The Role of Epigenetics and Type 2 Epithelial-Mesenchymal Transitions in Trachoma.

Trachoma is the leading infectious cause of blindness worldwide and is initiated by repeated infection of the conjunctiva with Chlamydia trachomatis (Ct). In some individuals this causes chronic inflammation and fibrosis that progresses in the absence of Ct. The work presented in this thesis sought to determine the role and contribution of miRNA and epithelial-mesenchymal transition (EMT) in various stages of trachomatous disease. Epithelial cells did not differentially express miRNA at 48 hours post infection with virulent plasmid-competent and avirulent plasmid-free ocular strains of Ct. Expression of inflammatory cytokines and growth factors were increased in response to virulent Ct infection but the induction of EMT was not detected in response to either strain. In a set of 161 samples from children living in a trachoma hyper-endemic region in Guinea-Bissau, miR-155 was upregulated in children with active trachoma and current Ct infection and miR-184 was downregulated in children with active trachoma with and without Ct infection. In a set of 194 samples from adults in The Gambia, miR-1285 and miR-147b were upregulated in inflammatory trachomatous scarring. Differential expression of these miR indicates the regulation of inflammation, wound healing and cell proliferation pathways. Immunohistochemistry was used to study conjunctival biopsies from Tanzanian adults with trachomatous trichiasis and found increased epithelial expression of the pro-inflammatory mediator and antimicrobial peptide S100A7 and connective tissue growth factor. Pro-inflammatory cytokine IL-1β expression was increased in the subepithelium relative to controls. Trichiasis cases had increased disruption of collagen deposition patterns and increased sub-clinical inflammatory cell infiltrates, but no differences in epithelial atrophy and myofibroblasts were detected relative to controls. There was no evidence for the occurrence of EMT in biopsy tissue from trachomatous trichiasis cases. These data suggest that EMT does not have a major role in conjunctival fibrosis and highlight the importance of inflammation in trachomatous pathology.