Bone marrow-derived mesenchymal stem cells (German Sport University Cologne, Cologne, Germany)

Bone-marrow samples were flushed out from the bone, filtered (mesh 70 uM), and then subjected to Ficoll-Paque density gradient centrifugation. Cells are cultured in alpha minimum essential medium supplemented with fetal calf serum (20%), glutamine (200 uM), penicillin (100 U/ml), and streptomycin ( 100 U/ml). Cells are plated at a density of 2000 cells/cm2 and are used until passage 3.