Fibronectin antibody labels corneal stromal collagen fibrils in situ along their length and circumference and demonstrates distinct staining along the cell and stromal interfaces of Descemet's membrane.

PURPOSE/AIM OF THE STUDY: An immunoperoxidase cytochemical study of fibronectin localization in the rat corneal stroma and Descemet's membrane was conducted following organ culture to determine whether stromal swelling allowed better primary antibody penetration into the normally tough fibrous corneal stroma.

MATERIALS AND METHODS

Following 24 h organ culture, corneas were fixed in 4% paraformaldehyde, washed and stained overnight at 4 °C in anti-fibronectin followed by washing and incubation in an appropriate secondary antibody and exposure to protein A-HRP. Cytochemical processing was carried out in a DAB-containing medium followed by dehydration and Epon embedding.

RESULTS

Observations of the stromal lamellae revealed the presence of a novel punctate staining pattern along the length of the collagen fibrils that extended around the fibril's circumference. Measurements on the peroxidase reaction product spacing indicated a periodicity of approximately 20.69 ± 3.57 nm along the fibril's length. Light microscopic immunocytochemistry revealed the presence of fibronectin staining occurred within the endothelial cell layer but only along the DM/stromal interface. Electron microscopic observations however, revealed that fibronectin staining occurred in distinct linear patterns along the length of both the endothelial and stromal DM interfaces.

DISCUSSION

Results indicate that organ culture mediated swelling helps facilitate the penetration of primary antibody into the corneal stroma. Observations suggest a novel association exists between fibronectin and stromal collagen fibrils that helps to mediate the arrangement and organization of the stromal extracellular matrix. Results also definitively indicate that fibronectin is deposited along both DM interfaces suggesting that it plays a role in the adhesion of both the endothelial cell layer and stroma to Descemet's membrane to help maintain the tissue architecture within this region of the cornea.