Surprisingly, we found that the proliferation of PASM cells with a reduced level of ARSB depends strongly on the concentration of DS, and that DS significantly increases the rate of division of PASM cells (Figure 1), which suggest that vessel hypertrophy in MPS VI patients could be related to a dysfunction in the smooth muscle cell proliferation ratio rather than in endothelial cells. This evidence concerns the gene ARSB and mucopolysaccharidosis type 6.