Who's got pull around here? Cell organization in development and tissue engineering

How cells organize into structured tissues has been a long-standing question for the field of developmental biology (1). Whereas many of the key cellular and extracellular regulatory components have become identified over the past decades, including soluble growth factors and insoluble matrix factors in the environment and receptors on the cells themselves, fundamental principles by which molecular regulatory processes govern resulting cell–cell interactions remain largely unclear. More recently, a nascent medical technology field of tissue engineering has arisen that can be viewed essentially as applied developmental biology—with bioengineers seeking to control for their own purposes cell population organization into functional tissue structures, often employing biomaterials approaches (2). Success in this technology field, correspondingly, depends similarly on elucidating how cell organizational processes are governed by interactions of cell receptors with cognate ligands in their surroundings. In this issue of PNAS, a collaborative effort combining biomaterials and molecular cell biology methodologies provides an important advance in both the fields of developmental biology and tissue engineering (3).