Basalmembranin

Basalmembranin, commonly referred to as the basal membrane, is a thin extracellular matrix layer that lies between epithelial or endothelial cells and the underlying connective tissue. It serves as both a structural support and a selective barrier that helps define tissue boundaries and maintain cell polarity.

The basement membrane comprises two main components: the basal lamina, which is closest to the epithelium or endothelium, and the underlying reticular lamina produced by connective tissue. The basal lamina contains laminins, type IV collagen, nidogen (entactin), and heparan sulfate proteoglycans such as perlecan. The reticular lamina contains other collagens and connects to the surrounding stroma through anchoring fibrils, notably type VII collagen that helps anchor the basement membrane to connective tissue.

Functions of basalmembranin include providing mechanical support to tissues, guiding cell adhesion, migration, and differentiation, and forming a selective filtration barrier in organs such as the kidney glomerulus. It also acts as a reservoir for growth factors and signaling molecules that influence tissue repair and development.

Cellular sources of the basement membrane include epithelial and endothelial cells, as well as adjacent fibroblasts, with remodeling mediated by proteases such as matrix metalloproteinases. Changes in basement membrane composition or thickness are associated with disease and aging, and they can influence tumor invasion and metastasis by affecting barrier integrity.

Clinical relevance includes genetic disorders such as Alport syndrome, caused by mutations in type IV collagen that affect the kidney and other tissues; autoimmune conditions like Goodpasture syndrome; and diabetic nephropathy, where basement membrane thickening occurs in glomeruli. The basement membrane is a common feature across many tissues, including skin, kidney, lung, and cornea.