Fig. 5. Expression of marker genes (I) and proteins (II) during cultivation of chondrogenic cells isolated from EBs, indicating initial dedifferentiation followed by redifferentiation after prolonged cultivation. In chondrocyte cultures obtained from 5+16 d EB outgrowths mRNA levels of chondrocyte marker genes such as the adult splice variant B of collagen II (IA) and collagen X (IB) declined 4 days after isolation and were upregulated again up to 14 days after isolation. Coating of tissue culture plastic either with collagen II or gelatin did not cause significant differences. The level of transcription in relation to HPRT is shown. Significant differences (^*P0.05; ^**P0.01; ^***P0.001) in the mRNA levels for collagen IIB: 1-3, 2-4=^***; 3-7=^**; 4-8 and 3-5=^* and for collagen X: 1-3, 2-4, 5-7=^**. Mean values±s.e.m. from independent experiments (n=8) are shown. The isolated chondrogenic cells initially showed a fibroblastic morphology after one day in culture (IIA), started to form condensations after 4 days (IID) and eventually showed a round-shaped morphology after 8 days (IIG). These morphological alterations were accompanied by increasing expression of collagen II (IIB,E,H) and loss of collagen I expression (IIC,F,I) after one (IIB,C), four (IIE,F) and eight (IIH,I) days. Representative areas are shown. Bar, 100 µm.

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