Isolation and in vitro proliferation of chondrocytes, tenocytes, and ligament cells.

In recent years it has become possible to grow large numbers of selected cell types in vitro from relatively small tissue samples. This capability has served as the foundation for using autogenous, as well as allogeneic, cells expanded in culture for engineering tissues that display little potential for spontaneous regeneration. Cartilage, tendons, and ligaments are connective tissues that have common attributes that limit their capabilities of regeneration (Table 1). These tissues are relatively avascular, sparsely populated with cells, and their cell populations have a low mitotic activity. Because the use of allogeneic grafts brings with it concerns regarding transfer of disease and immunological rejection of the foreign material, the availability of an autologous system for regeneration of these tissues is of paramount importance for restoring joint function and preventing further degeneration. Table 1 Characteristics of Adult Tissue Articular Cartilage Ligament Cruciate Collateral Cell type Chondrocyte Fibroblast/Fibrochondrocyte Fibroblast Fibroblast Cell density Low(1.4-1.7 × 10(4) cell/mm(3))(1) Low (2.7μg DNA/mg dry wt)(5) Low (2.6μg DNA/mg dry wt)(5) Low (1.5μg DNA/mg dry wt)(5) Mitotic activity Low Low Low Low Predominant collagen type II I I I Vascularity No Low Low Low Substrate for Phenotype preservation 3D Hydrogel (viz,agarose) 2D Culture plates 2D Plates 2D Plates Repair capacity Low Low High Low.