Cell‐ and Tissue‐mechanics of Apical Contraction in Embryonic Epithelia

Abstract

Apical contraction is one of the principle cellular mechanisms that sculpt epithelial sheets into structures such as tubes, pits, and furrows. In order to investigate the mechanics of apical contraction and epithelial morphogenesis in vertebrates we have developed three methods (chemical‐, electrical‐, and laser‐activation) to induce contraction in embryonic epithelia of the frog Xenopus laevis. We use these methods together with a biomechanical analytical framework to investigate the molecular signaling pathways regulating contraction and the mechanical coupling of these pathways to tissue movements. Thus far, we find pathways that control exogenously induced contractions are similar to the programs that regulate native epithelial morphogenesis. For instance, laser‐activation induces a Ca++ wave, activates RhoGTPase, and drives F‐actin remodeling. Epithelial stiffness and force‐generation measured during electrically induced contraction suggests these two properties are mechanically independent. In contrast to single‐cell studies we have found no evidence that mechanical‐stimulation can induce apical contraction. In addition to our results on the molecular and mechanical regulation of apical contraction our studies suggest morphogenetic processes can be co‐opted by tissue engineers to build replacement tissues and construct artificial organs.