Effect of epithelial debridement on human cornea proteoglycans

Abstract

Corneal transparency is attributed to the regular spacing and diameter of collagen fibrils, and proteoglycans may play a role in fibrillogenesis and matrix assembly. Corneal scar tissue is opaque and this opacity is explained by decreased ultrastructural order that may be related to proteoglycan composition. Thus, the objectives of the present study were to characterize the proteoglycans synthesized by human corneal explants and to investigate the effect of mechanical epithelial debridement. Human corneas unsuitable for transplants were immersed in F-12 culture medium and maintained under tissue culture conditions. The proteoglycans synthesized in 24 h were labeled metabolically by the addition of 35 S-sulfate to the medium. These compounds were extracted by 4 M GuHCl and identified by a combination of agarose gel electrophoresis, enzymatic degradation with protease and mucopolysaccharidases, and immunoblotting. Decorin was identified as the main dermatan sulfate proteoglycan and keratan sulfate proteoglycans were also prominent components. When the glycosaminoglycan side chains were analyzed, only keratan sulfate and dermatan sulfate were detected (~50% each). Nevertheless, when these compounds were 35 Slabeled metabolically, the label in dermatan sulfate was greater than in keratan sulfate, suggesting a lower synthesis rate for keratan sulfate. 35 S-Heparan sulfate also appeared. The removal of the epithelial layer caused a decrease in heparan sulfate labeling and induced the synthesis of dermatan sulfate by the stroma. The increased deposit of dermatan sulfate proteoglycans in the stroma suggests a functional relationship between epithelium and stroma that could be related to the corneal opacity that may appear after epithelial cell debridement.

Collagens and proteoglycans of the corneal extracellular matrix

“…The quantitative and qualitative patterns of proteoglycan synthesis, and possibly of collagen fibril deposition, change when the cornea is submitted to injuries, such as epithelial debridement (36,58) and laser refractive surgery (59), suggesting that the keratocyte program for synthesis and deposition of extracellular matrix, which was followed during normal development leading to corneal transparency, is hardly recovered after injury.…”

Characterization of glycosaminoglycans in tubular epithelial cells: Calcium oxalate and oxalate ions effects

“…The results were expressed as counts per minute (cpm). Molecular weight determinations were performed by polyacrylamide gel electrophoresis (PAGE) as previously described [30,31].…”

Sulfated Glycosaminoglycans as Viral Decoy Receptors for Human Adenovirus Type 37

“…HA, on the other hand, is a non-sulfated GAG and the only GAG that is not attached to proteins [10,11]. In the eye, SA-containing mucins are common on epithelial cells and in mucosal secretions, including tear fluid [13], whereas GAG-containing molecules such as heparan sulfated proteoglycans (HSPGs) and keratan sulfated proteoglycans (KSPGs) are present on corneal (HSPGs) and stromal keratocytes (KSPGs), respectively and in the corresponding ECM [14,15,16,17].…”