Effets du stress oxydatif induit par les rayons UVA et endogène sur la cornée humaine : étude des délétions de l'ADN mitochondrial, des modifications dans la matrice extracellulaire cornéenne et de la dystrophie cornéenne endothéliale de Fuchs
|Authors:||Gendron, Sébastien P.|
|Abstract:||Oxidative stress can arise from exogenous sources like UVA or endogenous source like the respiratory chain (OXPHOS). Oxidation of cellular components is associated with degenerative disease, aging phenotypes and loss of tissue functions. UVA is the most efficient components of UV light to induce oxidation, like it have been shown by the formation of oxidative damage on DNA and the appearance of resulting mitochondrial deletions. The mitochondrial deletion of 4977 bp (mtDNACD4977), the most common, and the 3895 bp (mtDNA3895) are both connected to skin photoaging and exposition to oxidative stress. Skin photoaging is well documented and is portrayed by a degradation of the extracellular matrix, a loss of elasticity and formation of wrinkles. However, few studies have been done on the human cornea even if this structure is directly exposed to UV light like the skin. Thus, we have tried to understand the effect of exogenous and endogenous oxidative stress on this eye structure. Analysis of mtDNACD4977 and mtDNA3895 in the human eye has shown that these deletions are localized in the corneal stroma and accumulate with age. The corneal stroma is the cellular layer conferring transparency and rigidity to the human cornea. Our results have suggested that UVA is implicated in the photoaging of the cornea. Thus, we checked for changes linked to UVA exposure in the corneal stroma since UVA are known to cause alteration to the extracellular matrix (ECM). Thereby, we created a photoaging model by exposing keratocytes to chronic UVA doses and then making them secrete an ECM. Our results have shown that chronic UVA exposure causes changes similar to photoaging phenotypes. We noted changes in the transcriptomic and proteomic expression of collagen and proteoglycans. Alteration to collagens composition by aging leads to corneal rigidity, cloudening and a loss of refractive power of the cornea, which can result in a loss of vision. On the other hand, we also investigated the implication of oxidative stress in the Fuch’s Endothelial Corneal Dystrophy, a degenerative disease of the corneal endothelium, which leads to a vision loss and is the leading cause of corneal transplantation. The etiology of the disease is not well known, but oxidative stress is suspected of playing an important role in the pathogenesis. Our results have shown new evidences of oxidative stress in the pathology by displaying an increase in mitochondrial DNA and a telomeric shortening in cells from corneal explants. Our results have also shown that using cell culture on FECD cells can allow the selection of functional cells that can compare to healthy cells terms of mitochondrial amount and integrity, sensitivity to oxidation and telomere length. Our results support the fact that functional FECD cells could be used to create autologous cornea by tissue engineering to solve the lack of corneal graft. Thus, our findings bring new evidences to the implication of oxidative stress in corneal photoaging and in the etiology of FECD.|
|Document Type:||Thèse de doctorat|
|Open Access Date:||24 April 2018|
|Collection:||Thèses et mémoires|
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