Evaluation of chondrocytes expression embedded in thermoresponsive poly(amino acid)s with sol-gel transition

Poly(N-substituted alpha/beta-asparagine) was evaluated as a thermoresponsible and an injectable scaffold for cartilage regeneration. Solutions of this polymer are liquid state below 25 degrees C and nonfluid hydrogel above 35 degrees C, allowing an aqueous solution containing cells at room temperature to form a hydrogel with encapsulated cells at physiological body temperature. Chondrocytes were isolated from joint of 4-week-old Japanese white rabbits, dispersed within the thermoresponsive polymer solution and maintained for up to 72 hours in vitro. The polymer solutions demonstrated concentration-dependent inhibitory effect on chondrocytes multiplication. After the three-day cultivation, the survival rate of the chondrocytes fell into a 70~90% ranges among all the tested polymer concentrations. The morphology studies showed that there were some physical and/or chemical stress leading cells to necrosis and some extent apoptosis. Some physical and/or chemical stress may be applied, and over 70% of the chondrocytes could survive through the stress, suggesting that some phenotype could have been selected from the heterogeneous mixture of chondrocytes.