Flat membrane bioreactor for the replacement of liver functions

The effectiveness of a novel cartridge-based bioreactor design in supporting liver cells

There are a number of applications--ranging from temporary strategies for organ failure to pharmaceutical testing--that rely on effective bioreactor designs. The significance of these devices is that they provide an environment for maintaining cells in a way that allows them to perform key cellular and tissue functions. In the current study, a novel cartridge-based bioreactor was developed and evaluated. Its unique features include its capacity for cell support and the adaptable design of its cellular space. Specifically, it is able to accommodate functional and reasonably sized tissue (>2.0 x 10(8) cells), and can be easily modified to support a range of anchorage-dependent cells. To evaluate its efficacy, it was applied to liver support in the current study. This involved evaluating the performance of rat primary hepatocytes within the unique cartridges in culture--sans bioreactor--and after being loaded within the novel bioreactor. Compared to collagen sandwich culture functional controls, hepatocytes within the unique cartridge design demonstrated significantly higher albumin production and urea secretion rates when cultured under dynamic flow conditions--reaching peak values of 170 +/- 22 microg/10(6) cells/day and 195 +/- 18 microg/10(6) cells/day, respectively. The bioreactor's effectiveness in supporting live and functioning primary hepatocytes is also presented. Cell viability at the end of 15 days of culture in the new bioreactor was 84 +/- 18%, suggesting that the new design is effective in maintaining primary hepatocytes for at least 2 weeks in culture. Liver-specific functions of urea secretion, albumin synthesis, and cytochrome P450 activity were also assessed. The results indicate that hepatocytes are able to achieve good functional performance when cultured within the novel bioreactor. This is especially true in the case of cytochrome P450 activity, where by day 15 of culture, hepatocytes within the bioreactor reached values that were 56.6% higher than achieved by the collagen sandwich functional control cultures. The success of the novel cartridge-based bioreactor in supporting hepatocytes with good viability and functional performance suggests that it is an effective design for supporting anchorage-dependent cells.

Hepatic tissue engineering: from transplantation to customized cell-based liver directed therapies from the laboratory

Today, liver transplantation is still the only curative treatment for liver failure due to end-stages liver diseases. Donor organ shortage, high cost and the need of immunosuppressive medications are still the major limitations in the field of liver transplantation. Thus, alternative innovative cell-based liver directed therapies, e.g. liver tissue engineering, are under investigation with the aim, that in future an artificial liver tissue could be created and be used for the replacement of the liver function in patients. Using cells instead of organs in this setting should permit (i) expansion of cells in an in vitro phase, (ii) genetic or immunological manipulation of cells for transplantation, (iii) tissue typing and cryopreservation in a cell bank, and (iv) the ex vivo genetic modification of patient's own cells prior re-implantation. Function and differentiation of liver cells are influenced by the three-dimensional organ architecture. The use of polymeric matrices permits the three dimensional formation of a neo-tissue and specific stimulation by adequate modification of the matrix-surface which might be essential for appropriate differentiation of transplanted cells. Additionally, culturing hepatocytes on three dimensional matrices permits culture in a flow bioreactor system with increased function and survival of the cultured cells. Based on bioreactor technology, bioartificial liver devices (BAL) are developed for extracorporeal liver support. Although BALs improved clinical and metabolic conditions, increased patient survival rates have not been proven yet. For intra-corporeal liver replacement, a concept which combines Tissue Engineering using three-dimensional, highly porous matrices with cell transplantation could be useful. In such a concept, whole liver mass transplantation, long term engraftment and function as well as correction of a metabolic defect in animal models could be achieved with a principally reversible procedure. Future studies have to investigate, which environmental conditions and transplantation system would be most suitable for the development of artificial functional liver tissue including blood supply for a potential use in a clinical setting.

Hepatic tissue engineering: from transplantation to customized cell-based liver directed therapies from the laboratory

Today, liver transplantation is still the only curative treatment for liver failure due to end-stages liver diseases. Donor organ shortage, high cost and the need of immunosuppressive medications are still the major limitations in the field of liver transplantation. Thus, alternative innovative cell-based liver directed therapies, e.g. liver tissue engineering, are under investigation with the aim, that in future an artificial liver tissue could be created and be used for the replacement of the liver function in patients. Using cells instead of organs in this setting should permit (i) expansion of cells in an in vitro phase, (ii) genetic or immunological manipulation of cells for transplantation, (iii) tissue typing and cryopreservation in a cell bank, and (iv) the ex vivo genetic modification of patient's own cells prior re-implantation. Function and differentiation of liver cells are influenced by the three-dimensional organ architecture. The use of polymeric matrices permits the three dimensional formation of a neo-tissue and specific stimulation by adequate modification of the matrix-surface which might be essential for appropriate differentiation of transplanted cells. Additionally, culturing hepatocytes on three dimensional matrices permits culture in a flow bioreactor system with increased function and survival of the cultured cells. Based on bioreactor technology, bioartificial liver devices (BAL) are developed for extracorporeal liver support. Although BALs improved clinical and metabolic conditions, increased patient survival rates have not been proven yet. For intra-corporeal liver replacement, a concept which combines Tissue Engineering using three-dimensional, highly porous matrices with cell transplantation could be useful. In such a concept, whole liver mass transplantation, long term engraftment and function as well as correction of a metabolic defect in animal models could be achieved with a principally reversible procedure. Future studies have to investigate, which environmental conditions and transplantation system would be most suitable for the development of artificial functional liver tissue including blood supply for a potential use in a clinical setting.