In vitro studies have established that airway smooth muscle (ASM) cells exhibit phenotypic plasticity in response to inflammatory events mediated by transcriptional and post-transcriptional mechanisms that have not been fully elucidated. microRNA (miRNA)-mediated gene silencing has emerged as an regulator of gene expression and studies of miRNA function in ASM hold promise for the development of novel miRNA-based tools for prognosis and therapy. The long-term goal of our studies is to identify the miRNA-mediated gene- silencing mechanisms determining ASM cell phenotype in asthma. Our laboratory was the first to characterize miRNA expression in ASM following a pro-inflammatory stimulus and identified miR-25 as a target of the inflammatory response that regulates plasticity of ASM cells. This proposal will test the hypothesis that expression of miR-25 attenuates allergic asthma pathogenesis by altering ASM phenotype.
In Specific Aim 1, we will determine whether miR-25 expression in a mouse model of allergic inflammation attenuates hyperreactivity, remodeling and alters ASM contractile force using a unique transgenic mouse model of smooth muscle-targeted miR-25 expression. These mice will be used to assess the effects of miR-25 on AHR, remodeling and ASM contractility following acute and chronic models of ovalbumin-sensitization and challenge.
In Specific Aim 2, we will study the effect of smooth muscle-targeted miR-25 expression on increased ASM mass in vivo following acute and chronic ovalbumin-sensitization and challenge by assessing proliferative markers and mitogenic signaling pathways to address the molecular mechanisms underlying this miR-25 function.
In Specific Aim 3, we will determine whether miR-25 affects the phenotype of asthmatic ASM cells using gain and loss of miR-25 function studies, as well as effects on identified targets of miR-25 mediated gene-silencing. This unique experimental approach, coupled with correlations in human diseased cells, will provide mechanistic data describing miR-25 function in the lung and be an essential step towards developing novel therapeutic strategies targeting miRNA in asthma.
Current asthma therapies alleviate airway obstruction and inflammation without adequately addressing airway hyperresponsiveness and remodeling mediated by airway smooth muscle. This proposal will explore the role of gene-silencing by microRNA-25 as a mechanism regulating phenotype of normal and asthmatic airway smooth muscle cells and propose experiments targeting microRNA-25 expression in a mouse model of airway disease as a potential therapeutic.