Cell-cell adhesion in the prelaminar region of the optic nerve head: a possible target for ionic stress.
OBJECTIVE
This paper aims to study the anterior surface of the optic nerve in relation to its ability to support a source of stress acting from the vitreous cavity. The intercellular junctions of the lining astrocytes mediated by cellular adhesion molecules (CAMs) may be the main targets for ionic stress.


METHODS
The optic nerve of the domestic pig was prepared for light, confocal laser and transmission electron microscopy. Immunostaining was performed for antibodies against glial fibrillary acidic protein, neural cadherin (N-cadherin) and neural CAM (N-CAM).


RESULTS
Only 1 type of intercellular junction was found among the bordering astrocytes, which was characterized as a zonula adherens. Unions between lining cells showed a positive immunogold effect and immunofluorescence against N-cadherin in the zonula adherens and membrane apposition. N-CAM was also present in areas of nonjunctional cellular adhesion.


CONCLUSIONS
The stability of intercellular junctions of the nerve-vitreous boundary is sensitive to altered concentrations of Ca(2+). Since aqueous humor has half the Ca(2+) concentration of plasma, any contact of aqueous humor with the optic nerve head can interfere with the ionic concentration of calcium in the extracellular spaces. This mechanism may contribute to age-related changes and some types of glaucoma.
Carreras
Francisco Javier
FJ
Department of Surgery (Ophthalmology), Faculty of Medicine, University of Granada, ES-18071 Granada, Spain. fjcarreras@telefonica.net
Porcel
David
D
Alaminos
Miguel
M
Garzón
Ingrid
I
D022005:Adherens Junctions / Q000378:metabolism / Q000648:ultrastructure*; D000818:Animals; D001253:Astrocytes / Q000378:metabolism*; D001485:Basement Membrane / Q000378:metabolism / Q000648:ultrastructure; D015820:Cadherins / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D002448:Cell Adhesion / Q000502:physiology; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism; D007124:Immunoenzyme Techniques; D007477:Ions / Q000378:metabolism; D018613:Microscopy, Confocal; D046529:Microscopy, Electron, Transmission; D019006:Neural Cell Adhesion Molecules / Q000378:metabolism; D009898:Optic Disk / Q000378:metabolism / Q000648:ultrastructure*; D013552:Swine; D014822:Vitreous Body / Q000378:metabolism / Q000648:ultrastructure
D015820:Cadherins; D005904:Glial Fibrillary Acidic Protein; D007477:Ions; D019006:Neural Cell Adhesion Molecules; D002118:Calcium