Pterygium is an ocular surface disorder characterised by centripetal invasion of the cornea by altered limbal cells, accompanied by fibrosis and neovascularisation. One of the enigmatic features of pterygium is its wing-like shape and the mechanism(s) supporting its centripetal growth remain to be elucidated. As the growth pattern of pterygia mirrors the radial arrangement of corneal nerves, we hypothesised that neuropeptides may facilitate its directional growth. In this thesis, we investigated the roles that the sensory neuropeptide substance P (SP) may play in the pathogenesis of pterygia given its known functions in corneal cell migration, proliferation, wound healing and neurogenic inflammation. Using a modified Boyden chamber method, SP was shown to act as a chemoattractant to pterygium fibroblasts and vascular endothelial cells, and this activity was diminish by blockade of its receptor (NK1). 3H-thymidine incorporation assays confirmed that our cell migration results were unrelated to SP-stimulated proliferation. A bead-based multiplex cytokine array detected secretion of pro-inflammatory cytokines (IL-6, IL-8 and CCL2) from SP stimulated pterygium and limbal epithelial cells. Using real-time RT-PCR and immunoblotting, we show that UVB stimulated transcription of the TAC1 gene followed by secretion of SP in ocular surface epithelial cell cultures. Finally, SP and NK1receptor immunoreactivity was identified in pterygium tissue, where overall, NK1receptors were up-regulated in pterygia. Furthermore, we identified a population of NK1 receptor positive mononuclear cells in pterygia that did not express lineage markers for T or B-Iymphocytes, macrophages or mast cells, but may represent immature haemopoietic cells that may have migrated in from the blood since these cells were also present in autologous conjunctival tissue. In summary, SP may contribute to the shape of pterygia by facilitating migration of fibroblasts and vascular endothelial cells into the normally avascular cornea. Additionally, UVB stimulates SP production in epithelial cells and the presence of SP contributes to inflammation in pterygia by inducing pro-inflammatory cytokine release. Finally, we identified a population of relatively immature, NK1 receptor positive cells in pterygia that may have been attracted by the presence of SP. Collectively, these results imply that SP may contribute to the pathogenesis of pterygia.

Made available in DSpace on 2016-08-10T10:39:27Z (GMT). No. of bitstreams: 1 Francisco Weliton Rodrigues.pdf: 26774271 bytes, checksum: c81af1f8ff9812886fda32632000dc44 (MD5) Previous issue date: 2008-09-29 / Pterygium is a disease of unknown origin and pathogenesis that can be vision threatening. Several researchers believe that pterygium is UV-related and that abnormal expression of p53 protein and infection with human papillomavirus (HPV) are risk factors for pterygium, but their experiments have been inconclusive. We investigated its relation with p53 protein expression, p53 gene codon 72 polymorphism and infection with HPV DNA. Pterygial samples were obtained from 36 patients; 21 normal conjunctival samples were used as controls. Expression of p53 protein was studied by Immunohistochemistry, using the antibody DO-7. Analysis for the p53 genotype was made with PCR, using specific primers for the arginine and proline alleles, and an analysis for HPV was made of the pterygium patients and control group. Fourteen of the 36 pterygia specimens were positive for abnormal p53 expression. Thirty one of the patients were heterozygotic and three were homozygotic for the proline allele; two were homozygotic for the arginine allele; in the control group 12 of 21 were heterozygotic and seven of these 21 were homozygotic for the proline allele; two were homozygotic for the arginine allele. Twenty-one of the pterygia patients were positive for HPV; HPV type 1 was found in nine of these, type 2 in seven and both types in five. Only two of the 21 controls had HPV; both had type 16. We suggest that abnormal expression of p53, p53 codon 72 polymorphisms and HPV DNA are required cofactors for the development of pterygium. / O pterígio é uma doença de origem e patogênese desconhecida que pode comprometer a visão. Vários pesquisadores acreditam que o pterígio está relacionado à luz UV e a expressão anormal da proteína p53, além da presença do papilomavírus humano (HPV), como fatores de risco para o seu desenvolvimento, mas os resultados são inconclusivos. Investigamos a expressão da proteína p53, o polimorfismo do codon 72 do gene TP53 e a presença do HPV. Amostras de pterígio foram obtidas de 36 pacientes e 21 escleras normais formaram o grupo controle. A expressão de p53 foi analisada por imunohistoquímica usando anticorpo DO-7. Análise do genótipo de p53 foi realizada por PCR com primers específicos para os alelos arginina e prolina e a presença do HPV foi analisada nos dois grupos. Quatorze amostras de pterígio (39%) foram positivas para expressão anormal de p53. O polimorfismo foi observado em 31 (86%) amostras heterozigotas, 03 (8%) homozigotas para prolina e 02 (6%) homozigotas para arginina, enquanto que no grupo controle foi observado 12 (57%) amostras heterozigotas, 07 (33%) homozigotas para prolina e 02 (10%) homozigotas para arginina. 21 pterígios (59%) foram positivos para HPV e o tipo 01 foi encontrado em 43% (9/21), tipo 02 em 34% (7/21) e os dois tipos simultaneamente em 23% (5/21) amostras do gruppo pterígio. O grupo controle mostrou 9.5% (2/21) amostras positivas para HPV e o tipo 16 nas duas amostras. Nossos dados sugerem que a expressão anormal de p53, o polimorfismo do codon 72 e a presença do HPV podem estar relacionados com o desenvolvimento do pterígio.