Figure 4: Expression of chondrogenic markers in ATDC5 cells cultured on hydrogels with various charge density; Polystyrene dish (PS), PDMAAm gel, P(AMPS-co-DMAAm) (molar fraction of AMPS, , 0.75), and PAMPS gel, in the absence of insulin. Scale bar, 100 μm. Expression of type II collagen was analyzed by immunofluorescent staining at 14 days of culture. The cells were stained with an antitype II collagen antibody (green) and Hoechst 33258 (red). Reproduced with permission from [22]. © 2010, Elsevier, Inc.