Dynamic pressure transmission through agarose gels

In biomedical research, agarose gel is widely used in tissue culture system s because it permits growing cells and tissues in a three-dimensional suspe nsion. This is especially important in the application of tissue engineerin g concepts to cartilage repair because it supports the cartilage phenotype. Mechanical loading, especially compression, plays a fundamental role in th e development and repair of cartilage. It would be advantageous to develop a system where cells and tissues could be subjected to compression so that their responses can be studied. There is currently no information on the pr essure response of agarose gel when pressure is applied to the gas phase of a culture system. To understand the transmission of pressure through the g el, we set up an apparatus that would mimic an agarose suspension tissue cu lture system. This consisted of a sealed metal cylinder containing air as w ell as a layer of agarose submerged in culture medium. Pressure responses w ere recorded in the air, fluid, gel center, and gel periphery using various frequencies, pressures, gel volumes, and viscosities. Regression analyses show an almost perfect linear relation between gas and gel pressures (r(2) = 0.99987, p < 0.0001, f(x) = 0.9982 x - 0.0286). The pressure transmission was complete and immediate, throughout the range of the applied pressures, frequencies, volumes, and viscosities tested. Applying dynamic pressure to the gas phase results in reproducible pressure in the agarose and, therefo re, validates the use of agarose tissue culture systems in studies employin g dynamic pressurization in cartilage tissue engineering.