Modulation of endothelial cell morphology and collagen synthesis by polymorphonuclear leukocytes

Primary corneal endothelial monolayers exposed to polymorphonuclear leukocytes undergo a series of morphologic alterations. Elongation occurred in foci within 3 days after removal of polymorphonuclear leukocytes, the modulated endothelial foci grew into fibroblastic colonies, and the fibroblastic cells eventually overgrew the endothelial cells. Control cultures of endothelial cells originated from confluent monolayers became enlarged, attenuated and lost their characteristic polygonal shape within 10 days following postconfluency , but no fibroblastic changes were seen. "Wounding" the endothelial monolayer with a focal freeze resulted in death of cells with slow regeneration. In the presence of polymorphonuclear leukocytes, cell migration into the wound was enhanced, and there was selective proliferation of fibroblastic cells. Indirect immunofluorescent studies showed that anti-type I collagen antibodies stained the fibroblastic foci in the polymorphonuclear leukocyte-treated endothelial cells and the fully modulated endothelial cells. The fully modulated cells also showed loss of contact inhibition leading to mutilayering of cells and extracellular matrices, which accumulated not only between the basal cell layers and plastic substratum but also in the cellular interstices. When collagen phenotype was analyzed by SDS electrophoresis in comparison with corneal endothelial phenotypes (type IV collagen), type I procollagen synthesis became evident in the secondary subculture originated from polymorphonuclear leukocyte-treated endothelial cells. Limited pepsin treatment gave rise to type I collagen as a major collagenous peptide. Polymorphonuclear leukocytes, thus, apparently contribute to the modulation of endothelial cells into fibroblastic cells, which also switch their collagen phenotype from type IV to type I collagen synthesis.