Martin Lab Research
Our studies aim to understand the molecular mechanisms that regulate vascular smooth muscle cell (SMC) phenotypic plasticity. Mature SMC retain the ability to de-differentiate and re-enter the cell cycle. This is essential for such processes as angiogenesis, but also contributes to the pathogenesis of atherosclerosis, intimal hyperplasia, and restenosis.
Regulation of Vascular Smooth Muscle Phenotype
Rapamycin-eluting stents have revolutionized treatment of coronary artery disease, dramatically reducing restenosis. While highly efficacious in this localized drug delivery setting, systemic high dose rapamycin is not a viable strategy for other vascular diseases due to adverse effects. Our goal is to understand the molecular mechanisms by which rapamycin beneficially affects SMC phenotype, in order to develop novel therapeutics. Identifying the smooth muscle-specific targets of the mTOR pathway may generate new strategies for treatment and prevention of atherosclerosis and intimal hyperplasia.
We have recently discovered that the mTOR pathway promotes VSMC differentiation through regulation of the DNA modifying enzyme TET2. We have identified TET2 as a novel master epigenetic regulator of VSMC phenotype. Notably, TET2 promotes changes in chromatin that lead to expression of prodifferentiation genes including SRF and myocardin and contractile genes such as SM-MHC and SM-alpha actin, while concomitantly downregulating expression of de-differentiation-associated genes including KLF4. TET2 also promotes more global chromatin remodeling as indicated by changes in histone marks.
We are working to understand how TET2 regulates SMC gene expression by genome-wide profiling of methylation and hydroxymethylation in concert with transcriptome profiling in SMC. We are also expanding our studies, identifying other epigenetic regulators and marks that influence SMC phenotype.
We have previously shown that rapamycin feedback signaling through Akt2 underlies its effects on VSMC phenotype in vitro. We are currently studying the effects of Akt isoforms in rapamycin therapeutic response in vivo and have uncovered exciting Akt isoform-specific effects that reveal opposing roles for these highly related kinases.
We are also studying Akt-regulated transcription factors and cyto skeletal-associated proteins that contribute to VSMC phenotypic modulation.