Synergistic Effects of Conditioned Media and Hydrostatic Pressure on the Differentiation of Mesenchymal Stem Cells

The objective of this study was to investigate the effect of mechanical stimuli in combination with conditioned media (CM) on the osteogenic and chondrogenic differentiation of mesenchymal stem cells (MSCs). Two “opposing” groups were defined for the study. The first, designated the bone group, was formed by seeding MSCs onto porous poly(l-lactide-co-ε-caprolactone)/hydroxyapatite scaffolds. The second group, designated the cartilage group, was formed by encapsulating MSCs in 2% agarose. The samples were either subjected to hydrostatic pressure (HP), administered CM from the opposing group at a concentration of 50%, or given a combination of the two stimuli. The sulfated glycosaminoglycan (sGAG) content and SOX9, aggrecan, and collagen type II expressions suggest that both osteoblast CM and intermittent HP individually enhanced the chondrogenic differentiation of MSCs. In addition, there is evidence of a synergistic interaction between CM and HP on chondrogenic differentiation. The alkaline phosphatase (ALP) activity and osteocalcin and bone sialoprotein expression suggest that the combination of chondrocyte CM and HP significantly enhanced the osteogenic differentiation of MSCs. However, the individual stimuli did not have a significant effect on osteogenic differentiation. Enzyme-linked immunosorbent assay (ELISA) results revealed that both the chondrocyte CM and osteoblast CM contained considerable amounts of TGF-β1 and BMP-2.