Method of preparing a conditioned medium from a confluent stromal cell culture

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 substrate in the form of a sheet, said substrate including a non-woven fibrous matrix forming a physiologically acceptable three-dimensional network to obtain a stationary phase three-dimensional confluent stromal cell culture, wherein said stromal cell culture is grown to a density of at least 5×106 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, said medium useful in expanding an undifferentiated hemopoietic stem cell culture to increase the number of the undifferentiated hemopoietic stem cells.