Corneal development and the role of keratan sulphate

Liles, Melody. 2006. Corneal development and the role of keratan sulphate. PhD Thesis, Cardiff University.

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Abstract

In the week before hatch, the embryonic chick cornea thins and becomes transparent (Coulombre and Coulombre, 1958 Hay and Revel, 1969 Connon etai, 2003). Proteoglycans (PGs), have long been envisaged as potential modulators of corneal structure during the latter stages of development previous quantification of corneal glycosaminoglycans has indicated no change in the amount, molecular size, or degree of sulphation between developmental days 10 and 14 (Hart, 1976). After this time, keratan sulphate (KS) becomes more highly sulphated. This study aims to investigate changes in highly and lesser sulphated KS levels with collagen order and spacing in the developing chick cornea during the week before hatch around day 21 of development. Microscopy studies were used to follow the emergence of highly and lesser/undersulphated KS at both the light and electron level. Immunostaining of corneas from select developmental timepoints showed accumulation in an anterior-posterior fashion, becoming homogeneous shortly before hatch. Immunolocalisation of KSPGs show association with collagen fibrils at the cell surface, with a corresponding increase in labelling as fibrils become more aligned. Collagen fibrils show uniform spacing in bundles as fibrils are extruded, with highly sulphated KS already associated with collagen at the cell surface. X-ray diffraction was used to deduce mean centre to centre collagen fibril spacing and local order at specific timepoints in a large sample group of developing chick corneas. These same corneas were then analysed for highly and lesser sulphated KS content, collagen content and wet weight. A separate cohort of corneas were analysed for collagen fibril spacing and keratanase sensitive KS content. KS was found to increase as collagen fibrils condense and collagen deposition increases, significantly so when highly sulphated. In summary, as the secondary chick cornea develops and becomes transparent, the compaction of stromal collagen fibrils is accompanied by an increase in tissue levels of sulphated KS. Remodelling of the fibrillar arrangement may be related to a switch to highly sulphated KS production, with a role for KS in the structural "fine tuning" of the fibrillar array.

Item Type:	Thesis (PhD)
Status:	Unpublished
Schools:	Optometry and Vision Sciences
Subjects:	Q Science > Q Science (General)
ISBN:	9781303207662
Date of First Compliant Deposit:	30 March 2016
Last Modified:	22 Aug 2024 10:26
URI:	https://orca.cardiff.ac.uk/id/eprint/56129

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