Hyperactive mTORC1 in Lung Mesenchyme Induces Endothelial Cell Dysfunction and Pulmonary Vascular Remodeling
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ABSTRACT: Lymphangioleiomyomatosis (LAM) is a progressive cystic lung disease caused by tuberous sclerosis complex 1/2 (TSC1/2) gene mutations resulting in activation of the mechanistic target of rapamycin complex 1 (mTORC1). A subset of LAM patients develops pulmonary vascular remodeling and pulmonary hypertension. To model LAM disease, we utilized an mTORC1 gain-of-function mouse model with a Tsc2 knock-out (Tsc2KO) specific to lung mesenchyme (Tbx4LME-CreTsc2fl/fl), similar to the mesenchyme specific genetic alterations seen in human disease. As early as 8 weeks of age, ECs from Tbx4LME-CreTsc2fl/fl mice exhibited marked transcriptomic changes despite absence of morphological changes to the distal lung microvasculature. In contrast, 1 year old Tbx4LME-CreTsc2fl/fl mice spontaneously developed pulmonary vascular remodeling with increased medial thickness. We subsequently performed single cell RNA-sequencing of 1 year old mouse lung and identified paracrine ligands originating from Tsc2KO mesenchyme impacting arterial endothelial cells. These cells contained transcriptionally altered genes including those in pathways associated with blood vessel remodeling, highlighting the pathogenic importance of the mesenchymal-endothelial cell axis.
Project description:Tumor suppressor Tuberous sclerosis complex 2 (TSC2) is a key negative regulator of mammalian target of rapamycin (mTOR), a central controller of cell growth and metabolism in health and disease. Loss of TSC2 induces the constitutive activation of mTORC1 in rare lung disease pulmonary Lymphangioleiomyomatosis (LAM), which affects only women of childbearing age and characterized by lung destruction and progressive loss of pulmonary function. Little is known how TSC2 loss induces LAM and what is the LAM cell of origin. To determine cell-type specific effects of TSC2 loss and mTORC1 activation on lung homeostasis we generated new transgenic mice with targeted Tsc2 deletion in lung mesenchyme Tbx4-Cre+Tsc2flox/flox and lung epithelium Shh-Cre+Tsc2flox/flox. Both Tbx4-Cre+, Tsc2flox/flox and Shh-Cre+, Tsc2flox/flox mice were viable and fertile. Adult Tbx4-Cre+Tsc2flox/flox mice demonstrated mTORC1 activation in lung mesenchyme, progressive alveolar enlargement, female-specific pulmonary function decline and prgenancy-induced lesion growth. To investigate molecular mechanism underlying observed phenotypic changes in the Tsc2KO lungs we performed comparative bulk-RNAseq analysis of the gene expression changes in the major cell subpopulations of the adult female 8-week-old Tsc2KO mouse lungs compared to the age- and sex-matched WT controls.
Project description:Lymphangioleiomyomatosis (LAM) is a rare, debilitating lung disease that predominantly affects women of reproductive age. LAM cells carry deleterious mutations of tuberous sclerosis complex (TSC1/TSC2) genes, resulting in hyperactivation of the mechanistic target of rapamycin complex 1 (mTORC1) and ultimately dysregulated cell growth. The integrative single cell omics data identified the activation of uterine specific HOX-PBX transcriptional programming in pulmonary LAMCORE cells. Network analysis predicted homeobox transcription factors including PBX1 and HOXD11 as key regulators controlling LAMCORE cell fate. Targeting the HOX-PBX network may have therapeutic value in LAM and TSC-related diseases, and possibly in other mTORC1-hyperactive neoplasms.
Project description:Lymphangioleiomyomatosis (LAM) is a rare, debilitating lung disease that predominantly affects women of reproductive age. LAM cells carry deleterious mutations of tuberous sclerosis complex (TSC1/TSC2) genes, resulting in hyperactivation of the mechanistic target of rapamycin complex 1 (mTORC1) and ultimately dysregulated cell growth. The integrative single cell omics data identified the activation of uterine specific HOX-PBX transcriptional programming in pulmonary LAMCORE cells. Network analysis predicted homeobox transcription factors including PBX1 and HOXD11 as key regulators controlling LAMCORE cell fate. Targeting the HOX-PBX network may have therapeutic value in LAM and TSC-related diseases, and possibly in other mTORC1-hyperactive neoplasms.
Project description:mTORC1 is inhibited by rapamycin or Torin1 in lymphangioleiomyomatosis (LAM) 621-101 (TSC2-deficient) cells, in which mTORC1 activity is elevated, and we compared these effects to inhibition of S6K and its target SRPK2.
