Effects of intermittent hydrostatic pressure magnitude on the chondrogenesis of MSCs without biochemical agents under 3D co-culture.

Without using biochemical agents, in this study, we sought to investigate the potential of controlling the differentiation of mesenchymal stem cells (MSCs) into a specific cell type through the use of 3D co-culturing and mechanical stimuli. MSCs and primary cultured chondrocytes were separately encapsulated into alginate beads, and the two types of beads were separated by a membrane. For the investigation a computer-controllable bioreactor was designed and used to engage intermittent hydrostatic pressure (IHP). Five different magnitudes (0.20, 0.10, 0.05, 0.02 MPa and no stimulation) of IHP were applied. The stimulation pattern was the same for all groups: 2 h/day for 7 days starting at 24 h after seeding; 2 and 15 min cycles of stimulating and resting, respectively. Biochemical (DNA and GAG contents), histological (Alcian blue), and RT-PCR (Col II, SOX9, AGC) analyses were performed on days 1, 5, 10, and 20. The results from these analyses showed that stimulation with higher magnitudes of IHP (≥0.10 MPa) were more effective on the proliferation and differentiation of co-cultured MSCs. Together, these data demonstrate the potential of using mechanical stimulation and co-culturing for the proliferation and differentiation of MSCs, even without biochemical agents.