ABSTRACT
The cells comprising the vertebrate lung are derived from the endoderm and mesoderm of the developing embryo. Bidirectional interactions between these two tissue layers have been shown to be essential for the proper development of the lung (1). In the mouse, the lung epithelial cells come from the primitive foregut around embryonic day 9.5 (E9.5) and invade the surrounding splanchnic mesenchyme (2). As development proceeds, these cells proliferate and differentiate into the cells that will form the mature lung. This process requires activation of cell-specific transcription factors and occurs under the influence of a number of growth factors, many of which act in a paracrine or autocrine manner. Epithelial-mesenchymal interactions play an important role in branching morphogenesis and proximal-distal airway differentiation. Epithelial-endothelial interactions assist in vascularization of the lung and development of the blood-air interface, which allows the organ to carry out gas exchange. This chapter focuses on the growth factors involved in early lung development, with emphasis on those factors involved in cell-cell interactions that aid in cell-fate decisions (Fig. 1).
