neuroblast descendants requires multiple Wnt ligands and receptors. We found that the migration of the QR descendants is divided into three sequential phases that are each mediated by a distinct Wnt signaling mechanism. Importantly, the transition from the first to the second phase, which is the main determinant of the final position of the QR descendants along the anteroposterior body axis, is mediated through a cell-autonomous process in which the time-dependent expression of a Wnt receptor turns on the canonical Wnt/ß-catenin signaling response that is required to terminate long-range anterior migration. Our results show that, in addition to direct guidance of cell migration by Wnt morphogenic gradients, cell migration can also be controlled indirectly through cell-intrinsic modulation of Wnt signaling responses.