Ex vivo preparation of porcine hepatocytes for use in bioartificial hepatic support systems

Mass Preparation of Primary Porcine Hepatocytes and the Design of a Hybrid Artificial Liver Module using Spheroid Culture for a Clinical Trial

To isolate a large number of porcine hepatocytes, we originally developed a mass preparation method that combined the usual collagenase perfusion method of a whole liver with a collagenase redigestion method of tissue fragments after liver perfusion. Using a pig of 10kg, collagenase perfusion only resulted in a yield of 63 ± 78 x 108 total cells with a viability of 69.2 ± 25.3 %, but our combined method had a yield of 167 ± 31 x 108 total cells with a viability of 87.9 ± 4.4 % (mean ± SD). Also, the combined method was applied to two pigs of 10kg body weight at the same time, and isolated 387 ± 89 x 108 hepatocytes with a viability of 87.1 ± 6.9 % and a purity of 93.6 ± 2.8 % in 11 experiments.

We designed a large multi-capillary polyurethane foam (MC-PUF) packed-bed module containing 1 x 1010 porcine hepatocytes on a clinical trial scale. The porcine hepatocytes in the module formed spherical multicellular aggregates (spheroids) of 200 – 500 μm diameter. Most hepatocytes forming spheroids were viable judged by fluorescein diacetate and ethidium bromide staining. The activities of ammonia removal, albumin secretion and oxygen consumption of the large MC-PUF module were the same as for a small MC-PUF module containing 2 x 108 porcine hepatocytes, and were maintained for at least 9 days of culture. These results show that a large MC-PUF module is successfully scaled up 50 times.

In conclusion, we succeeded in developing a mass preparation method of porcine hepatocytes and a large hybrid artificial liver module on a clinical trial scale.

Efficiency of doxorubicin handling by isolated hepatocytes is a valuable indicator for restored cell function

Pig liver is a possible source of hepatocytes for extracorporeal bio-artificial liver devices. In order to evaluate recovered hepatocyte function following enzymatic isolation, we developed a cytochemical method that is based on the capacity of hepatocytes to sequester the anthracycline antitumour drug doxorubicin within intracellular acidic compartments. Doxorubicin is a naturally fluorescent molecule. Thus, the process of drug concentration within hepatocytes can be visualized in living conditions by fluorescence microscopy. Porcine hepatocytes harvested from heart-beating donors were grown either as isolated cell suspensions or as tissue monolayers. Immediately after isolation and at fixed culture times, cells were incubated with 0.1 mM doxorubicin in Hanks' balanced salt solution for 10 min at 37 degrees C in 5% CO2-humidified atmosphere and observed by fluorescence microscopy. Parallel electron microscopy was performed to compare fluorescence data with general cell morphology. To monitor lysosomal acidification capacity, the fluorescent pH-sensitive vital dye LysoSensor-Blue was used. Doxorubicin fluorescence showed different patterns of nuclear and cytoplasmic staining, according to the time allowed for cell recovery and the culture method. In particular, cytoplasmic fluorescence changed from a diffuse staining, that could be observed after cell isolation and in hepatocyte suspensions, to a punctate perinuclear and pericanalicular fluorescence detectable in fully recovered hepatocyte monolayers. This study indicates that the 'doxorubicin-fluorescence test' may be considered a simple and rapid procedure for assessing hepatocyte functional condition. It may provide valuable and 'real time' guidelines for judging the correct way these cells are to be collected, preserved and utilized for clinical purposes.