Direct comparison of the spread area, contractility, and migration of balb/c 3T3 fibroblasts adhered to fibronectin- and RGD-modified substrata

Native proteins are often substituted by short peptide sequences. These peptides can recapitulate key, but not all biofunctional properties of the native proteins. Here, we quantify the similarities and differences in spread area, contractile activity, and migration speed for balb/c 3T3 fibroblasts adhered to fibronectin-(FN) and Arg-Gly-Asp (RGD)-modified substrata of varying surface density. In both cases spread area has a biphasic dependence on surface ligand density (sigma) with a maximum at sigma similar to 200 molecules/mum(2), whereas the total traction force increases and reaches a plateau as a function of sigma. In addition to these qualitative similarities, there are significant quantitative differences between fibroblasts adhered to FN and RGD. For example, fibroblasts on FN have a spread area that is on average greater by similar to200 mum(2) over a similar to40-fold change in sigma. In addition, fibroblasts on FN exert similar to3-5 times more total force, which reaches a maximum at a value of sigma similar to 5 times less than for cells adhered to RGD. The data also indicate that the differences in traction are not simply a function of the degree of spreading. In fact, fibroblasts on FN (sigma similar to 2000 mum(-2)) and RGD (sigma similar to 200 mum(-2)) have both similar spread area (similar to600 mum(2)) and migration speed (similar to11 mum/h), yet the total force production is five times higher on FN than RGD (similar to0.05 dyn compared to similar to0.01 dyn). Thus, the specific interactions between fibroblasts and FN molecules must inherently allow for higher traction force generation in comparison to the interactions between fibroblasts and RGD.