The fundamentals of tissue engineering: scaffolds and bioreactors.

Tissue engineering has the potential to provide cartilaginous constructs capable of restoring the normal function of native articular cartilage following joint injury or degradation. One approach to functional tissue engineering of cartilage involves the in vitro cultivation of tissue constructs by using: (i) chondrogenic cells that can be selected, expanded, and transfected to overexpress the genes of interest, (ii) scaffolds that provide a defined three-dimensional structure for tissue development and biodegrade at a controlled rate, and (iii) bioreactors that provide the conditions necessary for the cells to regenerate functional cartilaginous tissues. Here we explore the paradigm of tissue-engineered cartilage repair that is based on the generation of immature but functional constructs in vitro, and the remodelling and maturation of these constructs in vivo.