A stimulation unit for the application of mechanical strain on tissue engineered anulus fibrosus cells: a new system to induce extracellular matrix synthesis by anulus fibrosus cells dependent on cyclic mechanical strain.

A bioreactor system consisting of a multifunctional stimulation unit and common 6-well culture plate is introduced to activate extracellular matrix synthesis in intervertebral disc cells due to cyclic mechanical strain. The developed stimulation unit is sterilizable and reusable. It is viable for cultivation and mechanical stimulation of cartilage tissue and tissue engineered cell matrix constructs in combination with the common 6-well culture plate. The custom made device allows long-term cultivations in batch- or continuous operation mode. Manual handling and thereby the risk of contamination is reduced. Sampling, changing the medium, and addition of supplements are easily performed from the connected conditioning vessel. This bioreactor system enables stimulation of different samples independently during one run. For the work presented here anulus fibrosus cells from pigs were taken and immobilized in agarose to obtain three-dimensional cell matrix constructs. Over a period of 14 days the constructs were subjected to 10% compression under cyclic mechanical pressure with a frequency of 0.1 Hz. Afterwards the constructs were biochemically examined for hydroxyproline and sulphated glycosaminoglycanes. These proven constituents of extracellular matrix were found to be released depending on the applied compressive strain.