The invention features modular chambers for culturing cells in which the volume of a chamber can be adjusted without compromising the seal or sterility of the chamber. The invention is based on the principle that the volume of a chamber formed between two plates sandwiching a compressible gasket and a substantially incompressible stop can be adjusted using a gasket that forms a fluid-tight seal between the plates at a plurality of levels of compression. The invention enables the culture of cells between substantially parallel and rigid plates in which a relatively large volume can be used to seed the cells and the holdup volume reduced for perfusion without opening or otherwise disassembling the system to compromise its liquidtightness and sterility. The new closed, modular and scalable cell-culturing chamber can be thus perfused and used to culture cells (e.g., hepatocytes) with high levels of cell function in organ (e.g., liver) assist systems, for production of cells, for production of cell-derived products, such as proteins or viruses, or for systems to treat biological liquids to remove toxins, such as ammonia, add cell-synthesized products, or both.