Apparatuses, systems, and methods are provided for growing and maintaining cells. A three-dimensional matrix, such as a hydrogel material, is seeded with cells and placed in a bioreactor having two compartments. The matrix is supported between the two compartments by first and second porous materials, which engage opposing surfaces of the matrix. A first media stream having certain properties is propagated through the first compartment, where it contacts one surface of the matrix via the first porous material. A second media stream having different properties is propagated through the second compartment such that it contacts the opposite surface of the matrix via the second porous material. Through migration of each stream at least partially into the matrix, various controlled gradients may be established within the matrix, encouraging growth of the cells. Such gradients include osmotic pressure, oscillating osmotic pressure, hydrostatic pressure, oxygen tension, and/or nutrient gradients.