Method for cell expansion

A method, comprising:

• a) adding mesenchymal stem cells in a cell culture medium and microcarriers to a bag bioreactor wherein the volume of added mesenchymal stem cells and microcarriers is between 150-300 ml, the seeding density is 1-10 adherent cells/microcarrier and the amount of microcarriers is at least 0.2 g (dry weight) per liter;
• b) allowing the mesenchymal stem cells to attach to the microcarriers while the bioreactor is kept in fixed position;
• c) adding additional cell culture medium to the bioreactor once the mesenchymal stem cells are attached;
• d) culturing the mesenchymal stem cells by agitation, to yield the cell culture;
• and
• e) increasing the surface area for continued culturing, wherein the step of increasing includes:
• i. securing the bag bioreactor in an angled upright position, at an opening in an upper corner of the bag bioreactor, by an external component such that the microcarriers are moved by gravity to a single corner inside the bag bioreactor opposite the upper corner;
• ii. collecting the microcarriers by sedimentation in the single corner of the bag bioreactor, the microcarriers having the mesenchymal stem cells attached thereon;
• iii. transferring the collected microcarriers to an external separation device using gravity flow or overpressure on the bag bioreactor
• iv. detaching the mesenchymal stem cells from the microcarriers inside the external separation device;
• v. separating the detached mesenchymal stem cells from the microcarriers by flowing, under agitation, a buffer through the external separation device;
• vi. adding new microcarriers and the detached mesenchymal stem cells to the bag bioreactor for continued culturing;
• f) harvesting the mesenchymal stem cells of step e) by active detachment and separation;
• wherein step e) is repeated until 3-8 g microcarriers per liter medium is reached;
• and wherein one therapeutic cell dose of mesenchymal stem cells can be produced per 2 liter of culture volume.