For lack of sufficient human cartilage donors, chondrocytes isolated from various animal species are used for cartilage tissue
engineering. The present study was undertaken to compare key features of cultured large animal and human articular chondrocytes
of the knee joint. Primary chondrocytes were isolated from human, porcine, ovine and equine full thickness knee joint cartilage
and investigated flow cytometrically for their proliferation rate. Synthesis of extracellular matrix proteins collagen type
II, cartilage proteoglycans, collagen type I, fibronectin and cytoskeletal organization were studied in freshly isolated or
passaged chondrocytes using immunohistochemistry and western blotting. Chondrocytes morphology, proliferation, extracellular
matrix synthesis and cytoskeleton assembly differed substantially between these species. Proliferation was higher in animal
derived compared with human chondrocytes. All chondrocytes expressed a cartilage-specific extracellular matrix. However, after
monolayer expansion, cartilage proteoglycan expression was barely detectable in equine chondrocytes whereby fibronectin and
collagen type I deposition increased compared with porcine and human chondrocytes. Animal-derived chondrocytes developed more
F-actin fibers during culturing than human chondrocytes. With respect to proliferation and extracellular matrix synthesis,
human chondrocytes shared more similarity with porcine than with ovine or equine chondrocytes. These interspecies differences
in chondrocytes in vitro biology should be considered when using animal models.
Keywords Chondrocytes - Collagen type II - Proteoglycans - Knee joint - Cytoskeleton