Progress in cartilage tissue engineering with nanostructured extracellular matrix

Tissue defects and organ failure have seriously threatened the health and life of human beings and are challenges in modem medicine we have been trying to overcome. They are often treated with tissue and organ transplantation. Although autologous tissue transplantation is not bothered by immune rejection, it could cause defects of the donor site and create new pains. Therefore, scientists are striving to explore more ideal principles and methods while working hard to improve the existing treatments as most as possible. The rise and development of tissue engineering will be possible to provide adequate safe "autologous" tissues and organs to repair human body. Cartilage damage is one of the main causes of osteoarthritis. However, it has limited self-repair ability. Thus, cartilage tissue engineering, especially nanomaterials as a new treatment modality provides a therapeutic potential. Cartilage consists of a small amount of chondrocytes and highly dense, nanostructured extracellular matrix, which is assembled by collagen fibers, proteoglycans and elastin fibers. As the cartilage tissue has no nutrient vessel and nerve distribution, its blood supply mainly relies on material exchange through osmosis between capillaries in its membrane. Since chondrocytes lack migration capability, cartilage tissue has limited self-repair ability after injury. When traumatic articular cartilage damage occurs, articular cartilage injury caused pain would eventually form osteoarthritis. Traditionally, articular cartilage injury is treated with debridement and flushing. Such methods may mitigate and reduce small cartilage damage in a short period. However, their long-term outcome is poor. In addition, osteoarthritis and joint space narrowing often occur in patients with defect greater than 1 cm(2)[1,2,3]. Further in-depth researches found that hole drilling repair surgery could lead to the formation of fibrocartilage rather than hyaline cartilage. Homminga et al[4]showed that twenty-five patients with 30 chondral lesions of the knee were treated with an autogenous strip of costal perichondrium. the defect in the 28 cases was completely filled with tissue resembling articular cartilage. Since Green[5]successfully isolated and cultured chondrocytes and tried to co-culture them with demineralized bone scaffold materials, which create a new research direction for cartilage regeneration and repair, complete reconstruction and recovery of cartilage anatomically and functionally at defect sites becomes possible through tissue engineering.