Formation of the basement membrane during regeneration of the corneal epithelium

Summary The epithelium regenerating after a surface lesion of the cornea forms a new basement membrane. This process begins 6–8 days after the lesion when the wound is completely covered, and epithelial cells have ceased to migrate. Only that part of the epithelial cells facing the stroma is involved. First, tufts of fine filamentous structures (about 30 Å thick) appear on the internal side of the plasma membrane, and apparently penetrate it reaching the extracellular space where they form a loose network. This then differentiates into two discrete layers, a very thin discontinuous one, restricted to areas with tufts, very close to the plasma membrane (juxtamembranous layer), and a thick continuous layer, the basement membrane proper, parallel to and much further away from the plasma membrane. The basement membrane appears to be the product of cytoplasmic secretion by epithelial cells, and there is no evidence for connective tissue cells taking part in this process.Supported by the Deutsche Forschungsgemeinschaft.