Regaining chondrocyte phenotype in thermosensitive gel culture

Chondrocyte tissue engineering continues to be a challenging problem, When chondrocytes are duplicated in vitro, it is imperative to obtain an adequat e number of cells of optimal phenotype. A temperature-sensitive polymer gel , a copolymer of poly(N-isopropylacrylamide) and acrylic acid (PNiPAAm-co-A ac), has the ability of gelling at 37 degreesC (the lower critical solution temperature, LCST) or above and liquefying below that temperature (Vernon and Gutowska, Macromol. Symp. 1996;109:155-167). The hypothesis of this stu dy was that chondrocytes could (1) duplicate in the copolymer gel; (2) rega in their chondrocyte phenotype; and (3) be easily recovered from the gel by simply lowering the temperature below 37 degreesC. Chondrocytes from adult rabbit scapular cartilage were harvested and cultured in a monolayer cultu re until confluency (approximately 2 weeks). Next, the cells were harvested and seeded into the copolymer gel and cultured for 2-4 weeks. The phenotyp e of the cultured cells was then characterized. Two groups of control cultu res, monolayer and agarose gel, were used to compare their ability to maint ain chondrocyte phenotype. The results showed that chondrocytes isolated fr om rabbit scapula can re-express chondrocyte phenotype in agarose culture a nd polymer gel culture but not in monolayer culture. Also, cultured chondro cytes can be easily recovered from polymer gel culture by simply lowering t he temperature. This new in vitro method of chondrocyte culture is recommen ded for chondrocyte propagation and regaining chondrocyte phenotype before cell seeding or transplantation. Anat Rec 263:336-341,2001. (C) 2001 Wiley- Liss,Inc.