The long-term objective of this proposal is to identify renal microRNAs (miRNAs) and their target genes that could potentially contribute to the progression of diabetic nephropathy (DN). MicroRNAs constitute a class of highly conserved noncoding RNAs that act as negative regulators of gene expression by either inhibiting the translation of mRNAs or destabilizing them. Because individual often regulate the expression of multiple target genes with related functions, dysregulation of a single microRNA can, in principle, microRNAs influence an entire gene network and thereby contribute to complex disease phenotypes such as DN. The main aim of the current proposed study is to evaluate the pathogenic role of microRNA-93 (miR-93) in DN. Our main hypothesis is that miR-93 contributes to the pathogenesis of DN via its modulatory involvement on VEGF signaling pathway. Our hypothesis is based on several novel observations: 1) we have recently shown miR-93 is a signature miRNA in the diabetic milieu based on comparative microRNA arrays, 2), we have shown for the first time that miR-93 plays a critical role in regulating VEGF-A expression in hyperglycemic conditions in vitro and in vivo (Long J. et al. J. Biol. Chem. 2010), and 3) targeting of miR-93 leads to a significant increase in VEGF secretion in an inducible mouse model of VEGF expression. Based upon these initial observations, we now propose an integrated in vitro and in vivo approach to test three specific aims.
Aim 1 : Assess the effect of conditional tissue-specific forced expression of miR-93 in the murine models of DN, Aim 2: Define the molecular targets through which miR-93 exerts its effect in vitro and in vivo.
Aim 3 : Characterization of glucose-responsive elements (GRE) of the mouse miR-93 promoter in podocytes. The findings of this application will provide a significant advance in three aspects: first, this proposal represents a new therapeutic approach, and potentially a new class of agents in the fight against diabetic kidney disease. Second, our research will shed light not only on the role of miR-93 in hyperglycemic conditions, but also on the pathobiology of VEGF in diabetic nephropathy. And third, we will generate a genetic model to confirm that miR-93 is directly involved in the pathogenesis of DN. This genetic model will provide additional information on the role of miR- 93, and its potential targets in DN.
Diabetic nephropathy represents the primary cause of ESRD in the US, underscoring the need for innovative therapies for preventing its progression. New evidence suggests that microRNAs in the kidney are key pathogenic factors in diabetic nephropathy. We propose that targeting of miR-93, a novel microRNA in the kidney, holds promise as a novel therapeutic strategy to ameliorate progression of diabetic nephropathy.
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