Effects of pentosan polysulfate on collagen type II deposition by micromass culture mesenchymal precursor cells. Bar graphs showing the concentration-dependent effects of pentosan polysulfate (PPS) on collagen type II deposition by mesenchymal precursor stem cells (MPCs) in micromass cultures (MMC) for (a) 5 days, (b) 7 days and (c) 10 days as determined by digital analysis of colour-intensity images of the 5-bromo-4-chloro-3'-indoyl phosphate/buffer + nitroblue tetrazolium salt stained conjugate to collagen type II applied to fixed MMC. n = 3 for each PPS concentration. Data expressed as mean ± standard deviation. (d) Digital photograph of the stained 7-day MMC cultures in 24-well culture plates after processing as described in the text showing the staining intensity in relation to PPS concentration. ‡P < 0.05, *P < 0.01; **P < 0.001; ***P < 0.0001 relative to control.