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

Abstract

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.

Galardin Inhibits Collagen Degradation by Rabbit Keratocytes by Inhibiting the Activation of Pro-Matrix Metalloproteinases

“…These cells also transformed and became elongated and spindleshaped, with long processes that extended and developed gap junctions with neighboring cells (Nishida et al, 1988). The ultrastructure of keratocytes in collagen gels resembles that found in normal keratocytes in vivo (Ueda et al, 1987). Langholtz and co-workers investigated collagen lattice contraction by the skin fibroblasts in this three-dimensional in-vitro model (Langholtz et al, 1995), and other researchers have studied the regulation of collagen and collagenase gene expression by skin fibroblasts in a collagen gel (Mauch et al, 1988(Mauch et al, , 1989.…”

“…In the corneal stroma, keratocytes are embedded in extracellular matrix proteins, mainly type I collagen ; the cells' functions are continuously modulated by interaction with this extracellular matrix. Thus, threedimensional culture of keratocytes in collagen gel represents the conditions more closely related to the situation in vivo than does monolayer culture (Ueda et al, 1987 ;Nishida et al, 1988). The present study used this model to examine the inhibitory action of Galardin on collagen degradation by keratocytes.…”

Gap Junctions between Fibroblasts in Rat Myotendon.

“…The existence of gap junctions between fibroblasts in the rabbit cornea (VEDA et al, 1987) and between fibroblast-like cells in the guinea-pig small intestine (ZHou et al, 1992) has been reported. However, several investigators found no junctions between the fibroblasts in the myotendon in previous studies (GELBER et al, 1960;MACKAY et al, 1969;NAKAO,1976;TROTER et al, 1981), while others found intermediate junctions of the zonula adherens type between fibroblasts in the rat flexor digital tendon and in the rat tendon tail (FARQUHAR and PALADE, 1963;GREENLEE and Ross, 1967;SQUIER and BAUSCH, 1984).…”

Characteristic Morphology and Distribution of Bone Marrow Derived Cells in the Cornea

“…Previous studies of rat or rabbit cornea by transmission and scanning electron microscopy have shown the corneal keratocytes to be flattened, polygonal cells, and had cytoplasmic processes. The processes of neighboring keratocytes contacted each other to form an extensive and continuous network structure (Ueda et al, 1987;Nishida et al, 1988). These morphological characteristics of keratocytes closely resemble that of the GFP(1) cells observed in this study.…”