Project description:<p>Lymphangioleiomyomatosis (LAM) is an uncommon, progressive, cystic lung disease that predominantly affects young women. It is believed to be caused by defects within cellular pathways that regulate nutrient uptake, cell size, cell migration, and cell proliferation. The disease is caused by mutations in tuberous sclerosis complex (TSC) genes. Individuals with Lymphangioleiomyomatosis (LAM) often experience pneumothorax and chylothorax, as well progressive loss of lung function. Lymphangioleiomyomatosis (LAM) is frequently fatal and existing therapies for the disease have not proven effective. Lung transplantation can be considered as a last option, but alternative treatments are needed. Sirolimus is an immunosuppressive drug that is often used in people who have had kidney transplants. It directly affects the genetic pathway that causes Lymphangioleiomyomatosis (LAM). This study will evaluate the safety and effectiveness of sirolimus in stabilizing or improving lung function in people with Lymphangioleiomyomatosis (LAM).</p> <p>Individuals interested in participating in this 2-year, double-blind study will first report to the study sites for pulmonary function testing to determine their eligibility for participation. Participants deemed eligible will be randomly assigned to receive either sirolimus or placebo for 1 year. Sirolimus or placebo will be administered in 2 tablet doses (2 mg for sirolimus) for the duration of the study. Study visits will occur at baseline, Week 3, every 3 months for 12 months, and Months 18 and 24. Study visits will include a physical exam, questionnaires, a pregnancy test, blood and urine collection, and functional lung tests. A 6-minute walk test will occur at most study visits; a chest x-ray will be taken at baseline and Month 24; and a volumetric computed tomography scan will occur at baseline Month 12, and Month 24. Adverse events, medication side effects, and lung function will be assessed at each visit.</p>
Project description:Transcriptome analysis of total RNA samples from human cell line (LAM 621-101, female) Global gene and splice isoform expression profiling was performed to get a comprehensive view of transcriptome changes in human Lymphangioleiomyomatosis (LAM 621-101, female) cell line after inhibition of mTORC1 and SRPK2 proteins.
Project description:Lymphangioleiomyomatosis (LAM) is a rare disease involving cystic lung destruction by invasive LAM cells. These cells harbor loss-of-function mutations in TSC2, conferring hyperactive mTORC1 signaling. Here, tissue engineering tools are employed to model LAM and identify new therapeutic candidates. Biomimetic hydrogel culture of LAM cells is found to recapitulate the molecular and phenotypic characteristics of human disease more faithfully than culture on plastic. A 3D drug screen is conducted, identifying histone deacetylase (HDAC) inhibitors as anti-invasive agents that are also selectively cytotoxic toward TSC2−/− cells. The anti-invasive effects of HDAC inhibitors are independent of genotype, while selective cell death is mTORC1-dependent and mediated by apoptosis. Genotype-selective cytotoxicity is seen exclusively in hydrogel culture due to potentiated differential mTORC1 signaling, a feature that is abrogated in cell culture on plastic. Importantly, HDAC inhibitors block invasion and selectively eradicate LAM cells in vivo in zebrafish xenografts. These findings demonstrate that tissue-engineered disease modeling exposes a physiologically relevant therapeutic vulnerability that would be otherwise missed by conventional culture on plastic. This work substantiates HDAC inhibitors as possible therapeutic candidates for the treatment of patients with LAM and requires further study.
Project description:Pulmonary Lymphangioleiomyomatosis (LAM), a rare lung disease that affects predominantly women, is characterized by proliferation of smooth muscle-like cells in the lungs, destruction of lung tissue, upregulation of VEGF-D, and growth of lymphatic vessels inducing a loss of pulmonary function. TSC2 gene mutations that render TSC2 inactive are a common finding associated with LAM. To better understand the function of the TSC2 gene in LAM , we sought to characterize differences in the transcriptome of cells where TSC2 is inactivated. RNA-Seq was used to measure transcript expression differences between a human TSC2-null angiolipoma cell line derived from an individual with LAM, and the same cell line with re-expressed TSC2 to serve as a control. The Illumina TruSeq method was used to prepare poly(A)-selected stranded RNA-Seq libraries, and 100bp paired-end reads were generated with an Illumina Hi-Seq 2500 instrument in high output mode. RNA-Seq data was analyzed using kallisto (http://pachterlab.github.io/kallisto/) and R.
Project description:Lymphangioleiomyomatosis (LAM) is a metastasizing neoplasm of reproductive age women which causes cystic lung remodeling and progressive respiratory failure. While LAM lesions are known to contain abnormal smooth muscle-like cells which harbor mTOR activating mutations in TSC1 or TSC2, the tissue origins of the mutant “LAM cells” that invade the lung remain unclear. By employing single cell and single nuclear RNA sequencing on explanted LAM lungs, we identified a unique population of cells and associated signature genes and gene networks which were readily distinguished from those of endogenous lung cells. These unique LAMCORE cells shared closest transcriptomic similarity to normal uterus and share transcriptomic features with neural crest, as identified in uterine LAM lesions by single nuclear RNA-seq. Immunofluorescence microscopy demonstrated the expression of LAMCORE cell signature genes within LAM lesions in both lung and uterus. Serum aptamer proteomics and ELISA identified biomarkers consistent with the signature genes expressed and predicted to be secreted by LAMCORE cells. Single cell transcriptomics strongly supports a uterine neural crest origin of LAMCORE cells; providing insights into disease pathogenesis and informing future treatment strategies for LAM.