To be applied in sufficient numbers for regenerative medicine, primary mesenchymal stem cells (MSCs) need to be amplified in culture. Standard cell culture involves regular passing because MSC proliferation in size-limited culture vessels stagnates due to contact inhibition of growth. The use of harmful enzymes for passaging and the mechanical properties of standard culture vessels change the MSC phenotype. Initially, fast growing multipotent and regenerative MSCs will turn into slowly growing cells with reduced multipotency and fibrotic character. We here describe an innovative culture system that maintains overall constant cell densities which are near-optimal for proliferation, while preventing contact-inhibition of cell growth. This is achieved by dynamically enlarging a novel highly elastic culture dish using a motorized mechanical device and adapting the culture surface to the increasing cell numbers. Dynamic MSC culture expansion reduces the number of enzymatic passages by a factor of 3 and delivers higher MSC yields than conventional culture. On the expanded culture surface, MSCs maintain stem cell characteristics and high growth rates over months and are still inducible to follow different lineages thereafter.
