Project Summary Pulmonary hypertension (PH) is a devastating lung disease characterized by pulmonary vascular remodeling and associated with high morbidity and mortality. Discovery of new therapeutic targets in PH has been limited by the heterogeneity in disease endotypes and incomplete mechanistic insight into the cellular processes that control and perpetuate vascular remodeling. Recently, the mechanistic target of rapamycin (mTOR) signaling pathway has been implicated in the development and progression of PH, including pulmonary arterial hypertension (PAH). Despite the growing importance of mTOR activation in pulmonary diseases, the effects of mTOR hyperactivation on pulmonary cells and the contribution of mTOR to the development and progression of vascular remodeling remains incompletely understood. In my preliminary data, I demonstrate that mesenchymal cells will act as a signaling hub after selective deletion of tuberous sclerosis complex 2 (Tsc2) and subsequent mTOR activation in progenitor mesenchymal cells (Tbx4LME-CreTsc2Mesenchymal KO). These cells orchestrate dysregulated cellular responses in arterial endothelial cells (ECs), leading to pulmonary vascular remodeling and spontaneous PH in Tsc2M-KO mice. This proposal will expand on this finding and examine how mTOR activation in specific mesenchymal populations alters EC behavior, function and trajectory and how aberrant mTOR signaling contributes to pulmonary vascular remodeling. To accomplish this task, I will utilize three novel mouse models with mTOR activation in distinct mesenchymal populations. To understand the disease relevance of the murine models, I will be performing concurrent experiments on primary lung tissues from lymphangioleiomyomatosis (LAM) and PAH. LAM is a monogenic disease with mTORC1 activation in lung mesenchyme cells. In additional to parenchymal changes, a subset of patients with LAM develop pulmonary vascular remodeling and PH. As a monogenic disease, LAM is an ideal model for the study of mTOR activation on EC biology and pulmonary vascular remodeling. This proposal leverage my expertise in pulmonary vascular biology, ex vivo model systems and in vivo experience with transgenic murine lines to generate significant discoveries regarding the fate regulation and function of endothelial cells in pulmonary vascular remodeling. My training, composed of coursework/workshops in bioinformatics and epigenetics, will take place under the mentorship of Dr. Vera Krymskaya, a leader in mTOR research. To ensure that I am meeting research and academic milestones, I have compiled a diverse but complementary Advisory Committee. Upon completion of this work, I will develop additional comprehensive skills in epigenetic analysis and advanced bioinformatics, ex vivo lung modeling, and in vivo murine models. Together, the research and career development plans proposed herein will facilitate a better understanding of the cellular crosstalk in the pulmonary microenvironment whi...