Changes in the biosynthesis of corneal glycosaminoglycans during wound healing

An ultrastructural and histochemical study of long-term wound healing after radial keratotomy

Using correlative microscopy and plant lectins conjugated to fluorescent dyes, we studied two human corneal specimens obtained 66 and 70 months after radial keratotomy. In one case a second radial keratotomy had been performed 11 months before we obtained the corneal specimen, which allowed us to compare wounds 11 and 66 months old in the same specimen. The 11-month-old incisions demonstrated morphologic features consistent with incomplete wound healing, whereas the incisions examined 66 and 70 months postoperatively demonstrated complete wound healing. A different lectin binding pattern of wheat germ agglutinin and concanavalin-A was observed in the 11-month-old wounds, compared with the 66-month-old wounds. Published and unpublished morphologic studies of 17 human keratotomy specimens have demonstrated incomplete wound healing up to 47 months postoperatively. The present study documents complete corneal wound healing 66 months after radial keratotomy.

Oculotoxicities of systemically administered drugs

There have been many drugs reported to cause oculotoxic responses after their systemic administration. The severity of these toxicities range from minor ocular inconvenience to permanent loss of vision. This paper reviews the current literature and attempts to suggest some probable factors involved in the development of oculotoxicities by systemic drugs. Various drug entry and exit pathways in the eye are presented and the role of some intraocular structures in the toxicity development is examined. The issues of melanin binding, genetic heterogeneity, photosensitivity and environmental pollution are discussed.

Proteoglycan changes during restoration of transparency in corneal scars

Corneal scars generated in rabbits by penetrating wounds are initially opaque but become transparent within a year. Previous studies have shown that the corneal stroma consists of proteoglycans and collagen fibrils spaced at regular intervals and that the interfibrillar spaces, the presumed location of proteoglycans, are abnormally large in opaque scars. In the present study, the size and glycosaminoglycan composition of the corneal stromal proteoglycans were determined in corneal scars during the restoration of transparency. The results showed that initially opaque scars which contained the large interfibrillar spaces also contained unusually large chondroitin sulfate proteoglycans with glycosaminoglycan side chains of normal size. These opaque scars also lacked the keratan sulfate proteoglycan but did contain hyaluronic acid. In the 1-year-old scars there was a restoration of normal interfibrillar spacing, and a return to corneal stromal proteoglycans of normal size and composition. These correlations suggest that the corneal stromal proteoglycans may play a fundamental role in regulating corneal collagen fibril spacing.

Alkali burns of the rabbit cornea. II. A histochemical study of glycosaminoglycans

In alkali burned rabbit cornea the stainability of glycosaminoglycans in cold microtome setions was investigated. Staining by Alcian blue in 3% acetic acid, Alcian blue in various MgCl2 concentration and toluidine blue (pH 4.5) was employed. From the 1st to the 4th experimental day the intensity of reactions was decreased. This is most probably due to an increased hydration of the corneal stroma. On the 7th day hydration was markedly suppressed and reached nearly the normal level. In this time interval a decreased stainability of glycosaminoglycans was seen accompanied by a complete loss of staining in the marginal zone. On the 14th day the stainability in the traumatized area began to restore and in the marginal zone appeared. On the 32nd day the staining intensity of both areas was normalised, however when lower concentrations of MgCl2 were used; in the presence of higher concentrations of MgCl2 the decreased staining intensity persisted and points to a lower sulfatation of glycosaminoglycans. This was particularly remarkable in the area bordering the injured zone. This decrease runs parallel to the increased activities of acid glycosidases (especially of acid beta-galactosidase) which were reported previously.

The hydration of proteoglycans of bovine cornea

The water sorptive and retentive capacities of three corneal proteoglycans with different keratan sulfate/chondroitin-4-sulfate compositions were investigated. The calcium salt of a predominantly keratan sulfate containing proteoglycan had hydration properties similar to that of calcium keratan sulfate. The proteoglycan containing predominantly calcium chondroitin-4-sulfate side chains sorbed water to a greater extent than pure calcium chondroitin-4-sulfate but its retentive power was somewhat less. The proteoglycan containing about twice as much keratan sulfate as chondroitin-4-sulfate, on a dissaccharidic molar basis and had hydration properties which were closer to the behavior of chondroitin-4-sulfate than keratan sulfate. The results are discussed in terms of structure and polymer interaction in the proteoglycan matrices.