A three-dimensional dynamic coculture system enabling facile cell separation for chondrogenesis of mesenchymal stem cells

Coculture has emerged as a strategy to improve chondrogenesisof mesenchymal stem cells (MSCs) for cartilage regeneration. In the present study, a new system integrating cell encapsulation, dynamic stimulation and coculture with articular chondrocytes (ACs), termed as three-dimensional (3D) dynamic coculture, was developed for chondrogenic differentiation of MSCs. In addition, a novel mechanism was exploited to enable facile separation of cocultured cells. Rabbit bone-marrow derived MSCs (rMSCs) and rabbit ACs (rACs) were encapsualted in alginate gel beads, respectively. In rACs-laden beads, magnetic Fe3O4 nanoparticles were incorporated. Dynamic coculture was performed in a spinner flask. Fe3O4 nanoparticles had no negative effects on growth of rACs, although a slight inhibition on production of glycosaminoglycans (GAG) by rACs was noticed. An alginate concentration of above 1.8 w/v% was favorable for dynamic culture of rMSCs and rACs. Coculturing rMSCs with rACs in chondrogenic medium in this system demonstrated an improved chondrogenesis than monocultured rMSCs according to GAG quantification, histological staining, and gene expression analysis of collagen I, II and X. However, supplementation of 2% FBS did not show posive effects on chondrogenesis of cocultured rMSCs. This proof-of-concept study demonstrates that such a separable 3D dynamic coculture system holds great potential in cartilage tissue regeneration.