Tissue Spreading Rate Dependence on Extracellular Matrix Concentration*

The collective migration of tissues is an essential part of development. In order to understand this process, we must understand the physical mechanisms that drive these movements. In order for tissue to self-propagate, they must form adhesions to their substrate. To study the rate of tissue spreading, I varied the number of adhesion sites. I began by cutting the tissue explants from gastrulation-stage Axolotl (Ambystoma mexicanum) embryos, removing a tissue that spreads across the surface of the embryo. These tissue explants spread in a similar manner when placed onto a fibronectin-coated substrate. By varying the concentration of fibronectin, an extracellular matrix protein, I tested the effect of the number of adhesion sites on the rate of tissue spreading. Initial analysis showed that over a concentration of 25 µg/ml, changes in fibronectin concentration no longer had an effect on the spreading rate of tissue. These results will allow us to conduct future experiments on tissue spreading in a regime where slight variations in fibronectin-coating are unlikely to affect spreading rate.