Artificial Organs 29(3):264–267, Blackwell Publishing, Inc. © 2005 International Center for Artificial Organs and Transplantation 264 Blackwell Science, LtdOxford, UKAORArtificial Organs0160-564X2005 International Society for Artificial OrgansMarch 2005293264267Miscellaneous THOUGHTS AND PROGRESSTHOUGHTS AND PROGRESS Received March 2004; revised August 2004. Address correspondence and reprint requests to Dr. Igor M. Sauer, Visceral and Transplantation Surgery, Experimental Surgery and Regenerative Medicine, Charité, Campus Virchow, Augustenburger Platz 1, 13353 Berlin, Germany. E-mail: igor.sauer@charite.de Thoughts and Progress The SlideReactor—A Simple Hollow Fiber Based Bioreactor Suitable for Light Microscopy *Igor M. Sauer, *Ruth Schwartlander, *Jochen Schmid, *Ekaterina Efimova, *Florian W.R. Vondran, *Daniel Kehr, *Gesine Pless, *Antonio Spinelli, †Börries Brandenburg, †Eberhardt Hildt, and *Peter Neuhaus *Visceral and Transplantation Surgery, Experimental Surgery and Regenerative Medicine Charité—Campus Virchow Universitätsmedizin Berlin; †Robert Koch Institute, Molecular Virology NG1, Berlin, Germany Abstract: Most bioartificial liver support systems are based on hollow fiber capillaries within modified dialysis cartridges or more sophisticated bioreactor constructions. Due to their design microscopic follow-up of reorganiza- tion and growth of tissue between the hollow fibers is not possible. The SlideReactor is a simple hollow fiber based bioreactor construction suitable for light microscopy and time-lapse video observation. The SlideReactor offers a cell compartment separated from a medium inflow and outflow compartment. Cell compartment access ports enable easy filling of the cell compartment with cell sus- pension, as well as fixation of the tissue. For more complex procedures or full access to all the cells, the bioreactor can be opened easily by cutting the silicone seal with a scalpel. Due to its simple design and the utilization of standard materials, it could serve as a suitable, cost-efficient tool to evaluate the behavior of cells cultured between hollow fiber capillaries. The paper describes the production pro- cess: similar to open source projects in software engineer- ing, we would like to propose the concept as an open platform to anyone interested in hollow fiber based cell culture. Key Words: Bioreactor—Microscopy—Hollow fibers—Time-lapse video microscopy—Cell culture. Conventional culture techniques lead to an alter- ation in the environmental conditions of liver cells in comparison to their in vivo situation. Electron microscopy investigations have demonstrated that major differences in the ultrastructure of hepatocytes can be observed when cultured, using monolayer techniques. Important findings are the endocytosis of the junctional complexes with secondary effects on the orientation of the cytoskeleton and cell organelles (1). If a culture model could support high cell densities (2), as well as a free three-dimensional cell rearrangement, a more physiological microenvi- ronment of hepatocytes could be established. Cell- to-cell aggregation would enable the reconstruction of functional complexes, as well as the reorientation of the cytoskeleton and cell organelles in vitro (3). Furthermore, a liver tissue-like formation of paren- chymal and nonparenchymal cells is thought to sup- port cellular orientation and differentiated function. A culture technique in which the different cell populations can reorganize themselves into three- dimensional structures may result in a hepatocyte microenvironment similar to the physiological situa- tion along the liver sinusoids. An early approach to cultivate an appropriate quantity of cells under conditions acceptable for cell culture and clinical use, was the use of hollow fiber capillaries within modified dialysis and plasma sepa- ration cartridges. In addition to cell immobilization, capillary membranes allow: gas exchange, substrate supply, waste removal, and easy interface with the blood or plasma circuit of the patient during clinical application. Modified dialysis cartridges or more sophisticated bioreactors enable the clinical use of liver cells. These systems consist of a collection of hollow fiber capillaries through which the patient’s blood or plasma is pumped (4). Within the Extra- corporeal Liver Assist Device (ELAD) cells are inoculated into the extracapillary space (5). An- other design (Academisch-Medisch-Centrum Bio- Artificial Liver, AMC-BAL) by Chamuleau and coworkers incorporates a spirally wound polyester matrix sheet which includes an integral hollow-fiber compartment for oxygenation (6). The CellModule uses independently perfused but interwoven hollow fiber membranes to create a three-dimensional frame- work over which self-assembling hepatocyte aggre- gates are distributed (7,8). By using hollow fiber capillaries these bioreactors imitate the conditions in the natural liver where each hepatocyte is in close contact with the intrahepatic blood vessels. Since these systems are not suitable for direct anal- ysis of the reorganization or growth of tissue between