The present invention concerns a method of preparing a conditioned medium from a confluent stromal cell culture, the method comprising: (a) culturing stromal cells to confluence in a stationary phase plug-flow bioreactor under continuous flow of medium on a three dimensional substrate to obtain a stationary phase three-dimensional confluent stromal cell culture, wherein said stromal cell culture is grown to a density of at least 5 x 10 6 cells per a cubic centimeter of said substrate and (b) separating and collecting a stromal cell conditioned medium from said stationary phase confluent stromal cell culture thereby obtaining the conditioned medium.
