AMD Mitochondria Modulate Expression of microRNA 135b-5p and 148a-3p in RPE Cybrids: Implications for Age-related Macular Degeneration

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Project Summary/Abstract Age-related Macular Degeneration (AMD) represents a major cause of blindness in the developed world, and significant research has been devoted to exploring the causes and potential treatments. While the mitochondria have been found to be of critical importance to the development of AMD, less is known about the exact pathways through which mitochondria influence nuclear gene expression and disease progression. We have developed a novel transmitochondrial cybrid model that allows us to generate retinal pigment epithelial cell lines with identical nuclei, but with mitochondria from different AMD and age-matched normal subjects. Using these cybrids, our laboratory has discovered that introduction of AMD mitochondria causes cellular apoptosis, oxidative stress and decreased cell viability. Presently, we are exploring how the mitochondria of AMD patients could cause these dramatic changes in cybrid cell lines, and how this influence could be modulated to improve cellular health. One of the potential pathways that we have investigated is the regulation of microRNA. Our preliminary cybrid data show that introduction of AMD mitochondria causes altered expression of seven microRNA with functions relevant to AMD pathology. Subsequent work has focused on the targeted downregulation of two overexpressed microRNA present in the AMD cybrids (miRNA 135b-5p and miRNA 148a-3p). Downregulation of miRNA 135b- 5p leads to decreased expression of genes associated with apoptosis and angiogenesis, while downregulation of miRNA 148a-3p results in increased expression levels of genes associated with mitochondrial biogenesis and decreased reactive oxygen species production. These findings demonstrate the effectiveness of microRNA modulation as a method for improvement of cellular health and potential treatment. Building upon these preliminary data, our central hypotheses for this grant are that cells with AMD mitochondria (a) exhibit altered microRNA expression and that (b) modulation of these dysregulated microRNA levels through targeted inhibition or overexpression will influence gene expression, cellular health and in vitro models of angiogenesis. Further understanding of the role of microRNA in the AMD model has a significant potential impact for a variety of other diseases with mitochondrial dysfunction, including Alzheimer’s and Parkinson’s diseases.