Figure 1.

Active fluid transport, driven by solute and ion pumping and powered by ATP hydrolysis, can alter cell and tissue shape. Such changes during morphogenesis can be explained by the interplay between ion transport, fluid transport and cell mechanics. Three examples are illustrated: (a) To form a lumen, cells in the lumen wall actively regulate solute and water flux, leading to a buildup of luminal hydraulic (Ρ_in; blue) and osmotic pressures (∏_in; green). These pressures are intricately coupled with the mechanics of the cells forming the lumen wall. Additionally, the tension in the lumen wall further modulates fluid transport properties, creating a dynamic feedback loop. (b) During sprouting angiogenesis, shear stress, solute transport, and hydrostatic pressure gradients influence migrating endothelial cells, enabling them to branch and move into avascular tissues. (c) The circulatory system is a network of active fluid pumps that establish natural osmotic and hydrostatic pressure gradients. Just as in an electrical circuit (superimposed on top of the circulatory system schematic), where the behaviour of the circuit depends on the combined effects of all its components, the osmolarity and hydraulic pressure at various points of the circulatory network, in turn, influences cell pumping properties and gene expression.