Why Is the Basement Membrane Important?

Structural Support

• The most important purpose of the basement membrane is to anchor the overlying epithelial or endothelial cells and provide mechanical support. Epithelial cells are connected to basement membrane fibers by proteins such as integrins. The integrins are transmembrane proteins attached to the cell cortex on one side of the membrane and proteins attached to the basement membrane or extracellular matrix on the other. Connecting the cell's internal microskeleton to the durable fibers in the basement membrane helps reinforce the epithelial tissue against external stress.

Development

• The basement membrane can also guide cells during development. This is especially crucial during formation of new blood vessels, a process called angiogenesis. Epithelial cells often feature polarized internal organization such that one side of the cell has different functions and thus different proteins in its membrane than the other. The cells in the lining of your intestine, for example, must take up nutrients on one side and release them into the bloodstream on the other. Scientists are still working to figure out all the details of the way the body maintains this organization, but the basement membrane clearly plays a critical role.

Other Functions

• In the glomeruli of your kidney, a basement membrane acts as the initial filter in the process of urine production; it allows blood plasma to leak through while ensuring that red blood cells stay behind. The basement membrane can also play a role in cell signaling. Molecules associated with the fibrous matrix of the basement membrane can interact with integrins and other proteins in the epithelial cell, triggering a cascade of events inside.

Cancer

• The structure and function of basement membranes is linked to cancer biology. To invade neighboring tissues, cancer cells must break down the basement membrane since it acts as a barrier to their spread. For a tumor to grow, it must also be able to recruit new blood vessels, and this process begins with degradation of the basement membrane around the endothelial lining of nearby capillaries. Cancer biologists are keenly interested in understanding how cancer cells invade and recruit blood vessels and what can be done to stop them.