Comprehensive analysis of Glomerular Endothelial Cell MicroRNA expression to identify diabetic kidney disease biomarkers

In accordance with worldwide trends for obesity, physical inactivity and an ageing population, the prevalence of diabetes mellitus is predicted to continue rising. Of those affected, it is estimated that 40% will develop diabetic kidney disease (DKD) (Jha et al. 2013; Alicic et al. 2017). DKD is the leading cause of end-stage renal disease and is a major contributor toward increased mortality in diabetes patients (Jha et al. 2013). Detection of urinary microalbuminuria forms the basis of current DKD progression monitoring, but prognosis is complicated since not all microalbuminuric patients progress to overt nephropathy. Numerous biomarkers have been assessed for utility in DKD, but none have demonstrated the specificity and sensitivity required to predict individual DKD patient outcomes. MicroRNAs (miRs) are ubiquitously expressed short noncoding RNAs that regulate the expression of most protein coding genes in the human genome. Urinary miRs represent a promising novel source of non-invasive biomarkers, that are rapidly and precisely detected by RT-qPCR (Beltrami et al. 2015). Recently, Beltrami et al. (2018) identified elevated detection of urinary miR-126, miR-155 and miR-29b in DKD, and demonstrated increased miR-126 in conditioned medium from cultured glomerular endothelial cells (GEnCs) in response to conditions mimicking the in vivo DKD environment. The work described in this thesis expanded these observations by conducting TaqMan Low Density Array (TLDA) expression profiling of 377 GEnC miRs from the same in vitro DKD model. A number of differentially expressed cellular and extracellular miRs were identified in response to hyperglycaemia and tumour necrosis factor-alpha (TNF-α) treatments. In silico analysis revealed the enrichment of biological pathways involved in TGF-β signaling, regulation of collagen expression, and cytoskeletal modulation. Further work will be required to determine the relevance of these alteration in miR expression in vivo