Mesenchymal stem cell transplantation constructs and protocols. (A) In bone marrow-derived cell (BMDC) transplantation, the bone marrow aspirate is centrifuged to create a BMDC concentrate that contains mesenchymal stem cells (MSCs) within a pool of other cells and chemical mediators. BMDCs are then seeded onto a scaffold and implanted within a cartilage defect. (B,C) MSC transplantation involves isolating MSCs from a bone marrow aspirate by plastic adherence and expansion in plastic tissue culture flasks. MSCs are then seeded onto a scaffold and implanted (B) or precultivated in vitro to promote chondrogenesis prior to implantation (C).