Fig. 6

Characterization of chondrogenesis in hBM-MPC cultures containing COL2A1-GFP transduced cells as sentinel cells (prepared as described in Fig. 1a and in the text). a Alcian blue staining of whole-mount and transverse sectioned samples revealed abundant moderate increases in deposition of cartilage-specific GAG deposition between 7 and 14 days of culture. Scale bar for transverse sections = 50 μm. Inset images depict a low magnification (× 10) image of each culture for reference. Scale bar = 200 μm. b Epifluorescence microscopy shows increasing expression of GFP by the transduced sentinel cells, indicating enhanced COL2A1 promoter activation during chondrogenesis. The white dashed lines indicate the location of the cultures based on the bright-field images of the same cultures. c Quantitative analysis of fluorescence (CTCF) in COL2A1-GFP transduced cells in the chondrogenic micromass cultures, showing increased fluorescence taking place between 7 and 14 days of culture, in agreement with changes in COL2A1 gene expression (fold-change) as determined by qRT-PCR in the same cultures. d Correspondence between non-invasive, fluorescence-based assay and gene expression analysis. The number of fluorescent cells per micromass did not change while CTCF/gene expression also remained constant throughout the culture period, confirming the correlation between the two outputs