Osteogenic effects of rest inserted and continuous cyclic tensile strain on hASC lines with disparate osteodifferentiation capabilities.

We investigated the effects of two types of cyclic tensile strain, continuous and rest inserted, on osteogenic differentiation of human adipose-derived adult stem cells (hASCs). The influence of these mechanical strains was tested on two hASC lines having different mineral deposition potential, with one cell line depositing approximately nine times as much calcium as the other hASC line after 14 days of culture in osteogenic medium on tissue culture plastic. Results showed that both continuous (10% strain, 1 Hz) and rest inserted cyclic tensile strain (10% strain, 1 Hz, 10 s rest after each cycle) regimens increased the amount and rate of calcium deposition for both high and low calcium depositing hASC lines as compared to unstrained controls. The response was similar for both types of tensile strain for a given cell line, however, cyclic tensile strain had a much stronger osteogenic effect on the high calcium depositing hASC line, suggesting that mechanical loading has a greater effect on cell lines that already have an innate ability to produce bone as compared to cell lines that do not. This is the first study to investigate the osteodifferentiation effects of cyclic tensile strain on hASCs and the first to show that both continuous (10%, 1 Hz) and rest inserted (10%, 1 Hz, 10 s rest) cyclic tensile strain accelerate hASC osteodifferentiation and increase calcium accretion.