Structure of Collagen fibril and proteoglycans at different depth of corneal stroma of CXL treated rats

Abstract

AbstractPurpose In the present study we assess the effects of collagen cross‐linking on ultrastructure organization of collagen fibrils (CF) and proteoglycans (PGs) in a rat model.Methods The corneas were treated with a standard cross linking (CXL) method with isotonic riboflavin. Scelral‐corneal rings were removed one week after the treatment. All samples were fixed in 2.5% glutaraldehyde containing cuprolinic blue in sodium acetate buffer and processed for electron microscopy.Results The CXL rat corneal stroma thickness increased compared to the normal rat corneal stromal thickness. The collagen fibril diameter (29.28±3.42nm) in the anterior stroma of CXL rats was larger compared to the CF diameter (27.76±3.77nm) of the anterior stroma of control rats. Within the CXL rat corneal stroma, the CF diameter (29.28±3.42nm) and the interfibrillar spacing (43.01±3.32nm) in the anterior stroma were larger compared to the diameter (26.07±2.8nm) and interfibrillar spacing (41.27±3.52nm) in the posterior stroma. The PGs mean area was larger in the posterior stroma (260.1±282.395nm2) than the PGs mean area in the anterior stroma (209.98±177.0nm2) within the corneal stroma of the CXL rat.Conclusion The present study demonstrates that CXL leads to an increase in the CF diameter and interfibrilar spacing and reduces the PGs area in the anterior stroma of the CXL rats. The changes in the collagen fibril diameter could be due to an increase in the spacing between the microfibrils within the collagen fibrils. The increase in interfibrillar spacing could be due to an increase in hydration in the corneal stroma.