Fig. 6. Graph of quantitative representation of cell-mediated gel contraction in vitro. One hundred thousand human dermal fibroblasts (HDF) contract gel to less than 10% its original volume. In contrast, 100,000 human retinal pigment epithelial (HRPE) cells produce negligible change at a similar time interval. One million cultured HRPE cells reduce gel volume by more than 70% after 120 hours.