Investigation of relationship between genetic variations of microRNA and its expression levels in exfoliation syndrome and exfoliative glaucoma

Exfoliation syndrome (XFS) is an extracellular matrix disease defined by the accumulation of abnormal fibrillary molecules in the eye tissues, which is known to develop more with age. Oxidative and cellular stress and inflammatory pathways play an important role in the pathogenesis of XFS. Exfoliative glaucoma (XFG), which occurs when the channels that provide drainage of aqueous humor fluid are blocked by exfoliation deposits and therefore increase in intraocular pressure, can lead to blindness if left untreated. For these reasons, early diagnosis of XFS is of great importance. microRNAs (miRNA) are significant post-transcriptional regulators that play a role in the regulation of messenger RNAs (mRNA). It has been determined that miRNA expression levels vary in various diseases. It is known that single nucleotide polymorphisms (SNPs) in the genes of miRNAs impact the processing of miRNAs and may play a role in susceptibility to various diseases. In this study, it is aimed to examine the potential of plasma expression levels of miR-196a-2 and miR-146a which are known to play a role in inflammation-related pathways, as well as the potential of mir-146a rs2910164 G/C, mir-196a-2 rs11614913 C/T SNPs as biomarkers for XFS and XFG diseases. The study group consisted of 260 patients with XFG, 260 patients with XFS and 295 control individuals in the genotyping part, and 27 patients with XFG, 25 patients with XFS and 27 controls were selected from each group for expression level determination. Blood samples were collected by Gulhane Training and Research Hospital, Department of Ophthalmology (Ankara, Turkey). Genotyping of SNPs was performed by using PCR-RFLP method, and expression levels of miRNAs in plasma were determined by using qRT-PCR method. Relative expression levels were calculated by the 2-ΔΔCt method. According to the genotype analysis, minor allele frequencies and genotype distributions for rs2910164 and rs11614913 were not different between XFG, XFS and control groups. It was found that the relative expression level of plasma hsa-miR-146a-5p was significantly higher in the XFG and XFS groups compared to the control group (XFG vs. control: P<.001, XFS vs. control: P=.001). Relative expression levels of hsa-miR-196a-5p were not different between the groups. As a result of logistic regression analysis, it was determined that the relative expression level of plasma hsa-miR-146a-5p was associated approximately 6-fold with XFG (P=.001; dominant model), and approximately 4-fold with XFS (P=.005; dominant model). As a result of ROC analysis, it was concluded that the relative expression level of hsa-miR-146a-5p in plasma could be a "good" level (AUC=0.897, P<.001, sensitivity=89%, specificity=78%) diagnostic test for XFG and a "fair" level (AUC=0.779, P=.001, sensitivity=52%, specificity=93%) diagnostic test for XFS. In this study, the relationship between mir-146a rs2910164 G/C and mir-196a-2 rs11614913 C/T SNPs, the plasma expression levels of miR-146a and miR-196a-2 and XFS and XFG was investigated for the first time. In conclusion, it was observed that the relative expression level of hsa-miR-146a-5p has the potential to be a blood-based biomarker for XFG and XFS. This thesis is a project that contributes to Biomedical Engineering, as it reveals results that have the potential to lead to the development of new diagnostic tests, biosensors and therapeutic agents that can be used in the early diagnosis, following the prognosis and treatment of XFG and XFS in the future.