Electron-microscopic studies on the presence of gap junctions between corneal fibroblasts in rabbits

Corneal fibroblasts, major cellular components of the corneal stroma, are loosely arrayed between collagen lamellae. They play an important role in the metabolic and physiological homeostasis mechanisms by which the cornea is kept transparent. This paper deals with the demonstration of the gap junctions between the corneal fibroblasts of rabbits by transmission electron microscopy of thin sections and of freeze-fracture specimens. Under the transmission electron microscope, the corneal fibroblasts are seen between the lamellae of collagen fibers of the corneal stroma. Their long cytoplasmic processes are in contact with those of neighboring fibroblasts. Typical gap junctions are found between these cytoplasmic processes. In the freeze-fracture images, intramembrane particles with a diameter of 10.3 nm form polygonal aggregates on P faces. These findings suggest that corneal fibroblasts, coupled with each other, might function synchronously through gap junctions responsible for metabolic activities essential for the maintenance of corneal transparency.