Hep-Art, artificial liver development

Product

Technology

The AMC-BAL is currently based on primary (porcine) hepatocytes, immobilized on a non-woven tissue spirally wound in a cartridge and an integral oxygenator. Primary hepatocytes are attached as small aggregates to the matrix and function in vitro for at least two weeks.

The AMC-BAL has several important advantages in comparison to the bioartificial liver types based on hollow fibres: for an extensive description, see Flendrig et al 1997c. A short summary of the advantages are:

Liver cells are attached and function in the AMC-BAL as small aggregates, rather than as single cells.

Oxygenation of the liver cells is optimal because it occurs on the spot by hollow fibres inside the bioreactor.

In the AMC-BAL there is no semi-permeable barrier between the plasma of the patient and the liver cell aggregates, simulating liver cell perfusion conditions like in vivo.

The AMC-BAL can easily contain the equivalent of 200 grams (20 billion of liver cells) or more of liver tissue.

The AMC-BAL has a simple construction, is cheap, is based on FDA approved materials, and can be steam sterilized.

Schematic drawings of a transverse and longitudinal cross-section of the bioreactor (right), a scanning electron micrograph of a small section of the cell culture compartment (upper left), and a scanning electron micrograph of hepatocyte aggregates attached to a scaffold (lower left) are shown above. The system is composed of a dialysis housing (A) comprising a three-dimensional nonwoven fabric (B) for high density hepatocyte culture as small aggregates and hollow-fiber membranes (C) for oxygen supply and CO2 removal. The combination of the matrix and the oxygenation tubing creates a third compartment (D). These channels are used to perfuse the plasma of the recipient through the bioreactor which can get in direct contact with the hepatocytes in the fabric. Plasma is perfused through the bioreactor via the side ports (F). The integrated oxygenator of the bioreactor is connected to the gas supply via the endcaps (E). The homogenous distribution of the oxygenation fibers throughout the bioreactor compartment ensures that every hepatocyte has an oxygenation source within its direct surroundings.

Pre-clinical Science

The AMC-BAL has been tested extensively in vitro (Flendrig 1997a, 1998a) and in vivo both in small animals (Flendrig 1997b, 1998b, 1999) and in larger animals (Flendrig 1997c). Animals with acute liver failure due to surgically induced complete liver ischemia (LIS), are connected during 24 hours to the BAL charged with freshly isolated porcine hepatocytes (CELL-BAL): 0.44 billion cells in LIS-rats and 10-14 billion cells in LIS-pigs. A schematic drawing of the extracorporeal circuit based on plasmapheresis is shown in Figure 1.

The survival time in this model of irreversible acute liver failure was significantly prolonged in animals treated with the CELL-BAL in comparison to control animals only treated by intensive care or an EMPTY-BAL (see Figure 2). In addition, improvement of several biochemical parameters (for instance plasma ammonia and bilirubin) was observed (not shown).

Figure 1: Schematic representation of the bioartificial liver support system. Plasma was obtained from the recipient by a centrifugal plasma-separator. To prevent cellular immunological problems, two plasma filters were included. When blocked, these filters can easily be replaced during the extra-corporal artificial liver procedure. Different filter types (various material properties and cut-off) can be applied without changing the bioreactor design.

Figure 2: The survival times of pigs after inducing liver ischemia (at t=0 h). Life was significantly prolonged in the LIS CELL-BAL group compared to the three control groups (p<0.027). The black bar represents the period in which groups B, C and D were connected to the plasma-separator. C= controls, only intensive care EB= EMPTY BAL PP= plasmapheresis CELL-BAL= BAL charged with 10-14 billion primary porcine hepatocytes.