Corneal and scleral collagen fiber formation in vitro.

We have investigated the role of structural differences in collagen molecules and the effect of proteoglycan preparations on the control of collagen fibril formation. Collagen and proteoglycans were extracted, purified and characterized from two structurally and functionally different connective tissues, rabbit corneal stroma and sclera. Corneal collagen was found to form fibers 6- to 7-times more slowly than scleral type I collagen. Proteoglycans from both sources retard fibrillogenesis, with corneal proteoglycans having approximately 3-times the effect observed with scleral proteoglycans. The morphology of the fibers formed was normal in all cases. Therefore, the changes observed may reflect a true control mechanism related to the strict morphological arrangement associated with corneal transparency.