Effects of various patterns of intermittent hydrostatic pressure on the osteogenic differentiation of mesenchymal stem cells

This study investigated the effects of intemittent hydrostatic pressure (IHP) patterns on the responses of mesenchymal stem cells (MSCs) such as osteogenic differentiation, proliferation and senescence. For these experimental groups were set based on IHP patterns: (1) C_BM: control group with no stimulation in basal media; (2) C_OM: control group with no stimulation in osteogenic media (OM); (3) S_2H/5M: longer pressurizing (2hours) and shorter resting (5minutes) time in OM; (4) S_1H/1H: equal pressurizing and resting time (1hour) in OM; (5) S_2M/15M: shorter pressurizing (2minutes) and longer resting (15minutes) time in OM. The magnitude of IHP was 0.15 MPa. IHP was applied to corresponding groups for 4 hours a day from 3 days starting at 48 hours after seeding. Examination of DNA contents, ALP activity and its staining, quantitative real-time PCR, and β-galactosidase staining were performed. ALP amount normalized by corresponding DNA content in S_2H/5M, C_BM was significantly lower than that of the other group at day 5, which was more observable even at day 7 while S_2H/5M significantly had lower ALP count than other groups at day 5 and day 7. Other groups (S_1H/1H and S_2M/15M) showed significantly higher ALP amounts indicating the positive effect on osteogenic differentiation. Other markers indicating the degrees of differentiation showed comparable results. Based on β-galactosidase staining, it appeared that mechanical stimuli did not affect cell senescence significantly. From this study, we concluded that engagement of IHP has a potential of controlling osteogenic differentiation depending on its pattern: it can promote or suppress differentiation.