Bone and Aletered Mechanical Loading: Basic Science Approaches
Mechanical loading can regulate bone adaptation. Changes in bone could be induced by the changes in osteoblast number, which could be a result of changes in osteoprogenitor proliferation. When bone is mechanically loaded, bone cells will be exposed to the loading induced oscillatory fluid flow (OFF). How this OFF is related to the changes in bone is not well understood. One potential mechanism is that OFF can affect the changes in bone through changing the osteoprogentor activity.
To investigate the effects of OFF on marrow stromal cells (MSCs), which are the osteoprogenitors of osteoblasts.
MSCs were cultured on 0.01% poly-l-lysine coated glass slides at standard conditions of 5% CO2, 37°C and 95% humidity to subconfluent level (3 days). Cells were then subjected to 1Hz OFF at peak shear stress of 1 Pa for 2 hours. Cells cultured on slides at the same conditions with no flow served as control. These cells remained in the incubator while the flow groups were exposed to OFF. After 24 hours, cells were collected and cell proliferation were assessed by the incorporation of 5-bromo-2′-deoxyuridine (BrdU).
The fraction of cells proliferating in OFF group (26 +/− 2.7%) is significantly higer than cells in no flow group (17+/− 1.3%, p < 0.0005).
Loading induced OFF upregulates osteoblasts number by increasing the proliferation rate of MSCs.