Xenogeneic protein-free cultivation of mesenchymal stromal cells - towards clinical applications.

We have studied a rapid cultivation method for human mesenchymal stromal cells based on CellGroTM medium and human serum, supplemented with insulin, ascorbic acid, dexamethasone, epidermal growth factor, platelet-derived growth factor BB, macrophage colony-stimulating factor and fibroblast growth factor 2. This study has shown that rapid expansion of human multipotent mesenchymal stromal cells using human serum could not be achieved without addition of growth factors. Furthermore, we have found that insulin and, quite probably, epidermal growth factor may be omitted from our formula without loss of colony-forming capacity or total cell yield. On the other hand, dexamethasone, ascorbic acid and fibroblast growth factor 2 were necessary for the growth and colony-forming capacity of multipotent mesenchymal stromal cells, while platelet-derived growth factor BB prevented their differentiation into adipogenic lineage. Moreover, multipotent mesenchymal stromal cells cultivated in our system expressed higher levels of bone morphogenetic protein 2, but not bone morphogenetic protein 7, than cells cultivated in α-MEM with foetal bovine serum. This shows that our system promotes differentiation of mesenchymal cells towards osteogenic and chondrogenic lineages, making them more suitable for bone and cartilage engineering than cells grown in conventional media. Furthermore, we have proved that these cells may be conveniently cultivated in a closed system, in vessels certified for clinical use (RoboFlaskTM), making the transfer of our cultivation technology to good clinical practice easier and more convenient.