Aims: The cornea is a tough, transparent tissue providing the primary refractive element of the eye. The stroma consists of specially arranged collagen required for corneal transparency. Correct stromal hydration is important in the maintenance of transparency, a feature controlled by the endothelial cells on the posterior surface of the cornea. The aims of this research were firstly to investigate the morphology of corneal endothelial cells and their expression of the sodium bicarbonate cotransporter during avian embryonic development and secondly, to clarify the effect of disease, surgery and drugs on the posterior cornea including in particular the corneal endothelium. Methods: The corneal endothelial cell morphology and posterior stroma were examined using transmission electron microscopy to determine the ultrastructure of the cells and collagen fibril arrangement in the stroma in all results chapters. Immunohistochemistry and A-scan ultrasonography were employed to identify the presence of the Na+HCO3- cotransporter and to determine the thickness changes in embryonic chick cornea, respectively. Electron tomography was also used to determine the collagen arrangement in Descemet’s membrane. Results: The expression of the Na+HCO3- cotransporter was identified in the endothelial layer of the embryonic chicks at all stages imaged. Central corneal thickness increased in the initial stages of development before a plateau between the E12-E15 developmental period followed by a steady thickness decrease. The ultrastructure of Descemet’s membrane was determined using electron tomography of transverse and en face resin embedded sections from which a model was produced. Polygonal and elongated structures were observed with proteoglycans present at the intermodal regions of the collagenous structures. The polygonal lattice visualised in en face sections appeared to be composed of stacked globular domains which were integrated into the collagen type VIII model. Predominant changes in the Col8a2 knock-in mouse models were observed in the posterior cornea. Differences included increased proteoglycans at the Descemet’s endothelial interface, dilated rough endoplasmic reticulum and focal posterior oedema. This animal model exhibits features similar to those seen in the human form of early-onset Fuchs’ endothelial corneal dystrophy, unlike previous models reported. The final chapter is concerned with regeneration of the corneal endothelial cells. Tissue from posterior corneal surgery examined using electron microscopy revealed the presence of the host endothelial cells and fibrous tissue at the interface in non-Descemet’s membrane stripping automated endothelial keratoplasty and interface haze in Descemet’s membrane stripping automated endothelial keratoplasty. However, these features did not appear to interfere with the adhesion of the graft nor the clarity. Finally, ultrastructural analysis of Rho-kinase inhibited cells showed cells with typical morphology when compared with the untreated group Conclusions: 1) The Na+HCO3- cotransporter is present in the embryonic cornea. It is possible that the cotransporter is involved in the developmental stages and probably the thickness changes we observe during this period. 2) The ultrastructure of Descemet’s membrane appears to be composed of stacked globular domains arranged in a polygonal lattice alongside more elongated structures interspersed with proteoglycans within the internodal regions. 3) Our studies have helped validate Col4a2 mice as a promising Fuchs’ endothelial corneal dystrophy model. 4) Our investigation into posterior corneal surgery revealed ultrastructural changes that occur post-surgery at the graft interface.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:577912 |
| Date | January 2013 |
| Creators | Jones, Frances E. |
| Publisher | Cardiff University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://orca.cf.ac.uk/49911/ |
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