Modification of proteoglycan synthesis by corneal stromal cells on co-culture with either epithelial or endothelial cells.

Corneal stromal cells, prepared from 2-day-old chicks and embedded in collagen gel on an insert dish, were co-cultured with corneal epithelial cells or endothelial cells on a fibronectin-coated companion plate. Cell growth and proteoglycan synthesis, as determined as the incorporation of [35S] sulfate and [3H] glucosamine, were examined for each cell type in both combinations. In comparison with single cultures, growth was affected little, while proteoglycan synthesis was appreciably altered in both combinations. Stromal and epithelial cells stimulated proteoglycan synthesis by each other, while endothelial cells stimulated the synthesis by stromal cells, but stromal cells reduced that by endothelial cells to some extent. Endothelial cells alone synthesized proteoglycans much more actively than did epithelial or stromal cells. Analysis of the radiolabeled proteoglycans revealed that endothelial and epithelial cells had different effects on proteoglycan synthesis by stromal cells: the former tended to increase keratan sulfate synthesis by stromal cells, while the latter tended to increase chondroitin sulfate/dermatan sulfate synthesis. Proteoglycan synthesis in the corneal stroma in vivo might thus be controlled by the balance between the antipodal actions of the epithelial and endothelial cell layers.