A packed-bed bioreactor system is provided, the system including a cell culture vessel having a first end, a second end, and a reservoir between the first and second ends; and a cell culture matrix disposed in the reservoir. The cell culture matrix includes a structurally defined substrate with a plurality of interwoven fibers having surfaces for adhering cells thereto. The substrate is disposed within the reservoir in a wound configuration creating a plurality of layers of substrate in the wound configuration, and none of the plurality of layers of substrate are separated by a spacer material.