In vitro cartilage formation using TGF-beta-immobilized magnetic beads and mesenchymal stem cell-magnetic bead complexes under magnetic field conditions.

We evaluated the efficacy of transforming growth factor (TGF)-beta-immobilized magnetic beads for chondrogenesis in vitro using a mesenchymal stem cell (MSC) delivery system and an external magnetic force (EMF). MSCs isolated from the bone marrow of Sprague Dawley rats were mixed with carboxyl group-combined magnetic beads (Ferri Sphere 100C) coated with anti-rat CD44 mouse monoclonal antibodies. TGF-beta3 (10 and 1 ng/mL) was attached magnetically to such other Ferri Sphere 100C beads via an amide bond formed between a primary amino group on the TGF-beta3 and the carboxyl groups on the surface of the beads. MSC-magnetic bead complexes were centrifuged to form a pellet and cultured in chondrogenic differentiation medium (CDM) supplemented with either 10 or 1 ng/mL TGF-beta-immobilized magnetic beads (10 or 1 ng/mL TGF-beta-immobilized magnetic bead groups) or in CDM supplemented with 1 or 10 ng/mL TGF-beta (1 or 10 ng/mL TGF-beta group). TGF-beta-immobilized magnetic beads were gathered effectively under an EMF. Chondrogenesis was achieved from the MSC-magnetic bead complexes in the presence of 1 ng/mL TGF-beta-immobilized magnetic beads.