Control of the Corneal Epithelial Stem/Progenitor Cell Niche

The corneal epithelium is vital for healthy vision and its malfunction owing to injury or disease leads to irreversible blindness. The epithelium is maintained by a population of slow-cycling adult stem/progenitor cells located at the edge of the cornea. These exist basally and within radial infoldings of the epithelial basement membrane. We hypothesise that cellular cross-talk and signals from the matrix help maintain the stem/progenitor cell niche. This is based on our discovery that specific sulphation motifs of chondroitin sulphate are putative biomarkers for articular cartilage progenitor cells (J Histochem Cytochem 2008;56:125-131). Pilot investigations of rabbit cornea support this concept and indicate that chondroitin sulphate is preferentially located next to the epithelial basal cells at the corneal periphery.
This studentship will comprise an in-depth investigation of the stem/progenitor cell niche at the edge of the cornea and in corneal cells in culture. Immunohistochemistry will be conducted using a battery of monoclonal antibodies developed in the Caterson laboratory against variously sulphated chondroitin sulphate epitopes. This will allow identification of matrix markers of the corneal stem/progenitor cell niche. Co-localisation with putative identifiers of stem/progenitor cells (CD-90, CD-105, p63 and Beta-catenin) will clarify specific co-associations between cells and their immediate environment in vivo and in vitro. Higher resolution imaging by immunoelectron microscopy with nanogold particles will distinguish cell surface-associated, or matrix-associated, localisation of the chondroitin sulphate biomarkers. Pilot studies of rabbit cornea have also provided tantalising evidence of what appear to be direct connections between fibroblasts and epithelial cells at the cornea's edge (Fig 2). This will be investigated at high magnification and in three-dimensions using the emerging technique of serial block face scanning electron microscopy to ascertainthe nature and extent of these proposed intercellular connections in, and away from, the niche. Finally, to identify the role of the stem/progenitor cell niche in corneal epithelial dysfunction, changes in the presence, distribution and sulphation specificity of chondroitin sulphate -- and of the pattern of cell-cell connections across the epithelial basement membrane -- will be investigated in tissue obtained postoperatively from eyes with corneal epithelial stem cell deficiencies, caused either by disease or chemical injury.
It is also intended that in the second year of study, the student will have a summer placement in the lab of the research collaborators in Kyoto, Japan.