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Proteoglycan distribution during healing of corneal stromal wounds in chick
1University of Pittsburgh School of Medicine, Pittsburgh, PA, USA.
Insights
Corneal wound healing in young chicks shows altered proteoglycan synthesis. Scar tissue has increased adhesive molecules like laminin and perlecan, but reduced lumican (a keratan sulfate proteoglycan).
Area of Science:
- Ophthalmology
- Developmental Biology
- Tissue Engineering
Background:
- Corneal stromal healing is crucial for maintaining vision.
- Proteoglycans play vital roles in corneal structure and wound repair.
- Understanding molecular changes during healing in developing corneas is important.
Purpose of the Study:
- To analyze proteoglycan distribution during corneal stromal healing in young chicks.
- To investigate changes in specific proteoglycans (lumican, keratocan, keratan sulfate) and matrix molecules (perlecan, laminin) post-wounding.
Main Methods:
- Histological and immunohistochemical analyses of chick corneas post-wounding.
- Periodic acid-Schiff's reaction (PAS) for glycoprotein content.
- Indirect immunofluorescence for lumican, keratocan, keratan sulfate, perlecan, and laminin.
Main Results:
- Wounds were covered by epithelium within 2 days, with scar tissue partially restoring stromal thickness.
- Scar tissue was hypercellular and PAS positive, indicating increased glycoprotein content.
- Increased synthesis and deposition of perlecan and laminin were observed in healing stroma.
- Keratocan and keratan sulfate showed no difference, while lumican levels were markedly decreased in scar tissue.
Conclusions:
- Corneal wound healing in young chicks involves altered proteoglycan and glycoprotein synthesis.
- Elevated synthesis of adhesive molecules (laminin, perlecan) occurs during healing.
- Reduced synthesis of lumican, a keratan sulfate proteoglycan, is a key feature of corneal scar tissue in developing corneas.
Abstract:
Proteoglycan distribution during corneal stromal healing in growing corneas of young chicks were histologically and immunohistochemically analysed. Single linear incisions to produce partial-thickness wounds were made in the corneas of 5 day old chicks. The corneas were harvested at different times after wounding and processed for either histochemical analyses using periodic acid-Schiff's reaction (PAS) or for indirect immunofluorescence analyses of lumican, keratocan, keratan sulfate, perlecan and laminin. Linear corneal stromal incisions were completely covered by migrated stratified epithelium by day 2 post wounding and resulted in a gaping wound with a thinner stroma. New stromal scar tissue formed between the epithelium and the original stroma that resulted in partial restoration of stromal thickness. During the first two to three weeks of healing, the stromal tissue filling the depression formed from the gaping wound, was hypercellular and PAS positive, indicating significantly higher levels of glycoprotein content but no new Bowman's membrane was formed. By four weeks, the scar tissue occupied a 2-3 mm wide region. Immunofluorescence analyses indicated that other major differences in the healing and normally growing stroma were the increased synthesis and deposition of perlecan and laminin. No differences were evident in the immunofluorescence for keratocan or keratan sulfate in the scar tissue, but the scar tissue did contain markedly decreased levels of lumican. Thus, the regulation of proteoglycan and glycoprotein synthesis is altered in the keratocytes that are recruited to the wounded regions in the growing corneal stroma of post-hatched young chicks. While synthesis and deposition of adhesive molecules including laminin and perlecan are elevated, the synthesis of one of the keratan sulfate proteoglycans, lumican, is reduced in the scar tissue as compared to the normally growing stroma.