Mesenchymal Influence on Salivary Gland Morphogenesis

The underlying mesenchyme plays an active role in epithelial cell morphogenesis. It is responsible for beginning epithelial cell clefting and determining the structural shape of the branches. The general presence of the mesenchyme is necessary to induce the branching morphogenesis of each gland. Lawson (1974) demonstrated that the mesenchyme was needed for the branching morphogenesis of salivary glands, but salivary mesenchyme was not the only mesenchyme that could cause this differentiation. Lung mesenchyme could also support morphogenesis of mouse oral epithelium (Lawson, 1974) (Figure 1). This allowed for the assumption that there are similar morphogens in mesenchyme that naturally support a branching morphogenesis like the mesenchyme of the lungs and salivary glands.

Figure 1: The topmost figure represents mouse epithelium that has been cultured in its own mesenchyme. The lower four figures demonstrate the effect lung mesenchyme has on the branching morphogenesis of the mouse epithelium. The characteristic branching is still evident (Figure from Lawson, 1974).

Many of the mesenchymal-epithelial interactions are permissible by the basement membrane formed by the mesenchyme and the epithelium. It is not a uniform structure as it has gaps which allow the epithelium and the mesenchyme to directly touch each other, though this is not always necessary as diffusible agents exist. There are various intricacies to the interactions of the two types of cells. One seems to be a mechanical aspect by which the migrating epithelial cells cause the epithelial cells to alter their configuration. The other form of interaction comes from diffusible agents that are transported between the layers.

Link to the Mechanical Aspects of Mesenchymal influence on Epithelial branching

Link to Epithelial changes caused by Diffusible Mesenchymal Agents

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