Identifying Molecular Phenotype of Normal and Asthmatic Bronchial Smooth Muscle

Boston University Medical Campus, Boston MA

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Abstract

Asthma is a common disease with several effective treatments, including inhaled steroids and ¿-agonists. Despite this, a small subpopulation of patients has a severe unrelenting course associated with airway remodeling. A central feature of airway remodeling is alteration in bronchial smooth muscle (BSM) phenotype, which is classically characterized by expansion of cell number and size, and increased hyper- reactivity to specific and non-specific agonists. While fundamental to asthma pathogenesis and its clinical manifestations, a lack of knowledge regarding the basis for a deranged BSM phenotype is an ongoing, unresolved, issue in the field. This is manifested by the paucity of information regarding the molecular signals underlying bronchial hyper-reactivity and by the lack of treatments directed specifically at reversing the asthmatic BSM phenotype. One major contributing factor to this state-of-affairs is the lack of tools/methodologies that support the high fidelity isolation of pure BSM cells from asthmatic lungs for analysis. To overcome this, we developed a unique transgenic mouse in which BSM singly express a green fluorescent protein (hrGFP) whereas vascular smooth muscle express green (hrGFP) and red fluorescent proteins (dsRed); thereby providing for the first time a reliable methodology for separating each of these two smooth muscle cell populations from one another, and from other lung cells using flow cytometry. Using this unique mouse, our plan is to perform comprehensive mRNA and miRNA profiling of BSM RNA to test the following broad based hypothesis: 1) BSM express a distinct genetic signature and 2) alterations in this signature mediate asthmatic BSM phenotypes. Our plan is to use the profiling data to generate lists of complete and differentially expressed mRNAs and miRNAs in normal and asthmatic BSM. Relationships between deregulated miRNAs, mRNA expression, and the identity of active signaling pathways in asthmatic BSM will be examined by bioinformatic and functional studies. At the end of this work, we will have initiated a process to fill a marked knowledge void in the asthma field and will have established a foundation for a variety of future studies.