Isotonic biaxial loading of fibroblast-populated collagen gels: a versatile, low-cost system for the study of mechanobiology.

We developed a simple, versatile system for applying a range of biaxial loads to cell-matrix constructs for the study of mechanobiology. The system consists of porous polyethylene bars that are polymerized into a square fibroblast-populated gel and loaded by freely hanging weights attached to sutures routed through a custom loading rig. The cost to manufacture each mold/loading rig pair was less than US dollars 250 and the expected life of the components is up to 10 years. Neonatal and adult cardiac fibroblasts contracted gels to a decreasing extent as external load was increased ( P=0.003) and achieved contraction forces of up to 1.4 mN per million cells. Strain distributions were reasonably homogeneous in the central region of the gel (25% of gel area), but clearly nonhomogeneous outside that central region. The primary advantages of this system are simplicity, low cost, biaxial loading, and the ability to test for a dose-response effect of mechanical load. The current disadvantages are the inability to apply cycling loading and the inhomogeneities introduced by the use of rigid loading bars.