Contraction of the fibroblast-populated collagen matrix in serum-free (A) or FBS-supplemented medium (B) in ten different fibroblast strains. The strains denoted in this Figure are different from those in Figures 1 and 2. Each data point represents a unique experiment (mean of triplicate matrix areas); total experiments = 57. Each strain had 3-14 repeats (limited by strain availability). The horizontal line associated with each data column (strain) is the mean of all triplicate means for that strain (see Table S2 in Additional File 1 for the mean and standard deviation values).