Type I collagen and fibronectin synthesis by retrocorneal fibrous membrane.

The primary cultures obtained from the experimentally induced retrocorneal fibrous membrane synthesized and secreted into the medium mainly type I procollagen. This collagen was characterized after limited pepsin treatment and identified as type I collagen by the following criteria: (1) it contained two alpha 1 chains and one alpha 2 chain, (2) its sedimentation behavior was identical to that of type I collagen from skin, and (3) its peptide map after limited proteolysis with Staphylococcus aureus V8 protease was identical to that of type I collagen. The medium contained procollagen I, which was converted into alpha size chains by limited pepsin treatment, whereas the cellular fraction contained type I collagen already processed to its end product. Type III collagen and basement membrane collagen were present as minor components in this system Fibronectin, one of the major glycoproteins in extracellular matrices, was also synthesized and secreted into the medium. In contrast, normal corneal endothelial cells produce mainly basement membrane collagen.