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.

	Articular Cartilage	Ligament
		Cruciate	Collateral
Cell type	Chondrocyte	Fibroblast/Fibrochondrocyte	Fibroblast	Fibroblast
Cell density	Low(1.4–1.7 � 104 cell/mm3 )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