The Effects of Physical Forces on Cartilage Tissue Engineering

Abstract

Despite long-held beliefs to the contrary, articularcartilage, which provides articulating joints with a nearly frictionless, weight-distributing surface for transferring forces between bones, does have a limited ability for self..repair (Cheung et al., 1978; Mankin, 1982; Grande et at., 1989). With age, repeated overuse, or injury, however, natural mechanislns may be inadequate for repairing the damage. Mechanical breakdown of the articulating surfaces within freely moving (diarthrodial or synovial) joints results in osteoarthritis, which afflicts over 30 million people in the U.S. alone (Mow et al., 1992). Current treatment of severely damaged cartilage usually involves total replacement of affected joints with artificial prostheses or transplantation of donor tissue, each of which has its limitations. Artificial prostheses, because of their limited lifetime and need for replacement, are not the best option for younger patients. Donor tissue, on the other hand, is not always available, especially in the size and shape needed. Promising new therapies already in clinical use or still under study include the development of replacement cartilage ill vivo, either by injecting cells into the tissue (Brittberg et ai., 1994) or by implanting a matrix that was seeded with cells ill vitro (Frenkel et aI., 1997). Another alternative is implantation of tissue constructs that have already been partially developed in vitro. A nunlber of studies have shown that cartilage-like tissue can be regenerated in vitro, and that development of the tissue matrix is enhanced in culture systenlS simulating aspects of the native environment, ie that provide a compatible three-dimensional support. structure, good mass trdnsfer, and a physical (and/or chemical) stimulus. While progress has been made in growing tissue that has bioclzel1zical and even histological similarity, in most cases the