Cell sheet engineering has received much attention in the recent years as a new approach of tissue engineering without the use of scaffold. Confluent cultured cells are harvested as an intact sheet using a temperature-responsive polymer, poly (N-isopropylacrylamide) (PNIAM) and its derivatives. Above the low critical solution temperature (LCST) of the polymer, the polymer becomes hydrophobic, allowing the cells to attach and grow. When the temperature was reduced to below its LCST, the polymer chains undergo rapid hydration and chain extension, making the polymer hydrophilic. Due to different surface properties, the cell layer, together with the underlying extracellular matrix, is detached from the surface. The extracellular matrix recovered from the culture surface allows for cell sheet stratification, making the construction of multi-layered cell sheets possible.
This technology has been applied to the treatment of articular cartilage defects. Currently, articular cartilage defects can be repaired using chondrocyte implantation. Although the clinical outcome is promising, several problems remain including low cell numbers, control of the location of the injected cells and incorporation to the host tissue. To overcome these problems, autologous transplantation of a chondrocyte cell sheet is suggested as an alternative. Chondrocytes isolated from cartilage tissue are cultured on the temperature-responsive polymer surface until confluence. At 37°C, the polymer becomes hydrophobic, allowing the cells to attach and grow. To detach the cells, the temperature is simply reduced to initiate the polymer chain extension, lifting the cells away from the culture surface. The protein matrix recovered from the culture surface allows for cell sheet stratification, making the construction of multi-layered cell sheets possible. This cell sheet can be readily transplanted to the damaged site of the cartilage. We hope that this new treatment option can potentially provide an alternative solution for pain reduction and improvement in knee functions, allowing patients with knee problems to resume their normal activities.
Assoc.Prof.Dr. Kwanchanok Viravaidya-Pasuwat