Regulation of VSMC phenotype remains a key unanswered question in vascular smooth muscle cell (VSMC) biology. VSMC retain a remarkable plasticity to de-differentiate and re-enter the cell cycle allowing for growth and healing. However, such plasticity can also contribute to severe vascular pathologies, including restenosis, graft failure, atherosclerosis, and transplant vasculopathy. Remarkably, despite intense study, the process regulating plasticity is largely unknown with few therapies successfully targeting this process. With the growing numbers of patients suffering from vascular disease the discovery of novel targets is urgently warranted. While rapamycin analogs are efficacious drug-eluting stent agents, the risk of late-stent thrombosis and subsequent need for long term antiplatelet therapy still complicates their use. Our previous studies have revealed that the mTORC1 inhibitor, rapamycin, promotes VSMC differentiation, revealing cell type-specific transcription as a novel function of the mTORC1 pathway. Moreover, we implicated feedback activation of Akt2 as critical for rapamycin-induced differentiation. We have discovered distinct roles for Akt1 and Akt2 in the response to vascular injury. We have also identified TET2 and LMO7 as novel mTORC1-regulated proteins that modulate VSMC phenotype. Based upon these exciting Preliminary Results we will address the overall hypothesis that the mTORC1 pathway governs VSMC phenotype and response to injury through epigenetic (TET2) and transcriptional (LMO7) regulation, and that Akt isoforms play distinct roles in the pathology of restenosis and therapeutic response to rapamycin.
In Specific Aim 1, we will determine the role of TET2 in VSMC phenotypic modulation and how it is regulated by rapamycin.
In Specific Aim 2, we will determine the role of LMO7 in rapamycin- induced VSMC differentiation in vitro and in response to injury in vivo.
In Specific Aim 3, we will determine the differential roles of Akt1 and Akt2 in injury response in vascular tissues. If our goals are achieved, we will have identified key regulatory elements in VSMC plasticity. Understanding the critical mechanisms by which mTORC1 regulates VSMC phenotype will lead to improved cardiovascular therapeutics.
Excessive growth of vascular smooth muscle cells (VSMC) contributes to atherosclerosis and to failure of the procedures (angioplasty/stenting) that restore blood flow through atherosclerotic vessels. Delivering the drug rapamycin on stents during angioplasty very effectively prevents VSMC overgrowth. Our goal is to understand why VSMC grow excessively and how rapamycin regulates this process, in order to develop better and safer agents for prevention and therapy for other cardiovascular diseases, including atherosclerosis and transplant vasculopathy.
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