Abstract:
Keratoconus presents as a distinctive conical protuberance of the cornea which manifests from stromal thinning. This can cause severe visual decline in serious cases which may require a corneal transplant. Curative strategies targeting the causal pathological mechanisms are not currently available. This is resultant of the undefined pathobiology underlying disease development, in spite of extensive investigative efforts. There is evidence of wound healing and reactive oxygen species (ROS)-associated defects in keratoconus. Their interaction and the normalising effect of ROS-neutralisation on both these functions have been shown in other tissue types. Thus, this thesis explored repair and ROS-linked processes, their connection and the effect of antioxidant treatment in keratoconus. Stromal cells from keratoconic and unaffected corneas with and without an ex vivo incisional lesion, and oxidant and antioxidant exposure, were analysed using quantitative Polymerase Chain Reaction (qPCR) and immunoarrays. These, respectively, measured the gene and protein expression of cytokines and ECM elements typically produced during healing, and corneal stromal ROS-synthesisers and deactivators. In keratoconic cells, repair may be overactive; in fact, it may be comparable to that in normal cells after wounding. However, following a secondary injury, the reparative response in keratoconic cells may be deficient. Keratoconic cells may produce more ROS and their ability to counteract them may be abnormal. These differences may be distinct from those in normal cells exposed to oxidant. In response to a secondary oxidative challenge, ROS neutralisation by keratoconic cells may be excessive. The relationship between wound healing and ROS-associated pathways in keratoconic cells was examined by inflicting a secondary insult to one process and assessing its effect on the other. The capability of injured keratoconic cells to counterbalance ROS may be reduced. Conversely, repair in keratoconic cells may be increased after an oxidative challenge. Antioxidant treatment may encourage the synthesis of a normal ECM and modulate ROS levels in keratoconic cells. These molecular changes could underpin a structural improvement in corneal strength. These results demonstrate that wound healing and ROS-associated pathways may be abnormal in keratoconus. Moreover, antioxidant treatment can normalise these pathological irregularities. Ultimately, these novel findings may improve our comprehension of pathobiology and, consequently, advance the clinical management of keratoconus in the future.